Publications by authors named "Blake M Hauser"

47 Publications

Association of venous thromboembolism following pediatric traumatic spinal injuries with injury severity and longer hospital stays.

J Neurosurg Spine 2021 Sep 17:1-7. Epub 2021 Sep 17.

1Computational Neurosciences Outcomes Center, Department of Neurosurgery, Harvard Medical School, Brigham and Women's Hospital; and.

Objective: Venous thromboembolism (VTE) can cause significant morbidity and mortality in hospitalized patients, and may disproportionately occur in patients with limited mobility following spinal trauma. The authors aimed to characterize the epidemiology and clinical predictors of VTE in pediatric patients following traumatic spinal injuries (TSIs).

Methods: The authors conducted a retrospective cohort analysis of children who experienced TSI, including spinal fractures and spinal cord injuries, encoded within the National Trauma Data Bank from 2011 to 2014.

Results: Of the 22,752 pediatric patients with TSI, 192 (0.8%) experienced VTE during initial hospitalization. Proportionally, more patients in the VTE group (77%) than in the non-VTE group (68%) presented following a motor vehicle accident. Patients developing VTE had greater odds of presenting with moderate (adjusted odds ratio [aOR] 2.6, 95% confidence interval [CI] 1.4-4.8) or severe Glasgow Coma Scale scores (aOR 4.3, 95% CI 3.0-6.1), epidural hematoma (aOR 2.8, 95% CI 1.4-5.7), and concomitant abdominal (aOR 2.4, 95% CI 1.8-3.3) and/or lower extremity (aOR 1.5, 95% CI 1.1-2.0) injuries. They also had greater odds of being obese (aOR 2.9, 95% CI 1.6-5.5). Neither cervical, thoracic, nor lumbar spine injuries were significantly associated with VTE. However, involvement of more than one spinal level was predictive of VTE (aOR 1.3, 95% CI 1.0-1.7). Spinal cord injury at any level was also significantly associated with developing VTE (aOR 2.5, 95% CI 1.8-3.5). Patients with VTE stayed in the hospital an adjusted average of 19 days longer than non-VTE patients. They also had greater odds of discharge to a rehabilitative facility or home with rehabilitative services (aOR 2.6, 95% CI 1.8-3.6).

Conclusions: VTE occurs in a low percentage of hospitalized pediatric patients with TSI. Injury severity is broadly associated with increased odds of developing VTE; specific risk factors include concomitant injuries such as cranial epidural hematoma, spinal cord injury, and lower extremity injury. Patients with VTE also require hospital-based and rehabilitative care at greater rates than other patients with TSI.
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http://dx.doi.org/10.3171/2021.3.SPINE201981DOI Listing
September 2021

An AAV-based, room-temperature-stable, single-dose COVID-19 vaccine provides durable immunogenicity and protection in non-human primates.

Cell Host Microbe 2021 09 7;29(9):1437-1453.e8. Epub 2021 Aug 7.

Department of Microbiology and National Emerging Infectious Diseases Laboratories, Boston University School of Medicine, Boston, MA 02118, USA.

The SARS-CoV-2 pandemic has affected more than 185 million people worldwide resulting in over 4 million deaths. To contain the pandemic, there is a continued need for safe vaccines that provide durable protection at low and scalable doses and can be deployed easily. Here, AAVCOVID-1, an adeno-associated viral (AAV), spike-gene-based vaccine candidate demonstrates potent immunogenicity in mouse and non-human primates following a single injection and confers complete protection from SARS-CoV-2 challenge in macaques. Peak neutralizing antibody titers are sustained at 1 year and complemented by functional memory T cell responses. The AAVCOVID vector has no relevant pre-existing immunity in humans and does not elicit cross-reactivity to common AAVs used in gene therapy. Vector genome persistence and expression wanes following injection. The single low-dose requirement, high-yield manufacturability, and 1-month stability for storage at room temperature may make this technology well suited to support effective immunization campaigns for emerging pathogens on a global scale.
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http://dx.doi.org/10.1016/j.chom.2021.08.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8346325PMC
September 2021

CD209L/L-SIGN and CD209/DC-SIGN Act as Receptors for SARS-CoV-2.

ACS Cent Sci 2021 Jul 30;7(7):1156-1165. Epub 2021 Jun 30.

Department of Pathology, School of Medicine, Boston University Medical Campus, Boston, Massachusetts 02118, United States.

As the COVID-19 pandemic continues to spread, investigating the processes underlying the interactions between SARS-CoV-2 and its hosts is of high importance. Here, we report the identification of CD209L/L-SIGN and the related protein CD209/DC-SIGN as receptors capable of mediating SARS-CoV-2 entry into human cells. Immunofluorescence staining of human tissues revealed prominent expression of CD209L in the lung and kidney epithelia and endothelia. Multiple biochemical assays using a purified recombinant SARS-CoV-2 spike receptor-binding domain (S-RBD) or S1 encompassing both N termal domain and RBD and ectopically expressed CD209L and CD209 revealed that CD209L and CD209 interact with S-RBD. CD209L contains two -glycosylation sequons, at sites N92 and N361, but we determined that only site N92 is occupied. Removal of the -glycosylation at this site enhances the binding of S-RBD with CD209L. CD209L also interacts with ACE2, suggesting a role for heterodimerization of CD209L and ACE2 in SARS-CoV-2 entry and infection in cell types where both are present. Furthermore, we demonstrate that human endothelial cells are permissive to SARS-CoV-2 infection, and interference with CD209L activity by a knockdown strategy or with soluble CD209L inhibits virus entry. Our observations demonstrate that CD209L and CD209 serve as alternative receptors for SARS-CoV-2 in disease-relevant cell types, including the vascular system. This property is particularly important in tissues where ACE2 has low expression or is absent and may have implications for antiviral drug development.
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http://dx.doi.org/10.1021/acscentsci.0c01537DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8265543PMC
July 2021

Memory B cell repertoire for recognition of evolving SARS-CoV-2 spike.

Cell 2021 Sep 23;184(19):4969-4980.e15. Epub 2021 Jul 23.

Department of Data Science, Dana-Farber Cancer Institute, Boston, MA 02215, USA.

Memory B cell reserves can generate protective antibodies against repeated SARS-CoV-2 infections, but with unknown reach from original infection to antigenically drifted variants. We charted memory B cell receptor-encoded antibodies from 19 COVID-19 convalescent subjects against SARS-CoV-2 spike (S) and found seven major antibody competition groups against epitopes recurrently targeted across individuals. Inclusion of published and newly determined structures of antibody-S complexes identified corresponding epitopic regions. Group assignment correlated with cross-CoV-reactivity breadth, neutralization potency, and convergent antibody signatures. Although emerging SARS-CoV-2 variants of concern escaped binding by many members of the groups associated with the most potent neutralizing activity, some antibodies in each of those groups retained affinity-suggesting that otherwise redundant components of a primary immune response are important for durable protection from evolving pathogens. Our results furnish a global atlas of S-specific memory B cell repertoires and illustrate properties driving viral escape and conferring robustness against emerging variants.
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http://dx.doi.org/10.1016/j.cell.2021.07.025DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8299219PMC
September 2021

In vitro and in vivo functions of SARS-CoV-2 infection-enhancing and neutralizing antibodies.

Cell 2021 08 18;184(16):4203-4219.e32. Epub 2021 Jun 18.

Duke Human Vaccine Institute, Duke University School of Medicine, Durham, NC 27710, USA; Department of Medicine, Duke University School of Medicine, Durham, NC 27710, USA.

SARS-CoV-2-neutralizing antibodies (NAbs) protect against COVID-19. A concern regarding SARS-CoV-2 antibodies is whether they mediate disease enhancement. Here, we isolated NAbs against the receptor-binding domain (RBD) or the N-terminal domain (NTD) of SARS-CoV-2 spike from individuals with acute or convalescent SARS-CoV-2 or a history of SARS-CoV infection. Cryo-electron microscopy of RBD and NTD antibodies demonstrated function-specific modes of binding. Select RBD NAbs also demonstrated Fc receptor-γ (FcγR)-mediated enhancement of virus infection in vitro, while five non-neutralizing NTD antibodies mediated FcγR-independent in vitro infection enhancement. However, both types of infection-enhancing antibodies protected from SARS-CoV-2 replication in monkeys and mice. Three of 46 monkeys infused with enhancing antibodies had higher lung inflammation scores compared to controls. One monkey had alveolar edema and elevated bronchoalveolar lavage inflammatory cytokines. Thus, while in vitro antibody-enhanced infection does not necessarily herald enhanced infection in vivo, increased lung inflammation can rarely occur in SARS-CoV-2 antibody-infused macaques.
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http://dx.doi.org/10.1016/j.cell.2021.06.021DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8232969PMC
August 2021

Rapid generation of potent antibodies by autonomous hypermutation in yeast.

Nat Chem Biol 2021 Jun 24. Epub 2021 Jun 24.

Department of Biomedical Engineering, University of California, Irvine, CA, USA.

The predominant approach for antibody generation remains animal immunization, which can yield exceptionally selective and potent antibody clones owing to the powerful evolutionary process of somatic hypermutation. However, animal immunization is inherently slow, not always accessible and poorly compatible with many antigens. Here, we describe 'autonomous hypermutation yeast surface display' (AHEAD), a synthetic recombinant antibody generation technology that imitates somatic hypermutation inside engineered yeast. By encoding antibody fragments on an error-prone orthogonal DNA replication system, surface-displayed antibody repertoires continuously mutate through simple cycles of yeast culturing and enrichment for antigen binding to produce high-affinity clones in as little as two weeks. We applied AHEAD to generate potent nanobodies against the SARS-CoV-2 S glycoprotein, a G-protein-coupled receptor and other targets, offering a template for streamlined antibody generation at large.
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http://dx.doi.org/10.1038/s41589-021-00832-4DOI Listing
June 2021

Alum:CpG adjuvant enables SARS-CoV-2 RBD-induced protection in aged mice and synergistic activation of human elder type 1 immunity.

bioRxiv 2021 May 21. Epub 2021 May 21.

Global deployment of vaccines that can provide protection across several age groups is still urgently needed to end the COVID-19 pandemic especially for low- and middle-income countries. While vaccines against SARS-CoV-2 based on mRNA and adenoviral-vector technologies have been rapidly developed, additional practical and scalable SARS-CoV-2 vaccines are needed to meet global demand. In this context, protein subunit vaccines formulated with appropriate adjuvants represent a promising approach to address this urgent need. Receptor-binding domain (RBD) is a key target of neutralizing antibodies (Abs) but is poorly immunogenic. We therefore compared pattern recognition receptor (PRR) agonists, including those activating STING, TLR3, TLR4 and TLR9, alone or formulated with aluminum hydroxide (AH), and benchmarked them to AS01B and AS03-like emulsion-based adjuvants for their potential to enhance RBD immunogenicity in young and aged mice. We found that the AH and CpG adjuvant formulation (AH:CpG) demonstrated the highest enhancement of anti-RBD neutralizing Ab titers in both age groups (∼80-fold over AH), and protected aged mice from the SARS-CoV-2 challenge. Notably, AH:CpG-adjuvanted RBD vaccine elicited neutralizing Abs against both wild-type SARS-CoV-2 and B.1.351 variant at serum concentrations comparable to those induced by the authorized mRNA BNT162b2 vaccine. AH:CpG induced similar cytokine and chemokine gene enrichment patterns in the draining lymph nodes of both young adult and aged mice and synergistically enhanced cytokine and chemokine production in human young adult and elderly mononuclear cells. These data support further development of AH:CpG-adjuvanted RBD as an affordable vaccine that may be effective across multiple age groups.

One Sentence Summary: Alum and CpG enhance SARS-CoV-2 RBD protective immunity, variant neutralization in aged mice and Th1-polarizing cytokine production by human elder leukocytes.
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http://dx.doi.org/10.1101/2021.05.20.444848DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8142652PMC
May 2021

Moving the Needle on Global Surgery Education in the US.

J Surg Educ 2021 May 5. Epub 2021 May 5.

Global Surgery Student Alliance, Boston, Massachusetts; Harvard Medical School, Boston, Massachusetts.

Objective: Interest in global surgery continues to increase among students and trainees in the U.S. pursuing fields that provide perioperative care, including surgery, anesthesia, and OB/GYN. While some students and trainees successfully engage in global surgery-related research, advocacy, and clinical work, many individuals face gaps in global surgery education and opportunities. A lack of access to mentorship and resources can limit engagement with the shift from pursuing clinically-oriented experiences, such as short-term trips, to focusing on long-term models emphasizing equity. To address these challenges, motivated students and trainees have formed networks of future global surgery providers.

Design: Within the U.S., the Global Surgery Student Alliance (GSSA) has constructed a network reaching students and trainees at 75 medical schools. GSSA is able to connect American students and trainees with resources and mentors, as well as emphasizing the importance of equitable engagement in the global surgery field. GSSA also serves as the National Working Group for the International Student Surgical Network (InciSioN).

Results: Since launching in January 2017, GSSA has constructed a national leadership team that supports chapters at individual medical schools in addition to hosting nationwide events and producing resources. Using the global surgery education needs identified in the NextGen study, GSSA has authored toolkits aimed at guiding students towards ethical and equitable opportunities to engage in global surgery research, education, and advocacy. GSSA also hosts numerous events to help students prepare for potential careers in global surgery, including annual national symposia and frequent webinars. Additionally, GSSA has created a freely accessible database to connect students with peers and mentors within global surgery worldwide.

Conclusion: Students have created a national organization that connects future perioperative care providers with resources to engage in equitable global surgery advocacy, education, and research. GSSA helps bridge the gaps between interest, opportunity, and equity in global surgery work.
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http://dx.doi.org/10.1016/j.jsurg.2021.04.006DOI Listing
May 2021

The Prolyl-tRNA Synthetase Inhibitor Halofuginone Inhibits SARS-CoV-2 Infection.

bioRxiv 2021 Mar 26. Epub 2021 Mar 26.

We identify the prolyl-tRNA synthetase (PRS) inhibitor halofuginone , a compound in clinical trials for anti-fibrotic and anti-inflammatory applications , as a potent inhibitor of SARS-CoV-2 infection and replication. The interaction of SARS-CoV-2 spike protein with cell surface heparan sulfate (HS) promotes viral entry . We find that halofuginone reduces HS biosynthesis, thereby reducing spike protein binding, SARS-CoV-2 pseudotyped virus, and authentic SARS-CoV-2 infection. Halofuginone also potently suppresses SARS-CoV-2 replication post-entry and is 1,000-fold more potent than Remdesivir . Inhibition of HS biosynthesis and SARS-CoV-2 infection depends on specific inhibition of PRS, possibly due to translational suppression of proline-rich proteins. We find that pp1a and pp1ab polyproteins of SARS-CoV-2, as well as several HS proteoglycans, are proline-rich, which may make them particularly vulnerable to halofuginone's translational suppression. Halofuginone is orally bioavailable, has been evaluated in a phase I clinical trial in humans and distributes to SARS-CoV-2 target organs, including the lung, making it a near-term clinical trial candidate for the treatment of COVID-19.
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http://dx.doi.org/10.1101/2021.03.22.436522DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8010724PMC
March 2021

Memory B cell repertoire for recognition of evolving SARS-CoV-2 spike.

bioRxiv 2021 Mar 10. Epub 2021 Mar 10.

Department of Medicine, Division of Allergy and Immunology, Division of Genetics, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.

Memory B cell reserves can generate protective antibodies against repeated SARS-CoV-2 infections, but with an unknown reach from original infection to antigenically drifted variants. We charted memory B cell receptor-encoded monoclonal antibodies (mAbs) from 19 COVID-19 convalescent subjects against SARS-CoV-2 spike (S) and found 7 major mAb competition groups against epitopes recurrently targeted across individuals. Inclusion of published and newly determined structures of mAb-S complexes identified corresponding epitopic regions. Group assignment correlated with cross-CoV-reactivity breadth, neutralization potency, and convergent antibody signatures. mAbs that competed for binding the original S isolate bound differentially to S variants, suggesting the protective importance of otherwise-redundant recognition. The results furnish a global atlas of the S-specific memory B cell repertoire and illustrate properties conferring robustness against emerging SARS-CoV-2 variants.
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http://dx.doi.org/10.1101/2021.03.10.434840DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7987022PMC
March 2021

Rationally designed immunogens enable immune focusing to the SARS-CoV-2 receptor binding motif.

bioRxiv 2021 Jul 9. Epub 2021 Jul 9.

Eliciting antibodies to surface-exposed viral glycoproteins can lead to protective responses that ultimately control and prevent future infections. Targeting functionally conserved epitopes may help reduce the likelihood of viral escape and aid in preventing the spread of related viruses with pandemic potential. One such functionally conserved viral epitope is the site to which a receptor must bind to facilitate viral entry. Here, we leveraged rational immunogen design strategies to focus humoral responses to the receptor binding motif (RBM) on the SARS-CoV-2 spike. Using glycan engineering and epitope scaffolding, we find an improved targeting of the serum response to the RBM in context of SARS-CoV-2 spike imprinting. Furthermore, we observed a robust SARS-CoV-2-neutralizing serum response with increased potency against related sarbecoviruses, SARS-CoV, WIV1-CoV, RaTG13-CoV, and SHC014-CoV. Thus, RBM focusing is a promising strategy to elicit breadth across emerging sarbecoviruses and represents an adaptable design approach for targeting conserved epitopes on other viral glycoproteins.

One Sentence Summary: SARS-CoV-2 immune focusing with engineered immunogens.
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http://dx.doi.org/10.1101/2021.03.15.435440DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7987010PMC
July 2021

Multiple SARS-CoV-2 variants escape neutralization by vaccine-induced humoral immunity.

Cell 2021 04 12;184(9):2372-2383.e9. Epub 2021 Mar 12.

Ragon Institute of MGH, MIT, and Harvard, Cambridge, MA 02139, USA. Electronic address:

Vaccination elicits immune responses capable of potently neutralizing SARS-CoV-2. However, ongoing surveillance has revealed the emergence of variants harboring mutations in spike, the main target of neutralizing antibodies. To understand the impact of these variants, we evaluated the neutralization potency of 99 individuals that received one or two doses of either BNT162b2 or mRNA-1273 vaccines against pseudoviruses representing 10 globally circulating strains of SARS-CoV-2. Five of the 10 pseudoviruses, harboring receptor-binding domain mutations, including K417N/T, E484K, and N501Y, were highly resistant to neutralization. Cross-neutralization of B.1.351 variants was comparable to SARS-CoV and bat-derived WIV1-CoV, suggesting that a relatively small number of mutations can mediate potent escape from vaccine responses. While the clinical impact of neutralization resistance remains uncertain, these results highlight the potential for variants to escape from neutralizing humoral immunity and emphasize the need to develop broadly protective interventions against the evolving pandemic.
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http://dx.doi.org/10.1016/j.cell.2021.03.013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7953441PMC
April 2021

Multiple SARS-CoV-2 variants escape neutralization by vaccine-induced humoral immunity.

medRxiv 2021 Mar 12. Epub 2021 Mar 12.

Ragon Institute of MGH, MIT, and Harvard, Cambridge, MA, 02139, USA.

Vaccination elicits immune responses capable of potently neutralizing SARS-CoV-2. However, ongoing surveillance has revealed the emergence of variants harboring mutations in spike, the main target of neutralizing antibodies. To understand the impact of these variants, we evaluated the neutralization potency of 99 individuals that received one or two doses of either BNT162b2 or mRNA-1273 vaccines against pseudoviruses representing 10 globally circulating strains of SARS-CoV-2. Five of the 10 pseudoviruses, harboring receptor-binding domain mutations, including K417N/T, E484K, and N501Y, were highly resistant to neutralization. Crossneutralization of B.1.351 variants was comparable to SARS-CoV and bat-derived WIV1-CoV, suggesting that a relatively small number of mutations can mediate potent escape from vaccine responses. While the clinical impact of neutralization resistance remains uncertain, these results highlight the potential for variants to escape from neutralizing humoral immunity and emphasize the need to develop broadly protective interventions against the evolving pandemic.
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http://dx.doi.org/10.1101/2021.02.14.21251704DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7899476PMC
March 2021

Naive human B cells engage the receptor binding domain of SARS-CoV-2, variants of concern, and related sarbecoviruses.

bioRxiv 2021 Jul 9. Epub 2021 Jul 9.

Ragon Institute of MGH, MIT and Harvard, Cambridge, MA, 02139, USA.

Exposure to a pathogen elicits an adaptive immune response aimed to control and eradicate. Interrogating the abundance and specificity of the naive B cell repertoire contributes to understanding how to potentially elicit protective responses. Here, we isolated naive B cells from 8 seronegative human donors targeting the SARS-CoV-2 receptor-binding domain (RBD). Single B cell analysis showed diverse gene usage with no restricted complementarity determining region lengths. We show that recombinant antibodies engage SARS-CoV-2 RBD, circulating variants, and pre-emergent coronaviruses. Representative antibodies signal in a B cell activation assay and can be affinity matured through directed evolution. Structural analysis of a naive antibody in complex with spike shows a conserved mode of recognition shared with infection-induced antibodies. Lastly, both naive and affinity-matured antibodies can neutralize SARS-CoV-2. Understanding the naive repertoire may inform potential responses recognizing variants or emerging coronaviruses enabling the development of pan-coronavirus vaccines aimed at engaging germline responses.
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http://dx.doi.org/10.1101/2021.02.02.429458DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7885909PMC
July 2021

The functions of SARS-CoV-2 neutralizing and infection-enhancing antibodies in vitro and in mice and nonhuman primates.

bioRxiv 2021 Feb 18. Epub 2021 Feb 18.

SARS-CoV-2 neutralizing antibodies (NAbs) protect against COVID-19. A concern regarding SARS-CoV-2 antibodies is whether they mediate disease enhancement. Here, we isolated NAbs against the receptor-binding domain (RBD) and the N-terminal domain (NTD) of SARS-CoV-2 spike from individuals with acute or convalescent SARS-CoV-2 or a history of SARS-CoV-1 infection. Cryo-electron microscopy of RBD and NTD antibodies demonstrated function-specific modes of binding. Select RBD NAbs also demonstrated Fc receptor-γ (FcγR)-mediated enhancement of virus infection , while five non-neutralizing NTD antibodies mediated FcγR-independent infection enhancement. However, both types of infection-enhancing antibodies protected from SARS-CoV-2 replication in monkeys and mice. Nonetheless, three of 31 monkeys infused with enhancing antibodies had higher lung inflammation scores compared to controls. One monkey had alveolar edema and elevated bronchoalveolar lavage inflammatory cytokines. Thus, while antibody-enhanced infection does not necessarily herald enhanced infection , increased lung inflammation can occur in SARS-CoV-2 antibody-infused macaques.
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http://dx.doi.org/10.1101/2020.12.31.424729DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7805451PMC
February 2021

Immunogenicity of an AAV-based, room-temperature stable, single dose COVID-19 vaccine in mice and non-human primates.

bioRxiv 2021 Jan 19. Epub 2021 Jan 19.

The SARS-CoV-2 pandemic has affected more than 70 million people worldwide and resulted in over 1.5 million deaths. A broad deployment of effective immunization campaigns to achieve population immunity at global scale will depend on the biological and logistical attributes of the vaccine. Here, two adeno-associated viral (AAV)-based vaccine candidates demonstrate potent immunogenicity in mouse and nonhuman primates following a single injection. Peak neutralizing antibody titers remain sustained at 5 months and are complemented by functional memory T-cells responses. The AAVrh32.33 capsid of the AAVCOVID vaccine is an engineered AAV to which no relevant pre-existing immunity exists in humans. Moreover, the vaccine is stable at room temperature for at least one month and is produced at high yields using established commercial manufacturing processes in the gene therapy industry. Thus, this methodology holds as a very promising single dose, thermostable vaccine platform well-suited to address emerging pathogens on a global scale.
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http://dx.doi.org/10.1101/2021.01.05.422952DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7805441PMC
January 2021

COVID-19-neutralizing antibodies predict disease severity and survival.

Cell 2021 01 15;184(2):476-488.e11. Epub 2020 Dec 15.

Ragon Institute of MGH, MIT, and Harvard, Cambridge, MA 02139, USA. Electronic address:

Coronavirus disease 2019 (COVID-19) exhibits variable symptom severity ranging from asymptomatic to life-threatening, yet the relationship between severity and the humoral immune response is poorly understood. We examined antibody responses in 113 COVID-19 patients and found that severe cases resulting in intubation or death exhibited increased inflammatory markers, lymphopenia, pro-inflammatory cytokines, and high anti-receptor binding domain (RBD) antibody levels. Although anti-RBD immunoglobulin G (IgG) levels generally correlated with neutralization titer, quantitation of neutralization potency revealed that high potency was a predictor of survival. In addition to neutralization of wild-type SARS-CoV-2, patient sera were also able to neutralize the recently emerged SARS-CoV-2 mutant D614G, suggesting cross-protection from reinfection by either strain. However, SARS-CoV-2 sera generally lacked cross-neutralization to a highly homologous pre-emergent bat coronavirus, WIV1-CoV, which has not yet crossed the species barrier. These results highlight the importance of neutralizing humoral immunity on disease progression and the need to develop broadly protective interventions to prevent future coronavirus pandemics.
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http://dx.doi.org/10.1016/j.cell.2020.12.015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7837114PMC
January 2021

Assessment of Maternal and Neonatal SARS-CoV-2 Viral Load, Transplacental Antibody Transfer, and Placental Pathology in Pregnancies During the COVID-19 Pandemic.

JAMA Netw Open 2020 12 1;3(12):e2030455. Epub 2020 Dec 1.

Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts.

Importance: Biological data are lacking with respect to risk of vertical transmission and mechanisms of fetoplacental protection in maternal severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection.

Objective: To quantify SARS-CoV-2 viral load in maternal and neonatal biofluids, transplacental passage of anti-SARS-CoV-2 antibody, and incidence of fetoplacental infection.

Design, Setting, And Participants: This cohort study was conducted among pregnant women presenting for care at 3 tertiary care centers in Boston, Massachusetts. Women with reverse transcription-polymerase chain reaction (RT-PCR) results positive for SARS-CoV-2 were recruited from April 2 to June 13, 2020, and follow-up occurred through July 10, 2020. Contemporaneous participants without SARS-CoV-2 infection were enrolled as a convenience sample from pregnant women with RT-PCR results negative for SARS-CoV-2.

Exposures: SARS-CoV-2 infection in pregnancy, defined by nasopharyngeal swab RT-PCR.

Main Outcomes And Measures: The main outcomes were SARS-CoV-2 viral load in maternal plasma or respiratory fluids and umbilical cord plasma, quantification of anti-SARS-CoV-2 antibodies in maternal and cord plasma, and presence of SARS-CoV-2 RNA in the placenta.

Results: Among 127 pregnant women enrolled, 64 with RT-PCR results positive for SARS-CoV-2 (mean [SD] age, 31.6 [5.6] years) and 63 with RT-PCR results negative for SARS-CoV-2 (mean [SD] age, 33.9 [5.4] years) provided samples for analysis. Of women with SARS-CoV-2 infection, 23 (36%) were asymptomatic, 22 (34%) had mild disease, 7 (11%) had moderate disease, 10 (16%) had severe disease, and 2 (3%) had critical disease. In viral load analyses among 107 women, there was no detectable viremia in maternal or cord blood and no evidence of vertical transmission. Among 77 neonates tested in whom SARS-CoV-2 antibodies were quantified in cord blood, 1 had detectable immunoglobuilin M to nucleocapsid. Among 88 placentas tested, SARS-CoV-2 RNA was not detected in any. In antibody analyses among 37 women with SARS-CoV-2 infection, anti-receptor binding domain immunoglobin G was detected in 24 women (65%) and anti-nucleocapsid was detected in 26 women (70%). Mother-to-neonate transfer of anti-SARS-CoV-2 antibodies was significantly lower than transfer of anti-influenza hemagglutinin A antibodies (mean [SD] cord-to-maternal ratio: anti-receptor binding domain immunoglobin G, 0.72 [0.57]; anti-nucleocapsid, 0.74 [0.44]; anti-influenza, 1.44 [0.80]; P < .001). Nonoverlapping placental expression of SARS-CoV-2 receptors angiotensin-converting enzyme 2 and transmembrane serine protease 2 was noted.

Conclusions And Relevance: In this cohort study, there was no evidence of placental infection or definitive vertical transmission of SARS-CoV-2. Transplacental transfer of anti-SARS-CoV-2 antibodies was inefficient. Lack of viremia and reduced coexpression and colocalization of placental angiotensin-converting enzyme 2 and transmembrane serine protease 2 may serve as protective mechanisms against vertical transmission.
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http://dx.doi.org/10.1001/jamanetworkopen.2020.30455DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7756241PMC
December 2020

Engineered receptor binding domain immunogens elicit pan-sarbecovirus neutralizing antibodies outside the receptor binding motif.

bioRxiv 2021 Jun 29. Epub 2021 Jun 29.

Effective countermeasures are needed against emerging coronaviruses of pandemic potential, similar to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Designing immunogens that elicit broadly neutralizing antibodies to conserved viral epitopes on the major surface glycoprotein, spike, such as the receptor binding domain (RBD) is one potential approach. Here, we report the generation of homotrimeric RBD immunogens from different sarbecoviruses using a stabilized, immune-silent trimerization tag. In mice, we find that a cocktail of these homotrimeric sarbecovirus RBDs elicits antibodies to conserved viral epitopes outside of the ACE2 receptor binding motif (RBM). Importantly, these responses neutralize all sarbecovirus components even in context of prior SARS-CoV-2 imprinting. We further show that a substantial fraction of the neutralizing antibodies elicited after vaccination in humans also engages non-RBM epitopes on the RBD. Collectively, our results suggest a strategy for eliciting broadly neutralizing responses leading to a pan-sarbecovirus vaccine.

Author Summary: Immunity to SARS-CoV-2 in the human population will be widespread due to natural infection and vaccination. However, another novel coronavirus will likely emerge in the future and may cause a subsequent pandemic. Humoral responses induced by SARS-CoV-2 infection and vaccination provide limited protection against even closely related coronaviruses. We show immunization with a cocktail of trimeric coronavirus receptor binding domains induces a neutralizing antibody response that is broadened to related coronaviruses with pandemic potential. Importantly, this broadening occurs in context of an initial imprinted SARS-CoV-2 spike immunization showing that preexisting immunity can be expanded to recognize other related coronaviruses. Our immunogens focused the serum antibody response to conserved epitopes on the receptor binding domain outside of the ACE2 receptor binding motif; this contrasts with current SARS-CoV-2 therapeutic antibodies, which predominantly target the receptor binding motif.
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http://dx.doi.org/10.1101/2020.12.07.415216DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7743097PMC
June 2021

Rapid generation of potent antibodies by autonomous hypermutation in yeast.

bioRxiv 2020 Nov 11. Epub 2020 Nov 11.

The predominant approach for antibody generation remains animal immunization, which can yield exceptionally selective and potent antibody clones owing to the powerful evolutionary process of somatic hypermutation. However, animal immunization is inherently slow, has poor compatibility with certain antigens ( . ., integral membrane proteins), and suffers from self-tolerance and immunodominance, which limit the functional spectrum of antibodies that can be obtained. Here, we describe A utonomous H ypermutation y E ast surf A ce D isplay (AHEAD), a synthetic recombinant antibody generation technology that imitates somatic hypermutation inside engineered yeast. In AHEAD, antibody fragments are encoded on an error-prone orthogonal DNA replication system, resulting in populations that continuously mutate surface-displayed antibody repertoires. Simple cycles of yeast culturing and enrichment for antigen binding drive the evolution of high-affinity antibody clones in a readily parallelizable process that takes as little as 2 weeks. We applied AHEAD to generate nanobodies against the SARS-CoV-2 S glycoprotein, a GPCR, and other targets. The SARS-CoV-2 nanobodies, concurrently evolved from an open-source naïve nanobody library in 8 independent experiments, reached subnanomolar affinities through the sequential fixation of multiple mutations over 3-8 AHEAD cycles that saw ∼580-fold and ∼925-fold improvements in binding affinities and pseudovirus neutralization potencies, respectively. These experiments highlight the defining speed, parallelizability, and effectiveness of AHEAD and provide a template for streamlined antibody generation at large with salient utility in rapid response to current and future viral outbreaks.
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http://dx.doi.org/10.1101/2020.11.11.378778DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7668743PMC
November 2020

Quick COVID-19 Healers Sustain Anti-SARS-CoV-2 Antibody Production.

Cell 2020 12 3;183(6):1496-1507.e16. Epub 2020 Nov 3.

Department of Medicine, Division of Allergy and Immunology, Division of Genetics, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA; Massachusetts Consortium on Pathogen Readiness, Boston, MA 02115, USA. Electronic address:

Antibodies are key immune effectors that confer protection against pathogenic threats. The nature and longevity of the antibody response to SARS-CoV-2 infection are not well defined. We charted longitudinal antibody responses to SARS-CoV-2 in 92 subjects after symptomatic COVID-19. Antibody responses to SARS-CoV-2 are unimodally distributed over a broad range, with symptom severity correlating directly with virus-specific antibody magnitude. Seventy-six subjects followed longitudinally to ∼100 days demonstrated marked heterogeneity in antibody duration dynamics. Virus-specific IgG decayed substantially in most individuals, whereas a distinct subset had stable or increasing antibody levels in the same time frame despite similar initial antibody magnitudes. These individuals with increasing responses recovered rapidly from symptomatic COVID-19 disease, harbored increased somatic mutations in virus-specific memory B cell antibody genes, and had persistent higher frequencies of previously activated CD4 T cells. These findings illuminate an efficient immune phenotype that connects symptom clearance speed to differential antibody durability dynamics.
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http://dx.doi.org/10.1016/j.cell.2020.10.051DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7608032PMC
December 2020

COVID-19 neutralizing antibodies predict disease severity and survival.

medRxiv 2020 Oct 20. Epub 2020 Oct 20.

Ragon Institute of MGH, MIT, and Harvard, Cambridge, MA.

COVID-19 exhibits variable symptom severity ranging from asymptomatic to life-threatening, yet the relationship between severity and the humoral immune response is poorly understood. We examined antibody responses in 113 COVID-19 patients and found that severe cases resulting in intubation or death exhibited increased inflammatory markers, lymphopenia, and high anti-RBD antibody levels. While anti-RBD IgG levels generally correlated with neutralization titer, quantitation of neutralization potency revealed that high potency was a predictor of survival. In addition to neutralization of wild-type SARS-CoV-2, patient sera were also able to neutralize the recently emerged SARS-CoV-2 mutant D614G, suggesting protection from reinfection by this strain. However, SARS-CoV-2 sera was unable to cross-neutralize a highly-homologous pre-emergent bat coronavirus, WIV1-CoV, that has not yet crossed the species barrier. These results highlight the importance of neutralizing humoral immunity on disease progression and the need to develop broadly protective interventions to prevent future coronavirus pandemics.
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http://dx.doi.org/10.1101/2020.10.15.20213512DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7587842PMC
October 2020

Persistence and decay of human antibody responses to the receptor binding domain of SARS-CoV-2 spike protein in COVID-19 patients.

Sci Immunol 2020 10;5(52)

Ragon Institute of MGH, MIT, and Harvard, Cambridge, MA, USA.

We measured plasma and/or serum antibody responses to the receptor-binding domain (RBD) of the spike (S) protein of SARS-CoV-2 in 343 North American patients infected with SARS-CoV-2 (of which 93% required hospitalization) up to 122 days after symptom onset and compared them to responses in 1548 individuals whose blood samples were obtained prior to the pandemic. After setting seropositivity thresholds for perfect specificity (100%), we estimated sensitivities of 95% for IgG, 90% for IgA, and 81% for IgM for detecting infected individuals between 15 and 28 days after symptom onset. While the median time to seroconversion was nearly 12 days across all three isotypes tested, IgA and IgM antibodies against RBD were short-lived with median times to seroreversion of 71 and 49 days after symptom onset. In contrast, anti-RBD IgG responses decayed slowly through 90 days with only 3 seropositive individuals seroreverting within this time period. IgG antibodies to SARS-CoV-2 RBD were strongly correlated with anti-S neutralizing antibody titers, which demonstrated little to no decrease over 75 days since symptom onset. We observed no cross-reactivity of the SARS-CoV-2 RBD-targeted antibodies with other widely circulating coronaviruses (HKU1, 229 E, OC43, NL63). These data suggest that RBD-targeted antibodies are excellent markers of previous and recent infection, that differential isotype measurements can help distinguish between recent and older infections, and that IgG responses persist over the first few months after infection and are highly correlated with neutralizing antibodies.
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http://dx.doi.org/10.1126/sciimmunol.abe0367DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7857394PMC
October 2020

SARS-CoV-2 Infection Depends on Cellular Heparan Sulfate and ACE2.

Cell 2020 11 14;183(4):1043-1057.e15. Epub 2020 Sep 14.

Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093, USA; Glycobiology Research and Training Center, University of California, San Diego, La Jolla, CA 92093, USA.

We show that SARS-CoV-2 spike protein interacts with both cellular heparan sulfate and angiotensin-converting enzyme 2 (ACE2) through its receptor-binding domain (RBD). Docking studies suggest a heparin/heparan sulfate-binding site adjacent to the ACE2-binding site. Both ACE2 and heparin can bind independently to spike protein in vitro, and a ternary complex can be generated using heparin as a scaffold. Electron micrographs of spike protein suggests that heparin enhances the open conformation of the RBD that binds ACE2. On cells, spike protein binding depends on both heparan sulfate and ACE2. Unfractionated heparin, non-anticoagulant heparin, heparin lyases, and lung heparan sulfate potently block spike protein binding and/or infection by pseudotyped virus and authentic SARS-CoV-2 virus. We suggest a model in which viral attachment and infection involves heparan sulfate-dependent enhancement of binding to ACE2. Manipulation of heparan sulfate or inhibition of viral adhesion by exogenous heparin presents new therapeutic opportunities.
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http://dx.doi.org/10.1016/j.cell.2020.09.033DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7489987PMC
November 2020

Ultrasensitive high-resolution profiling of early seroconversion in patients with COVID-19.

Nat Biomed Eng 2020 12 18;4(12):1180-1187. Epub 2020 Sep 18.

Department of Pathology, Brigham and Women's Hospital, Boston, MA, USA.

Sensitive assays are essential for the accurate identification of individuals infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Here, we report a multiplexed assay for the fluorescence-based detection of seroconversion in infected individuals from less than 1 µl of blood, and as early as the day of the first positive nucleic acid test after symptom onset. The assay uses dye-encoded antigen-coated beads to quantify the levels of immunoglobulin G (IgG), IgM and IgA antibodies against four SARS-CoV-2 antigens. A logistic regression model trained using samples collected during the pandemic and samples collected from healthy individuals and patients with respiratory infections before the first outbreak of coronavirus disease 2019 (COVID-19) was 99% accurate in the detection of seroconversion in a blinded validation cohort of samples collected before the pandemic and from patients with COVID-19 five or more days after a positive nasopharyngeal test by PCR with reverse transcription. The high-throughput serological profiling of patients with COVID-19 allows for the interrogation of interactions between antibody isotypes and viral proteins, and should help us to understand the heterogeneity of clinical presentations.
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http://dx.doi.org/10.1038/s41551-020-00611-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7498988PMC
December 2020

High Seroprevalence of Anti-SARS-CoV-2 Antibodies in Chelsea, Massachusetts.

J Infect Dis 2020 11;222(12):1955-1959

Department of Pathology, Massachusetts General Hospital, Boston, Massachusetts, USA.

SARS-CoV-2 antibody testing allows quantitative determination of disease prevalence, which is especially important in high-risk communities. We performed anonymized convenience sampling of 200 currently asymptomatic residents of Chelsea, the epicenter of COVID-19 illness in Massachusetts, by BioMedomics SARS-CoV-2 combined IgM-IgG point-of-care lateral flow immunoassay. The seroprevalence was 31.5% (17.5% IgM+IgG+, 9.0% IgM+IgG-, and 5.0% IgM-IgG+). Of the 200 participants, 50.5% reported no symptoms in the preceding 4 weeks, of which 24.8% (25/101) were seropositive, and 60% of these were IgM+IgG-. These data are the highest seroprevalence rates observed to date and highlight the significant burden of asymptomatic infection.
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http://dx.doi.org/10.1093/infdis/jiaa579DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7499676PMC
November 2020

Ad26 vaccine protects against SARS-CoV-2 severe clinical disease in hamsters.

Nat Med 2020 11 3;26(11):1694-1700. Epub 2020 Sep 3.

Center for Virology and Vaccine Research, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.

Coronavirus disease 2019 (COVID-19) in humans is often a clinically mild illness, but some individuals develop severe pneumonia, respiratory failure and death. Studies of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in hamsters and nonhuman primates have generally reported mild clinical disease, and preclinical SARS-CoV-2 vaccine studies have demonstrated reduction of viral replication in the upper and lower respiratory tracts in nonhuman primates. Here we show that high-dose intranasal SARS-CoV-2 infection in hamsters results in severe clinical disease, including high levels of virus replication in tissues, extensive pneumonia, weight loss and mortality in a subset of animals. A single immunization with an adenovirus serotype 26 vector-based vaccine expressing a stabilized SARS-CoV-2 spike protein elicited binding and neutralizing antibody responses and protected against SARS-CoV-2-induced weight loss, pneumonia and mortality. These data demonstrate vaccine protection against SARS-CoV-2 clinical disease. This model should prove useful for preclinical studies of SARS-CoV-2 vaccines, therapeutics and pathogenesis.
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http://dx.doi.org/10.1038/s41591-020-1070-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7671939PMC
November 2020

Loss of Bcl-6-Expressing T Follicular Helper Cells and Germinal Centers in COVID-19.

Cell 2020 10 19;183(1):143-157.e13. Epub 2020 Aug 19.

Ragon Institute of MGH, MIT and Harvard, Cambridge, MA 02139, USA.

Humoral responses in coronavirus disease 2019 (COVID-19) are often of limited durability, as seen with other human coronavirus epidemics. To address the underlying etiology, we examined post mortem thoracic lymph nodes and spleens in acute SARS-CoV-2 infection and observed the absence of germinal centers and a striking reduction in Bcl-6 germinal center B cells but preservation of AID B cells. Absence of germinal centers correlated with an early specific block in Bcl-6 T cell differentiation together with an increase in T-bet T cells and aberrant extra-follicular TNF-α accumulation. Parallel peripheral blood studies revealed loss of transitional and follicular B cells in severe disease and accumulation of SARS-CoV-2-specific "disease-related" B cell populations. These data identify defective Bcl-6 T cell generation and dysregulated humoral immune induction early in COVID-19 disease, providing a mechanistic explanation for the limited durability of antibody responses in coronavirus infections, and suggest that achieving herd immunity through natural infection may be difficult.
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http://dx.doi.org/10.1016/j.cell.2020.08.025DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7437499PMC
October 2020
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