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.

Immunogenicity of the Ad26.COV2.S Vaccine for COVID-19.

Importance: Control of the global COVID-19 pandemic will require the development and deployment of safe and effective vaccines. Objective: To evaluate the immunogenicity of the Ad26.COV2.S vaccine (Janssen/Johnson & Johnson) in humans, including the kinetics, magnitude, and phenotype of SARS-CoV-2 spike-specific humoral and cellular immune responses. Design, Setting, and Participants: Twenty-five participants were enrolled from July 29, 2020, to August 7, 2020, and the follow-up for this day 71 interim analysis was completed on October 3, 2020; follow-up to assess durability will continue for 2 years. This study was conducted at a single clinical site in Boston, Massachusetts, as part of a randomized, double-blind, placebo-controlled phase 1 clinical trial of Ad26.COV2.S. Interventions: Participants were randomized to receive 1 or 2 intramuscular injections with 5 × 1010 viral particles or 1 × 1011 viral particles of Ad26.COV2.S vaccine or placebo administered on day 1 and day 57 (5 participants in each group). Main Outcomes and Measures: Humoral immune responses included binding and neutralizing antibody responses at multiple time points following immunization. Cellular immune responses included immunospot-based and intracellular cytokine staining assays to measure T-cell responses. Results: Twenty-five participants were randomized (median age, 42; age range, 22-52; 52% women, 44% male, 4% undifferentiated), and all completed the trial through the day 71 interim end point. Binding and neutralizing antibodies emerged rapidly by day 8 after initial immunization in 90% and 25% of vaccine recipients, respectively. By day 57, binding and neutralizing antibodies were detected in 100% of vaccine recipients after a single immunization. On day 71, the geometric mean titers of spike-specific binding antibodies were 2432 to 5729 and the geometric mean titers of neutralizing antibodies were 242 to 449 in the vaccinated groups. A variety of antibody subclasses, Fc receptor binding properties, and antiviral functions were induced. CD4+ and CD8+ T-cell responses were induced. Conclusion and Relevance: In this phase 1 study, a single immunization with Ad26.COV2.S induced rapid binding and neutralization antibody responses as well as cellular immune responses. Two phase 3 clinical trials are currently underway to determine the efficacy of the Ad26.COV2.S vaccine. Trial Registration: ClinicalTrials.gov Identifier: NCT04436276.

Comparison of Subgenomic and Total RNA in SARS-CoV-2 Challenged Rhesus Macaques.

Respiratory virus challenge studies involve administration of the challenge virus and sampling to assess for protection from the same anatomical locations. It can therefore be difficult to differentiate actively replicating virus from input challenge virus. For SARS-CoV-2, specific monitoring of actively replicating virus is critical to investigate the protective and therapeutic efficacy of vaccines, monoclonal antibodies, and antiviral drugs. We developed a SARS-CoV-2 subgenomic RNA (sgRNA) RT-PCR assay to differentiate productive infection from inactivated or neutralized virus. Subgenomic RNAs are generated after cell entry and are poorly incorporate into mature virions, and thus may provide a marker for actively replicating virus. We show envelope (E) sgRNA was degraded by RNase in infected cell lysates, while genomic RNA (gRNA) was protected, presumably due to packaging into virions. To investigate the capacity of the sgRNA assay to distinguish input challenge virus from actively replicating virus in vivo, we compared the E sgRNA assay to a standard nucleoprotein (N) or E total RNA assay in convalescent rhesus macaques and in antibody-treated rhesus macaques after experimental SARS-CoV-2 challenge. In both studies, the E sgRNA assay was negative, suggesting protective efficacy, whereas the N and E total RNA assays remained positive. These data suggest the potential utility of sgRNA to monitor actively replicating virus in prophylactic and therapeutic SARS-CoV-2 studies.ImportanceDeveloping therapeutic and prophylactic countermeasures for the SARS-CoV-2 virus is a public health priority. During challenge studies, respiratory viruses are delivered and sampled from the same anatomical location. It is therefore important to distinguish actively replicating virus from input challenge virus. The most common assay for detecting SARS-CoV-2 virus, reverse transcription polymerase chain reaction (RT-PCR) targeting nucleocapsid total RNA, cannot distinguish neutralized input virus from replicating virus. In this study, we assess SARS-CoV-2 subgenomic RNA as a potential measure of replicating virus in rhesus macaques.

Deletion of the SARS-CoV-2 Spike Cytoplasmic Tail Increases Infectivity in Pseudovirus Neutralization Assays.

Pseudotyped viruses are valuable tools for studying virulent or lethal viral pathogens that need to be handled in biosafety level 3 (BSL-3) or higher facilities. With the explosive spread of the coronavirus disease 2019 (COVID-19) pandemic, the establishment of a BSL-2 adapted SARS-CoV-2 pseudovirus neutralization assay is needed to facilitate the development of countermeasures. Here we describe an approach to generate a single-round lentiviral vector-based SARS-CoV-2 pseudovirus, which produced a signal more than 2 logs above background. Specifically, a SARS-CoV-2 spike variant with a cytoplasmic tail deletion of 13 amino acids, termed SΔCT13, conferred enhanced spike incorporation into pseudovirions and increased viral entry into cells as compared with full-length spike (S). We further compared S and SΔCT13 in terms of their sensitivity to vaccine sera, purified convalescent IgG, hACE2-mIgG, and the virus entry inhibitor BafA1. We developed a SΔCT13-based pseudovirus neutralization assay and defined key assay characteristics, including linearity, limit of detection, and intra- and intermediate-assay precision. Our data demonstrate that the SΔCT13-based pseudovirus shows enhanced infectivity in target cells, which will facilitate the assessment of humoral immunity to SARS-CoV-2 infection, antibody therapeutics, and vaccination. This pseudovirus neutralization assay can also be readily adapted to SARS-CoV-2 variants that emerge.IMPORTANCESARS-CoV-2 is the etiologic agent of the COVID-19 pandemic. The development of a high throughput pseudovirus neutralization assay is critical for the development of vaccines and immune-based therapeutics. In this study, we show that deletion of the cytoplasmic tail of the SARS-CoV-2 spike leads to pseudoviruses with enhanced infectivity. This SΔCT13-based pseudovirus neutralization assay should be broadly useful for the field.

Single-shot Ad26 vaccine protects against SARS-CoV-2 in rhesus macaques.

A safe and effective vaccine for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) may be required to end the coronavirus disease 2019 (COVID-19) pandemic1-8. For global deployment and pandemic control, a vaccine that requires only a single immunization would be optimal. Here we show the immunogenicity and protective efficacy of a single dose of adenovirus serotype 26 (Ad26) vector-based vaccines expressing the SARS-CoV-2 spike (S) protein in non-human primates. Fifty-two rhesus macaques (Macaca mulatta) were immunized with Ad26 vectors that encoded S variants or sham control, and then challenged with SARS-CoV-2 by the intranasal and intratracheal routes9,10. The optimal Ad26 vaccine induced robust neutralizing antibody responses and provided complete or near-complete protection in bronchoalveolar lavage and nasal swabs after SARS-CoV-2 challenge. Titres of vaccine-elicited neutralizing antibodies correlated with protective efficacy, suggesting an immune correlate of protection. These data demonstrate robust single-shot vaccine protection against SARS-CoV-2 in non-human primates. The optimal Ad26 vector-based vaccine for SARS-CoV-2, termed Ad26.COV2.S, is currently being evaluated in clinical trials.

Potently neutralizing and protective human antibodies against SARS-CoV-2.

The ongoing pandemic of coronavirus disease 2019 (COVID-19), which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is a major threat to global health1 and the medical countermeasures available so far are limited2,3. Moreover, we currently lack a thorough understanding of the mechanisms of humoral immunity to SARS-CoV-24. Here we analyse a large panel of human monoclonal antibodies that target the spike (S) glycoprotein5, and identify several that exhibit potent neutralizing activity and fully block the receptor-binding domain of the S protein (SRBD) from interacting with human angiotensin-converting enzyme 2 (ACE2). Using competition-binding, structural and functional studies, we show that the monoclonal antibodies can be clustered into classes that recognize distinct epitopes on the SRBD, as well as distinct conformational states of the S trimer. Two potently neutralizing monoclonal antibodies, COV2-2196 and COV2-2130, which recognize non-overlapping sites, bound simultaneously to the S protein and neutralized wild-type SARS-CoV-2 virus in a synergistic manner. In two mouse models of SARS-CoV-2 infection, passive transfer of COV2-2196, COV2-2130 or a combination of both of these antibodies protected mice from weight loss and reduced the viral burden and levels of inflammation in the lungs. In addition, passive transfer of either of two of the most potent ACE2-blocking monoclonal antibodies (COV2-2196 or COV2-2381) as monotherapy protected rhesus macaques from SARS-CoV-2 infection. These results identify protective epitopes on the SRBD and provide a structure-based framework for rational vaccine design and the selection of robust immunotherapeutic agents.