Abstract
BackgroundIn order to investigate host factors associated with the establishment of persistent foot-and-mouth disease virus (FMDV) infection, the systemic response to vaccination and challenge was studied in 47 steers. Eighteen steers that had received a recombinant FMDV A vaccine 2 weeks earlier and 29 non-vaccinated steers were challenged by intra-nasopharyngeal deposition of FMDV A24. For up to 35 days after challenge, host factors including complete blood counts with T lymphocyte subsets, type I/III interferon (IFN) activity, neutralizing and total FMDV-specific antibody titers in serum, as well as antibody-secreting cells (in 6 non-vaccinated animals) were characterized in the context of viral infection dynamics.ResultsVaccination generally induced a strong antibody response. There was a transient peak of FMDV-specific serum IgM in non-vaccinated animals after challenge, while IgM levels in vaccinated animals did not increase further. Both groups had a lasting increase of specific IgG and neutralizing antibody after challenge.Substantial systemic IFN activity in non-vaccinated animals coincided with viremia, and no IFN or viremia was detected in vaccinated animals. After challenge, circulating lymphocytes decreased in non-vaccinated animals, coincident with viremia, IFN activity, and clinical disease, whereas lymphocyte and monocyte counts in vaccinated animals were unaffected by vaccination but transiently increased after challenge. The CD4+/CD8+ T cell ratio in non-vaccinated animals increased during acute infection, driven by an absolute decrease of CD8+ cells.ConclusionsThe incidence of FMDV persistence was 61.5 % in non-vaccinated and 54.5 % in vaccinated animals. Overall, the systemic factors examined were not associated with the FMDV carrier/non-carrier divergence; however, significant differences were identified between responses of non-vaccinated and vaccinated cattle.Electronic supplementary materialThe online version of this article (doi:10.1186/s12917-016-0838-x) contains supplementary material, which is available to authorized users.
Highlights
In order to investigate host factors associated with the establishment of persistent foot-and-mouth disease virus (FMDV) infection, the systemic response to vaccination and challenge was studied in 47 steers
FMDV carrier/non-carrier divergence The overarching goal of this work was to investigate systemic trends associated with 2 categorical factors: vaccination status at the start of the experiment and FMDV carrier status determined at the end of the study
All probang samples from non-carriers were virus-negative by 21 dpi and remained negative, whereas all animals that were viruspositive in their 21-dpi probangs remained virus-positive until 28 dpi and beyond; there was no change in viral shedding in probangs in any animal between 21 dpi and the end of the experiment
Summary
In order to investigate host factors associated with the establishment of persistent foot-and-mouth disease virus (FMDV) infection, the systemic response to vaccination and challenge was studied in 47 steers. The bovine nasopharynx [7,8,9,10,11,12] and regional lymph nodes [13] have been identified as sites of this persistence, but it is poorly understood how FMDV evades clearance by the host immune response at these sites [14]. It is unknown whether there are pre-existent factors or patterns in the virus-host interaction during and after acute infection that can be used to predict or influence the ultimate outcome of virus clearance versus persistence
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