Evaluation of the humoral and mucosal immune response of a multiepitope vaccine against COVID-19 in pigs

Introduction

This study evaluated the immune response to a multiepitope recombinant chimeric protein (CHIVAX) containing B- and T-cell epitopes of the SARS-CoV-2 spike's receptor binding domain (RBD) in a translational porcine model for pre-clinical studies.

Methods

We generated a multiepitope recombinant protein engineered to include six coding conserved epitopes from the RBD domain of the SARS-CoV-2 S protein. Pigs were divided into groups and immunized with different doses of the protein, with serum samples collected over time to determine antibody responses by indirect ELISA and antibody titration. Peptide recognition was also analyzed by Western blotting. A surrogate neutralization assay with recombinant ACE2 and RBDs was performed. Intranasal doses of the immunogen were also prepared and tested on Vietnamese minipigs.

Results

When the immunogen was administered subcutaneously, it induced specific IgG antibodies in pigs, and higher doses correlated with higher antibody levels. Antibodies from immunized pigs recognized individual peptides in the multiepitope vaccine and inhibited RBD-ACE2 binding for five variants of concern (VOC). Comparative antigen delivery methods showed that both, subcutaneous and combined subcutaneous/intranasal approaches, induced specific IgG and IgA antibodies, with the subcutaneous approach having superior neutralizing activity. CHIVAX elicited systemic immunity, evidenced by specific IgG antibodies in the serum, and local mucosal immunity, indicated by IgA antibodies in saliva, nasal, and bronchoalveolar lavage secretions. Importantly, these antibodies demonstrated neutralizing activity against SARS-CoV-2 in vitro.

Discussion

The elicited antibodies recognized individual epitopes on the chimeric protein and demonstrated the capacity to block RBD-ACE2 binding of the ancestral SARS-CoV-2 strain and four VOCs. The findings provide proof of concept for using multiepitope recombinant antigens and a combined immunization protocol to induce a neutralizing immune response against SARS-CoV-2 in the pig translational model for preclinical studies.

A Retrospective Analysis of Porcine Circovirus Type 3 in Samples Collected from 2008 to 2021 in Mexico

Porcine circovirus type 3 (PCV3) is a nonenveloped virus of the Circoviridae family. This virus has been identified in pigs of different ages and pigs with several clinical manifestations of the disease or even in apparently healthy pigs. While PCV3 was first reported in 2015, several retrospective studies have reported the virus before that year. The earliest report indicates that PCV3 has been circulated in swine farms since 1996. In this study, we evaluated the presence of PCV3 in samples collected in Mexico in 2008, 2015, 2020, and 2021. This study assessed PCV3 DNA by qPCR and antibodies against CAP protein by indirect ELISA. The results showed that PCV3 (DNA and anti-CAP antibodies) was detected in the samples collected from 2008 to 2021. The highest prevalence was in 2008 (100%), and the lowest was in 2015 (negative). Genetic analysis of ORF2 showed that the virus identified belonged to genotype a, as most of the viruses identified thus far. PCV3 was detected in samples from piglets with respiratory signs and growth retardation, sows with reproductive failure, or asymptomatic piglets and sows. Pigs with respiratory signs, growth retardation, or reproductive failure had a higher prevalence of antibodies and qPCR-positive samples. In conclusion, this study showed that PCV3 has been circulating in Mexico since 2008 and that PCV3 DNA and antibodies were more prevalent in samples from pigs with clinical manifestations of diseases.

19n01, a broadly neutralizing antibody against Omicron BA.1, BA.2, BA.4/5, and other SARS-CoV-2 variants of concern

This study reports the isolation and characterization of a human monoclonal antibody (mAb) called 19n01. This mAb was isolated by using single-cell RNAseq of B cells from donors infected with the ancestral strain. This mAb possesses a potent and broad capacity to bind and neutralize all previously circulating variants of concern (VOCs), including Omicron sublineages BA.1, BA.2, and BA.4/5. The pseudovirus neutralization assay revealed robust neutralization capacity against the G614 strain, BA.1, BA.2, and BA.4/5, with inhibitory concentration (IC50) values ranging from 0.0035 to 0.0164 μg/mL. The microneutralization assay using the G614 strain and VOCs demonstrated IC50 values of 0.013-0.267 μg/mL. Biophysical and structural analysis showed that 19n01 cross-competes with ACE2 binding to the receptor-binding domain (RBD) and the kinetic parameters confirmed the high affinity against the Omicron sublineages (K_D of 61 and 30 nM for BA.2 and BA.4/5, respectively). These results suggest that the 19n01 is a remarkably potent and broadly reactive mAb.

Analysis of IgG, IgA and IgM antibodies against SARS-CoV-2 spike protein S1 in convalescent and vaccinated patients with the Pfizer-BioNTech and CanSinoBio vaccines

The SARS‐CoV‐2 virus was detected for the first time in December 2019 in Wuhan, China. Currently, this virus has spread around the world, and new variants have emerged. This new pandemic virus provoked the rapid development of diagnostic tools, therapies and vaccines to control this new disease called COVID‐19. Antibody detection by ELISA has been broadly used to recognize the number of persons infected with this virus or to evaluate the response of vaccinated individuals. As the pandemic spread, new questions arose, such as the prevalence of antibodies after natural infection and the response induced by the different vaccines. In Mexico, as in other countries, mRNA and viral‐vectored vaccines have been widely used among the population. In this work, we developed an indirect ELISA test to evaluate S1 antibodies in convalescent and vaccinated individuals. By using this test, we showed that IgG antibodies against the S1 protein of SARS‐CoV‐2 were detected up to 42 weeks after the onset of the symptoms, in contrast to IgA and IgM, which decreased 14 weeks after the onset of symptoms. The evaluation of the antibody response in individuals vaccinated with Pfizer‐BioNTech and CanSinoBio vaccines showed no differences 2 weeks after vaccination. However, after completing the two doses of Pfizer‐BioNTech and the one dose of CanSinoBio, a significantly higher response of IgG antibodies was observed in persons vaccinated with Pfizer‐BioNTech than in those vaccinated with CanSinoBio. In conclusion, these results confirm that after natural infection with SARS‐CoV‐2, it is possible to detect antibodies for up to 10 months. Additionally, our results showed that one dose of the CanSinoBio vaccine induces a lower response of IgG antibodies than that induced by the complete scheme of the Pfizer‐BioNTech vaccine.

Recombinant Antibodies in Veterinary Medicine: An Update

The production of recombinant antibodies has had a tremendous impact on several research fields, most prominently in biotechnology, immunology and medicine, enabling enormous advances in each. Thus far, a broad diversity of recombinant antibody (rAb) forms have been designed and expressed using different expression systems. Even though the majority of rAbs approved for clinical use are targeted to humans, advances in veterinary medicine seem promising. The aim of this mini-review is to present an update regarding the rAbs in veterinary medicine reported to date, as well as their potential use in diagnostics, prophylaxis and therapeutics. Full- and single-chain fragment variables are the most common forms of rAbs developed for the detection, prevention and control of parasitic, bacterial and viral diseases, as well as pain and cancer treatment. Nonetheless, advances in research seem to be skewed toward economically important animals, such as pigs, cows, poultry and dogs. Although significant results have been obtained from the rAbs reported here, most have not been developed enough to be approved. Further research and clinical trials should be encouraged to enable important findings to fulfill their intended potential to improve animal well-being.