SARS-COV-2 recombinant Receptor-Binding-Domain (RBD) induces neutralizing antibodies against variant strains of SARS-CoV-2 and SARS-CoV-1.

SARS-CoV-2 is the etiological agent of COVID19. There are currently several licensed vaccines approved for human use and most of them target the spike protein in the virion envelope to induce protective immunity. Recently, variants that spread more quickly have emerged. There is evidence that some of these variants are less sensitive to neutralization in vitro, but it is not clear whether they can evade vaccine induced protection. In this study, we tested SARS-CoV-2 spike RBD as a vaccine antigen and explored the effect of formulation with Alum/MPLA or AddaS03 adjuvants. Our results show that RBD induces high titers of neutralizing antibodies and activates strong cellular immune responses. There is also significant cross-neutralization of variants B.1.1.7 and B.1.351 and to a lesser extent, SARS-CoV-1. These results indicate that recombinant RBD can be a viable candidate as a stand-alone vaccine or as a booster shot to diversify our strategy for COVID19 protection.

Native Folding of a Recombinant gpE1/gpE2 Heterodimer Vaccine Antigen from a Precursor Protein Fused with Fc IgG.

A recombinant strain HCV1 (hepatitis C virus [HCV] genotype 1a) gpE1/gpE2 (E1E2) vaccine candidate was previously shown by our group to protect chimpanzees and generate broad cross-neutralizing antibodies in animals and humans. In addition, recent independent studies have highlighted the importance of conserved neutralizing epitopes in HCV vaccine development that map to antigenic clusters in E2 or the E1E2 heterodimer. E1E2 can be purified using Galanthis nivalis lectin agarose (GNA), but this technique is suboptimal for global production. Our goal was to investigate a high-affinity and scalable method for isolating E1E2. We generated an Fc tag-derived (Fc-d) E1E2 that was selectively captured by protein G Sepharose, with the tag being removed subsequently using PreScission protease. Surprisingly, despite the presence of the large Fc tag, Fc-d E1E2 formed heterodimers similar to those formed by GNA-purified wild-type (WT) E1E2 and exhibited nearly identical binding profiles to HCV monoclonal antibodies that target conserved neutralizing epitopes in E2 (HC33.4, HC84.26, and AR3B) and the E1E2 heterodimer (AR4A and AR5A). Antisera from immunized mice showed that Fc-d E1E2 elicited anti-E2 antibody titers and neutralization of HCV pseudotype viruses similar to those with WT E1E2. Competition enzyme-linked immunosorbent assays (ELISAs) showed that antisera from immunized mice inhibited monoclonal antibody binding to neutralizing epitopes. Antisera from Fc-d E1E2-immunized mice exhibited stronger competition for AR3B and AR5A than the WT, whereas the levels of competition for HC84.26 and AR4A were similar. We anticipate that Fc-d E1E2 will provide a scalable purification and manufacturing process using protein A/G-based chromatography. IMPORTANCE: A prophylactic HCV vaccine is still needed to control this global disease despite the availability of direct-acting antivirals. Previously, we demonstrated that a recombinant envelope glycoprotein (E1E2) vaccine (genotype 1a) elicited cross-neutralizing antibodies from human volunteers. A challenge for isolating the E1E2 antigen is the reliance on GNA, which is unsuitable for large scale-up and global vaccine delivery. We have generated a novel Fc domain-tagged E1E2 antigen that forms functional heterodimers similar to those with native E1E2. Affinity purification and removal of the Fc tag from E1E2 resulted in an antigen with a nearly identical profile of cross-neutralizing epitopes. This antigen elicited anti-HCV antibodies that targeted conserved neutralizing epitopes of E1E2. Owing to the high selectivity and cost-effective binding capacity of affinity resins for capture of the Fc-tagged rE1E2, we anticipate that our method will provide a means for large-scale production of this HCV vaccine candidate.

Intrinsic Viral Factors Are the Dominant Determinants of the Hepatitis C Virus Response to Interferon Alpha Treatment in Chimeric Mice.

BACKGROUND: Hepatitis C virus infection is a global health problem. New direct-acting antiviral agents have been recently approved. However, due to their high cost and some genotypes remaining difficult to treat, interferon-based therapy with pegylated interferon and ribavirin likely may remain a component of hepatitis C virus treatment for some patients. Unfortunately, pegylated interferon / ribavirin treatment achieved favorable outcomes in less than 50% of patients. Factors determining the outcome to pegylated interferon/ribavirin include both host and viral factors. It has been a major challenge to separate the host and viral factors in most in vivo systems. AIMS & METHODS: We used two hepatitis C virus strains from patients with different interferon-sensitivities and three hepatocyte donors, each with distinct interleukin 28B and interferon lambda 4 single nucleotide polymorphisms to investigate the contributions of viral and host factors to the response of hepatitis C virus to interferon treatment in chimeric mice. RESULTS AND CONCLUSIONS: We found that viral factors were the dominant factors in determining the interferon treatment outcomes in chimeric mice. Host factors, such as pre-treatment liver interferon-stimulated gene expression and single nucleotide polymorphisms near interleukin 28B and interferon lambda 4 coding regions, were less important determinants of the response to interferon in the chimeric mice than they were in patients. Our results also suggest that a complete immune system as seen in patients may be required for host factors such as single nucleotide polymorphisms near interleukin 28B/interferon lambda 4 and pre-treatment liver interferon-stimulated gene upregulation to have an effect on the interferon response.