An Orf-Virus (ORFV)-Based Vector Expressing a Consensus H1 Hemagglutinin Provides Protection against Diverse Swine Influenza Viruses

Abstract

Influenza A viruses (IAV-S) belonging to the H1 subtype are endemic in swine worldwide. Antigenic drift and antigenic shift lead to a substantial antigenic diversity in circulating IAV-S strains. As a result, the most commonly used vaccines based on whole inactivated viruses (WIVs) provide low protection against divergent H1 strains due to the mismatch between the vaccine virus strain and the circulating one. Here, a consensus coding sequence of the full-length of HA from H1 subtype was generated in silico after alignment of the sequences from IAV-S isolates obtained from public databases and was delivered to pigs using the Orf virus (ORFV) vector platform. The immunogenicity and protective efficacy of the resulting ORFVΔ121conH1 recombinant virus were evaluated against divergent IAV-S strains in piglets. Virus shedding after intranasal/intratracheal challenge with two IAV-S strains was assessed by real-time RT-PCR and virus titration. Viral genome copies and infectious virus load were reduced in nasal secretions of immunized animals. Flow cytometry analysis showed that the frequency of T helper/memory cells, as well as cytotoxic T lymphocytes (CTLs), were significantly higher in the peripheral blood mononuclear cells (PBMCs) of the vaccinated groups compared to unvaccinated animals when they were challenged with a pandemic strain of IAV H1N1 (CA/09). Interestingly, the percentage of T cells was higher in the bronchoalveolar lavage of vaccinated animals in relation to unvaccinated animals in the groups challenged with a H1N1 from the gamma clade (OH/07). In summary, delivery of the consensus HA from the H1 IAV-S subtype by the parapoxvirus ORFV vector decreased shedding of infectious virus and viral load of IAV-S in nasal secretions and induced cellular protective immunity against divergent influenza viruses in swine.

Identification of an Immunodominant B-Cell Epitope in African Swine Fever Virus p30 Protein and Evidence of p30 Antibody-Mediated Antibody Dependent Cellular Cytotoxicity

“…Similar to what we observed in Study 1, animals in Study 2 also developed high antibody titers against ASFV p30, albeit overall titers were lower than those detected in animals in Study 1. As observed in other immunization studies with ORFV vectors in swine [50][51][52][53][54][55], an anamnestic antibody response to ASFV p30 was detected a week after the booster immunizations on day 21 (Study 1) or 28 (Study 2), respectively.…”

“…As expected, virus replication was markedly impaired in swine cells (PK15). This was previously described in primary swine turbinate cells [50][51][52], indicating that ORFV viruses do not, or only minimally, replicate in cells of swine origin, which constitutes a safety feature for the use of ORFV-based vectors in swine.…”

Immunogenicity of chimeric hemagglutinins delivered by an orf virus vector platform against swine influenza virus

“…More recently, our team demonstrated that an ORFV vector expressing the full-length HA glycoprotein of a well-characterized swine influenza virus (OH07) elicited antibody and T-cell responses that correlated with protection against homologous IAV-S challenge ( 5 ). We have also shown that an ORFV vector expressing a centralized consensus H1 sequence elicited cross-reactive and protective responses against IAV-S challenge in pigs ( 22 ). Collectively, these studies validate ORFV as a valuable tool for the development of vaccines targeting various viral pathogens in swine and other animal species.…”

Swine influenza A virus: challenges and novel vaccine strategies

“…These results indicate that a monovalent consensus vaccine design can improve cross-reactive responses against divergent H3 IAV-S compared to a wildtype sequence alone. Similarly, a consensus vaccine targeting H1 IAV-S has recently been described ( Do Nascimento et al., 2023 ). The consensus H1 IAV-S immunogen was developed using IAV-S sequences isolated between 2014-2017 and delivered by an ORFV viral vector (ORFV-conH1).…”

“…In contrast, immunization with ORFV-conH1 and challenge with a npdm clade virus induced a significantly higher frequency of T cells with a helper/memory phenotype and circulating IFN-γ CD8 + T cells. This induction of cell-mediated immune responses likely in the absence of neutralizing antibody responses again translated to a significant reduction of infectious virus in nasal secretions and 2- and 6-days post challenge coupled with lower viral RNA in the BAL ( Do Nascimento et al., 2023 ). Currently, reasons driving the differential kinetics of T cell development in these anatomical compartments are unknown, but analysis of the T cell responses prior to challenge may help uncover the reason behind these differences.…”