Abstract
Although swine are natural hosts for influenza A viruses, the porcine T-cell response to swine influenza A virus (FLUAVsw) infection has been poorly characterized so far. We have studied Ki-67 expression and FLUAVsw-specific production of IFN-γ, TNF-α and IL-2 in CD4+ and CD8β+ T cells isolated from piglets that had been intratracheally infected with a H1N2 FLUAVsw isolate. IFN-γ+TNF-α+IL-2+ multifunctional CD4+ T cells were present in the blood of all infected animals at one or two weeks after primary infection and their frequency increased in four out of six animals after homologous secondary infection. These cells produced higher amounts of IFN-γ, TNF-α and IL-2 than did CD4+ T cells that only produced a single cytokine. The vast majority of cytokine-producing CD4+ T cells expressed CD8α, a marker associated with activation and memory formation in porcine CD4+ T cells. Analysis of CD27 expression suggested that FLUAVsw-specific CD4+ T cells included both central memory and effector memory populations. Three out of six animals showed a strong increase of Ki-67+perforin+ CD8β+ T cells in blood one week post infection. Blood-derived FLUAVsw-specific CD8β+ T cells could be identified after an in vitro expansion phase and were multifunctional in terms of CD107a expression and co-production of IFN-γ and TNF-α. These data show that multifunctional T cells are generated in response to FLUAVsw infection of pigs, supporting the idea that T cells contribute to the efficient control of infection.Electronic supplementary materialThe online version of this article (doi:10.1186/s13567-015-0182-3) contains supplementary material, which is available to authorized users.
Highlights
Pigs are natural hosts for influenza A viruses and infections of humans with swine influenza A viruses (FLUAVsw) have been reported [1]
By comparing the median fluorescence intensity (MFI) obtained by flow cytometry (FCM) for the investigated cytokines (IFN-γ, TNF-α, IL-2) among single, double- and triple-cytokine-producing CD4+ T cells isolated from week 2 after primary infection onwards, we found higher quantities of IFN-γ and TNF-α in tripleand double-producers (Figures 5A and B and Additional file 6)
A FLUAVsw H1N2 isolate from Germany was used for infection and in vitro restimulation
Summary
Pigs are natural hosts for influenza A viruses and infections of humans with swine influenza A viruses (FLUAVsw) have been reported [1]. The 2009 pandemic H1N1 virus was frequently transmitted from farmers to pigs during the last years, thereby reflecting the zoonotic potential of this. These observations, and economic and animal welfare issues of FLUAVsw infections in pig production units, justify investigations on pig-FLUAVsw hostpathogen interactions. FLUAVsw infections are usually rapidly controlled by the porcine immune system and an elimination of replicating virus from the respiratory tract within one week has been reported [4]. It is assumed that these antibodies play a major role in control of infection, a production of IgA antibodies by B cells in the nasal mucosa has been reported [5]
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