Abstract
BackgroundCurrently, an in vitro immunogenicity screening system for the immunological assessment of potential porcine reproductive and respiratory syndrome virus (PRRSV) vaccine candidates is highly desired. Thus, in the present study, two genetically divergent PRRSVs were characterized in vitro and in vivo to identify an in vitro system and immunological markers that predict the host immune response. Porcine alveolar macrophages (PAMs) and peripheral blood mononuclear cells (PBMCs) collected from PRRSV-negative pigs were used for in vitro immunological evaluation, and the response of these cells to VR2332c or JA142c were compared with those elicited in pigs challenged with the same viruses.ResultsCompared with VR2332c or mock infection, JA142c induced increased levels of type I interferons and pro-inflammatory cytokines (TNF-α, IL-1α/β, IL-6, IL-8, and IL-12) in PAMs, and these elevated levels were comparable to the cytokine induction observed in PRRSV-challenged pigs. Furthermore, significantly greater numbers of activated CD4+ T cells, type I helper T cells, cytotoxic T cells and total IFN-γ+ cells were observed in JA142c-challenged pigs than in VR2332c- or mock-challenged pigs.ConclusionsBased on these results, the innate immune response patterns (particularly IFN-α, TNF-α and IL-12) to specific PRRSV strains in PAMs might reflect those elicited by the same viruses in pigs.
Highlights
An in vitro immunogenicity screening system for the immunological assessment of potential porcine reproductive and respiratory syndrome virus (PRRSV) vaccine candidates is highly desired
The majority of previous studies examining PRRSV-induced immune responses have used a single PRRSV strain that was tested either in vitro or in vivo but rarely both. These studies failed to take into account the effects of PRRSV strain diversity, immune evaluation systems, or both when drawing general conclusions regarding PRRSV immunobiology. To fill in these gaps, the current study focused on two important goals: i) in vitro and in vivo characterization of the immune responses elicited by two divergent Type II PRRSV strains, and ii) identification of a feasible in vitro model or specific immunological markers to predict the in vivo immune responses induced by a PRRSV strain
PRRSVs replicated at similar levels in Porcine alveolar macrophages (PAMs) and pigs A multi-step growth curve for PRRSV replication in PAMs was constructed by measuring viral titres in cell lysates at 6, 12, 24, 36 and 48 h post-infection
Summary
An in vitro immunogenicity screening system for the immunological assessment of potential porcine reproductive and respiratory syndrome virus (PRRSV) vaccine candidates is highly desired. In the present study, two genetically divergent PRRSVs were characterized in vitro and in vivo to identify an in vitro system and immunological markers that predict the host immune response. Porcine alveolar macrophages (PAMs) and peripheral blood mononuclear cells (PBMCs) collected from PRRSV-negative pigs were used for in vitro immunological evaluation, and the response of these cells to VR2332c or JA142c were compared with those elicited in pigs challenged with the same viruses. The immune responses elicited by PRRSV in vitro and in vivo have been well-studied, but researchers have not reached a consensus on immune response patterns. According to the majority of studies, PRRSVs induce IL-8 [25, 26], and the in vitro/ex vivo induction of IL-6 by PRRSV has been reported [27,28,29]
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