A recombinant bovine herpesvirus-4 vectored vaccine delivered via intranasal nebulization elicits viral neutralizing antibody titers in cattle

An attenuated herpesvirus vectored vaccine candidate induces T-cell responses against highly conserved porcine reproductive and respiratory syndrome virus M and NSP5 proteins that are unable to control infection

Porcine reproductive and respiratory syndrome virus (PRRSV) remains a leading cause of economic loss in pig farming worldwide. Existing commercial vaccines, all based on modified live or inactivated PRRSV, fail to provide effective immunity against the highly diverse circulating strains of both PRRSV-1 and PRRSV-2. Therefore, there is an urgent need to develop more effective and broadly active PRRSV vaccines. In the absence of neutralizing antibodies, T cells are thought to play a central role in controlling PRRSV infection. Herpesvirus-based vectors are novel vaccine platforms capable of inducing high levels of T cells against encoded heterologous antigens. Therefore, the aim of this study was to assess the immunogenicity and efficacy of an attenuated herpesvirus-based vector (bovine herpesvirus-4; BoHV-4) expressing a fusion protein comprising two well-characterized PRRSV-1 T-cell antigens (M and NSP5). Prime-boost immunization of pigs with BoHV-4 expressing the M and NSP5 fusion protein (vector designated BoHV-4-M-NSP5) induced strong IFN-γ responses, as assessed by ELISpot assays of peripheral blood mononuclear cells (PBMC) stimulated with a pool of peptides representing PRRSV-1 M and NSP5. The responses were closely mirrored by spontaneous IFN-γ release from unstimulated cells, albeit at lower levels. A lower frequency of M and NSP5 specific IFN-γ responding cells was induced following a single dose of BoHV-4-M-NSP5 vector. Restimulation using M and NSP5 peptides from PRRSV-2 demonstrated a high level of cross-reactivity. Vaccination with BoHV-4-M-NSP5 did not affect viral loads in either the blood or lungs following challenge with the two heterologous PRRSV-1 strains. However, the BoHV-4-M-NSP5 prime-boost vaccination showed a marked trend toward reduced lung pathology following PRRSV-1 challenge. The limited effect of T cells on PRRSV-1 viral load was further examined by analyzing local and circulating T-cell responses using intracellular cytokine staining and proliferation assays. The results from this study suggest that vaccine-primed T-cell responses may have helped in the control of PRRSV-1 associated tissue damage, but had a minimal, if any, effect on controlling PRRSV-1 viral loads. Together, these results indicate that future efforts to develop effective PRRSV vaccines should focus on achieving a balanced T-cell and antibody response.

Assessment of BoHV-4-based vector vaccine intranasally administered in a hamster challenge model of lung disease

Introduction

Bovine herpesvirus 4 (BoHV-4) is a bovine Rhadinovirus not associated with a specific pathological lesion or disease and experimentally employed as a viral vector vaccine. BoHV-4-based vector (BoHV-4-BV) has been shown to be effective in immunizing and protecting several animal species when systemically administrated through intramuscular, subcutaneous, intravenous, or intraperitoneal routes. However, whether BoHV-4-BV affords respiratory disease protection when administered intranasally has never been tested.

Methods

In the present study, recombinant BoHV-4, BoHV-4-A-S-ΔRS-HA-ΔTK, was constructed to deliver an expression cassette for the SARS-CoV-2 spike glycoprotein, and its immunogenicity, as well as its capability to transduce cells of the respiratory tract, were tested in mice. The well-established COVID-19/Syrian hamster model was adopted to test the efficacy of intranasally administered BoHV-4-A-S-ΔRS-HA-ΔTK in protecting against a SARS-CoV-2 challenge.

Results

The intranasal administration of BoHV-4-A-S-ΔRS-HA-ΔTK elicited protection against SARS-CoV-2, with improved clinical signs, including significant reductions in body weight loss, significant reductions in viral load in the trachea and lungs, and significant reductions in histopathologic lung lesions compared to BoHV-4-A-S-ΔRS-HA-ΔTK administered intramuscularly.

Discussion

These results suggested that intranasal immunization with BoHV-4-BV induced protective immunity and that BoHV-4-BV could be a potential vaccine platform for the protection of other animal species against respiratory diseases.

Bovine Herpesvirus-4 Based Vaccine Provides Protective Immunity against Streptococcus suis Disease in a Rabbit Model

Streptococcus suis (S. suis) is a bacterial pathogen of pigs that has a major animal health and economic impact on the pig industry. Bovine herpesvirus-4 (BoHV-4) is a new virus-based vaccine vector that has been used for the immunogenic delivery of antigens from a variety of pathogens. In the present study, two recombinant BoHV-4-based vectors were evaluated for their ability to induce immunity and protection against S. suis in a rabbit model. The GMD protein is a fusion protein consisting of multiple dominant B-cell epitopes ((B-cell dominant epitopes of GAPDH, MRP, and DLDH antigens) (BoHV-4/GMD)) and the second suilysin (SLY) (BoHV-4/SLY) from S. suis serotype 2 (SS2). Both GMD and SLY delivered by the BoHV-4 vectors were recognized by sera from SS2-infected rabbits. The vaccination of rabbits with the BoHV-4 vectors induced antibodies against SS2, as well as against additional S. suis serotypes, SS7 and SS9. However, sera from BoHV-4/GMD-vaccinated animals promoted a significant level of phagocytic activity by pulmonary alveolar macrophages (PAMs) against SS2, SS7, and SS9. In contrast, sera from rabbits immunized with BoHV-4/SLY induced PAM phagocytic activity against only SS2. In addition, BoHV-4 vaccines differed in the associated level of protection against lethal SS2 challenge, which ranged from high (71.4%) to low (12.5%) for BoHV-4/GMD and BoHV-4/SLY, respectively. These data suggest BoHV-4/GMD as a promising vaccine candidate against S. suis disease.

Evaluation of the Mucosal Immunity Effect of Bovine Viral Diarrhea Virus Subunit Vaccine E2Fc and E2Ft

Classified as a class B infectious disease by the World Organization for Animal Health (OIE), bovine viral diarrhea/mucosal disease is an acute, highly contagious disease caused by the bovine viral diarrhea virus (BVDV). Sporadic endemics of BVDV often lead to huge economic losses to the dairy and beef industries. To shed light on the prevention and control of BVDV, we developed two novel subunit vaccines by expressing bovine viral diarrhea virus E2 fusion recombinant proteins (E2Fc and E2Ft) through suspended HEK293 cells. We also evaluated the immune effects of the vaccines. The results showed that both subunit vaccines induced an intense mucosal immune response in calves. Mechanistically, E2Fc bonded to the Fc γ receptor (FcγRI) on antigen-presenting cells (APCs) and promoted IgA secretion, leading to a stronger T-cell immune response (Th1 type). The neutralizing antibody titer stimulated by the mucosal-immunized E2Fc subunit vaccine reached 1:64, which was higher than that of the E2Ft subunit vaccine and that of the intramuscular inactivated vaccine. The two novel subunit vaccines for mucosal immunity developed in this study, E2Fc and E2Ft, can be further used as new strategies to control BVDV by enhancing cellular and humoral immunity.

The first study on the occurrence of bovine herpesviruses in the wild fauna of the Moscow region, Russia

Background and Aim:

Some pathogens that cause infections in cattle are found in wild artiodactyls. Their prevalence, possible impact on the population of free-living animals, and the spread of infectious pathology in livestock have yet to be studied. We investigated the occurrence of bovine herpesviruses (BoHV-1, BoHV-4, and BoHV-6) among wild moose and roe deer in 8 areas of the Moscow region in the Russian Federation.

Materials and Methods:

One hundred and one tissue samples and nasal swabs of 24 moose and seven roe deer were studied using a real-time polymerase chain reaction (PCR) for BoHV-1 DNA and conventional PCR for BoHV-4 and BoHV-6 DNA. A virus neutralization test (VNT) was used to detect antibodies to BoHV-1 in 19 serum samples. The final antibody titer was calculated with the Spearman-Kärber method.

Results:

BoHV-4 and BoHV-6 DNA were not detected in all studied samples of 31 animals. BoHV-1 DNA was detected using a real-time PCR in nasal swabs from 2 adult roe deer. For BoHV-1, only 9/19 tested serum samples reacted positive in VNT with the titer range from 0.67 ± 0.19 to 3.75 ± 0.10 log2. Antibodies were detected in all age groups, more often in fawns under 1-year-old. The seropositivity of females was higher than in males.

Conclusion:

Wild ungulates can potentially represent a reservoir of new pathogenic livestock viruses. To study the prevalence and genetic diversity of wild ungulate herpesviruses, detailed molecular studies of the cervid herpesvirus 1, cervid herpesvirus 2, and elk herpesvirus 1 are necessary.

Genome sequence and experimental infection of calves with bovine gammaherpesvirus 4 (BoHV-4)

Bovine gammaherpesvirus 4 (BoHV-4) is ubiquitous in cattle worldwide, and it has been detected in animals exhibiting broad clinical presentations. The virus has been detected in the United States since the 1970s; however, its clinical relevance remains unknown. Here, we determined the complete genome sequences of two contemporary BoHV-4 isolates obtained from respiratory (SD16-38) or reproductive (SD16-49) tract specimens and assessed clinical, virological, and pathological outcomes upon intranasal (IN) inoculation of calves with the respiratory BoHV-4 isolate SD16-38. A slight and transient increase in body temperature was observed in BoHV-4-inoculated calves. Additionally, transient viremia and virus shedding in nasal secretions were observed in all inoculated calves. BoHV-4 DNA was detected by nested PCR in the tonsil and regional lymph nodes (LNs) of calves euthanized on day 5 post-inoculation (pi) and in the lungs of calves euthanized on day 10 pi. Calves euthanized on day 35 pi harbored BoHV-4 DNA in the respiratory tract (turbinates, trachea, lungs), regional lymphoid tissues, and trigeminal ganglia. Interestingly, in situ hybridization revealed the presence of BoHV-4 DNA in nerve bundles surrounding the trigeminal ganglia and retropharyngeal lymph nodes (day 35 pi). No histological changes were observed in the respiratory tract (turbinate, trachea, and lung), lymphoid tissues (tonsil, LNs, thymus, and spleen), or central nervous tissues (olfactory bulb and trigeminal ganglia) sampled throughout the animal studies (days 5, 10, and 35 pi). This study contributes to the understanding of the infection dynamics and tissue distribution of BoHV-4 following IN infection in calves. These results suggest that BoHV-4 SD16-38 used in our study has low pathogenicity in calves upon intranasal inoculation.

Immunization With Bovine Herpesvirus-4-Based Vector Delivering PPRV-H Protein Protects Sheep From PPRV Challenge

The Morbillivirus peste des petits ruminants virus (PPRV) is the causal agent of a highly contagious disease that mostly affects sheep and goats and produces considerable losses in developing countries. Current PPRV control strategies rely on live-attenuated vaccines, which are not ideal, as they cannot differentiate infected from vaccinated animals (DIVA). Recombinant vector-based vaccines expressing viral subunits can provide an alternative to conventional vaccines, as they can be easily paired with DIVA diagnostic tools. In the present work, we used the bovine herpesvirus-4-based vector (BoHV-4-A) to deliver PPRV hemagglutinin H antigen (BoHV-4-A-PPRV-H-ΔTK). Vaccination with BoHV-4-A-PPRV-H-ΔTK protected sheep from virulent PPRV challenge and prevented virus shedding. Protection correlated with anti-PPRV IgGs, neutralizing antibodies and IFN-γ-producing cells induced by the vaccine. Detection of antibodies exclusively against H-PPRV in animal sera and not against other PPRV viral proteins such as F or N could serve as a DIVA diagnostic test when using BoHV-4-A-PPRV-H-ΔTK as vaccine. Our data indicate that BoHV-4-A-PPRV-H-ΔTK could be a promising new approach for PPRV eradication programs.

OvHV-2 Glycoprotein B Delivered by a Recombinant BoHV-4 Is Immunogenic and Induces Partial Protection against Sheep-Associated Malignant Catarrhal Fever in a Rabbit Model

An efficacious vaccine for sheep-associated malignant catarrhal fever (SA-MCF) is important for the livestock industry. Research towards SA-MCF vaccine development is hindered by the absence of culture systems to propagate the causative agent, ovine herpesvirus-2 (OvHV-2), which means its genome cannot be experimentally modified to generate an attenuated vaccine strain. Alternative approaches for vaccine development are needed to deliver OvHV-2 antigens. Bovine herpesvirus 4 (BoHV-4) has been evaluated as a vaccine vector for several viral antigens with promising results. In this study, we genetically engineered BoHV-4 to express OvHV-2 glycoprotein B (gB) and evaluated its efficacy as an SA-MCF vaccine using a rabbit model. The construction of a viable recombinant virus (BoHV-4-AΔTK-OvHV-2-gB) and confirmation of OvHV-2 gB expression were performed in vitro. The immunization of rabbits with BoHV-4-AΔTK-OvHV-2-gB elicited strong humoral responses to OvHV-2 gB, including neutralizing antibodies. Following intra-nasal challenge with a lethal dose of OvHV-2, 42.9% of the OvHV-2 gB vaccinated rabbits were protected against SA-MCF, while all rabbits in the mock-vaccinated group succumbed to SA-MCF. Overall, OvHV-2 gB delivered by the recombinant BoHV-4 was immunogenic and partly protective against SA-MCF in rabbits. These are promising results towards an SA-MCF vaccine; however, improvements are needed to increase protection rates.