Publications by authors named "Deepak Gaur"

47 Publications

RTS,S/AS01 malaria vaccine induces IgA responses against CSP and vaccine-unrelated antigens in African children in the phase 3 trial.

Vaccine 2021 01 25;39(4):687-698. Epub 2020 Dec 25.

ISGlobal, Hospital Clínic, Universitat de Barcelona, Carrer Rosselló 153 CEK Building, E-08036 Barcelona, Catalonia, Spain; Centro de Investigação em Saúde de Manhiça (CISM), Rua 12, Cambeve, Vila de Manhiça, CP 1929 Maputo, Mozambique. Electronic address:

Background: The evaluation of immune responses to RTS,S/AS01 has traditionally focused on immunoglobulin (Ig) G antibodies that are only moderately associated with protection. The role of other antibody isotypes that could also contribute to vaccine efficacy remains unclear. Here we investigated whether RTS,S/AS01 elicits antigen-specific serum IgA antibodies to the vaccine and other malaria antigens, and we explored their association with protection.

Methods: Ninety-five children (age 5-17 months old at first vaccination) from the RTS,S/AS01 phase 3 clinical trial who received 3 doses of RTS,S/AS01 or a comparator vaccine were selected for IgA quantification 1 month post primary immunization. Two sites with different malaria transmission intensities (MTI) and clinical malaria cases and controls, were included. Measurements of IgA against different constructs of the circumsporozoite protein (CSP) vaccine antigen and 16 vaccine-unrelated Plasmodium falciparum antigens were performed using a quantitative suspension array assay.

Results: RTS,S vaccination induced a 1.2 to 2-fold increase in levels of serum/plasma IgA antibodies to all CSP constructs, which was not observed upon immunization with a comparator vaccine. The IgA response against 13 out of 16 vaccine-unrelated P. falciparum antigens also increased after vaccination, and levels were higher in recipients of RTS,S than in comparators. IgA levels to malaria antigens before vaccination were more elevated in the high MTI than the low MTI site. No statistically significant association of IgA with protection was found in exploratory analyses.

Conclusions: RTS,S/AS01 induces IgA responses in peripheral blood against CSP vaccine antigens and other P. falciparum vaccine-unrelated antigens, similar to what we previously showed for IgG responses. Collectively, data warrant further investigation of the potential contribution of vaccine-induced IgA responses to efficacy and any possible interplay, either synergistic or antagonistic, with protective IgG, as identifying mediators of protection by RTS,S/AS01 immunization is necessary for the design of improved second-generation vaccines.

Clinical Trial Registration: ClinicalTrials.gov: NCT008666191.
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http://dx.doi.org/10.1016/j.vaccine.2020.12.038DOI Listing
January 2021

Antibody combinations targeting the essential antigens CyRPA, RH5 and MSP-119 potently neutralize Plasmodium falciparum clinical isolates from India and Africa.

J Infect Dis 2020 Sep 29. Epub 2020 Sep 29.

Laboratory of Malaria & Vaccine Research, School of Biotechnology, Jawaharlal Nehru University, New Delhi, India.

Background: Targeting multiple key antigens that mediate distinct P. falciparum erythrocyte invasion pathways is an attractive approach for the development of blood-stage malaria vaccines. However, the challenge is to identify antigen cocktails that elicit potent strain-transcending parasite-neutralizing antibodies efficacious at low IgG concentrations feasible to achieve through vaccination. Previous reports have screened inhibitory antibodies primarily against well-adapted laboratory parasite clones. However, validation of the parasite-neutralizing efficacy against clinical isolates with minimal in vitro cultivation is equally significant to better ascertain their prospective in vivo potency.

Method: We evaluated the parasite-neutralizing activity of different antibodies individually and in combinations against laboratory adapted clones and clinical isolates. Clinical isolates were collected from central India and Mozambique (Africa), characterized for their invasion properties and genetic diversity of invasion ligands.

Results: In our portfolio, we evaluated 25 triple antibody combinations and identified the MSP-Fu+CyRPA+RH5 antibody combination to elicit maximal parasite neutralization against P. falciparum clinical isolates with variable properties that underwent minimal in vitro cultivation.

Conclusion: The MSP-Fu+CyRPA+RH5 combination exhibited highly robust parasite-neutralization against P. falciparum clones and clinical-isolates, thus substantiating them as promising candidate antigens and establishing a proof of principle for the development of a combinatorial P. falciparum blood-stage malaria vaccine.
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http://dx.doi.org/10.1093/infdis/jiaa608DOI Listing
September 2020

Lead Intraocular Foreign Body Injury Following Ejection.

Aerosp Med Hum Perform 2020 Aug;91(8):674-678

Ejection injuries involving the eyes have become uncommon due to effective protection by helmets and visors. We report a unique case of intraocular lead foreign body injury occurring after ejection from a Hawk aircraft in a pilot who had his helmet and visor on. A 40-yr-old male pilot sustained facial injuries after ejection from a Hawk aircraft. He had multiple foreign bodies embedded in the skin around his jaw, corneal foreign bodies, and self-sealed corneal and lens entry in left eye, with one foreign body lodged within the lens and two in the vitreous behind the lens. The foreign bodies showed low reflectivity on CT scan suggestive of plastic. However, spectroscopic and electron microscopic analysis of pieces removed from the cornea confirmed the material to be predominantly lead, which came from the miniature detonator cord (MDC). An electroretinogram (ERG) showed reduction of scotopic b wave amplitude in the affected eye. The pilot underwent intravitreal foreign body removal successfully through pars plana vitrectomy. Post-removal vision recovered from 20/60 to 20/20 with ERG also showing recovery of scotopic b wave amplitude from 100 μV to 180 μV Though systemic toxicity due to high blood levels of lead are well known, this case is unique in demonstrating direct retinal toxicity because of intravitreal lead foreign body. It also raises aeromedical concerns about the hazards of MDC splatter despite full protection with helmet and visor.
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August 2020

Bliss' and Loewe's additive and synergistic effects in Plasmodium falciparum growth inhibition by AMA1-RON2L, RH5, RIPR and CyRPA antibody combinations.

Sci Rep 2020 07 16;10(1):11802. Epub 2020 Jul 16.

Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 12735 Twinbrook Parkway, Rockville, MD, 20852, USA.

Plasmodium invasion of red blood cells involves malaria proteins, such as reticulocyte-binding protein homolog 5 (RH5), RH5 interacting protein (RIPR), cysteine-rich protective antigen (CyRPA), apical membrane antigen 1 (AMA1) and rhoptry neck protein 2 (RON2), all of which are blood-stage malaria vaccine candidates. So far, vaccines containing AMA1 alone have been unsuccessful in clinical trials. However, immunization with AMA1 bound with RON2L (AMA1-RON2L) induces better protection against P. falciparum malaria in Aotus monkeys. We therefore sought to determine whether combinations of RH5, RIPR, CyRPA and AMA1-RON2L antibodies improve their biological activities and sought to develop a robust method for determination of synergy or additivity in antibody combinations. Rabbit antibodies against AMA1-RON2L, RH5, RIPR or CyRPA were tested either alone or in combinations in P. falciparum growth inhibition assay to determine Bliss' and Loewe's additivities. The AMA1-RON2L/RH5 combination consistently demonstrated an additive effect while the CyRPA/RIPR combination showed a modest synergistic effect with Hewlett's [Formula: see text] Additionally, we provide a publicly-available, online tool to aid researchers in analyzing and planning their own synergy experiments. This study supports future blood-stage vaccine development by providing a solid methodology to evaluate additive and/or synergistic (or antagonistic) effect of vaccine-induced antibodies.
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http://dx.doi.org/10.1038/s41598-020-67877-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7366652PMC
July 2020

Complement Evasion Strategies of Human Pathogenic Bacteria.

Indian J Microbiol 2020 Sep 24;60(3):283-296. Epub 2020 Apr 24.

Laboratory of Malaria and Vaccine Research, School of Biotechnology, Jawaharlal Nehru University, New Mehrauli Road, New Delhi, 110067 India.

Human pathogens need to overcome an elaborate network of host defense mechanisms in order to establish their infection, colonization, proliferation and eventual dissemination. The interaction of pathogens with different effector molecules of the immune system results in their neutralization and elimination from the host. The complement system is one such integral component of innate immunity that is critically involved in the early recognition and elimination of the pathogen. Hence, under this immune pressure, all virulent pathogens capable of inducing active infections have evolved immune evasive strategies that primarily target the complement system, which plays an essential and central role for host defense. Recent reports on several bacterial pathogens have elucidated the molecular mechanisms underlying complement evasion, inhibition of opsonic phagocytosis and cell lysis. This review aims to comprehensively summarize the recent findings on the various strategies adopted by pathogenic bacteria to escape complement-mediated clearance.
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http://dx.doi.org/10.1007/s12088-020-00872-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7329968PMC
September 2020

Antibody responses to the RTS,S/AS01 vaccine and antigens after a booster dose within the phase 3 trial in Mozambique.

NPJ Vaccines 2020 4;5:46. Epub 2020 Jun 4.

ISGlobal, Hospital Clínic-Universitat de Barcelona, Barcelona, Catalonia Spain.

The RTS,S/AS01 vaccine has shown consistent but partial vaccine efficacy in a pediatric phase 3 clinical trial using a 3-dose immunization schedule. A fourth-dose 18 months after the primary vaccination was shown to restore the waning efficacy. However, only total IgG against the immunodominant malaria vaccine epitope has been analyzed following the booster. To better characterize the magnitude, nature, and longevity of the immune response to the booster, we measured levels of total IgM, IgG, and IgG subclasses against three constructs of the circumsporozoite protein (CSP) and the hepatitis B surface antigen (HBsAg, also present in RTS,S) by quantitative suspension array technology in 50 subjects in the phase 3 trial in Manhiça, Mozambique. To explore the impact of vaccination on naturally acquired immune responses, we measured antibodies to antigens not included in RTS,S. We found increased IgG, IgG1, IgG3 and IgG4, but not IgG2 nor IgM, levels against vaccine antigens 1 month after the fourth dose. Overall, antibody responses to the booster dose were lower than the initial peak response to primary immunization and children had higher IgG and IgG1 levels than infants. Higher anti-Rh5 IgG and IgG levels were detected after the booster dose, suggesting that RTS,S partial protection could increase some blood stage antibody responses. Our work shows that the response to the RTS,S/AS01 booster dose is different from the primary vaccine immune response and highlights the dynamic changes in subclass antibody patterns upon the vaccine booster and with acquisition of adaptive immunity to malaria.
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http://dx.doi.org/10.1038/s41541-020-0192-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7272643PMC
June 2020

Poly-γ-D-Glutamate Capsule Inhibits Opsonic Phagocytosis by Impeding Complement Activation.

Front Immunol 2020 31;11:462. Epub 2020 Mar 31.

Laboratory of Malaria and Vaccine Research, School of Biotechnology, Jawaharlal Nehru University, New Delhi, India.

poly-γ-D-glutamic acid (PGA) capsule is an essential virulent factor that helps the bacterial pathogen to escape host immunity. Like other encapsulated bacterial species, the capsule may also inhibit complement-mediated clearance and ensure bacterial survival in the host. Previous reports suggest that spore proteins inhibit complement activation. However, the mechanism through which the capsule imparts a survival advantage to the active bacteria has not been demonstrated till date. Thus, to evaluate the role of the PGA capsule in evading host immunity, we have undertaken the present head-to-head comparative study of the phagocytosis and complement activation of non-encapsulated and encapsulated strains. The encapsulated virulent strain exhibited resistance toward complement-dependent and complement-independent bacterial phagocytosis by human macrophages. The non-encapsulated Sterne strain was highly susceptible to phagocytosis by THP-1 macrophages, after incubation with normal human serum (NHS), heat-inactivated serum, and serum-free media, thus indicating that the capsule inhibited both complement-dependent and complement-independent opsonic phagocytosis. An increased binding of C3b and its subsequent activation to C3c and C3dg, which functionally act as potent opsonins, were observed with the non-encapsulated Sterne strain compared with the encapsulated strain. Other known mediators of complement fixation, IgG, C-reactive protein (CRP), and serum amyloid P component (SAP), also bound more prominently with the non-encapsulated Sterne strain. Studies with complement pathway-specific, component-deficient serum demonstrated that the classical pathway was primarily involved in mediating C3b binding on the non-encapsulated bacteria. Both strains equally bound the complement regulatory proteins C4BP and factor H. Importantly, we demonstrated that the negative charge of the PGA capsule was responsible for the differential binding of the complement proteins between the non-encapsulated and encapsulated strains. At lower pH closer to the isoelectric point of PGA, the neutralization of the negative charge was associated with an increased binding of C3b and IgG with the encapsulated strain. Overall, our data have demonstrated that the capsule inhibits complement fixation and opsonization resulting in reduced phagocytosis by macrophages, thus allowing the bacterial pathogen to evade host immunity.
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http://dx.doi.org/10.3389/fimmu.2020.00462DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7138205PMC
March 2021

RTS,S/AS01E immunization increases antibody responses to vaccine-unrelated Plasmodium falciparum antigens associated with protection against clinical malaria in African children: a case-control study.

BMC Med 2019 08 14;17(1):157. Epub 2019 Aug 14.

ISGlobal, Hospital Clínic - Universitat de Barcelona, Carrer Rosselló 153, E-08036, Barcelona, Catalonia, Spain.

Background: Vaccination and naturally acquired immunity against microbial pathogens may have complex interactions that influence disease outcomes. To date, only vaccine-specific immune responses have routinely been investigated in malaria vaccine trials conducted in endemic areas. We hypothesized that RTS,S/A01E immunization affects acquisition of antibodies to Plasmodium falciparum antigens not included in the vaccine and that such responses have an impact on overall malaria protective immunity.

Methods: We evaluated IgM and IgG responses to 38 P. falciparum proteins putatively involved in naturally acquired immunity to malaria in 195 young children participating in a case-control study nested within the African phase 3 clinical trial of RTS,S/AS01E (MAL055 NCT00866619) in two sites of different transmission intensity (Kintampo high and Manhiça moderate/low). We measured antibody levels by quantitative suspension array technology and applied regression models, multimarker analysis, and machine learning techniques to analyze factors affecting their levels and correlates of protection.

Results: RTS,S/AS01E immunization decreased antibody responses to parasite antigens considered as markers of exposure (MSP1, AMA1) and levels correlated with risk of clinical malaria over 1-year follow-up. In addition, we show for the first time that RTS,S vaccination increased IgG levels to a specific group of pre-erythrocytic and blood-stage antigens (MSP5, MSP1 block 2, RH4.2, EBA140, and SSP2/TRAP) which levels correlated with protection against clinical malaria (odds ratio [95% confidence interval] 0.53 [0.3-0.93], p = 0.03, for MSP1; 0.52 [0.26-0.98], p = 0.05, for SSP2) in multivariable logistic regression analyses.

Conclusions: Increased antibody responses to specific P. falciparum antigens in subjects immunized with this partially efficacious vaccine upon natural infection may contribute to overall protective immunity against malaria. Inclusion of such antigens in multivalent constructs could result in more efficacious second-generation multistage vaccines.
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http://dx.doi.org/10.1186/s12916-019-1378-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6693200PMC
August 2019

Differential Patterns of IgG Subclass Responses to Antigens in Relation to Malaria Protection and RTS,S Vaccination.

Front Immunol 2019 15;10:439. Epub 2019 Mar 15.

ISGlobal, Hospital Clínic - Universitat de Barcelona, Barcelona, Spain.

Naturally acquired immunity (NAI) to malaria is mainly mediated by IgG antibodies but the subclasses, epitope targets and effector functions have not been unequivocally defined. Dissecting the type and specificity of antibody responses mediating NAI is a key step toward developing more effective vaccines to control the disease. We investigated the role of IgG subclasses to malaria antigens in protection against disease and the factors that affect their levels, including vaccination with RTS,S/AS01E. We analyzed plasma and serum samples at baseline and 1 month after primary vaccination with RTS,S or comparator in African children and infants participating in a phase 3 trial in two sites of different malaria transmission intensity: Kintampo in Ghana and Manhiça in Mozambique. We used quantitative suspension array technology (qSAT) to measure IgG responses to 35 pre-erythrocytic and blood stage antigens. Our results show that the pattern of IgG response is predominantly IgG1 or IgG3, with lower levels of IgG2 and IgG4. Age, site and RTS,S vaccination significantly affected antibody subclass levels to different antigens and susceptibility to clinical malaria. Univariable and multivariable analysis showed associations with protection mainly for cytophilic IgG3 levels to selected antigens, followed by IgG1 levels and, unexpectedly, also with IgG4 levels, mainly to antigens that increased upon RTS,S vaccination such as MSP5 and MSP1 block 2, among others. In contrast, IgG2 was associated with malaria risk. Stratified analysis in RTS,S vaccinees pointed to novel associations of IgG4 responses with immunity mainly involving pre-erythrocytic antigens upon RTS,S vaccination. Multi-marker analysis revealed a significant contribution of IgG3 responses to malaria protection and IgG2 responses to malaria risk. We propose that the pattern of cytophilic and non-cytophilic IgG antibodies is antigen-dependent and more complex than initially thought, and that mechanisms of both types of subclasses could be involved in protection. Our data also suggests that RTS,S efficacy is significantly affected by NAI, and indicates that RTS,S vaccination significantly alters NAI.
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http://dx.doi.org/10.3389/fimmu.2019.00439DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6428712PMC
August 2020

Analysis of factors affecting the variability of a quantitative suspension bead array assay measuring IgG to multiple Plasmodium antigens.

PLoS One 2018 2;13(7):e0199278. Epub 2018 Jul 2.

ISGlobal, Hospital Clínic-Universitat de Barcelona, Barcelona, Catalonia, Spain.

Reducing variability of quantitative suspension array assays is key for multi-center and large sero-epidemiological studies. To maximize precision and robustness of an in-house IgG multiplex assay, we analyzed the effect of several conditions on variability to find the best combination. The following assay conditions were studied through a fractional factorial design: antigen-bead coupling (stock vs. several), sample predilution (stock vs. daily), temperature of incubation of sample with antigen-bead (22°C vs. 37°C), plate washing (manual vs. automatic) and operator expertise (expert vs. apprentice). IgG levels against seven P. falciparum antigens with heterogeneous immunogenicities were measured in test samples, in a positive control and in blanks. We assessed the variability and MFI quantification range associated to each combination of conditions, and their interactions, and evaluated the minimum number of samples and blank replicates to achieve good replicability. Results showed that antigen immunogenicity and sample seroreactivity defined the optimal dilution to assess the effect of assay conditions on variability. We found that a unique antigen-bead coupling, samples prediluted daily, incubation at 22°C, and automatic washing, had lower variability. However, variability increased when performing several couplings and incubating at 22°C vs. 37°C. In addition, no effect of temperature was seen with a unique coupling. The expertise of the operator had no effect on assay variability but reduced the MFI quantification range. Finally, differences between sample replicates were minimal, and two blanks were sufficient to capture assay variability, as suggested by the constant Intraclass Correlation Coefficient of three and two blanks. To conclude, a single coupling was the variable that most consistently reduced assay variability, being clearly advisable. In addition, we suggest having more sample dilutions instead of replicates to increase the likelihood of sample MFIs falling in the linear part of the antigen-specific curve, thus increasing precision.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0199278PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6028107PMC
December 2018

Optimization of incubation conditions of Plasmodium falciparum antibody multiplex assays to measure IgG, IgG, IgM and IgE using standard and customized reference pools for sero-epidemiological and vaccine studies.

Malar J 2018 Jun 1;17(1):219. Epub 2018 Jun 1.

ISGlobal, Hospital Clínic-Universitat de Barcelona, Carrer Rosselló 153 (CEK Building), 08036, Barcelona, Catalonia, Spain.

Background: The quantitative suspension array technology (qSAT) is a useful platform for malaria immune marker discovery. However, a major challenge for large sero-epidemiological and malaria vaccine studies is the comparability across laboratories, which requires the access to standardized control reagents for assay optimization, to monitor performance and improve reproducibility. Here, the Plasmodium falciparum antibody reactivities of the newly available WHO reference reagent for anti-malaria human plasma (10/198) and of additional customized positive controls were examined with seven in-house qSAT multiplex assays measuring IgG, IgG subclasses, IgM and IgE against a panel of 40 antigens. The different positive controls were tested at different incubation times and temperatures (4 °C overnight, 37 °C 2 h, room temperature 1 h) to select the optimal conditions.

Results: Overall, the WHO reference reagent had low IgG2, IgG4, IgM and IgE, and also low anti-CSP antibody levels, thus this reagent was enriched with plasmas from RTS,S-vaccinated volunteers to be used as standard for CSP-based vaccine studies. For the IgM assay, another customized plasma pool prepared with samples from malaria primo-infected adults with adequate IgM levels proved to be more adequate as a positive control. The range and magnitude of IgG and IgG responses were highest when the WHO reference reagent was incubated with antigen-coupled beads at 4 °C overnight. IgG levels measured in the negative control did not vary between incubations at 37 °C 2 h and 4 °C overnight, indicating no difference in unspecific binding.

Conclusions: With this study, the immunogenicity profile of the WHO reference reagent, including seven immunoglobulin isotypes and subclasses, and more P. falciparum antigens, also those included in the leading RTS,S malaria vaccine, was better characterized. Overall, incubation of samples at 4 °C overnight rendered the best performance for antibody measurements against the antigens tested. Although the WHO reference reagent performed well to measure IgG to the majority of the common P. falciparum blood stage antigens tested, customized pools may need to be used as positive controls depending on the antigens (e.g. pre-erythrocytic proteins of low natural immunogenicity) and isotypes/subclasses (e.g. IgM) under study.
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http://dx.doi.org/10.1186/s12936-018-2369-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5984756PMC
June 2018

Human APOBEC3B interacts with the heterogenous nuclear ribonucleoprotein A3 in cancer cells.

J Cell Biochem 2018 08 25;119(8):6695-6703. Epub 2018 Apr 25.

Faculty of Life Sciences and Biotechnology, South Asian University, New Delhi, India.

Human APOBEC3B (A3B), like other APOBEC3 members, is a cytosine deaminase which causes hypermutation of single stranded genome. Recent studies have shown that A3B is predominantly elevated in multiple cancer tissues and cell lines such as the bladder, cervix, lung, head and neck, and breast. Upregulation and activation of A3B in developing tumors can cause an unexpected cluster of mutations which promote cancer development and progression. The cellular proteins which facilitate A3B function through direct or indirect interactions remain largely unknown. In this study, we performed LC-MS-based proteomics to identify cellular proteins which coimmunoprecipitated with A3B. Our results indicated a specific interaction of A3B with hnRNP A3 (heterogeneous nuclear ribonucleoprotein). This interaction was verified by co-immunoprecipitation and was found to be RNA-dependent. Furthermore, A3B and hnRNP A3 colocalized as evident from immunofluorescence analysis.
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http://dx.doi.org/10.1002/jcb.26855DOI Listing
August 2018

Identifying Immune Correlates of Protection Against Plasmodium falciparum Through a Novel Approach to Account for Heterogeneity in Malaria Exposure.

Clin Infect Dis 2018 02;66(4):586-593

ISGlobal, Barcelona Ctr. Int. Health Res. (CRESIB), Hospital Clínic - Universitat de Barcelona, Spain.

Background: A main criterion to identify malaria vaccine candidates is the proof that acquired immunity against them is associated with protection from disease. The age of the studied individuals, heterogeneous malaria exposure, and assumption of the maintenance of a baseline immune response can confound these associations.

Methods: Immunoglobulin G/immunoglobulin M (IgG/ IgM) levels were measured by Luminex® in Mozambican children monitored for clinical malaria from birth until 3 years of age, together with functional antibodies. Studied candidates were pre-erythrocytic and erythrocytic antigens, including EBAs/PfRhs, MSPs, DBLs, and novel antigens merely or not previously studied in malaria-exposed populations. Cox regression models were estimated at 9 and 24 months of age, accounting for heterogeneous malaria exposure or limiting follow-up according to the antibody's decay.

Results: Associations of antibody responses with higher clinical malaria risk were avoided when accounting for heterogeneous malaria exposure or when limiting the follow-up time in the analyses. Associations with reduced risk of clinical malaria were found only at 24 months old, but not younger children, for IgG breadth and levels of IgG targeting EBA140III-V, CyRPA, DBL5ε and DBL3x, together with C1q-fixation activity by antibodies targeting MSP119.

Conclusions: Malaria protection correlates were identified, only in children aged 24 months old when accounting for heterogeneous malaria exposure. These results highlight the relevance of considering age and malaria exposure, as well as the importance of not assuming the maintenance of a baseline immune response throughout the follow-up. Results may be misleading if these factors are not considered.
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http://dx.doi.org/10.1093/cid/cix837DOI Listing
February 2018

Aeromedical solutions for aerospace safety.

Med J Armed Forces India 2017 Oct 15;73(4):384-387. Epub 2017 Nov 15.

PDMS (Spl), Air HQ, RK Puram, New Delhi 110066, India.

All facets of activity in the speciality of Aviation Medicine are essentially aimed at enhancing aerospace safety. This paper highlights some innovative changes brought about by Aerospace Medicine in the three major fields of the speciality namely, medical evaluation, aeromedical training and research. Based on lab and field studies, military aircrew are now permitted flying with Modifinil as 'Go' Pill and Zolpidem as 'No-Go' Pill during sustained operations. Several other drugs for disabilities like Hypertension and CAD are now permitted for aviators. Comprehensive revision of policy permitting early return to flying is an on-going process. OPRAM courses for all three streams of aircrew in IAF have contributed to reduce aircraft accident rates. Human Engineering Consultancy and expert advice is provided by specialists at IAM as well as those in the field. In future, the country needs to provide better post-service opportunities to aerospace medicine specialists. This, in turn, will attract bright young minds to the specialty. The ISRO Humanin-Space programme will be an exciting challenge for all in this unique field. Aerospace Medicine continues to provide aerospace safety solutions to the IAF and the aviation industry. The nation needs to continue to utilize and support this specialty.
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http://dx.doi.org/10.1016/j.mjafi.2017.09.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5771699PMC
October 2017

Prevalence of afebrile parasitaemia due to & in district Balaghat (Madhya Pradesh): Implication for malaria control.

Indian J Med Res 2017 Aug;146(2):260-266

National Institute for Research in Tribal Health, Jabalpur, India.

Background & Objectives: Balaghat district in Central India is a highly malarious district where both Plasmodium falciparum and P. vivax are prevalent. In this district, the persistence of malaria was on an increase and not responsive to intervention measures even though there was no drug resistance. This study was undertaken by conducting mass screening to determine the prevalence of malaria among particularly vulnerable tribe of Balaghat, for developing evidence-based intervention measures for malaria control in hard to reach areas.

Methods: This prospective study was carried out during 2013-2014 by conducting mass survey of the population in 10 villages of Birsa community health centre (CHC) and 12 villages of Baihar CHC. Finger-pricked blood smears were collected from all consenting individuals with or without fever for microscopic examination.

Results: In the febrile group, the slide positivity rate (SPR) and slide falciparum rate (SFR) were 32.4 and 28.9 per cent, respectively, with 89.4 per cent P. falciparum, while in the afebrile individuals also, the SPR and SFR were high (29 and 26%, respectively), but these were significantly lower than that of febrile group. The gametocyte carriers were significantly higher (odds ratio 1.67, 95% confidence interval 1.25-2.25, P=0.0004) in afebrile patients when compared with febrile group. Vector incrimination showed the presence of four sporozoite-positive Anopheles culicifacies out of 1953 assayed.

Interpretation & Conclusions: Plasmodium falciparum malaria was high in young children (up to 8 years) as compared to the adult in both afebrile and febrile group in Balaghat district. High prevalence of gametocyte was observed in all age groups among the afebrile cases. The identification of afebrile malaria parasitaemia is an important challenge for the malaria elimination initiatives. A strong malaria surveillance system is fundamental to both programme design and implementation.
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http://dx.doi.org/10.4103/ijmr.IJMR_1538_16DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5761037PMC
August 2017

Role of Chromatin assembly factor 1 in DNA replication of Plasmodium falciparum.

Biochem Biophys Res Commun 2018 01 26;495(1):1285-1291. Epub 2017 Nov 26.

Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi, India. Electronic address:

Nucleosome assembly in P. falciparum could be the key process in maintaining its genomic integrity as DNA replicates more than once per cell cycle during several stages of its life cycle. Here, we report the functional characterization of P. falciparum chromatin assembly factor 1 (CAF1), which interacts with several proteins namely PfCAF2, Histones, PfHP1 and others. Consistent with the above findings, we demonstrate the presence of PfCAF1 at the telomeric repeat regions, central and subtelomeric var genes of multiple var gene family along with PfHP1. Further, we report the upregulation of PfCAF1 after treatment with genotoxic agents like MMS and HU. Together, these findings establish role of PfCAF1 in heterochromatin maintenance and as histone chaperone in nucleosome assembly and DNA damage repair.
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http://dx.doi.org/10.1016/j.bbrc.2017.11.131DOI Listing
January 2018

Assessment of the Combined Effect of Epstein-Barr Virus and Infections on Endemic Burkitt Lymphoma Using a Multiplex Serological Approach.

Front Immunol 2017 26;8:1284. Epub 2017 Oct 26.

ISGlobal, Barcelona Centre for International Health Research (CRESIB), Hospital Clínic, Universitat de Barcelona, Barcelona, Spain.

Epstein-Barr virus (EBV) is a necessary cause of endemic Burkitt lymphoma (eBL), while the role of in eBL remains uncertain. This study aimed to generate new hypotheses on the interplay between both infections in the development of eBL by investigating the IgG and IgM profiles against several EBV and antigens. Serum samples collected in a childhood study in Malawi (2005-2006) from 442 HIV-seronegative children (271 eBL cases and 171 controls) between 1.4 and 15 years old were tested by quantitative suspension array technology against a newly developed multiplex panel combining 4 EBV antigens [Z Epstein-Barr replication activator protein (ZEBRA), early antigen-diffuse component (EA-D), EBV nuclear antigen 1, and viral capsid antigen p18 subunit (VCA-p18)] and 15 antigens selected for their immunogenicity, role in malaria pathogenesis, and presence in different parasite stages. Principal component analyses, multivariate logistic models, and elastic-net regressions were used. As expected, elevated levels of EBV IgG (especially against the lytic antigens ZEBRA, EA-D, and VCA-p18) were strongly associated with eBL [high vs low tertile odds ratio (OR) = 8.67, 95% confidence interval (CI) = 4.81-15.64]. Higher IgG responses to the merozoite surface protein 3 were observed in children with eBL compared with controls (OR = 1.29, 95% CI = 1.02-1.64), showing an additive interaction with EBV IgGs (OR = 10.6, 95% CI = 5.1-22.2,  = 0.05). Using elastic-net regression models, eBL serological profile was further characterized by lower IgM levels against preerythrocytic-stage antigen CelTOS and EBV lytic antigen VCA-p18 compared with controls. In a secondary analysis, abdominal Burkitt lymphoma had lower IgM to EBV and higher IgG to EA-D levels than cases with head involvement. Overall, this exploratory study confirmed the strong role of EBV in eBL and identified differential IgG and IgM patterns to erythrocytic vs preerythrocytic antigens that suggest a more persistent/chronic malaria exposure and a weaker IgM immune response in children with eBL compared with controls. Future studies should continue exploring how the malaria infection status and the immune response to interact with EBV infection in the development of eBL.
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http://dx.doi.org/10.3389/fimmu.2017.01284DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5662586PMC
October 2017

Host age and expression of genes involved in red blood cell invasion in Plasmodium falciparum field isolates.

Sci Rep 2017 07 5;7(1):4717. Epub 2017 Jul 5.

ISGlobal, Barcelona Ctr. Int. Health Res. (CRESIB), Hospital Clínic - Universitat de Barcelona, Barcelona, Spain.

Plasmodium falciparum proteins involved in erythrocyte invasion are main targets of acquired immunity and important vaccine candidates. We hypothesized that anti-parasite immunity acquired upon exposure would limit invasion-related gene (IRG) expression and affect the clinical impact of the infection. 11 IRG transcript levels were measured in P. falciparum isolates by RT-PCR, and IgG/IgM against invasion ligands by Luminex®, in 50 Mozambican adults, 25 children with severe malaria (SM) and 25 with uncomplicated malaria (UM). IRG expression differences among groups and associations between IRG expression and clinical/immunologic parameters were assessed. IRG expression diversity was higher in parasites infecting children than adults (p = 0.022). eba140 and ptramp expression decreased with age (p = 0.003 and 0.007, respectively) whereas p41 expression increased (p = 0.022). pfrh5 reduction in expression was abrupt early in life. Parasite density decreased with increasing pfrh5 expression (p < 0.001) and, only in children, parasite density increased with p41 expression (p = 0.007), and decreased with eba175 (p = 0.013). Antibody responses and IRG expression were not associated. In conclusion, IRG expression is associated with age and parasite density, but not with specific antibody responses in the acute phase of infection. Our results confirm the importance of multi-antigen vaccines development to avoid parasite immune escape when tested in malaria-exposed individuals.
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http://dx.doi.org/10.1038/s41598-017-05025-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5498679PMC
July 2017

Molecular characterization of internal transcribed spacer 1 (ITS 1) region of different isolates of India.

J Parasit Dis 2017 Jun 29;41(2):527-533. Epub 2016 Sep 29.

ICAR-National Research Centre on Equines, Sirsa Road, Hisar, Haryana 125001 India.

Six isolates collected from ponies (PH1 and PK6), camel (CB2), donkeys (DJ3 and DH4) and cattle (CK5) from Haryana, Rajasthan, Uttar Pradesh and Gujarat states of India were used for molecular characterization of internal transcribed spacer 1 (ITS 1). The DNA was isolated from purified trypanosomes of these six isolates after propagation in mice model. ITS1-PCR of purified parasite DNA yielded an amplification product approximately 540 bp in size. Nucleotide sequence of ITS1 gene of CB2 isolate had 530 bp while CK5, DH4, DJ3, and PH1 isolates had 532 bp, whereas, PK6 isolates had 533 bp size. Blast data of the Indian isolates revealed 99 % homology with other available sequences of Multiple alignment of nucleotide sequence of ITS1 gene variants from Indian isolates with selected homologous sequences from GenBank revealed that nucleotide substitution mostly occurred at the position of 101-103, 218-223, 243-244, 301-396 and 470-480. The isolates PH1, CK5, DH4 and DJ3 were found more associated with isolates from the Philippines, Thailand, Iran, Egypt and China, whereas, PK6 and CB2 isolates were related to each other and were phylogenetically distant from rest of the Indian isolates used in this study. Based on the ITS1 rDNA sequence, the Neighbour-Joining consensus tree indicated clear evidence of existence of genetic diversity among isolates from India.
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http://dx.doi.org/10.1007/s12639-016-0843-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5447620PMC
June 2017

Naturally Acquired Human Antibodies Against Reticulocyte-Binding Domains of Plasmodium vivax Proteins, PvRBP2c and PvRBP1a, Exhibit Binding-Inhibitory Activity.

J Infect Dis 2017 05;215(10):1558-1568

Malaria Group, International Centre for Genetic Engineering and Biotechnology.

Background: Crucial gaps in our understanding of Plasmodium vivax reticulocyte invasion and protective immunity have hampered development of vivax vaccines. P. vivax exclusively invades reticulocytes that is mediated by the P. vivax reticulocyte-binding proteins (PvRBPs) specifically PvRBP2c and PvRBP1a. Vivax infections in Duffy-null individuals have suggested the evolution of alternate invasion pathways that may be mediated by the PvRBPs. Thus, PvRBPs appear as potential targets for efficacious P. vivax neutralization. However, there are limited data validating their vaccine efficacy. In the absence of vivax invasion assays, binding-inhibitory activity of antibodies has been reported to be associated with protection and a measure of vaccine potential.

Methods: -based analysis was performed of the PvRBP reticulocyte-binding properties and binding-inhibitory activity of specific anti-PvRBP2c/PvRBP1a human antibodies.

Results: PvRBP2c and PvRBP1a displayed a distinct reticulocyte-binding specificity, and their specific reticulocyte-binding domains were mapped within their N-terminal regions. Importantly, naturally acquired antibodies against the reticulocyte-binding domains efficaciously blocked reticulocyte binding of native PvRBPs, suggesting that the human immune system produced functional binding-inhibitory antibodies through exposure to vivax malaria.

Conclusions: Reticulocyte-binding domains of PvRBP2c/PvRBP1a are targets of naturally acquired binding-inhibitory antibodies, substantiating their promise as candidate antigens against which vaccine-inducible immunity could potentially be boosted through natural infections.
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http://dx.doi.org/10.1093/infdis/jix170DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5853946PMC
May 2017

A novel Plasmodium falciparum rhoptry associated adhesin mediates erythrocyte invasion through the sialic-acid dependent pathway.

Sci Rep 2016 07 7;6:29185. Epub 2016 Jul 7.

Laboratory of Malaria and Vaccine Research, School of Biotechnology, Jawaharlal Nehru University, New Delhi, India.

Erythrocyte invasion by Plasmodium falciparum merozoites is central to blood-stage infection and malaria pathogenesis. This intricate process is coordinated by multiple parasite adhesins that bind erythrocyte receptors and mediate invasion through several alternate pathways. P. falciparum expresses 2700 genes during the blood-stages, of which the identity and function of many remains unknown. Here, we have identified and characterized a novel P. falciparum rhoptry associated adhesin (PfRA) that mediates erythrocyte invasion through the sialic-acid dependent pathway. PfRA appears to play a significant functional role as it is conserved across different Plasmodium species. It is localized in the rhoptries and further translocated to the merozoite surface. Both native and recombinant PfRA specifically bound erythrocytes in a sialic-acid dependent, chymotrypsin and trypsin resistant manner, which was abrogated by PfRA antibodies confirming a role in erythrocyte invasion. PfRA antibodies inhibited erythrocyte invasion and in combination with antibodies against other parasite ligands produced an additive inhibitory effect, thus validating its important role in erythrocyte invasion. We have thus identified a novel P. falciparum adhesin that binds with a sialic acid containing erythrocyte receptor. Our observations substantiate the strategy to block P. falciparum erythrocyte invasion by simultaneously targeting multiple conserved merozoite antigens involved in alternate invasion pathways.
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http://dx.doi.org/10.1038/srep29185DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4935899PMC
July 2016

Evidence for the Nucleo-Apical Shuttling of a Beta-Catenin Like Plasmodium falciparum Armadillo Repeat Containing Protein.

PLoS One 2016 1;11(2):e0148446. Epub 2016 Feb 1.

Laboratory of Malaria and Vaccine Research, School of Biotechnology, Jawaharlal Nehru University, New Delhi, India.

Eukaryotic Armadillo (ARM) repeat proteins are multifaceted with prominent roles in cell-cell adhesion, cytoskeletal regulation and intracellular signaling among many others. One such ARM repeat containing protein, ARM Repeats Only (ARO), has recently been demonstrated in both Toxoplasma (TgARO) and Plasmodium (PfARO) parasites to be targeted to the rhoptries during the late asexual stages. TgARO has been implicated to play an important role in rhoptry positioning i.e. directing the rhoptry towards the apical end of the parasite. Here, we report for the first time that PfARO exhibits a DNA binding property and a dynamic sub-cellular localization between the nucleus (early schizont) and rhoptry (late schizont) during the different stages of the asexual blood-stage life cycle. PfARO possesses a putative nuclear export signal (NES) and the nucleo-apical shuttling was sensitive to Leptomycin B (LMB) suggesting that the nuclear export was mediated by CRM1. Importantly, PfARO specifically bound an A-T rich DNA sequence of the P. falciparum Gyrase A (PfgyrA) gene, suggesting that the DNA binding specificity of PfARO is likely due to the AT-richness of the probe. This is a novel functional characteristic that has not been reported previously for any P. falciparum ARM containing protein and suggests a putative role for PfARO in gene regulation. This study describes for the first time a conserved P. falciparum ARM repeat protein with a high degree of functional versatility.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0148446PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4734682PMC
July 2016

Identification and localization of a Novel Invasin of Plasmodium falciparum.

Mol Biochem Parasitol 2015 Aug 30;202(2):38-43. Epub 2015 Sep 30.

Malaria Group, International Centre for Genetic Engineering and Biotechnology, P. O. Box 10504, Aruna Asaf Ali Marg, New Delhi 110067, India. Electronic address:

Plasmodium falciparum is the causative organism for the most severe form of malaria among humans. The clinical symptoms are accredited to the asexual stage of parasite life cycle, involving merozoite invasion of erythrocyte, development and re-invasion into the new erythrocyte. Interaction of parasite proteins present on the surface or secreted from apical organelles with the host receptors is indispensable for the invasion process. Identification and elucidation of precise localization and function of these proteins will not only enhance our understanding of this process but will also aid in the progress of development of treatment strategies against malaria. Here we report the identification and localization of a novel protein, PfAEP (P. falciparum Apical Exonemal Protein) (PF3D7_1137200/ PF11_0383) which is conserved across Plasmodium species. Transcription and translation analysis have confirmed its expression in the schizont stage of P. falciparum. Super-resolution microscopy in schizonts and merozoites revealed its localization in the exonemes of P. falciparum.
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http://dx.doi.org/10.1016/j.molbiopara.2015.09.004DOI Listing
August 2015

Comparative genomic analysis of buffalo (Bubalus bubalis) NOD1 and NOD2 receptors and their functional role in in-vitro cellular immune response.

PLoS One 2015 18;10(3):e0119178. Epub 2015 Mar 18.

Animal Genomics Lab, Animal Biotechnology Centre, National Dairy Research Institute, Karnal, 132001, Haryana, India.

Nucleotide binding and oligomerization domain (NOD)-like receptors (NLRs) are innate immune receptors that recognize bacterial cell wall components and initiate host immune response. Structure and function of NLRs have been well studied in human and mice, but little information exists on genetic composition and role of these receptors in innate immune system of water buffalo--a species known for its exceptional disease resistance. Here, a comparative study on the functional domains of NOD1 and NOD2 was performed across different species. The NOD mediated in-vitro cellular responses were studied in buffalo peripheral blood mononuclear cells, resident macrophages, mammary epithelial, and fibroblast cells. Buffalo NOD1 (buNOD1) and buNOD2 showed conserved domain architectures as found in other mammals. The domains of buNOD1 and buNOD2 showed analogy in secondary and tertiary conformations. Constitutive expressions of NODs were ubiquitous in different tissues. Following treatment with NOD agonists, peripheral lymphocytes showed an IFN-γ response along-with production of pro-inflammatory cytokines. Alveolar macrophages and mammary epithelial cells showed NOD mediated in-vitro immune response through NF-κB dependent pathway. Fibroblasts showed pro-inflammatory cytokine response following agonist treatment. Our study demonstrates that both immune and non-immune cells could generate NOD-mediated responses to pathogens though the type and magnitude of response depend on the cell types. The structural basis of ligand recognition by buffalo NODs and knowledge of immune response by different cell types could be useful for development of non-infective innate immune modulators and next generation anti-inflammatory compounds.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0119178PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4365024PMC
March 2016

Multiprotein complex between the GPI-anchored CyRPA with PfRH5 and PfRipr is crucial for Plasmodium falciparum erythrocyte invasion.

Proc Natl Acad Sci U S A 2015 Jan 12;112(4):1179-84. Epub 2015 Jan 12.

Malaria Group, International Centre for Genetic Engineering & Biotechnology (ICGEB), New Delhi, India 110067; and School of Biotechnology, Jawaharlal Nehru University (JNU), New Delhi, India 110067

Erythrocyte invasion by Plasmodium falciparum merozoites is a highly intricate process in which Plasmodium falciparum reticulocyte binding-like homologous protein 5 (PfRH5) is an indispensable parasite ligand that binds with its erythrocyte receptor, Basigin. PfRH5 is a leading blood-stage vaccine candidate because it exhibits limited polymorphisms and elicits potent strain-transcending parasite neutralizing antibodies. However, the mechanism by which it is anchored to the merozoite surface remains unknown because both PfRH5 and the PfRH5-interacting protein (PfRipr) lack transmembrane domains and GPI anchors. Here we have identified a conserved GPI-linked parasite protein, Cysteine-rich protective antigen (CyRPA) as an interacting partner of PfRH5-PfRipr that tethers the PfRH5/PfRipr/CyRPA multiprotein complex on the merozoite surface. CyRPA was demonstrated to be GPI-linked, localized in the micronemes, and essential for erythrocyte invasion. Specific antibodies against the three proteins successfully detected the intact complex in the parasite and coimmunoprecipitated the three interacting partners. Importantly, full-length CyRPA antibodies displayed potent strain-transcending invasion inhibition, as observed for PfRH5. CyRPA does not bind with erythrocytes, suggesting that its parasite neutralizing antibodies likely block its critical interaction with PfRH5-PfRipr, leading to a blockade of erythrocyte invasion. Further, CyRPA and PfRH5 antibody combinations produced synergistic invasion inhibition, suggesting that simultaneous blockade of the PfRH5-Basigin and PfRH5/PfRipr/CyRPA interactions produced an enhanced inhibitory effect. Our discovery of the critical interactions between PfRH5, PfRipr, and the GPI-anchored CyRPA clearly defines the components of the essential PfRH5 adhesion complex for P. falciparum erythrocyte invasion and offers it as a previously unidentified potent target for antimalarial strategies that could abrogate formation of the crucial multiprotein complex.
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http://dx.doi.org/10.1073/pnas.1415466112DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4313826PMC
January 2015

Production and preclinical evaluation of Plasmodium falciparum MSP-119 and MSP-311 chimeric protein, PfMSP-Fu24.

Clin Vaccine Immunol 2014 Jun 30;21(6):886-97. Epub 2014 Apr 30.

Malaria Research Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi, India

A Plasmodium falciparum chimeric protein, PfMSP-Fu24, was constructed by genetically coupling immunodominant, conserved regions of two merozoite surface proteins, the 19-kDa region C-terminal region of merozoite surface protein 1 (PfMSP-119) and an 11-kDa conserved region of merozoite surface protein 3 (PfMSP-311), to augment the immunogenicity potential of these blood-stage malaria vaccine candidates. Here we describe an improved, efficient, and scalable process to produce high-quality PfMSP-Fu24. The chimeric protein was produced in Escherichia coli SHuffle T7 Express lysY cells that express disulfide isomerase DsbC. A two-step purification process comprising metal affinity followed by cation exchange chromatography was developed, and we were able to obtain PfMSP-Fu24 with purity above 99% and with a considerable yield of 23 mg/liter. Immunogenicity of PfMSP-Fu24 formulated with several adjuvants, including Adjuplex, Alhydrogel, Adjuphos, Alhydrogel plus glucopyranosyl lipid adjuvant, aqueous (GLA-AF), Adjuphos+GLA-AF, glucopyranosyl lipid adjuvant-stable emulsion (GLA-SE), and Freund's adjuvant, was evaluated. PfMSP-Fu24 formulated with GLA-SE and Freund's adjuvant in mice and with Alhydrogel and Freund's adjuvant in rabbits produced high titers of PfMSP-119 and PfMSP-311-specific functional antibodies. Some of the adjuvant formulations induced inhibitory antibody responses and inhibited in vitro growth of P. falciparum parasites in the presence as well as in the absence of human monocytes. These results suggest that PfMSP-Fu24 can form a constituent of a multistage malaria vaccine.
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http://dx.doi.org/10.1128/CVI.00179-14DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4054244PMC
June 2014

Bacterially expressed full-length recombinant Plasmodium falciparum RH5 protein binds erythrocytes and elicits potent strain-transcending parasite-neutralizing antibodies.

Infect Immun 2014 Jan 14;82(1):152-64. Epub 2013 Oct 14.

Malaria Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), New Delhi, India.

Plasmodium falciparum reticulocyte binding-like homologous protein 5 (PfRH5) is an essential merozoite ligand that binds with its erythrocyte receptor, basigin. PfRH5 is an attractive malaria vaccine candidate, as it is expressed by a wide number of P. falciparum strains, cannot be genetically disrupted, and exhibits limited sequence polymorphisms. Viral vector-induced PfRH5 antibodies potently inhibited erythrocyte invasion. However, it has been a challenge to generate full-length recombinant PfRH5 in a bacterial-cell-based expression system. In this study, we have produced full-length recombinant PfRH5 in Escherichia coli that exhibits specific erythrocyte binding similar to that of the native PfRH5 parasite protein and also, importantly, elicits potent invasion-inhibitory antibodies against a number of P. falciparum strains. Antibasigin antibodies blocked the erythrocyte binding of both native and recombinant PfRH5, further confirming that they bind with basigin. We have thus successfully produced full-length PfRH5 as a functionally active erythrocyte binding recombinant protein with a conformational integrity that mimics that of the native parasite protein and elicits potent strain-transcending parasite-neutralizing antibodies. P. falciparum has the capability to develop immune escape mechanisms, and thus, blood-stage malaria vaccines that target multiple antigens or pathways may prove to be highly efficacious. In this regard, antibody combinations targeting PfRH5 and other key merozoite antigens produced potent additive inhibition against multiple worldwide P. falciparum strains. PfRH5 was immunogenic when immunized with other antigens, eliciting potent invasion-inhibitory antibody responses with no immune interference. Our results strongly support the development of PfRH5 as a component of a combination blood-stage malaria vaccine.
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http://dx.doi.org/10.1128/IAI.00970-13DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3911863PMC
January 2014

Identification and characterization of a novel Plasmodium falciparum adhesin involved in erythrocyte invasion.

PLoS One 2013 13;8(9):e74790. Epub 2013 Sep 13.

Malaria Research Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), New Delhi, India.

Malaria remains a major health problem worldwide. All clinical symptoms of malaria are attributed to the asexual blood stages of the parasite life cycle. Proteins resident in apical organelles and present on the surface of P. falciparum merozoites are considered promising candidates for the development of blood stage malaria vaccines. In the present study, we have identified and characterized a microneme associated antigen, PfMA [PlasmoDB Gene ID: PF3D7_0316000, PFC0700c]. The gene was selected by applying a set of screening criteria such as transcriptional upregulation at late schizogony, inter-species conservation and the presence of signal sequence or transmembrane domains. The gene sequence of PfMA was found to be conserved amongst various Plasmodium species. We experimentally demonstrated that the transcript for PfMA was expressed only in the late blood stages of parasite consistent with a putative role in erythrocyte invasion. PfMA was localized by immunofluorescence and immuno-electron microscopy to be in the micronemes, an apical organelle of merozoites. The functional role of the PfMA protein in erythrocyte invasion was identified as a parasite adhesin involved in direct attachment with the target erythrocyte. PfMA was demonstrated to bind erythrocytes in a sialic acid independent, chymotrypsin and trypsin resistant manner and its antibodies inhibited P. falciparum erythrocyte invasion. Invasion of erythrocytes is a complex multistep process that involves a number of redundant ligand-receptor interactions many of which still remain unknown and even uncharacterized. Our work has identified and characterized a novel P. falciparum adhesin involved in erythrocyte invasion.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0074790PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3772933PMC
June 2014

Current status of malaria vaccines.

Indian J Pediatr 2013 Jun 19;80(6):441-3. Epub 2013 Apr 19.

Malaria Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), Aruna Asaf Ali Marg, New Delhi 110067, India.

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http://dx.doi.org/10.1007/s12098-013-1031-xDOI Listing
June 2013