Publications by authors named "Kishore R Alugupalli"

26 Publications

  • Page 1 of 1

IL-7 Enables Antibody Responses to Bacterial Polysaccharides by Promoting B Cell Receptor Diversity.

J Immunol 2018 08 13;201(4):1229-1240. Epub 2018 Jul 13.

Department of Microbiology and Immunology, Sidney Kimmel Medical College, Sidney Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA 19107; and

Polysaccharide vaccines such as the Vi polysaccharide (ViPS) of serovar Typhi induce efficient Ab responses in adults but not in young children. The reasons for this difference are not understood. IL-7 dependency in B cell development increases progressively with age. IL-7Rα-mediated signals are required for the expression of many V gene segments that are distal to D-J in the IgH locus and for the complete diversification of the BCR repertoire. Therefore, we hypothesized that B cells generated in the absence of IL-7 do not recognize a wide range of Ags because of a restricted BCR repertoire. Compared with adult wildtype mice, young wildtype mice and IL-7-deficient adult mice generated a significantly reduced Ab response to ViPS. Additionally, ViPS-binding B cells in adult wildtype mice predominantly used distal V gene segments. Transgenic expression of either IL-7 or a BCR encoded by a distal V gene segment permitted young mice to respond efficiently to bacterial polysaccharides. These results indicate that restricted V gene usage early in life results in a paucity of Ag-specific B cell precursors, thus limiting antipolysaccharide responses.
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http://dx.doi.org/10.4049/jimmunol.1800162DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6085875PMC
August 2018

Terminal Deoxynucleotidyl Transferase Is Not Required for Antibody Response to Polysaccharide Vaccines against Streptococcus pneumoniae and Salmonella enterica Serovar Typhi.

Infect Immun 2018 09 22;86(9). Epub 2018 Aug 22.

Department of Microbiology and Immunology, Sidney Kimmel Medical College, Sidney Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania, USA

B cell antigen receptor (BCR) diversity increases by several orders of magnitude due to the action of terminal deoxynucleotidyl transferase (TdT) during V(D)J recombination. Unlike adults, infants have limited BCR diversity, in part due to reduced expression of TdT. Since human infants and young mice respond poorly to polysaccharide vaccines, such as the pneumococcal polysaccharide vaccine Pneumovax23 and Vi polysaccharide (ViPS) of serovar Typhi, we tested the contribution of TdT-mediated BCR diversity in response to these vaccines. We found that TdT and TdT mice generated comparable antibody responses to Pneumovax23 and survived challenge. Moreover, passive immunization of B cell-deficient mice with serum from Pneumovax23-immunized TdT or TdT mice conferred protection. TdT and TdT mice generated comparable levels of anti-ViPS antibodies and antibody-dependent, complement-mediated bactericidal activity against Typhi To test the protective immunity conferred by ViPS immunization , TdT and TdT mice were challenged with a chimeric serovar Typhimurium strain expressing ViPS, since mice are nonpermissive hosts for Typhi infection. Compared to their unimmunized counterparts, immunized TdT and TdT mice challenged with ViPS-expressing Typhimurium exhibited a significant reduction in the bacterial burden and liver pathology. These data suggest that the impaired antibody response to the Pneumovax23 and ViPS vaccines in the young is not due to limited TdT-mediated BCR diversification.
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http://dx.doi.org/10.1128/IAI.00211-18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6105908PMC
September 2018

An Unmutated IgM Response to the Vi Polysaccharide of Typhi Contributes to Protective Immunity in a Murine Model of Typhoid.

J Immunol 2018 06 9;200(12):4078-4084. Epub 2018 May 9.

Department of Microbiology and Immunology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA 19107; and

T cell-dependent B cell responses typically develop in germinal centers. Abs generated during such responses are isotype switched and have a high affinity to the Ag because of somatic hypermutation of Ab genes. B cell responses to purified polysaccharides are T cell independent and do not result in the formation of bona fide germinal centers, and the dominant Ab isotype produced during such responses is IgM with very few or no somatic mutations. Activation-induced cytidine deaminase (AID) is required for both somatic hypermutation and Ig isotype switching in humans and mice. To test the extent to which unmutated polysaccharide-specific IgM confers protective immunity, we immunized wildtype and AID mice with either heat-killed serovar Typhi ( Typhi) or purified Vi polysaccharide (ViPS). We found that wildtype and AID mice immunized with heat-killed Typhi generated similar anti-ViPS IgM responses. As expected, wildtype, but not AID mice generated ViPS-specific IgG. However, the differences in the Ab-dependent killing of Typhi mediated by the classical pathway of complement activation were not statistically significant. In ViPS-immunized wildtype and AID mice, the ViPS-specific IgM levels and Typhi bactericidal Ab titers at 7 but not at 28 d postimmunization were also comparable. To test the protective immunity conferred by these immunizations, mice were challenged with a chimeric Typhimurium strain expressing ViPS. Compared with their naive counterparts, immunized wildtype and AID mice exhibited significantly reduced bacterial burden regardless of the route of infection. These data indicate that an unmutated IgM response to ViPS contributes to protective immunity to Typhi.
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http://dx.doi.org/10.4049/jimmunol.1701348DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6033073PMC
June 2018

Humoral Immunity in Mice Transplanted with Hematopoietic Stem Cells Derived from Human Umbilical Cord Blood Recapitulates That of Human Infants.

Stem Cells Dev 2017 12 3;26(23):1715-1723. Epub 2017 Nov 3.

Department of Microbiology and Immunology, Sidney Kimmel Cancer Center, Sidney Kimmel Medical College, Thomas Jefferson University , Philadelphia, Pennsylvania.

Immunodeficient mice transplanted with human hematopoietic stem cells (HSCs) have been referred to as "Human Immune System" (HIS) mice and are a translational platform for studying human immune responses in vivo. Human HSC sources used in generating HIS mice include fetal liver (FL), umbilical cord blood (CB), and adult bone marrow (BM). Since HSCs from FL, CB, and BM are produced at various stages of human development, we tested whether mice transplanted with these three HSCs differ in their immune responses. We found that compared with CB HSCs or FL HSCs, adult BM HSCs reconstitute the immune system poorly. The resulting HIS mice do not mount an antibody response to Borrelia hermsii infection and as a consequence suffer persistently high levels of bacteremia. While both CB and FL HSCs yield comparable levels of immune reconstitution of HIS mice resulting in robust anti-B. hermsii immune responses, FL HSC-transplanted mice exhibited a discernable difference in their human B cell maturity as identified by an increased frequency of CD10 immature B cells and relatively smaller lymphoid follicles compared with CB HSC-transplanted mice. Although CB HSC-transplanted mice generated robust antibody responses to B. hermsii and specific protein antigens of B. hermsii, they failed to respond to Salmonella typhi Vi polysaccharide, a classical T cell-independent antigen. This situation resembles that seen in human infants and young children. Therefore, CB HSC-transplanted mice may serve as a translation platform to explore approaches to overcome the impaired antipolysaccharide responses characteristic of human infants.
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http://dx.doi.org/10.1089/scd.2017.0156DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5706618PMC
December 2017

APRIL:TACI axis is dispensable for the immune response to rabies vaccination.

Antiviral Res 2017 08 12;144:130-137. Epub 2017 Jun 12.

Department of Microbiology and Immunology, Thomas Jefferson University, Philadelphia, PA, United States; Jefferson Vaccine Center, Thomas Jefferson University, Philadelphia, PA, United States. Electronic address:

There is significant need to develop a single-dose rabies vaccine to replace the current multi-dose rabies vaccine regimen and eliminate the requirement for rabies immune globulin in post-exposure settings. To accomplish this goal, rabies virus (RABV)-based vaccines must rapidly activate B cells to secrete antibodies which neutralize pathogenic RABV before it enters the CNS. Increased understanding of how B cells effectively respond to RABV-based vaccines may improve efforts to simplify post-exposure prophylaxis (PEP) regimens. Several studies have successfully employed the TNF family cytokine a proliferation-inducing ligand (APRIL) as a vaccine adjuvant. APRIL binds to the receptors TACI and B cell maturation antigen (BCMA)-expressed by B cells in various stages of maturation-with high affinity. We discovered that RABV-infected primary murine B cells upregulate APRIL ex vivo. Cytokines present at the time of antigen exposure affect the outcome of vaccination by influencing T and B cell activation and GC formation. Therefore, we hypothesized that the presence of APRIL at the time of RABV-based vaccine antigen exposure would support the generation of protective antibodies against RABV glycoprotein (G). In an effort to improve the response to RABV vaccination, we constructed and characterized a live recombinant RABV-based vaccine vector which expresses murine APRIL (rRABV-APRIL). Immunogenicity testing in mice demonstrated that expressing APRIL from the RABV genome does not impact the primary antibody response against RABV G compared to RABV alone. In order to evaluate the necessity of APRIL for the response to rabies vaccination, we compared the responses of APRIL-deficient and wild-type mice to immunization with rRABV. APRIL deficiency does not affect the primary antibody response to vaccination. Furthermore, APRIL expression by the vaccine did not improve the generation of long-lived antibody-secreting plasma cells (PCs) as serum antibody levels were equivalent in response to rRABV-APRIL and the vector eight weeks after immunization. Moreover, APRIL is dispensable for the long-lived antibody-secreting PC response to rRABV vaccination as anti-RABV G IgG levels were similar in APRIL-deficient and wild-type mice six months after vaccination. Mice lacking the APRIL receptor TACI demonstrated primary anti-RABV G antibody responses similar to wild-type mice following immunization with the vaccine vector indicating that this response is independent of TACI-mediated signals. Collectively, our findings demonstrate that APRIL and associated TACI signaling is dispensable for the immune response to RABV-based vaccination.
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http://dx.doi.org/10.1016/j.antiviral.2017.06.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5547903PMC
August 2017

BAFF receptor and TACI in B-1b cell maintenance and antibacterial responses.

Ann N Y Acad Sci 2015 Dec 11;1362:57-67. Epub 2015 May 11.

Department of Microbiology and Immunology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania.

Although evidence of the protective immunity conferred by B-1b cells (CD19(+) B220(+) IgM(hi) Mac1(+) CD5(-)) has been established, the mechanisms governing the maintenance and activation of B-1b cells following pathogen encounter remain unclear. B cell-activating factor (BAFF) and a proliferation-inducing ligand (APRIL) mediate their function in mature B cells through the BAFF receptor (BAFFR) and transmembrane activator and CAML interactor (TACI). BAFFR-deficient mice have lower numbers of B-1b cells, and this reduction is directly proportional to BAFFR levels. The generation of B-1b cells is also dependent on the strength of B cell receptor (BCR) signaling. Mice with impaired BCR signaling, such as X-linked immunodeficient (xid) mice, have B-1b cell deficiency, indicating that both BCR- and BAFFR-mediated signaling are critical for B-1b cell homeostasis. Borrelia hermsii induces expansion and persistence of B-1b cells in xid mice, and these B-1b cells provide a heightened protective response. Toll-like receptor (TLR)-mediated stimulation of xid B cells results in a significant increase in TACI expression and restoration of TACI-mediated functions. The activation of TLR signaling by B. hermsii and BCR/TLR costimulation-mediated upregulation of BAFFR and TACI on B-1b cells suggests that B-1b cell maintenance and function following bacterial exposure may depend on BAFFR- and TACI-mediated signaling. In fact, the loss of both BAFFR and TACI results in a greater impairment in anti-B. hermsii responses compared to deficiency of BAFFR or TACI alone.
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http://dx.doi.org/10.1111/nyas.12772DOI Listing
December 2015

Impaired B cell receptor signaling is responsible for reduced TACI expression and function in X-linked immunodeficient mice.

J Immunol 2014 Apr 19;192(8):3582-95. Epub 2014 Mar 19.

Laboratory of Bacterial Polysaccharides, Division of Bacterial Parasitic and Allergenic Products, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Bethesda, MD, 20892.

Immune response to T cell independent type 2 (TI-2) Ags, such as bacterial polysaccharides, is severely impaired in X-linked immunodeficient (XID) mice. In this study, we investigated the involvement of a proliferation-inducing ligand (APRIL) or BAFF and their receptors in the unresponsiveness of XID mouse to TI-2 Ags. We discovered that whereas serum BAFF levels were increased, the expression of the APRIL and BAFF receptor transmembrane activator and calcium-modulator and cyclophilin ligand interactor (TACI) was severely reduced in XID B cells. Moreover, B cells from XID mouse were unable to secrete Igs in response to APRIL or BAFF. In correlation with reduced TACI expression and impaired TACI function, APRIL or BAFF did not activate the classical NF-κB pathway in XID cells. Also correlating with the unaltered expression of BAFF receptor, BAFF stimulation induced the activation of the alternative NF-κB pathway in XID cells. Moreover, activation of MAPK pathway was ablated in APRIL-stimulated XID cells. Prestimulation of XID B cells with the TLR9 agonist, CpG led to a significant increase in TACI expression and restored TACI-mediated functions. CpG prestimulation also restored TACI-mediated signaling in APRIL- or BAFF-stimulated XID B cells. Finally, immunization of XID mouse with the prototype TI-2 Ag NP-Ficoll induced IgG and IgM Abs when CpG was given with NP-Ficoll. Collectively, these results suggest that reduced TACI expression is responsible for the unresponsiveness of XID mouse to TI-2 Ags and BCR activation controls TACI expression.
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http://dx.doi.org/10.4049/jimmunol.1203468DOI Listing
April 2014

Efficient B cell responses to Borrelia hermsii infection depend on BAFF and BAFFR but not TACI.

Infect Immun 2014 Jan 11;82(1):453-9. Epub 2013 Nov 11.

Department of Microbiology and Immunology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania, USA.

T cell-independent antibody responses develop rapidly, within 3 to 4 days, and are critical for preventing blood-borne pathogens from evolving into life-threatening infections. The interaction of BAFF, also known as BLyS, with its receptors BAFFR and TACI on B cells is critical for B cell homeostasis and function. Using a synthetic polysaccharide antigen, it has previously been shown that TACI is critical for T cell-independent antibody responses. To examine the role of BAFFR and TACI in T cell-independent antibody responses to an active infection, we utilized the Borrelia hermsii infection system. In this infection system, T cell-independent responses mediated by the B1b cell subset are critical for controlling bacteremia. We found that B1b cells express BAFFR and TACI and that the surface expression of both receptors is upregulated on B1b cells following exposure to whole B. hermsii cells. Surprisingly, we found that TACI(-/-) mice are not impaired either in specific antibody responses to B. hermsii or in controlling B. hermsii bacteremia. In contrast, TACI-deficient mice immunized with heat-killed type 3 serotype pneumococcus cells are impaired in generating pneumococcal polysaccharide-specific responses and succumb to challenge with live type 3 serotype pneumococcus, indicating that TACI is required for T cell-independent antibody responses to bacterial-associated polysaccharides. Although we have found that TACI is dispensable for controlling B. hermsii infection, mice deficient in BAFFR or BAFF exhibit impairment in B. hermsii-specific IgM responses and clearance of bacteremia. Collectively, these data indicate a disparity in the roles for TACI and BAFFR in primary T cell-independent antibody responses to bacterial pathogens.
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http://dx.doi.org/10.1128/IAI.01147-13DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3911873PMC
January 2014

Deciphering the role of Toll-like receptors in humoral responses to Borreliae.

Front Biosci (Schol Ed) 2012 Jan 1;4:699-712. Epub 2012 Jan 1.

Department of Microbiology and Immunology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA 19107, USA.

The bacteria of the genus Borrelia are arthropod-borne spirochetes that cause relapsing fever and Lyme disease in humans. Like most arthropod-borne pathogens, Borreliae must survive in the periphery of their vertebrate hosts to allow for transmission to another arthropod vector. These spatial and temporal restrictions require that Borreliae evade the adaptive immune response. Borreliae have evolved genetic mechanisms that alter their surface protein expression, thereby altering the antigenic target presented to the host. To control Borreliae infection, the host relies on a rapid humoral response. While it is clear that B cell antigen receptor signaling is a critical requirement for the specific antibody responses, growing evidence suggests that additional signaling by innate immune receptors such as Toll-like receptors is necessary for optimal T cell-dependent and T cell-independent antibody responses. This review is focused on the role of Toll-like receptors in B cell responses to relapsing fever and Lyme disease Borreliae.
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http://dx.doi.org/10.2741/s294DOI Listing
January 2012

Characteristics of Borrelia hermsii infection in human hematopoietic stem cell-engrafted mice mirror those of human relapsing fever.

Proc Natl Acad Sci U S A 2011 Dec 5;108(51):20707-12. Epub 2011 Dec 5.

Department of Microbiology and Immunology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA 19107, USA.

Rodents are natural reservoirs for a variety of species of Borrelia that cause relapsing fever (RF) in humans. The murine model of this disease recapitulates many of the clinical manifestations of the human disease and has revealed that T cell-independent antibody responses are required to resolve the bacteremic episodes. However, it is not clear whether such protective humoral responses are mounted in humans. We examined Borrelia hermsii infection in human hematopoietic stem cell-engrafted nonobese diabetic/SCID/IL-2Rγ(null) mice: "human immune system mice" (HISmice). Infection of these mice, which are severely deficient in lymphoid and myeloid compartments, with B. hermsii resulted in persistent bacteremia. In contrast, this infection in HISmice resulted in recurrent episodes of bacteremia, the hallmark of RF. The resolution of the primary episode of bacteremia was concurrent with the generation of B. hermsii-specific human IgM. Remarkably, HISmice generated antibody responses to the B. hermsii outer-membrane protein Factor H binding protein A. Sera from humans infected by B. hermsii have a similar reactivity, and studies in mice have shown that this response is generated by the B1b cell subset. HISmice contain several B-cell subsets, including those with the phenotype CD20(+)CD27(+)CD43(+)CD70(-), a proposed human equivalent of mouse B1 cells. Reduction of B cells by administration of anti-human CD20 antibody resulted in diminished anti-B. hermsii responses and persistent bacteremia in HISmice. These data indicate that analysis of B. hermsii infection in HISmice will serve as a model in which to study the cellular and molecular mechanisms involved in controlling human RF.
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http://dx.doi.org/10.1073/pnas.1108776109DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3251092PMC
December 2011

B1b lymphocyte-derived antibodies control Borrelia hermsii independent of Fcα/μ receptor and in the absence of host cell contact.

Immunol Res 2011 Dec;51(2-3):249-56

Department of Microbiology and Immunology, Kimmel Cancer Center, Thomas Jefferson University, 233 S 10th Street, Room 726, Philadelphia, PA 19107, USA.

The critical role of IgM in controlling pathogen burden has been demonstrated in a variety of infection models. In the murine model of Borrelia hermsii infection, IgM is necessary and sufficient for the rapid clearance of bacteremia. Convalescent, but not naïve, B1b cells generate a specific IgM response against B. hermsii, but the mechanism of IgM-mediated protection is unknown. Here, we show that neither Fcα/μR, a high-affinity receptor for IgM, nor IgM-dependent complement activation is required for controlling B. hermsii. Bacteria in diffusion chambers with a pore size impermeable to cells were killed when diffusion chambers were implanted into either convalescent or passively immunized mice. Furthermore, adoptively transferred convalescent B1b cells in Rag1(-/-) mice produced specific IgM that also cleared B. hermsii in diffusion chambers independent of complement. These results demonstrate that IgM-mediated clearance of B. hermsii does not require opsonophagocytosis and indicate that a mechanism for in vivo B1b cell-mediated protection is through the generation of bactericidal IgM.
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http://dx.doi.org/10.1007/s12026-011-8260-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6707740PMC
December 2011

Toll-like receptor 2 deficiency results in impaired antibody responses and septic shock during Borrelia hermsii infection.

Infect Immun 2010 Nov 9;78(11):4579-88. Epub 2010 Aug 9.

Department of Microbiology and Immunology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA 19107, USA.

Overwhelming bacteremia is a leading cause of death. To understand the mechanisms involved in protective antibody and pathological inflammatory responses during bacteremia, we have been studying the murine model of Borrelia hermsii infection. Toll-like receptor (TLR) signaling plays an important role in generating the rapid anti-B. hermsii antibody responses required for the resolution of bacteremia. Using NF-κB reporter assays, we found that B. hermsii activates TLR2 and TLR9. However, TLR2(-/-) TLR9(-/-) mice exhibited an impairment in anti-B. hermsii antibody responses similar to that of TLR2(-/-) mice. Moreover, the impairment in the antibody responses of TLR2(-/-) mice or TLR2(-/-) TLR9(-/-) mice coincides with an order-of-magnitude-higher bacteremia, and death results from septic shock, as evidenced by a dysregulated systemic cytokine response and characteristic organ pathology. Since TLR2 appears to be the major extracellular sensor stimulated by B. hermsii, we hypothesized that during elevated bacteremia the activation of intracellular sensors of bacteria triggers dysregulated inflammation in TLR2(-/-) mice. Indeed, blocking the internalization of B. hermsii prevented the induction of inflammatory cytokine responses in TLR2-deficient cells. Furthermore, we found that B. hermsii activates the cytoplasmic sensor nucleotide-binding oligomerization domain 2 (NOD2). Macrophages deficient in both TLR2 and NOD2 have impaired cytokine responses to B. hermsii compared to cells lacking TLR2 alone, and B. hermsii-infected TLR2(-/-) NOD2(-/-) mice exhibited improved survival compared to TLR2(-/-) mice. These data demonstrate that TLR2 is critical for protective immunity and suggest that, during heightened bacteremia, recognition of bacterial components by intracellular sensors can lead to pathological inflammatory responses.
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http://dx.doi.org/10.1128/IAI.00438-10DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2976319PMC
November 2010

T-cell-independent immune responses do not require CXC ligand 13-mediated B1 cell migration.

Infect Immun 2010 Sep 28;78(9):3950-6. Epub 2010 Jun 28.

Department of Microbiology and Immunology, Thomas Jefferson University, 233 South 10th Street, BLSB 726, Philadelphia, PA 19107, USA.

The dynamic movement of B cells increases the probability of encountering specific antigen and facilitates cell-cell interactions required for mounting a rapid antibody response. B1a and B1b cells are enriched in the coelomic cavity, contribute to T-cell-independent (TI) antibody responses, and increase in number upon antigen exposure. B1 cell movement is largely governed by Cxc ligand 13 (Cxcl13), and mice deficient in this chemokine have a severe reduction in peritoneal B1 cells. In this study, we examined the role of Cxcl13-dependent B cell migration using Borrelia hermsii infection or intraperitoneal immunization with pneumococcal polysaccharide or 4-hydroxy-3-nitrophenyl-acetyl (NP)-Ficoll, all of which induce robust antibody responses from B1b cells. Surprisingly, we found that antibody responses to B. hermsii or to FhbA, an antigenic target of B1b cells, and the resolution of bacteremia were indistinguishable between wild-type and Cxcl13-/- mice. Importantly, we did not observe an expansion of peritoneal B1b cell numbers in Cxcl13-/- mice. Nonetheless, mice that had resolved infection were resistant to reinfection, indicating that the peritoneal B1b cell reservoir is not required for controlling B. hermsii. Furthermore, despite a reduced peritoneal B1b compartment, immunization with pneumococcal polysaccharide vaccine yielded comparable antigen-specific antibody responses in wild-type and Cxcl13-/- mice and conferred protection against Streptococcus pneumoniae. Likewise, immunization with NP-Ficoll elicited similar antibody responses in wild-type and Cxcl13-/- mice. These data demonstrate that homing of B1 cells into the coelomic cavity is not a requirement for generating protective TI antibody responses, even when antigen is initially localized to this anatomical compartment.
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http://dx.doi.org/10.1128/IAI.00371-10DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2937435PMC
September 2010

IL-7-dependent B lymphocytes are essential for the anti-polysaccharide response and protective immunity to Streptococcus pneumoniae.

J Immunol 2010 Jul 26;185(1):525-31. Epub 2010 May 26.

Department of Microbiology and Immunology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA 19107, USA.

Young children are impaired in their response to T cell-independent (TI) Ags, such as pneumococcal polysaccharide (PPS). B lymphopoeisis early in life is IL-7 independent, whereas in adults it is IL-7 dependent. Therefore, we hypothesized that IL-7-driven B lymphopoiesis plays a critical role in promoting Ab responses to TI Ags. Young but not adult mice are impaired in responses to PPS vaccination and to 4-hydroxy-3-nitrophenyl-acetyl-Ficoll, a widely studied model TI Ag, and B1b cells generate Ab responses to these Ags. In this paper, we show that, despite having B1b, B1a, and MZ B cells-all of which are involved in TI responses-young wild-type or adult mice deficient either in IL-7 or in IL-7Ralpha are severely impaired in anti-PPS responses and do not survive Streptococcus pneumoniae challenge, indicating IL-7-dependent B cells are required for TI immunity. Consistent with this, PPS immunization induced a robust TI response in young IL-7 transgenic mice that was comparable to adult wild-type responses. Moreover, immunized young or adult IL-7 transgenic mice were completely resistant to S. pneumoniae challenge. Our data indicate that activating the IL-7 signaling pathway could restore impaired TI responses in the young.
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http://dx.doi.org/10.4049/jimmunol.0902841DOI Listing
July 2010

Induction of distinct neurologic disease manifestations during relapsing fever requires T lymphocytes.

J Immunol 2010 May 9;184(10):5859-64. Epub 2010 Apr 9.

Department of Microbiology and Immunology, Thomas Jefferson University, Philadelphia, PA 19107, USA.

Relapsing fever borreliosis is a multisystemic infection characterized primarily by bacteremia but can extend to the CNS. The incidence of CNS disease manifestations in humans depends on the infecting relapsing fever Borrelia species. In the murine model of Borrelia hermsii infection we found high incidence of distinct signs of CNS disease that ranged from a flaccid tail to complete paralysis of hind limbs. Infiltration of large number of T cells into the spinal cord of B. hermsii-infected mice and the upregulation of MHC class II and CD80 on infiltrating macrophages and on microglial cells suggested a role for T cell and Ag-presenting cell interactions in this pathogenesis. Indeed, B. hermsii infection did not induce CNS disease manifestations in T cell-deficient mice (TCR-beta x delta(-/-)), although it resulted in bacteremia comparable to wild-type (Wt) level. Moreover, the infiltration of immune cells into the spinal cord of TCR-beta x delta(-/-) mice was reduced and the resident microglial cells were not activated. Histopathological analysis of lumbar sections of the spinal cord confirmed severe inflammation in Wt but not in TCR-beta x delta(-/-) mice. Induction of CNS disease was dependent on the B. hermsii strain as well as on the ability of the host to control bacteremia. Mice that are impaired in controlling B. hermsii, such as CD14(-/-) mice, exhibited more severe CNS disease than Wt mice. This study demonstrates that distinct neurologic disease manifestations develop during relapsing fever and that T cells play a critical role in the induction of neuropathogenesis.
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http://dx.doi.org/10.4049/jimmunol.0902737DOI Listing
May 2010

Genetic control of the innate immune response to Borrelia hermsii influences the course of relapsing fever in inbred strains of mice.

Infect Immun 2010 Feb 7;78(2):586-94. Epub 2009 Dec 7.

Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worcester, MA 01655, USA.

Host susceptibility to infection is controlled in large measure by the genetic makeup of the host. Spirochetes of the genus Borrelia include nearly 40 species of vector-borne spirochetes that are capable of infecting a wide range of mammalian hosts, causing Lyme disease and relapsing fever. Relapsing fever is associated with high-level bacteremia, as well as hematologic manifestations, such as thrombocytopenia (i.e., low platelet numbers) and anemia. To facilitate studies of genetic control of susceptibility to Borrelia hermsii infection, we performed a systematic analysis of the course of infection using immunocompetent and immunocompromised inbred strains of mice. Our analysis revealed that sensitivity to B. hermsii infections is genetically controlled. In addition, whereas the role of adaptive immunity to relapsing fever-causing spirochetes is well documented, we found that innate immunity contributes significantly to the reduction of bacterial burden. Similar to human infection, the progression of the disease in mice was associated with thrombocytopenia and anemia. Histological and fluorescence in situ hybridization (FISH) analysis of infected tissues indicated that red blood cells (RBCs) were removed by tissue-resident macrophages, a process that could lead to anemia. Spirochetes in the spleen and liver were often visualized associated with RBCs, lending support to the hypothesis that direct interaction of B. hermsii spirochetes with RBCs leads to clearance of bacteria from the bloodstream by tissue phagocytes.
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http://dx.doi.org/10.1128/IAI.01216-09DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2812184PMC
February 2010

Effective preexposure and postexposure prophylaxis of rabies with a highly attenuated recombinant rabies virus.

Proc Natl Acad Sci U S A 2009 Jul 6;106(27):11300-5. Epub 2009 Jul 6.

Department of Microbiology and Immunology, Thomas Jefferson University, Philadelphia, PA 19107, USA.

Rabies remains an important public health problem with more than 95% of all human rabies cases caused by exposure to rabid dogs in areas where effective, inexpensive vaccines are unavailable. Because of their ability to induce strong innate and adaptive immune responses capable of clearing the infection from the CNS after a single immunization, live-attenuated rabies virus (RV) vaccines could be particularly useful not only for the global eradication of canine rabies but also for late-stage rabies postexposure prophylaxis of humans. To overcome concerns regarding the safety of live-attenuated RV vaccines, we developed the highly attenuated triple RV G variant, SPBAANGAS-GAS-GAS. In contrast to most attenuated recombinant RVs generated thus far, SPBAANGAS-GAS-GAS is completely nonpathogenic after intracranial infection of mice that are either developmentally immunocompromised (e.g., 5-day-old mice) or have inherited deficits in immune function (e.g., antibody production or type I IFN signaling), as well as normal adult animals. In addition, SPBAANGAS-GAS-GAS induces immune mechanisms capable of containing a CNS infection with pathogenic RV, thereby preventing lethal rabies encephalopathy. The lack of pathogenicity together with excellent immunogenicity and the capacity to deliver immune effectors to CNS tissues makes SPBAANGAS-GAS-GAS a promising vaccine candidate for both the preexposure and postexposure prophylaxis of rabies.
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http://dx.doi.org/10.1073/pnas.0905640106DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2706273PMC
July 2009

B cell multitasking is required to control nematode infection.

Immunity 2009 Mar;30(3):317-9

Department of Microbiology and Immunology, Thomas Jefferson University, Philadelphia, PA 19107, USA.

In this issue of Immunity, Wojciechowski et al. (2009) demonstrate that in addition to producing antibodies, B cells play pivotal roles in specific-antigen presentation and cytokine production for optimal T helper 2 responses required for protection against Heligmosomoides polygyrus.
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http://dx.doi.org/10.1016/j.immuni.2009.02.004DOI Listing
March 2009

Role of the innate immune system in autoimmune inflammatory demyelination.

Curr Med Chem 2008 ;15(11):1105-15

Division of Clinical Neurology, University of Nottingham, UK.

Considerable research has been devoted to the role of the adaptive immune system in the pathogenesis of autoimmune inflammatory demyelination (AID). AID is thought to occur spontaneously in patients with multiple sclerosis (MS), a common cause of neurological disability. AID is also observed in the best characterized animal model of MS, experimental autoimmune encephalomyelitis (EAE). The adaptive immune system recognizes and responds to antigens via highly specific T-cell receptors. Myelin-reactive T-cells may initiate pathological immune responses that lead to central nervous system damage in MS and EAE. By contrast, the innate immune system recognizes evolutionarily conserved structures that are common to invading pathogens with high efficiency for rapid recognition and elimination of viruses, bacteria, and fungi. This recognition is mediated by pattern-recognition receptors such as Toll-like receptors (TLRs) expressed on cells of the innate immune system (dendritic cells and CNS-resident cells, such as microglia) that have the potential to activate autoimmune responses by inducing the production of inflammatory cytokines and chemokines. Conversely, the innate immune system can also regulate autoimmune inflammation by inducing the production of immunoregulatory molecules such as type I interferons, which are currently used in the treatment of MS. We review the evidence that TLRs can exacerbate or regulate AID and discuss the therapeutic potential of targeting either process.
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http://dx.doi.org/10.2174/092986708784221458DOI Listing
July 2008

Complement factor H-binding protein, a putative virulence determinant of Borrelia hermsii, is an antigenic target for protective B1b lymphocytes.

J Immunol 2008 Apr;180(7):4858-64

Department of Microbiology and Immunology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA 19107, USA.

Vaccination is the most effective way to control infectious diseases. A variety of microbial pathogens use antigenic variation, an immune evasion strategy that poses a challenge for vaccine development. To understand protective immune responses against such pathogens, we have been studying Borrelia hermsii, a bacterium that causes recurrent bacteremia due to antigenic variation. An IgM response is necessary and sufficient to control B. hermsii infection. We have recently found a selective expansion of B1b cells concurrent with the resolution of B. hermsii bacteremia. B1b cells from convalescent but not naive mice confer long-lasting immunity, but the Ag(s) driving the protective IgM responses is unknown. Herein we demonstrate that convalescent B1b cell-derived IgM recognizes complement factor H-binding protein (FhbA), a B. hermsii outer-surface protein and putative virulence factor that does not undergo antigenic variation and is expressed by all clinical isolates. A progressive increase in the IgM response to FhbA correlated with the kinetics of B1b cell expansion, diminished the severity of bacteremic episodes, and led to the eventual resolution of the infection. These data indicate that FhbA is a specific target for protective B1b cell responses. Ags recognized by B1b cells may be considered as an important component in vaccination strategies.
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http://dx.doi.org/10.4049/jimmunol.180.7.4858DOI Listing
April 2008

The ArcA regulon and oxidative stress resistance in Haemophilus influenzae.

Mol Microbiol 2007 Jun;64(5):1375-90

Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worcester, MA 01655, USA.

Haemophilus influenzae transits between niches within the human host that are predicted to differ in oxygen levels. The ArcAB two-component signal transduction system controls gene expression in response to respiratory conditions of growth and has been implicated in bacterial pathogenesis, yet the mechanism is not understood. We undertook a genome-scale study to identify genes of the H. influenzae ArcA regulon. Deletion of arcA resulted in increased anaerobic expression of genes of the respiratory chain and of H. influenzae's partial tricarboxylic acid cycle, and decreased anaerobic expression levels of genes of polyamine metabolism, and iron sequestration. Deletion of arcA also conferred a susceptibility to transient exposure to hydrogen peroxide that was greater following anaerobic growth than after aerobic growth. Array data revealed that the dps gene, not previously assigned to the ArcA modulon in bacteria, exhibited decreased expression in the arcA mutant. Deletion of dps resulted in hydrogen peroxide sensitivity and complementation restored resistance, providing insight into the previously uncharacterized mechanism of arcA-mediated H(2)O(2) resistance. The results indicate a role for H. influenzae arcA and dps in pre-emptive defence against transitions from growth in low oxygen environments to aerobic exposure to hydrogen peroxide, an antibacterial oxidant produced by phagocytes during infection.
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http://dx.doi.org/10.1111/j.1365-2958.2007.05747.xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1974803PMC
June 2007

MyD88- and Bruton's tyrosine kinase-mediated signals are essential for T cell-independent pathogen-specific IgM responses.

J Immunol 2007 Mar;178(6):3740-9

Department of Microbiology and Immunology and Kimmel Cancer Center, Thomas Jefferson University, 233 South 10th Street, Philadelphia, PA 19107, USA.

Bacteremia is one of the leading causes of death by infectious disease. To understand the immune mechanisms required for the rapid control of bacteremia, we studied Borrelia hermsii, a bacterial pathogen that colonizes the blood stream of humans and rodents to an extremely high density. A T cell-independent IgM response is essential and sufficient for controlling B. hermsii bacteremia. Mice deficient in Bruton's tyrosine kinase (Btk), despite their known defect in BCR signaling, generated B. hermsii-specific IgM and resolved bacteremia, suggesting that an alternative activation or costimulatory pathway remained functional for T cell-independent B cells in Btk(-/-) mice. B. hermsii contains putative ligands for TLRs, and we found that mice deficient in TLR1, TLR2, or the TLR adaptor MyD88 generated anti-B. hermsii IgM with delayed kinetics and suffered more severe episodes of bacteremia. In striking contrast to the anti-B. hermsii IgM response in mice deficient only in Btk, mice deficient in both Btk and MyD88 were entirely incapable of generating B. hermsii-specific Ab or resolving bacteremia. The response to a T cell-dependent model Ag was unaffected in Btk(-/-) x MyD88(-/-) mice. These results suggest that MyD88 specifically promotes T cell-independent BCR signaling and that, in the absence of Btk, this TLR-mediated stimulation is a required component of this signal.
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http://dx.doi.org/10.4049/jimmunol.178.6.3740DOI Listing
March 2007

Divide and conquer: division of labor by B-1 B cells.

Immunity 2005 Jul;23(1):1-2

Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, Massachusetts 01655, USA.

Capsular polysaccharides enhance bacterial virulence. In this issue of Immunity, demonstrate a division of labor between the B-1 B cell subsets: natural antibodies from B-1a cells limit infection by Streptococcus pneumoniae, whereas B-1b cells generate the anticapsule-induced response that prevents fatal infection.
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http://dx.doi.org/10.1016/j.immuni.2005.07.001DOI Listing
July 2005

B1b lymphocytes confer T cell-independent long-lasting immunity.

Immunity 2004 Sep;21(3):379-90

Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worcester 01655, USA.

Many microbial pathogens employ antigenic variation as a strategy to evade the immune system, posing a challenge in vaccine development. To understand the requirements for immunity against such pathogens, we studied Borrelia hermsii, a relapsing fever bacterium. We found that mice deficient in T, follicular B, marginal zone B, or B1a lymphocytes resolved B. hersmii bacteremia and became resistant to reinfection. The resolution of bacteremia coincided with an expansion and persistence of B1b lymphocytes, and purified B1b lymphocytes from convalescent wild-type or TCR-betaxdelta-/- mice conferred immunity to Rag1-/- mice. The B1b lymphocytes in the reconstituted Rag1-/- mice provided long-lasting immunity by rapidly generating B. hermsii-specific IgM but not IgG upon bacterial challenge. Unmutated IgM is sufficient to eliminate B. hermsii, because AID-/- mice deficient in somatic hypermutation and class switch recombination efficiently resolved all bacteremic episodes. These data demonstrate that B1b lymphocytes can provide long-lasting T cell-independent IgM memory.
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http://dx.doi.org/10.1016/j.immuni.2004.06.019DOI Listing
September 2004

Spirochete-platelet attachment and thrombocytopenia in murine relapsing fever borreliosis.

Blood 2003 Oct 10;102(8):2843-50. Epub 2003 Jul 10.

Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, 55 Lake Ave N, Worcester, MA 01655, USA.

Thrombocytopenia is common in persons infected with relapsing fever Borreliae. We previously showed that the relapsing fever spirochete Borrelia hermsii binds to and activates human platelets in vitro and that, after platelet activation, high-level spirochete-platelet attachment is mediated by integrin alpha IIb beta 3, a receptor that requires platelet activation for full function. Here we established that B hermsii infection of the mouse results in severe thrombocytopenia and a functional defect in hemostasis caused by accelerated platelet loss. Disseminated intravascular coagulation, immune thrombocytopenic purpura, or splenic sequestration did not play a discernible role in this model. Instead, spirochete-platelet complexes were detected in the blood of infected mice, suggesting that platelet attachment by bacteria might result in platelet clearance. Consistent with this, splenomegaly and thrombocytopenia temporally correlated with spirochetemia, and the severity of thrombocytopenia directly correlated with the degree of spirochetemia. Activation of platelets and integrin alpha IIb beta 3 were apparently not required for bacterium-platelet binding or platelet clearance because the bacterium-bound platelets in the circulation were not activated, and platelet binding and thrombocytopenia during infection of beta 3-deficient and wild-type mice were indistinguishable. These findings suggest that thrombocytopenia of relapsing fever is the result of platelet clearance after beta 3-independent bacterial attachment to circulating platelets.
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http://dx.doi.org/10.1182/blood-2003-02-0426DOI Listing
October 2003

The resolution of relapsing fever borreliosis requires IgM and is concurrent with expansion of B1b lymphocytes.

J Immunol 2003 Apr;170(7):3819-27

Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worcester, MA 01655, USA.

The rate of pathogen clearance is a critical determinant of morbidity and mortality. We sought to characterize the immune response responsible for the remarkably rapid clearance of individual episodes of bacteremia caused by the relapsing fever bacterium, Borrelia hermsii. SCID or Rag(-/-) mice were incapable of resolving B. hermsii infection, indicating a critical role for T and/or B cells. TCR(-/-) mice, which lack T cells, and IL-7(-/-) mice, which are deficient in both T cells and follicular B cells, but not in B1 cells and splenic marginal zone (MZ) B cells, efficiently cleared B. hermsii. These findings suggested that B1 cells and/or MZ B cells, two B cell subsets that are known to participate in rapid, T-independent responses, might be involved. The efficient resolution of the episodes of moderate level bacteremia by splenectomized mice suggested that MZ B cells do not play the primary role in clearance of this bacterium. In contrast, xid mice, which are deficient in B1 cells, suffered more severe episodes of bacteremia than wild-type mice. The hypothesis that B1 cells are critical for clearance of B. hermsii was further supported by a selective expansion of the B1b (i.e., IgM(high), IgD(-/low), Mac1(+) CD23(-), and CD5(-)) cell subset in infected xid mice, which coincided with the eventual resolution of infection. Finally, mice selectively incapable of secreting IgM, the dominant isotype produced by B1 cells, were completely unable to clear B. hermsii. Together these results support the model that B1b cells generate the T-independent IgM required for the control and resolution of relapsing fever borreliosis.
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http://dx.doi.org/10.4049/jimmunol.170.7.3819DOI Listing
April 2003