Selective SARS-CoV2 BA.2 escape of antibody Fc/Fc-receptor interactions.

The number of mutations in the omicron (B.1.1.529) BA.1 variant of concern led to an unprecedented evasion of vaccine induced immunity. However, despite rise in global infections, severe disease did not increase proportionally and is likely linked to persistent recognition of BA.1 by T cells and non-neutralizing opsonophagocytic antibodies. Yet, the emergence of new sublineage BA.2, which is more transmissible than BA.1 despite relatively preserved neutralizing antibody responses, has raised the possibility that BA.2 may evade other vaccine-induced responses. Here, we comprehensively profiled the BNT162b2 vaccine-induced response to several VOCs, including omicron BA.1 and BA.2. While vaccine-induced immune responses were compromised against both omicron sublineages, vaccine-induced antibody isotype titers, and non-neutralizing Fc effector functions were attenuated to the omicron BA.2 spike compared to BA.1. Conversely, FcγR2a and FcγR2b binding was elevated to BA.2, albeit lower than BA.1 responses, potentially contributing to persistent protection against severity of disease.

Immunogenicity and protective efficacy of GBP510/AS03 vaccine against SARS-CoV-2 delta challenge in rhesus macaques.

Despite the availability of several effective SARS-CoV-2 vaccines, additional vaccines will be required for optimal global vaccination. In this study, we investigate the immunogenicity and protective efficacy of the GBP510 protein subunit vaccine adjuvanted with AS03, which has recently been authorized for marketing in South Korea under the trade name SKYCovioneTM. The antigen in GBP510/AS03 is a two-part recombinant nanoparticle, which displays 60 receptor binding domain (RBD) proteins of SARS-CoV-2 Spike on its surface. In this study we show that GBP510/AS03 induced robust immune responses in rhesus macaques and protected against a high-dose SARS-CoV-2 Delta challenge. We vaccinated macaques with two or three doses of GBP510/AS03 matched to the ancestral Wuhan strain of SARS-CoV-2 or with two doses of GBP510/AS03 matched to the ancestral strain and one dose matched to the Beta strain. Following the challenge with Delta, the vaccinated macaques rapidly controlled the virus in bronchoalveolar lavage and nasal swabs. Binding and neutralizing antibody responses prior to challenge correlated with protection against viral replication postchallenge. These data are consistent with data with this vaccine from the phase 3 clinical trial.

A genetically engineered, stem-cell-derived cellular vaccine.

Despite rapid clinical translation of COVID-19 vaccines in response to the global pandemic, an opportunity remains for vaccine technology innovation to address current limitations and meet challenges of inevitable future pandemics. We describe a universal vaccine cell (UVC) genetically engineered to mimic natural physiological immunity induced upon viral infection of host cells. Cells engineered to express the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike as a representative viral antigen induce robust neutralizing antibodies in immunized non-human primates. Similar titers generated in this established non-human primate (NHP) model have translated into protective human neutralizing antibody levels in SARS-CoV-2-vaccinated individuals. Animals vaccinated with ancestral spike antigens and subsequently challenged with SARS-CoV-2 Delta variant in a heterologous challenge have an approximately 3 log decrease in viral subgenomic RNA in the lungs. This cellular vaccine is designed as a scalable cell line with a modular poly-antigenic payload, allowing for rapid, large-scale clinical manufacturing and use in an evolving viral variant environment.

Durability of Heterologous and Homologous COVID-19 Vaccine Boosts.

Importance: Antibody responses elicited by current messenger RNA (mRNA) COVID-19 vaccines decline rapidly and require repeated boosting. Objective: To evaluate the immunogenicity and durability of heterologous and homologous prime-boost regimens involving the adenovirus vector vaccine Ad26.COV2.S and the mRNA vaccine BNT162b2. Design, Setting, and Participants: In this cohort study at a single clinical site in Boston, Massachusetts, 68 individuals who were vaccinated at least 6 months previously with 2 immunizations of BNT162b2 were boosted with either Ad26.COV2.S or BNT162b2. Enrollment of participants occurred from August 12, 2021, to October 25, 2021, and this study involved 4 months of follow-up. Data analysis was performed from November 2021 to February 2022. Exposures: Participants who were previously vaccinated with BNT162b2 received a boost with either Ad26.COV2.S or BNT162b2. Main Outcomes and Measures: Humoral immune responses were assessed by neutralizing, binding, and functional antibody responses for 16 weeks following the boost. CD8+ and CD4+ T-cell responses were evaluated by intracellular cytokine staining assays. Results: Among 68 participants who were originally vaccinated with BNT162b2 and boosted with Ad26.COV2.S (41 participants; median [range] age, 36 [23-84] years) or BNT162b2 (27 participants; median [range] age, 35 [23-76] years), 56 participants (82%) were female, 7 (10%) were Asian, 4 (6%) were Black, 4 (6%) were Hispanic or Latino, 3 (4%) were more than 1 race, and 53 (78%) were White. Both vaccines were found to be associated with increased humoral and cellular immune responses, including against SARS-CoV-2 variants of concern. BNT162b2 boosting was associated with a rapid increase of Omicron neutralizing antibodies that peaked at a median (IQR) titer of 1018 (699-1646) at week 2 and declined by 6.9-fold to a median (IQR) titer of 148 (95-266) by week 16. Ad26.COV2.S boosting was associated with increased Omicron neutralizing antibodies titers that peaked at a median (IQR) of 859 (467-1838) week 4 and declined by 2.1-fold to a median (IQR) of 403 (208-1130) by week 16. Conclusions and Relevance: Heterologous Ad26.COV2.S boosting was associated with durable humoral and cellular immune responses in individuals who originally received the BNT162b2 vaccine. These data suggest potential benefits of heterologous prime-boost vaccine regimens for SARS-CoV-2.

A bivalent SARS-CoV-2 monoclonal antibody combination does not affect the immunogenicity of a vector-based COVID-19 vaccine in macaques.

Human monoclonal antibodies (mAbs) that target the spike glycoprotein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) offer a promising approach for the prevention and treatment of coronavirus disease 2019 (COVID-19). Given suboptimal global vaccination rates, waning immunity in vaccinated individuals, and the emergence of SARS-CoV-2 variants of concern, the use of mAbs for COVID-19 prevention may increase and may need to be administered together with vaccines in certain settings. However, it is unknown whether administration of mAbs will affect the immunogenicity of SARS-CoV-2 vaccines. Using an adenovirus vector-based SARS-CoV-2 vaccine, we show that simultaneous administration of the vaccine with SARS-CoV-2 mAbs does not diminish vaccine-induced humoral or cellular immunity in cynomolgus macaques. These results suggest that SARS-CoV-2 mAbs and viral vector-based SARS-CoV-2 vaccines can be administered together without loss of potency of either product. Additional studies will be required to evaluate coadministration of mAbs with other vaccine platforms.

Therapeutic efficacy of combined active and passive immunization in ART-suppressed, SHIV-infected rhesus macaques.

The latent viral reservoir is the critical barrier for developing an HIV-1 cure. Previous studies have shown that therapeutic vaccination or broadly neutralizing antibody (bNAb) administration, together with a Toll-like receptor 7 (TLR7) agonist, enhanced virologic control or delayed viral rebound, respectively, following discontinuation of antiretroviral therapy (ART) in SIV- or SHIV-infected rhesus macaques. Here we show that the combination of active and passive immunization with vesatolimod may lead to higher rates of post-ART virologic control compared to either approach alone. Therapeutic Ad26/MVA vaccination and PGT121 administration together with TLR7 stimulation with vesatolimod resulted in 70% post-ART virologic control in SHIV-SF162P3-infected rhesus macaques. These data suggest the potential of combining active and passive immunization targeting different immunologic mechanisms as an HIV-1 cure strategy.

Reduced SARS-CoV-2 disease outcomes in Syrian hamsters receiving immune sera: Quantitative image analysis in pathologic assessments.

There is a need to standardize pathologic endpoints in animal models of SARS-CoV-2 infection to help benchmark study quality, improve cross-institutional comparison of data, and assess therapeutic efficacy so that potential drugs and vaccines for SARS-CoV-2 can rapidly advance. The Syrian hamster model is a tractable small animal model for COVID-19 that models clinical disease in humans. Using the hamster model, the authors used traditional pathologic assessment with quantitative image analysis to assess disease outcomes in hamsters administered polyclonal immune sera from previously challenged rhesus macaques. The authors then used quantitative image analysis to assess pathologic endpoints across studies performed at different institutions using different tissue processing protocols. The authors detail pathological features of SARS-CoV-2 infection longitudinally and use immunohistochemistry to quantify myeloid cells and T lymphocyte infiltrates during SARS-CoV-2 infection. High-dose immune sera protected hamsters from weight loss and diminished viral replication in tissues and reduced lung lesions. Cumulative pathology scoring correlated with weight loss and was robust in distinguishing IgG efficacy. In formalin-infused lungs, quantitative measurement of percent area affected also correlated with weight loss but was less robust in non-formalin-infused lungs. Longitudinal immunohistochemical assessment of interstitial macrophage infiltrates showed that peak infiltration corresponded to weight loss, yet quantitative assessment of macrophage, neutrophil, and CD3+ T lymphocyte numbers did not distinguish IgG treatment effects. Here, the authors show that quantitative image analysis was a useful adjunct tool for assessing SARS-CoV-2 treatment outcomes in the hamster model.

Therapeutic efficacy of an Ad26/MVA vaccine with SIV gp140 protein and vesatolimod in ART-suppressed rhesus macaques.

Developing an intervention that results in virologic control following discontinuation of antiretroviral therapy (ART) is a major objective of HIV-1 cure research. In this study, we investigated the therapeutic efficacy of a vaccine consisting of adenovirus serotype 26 (Ad26) and modified vaccinia Ankara (MVA) with or without an SIV Envelope (Env) gp140 protein with alum adjuvant in combination with the TLR7 agonist vesatolimod (GS-9620) in 36 ART-suppressed, SIVmac251-infected rhesus macaques. Ad26/MVA therapeutic vaccination led to robust humoral and cellular immune responses, and the Env protein boost increased antibody responses. Following discontinuation of ART, virologic control was observed in 5/12 animals in each vaccine group, compared with 0/12 animals in the sham control group. These data demonstrate therapeutic efficacy of Ad26/MVA vaccination with vesatolimod but no clear additional benefit of adding an Env protein boost. SIV-specific cellular immune responses correlated with virologic control. Our findings show partial efficacy of therapeutic vaccination following ART discontinuation in SIV-infected rhesus macaques.

HIV envelope antibodies and TLR7 agonist partially prevent viral rebound in chronically SHIV-infected monkeys.

A key challenge for the development of a cure to HIV-1 infection is the persistent viral reservoir established during early infection. Previous studies using Toll-like receptor 7 (TLR7) agonists and broadly neutralizing antibodies (bNAbs) have shown delay or prevention of viral rebound following antiretroviral therapy (ART) discontinuation in simian-human immunodeficiency virus (SHIV)-infected rhesus macaques. In these prior studies, ART was initiated early during acute infection, which limited the size and diversity of the viral reservoir. Here we evaluated in SHIV-infected rhesus macaques that did not initiate ART until 1 year into chronic infection whether the TLR7 agonist vesatolimod in combination with the bNAb PGT121, formatted either as a human IgG1, an effector enhanced IgG1, or an anti-CD3 bispecific antibody, would delay or prevent viral rebound following ART discontinuation. We found that all 3 antibody formats in combination with vesatolimod were able to prevent viral rebound following ART discontinuation in a subset of animals. These data indicate that a TLR7 agonist combined with antibodies may be a promising strategy to achieve long-term ART-free HIV remission in humans.

Vaccine protection against the SARS-CoV-2 Omicron variant in macaques.

The rapid spread of the SARS-CoV-2 Omicron (B.1.1.529) variant, including in highly vaccinated populations, has raised important questions about the efficacy of current vaccines. In this study, we show that the mRNA-based BNT162b2 vaccine and the adenovirus-vector-based Ad26.COV2.S vaccine provide robust protection against high-dose challenge with the SARS-CoV-2 Omicron variant in cynomolgus macaques. We vaccinated 30 macaques with homologous and heterologous prime-boost regimens with BNT162b2 and Ad26.COV2.S. Following Omicron challenge, vaccinated macaques demonstrated rapid control of virus in bronchoalveolar lavage, and most vaccinated animals also controlled virus in nasal swabs. However, 4 vaccinated animals that had moderate Omicron-neutralizing antibody titers and undetectable Omicron CD8+ T cell responses failed to control virus in the upper respiratory tract. Moreover, virologic control correlated with both antibody and T cell responses. These data suggest that both humoral and cellular immune responses contribute to vaccine protection against a highly mutated SARS-CoV-2 variant.

Characterization of immune responses in fully vaccinated individuals after breakthrough infection with the SARS-CoV-2 delta variant.

Breakthrough infections with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants have been reported frequently in vaccinated individuals with waning immunity. In particular, a cluster of over 1000 infections with the SARS-CoV-2 delta variant was identified in a predominantly fully vaccinated population in Provincetown, Massachusetts in July 2021. In this study, vaccinated individuals who tested positive for SARS-CoV-2 (n = 16) demonstrated substantially higher serum antibody responses than vaccinated individuals who tested negative for SARS-CoV-2 (n = 23), including 32-fold higher binding antibody titers and 31-fold higher neutralizing antibody titers against the SARS-CoV-2 delta variant. Vaccinated individuals who tested positive also showed higher mucosal antibody responses in nasal secretions and higher spike protein-specific CD8+ T cell responses in peripheral blood than did vaccinated individuals who tested negative. These data demonstrate that fully vaccinated individuals developed robust anamnestic antibody and T cell responses after infection with the SARS-CoV-2 delta variant. Moreover, these findings suggest that population immunity will likely increase over time by a combination of widespread vaccination and breakthrough infections.

SARS-CoV-2 receptor binding domain displayed on HBsAg virus-like particles elicits protective immunity in macaques.

Authorized vaccines against SARS-CoV-2 remain less available in low- and middle-income countries due to insufficient supply, high costs, and storage requirements. Global immunity could still benefit from new vaccines using widely available, safe adjuvants, such as alum and protein subunits, suited to low-cost production in existing manufacturing facilities. Here, a clinical-stage vaccine candidate comprising a SARS-CoV-2 receptor binding domain-hepatitis B surface antigen virus-like particle elicited protective immunity in cynomolgus macaques. Titers of neutralizing antibodies (>104) induced by this candidate were above the range of protection for other licensed vaccines in nonhuman primates. Including CpG 1018 did not significantly improve the immunological responses. Vaccinated animals challenged with SARS-CoV-2 showed reduced median viral loads in bronchoalveolar lavage (~3.4 log10) and nasal mucosa (~2.9 log10) versus sham controls. These data support the potential benefit of this design for a low-cost modular vaccine platform for SARS-CoV-2 and other variants of concern or betacoronaviruses.

A combination of two human neutralizing antibodies prevents SARS-CoV-2 infection in cynomolgus macaques.

BACKGROUND: Human monoclonal antibody (mAb) treatments are promising for COVID-19 prevention or therapy. The pre-exposure prophylactic efficacy of neutralizing antibodies that are engineered with mutations to extend their persistence in human serum and the neutralizing antibody titer in serum required for protection against SARS-CoV-2 infection remain poorly characterized. METHODS: The Fc region of two neutralizing mAbs (COV2-2130 and COV2-2381) targeting non-overlapping epitopes on the receptor binding domain of SARS-CoV-2 spike protein was engineered to extend their persistence in humans and reduce interactions with Fc gamma receptors. We assessed protection by individual antibodies or a combination of the two antibodies (designated ADM03820) given prophylactically by an intravenous or intramuscular route in a non-human primate (NHP) model of SARS-CoV-2 infection. FINDINGS: Passive transfer of individual mAbs or ADM03820 conferred virological protection in the NHP respiratory tract in a dose-dependent manner, and ADM03820 potently neutralized SARS-CoV-2 variants of concern in vitro. We defined a protective serum-neutralizing antibody titer and concentration in NHPs for passively transferred human antibodies that acted by direct viral neutralization. CONCLUSIONS: In summary, we demonstrate that neutralizing antibodies with extended half-life and lacking Fc-mediated effector functions are efficient for pre-exposure prophylaxis of SARS-CoV-2 infection in NHPs. These results support clinical development of ADM03820 for COVID-19 prevention. FUNDING: This research was supported by a contract from the JPEO-CBRND (W911QY-20-9-003, 20-05); the Joint Sciences and Technology Office and Joint Program Executive Office (MCDC-16-01-002 JSTO, JPEO); a DARPA grant (HR0011-18-2-0001); an NIH grant (R01 AI157155); and the 2019 Future Insight Prize from Merck KGaA.

Vaccines elicit highly conserved cellular immunity to SARS-CoV-2 Omicron.

The highly mutated SARS-CoV-2 Omicron (B.1.1.529) variant has been shown to evade a substantial fraction of neutralizing antibody responses elicited by current vaccines that encode the WA1/2020 spike protein1. Cellular immune responses, particularly CD8+ T cell responses, probably contribute to protection against severe SARS-CoV-2 infection2-6. Here we show that cellular immunity induced by current vaccines against SARS-CoV-2 is highly conserved to the SARS-CoV-2 Omicron spike protein. Individuals who received the Ad26.COV2.S or BNT162b2 vaccines demonstrated durable spike-specific CD8+ and CD4+ T cell responses, which showed extensive cross-reactivity against both the Delta and the Omicron variants, including in central and effector memory cellular subpopulations. Median Omicron spike-specific CD8+ T cell responses were 82-84% of the WA1/2020 spike-specific CD8+ T cell responses. These data provide immunological context for the observation that current vaccines still show robust protection against severe disease with the SARS-CoV-2 Omicron variant despite the substantially reduced neutralizing antibody responses7,8.

A homologous or variant booster vaccine after Ad26.COV2.S immunization enhances SARS-CoV-2-specific immune responses in rhesus macaques.

Ad26.COV2.S has demonstrated durability and clinical efficacy against symptomatic COVID-19 in humans. In this study, we report the correlates of durability of humoral and cellular immune responses in 20 rhesus macaques immunized with single-shot Ad26.COV2.S and the immunogenicity of a booster shot at 8 to 10 months after the initial immunization. Ad26.COV2.S elicited durable binding and neutralizing antibodies as well as memory B cells and long-lived bone marrow plasma cells. Innate immune responses and bone marrow plasma cell responses correlated with durable antibody responses. After Ad26.COV2.S boost immunization, binding and neutralizing antibody responses against multiple SARS-CoV-2 variants increased 31- to 69-fold and 23- to 43-fold, respectively, compared with preboost concentrations. Antigen-specific B cell and T cell responses also increased substantially after the boost immunization. Boosting with a modified Ad26.COV2.S.351 vaccine expressing the SARS-CoV-2 spike protein from the beta variant led to largely comparable responses with slightly higher beta- and omicron-specific humoral immune responses. These data demonstrate that a late boost with Ad26.COV2.S or Ad26.COV2.S.351 resulted in a marked increase in humoral and cellular immune responses that were highly cross-reactive across multiple SARS-CoV-2 variants in rhesus macaques.

Vaccine Protection Against the SARS-CoV-2 Omicron Variant in Macaques.

BACKGROUND: The rapid spread of the SARS-CoV-2 Omicron (B.1.1.529) variant, including in highly vaccinated populations, has raised important questions about the efficacy of current vaccines. Immune correlates of vaccine protection against Omicron are not known. METHODS: 30 cynomolgus macaques were immunized with homologous and heterologous prime-boost regimens with the mRNA-based BNT162b2 vaccine and the adenovirus vector-based Ad26.COV2.S vaccine. Following vaccination, animals were challenged with the SARS-CoV-2 Omicron variant by the intranasal and intratracheal routes. RESULTS: Omicron neutralizing antibodies were observed following the boost immunization and were higher in animals that received BNT162b2, whereas Omicron CD8+ T cell responses were higher in animals that received Ad26.COV2.S. Following Omicron challenge, sham controls showed more prolonged virus in nasal swabs than in bronchoalveolar lavage. Vaccinated macaques demonstrated rapid control of virus in bronchoalveolar lavage, and most vaccinated animals also controlled virus in nasal swabs, showing that current vaccines provide substantial protection against Omicron in this model. However, vaccinated animals that had moderate levels of Omicron neutralizing antibodies but negligible Omicron CD8+ T cell responses failed to control virus in the upper respiratory tract. Virologic control correlated with both antibody and T cell responses. CONCLUSIONS: BNT162b2 and Ad26.COV2.S provided robust protection against high-dose challenge with the SARS-CoV-2 Omicron variant in macaques. Protection against this highly mutated SARS-CoV-2 variant correlated with both humoral and cellular immune responses.

Comparable Neutralization of the SARS-CoV-2 Omicron BA.1 and BA.2 Variants.

The SARS-CoV-2 Omicron variant (B.1.1.529) has three major lineages BA.1, BA.2, and BA.3 1 . BA.1 rapidly became dominant and has demonstrated substantial escape from neutralizing antibodies (NAbs) induced by vaccination 2-4 . BA.2 has recently increased in frequency in multiple regions of the world, suggesting that BA.2 has a selective advantage over BA.1. BA.1 and BA.2 share multiple common mutations, but both also have unique mutations 1 ( Fig. 1A ). The ability of BA.2 to evade NAbs induced by vaccination or infection has not yet been reported. We evaluated WA1/2020, Omicron BA.1, and BA.2 NAbs in 24 individuals who were vaccinated and boosted with the mRNA BNT162b2 vaccine 5 and in 8 individuals who were infected with SARS-CoV-2 ( Table S1 ).

Vaccines Elicit Highly Cross-Reactive Cellular Immunity to the SARS-CoV-2 Omicron Variant.

The highly mutated SARS-CoV-2 Omicron (B.1.1.529) variant has been shown to evade a substantial fraction of neutralizing antibody responses elicited by current vaccines that encode the WA1/2020 Spike immunogen 1 , resulting in increased breakthrough infections and reduced vaccine efficacy. Cellular immune responses, particularly CD8+ T cell responses, are likely critical for protection against severe SARS-CoV-2 disease 2-6 . Here we show that cellular immunity induced by current SARS-CoV-2 vaccines is highly cross-reactive against the SARS-CoV-2 Omicron variant. Individuals who received Ad26.COV2.S or BNT162b2 vaccines demonstrated durable CD8+ and CD4+ T cell responses that showed extensive cross-reactivity against both the Delta and Omicron variants, including in central and effector memory cellular subpopulations. Median Omicron-specific CD8+ T cell responses were 82-84% of WA1/2020-specific CD8+ T cell responses. These data suggest that current vaccines may provide considerable protection against severe disease with the SARS-CoV-2 Omicron variant despite the substantial reduction of neutralizing antibody responses.

Passive transfer of Ad26.COV2.S-elicited IgG from humans attenuates SARS-CoV-2 disease in hamsters.

SARS-CoV-2 Spike-specific binding and neutralizing antibodies, elicited either by natural infection or vaccination, have emerged as potential correlates of protection. An important question, however, is whether vaccine-elicited antibodies in humans provide direct, functional protection from SARS-CoV-2 infection and disease. In this study, we explored directly the protective efficacy of human antibodies elicited by Ad26.COV2.S vaccination by adoptive transfer studies. IgG from plasma of Ad26.COV2.S vaccinated individuals was purified and transferred into naïve golden Syrian hamster recipients, followed by intra-nasal challenge of the hamsters with SARS-CoV-2. IgG purified from Ad26.COV2.S-vaccinated individuals provided dose-dependent protection in the recipient hamsters from weight loss following challenge. In contrast, IgG purified from placebo recipients provided no protection in this adoptive transfer model. Attenuation of weight loss correlated with binding and neutralizing antibody titers of the passively transferred IgG. This study suggests that Ad26.COV2.S-elicited antibodies in humans are mechanistically involved in protection against SARS-CoV-2.