Non-neutralizing SARS CoV-2 directed polyclonal antibodies demonstrate cross-reactivity with the HA glycans of influenza virus

Detection of SARS-CoV-2 Antibodies: Comparison of Enzyme Immunoassay, Surrogate Neutralization and Virus Neutralization Test

BACKGROUND

Since sensitivity and specificity vary widely between tests, SARS-CoV-2 serology results should be interpreted with caution.

METHODS

The study included serum samples from patients who had recovered from COVID-19 (n = 71), individuals vaccinated against SARS-CoV-2 (n = 84), and asymptomatic individuals (n = 33). All samples were tested for the presence of binding antibodies (enzyme immunoassay; EIA), neutralizing (NT) antibodies (virus neutralization test; VNT), and surrogate NT (sNT) antibodies (surrogate virus neutralization test; sVNT) of SARS-CoV-2.

RESULTS

SARS-CoV-2-binding antibodies were detected in 71 (100%) COVID-19 patients, 77 (91.6%) vaccinated individuals, and 4 (12.1%) control subjects. Among EIA-positive samples, VNT was positive (titer ≥ 8) in 100% of COVID-19 patients and 63 (75.0%) of the vaccinated individuals, while sVNT was positive (>30% inhibition) in 62 (87.3%) patients and 59 (70.2%) vaccinated individuals. The analysis of antibody levels showed a significant moderate positive correlation between EIA and VNT, a moderate positive correlation between EIA and sVNT, and a strong positive correlation between VNT and sVNT. The proportion of positive sVNT detection rate was associated with VNT titer. The lowest positivity (72.4%/70.8%) was detected in samples with low NT titers (8/16) and increased progressively from 88.2% in samples with titer 32 to 100% in samples with titer 256.

CONCLUSIONS

sVNT appeared to be a reliable method for the assessment COVID-19 serology in patients with high antibody levels, while false-negative results were frequently observed in patients with low NT titers.

Immune interference in effectiveness of influenza and COVID-19 vaccination

Vaccines are known to function as the most effective interventional therapeutics for controlling infectious diseases, including polio, smallpox, rabies, tuberculosis, influenza and SARS-CoV-2. Smallpox has been eliminated completely and polio is almost extinct because of vaccines. Rabies vaccines and Bacille Calmette-Guérin (BCG) vaccines could effectively protect humans against respective infections. However, both influenza vaccines and COVID-19 vaccines are unable to eliminate these two infectious diseases of their highly variable antigenic sites in viral proteins. Vaccine effectiveness (VE) could be negatively influenced (i.e., interfered with) by immune imprinting of previous infections or vaccinations, and repeated vaccinations could interfere with VE against infections due to mismatch between vaccine strains and endemic viral strains. Moreover, VE could also be interfered with when more than one kind of vaccine is administrated concomitantly (i.e., co-administrated), suggesting that the VE could be modulated by the vaccine-induced immunity. In this review, we revisit the evidence that support the interfered VE result from immune imprinting or repeated vaccinations in influenza and COVID-19 vaccine, and the interference in co-administration of these two types of vaccines is also discussed. Regarding the development of next-generation COVID-19 vaccines, the researchers should focus on the induction of cross-reactive T-cell responses and naive B-cell responses to overcome negative effects from the immune system itself. The strategy of co-administrating influenza and COVID-19 vaccine needs to be considered more carefully and more clinical data is needed to verify this strategy to be safe and immunogenic.

Performance and correlation of ten commercial immunoassays for the detection of SARS-CoV-2 antibodies

Accurate immunoassays with a good correlation to neutralizing antibodies are required to support SARS-CoV-2 diagnosis, management, vaccine deployment, and epidemiological investigation. We conducted a study to evaluate the performance and correlation of the surrogate virus neutralization test (sVNT) and other commercial immunoassays. We tested 107 sera of COVID-19 confirmed cases from three different time points, 58 confirmed non-COVID-19 sera, and 52 sera collected before the pandemic with two sVNTs, seven chemiluminescent assays, and one fluorescein assay. All assays achieved excellent sensitivity (95%-100%, ≥15 days after onset of illness), specificity (95.5%-100%), and showed moderate to high correlation with GenScript sVNT (r = 0.58 to r = 0.98), except Roche total antibodies (r = 0.48). Vazyme sVNT and Siemens total antibodies showed the highest correlation with GenScript sVNT (r = 0.98 and 0.88, respectively). Median indexes that may be used to estimate sera with the highest ability to inhibit SARS-CoV-2 and ACE-2 receptor attachment (GenScript sVNT inhibition 90%-100%) were 6.9 S/C (Abbott IgG), 161.9 COI (FREND™ IgG), 16.8 AU/ml (Snibe IgG), 40.1 S/CO (Beckman IgG), 281.9 U/ml (Mindray IgG), 712.2 U/ml (Mindray total antibodies), >10 index (Siemens total antibodies), and 95.3% inhibition (Vazyme sVNT). All ten commercial COVID-19 serology assays, with different targeting antigens, demonstrated a reliable performance, supporting the utility of those assays in clinical and research settings. However, further studies using more samples are needed to refine the results of evaluating the performances of these marketed serological assays. Reliable serological assays would be useful for clinicians, researchers and epidemiologists in confirming SARS-CoV-2 infections, observing SARS-CoV-2 transmission, and immune response post infection and vaccination, leading to better management and control of the disease.

SARS-CoV-2 Spike Protein-Activated Dendritic Cell-Derived Extracellular Vesicles Induce Antiviral Immunity in Mice

The onset and spread of the SARS-CoV-2 virus have created an unprecedented universal crisis. Although vaccines have been developed against the parental SARS-CoV-2, outbreaks of the disease still occur through the appearance of different variants, suggesting a continuous need for improved and effective therapeutic strategies. Therefore, we developed a novel nanovesicle presenting Spike protein on the surface of the dendritic cell-derived extracellular vesicles (DEVs) for use as a potential vaccine platform against SARS-CoV-2. DEVs express peptide/MHC-I (pMHC-I) complexes, CCR-7, on their surface. The immunogenicity and efficacy of the Spike-activated DEVs were tested in mice and compared with free Spike protein. A 1/10 Spike equivalent dose of DEVs showed a superior potency in inducing anti-Spike IgG titers in blood of mice when compared to dendritic cells or free Spike protein treatment. Moreover, DEV-induced sera effectively reduced viral infection by 55-60% within 15 days of booster dose administration. Furthermore, a 1/10 Spike equivalent dose of DEV-treated mice was found to be equally effective in inducing CD19+CD38+ T-cells in the spleen and lymph node; CD8 cells in the bone marrow, spleen, and lymph node; and CD4+CD25+ T-cells in the spleen and lymph node after 90 days of treatment. Thus, our results support the immunogenic nature of DEVs, demonstrating that a low dose of DEVs induces antibodies to inhibit SARS-CoV-2 infection in vitro, therefore warranting further investigations.

A broadly neutralizing monoclonal antibody overcomes the mutational landscape of emerging SARS-CoV-2 variants of concern

The emergence of new variants of SARS-CoV-2 necessitates unremitting efforts to discover novel therapeutic monoclonal antibodies (mAbs). Here, we report an extremely potent mAb named P4A2 that can neutralize all the circulating variants of concern (VOCs) with high efficiency, including the highly transmissible Omicron. The crystal structure of the P4A2 Fab:RBD complex revealed that the residues of the RBD that interact with P4A2 are a part of the ACE2-receptor-binding motif and are not mutated in any of the VOCs. The pan coronavirus pseudotyped neutralization assay confirmed that the P4A2 mAb is specific for SARS-CoV-2 and its VOCs. Passive administration of P4A2 to K18-hACE2 transgenic mice conferred protection, both prophylactically and therapeutically, against challenge with VOCs. Overall, our data shows that, the P4A2 mAb has immense therapeutic potential to neutralize the current circulating VOCs. Due to the overlap between the P4A2 epitope and ACE2 binding site on spike-RBD, P4A2 may also be highly effective against a number of future variants.

Virus-Like Particles of SARS-CoV-2 as Virus Surrogates: Morphology, Immunogenicity, and Internalization in Neuronal Cells

The engineering of virus-like particles (VLPs) is a viable strategy for the development of vaccines and for the identification of therapeutic targets without using live viruses. Here, we report the generation and characterization of quadruple-antigen SARS-CoV-2 VLPs. VLPs were generated by transient transfection of two expression cassettes in adherent HEK293T cells─one cassette containing Mpro for processing of three structural proteins (M, E, and N), and the second cassette expressing the Spike protein. Further characterization revealed that the VLPs retain close morphological and antigenic similarity with the native virus and also bind strongly to the SARS-CoV-2 receptor hACE-2 in an in vitro binding assay. Interestingly, the VLPs were found to internalize into U87-MG cells through cholesterol-rich domains in a dynamin-dependent process. Finally, our results showed that mice immunized with VLPs induce robust humoral and cellular immune responses mediated by enhanced levels of IL-4, IL-17, and IFNγ. Taken together, our results demonstrate that VLPs mimic the native virus and induce a strong immune response, indicating the possible use of these particles as an alternative vaccine candidate against SARS-CoV-2. VLPs can also be effective in mapping the initial stages of virus entry and screening inhibitors.

Non-neutralizing antibodies: Deleterious or propitious during SARS-CoV-2 infection?

Antibody-dependent enhancement (ADE) is a complex phenomenon mediated by antibodies, frequently pre-existing non-neutralizing or sub-neutralizing antibodies. In the course of infectious diseases, ADE may be responsible for worsening the clinical course of the disease by increasing the virulence of pathogens (ADE of infection) or enhancing disease severity (ADE of disease). Here we reviewed the mechanisms thought to be behind the ADE phenomenon and its potential relationship with COVID-19 severity. Since the early COVID-19 epidemics, ADE has been mentioned as a possible mechanism involved in severe COVID-19 disease and, later, as a potential risk in the case of infection after vaccination. However, current data do not support its role in disease severity, both after infection and reinfection.

Immunogenicity and Protective Efficacy of a Recombinant Pichinde Viral-Vectored Vaccine Expressing Influenza Virus Hemagglutinin Antigen in Pigs

Influenza A virus of swine (IAV-S) is an economically important swine pathogen. The IAV-S hemagglutinin (HA) surface protein is the main target for vaccine development. In this study, we evaluated the feasibility of using the recombinant tri-segmented Pichinde virus (rPICV) as a viral vector to deliver HA antigen to protect pigs against IAV-S challenge. Four groups of weaned pigs (T01–T04) were included in the study. T01 was injected with PBS to serve as a non-vaccinated control. T02 was inoculated with rPICV expressing green fluorescence protein (rPICV-GFP). T03 was vaccinated with rPICV expressing the HA antigen of the IAV-S H3N2 strain (rPICV-H3). T04 was vaccinated with the recombinant HA protein antigen of the same H3N2 strain. Pigs were vaccinated twice at day 0 and day 21 and challenged at day 43 by intra-tracheal inoculation with the homologous H3N2 IAV-S strain. After vaccination, all pigs in T03 and T04 groups were seroconverted and exhibited high titers of plasma neutralizing antibodies. After challenge, high levels of IAV-S RNA were detected in the nasal swabs and bronchioalveolar lavage fluid of pigs in T01 and T02 but not in the T03 and T04 groups. Similarly, lung lesions were observed in T01 and T02, but not in the T03 and T04 groups. No significant difference in terms of protection was observed between the T03 and T04 group. Collectively, our results demonstrate that the rPICV-H3 vectored vaccine elicited protective immunity against IAV-S challenge. This study shows that rPICV is a promising viral vector for the development of vaccines against IAV-S.

Multi Epitope-Based Vaccine Design for Protection Against Mycobacterium tuberculosis and SARS-CoV-2 Coinfection

Background

A prophylactic and immunotherapeutic vaccine for Mycobacterium tuberculosis (MTB) and SARS-CoV-2 coinfection needs to be developed for a proactive and effective therapeutic approach. Therefore, this study aims to use immunoinformatics to design a multi-epitope vaccine for protection against MTB and SARS-CoV-2 coinfection.

Methods

The bioinformatic techniques were used to screen and construct potential epitopes from outer membrane protein A Rv0899 of MTB and spike glycoprotein of SARS-CoV-2 for B and T cells. The antigenicity, allergenicity, and several physiochemical properties of the developed multi-epitope vaccination were then evaluated. Additionally, molecular docking and normal mode analysis (NMA) were utilized in evaluating the vaccine’s immunogenicity and complex stability.

Results

Selected proteins and predicted epitopes suggest that the vaccine prediction can be helpful in the protection against both SARS-CoV-2 and MTB coinfection. Through docking molecular and NMA, the vaccine-TLR4 protein interaction was predicted to be efficient with a high level of IgG, T-helper cells, T-cytotoxic cells, andIFN-γ.

Conclusion

This epitope-based vaccine is a potentially attractive tool for SARS-CoV-2 and MTB coinfection vaccine development.

Effect of the 2020/21 season influenza vaccine on SARS-CoV-2 infection in a cohort of Italian healthcare workers

OBJECTIVES

Healthcare workers (HCWs) are a priority group for seasonal influenza vaccination (SIV). The 2020/21 SIV campaign was conducted during the second wave of the COVID-19 pandemic. Vaccines, including SIV, may exert non-specific protective effects on other infectious diseases which may be ascribable to the concept of trained immunity. The aim of this study was to explore the association between 2020/21 SIV and SARS-CoV-2 positivity in a cohort of Italian HCWs.

METHODS

In this observational study, a cohort of HCWs employed by a large (ca 5000 employees) referral tertiary acute-care university hospital was followed up retrospectively until the start of the COVID-19 vaccination campaign. The independent variable of interest was the 2020/21 SIV uptake. Both egg-based and cell culture-derived quadrivalent SIVs were available. The study outcome was the incidence of new SARS-CoV-2 infections, as determined by RT-PCR. Multivariable Cox regression was applied in order to discern the association of interest.

RESULTS

The final cohort consisted of 2561 HCWs who underwent ≥1 RT-PCR test and accounted for a total of 94,445 person-days of observation. SIV uptake was 35.6%. During the study period, a total of 290 new SARS-CoV-2 infections occurred. The incidence of new SARS-CoV-2 was 1.62 (95% CI: 1.22-2.10) and 3.91 (95% CI: 3.43-4.45) per 1000 person-days in vaccinated and non-vaccinated HCWs, respectively, with an adjusted non-proportional hazard ratio of 0.37 (95% CI: 0.22-0.62). E-values suggested that unmeasured confounding was unlikely to explain the association.

CONCLUSIONS

A lower risk of SARS-CoV-2 infection was observed among SIV recipients.

COVID-19 and Seasonal Influenza Vaccination: Cross-Protection, Co-Administration, Combination Vaccines, and Hesitancy

SARS-CoV-2 and influenza are the main respiratory viruses for which effective vaccines are currently available. Strategies in which COVID-19 and influenza vaccines are administered simultaneously or combined into a single preparation are advantageous and may increase vaccination uptake. Here, we comprehensively review the available evidence on COVID-19/influenza vaccine co-administration and combination vaccine candidates from the standpoints of safety, immunogenicity, efficacy, policy and public acceptance. While several observational studies have shown that the trained immunity induced by influenza vaccines can protect against some COVID-19-related endpoints, it is not yet understood whether co-administration or combination vaccines can exert additive effects on relevant outcomes. In randomized controlled trials, co-administration has proved safe, with a reactogenicity profile similar to that of either vaccine administered alone. From the immunogenicity standpoint, the immune response towards four influenza strains and the SARS-CoV-2 spike protein in co-administration groups is generally non-inferior to that seen in groups receiving either vaccine alone. Several public health authorities have advocated co-administration. Different combination vaccine candidates are in (pre)-clinical development. The hesitancy towards vaccine co-administration or combination vaccines is a multifaceted phenomenon and may be higher than the acceptance of either vaccine administered separately. Public health implications are discussed.

The SARS CoV-2 spike directed non-neutralizing polyclonal antibodies cross-react with Human immunodeficiency virus (HIV-1) gp41

Cross-reactivity among the two diverse viruses is believed to originate from the concept of antibodies recognizing similar epitopes on the two viral surfaces. Cross-reactive antibody responses have been seen in previous variants of SARS and SARS-CoV-2, but little is known about the cross reactivity with other similar RNA viruses like HIV-1. In the present study, we examined the reactivity the SARS-CoV-2 directed antibodies, via spike, immunized mice sera and demonstrated whether they conferred any cross-reactive neutralization against HIV-1. Our findings show that SARS-CoV-2 spike immunized mice antibodies cross-react with the HIV-1 Env protein. Cross-neutralization among the two viruses is uncommon, suggesting the presence of a non-neutralizing antibody response to conserved epitopes amongst the two viruses. Our results indicate, that SARS-CoV-2 spike antibody cross reactivity is targeted towards the gp41 region of the HIV-1 Env (gp160) protein. Overall, our investigation not only answers a crucial question about the understanding of cross-reactive epitopes of antibodies generated in different viral infections, but also provides critical evidence for developing vaccine immunogens and novel treatment strategies with enhanced efficacy capable of recognising diverse pathogens with similar antigenic features.