Comparative analysis of adaptive immune responses following experimental infections of cattle with bovine viral diarrhoea virus-1 and an Asiatic atypical ruminant pestivirus

Th17 cell differentiation induced by cytopathogenic biotype BVDV-2 in bovine PBLCs

Background

Bovine viral diarrhea virus (BVDV) is a major pathogen that causes bovine viral diarrhea/mucosal disease (BVD-MD), which has become a global infectious disease due to its wide spread and the lack of effective treatment. The process of BVDV infection is complex. Once infected, host immune cells are activated and modulated. As a major immune cell, peripheral blood lymphocyte cells (PBLCs) are the primary target of BVDV. In order to further understand the mechanism of BVDV- host interaction, the expression profiles of host lymphocytes mRNAs associated with BVDV infection were investigated by transcriptomic sequencing analysis.

Results

The transcriptomic sequencing analysis was performed on bovine PBLCs infected with CP BVDV-2 GS2018 after 12 h of infection. Gene expression profiling demonstrated that 1052 genes were differentially expressed in GS2018 infected PBLCs compared with the control group. Of these genes, 485 genes were up-regulated and 567 were down-regulated. The 19 differential expressed genes (DEGs) were selected for validation using quantitative real-time PCR and the results were consistent with the results of RNA-Seq. Gene ontology enrichment and KEGG pathway analysis showed that 1052 DEGs were significantly enriched in 16 pathways, including cytokine-cytokine receptor interaction, IL17, PI3K-Akt, MAPK and TNF signaling pathway. PPI network analysis showed that IL17A, IFN-γ and TNF-α interacted with various proteins and may play crucial roles in BVDV-2 infection. Of note, we confirmed that GS2018 induced Th17 cell differentiation in PBLCs and persistently increased the expression levels of IL17A. In turn, the replication of GS2018 was inhibited by IL17A.

Conclusion

In this study, the transcription changes of DEGs related to host immune responses in bovine PBLCs were caused by CP BVDV-2 infection. In particular, the effector molecules IL17A of Th17 cells were significantly up-regulated, which inhibited viral replication. These results will contribute to exploration and further understanding of the host immune response mechanism and interaction between host and BVDV-2.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-08194-w.

Novel Potent IFN-γ-Inducing CD8+ T Cell Epitopes Conserved among Diverse Bovine Viral Diarrhea Virus Strains

Studies of immune responses elicited by bovine viral diarrhea virus (BVDV) vaccines have primarily focused on the characterization of neutralizing B cell and CD4⁺ T cell epitopes. Despite the availability of commercial vaccines for decades, BVDV prevalence in cattle has remained largely unaffected. There is limited knowledge regarding the role of BVDV-specific CD8⁺ T cells in immune protection, and indirect evidence suggests that they play a crucial role during BVDV infection. In this study, the presence of BVDV-specific CD8⁺ T cells that are highly cross-reactive in cattle was demonstrated. Most importantly, novel potent IFN-γ-inducing CD8⁺ T cell epitopes were identified from different regions of BVDV polyprotein. Eight CD8⁺ T cell epitopes were identified from the following structural BVDV Ags: E^rns, E1, and E2 glycoproteins. In addition, from nonstructural BVDV Ags N^pro, NS2-3, NS4A-B, and NS5A-B, 20 CD8⁺ T cell epitopes were identified. The majority of these IFN-γ-inducing CD8⁺ T cell epitopes were found to be highly conserved among more than 200 strains from BVDV-1 and -2 genotypes. These conserved epitopes were also validated as cross-reactive because they induced high recall IFN-γ⁺CD8⁺ T cell responses ex vivo in purified bovine CD8⁺ T cells isolated from BVDV-1- and -2-immunized cattle. Altogether, 28 bovine MHC class I-binding epitopes were identified from key BVDV Ags that can elicit broadly reactive CD8⁺ T cells against diverse BVDV strains. The data presented in this study will lay the groundwork for the development of a contemporary CD8⁺ T cell-based BVDV vaccine capable of addressing BVDV heterogeneity more effectively than current vaccines.

Bovine Pestivirus Heterogeneity and Its Potential Impact on Vaccination and Diagnosis

Bovine Pestiviruses A and B, formerly known as bovine viral diarrhoea viruses (BVDV)-1 and 2, respectively, are important pathogens of cattle worldwide, responsible for significant economic losses. Bovine viral diarrhoea control programmes are in effect in several high-income countries but less so in low- and middle-income countries where bovine pestiviruses are not considered in disease control programmes. However, bovine pestiviruses are genetically and antigenically diverse, which affects the efficiency of the control programmes. The emergence of atypical ruminant pestiviruses (Pestivirus H or BVDV-3) from various parts of the world and the detection of Pestivirus D (border disease virus) in cattle highlights the challenge that pestiviruses continue to pose to control measures including the development of vaccines with improved cross-protective potential and enhanced diagnostics. This review examines the effect of bovine pestivirus diversity and emergence of atypical pestiviruses in disease control by vaccination and diagnosis.

Phylogenetic and evolutionary analysis of HoBi-like pestivirus: Insights into origin and dispersal

The HoBi-like pestivirus (HoBiPeV), currently classified as Pestivirus H species, is a pathogen associated with a broad spectrum of clinical manifestations in ruminants, particularly in cattle. Since HoBiPeV complete genome sequencing data is scarce, in the present study we described five nearly complete new Brazilian HoBiPeV genomes and further perform a more complete genetic and evolutionary characterization with all additional genome sequences available in the GenBank database. Entropy and selection pressure analysis showed the E2 gene, a surface glycoprotein, is the most variable gene, which also displays the greatest number of sites under positive selection. Phylogenetic and Bayesian inference based on complete genome and Npro gene, respectively, from all HoBiPeV sequences available so far, confirms the existence of three main clades (a, b, and c). The abovementioned analysis suggests that this pestivirus species probably emerged in Asia and spread to different regions including Brazil, where only strains belonging to specific genetic group 'a' have been found. The hypothesis of the HoBiPeV introduction in Brazil (between 1,890 and 1,962), formulated based on Bayesian inference, coincides with a period of intensive importation of water buffalo (Bubalus arnee) and indicine cattle (Bos taurus indicus) from Asia to Brazil, suggesting that this could be the origin of the current Brazilian HoBiPeV genetic group 'a'.

Recombinant Erns-E2 protein vaccine formulated with MF59 and CPG-ODN promotes T cell immunity against bovine viral diarrhea virus infection

To obtain an effective vaccine candidate against bovine viral diarrhea virus (BVDV) disease which causes great economical loss in cattle industries, recombinant E^rns-E2 protein vaccine containing MF59 and CPG-ODN adjuvants was prepared and assessed in this study. The recombinant plasmid (pET32a-E^rns-E2) was constructed and transformed into BL21 (DE3) cells to produce E^rns-E2 protein. We immunized mice with the MF59-and CPG-ODN-adjuvanted recombinant E^rns-E2 protein, E2 protein, or E^rns protein, respectively. To evaluate immunogenicity and efficacy of a vaccine-adjuvant combination, mice were challenged with BVDV BJ175170 strain after immunization. All adjuvanted vaccines elicited detectable humoral and cellular immune responses, the BVDV-specific antibody titers as well as interleukin 4 (IL-4) levels in sera of mice immunized with the recombinant E^rns-E2 protein were higher than in those of mice immunized with either the recombinant E^rns or E2 protein. Besides, immunization with the E^rns-E2 vaccines induced higher percentage of CD4⁺IFN-γ⁺, CD8⁺IFN-γ⁺ T cells and CD3⁺TNF-α⁺ T cells compared with the other vaccines. More protective efficacy against BVDV infection was acquired in the mice treated with the recombinant E^rns-E2 protein, as shown by a reduction of viremia and slight pathological changes compared with both the control mice and the other vaccinated mice. Our findings suggest that the use of the recombinant E^rns-E2 protein vaccine formulated with MF59 and CPG-ODN adjuvants enhances T cell responses and viral control, which warrants the E^rns-E2 protein vaccine-adjuvant combination could be as a vaccine strategy to against BVDV.