Summary
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.
Keywords : African swine fever virus, experimental infection,
domestic pig, wild boar, T cell response, iNKT cells