A highly effective African swine fever virus vaccine elicits a memory T cell response in vaccinated swine

Authors: ATTREED, SARAH - Oak Ridge Institute For Science And Education (ORISE); Silva, Christina; Abbot, Sophia; Ramirez-Medina, Elizabeth; Espinoza, Nallely; Borca, Manuel; Gladue, Douglas; Diaz San Segundo, Fayna

Submitted to: Pathogens
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/24/2022
Publication Date: 11/29/2022
Citation: Attreed, S.E., Silva, C.M., Abbott, S.T., Ramirez Medina, E., Espinoza, N.N., Borca, M.V., Gladue, D.P., Diaz San Segundo, F.C. 2022. A highly effective African swine fever virus vaccine elicits a memory T cell response in vaccinated swine. Pathogens. 11(12). Article 1438. https://doi.org/10.3390/pathogens11121438.
DOI: https://doi.org/10.3390/pathogens11121438

Interpretive Summary: African swine fever (ASF) is currently devastating the pork industry world wide. There has been recent advancements in the development of a protective vaccine that would help controlling this lethal disease. Even though identification of protective immune response mechanisms induced by this candidate are poorly understood, knowing more about the intricate machinery behind a protective immune response will help solidified a ramping up platform towards the development of the first commercially available vaccine against (ASF). In this manuscript, we analyze samples from animal inoculated with a protective dose of ASFV-G-'I177L vaccine strain at different times before and after challenge and compare the elicited immune response with naive control animals. The results presented in this manuscript suggest that memory T cells play a role in protective immunity and that studying certain T cell populations may be a surrogate immunity marker in ASF vaccination.

Technical Abstract: African Swine Fever Virus (ASFV) is the causative agent of a highly contagious and lethal vector-borne disease in suids. Recently, a live attenuated virus strain, developed using the currently circulating, virulent Georgia strain (ASFV-G) with a single gene deletion (ASFV-G-'I177L), resulted in an effective vaccine. Nevertheless, identification of protective immune response mechanisms induced by this candidate are poorly understood. In this study, Yorkshire crossbred swine intramuscularly vaccinated with 106 50% hemadsorption dose (HAD50) of ASFV-G-deltaI177L or a vehicle control were challenged at 28 days post-inoculation (dpi) with 102 HAD50 of ASFV-G. Analysis of purified peripheral blood mononuclear cells following inoculation and challenge revealed that both CD4+ and CD8+ central memory T cells (CD44+CD62L+CCR7+, Tcm) decreased significantly by 28 dpi in ASFV-G-deltaI177L-vaccinated swine compared to baseline and time-matched controls. Conversely, CD4+ and CD8+ effector memory T cells (CD44+CD62-CCR7-, Tem) increased significantly among ASFV-G-'I177L-vaccined swine by 14 dpi compared to baseline and time-matched controls. Additionally, the percentage of CD4+ Tem and CD8+ Tcm and Tem positive for IFNgamma increased significantly following inoculation, surpassing that of controls by 28 dpi or earlier. These results suggest that memory T cells play a role in protective immunity and suggest that studying these cell populations may be a surrogate immunity marker in ASF vaccination.