Infection with SARS-CoV-2 can lead to long COVID, a chronic multisystemic condition estimated to affect approximately 400 million people worldwide. Although underlying mechanisms remain elusive, aberrant ongoing inflammation driven by Epstein-Barr virus (EBV) reactivation and persistent SARS-CoV-2 viral reservoirs have been hypothesized. We compared cellular and humoral immune responses to SARS-CoV-2 and EBV between participants with neuropsychiatric long COVID and recovered individuals. Peripheral blood mononuclear cells (PBMCs) and sera were collected from 27 long COVID individuals with ≥2 neuropsychiatric symptoms and 27 matched recovered participants at 3-6 months post-COVID-19 symptom onset (PSO). PBMCs were assessed for IFN-γ, IL-2, TNFα, and granzyme B T-cell responses against SARS-CoV-2, EBV, and human cytomegalovirus (HCMV). Sera were evaluated for neutralizing activity against live ancestral SARS-CoV-2 and EBV, and EBV reactivation was assessed by early antigen-diffuse IgG. We observed no significant differences in SARS-CoV-2-, EBV-, or HCMV-specific T-cell responses or live virus neutralization between long COVID and recovered groups at 3-6 months PSO. EBV reactivation was additionally only detected in one neuropsychiatric long COVID participant. However, reduced EBV neutralizing capacity at 3-6 months significantly associated with fatigue at 12 months PSO. Anti-EBV viral capsid antigen IgG levels were also significantly diminished in long COVID participants and similarly trended lower in those reporting fatigue at 12 months PSO. We therefore detected no differences in SARS-CoV-2- or EBV-specific T-cell responses or serological neutralizing capacity between neuropsychiatric long COVID and recovered participants; however, diminished EBV-specific humoral immunity may serve as a prognostic marker for neuropsychiatric long COVID development.

Abstract Background The receptor-binding domain (RBD) of the SARS-CoV-2 spike protein represents a key antigen for vaccine development due to its critical role in the ACE2 receptor recognition. Yeast-based expression systems, particularly Komagataella phaffii , offer scalable and cost-effective platforms for recombinant protein production. In addition to secretion, cell surface display provides an alternative strategy enabling direct antigen delivery, including applications via mucosal routes. Results In this study, we engineered K. phaffii strains for the production of SARS-CoV-2 RBD in two formats: as a secreted recombinant protein and as a cell surface-displayed antigen using a Sag1 anchoring system. Incorporation of glycine–serine linkers enhanced secretion efficiency, yielding up to 50 mg/L of RBD, with minimal intracellular retention. Western blot analysis indicated the presence of glycosylated forms of RBD, and the recombinant protein was subsequently purified for further characterization. Surface localization of RBD was validated by immunofluorescence microscopy and quantitative fluorescence measurements. Immunogenicity studies in mice demonstrated that intraperitoneal administration of purified RBD elicited a strong humoral immune response. Importantly, sera from immunized animals efficiently inhibited spike protein binding to the Ace2 receptor, indicating potent neutralizing activity. Comparable results were obtained following oral administration of K. phaffii cells displaying RBD on their surface, demonstrating the feasibility of a whole-cell yeast-based vaccine approach. Conclusions A yeast-based system enabling both secretion and surface display of SARS-CoV-2 RBD has been developed. Both delivery strategies, intraperitoneal administration of the purified protein and oral administration of recombinant yeast cells, induced robust and functionally relevant immune responses in mice. These findings highlight the potential of K. phaffii as a versatile system for the development of cost-effective subunit and oral vaccine candidates.

Since the emergence of SARS-CoV-2 in humans, novel variants have evolved to become dominant circulating lineages. These include D614G (B.1 lineage), Alpha (B.1.1.7), Gamma (P.1), Delta (B.1.617.2), and Omicron BA.1 (B.1.1.529) and BA.2 (B.1.1.529.2) viruses. Here, we compared the viral replication, pathogenesis, and transmissibility of these variants. Replication kinetics and innate immune response against the viruses were tested in ex vivo human nasal epithelial cells (HNEC) and induced pluripotent stem cell-derived lung organoids (IPSC-LOs), and the golden hamster model was employed to test pathogenicity and potential for transmission by the respiratory route. Delta, BA.1, and BA.2 viruses replicated more efficiently, and outcompeted D614G, Alpha, and Gamma viruses in an HNEC competition assay. BA.1 and BA.2 viruses, however, replicated poorly in IPSC-LOs compared to other variants. Moreover, BA.2 virus infection significantly increased secretion of IFN-λ1, IFN-λ2, IFN-λ3, IL-6, and IL-1RA in HNECs relative to D614G infection, but not in IPSC-LOs. The BA.1 and BA.2 viruses replicated less effectively in hamster lungs compared to the other variants; and while the Gamma virus reached titers comparable to D614G and Delta viruses, it caused greater lung pathology. Lastly, the Gamma and Delta variants transmitted more efficiently by the respiratory route compared to the other viruses, while BA.1 and BA.2 viruses transmitted less efficiently. These findings demonstrate the ongoing utility of experimental risk assessment as SARS-CoV-2 variants continue to evolve.

ABSTRACT The contributions of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific T cells to vaccine efficacy and durability are unclear. We investigated relationships between mRNA vaccine-induced spike-specific interferon- gamma (IFN-γ) and interleukin-2 (IL-2) T-cell responses and neutralizing antibody development in long-term care home staff doubly vaccinated with BNT162b2 or mRNA-1273. The impacts of pre-existing cross-reactive T-cell immunity on cellular and humoral responses to vaccination were additionally assessed. Mathematical modeling of the kinetics of spike-specific IFN-γ and IL-2 T-cell responses over 6 months post-second dose was bifurcated into recipients who exhibited gradual increases with doubling times of 155 and 167 days or decreases with half-lives of 165 and 132 days, respectively. Differences in kinetics did not correlate with clinical phenotypes. Serological anti-spike IgG, anti-receptor binding domain (RBD) IgG, anti-spike IgA, and anti-RBD IgA antibody levels otherwise decayed in all participants with half-lives of 63, 57, 79, and 46 days, respectively, alongside waning neutralizing capacity ( t 1/2 = 408 days). Spike-specific T-cell responses induced at 2–6 weeks positively correlated with live viral neutralization at 6 months post-second dose, especially in hybrid immune individuals. Participants with pre-existing cross-reactive T-cell immunity to SARS-CoV-2 exhibited greater spike-specific T-cell responses, reduced anti-RBD IgA antibody levels, and a trending increase in neutralization at 2–6 weeks post-second dose. Non-spike-specific T-cells predominantly targeted SARS-CoV-2 non-structural protein at 6 months post-second dose in cross-reactive participants. mRNA vaccination was lastly shown to induce off-target T-cell responses against unrelated antigens. In summary, vaccine-induced spike-specific T-cell immunity appeared to influence serological neutralizing capacity, with only a modest effect induced by pre-existing cross-reactivity. IMPORTANCE Our findings provide valuable insights into the potential contributions of mRNA vaccine-induced spike-specific T-cell responses to the durability of neutralizing antibody levels in both uninfected and hybrid immune recipients. Our study additionally sheds light on the precise impacts of pre-existing cross-reactive T-cell immunity to severe acute respiratory syndrome coronavirus 2 on the magnitude and kinetics of cellular and humoral responses to vaccination. Accordingly, our data will help optimize the development of next-generation T cell-based coronavirus vaccines and vaccine regimens to maximize efficacy and durability.

ABSTRACT The common cold coronaviruses are a source of ongoing morbidity and mortality particularly among elderly and immunocompromised individuals. While cross-reactive immune responses against multiple coronaviruses have been described following severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and vaccination, it remains unclear if these confer any degree of cross-protection against the common cold coronaviruses. A recombinant fowl adenovirus vaccine expressing the SARS-CoV-2 spike protein (FAdV-9-S19) was generated, and protection from SARS-CoV-2 challenge was shown in K18-hACE2 mice. Vaccinated mice were also challenged with the common cold coronaviruses human coronavirus (HCoV)-OC43 and HCoV-NL63 by the intranasal route, and viral shedding and lung burden were reduced in these groups compared to unvaccinated animals. Histopathological analysis of lung tissues revealed significantly less inflammation and lower pathology scores in mice that received FAdV-9-S19 . Because no mouse model for the coronavirus HCoV-229E exists, we vaccinated and challenged cynomolgus macaques to evaluate cross-protection against HCoV-229E. Animals were monitored for clinical signs of disease and viral shedding. Infectious virus was detected in both groups throughout the course of infection; however, vaccinated animals showed reduced viral shedding at multiple time points after infection. Histopathological analysis of lung tissues following challenge also indicated a more moderate disease in the vaccinated animals. Therefore, vaccination with FAdV-9-S19 also provided a moderate cross-protection against HCoV-229E disease in the cynomolgus macaques infection model. Our study demonstrates that vaccination with a recombinant fowl adenovirus expressing SARS-CoV-2 spike protein can provide a low-level cross-protection against beta- and alphacoronaviruses. These findings are important for the design of future pan-coronavirus vaccines. IMPORTANCE The common cold coronaviruses are a source of ongoing morbidity and mortality particularly among elderly and immunocompromised individuals, and no vaccine is currently available. Cross-reactive immune responses have been described following severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination; however, it remains unclear what degree of cross-protection they confer against the common cold coronaviruses. We demonstrate that both humoral and cell-mediated immune responses provide a low-level cross-protection, resulting in reduced viral load and pathology for the common cold coronaviruses OC43 and NL63 in mouse models. Additionally, we present a novel non-human primate (NHP) model of infection with the common cold coronavirus 229E, demonstrating that it mimics the disease observed in humans and can serve as a model for future vaccine studies, as cross-protection was also observed. This is significant as it suggests that current vaccines could provide a low-level protection against other coronaviruses and could serve as part of vaccination strategy against future novel coronaviruses.

Continuously emerging SARS-CoV-2 Omicron subvariants pose a threat thwarting the effectiveness of approved COVID-19 vaccines. Especially, the protection breadth and degree of these vaccines against antigenically distant Omicron subvariants is unclear. Here, we report the immunogenicity and efficacy of a bivalent mRNA vaccine, PTX-COVID19-M1.2 (M1.2), which encodes native spike proteins from Wuhan-Hu-1 (D614G) and Omicron BA.2.12.1, in mouse and hamster models. Both primary series and booster vaccination using M1.2 elicited potent and broad nAbs against Wuhan-Hu-1 (D614G) and some Omicron subvariants. Strong spike-specific T cell responses against Wuhan-Hu-1 and Omicron subvariants, including JN.1, were also induced. Vaccination with M1.2 protected animals from Wuhan-Hu-1 and multiple Omicron subvariants challenges. Interestingly, protection against XBB.1.5 lung infection did not correlate with nAb levels. These results indicate that M1.2 generated a broadly protective immune response against antigenically distant Omicron subvariants, and spike-specific T cells probably contributed to the breadth of the protection.

Although high titers of neutralizing Abs in human serum are associated with protection from reinfection by SARS-CoV-2, there is considerable heterogeneity in human serum-neutralizing Abs against SARS-CoV-2 during convalescence between individuals. Standard human serum live virus neutralization assays require inactivation of serum/plasma prior to testing. In this study, we report that the SARS-CoV-2 neutralization titers of human convalescent sera were relatively consistent across all disease states except for severe COVID-19, which yielded significantly higher neutralization titers. Furthermore, we show that heat inactivation of human serum significantly lowered neutralization activity in a live virus SARS-CoV-2 neutralization assay. Heat inactivation of human convalescent serum was shown to inactivate complement proteins, and the contribution of complement in SARS-CoV-2 neutralization was often >50% of the neutralizing activity of human sera without heat inactivation and could account for neutralizing activity when standard titers were zero after heat inactivation. This effect was also observed in COVID-19 vaccinees and could be abolished in individuals who were undergoing treatment with therapeutic anti-complement Abs. Complement activity was mainly dependent on the classical pathway with little contributions from mannose-binding lectin and alternative pathways. Our study demonstrates the importance of the complement pathway in significantly increasing viral neutralization activity against SARS-CoV-2 in spike seropositive individuals.

The continuous emergence of SARS-CoV-2 Omicron subvariants poses a serious threat thwarting the effectiveness of currently approved COVID-19 vaccines, demanding a vaccine that can provide broad protection against these subvariants. Although bivalent vaccines containing Omicron subvariant spikes have been shown to elicit high neutralizing antibodies (nAbs) and afford protection against homologous or antigenically close Omicron subvariants, the breadth and degree of the protection provided by the bivalent vaccines against antigenically distant Omicron subvariants is unclear. Here, we report the immunogenicity and efficacy of a bivalent mRNA vaccine, PTX-COVID19-M1.2 (M1.2), which encodes native spike proteins from Wuhan-Hu-1 (D614G) and Omicron BA.2.12.1, in mouse and hamster models. Both primary series and booster vaccination using M1.2 elicited potent and broad nAbs against Wuhan-Hu-1 (D614G) and Omicron subvariants, including BA.1, BA.2, BA.2.12.1, and BA.4/BA.5. Strong spike-specific T cell responses against Wuhan-Hu-1 and Omicron subvariants were also induced. In contrast, monovalent BA.2.12.1 spike-based mRNA vaccine elicited potent but narrower immune responses. Vaccination with M1.2 protected animals from Wuhan-Hu-1 and BA.1, BA.2, BA.5, and XBB.1.5 challenges. Interestingly, protection against XBB.1.5 lung infection did not correlate with nAb levels. These results indicate that M1.2 can generate a broadly protective immune response against multiple Omicron subvariants, including antigenically distant subvariants, and spike-specific T cells probably contribute to the breadth of the protection. Our findings have potential implications for designing COVID-19 booster vaccination strategies.

Background: There is limited understanding of the impact of coronavirus disease 2019 (COVID-19) infection and vaccination type and interval on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) human milk antibodies and their neutralizing capacity. Objectives: These cohort studies aimed to determine the presence of antibodies and live virus neutralizing capacity in milk from females infected with COVID-19, unexposed milk bank donors, and vaccinated females and examine impacts of vaccine interval and type. Methods: Milk was collected from participants infected with COVID-19 during pregnancy or lactation (Cohort -1) and milk bank donors (Cohort -2) from March 2020-July 2021 at 3 sequential 4 -wk intervals and COVID-19 vaccinated participants with varying dose intervals (Cohort -3) (January-October 2021). Cohort -1 and Cohort -3 were recruited from Sinai Health (patients) and through social media. Cohort -2 included Ontario Milk Bank donors. Milk was examined for SARS-CoV-2 antibodies and live virus neutralization. Results: Of females with COVID-19, 53% (Cohort -1, n = 55) had anti-SARS-CoV-2 IgA antibodies in >= 1 milk sample. IgA+ samples (40%) were more likely neutralizing than IgA- samples (odds ratio [OR]: 2.18; 95% confidence interval [CI]: 1.03, 4.60; P = 0.04); however, 25% of IgA- samples were neutralizing. Both IgA positivity and neutralization decreased similar to 6 mo after symptom onset (0-100 compared with 201+ d: IgA OR: 14.30; 95% CI: 1.08, 189.89; P = 0.04; neutralizing OR: 4.30; 95% CI: 1.55, 11.89; P = 0.005). Among milk bank donors (Cohort -2, n = 373), 4.3% had IgA antibodies; 23% of IgA+ samples were neutralizing. Vaccination (Cohort -3, n = 60) with mRNA-1273 and shorter vaccine intervals (3 to <6 wk) resulted in higher IgA and IgG than BNT162b2 (P < 0.04) and longer intervals (6 to <16 wk) (P <= 0.02), respectively. Neutralizing capacity increased postvaccination (P = 0.04) but was not associated with antibody positivity. Conclusions: SARS-CoV-2 infection and vaccination (type and interval) impacted milk antibodies; however, antibody presence did not consistently predict live virus neutralization. Although human milk is unequivocally the best way to nourish infants, guidance on protection to infants following maternal infection/vaccination may require more nuanced messaging.

Current vaccine efforts to combat SARS-CoV-2 are focused on the whole spike protein administered as mRNA, viral vector, or protein subunit. However, the SARS-CoV-2 receptor-binding domain (RBD) is the immunodominant portion of the spike protein, accounting for 90% of serum neutralizing activity. In this study, we constructed several versions of RBD and together with aluminum hydroxide or DDA (dimethyldioctadecylammonium bromide)/TDB (d-(+)-trehalose 6,6'-dibehenate) adjuvant evaluated immunogenicity in mice. We generated human angiotensin-converting enzyme 2 knock-in mice to evaluate vaccine efficacy in vivo following viral challenge. We found that 1) subdomain (SD)1 was essential for the RBD to elicit maximal immunogenicity; 2) RBDSD1 produced in mammalian HEK cells elicited better immunogenicity than did protein produced in insect or yeast cells; 3) RBDSD1 combined with the CD4 Th1 adjuvant DDA/TDB produced higher neutralizing Ab responses and stronger CD4 T cell responses than did aluminum hydroxide; 4) addition of monomeric human Fc receptor to RBDSD1 (RBDSD1Fc) significantly enhanced immunogenicity and neutralizing Ab titers; 5) the Beta version of RBDSD1Fc provided a broad range of cross-neutralization to multiple antigenic variants of concern, including Omicron; and 6) the Beta version of RBDSD1Fc with DDA/TDB provided complete protection against virus challenge in the knock-in mouse model. Thus, we have identified an optimized RBD-based subunit vaccine suitable for clinical trials.

Older individuals and people with HIV (PWH) were prioritized for COVID-19 vaccination, yet comprehensive studies of the immunogenicity of these vaccines and their effects on HIV reservoirs are not available. We followed 68 PWH aged 55 and older and 23 age-matched HIV-negative individuals for 48 weeks from the first vaccine dose, after the total of three doses. All PWH were on antiretroviral therapy (cART) and had different immune status, including immune responders (IR), immune non-responders (INR), and PWH with low-level viremia (LLV). We measured total and neutralizing Ab responses to SARS-CoV-2 spike and RBD in sera, total anti-spike Abs in saliva, frequency of anti-RBD/NTD B cells, changes in frequency of anti-spike, HIV gag/nef-specific T cells, and HIV reservoirs in peripheral CD4 + T cells. The resulting datasets were used to create a mathematical model for within-host immunization. Various regimens of BNT162b2, mRNA-1273, and ChAdOx1 vaccines elicited equally strong anti-spike IgG responses in PWH and HIV - participants in serum and saliva at all timepoints. These responses had similar kinetics in both cohorts and peaked at 4 weeks post-booster (third dose), while half-lives of plasma IgG also dramatically increased post-booster in both groups. Salivary spike IgA responses were low, especially in INRs. PWH had diminished live virus neutralizing titers after two vaccine doses which were 'rescued' after a booster. Anti-spike T cell immunity was enhanced in IRs even in comparison to HIV - participants, suggesting Th1 imprinting from HIV, while in INRs it was the lowest. Increased frequency of viral 'blips' in PWH were seen post-vaccination, but vaccines did not affect the size of the intact HIV reservoir in CD4 + T cells in most PWH, except in LLVs. Thus, older PWH require three doses of COVID-19 vaccine to maximize neutralizing responses against SARS-CoV-2, although vaccines may increase HIV reservoirs in PWH with persistent viremia.

Safe and effective vaccines are needed to end the COVID-19 pandemic. Here, we report the preclinical development of a lipid nanoparticle–formulated SARS-CoV-2 mRNA vaccine, PTX-COVID19-B. PTX-COVID19-B was chosen among three candidates after the initial mouse vaccination results showed that it elicited the strongest neutralizing antibody response against SARS-CoV-2. Further tests in mice and hamsters indicated that PTX-COVID19-B induced robust humoral and cellular immune responses and completely protected the vaccinated animals from SARS-CoV-2 infection in the lung. Studies in hamsters also showed that PTX-COVID19-B protected the upper respiratory tract from SARS-CoV-2 infection. Mouse immune sera elicited by PTX-COVID19-B vaccination were able to neutralize SARS-CoV-2 variants of concern, including the Alpha, Beta, Gamma, and Delta lineages. No adverse effects were induced by PTX-COVID19-B in either mice or hamsters. Based on these results, PTX-COVID19-B was authorized by Health Canada to enter clinical trials in December 2020 with a phase 2 clinical trial ongoing.

Although SARS-CoV-2 infects the upper respiratory tract, we know little about the amount, type, and kinetics of antibodies (Ab) generated in the oral cavity in response to COVID-19 vaccination. We collected serum and saliva samples from participants receiving two doses of mRNA COVID-19 vaccines and measured the level of anti-SARS-CoV-2 Ab. We detected anti-Spike and anti-Receptor Binding Domain (RBD) IgG and IgA, as well as anti-Spike/RBD associated secretory component in the saliva of most participants after dose 1. Administration of a second dose of mRNA boosted the IgG but not the IgA response, with only 30% of participants remaining positive for IgA at this timepoint. At 6 months post-dose 2, these participants exhibited diminished anti-Spike/RBD IgG levels, although secretory component-associated anti-Spike Ab were more stable. Examining two prospective cohorts we found that participants who experienced breakthrough infections with SARS-CoV-2 variants had lower levels of vaccine-induced serum anti-Spike/RBD IgA at 2–4 weeks post-dose 2 compared to participants who did not experience an infection, whereas IgG levels were comparable between groups. These data suggest that COVID-19 vaccines that elicit a durable IgA response may have utility in preventing infection.

SARS-CoV-2 depends on host cell components for infection and replication. Identification of virus-host dependencies offers an effective way to elucidate mechanisms involved in viral infection and replication. If druggable, host factor dependencies may present an attractive strategy for anti-viral therapy. In this study, we performed genome wide CRISPR knockout screens in Vero E6 cells and four human cell lines including Calu-3, UM-UC-4, HEK-293 and HuH-7 to identify genetic regulators of SARS-CoV-2 infection. Our findings identified only ACE2, the cognate SARS-CoV-2 entry receptor, as a common host dependency factor across all cell lines, while other host genes identified were largely cell line specific, including known factors TMPRSS2 and CTSL. Several of the discovered host-dependency factors converged on pathways involved in cell signalling, immune-related pathways, and chromatin modification. Notably, the chromatin modifier gene KMT2C in Calu-3 cells had the strongest impact in preventing SARS-CoV-2 infection when perturbed.

There is a pressing need for an in-depth understanding of immunity to SARS-CoV-2. In this study, we investigated human T cell recall responses to fully glycosylated spike trimer, recombinant N protein, as well as to S, N, M, and E peptide pools in the early convalescent phase and compared them with influenza-specific memory responses from the same donors. All subjects showed SARS-CoV-2-specific T cell responses to at least one Ag. Both SARS-CoV-2-specific and influenza-specific CD4+ T cell responses were predominantly of the central memory phenotype; however SARS-CoV-2-specific CD4+ T cells exhibited a lower IFN-γ to TNF ratio compared with influenza-specific memory responses from the same donors, independent of disease severity. SARS-CoV-2-specific T cells were less multifunctional than influenza-specific T cells, particularly in severe cases, potentially suggesting exhaustion. Most SARS-CoV-2-convalescent subjects also produced IFN-γ in response to seasonal OC43 S protein. We observed granzyme B+/IFN-γ+, CD4+, and CD8+ proliferative responses to peptide pools in most individuals, with CD4+ T cell responses predominating over CD8+ T cell responses. Peripheral T follicular helper (pTfh) responses to S or N strongly correlated with serum neutralization assays as well as receptor binding domain-specific IgA; however, the frequency of pTfh responses to SARS-CoV-2 was lower than the frequency of pTfh responses to influenza virus. Overall, T cell responses to SARS-CoV-2 are robust; however, CD4+ Th1 responses predominate over CD8+ T cell responses, have a more inflammatory profile, and have a weaker pTfh response than the response to influenza virus within the same donors, potentially contributing to COVID-19 disease.

Baweleta Isho1†, Kento T. Abe2,3†, Michelle Zuo1†, Alainna J. Jamal4,5†, Bhavisha Rathod2, Jenny H. Wang2, Zhijie Li3, Gary Chao1, Olga L. Rojas1, Yeo Myong Bang1, Annie Pu1, Natasha Christie-Holmes6, Christian Gervais7, Derek Ceccarelli2, Payman Samavarchi-Tehrani2, Furkan Guvenc3, Patrick Budylowski6,8, Angel Li5, Aimee Paterson5, Yue Feng Yun1, Lina M. Marin9, Lauren Caldwell2, Jeffrey L. Wrana2,3, Karen Colwill2, Frank Sicheri2,3, Samira Mubareka10,11,12,13, Scott D. Gray-Owen3,6, Steven J. Drews14,15, Walter L. Siqueira9, Miriam Barrios-Rodiles2, Mario Ostrowski1,16,17,18, James M. Rini3,19, Yves Durocher7, Allison J. McGeer2,4,5, Jennifer L. Gommerman1*, Anne-Claude Gingras2,3*

Vaccines against SARS-CoV-2 administered via the parenteral route (intra-muscular = i.m.) are effective at preventing COVID-19 in part by inducing neutralizing antibodies in the blood. The first line of defense against SARS-CoV-2 is in the upper respiratory tract, yet we know very little about whether COVID-19 vaccines induce immunity in this compartment, if at all. We analysed salivary antibodies against the SARS-CoV-2 Spike protein and its receptor binding domain (RBD) following 2 i.m. injections of either BNT162b2 or mRNA-1273 vaccines. Salivary anti-Spike/RBD IgG was detected after 1 dose and increased further after dose 2, reflecting the systemic immune response. Interestingly, salivary anti-Spike/RBD IgA associated with the secretory component (sIgA) was detected in nearly all vaccinated participants after one dose of mRNA vaccine, with anti-Spike sIgA diminishing after dose 2. Vaccination with ChAdOx1-S (Ad) followed by mRNA induced similar levels of salivary anti-Spike/RBD IgG and IgA, and both mRNA/mRNA and Ad/mRNA regimes provoked modest neutralizing capacity in this biofluid. Our results demonstrate that SARS-CoV-2 mRNA/mRNA and Ad/mRNA vaccination induces antibodies in the saliva, and in response to one dose of mRNA, a compartmentalized and transient antigen-specific sIgA response is generated that does not correlate with systemic immunity.

Background: The COVID-19 pandemic highlighted the need for evidence-based approaches to decontamination and reuse of N95 filtering facepiece respirators (FFRs). We sought to determine whether vapourized hydrogen peroxide (VHP) reduced SARS-CoV-2 bioburden on FFRs without compromising filtration efficiency. We also investigated coronavirus HCoV-229E as a surrogate for decontamination validation testing. Methods: N95 FFRs were laced with SARS-CoV-2 or HCoV-229E and treated with VHP in a hospital reprocessing facility. After sterilization, viral burden was determined using viral outgrowth in a titration assay, and filtration efficiency of FFRs was tested against ATSM F2299 and NIOSH TEB-STP-APR-0059. Results: Viable SARS-CoV-2 virus was not detected after VHP treatment. One replicate of the HCoV-229E laced FFRs yielded virus after processing. Unexpired N95 FFRs retained full filtration efficiency after VHP processing. Expired FFRs failed to meet design-specified filtration efficiency and therefore are unsuitable for reprocessing. Discussion: In-hospital VHP is an effective decontaminant for SARS-CoV-2 on FFRs. Further, filtration efficiency of unexpired respirators is not affected by this decontamination process. Conclusions: VHP is effective in inactivating SARS-CoV-2 on FFRs without compromising filtration efficiency. HCoV-229E is a suitable surrogate for SARS-CoV-2 for disinfection studies. (c) 2021 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.

SARS-CoV-2, the virus responsible for COVID-19, has caused a global pandemic. Antibodies can be powerful biotherapeutics to fight viral infections. Here, we use the human apoferritin protomer as a modular subunit to drive oligomerization of antibody fragments and transform antibodies targeting SARS-CoV-2 into exceptionally potent neutralizers. Using this platform, half-maximal inhibitory concentration (IC 50 ) values as low as 9 × 10 − 14 M are achieved as a result of up to 10,000-fold potency enhancements compared to corresponding IgGs. Combination of three different antibody specificities and the fragment crystallizable (Fc) domain on a single multivalent molecule conferred the ability to overcome viral sequence variability together with outstanding potency and IgG-like bioavailability. The MULTi-specific, multi-Affinity antiBODY (Multabody or MB) platform thus uniquely leverages binding avidity together with multi-specificity to deliver ultrapotent and broad neutralizers against SARS-CoV-2. The modularity of the platform also makes it relevant for rapid evaluation against other infectious diseases of global health importance. Neutralizing antibodies are a promising therapeutic for SARS-CoV-2.

Type I interferons (IFNs) are our first line of defense against virus infection. Recent studies have suggested the ability of SARS-CoV-2 proteins to inhibit IFN responses. Emerging data also suggest that timing and extent of IFN production is associated with manifestation of COVID-19 severity. In spite of progress in understanding how SARS-CoV-2 activates antiviral responses, mechanistic studies into wild-type SARS-CoV-2-mediated induction and inhibition of human type I IFN responses are scarce. Here we demonstrate that SARS-CoV-2 infection induces a type I IFN response in vitro and in moderate cases of COVID-19. In vitro stimulation of type I IFN expression and signaling in human airway epithelial cells is associated with activation of canonical transcriptions factors, and SARS-CoV-2 is unable to inhibit exogenous induction of these responses. Furthermore, we show that physiological levels of IFNα detected in patients with moderate COVID-19 is sufficient to suppress SARS-CoV-2 replication in human airway cells.