Correction: DNA vaccination induced protective immunity against SARS CoV-2 infection in hamsterss.

[This corrects the article DOI: 10.1371/journal.pntd.0009374.].

A DNA vaccine candidate delivered by an electroacupuncture machine provides protective immunity against SARS-CoV-2 infection.

A major challenge in the use of DNA vaccines is efficient DNA delivery in vivo. Establishing a safe and efficient electric transfer method is the key to developing rapid DNA vaccines against emerging infectious diseases. To overcome the complexity of designing new electric transfer machines for DNA delivery, a clinically approved electric transfer machine could be considered as an alternative. Here, we report an electroacupuncture machine-based method for DNA vaccine delivery after intramuscular injection of the COVID-19 DNA vaccine. The S gene of SARS-CoV-2 in the pVAX1 plasmid (pSARS2-S) was used as an antigen in this study. We optimized the clinically used electroacupuncture machine settings for efficient induction of the neutralizing antibody titer after intramuscular injection of pSARS2-S in mice. We found that pSARS2-S immunization at 40 Vpp for 3-5 s could induce high neutralizing antibody titers and Th1-biased immune responses. IFN-γ/TNF-α-secreting CD4+ and CD8+ T cells were also observed in the DNA vaccination group but not in the recombinant protein vaccination group. T-cell epitope mapping shows that the major reactive epitopes were located in the N-terminal domain (a.a. 261-285) and receptor-binding domain (a.a. 352-363). Importantly, pSARS2-S immunization in hamsters could induce protective immunity against SARS-CoV-2 challenge in vivo. In the preclinical toxicology study, blood biochemistry, hematology, and DNA persistence analysis reveal that the DNA delivery method is safe. Furthermore, the raised antisera could also cross-neutralize different variants of concern. These findings suggest that DNA vaccination using an electroacupuncture machine is feasible for use in humans in the future.

Furin and TMPRSS2 Resistant Spike Induces Robust Humoral and Cellular Immunity Against SARS-CoV-2 Lethal Infection.

An effective COVID-19 vaccine against broad SARS-CoV-2 variants is still an unmet need. In the study, the vesicular stomatitis virus (VSV)-based vector was used to express the SARS-CoV-2 Spike protein to identify better vaccine designs. The replication-competent of the recombinant VSV-spike virus with C-terminal 19 amino acid truncation (SΔ19 Rep) was generated. A single dose of SΔ19 Rep intranasal vaccination is sufficient to induce protective immunity against SARS-CoV-2 infection in hamsters. All the clones isolated from the SΔ19 Rep virus contained R682G mutation located at the Furin cleavage site. An additional S813Y mutation close to the TMPRSS2 cleavage site was identified in some clones. The enzymatic processing of S protein was blocked by these mutations. The vaccination of the R682G-S813Y virus produced a high antibody response against S protein and a robust S protein-specific CD8+ T cell response. The vaccinated animals were protected from the lethal SARS-CoV-2 (delta variant) challenge. The S antigen with resistance to enzymatic processes by Furin and TMPRSS2 will provide better immunogenicity for vaccine design.

Induction of Th1 and Th2 in the protection against SARS-CoV-2 through mucosal delivery of an adenovirus vaccine expressing an engineered spike protein.

A series of recombinant human type 5 adenoviruses that express the full-length or membrane-truncated spike protein (S) of SARS-CoV-2 (AdCoV2-S or AdCoV2-SdTM, respectively) was tested the efficacy against SARS-CoV-2 via intranasal (i.n.) or subcutaneous (s.c.) immunization in a rodent model. Mucosal delivery of adenovirus (Ad) vaccines could induce anti-SARS-CoV-2 IgG and IgA in the serum and in the mucosal, respectively as indicated by vaginal wash (vw) and bronchoalveolar lavage fluid (BALF). Serum anti-SARS-CoV-2 IgG but not IgA in the vw and BALF was induced by AdCoV2-S s.c.. Administration of AdCoV2-S i.n. was able to induce higher anti-SARS-CoV-2 binding and neutralizing antibody levels than s.c. injection. AdCoV2-SdTM i.n. induced a lower antibody responses than AdCoV2-S i.n.. Induced anti-S antibody responses by AdCoV2-S via i.n. or s.c. were not influenced by the pre-existing serum anti-Ad antibody. Novelty, S-specific IgG1 which represented Th2-mediated humoral response was dominantly induced in Ad i.n.-immunized serum in contrast to more IgG2a which represented Th1-mediated cellular response found in Ad s.c.-immunized serum. The activation of S-specific IFN-É£ and IL-4 in splenic Th1 and Th2 cells, respectively, was observed in the AdCoV2-S i.n. and s.c. groups, indicating the Th1 and Th2 immunity were activated. AdCoV2-S and AdCoV2-SdTM significantly prevented body weight loss and reduced pulmonary viral loads in hamsters. A reduction in inflammation in the lungs was observed in AdCoV-S via i.n. or s.c.-immunized hamsters following a SARS-CoV-2 challenge. It correlated to Th1 cytokine but no inflammatory cytokines secretions found in AdCoV-S i.n. -immunized BALF. These results indicate that intranasal delivery of AdCoV2-S vaccines is safe and potent at preventing SARS-CoV-2 infections.

Characterization of Virus Replication, Pathogenesis, and Cytokine Responses in Syrian Hamsters Inoculated with SARS-CoV-2.

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel coronavirus which caused a global respiratory disease pandemic beginning in December 2019. Understanding the pathogenesis of infection and the immune responses in a SARS-CoV-2-infected animal model is urgently needed for vaccine development. METHODS: Syrian hamsters (Mesocricetus auratus) were intranasally inoculated with 105, 5×105, and 106 TCID50 of SARS-CoV-2 per animal and studied for up to 14 days. Body weight, viral load and real-time PCR amplification of the SARS-CoV-2 N gene were measured. On days 3, 6 and 9, lung, blood, liver, pancreas, heart, kidney, and bone marrow were harvested and processed for pathology, viral load, and cytokine expression. RESULTS: Body weight loss, increased viral load, immune cell infiltration, upregulated cytokine expression, viral RNA, SARS-CoV-2 nucleoprotein, and mucus were detected in the lungs, particularly on day 3 post-infection. Extremely high expression of the pro-inflammatory cytokines MIP-1 and RANTES was detected in lung tissue, as was high expression of IL-1ß, IL-6, IL-12, and PD-L1. The glutamic oxalacetic transaminase/glutamic pyruvic transaminase (GOT/GPT) ratio in blood was significantly increased at 6 days post-infection, and plasma amylase and lipase levels were also elevated in infected hamsters. CONCLUSION: Our results provide new information on immunological cytokines and biological parameters related to the pathogenesis and immune response profile in the Syrian hamster model of SARS-CoV-2 infection.

DNA vaccination induced protective immunity against SARS CoV-2 infection in hamsterss.

The development of efficient vaccines against COVID-19 is an emergent need for global public health. The spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a major target for the COVID-19 vaccine. To quickly respond to the outbreak of the SARS-CoV-2 pandemic, a nucleic acid-based vaccine is a novel option, beyond the traditional inactivated virus vaccine or recombinant protein vaccine. Here, we report a DNA vaccine containing the spike gene for delivery via electroporation. The spike genes of SARS-CoV and SARS-CoV-2 were codon optimized for mammalian cell expression and then cloned into mammalian cell expression vectors, called pSARS-S and pSARS2-S, respectively. Spike protein expression was confirmed by immunoblotting after transient expression in HEK293T cells. After immunization, sera were collected for antigen-specific antibody and neutralizing antibody titer analyses. We found that both pSARS-S and pSARS2-S immunization induced similar levels of antibodies against S2 of SARS-CoV-2. In contrast, only pSARS2-S immunization induced antibodies against the receptor-binding domain of SARS-CoV-2. We further found that pSARS2-S immunization, but not pSARS-S immunization, could induce very high titers of neutralizing antibodies against SARS-CoV-2. We further analyzed SARS-CoV-2 S protein-specific T cell responses and found that the immune responses were biased toward Th1. Importantly, pSARS2-S immunization in hamsters could induce protective immunity against SARS-CoV-2 challenge in vivo. These data suggest that DNA vaccination could be a promising approach for protecting against COVID-19.