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.

Protection from SARS-CoV-2 Delta one year after mRNA-1273 vaccination in rhesus macaques coincides with anamnestic antibody response in the lung.

mRNA-1273 vaccine efficacy against SARS-CoV-2 Delta wanes over time; however, there are limited data on the impact of durability of immune responses on protection. Here, we immunized rhesus macaques and assessed immune responses over 1 year in blood and upper and lower airways. Serum neutralizing titers to Delta were 280 and 34 reciprocal ID50 at weeks 6 (peak) and 48 (challenge), respectively. Antibody-binding titers also decreased in bronchoalveolar lavage (BAL). Four days after Delta challenge, the virus was unculturable in BAL, and subgenomic RNA declined by ∼3-log10 compared with control animals. In nasal swabs, sgRNA was reduced by 1-log10, and the virus remained culturable. Anamnestic antibodies (590-fold increased titer) but not T cell responses were detected in BAL by day 4 post-challenge. mRNA-1273-mediated protection in the lungs is durable but delayed and potentially dependent on anamnestic antibody responses. Rapid and sustained protection in upper and lower airways may eventually require a boost.

BCG vaccination stimulates integrated organ immunity by feedback of the adaptive immune response to imprint prolonged innate antiviral resistance.

Bacille Calmette-Guérin (BCG) vaccination can confer nonspecific protection against heterologous pathogens. However, the underlying mechanisms remain mysterious. We show that mice vaccinated intravenously with BCG exhibited reduced weight loss and/or improved viral clearance when challenged with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2 B.1.351) or PR8 influenza. Protection was first evident between 14 and 21 d post-vaccination and lasted ∼3 months. Notably, BCG induced a biphasic innate response and robust antigen-specific type 1 helper T cell (TH1 cell) responses in the lungs. MyD88 signaling was essential for innate and TH1 cell responses, and protection against SARS-CoV-2. Depletion of CD4+ T cells or interferon (IFN)-γ activity before infection obliterated innate activation and protection. Single-cell and spatial transcriptomics revealed CD4-dependent expression of IFN-stimulated genes in lung myeloid and epithelial cells. Notably, BCG also induced protection against weight loss after mouse-adapted SARS-CoV-2 BA.5, SARS-CoV and SHC014 coronavirus infections. Thus, BCG elicits integrated organ immunity, where CD4+ T cells feed back on tissue myeloid and epithelial cells to imprint prolonged and broad innate antiviral resistance.

Fighting the SARS-CoV-2 pandemic requires a global approach to understanding the heterogeneity of vaccine responses.

Host genetic and environmental factors including age, biological sex, diet, geographical location, microbiome composition and metabolites converge to influence innate and adaptive immune responses to vaccines. Failure to understand and account for these factors when investigating severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine efficacy may impair the development of the next generation of vaccines. Most studies aimed at identifying mechanisms of vaccine-mediated immune protection have focused on adaptive immune responses. It is well established, however, that mobilization of the innate immune response is essential to the development of effective cellular and humoral immunity. A comprehensive understanding of the innate immune response and environmental factors that contribute to the development of broad and durable cellular and humoral immune responses to SARS-CoV-2 and other vaccines requires a holistic and unbiased approach. Along with optimization of the immunogen and vectors, the development of adjuvants based on our evolving understanding of how the innate immune system shapes vaccine responses will be essential. Defining the innate immune mechanisms underlying the establishment of long-lived plasma cells and memory T cells could lead to a universal vaccine for coronaviruses, a key biomedical priority.

mRNA-1273 protects against SARS-CoV-2 beta infection in nonhuman primates.

B.1.351 is the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant most resistant to antibody neutralization. We demonstrate how the dose and number of immunizations influence protection. Nonhuman primates received two doses of 30 or 100 µg of Moderna's mRNA-1273 vaccine, a single immunization of 30 µg, or no vaccine. Two doses of 100 µg of mRNA-1273 induced 50% inhibitory reciprocal serum dilution neutralizing antibody titers against live SARS-CoV-2 p.Asp614Gly and B.1.351 of 3,300 and 240, respectively. Higher neutralizing responses against B.1.617.2 were also observed after two doses compared to a single dose. After challenge with B.1.351, there was ~4- to 5-log10 reduction of viral subgenomic RNA and low to undetectable replication in bronchoalveolar lavages in the two-dose vaccine groups, with a 1-log10 reduction in nasal swabs in the 100-µg group. These data establish that a two-dose regimen of mRNA-1273 will be critical for providing upper and lower airway protection against major variants of concern.

A modified vaccinia Ankara vector-based vaccine protects macaques from SARS-CoV-2 infection, immune pathology, and dysfunction in the lungs.

A combination of vaccination approaches will likely be necessary to fully control the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. Here, we show that modified vaccinia Ankara (MVA) vectors expressing membrane-anchored pre-fusion stabilized spike (MVA/S) but not secreted S1 induced strong neutralizing antibody responses against SARS-CoV-2 in mice. In macaques, the MVA/S vaccination induced strong neutralizing antibodies and CD8+ T cell responses, and conferred protection from SARS-CoV-2 infection and virus replication in the lungs as early as day 2 following intranasal and intratracheal challenge. Single-cell RNA sequencing analysis of lung cells on day 4 after infection revealed that MVA/S vaccination also protected macaques from infection-induced inflammation and B cell abnormalities and lowered induction of interferon-stimulated genes. These results demonstrate that MVA/S vaccination induces neutralizing antibodies and CD8+ T cells in the blood and lungs and is a potential vaccine candidate for SARS-CoV-2.

Mucosal boosting enhances vaccine protection against SARS-CoV-2 in macaques.

A limitation of current SARS-CoV-2 vaccines is that they provide minimal protection against infection with current Omicron subvariants1,2, although they still provide protection against severe disease. Enhanced mucosal immunity may be required to block infection and onward transmission. Intranasal administration of current vaccines has proven inconsistent3-7, suggesting that alternative immunization strategies may be required. Here we show that intratracheal boosting with a bivalent Ad26-based SARS-CoV-2 vaccine results in substantial induction of mucosal humoral and cellular immunity and near-complete protection against SARS-CoV-2 BQ.1.1 challenge. A total of 40 previously immunized rhesus macaques were boosted with a bivalent Ad26 vaccine by the intramuscular, intranasal and intratracheal routes, or with a bivalent mRNA vaccine by the intranasal route. Ad26 boosting by the intratracheal route led to a substantial expansion of mucosal neutralizing antibodies, IgG and IgA binding antibodies, and CD8+ and CD4+ T cell responses, which exceeded those induced by Ad26 boosting by the intramuscular and intranasal routes. Intratracheal Ad26 boosting also led to robust upregulation of cytokine, natural killer, and T and B cell pathways in the lungs. After challenge with a high dose of SARS-CoV-2 BQ.1.1, intratracheal Ad26 boosting provided near-complete protection, whereas the other boosting strategies proved less effective. Protective efficacy correlated best with mucosal humoral and cellular immune responses. These data demonstrate that these immunization strategies induce robust mucosal immunity, suggesting the feasibility of developing vaccines that block respiratory viral infections.

S6K-STING interaction regulates cytosolic DNA-mediated activation of the transcription factor IRF3.

Cytosolic DNA-mediated activation of the transcription factor IRF3 is a key event in host antiviral responses. Here we found that infection with DNA viruses induced interaction of the metabolic checkpoint kinase mTOR downstream effector and kinase S6K1 and the signaling adaptor STING in a manner dependent on the DNA sensor cGAS. We further demonstrated that the kinase domain, but not the kinase function, of S6K1 was required for the S6K1-STING interaction and that the TBK1 critically promoted this process. The formation of a tripartite S6K1-STING-TBK1 complex was necessary for the activation of IRF3, and disruption of this signaling axis impaired the early-phase expression of IRF3 target genes and the induction of T cell responses and mucosal antiviral immunity. Thus, our results have uncovered a fundamental regulatory mechanism for the activation of IRF3 in the cytosolic DNA pathway.

Durability of immune responses to SARS-CoV-2 infection and vaccination.

Infection with SARS-CoV-2 in humans has caused a pandemic of unprecedented dimensions. SARS-CoV-2 is primarily transmitted through respiratory droplets and targets ciliated epithelial cells in the nasal cavity, trachea, and lungs by utilizing the cellular receptor angiotensin-converting enzyme 2 (ACE2). The innate immune response, including type I and III interferons, inflammatory cytokines (IL-6, TNF-α, IL-1ß), innate immune cells (monocytes, DCs, neutrophils, natural killer cells), antibodies (IgG, sIgA, neutralizing antibodies), and adaptive immune cells (B cells, CD8+ and CD4+ T cells) play pivotal roles in mitigating COVID-19 disease. Broad and durable B-cell- and T-cell immunity elicited by infection and vaccination is essential for protection against severe disease, hospitalization and death. However, the emergence of SARS-CoV-2 variants that evade neutralizing antibodies continue to jeopardize vaccine efficacy. In this review, we highlight our understanding the infection- and vaccine-mediated humoral, B and T cell responses, the durability of the immune responses, and how variants continue to threaten the efficacy of SARS-CoV-2 vaccines.

Loss of furin cleavage site attenuates SARS-CoV-2 pathogenesis.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-a new coronavirus that has led to a worldwide pandemic1-has a furin cleavage site (PRRAR) in its spike protein that is absent in other group-2B coronaviruses2. To explore whether the furin cleavage site contributes to infection and pathogenesis in this virus, we generated a mutant SARS-CoV-2 that lacks the furin cleavage site (ΔPRRA). Here we report that replicates of ΔPRRA SARS-CoV-2 had faster kinetics, improved fitness in Vero E6 cells and reduced spike protein processing, as compared to parental SARS-CoV-2. However, the ΔPRRA mutant had reduced replication in a human respiratory cell line and was attenuated in both hamster and K18-hACE2 transgenic mouse models of SARS-CoV-2 pathogenesis. Despite reduced disease, the ΔPRRA mutant conferred protection against rechallenge with the parental SARS-CoV-2. Importantly, the neutralization values of sera from patients with coronavirus disease 2019 (COVID-19) and monoclonal antibodies against the receptor-binding domain of SARS-CoV-2 were lower against the ΔPRRA mutant than against parental SARS-CoV-2, probably owing to an increased ratio of particles to plaque-forming units in infections with the former. Together, our results demonstrate a critical role for the furin cleavage site in infection with SARS-CoV-2 and highlight the importance of this site for evaluating the neutralization activities of antibodies.

In vivo monoclonal antibody efficacy against SARS-CoV-2 variant strains.

Rapidly emerging SARS-CoV-2 variants jeopardize antibody-based countermeasures. Although cell culture experiments have demonstrated a loss of potency of several anti-spike neutralizing antibodies against variant strains of SARS-CoV-21-3, the in vivo importance of these results remains uncertain. Here we report the in vitro and in vivo activity of a panel of monoclonal antibodies (mAbs), which correspond to many in advanced clinical development by Vir Biotechnology, AbbVie, AstraZeneca, Regeneron and Lilly, against SARS-CoV-2 variant viruses. Although some individual mAbs showed reduced or abrogated neutralizing activity in cell culture against B.1.351, B.1.1.28, B.1.617.1 and B.1.526 viruses with mutations at residue E484 of the spike protein, low prophylactic doses of mAb combinations protected against infection by many variants in K18-hACE2 transgenic mice, 129S2 immunocompetent mice and hamsters, without the emergence of resistance. Exceptions were LY-CoV555 monotherapy and LY-CoV555 and LY-CoV016 combination therapy, both of which lost all protective activity, and the combination of AbbVie 2B04 and 47D11, which showed a partial loss of activity. When administered after infection, higher doses of several mAb cocktails protected in vivo against viruses with a B.1.351 spike gene. Therefore, many-but not all-of the antibody products with Emergency Use Authorization should retain substantial efficacy against the prevailing variant strains of SARS-CoV-2.

Systems vaccinology of the BNT162b2 mRNA vaccine in humans.

The emergency use authorization of two mRNA vaccines in less than a year from the emergence of SARS-CoV-2 represents a landmark in vaccinology1,2. Yet, how mRNA vaccines stimulate the immune system to elicit protective immune responses is unknown. Here we used a systems vaccinology approach to comprehensively profile the innate and adaptive immune responses of 56 healthy volunteers who were vaccinated with the Pfizer-BioNTech mRNA vaccine (BNT162b2). Vaccination resulted in the robust production of neutralizing antibodies against the wild-type SARS-CoV-2 (derived from 2019-nCOV/USA_WA1/2020) and, to a lesser extent, the B.1.351 strain, as well as significant increases in antigen-specific polyfunctional CD4 and CD8 T cells after the second dose. Booster vaccination stimulated a notably enhanced innate immune response as compared to primary vaccination, evidenced by (1) a greater frequency of CD14+CD16+ inflammatory monocytes; (2) a higher concentration of plasma IFNγ; and (3) a transcriptional signature of innate antiviral immunity. Consistent with these observations, our single-cell transcriptomics analysis demonstrated an approximately 100-fold increase in the frequency of a myeloid cell cluster enriched in interferon-response transcription factors and reduced in AP-1 transcription factors, after secondary immunization. Finally, we identified distinct innate pathways associated with CD8 T cell and neutralizing antibody responses, and show that a monocyte-related signature correlates with the neutralizing antibody response against the B.1.351 variant. Collectively, these data provide insights into the immune responses induced by mRNA vaccination and demonstrate its capacity to prime the innate immune system to mount a more potent response after booster immunization.

Homologous and Heterologous Covid-19 Booster Vaccinations.

BACKGROUND: Although the three vaccines against coronavirus disease 2019 (Covid-19) that have received emergency use authorization in the United States are highly effective, breakthrough infections are occurring. Data are needed on the serial use of homologous boosters (same as the primary vaccine) and heterologous boosters (different from the primary vaccine) in fully vaccinated recipients. METHODS: In this phase 1-2, open-label clinical trial conducted at 10 sites in the United States, adults who had completed a Covid-19 vaccine regimen at least 12 weeks earlier and had no reported history of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection received a booster injection with one of three vaccines: mRNA-1273 (Moderna) at a dose of 100 µg, Ad26.COV2.S (Johnson & Johnson-Janssen) at a dose of 5×1010 virus particles, or BNT162b2 (Pfizer-BioNTech) at a dose of 30 µg. The primary end points were safety, reactogenicity, and humoral immunogenicity on trial days 15 and 29. RESULTS: Of the 458 participants who were enrolled in the trial, 154 received mRNA-1273, 150 received Ad26.COV2.S, and 153 received BNT162b2 as booster vaccines; 1 participant did not receive the assigned vaccine. Reactogenicity was similar to that reported for the primary series. More than half the recipients reported having injection-site pain, malaise, headache, or myalgia. For all combinations, antibody neutralizing titers against a SARS-CoV-2 D614G pseudovirus increased by a factor of 4 to 73, and binding titers increased by a factor of 5 to 55. Homologous boosters increased neutralizing antibody titers by a factor of 4 to 20, whereas heterologous boosters increased titers by a factor of 6 to 73. Spike-specific T-cell responses increased in all but the homologous Ad26.COV2.S-boosted subgroup. CD8+ T-cell levels were more durable in the Ad26.COV2.S-primed recipients, and heterologous boosting with the Ad26.COV2.S vaccine substantially increased spike-specific CD8+ T cells in the mRNA vaccine recipients. CONCLUSIONS: Homologous and heterologous booster vaccines had an acceptable safety profile and were immunogenic in adults who had completed a primary Covid-19 vaccine regimen at least 12 weeks earlier. (Funded by the National Institute of Allergy and Infectious Diseases; DMID 21-0012 ClinicalTrials.gov number, NCT04889209.).

Single-cell analysis reveals an antiviral network that controls Zika virus infection in human dendritic cells.

Zika virus (ZIKV) is a mosquito-borne flavivirus that caused an epidemic in the Americas in 2016 and is linked to severe neonatal birth defects, including microcephaly and spontaneous abortion. To better understand the host response to ZIKV infection, we adapted the 10× Genomics Chromium single-cell RNA sequencing (scRNA-seq) assay to simultaneously capture viral RNA and host mRNA. Using this assay, we profiled the antiviral landscape in a population of human monocyte-derived dendritic cells infected with ZIKV at the single-cell level. The bystander cells, which lacked detectable viral RNA, expressed an antiviral state that was enriched for genes coinciding predominantly with a type I interferon (IFN) response. Within the infected cells, viral RNA negatively correlated with type I IFN-dependent and -independent genes (the antiviral module). We modeled the ZIKV-specific antiviral state at the protein level, leveraging experimentally derived protein interaction data. We identified a highly interconnected network between the antiviral module and other host proteins. In this work, we propose a new paradigm for evaluating the antiviral response to a specific virus, combining an unbiased list of genes that highly correlate with viral RNA on a per-cell basis with experimental protein interaction data. IMPORTANCE: Zika virus (ZIKV) remains a public health threat given its potential for re-emergence and the detrimental fetal outcomes associated with infection during pregnancy. Understanding the dynamics between ZIKV and its host is critical to understanding ZIKV pathogenesis. Through ZIKV-inclusive single-cell RNA sequencing (scRNA-seq), we demonstrate on the single-cell level the dynamic interplay between ZIKV and the host: the transcriptional program that restricts viral infection and ZIKV-mediated inhibition of that response. Our ZIKV-inclusive scRNA-seq assay will serve as a useful tool for gaining greater insight into the host response to ZIKV and can be applied more broadly to the flavivirus field.

Innate antiviral immunity: how prior exposures can guide future responses.

Innate immunity is an intrinsic baseline defense in cells, with its earliest origins in bacteria, and with key roles in defense against pathogens and in the activation of B and T cell responses. In mammals, the efficacy of innate immunity in initiating the cascades that lead to pathogen control results from the interplay of transcriptomic, epigenomic, and proteomic responses regulating immune activation and long-lived pathogen-specific memory responses. Recent studies suggest that intrinsic innate immunity is modulated by individual exposure histories - prior infections, vaccinations, and metabolites of microbial origin - and this promotes, or impairs, the development of efficacious innate immune responses. Understanding how environmental factors regulate innate immunity and boost protection from infection or response to vaccination could be a valuable tool for pandemic preparedness.

Local Cellular and Cytokine Cues in the Spleen Regulate In Situ T Cell Receptor Affinity, Function, and Fate of CD8+ T Cells.

T cells rapidly undergo contraction upon viral clearance, but how T cell function and fate are determined during this phase is unclear. During the contraction phase of an acute infection with lymphocytic choriomeningitis virus, we found that virus-specific CD8+ T cells within the splenic red pulp (RP) had higher two-dimensional (2D) effective affinity than those within the white pulp (WP). This increased antigen recognition of RP-derived CD8+ T cells correlated with more efficient target cell killing and improved control of viremia. FoxP3+ regulatory T cells and cytokine TGF-ß limited the 2D-affinity in the WP during the contraction phase. Anatomical location drove gene expression patterns in CD8+ T cells that led to preferential differentiation of memory precursor WP T cells into long-term memory cells. These results highlight that intricate regulation of T cell function and fate is determined by anatomic compartmentalization during the early immune contraction phase.

Interferon-induced transmembrane protein 3 (IFITM3) limits lethality of SARS-CoV-2 in mice.

Interferon-induced transmembrane protein 3 (IFITM3) is an antiviral protein that alters cell membranes to block fusion of viruses. Conflicting reports identified opposing effects of IFITM3 on SARS-CoV-2 infection of cells, and its impact on viral pathogenesis in vivo remains unclear. Here, we show that IFITM3 knockout (KO) mice infected with SARS-CoV-2 experience extreme weight loss and lethality compared to mild infection in wild-type (WT) mice. KO mice have higher lung viral titers and increases in inflammatory cytokine levels, immune cell infiltration, and histopathology. Mechanistically, we observe disseminated viral antigen staining throughout the lung and pulmonary vasculature in KO mice, as well as increased heart infection, indicating that IFITM3 constrains dissemination of SARS-CoV-2. Global transcriptomic analysis of infected lungs shows upregulation of gene signatures associated with interferons, inflammation, and angiogenesis in KO versus WT animals, highlighting changes in lung gene expression programs that precede severe lung pathology and fatality. Our results establish IFITM3 KO mice as a new animal model for studying severe SARS-CoV-2 infection and overall demonstrate that IFITM3 is protective in SARS-CoV-2 infections in vivo.

Caspase-4/11 exacerbates disease severity in SARS-CoV-2 infection by promoting inflammation and immunothrombosis.

Severe acute respiratory syndrome coronavirus 2 (SARS­CoV-2) is a worldwide health concern, and new treatment strategies are needed. Targeting inflammatory innate immunity pathways holds therapeutic promise, but effective molecular targets remain elusive. Here, we show that human caspase-4 (CASP4) and its mouse homolog, caspase-11 (CASP11), are up-regulated in SARS­CoV-2 infections and that CASP4 expression correlates with severity of SARS­CoV-2 infection in humans. SARS­CoV-2­infected Casp11−/− mice were protected from severe weight loss and lung pathology, including blood vessel damage, compared to wild-type (WT) mice and mice lacking the caspase downstream effector gasdermin-D (Gsdmd−/−). Notably, viral titers were similar regardless of CASP11 knockout. Global transcriptomics of SARS­CoV-2­infected WT, Casp11−/−, and Gsdmd−/− lungs identified restrained expression of inflammatory molecules and altered neutrophil gene signatures in Casp11−/− mice. We confirmed that protein levels of inflammatory mediators interleukin (IL)-1ß, IL-6, and CXCL1, as well as neutrophil functions, were reduced in Casp11−/− lungs. Additionally, Casp11−/− lungs accumulated less von Willebrand factor, a marker for endothelial damage, but expressed more Kruppel-Like Factor 2, a transcription factor that maintains vascular integrity. Overall, our results demonstrate that CASP4/11 promotes detrimental SARS­CoV-2­induced inflammation and coagulopathy, largely independently of GSDMD, identifying CASP4/11 as a promising drug target for treatment and prevention of severe COVID-19.

Patients taking benralizumab, dupilumab, or mepolizumab have lower postvaccination SARS-CoV-2 immunity.

BACKGROUND: Biologic therapies inhibiting the IL-4 or IL-5 pathways are very effective in the treatment of asthma and other related conditions. However, the cytokines IL-4 and IL-5 also play a role in the generation of adaptive immune responses. Although these biologics do not cause overt immunosuppression, their effect in primary severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) immunization has not been studied completely. OBJECTIVE: Our aim was to evaluate the antibody and cellular immunity after SARS-CoV-2 mRNA vaccination in patients on biologics (PoBs). METHODS: Patients with severe asthma or atopic dermatitis who were taking benralizumab, dupilumab, or mepolizumab and had received the initial dose of the 2-dose adult SARS-CoV-2 mRNA vaccine were enrolled in a prospective, observational study. As our control group, we used a cohort of immunologically healthy subjects (with no significant immunosuppression) who were not taking biologics (NBs). We used a multiplexed immunoassay to measure antibody levels, neutralization assays to assess antibody function, and flow cytometry to quantitate Spike-specific lymphocytes. RESULTS: We analyzed blood from 57 patients in the PoB group and 46 control subjects from the NB group. The patients in the PoB group had lower levels of SARS-CoV-2 antibodies, pseudovirus neutralization, live virus neutralization, and frequencies of Spike-specific B and CD8 T cells at 6 months after vaccination. In subgroup analyses, patients with asthma who were taking biologics had significantly lower pseudovirus neutralization than did subjects with asthma who were not taking biologics. CONCLUSION: The patients in the PoB group had reduced SARS-CoV-2-specific antibody titers, neutralizing activity, and virus-specific B- and CD8 T-cell counts. These results have implications when considering development of a more individualized immunization strategy in patients who receive biologic medications blocking IL-4 or IL-5 pathways.

Timing of exposure is critical in a highly sensitive model of SARS-CoV-2 transmission.

Transmission efficiency is a critical factor determining the size of an outbreak of infectious disease. Indeed, the propensity of SARS-CoV-2 to transmit among humans precipitated and continues to sustain the COVID-19 pandemic. Nevertheless, the number of new cases among contacts is highly variable and underlying reasons for wide-ranging transmission outcomes remain unclear. Here, we evaluated viral spread in golden Syrian hamsters to define the impact of temporal and environmental conditions on the efficiency of SARS-CoV-2 transmission through the air. Our data show that exposure periods as brief as one hour are sufficient to support robust transmission. However, the timing after infection is critical for transmission success, with the highest frequency of transmission to contacts occurring at times of peak viral load in the donor animals. Relative humidity and temperature had no detectable impact on transmission when exposures were carried out with optimal timing and high inoculation dose. However, contrary to expectation, trends observed with sub-optimal exposure timing and lower inoculation dose suggest improved transmission at high relative humidity or high temperature. In sum, among the conditions tested, our data reveal the timing of exposure to be the strongest determinant of SARS-CoV-2 transmission success and implicate viral load as an important driver of transmission.