T-cell responses in domestic pigs and wild boar upon infection with the
moderately virulent African swine fever virus strain “Estonia2014”
Abstract
Infection with African swine fever virus (ASFV) causes a highly lethal
hemorrhagic disease in domestic and Eurasian wild pigs. Thus, it is a
major threat to pig populations worldwide and a cause of substantial
economic losses. Recently, less virulent ASFV strains emerged naturally,
which showed higher experimental virulence in wild boar than in domestic
pigs. The reason for this difference in disease progression and outcome
is unclear but likely involves different immunological responses.
Unfortunately, besides the importance of CD8α+ lymphocytes, little is
known about the immune responses against ASFV in suids. Against this
background, we used a multicolor flow cytometry platform to investigate
the T-cell responses in wild boar and domestic pigs after infection with
the moderately virulent ASFV strain “Estonia2014” in two independent
trials. CD4–/CD8α+ and CD4+/CD8α+ αβ T-cell frequencies increased in
both subspecies in various tissues, but CD8α+ γδ T cells differentiated
and responded in wild boar only. Proliferation in CD8α+ T cells was
found 10 days post infectionem only. Frequencies of T-bet+ T cells
increased in wild boar but not in domestic pigs. Of note, we found a
considerable loss of perforin expression in cytotoxic T cells, 5 and 7
dpi. Both subspecies established a regulatory T-cell response 10 dpi. In
domestic pigs, we show increasing levels of ICOS+ and CD8α+ invariant
Natural Killer T cells. These disparities in T-cell responses might
explain some of the differences in disease progression in wild boar and
domestic pigs and should pave the way for future studies.