Immune responses to influenza D virus in calves previously infected with bovine viral diarrhea virus

Authors: BAUERMANN, FERNANDO - Oklahoma State University; FALKENBERG, SHOLLIE - Auburn University; RUDD, JENNIFER - Oklahoma State University; PETER, CRISTINA - Oklahoma State University; MERCHIRATTO, INGRYD - Oklahoma State University; RITCHEY, JERRY - Oklahoma State University; GILLIAM, JOHN - Oklahoma State University; TAYLOR, JARED - Oklahoma State University; Ma, Hao; MAGGIOLO, MAYARA - Oklahoma State University

Submitted to: Viruses
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/13/2023
Publication Date: 12/16/2023
Citation: Bauermann, F.V., Falkenberg, S., Rudd, J.M., Peter, C.M., Merchiratto, I., Ritchey, J.W., Gilliam, J., Taylor, J., Ma, H., Maggiolo, M.F. 2023. Immune responses to influenza D virus in calves previously infected with bovine viral diarrhea virus. Viruses. 15(12). Article 2442. https://doi.org/10.3390/v15122442.
DOI: https://doi.org/10.3390/v15122442

Interpretive Summary: The impact of calves initially infected by bovine viral diarrhea virus (BVDV) and later infected by the influenza D virus (IDV) was studied. Twenty BVDV-free calves were divided into four groups. Animals in group 1 and group 3 received BVDV on day 0, while calves in group 2 and group 4 were negative controls. Group 1 and group 2 were necropsied on day 13 post-infection. On day 21, group 3 and group 4 were intranasally infected with IDV and necropsied on day 42. Pre-exposed BVDV calves exhibited prolonged and increased IDV detaching in nasal secretions. Thymus in acutely infected BVDV calves (group 1) was about 50% less than controls (group 2). On day 42, two calves in group 3 showed thymus reduction, while three had normal weight. BVDV-exposed calves had reduced a/ß T-cell proliferation and percentage of IFN-' producing cells after IDV recall stimulation, particularly evident in those with persistent thymic atrophy. Conversely, antibody levels demonstrated no significant difference between groups. BVDV-inducted thymus depletion may vary from transient to persistent. Our analysis suggested a correlation between persistent thymus atrophy and impaired T-cell immune response to subsequent infections.

Technical Abstract: Bovine viral diarrhea virus (BVDV) induces temporary immunosuppression and thymus depletion in calves. This study explores the impact of prior BVDV exposure on the immune response to the influenza D virus (IDV) in calves. Twenty BVDV-naïve calves were divided into four groups. Animals in G1 and G3 received BVDV on day 0, while calves in G2 and G4 were mock-treated. G1 and G2 were necropsied on day 13 post-infection. On day 21, G3 and G4 were intranasally infected with IDV and necropsied on day 42. Pre-exposed BVDV calves exhibited prolonged and increased IDV shedding in nasal secretions. Thymus in acutely infected BVDV calves (G1) was about 50% depleted compared to controls (G2). On day 42, two calves in G3 displayed thymus de-pletion, while three had normal weight. BVDV-exposed calves had reduced a/ß T-cell proliferation and per-centage of IFN-' producing cells after IDV recall stimulation, particularly evident in those with persistent thymic atrophy. Conversely, antibody levels demonstrated no significant difference between groups. BVDV-inducted thymus depletion may vary from transient to persistent. Persistent thymus atrophy was cor-related with weaker IFN-' response and T-cell proliferation, suggesting a correlation between persistent thy-mus atrophy and impaired T-cell immune response to subsequent infections.