γδ T Cells Mediate Protective Immunity Following Vaccination with an Insect-Based Chikungunya Fever Vaccine in Mice

Rodriguez L, Adam A, Luo H, Osman SR, Plante K, Rossi SL, Weaver SC, Wang T. γδ T Cells Mediate Protective Immunity Following Vaccination with an Insect-Based Chikungunya Fever Vaccine in Mice. Pathogens. 2025 Aug 30;14(9):863. doi: 10.3390/pathogens14090863. PMID: 41011763; PMCID: PMC12472593. Abstract: Eilat (EILV)/chikungunya virus (CHIKV) is a chimeric virus that contains the nonstructural proteins and cis-acting sequences of EILV and the structural proteins of CHIKV. EILV/CHIKV vaccination is known to protect with a single dose against wild-type (WT) CHIKV challenge in mice and non-human primates. The underlying immune mechanism of the vaccine-induced host protection remains unknown. γδ T cells react to WT CHIKV infection by controlling the virus-induced tissue inflammation and damage. Here, we found that γδ T cells contribute to EILV/CHIKV-induced host protection against WT CHIKV infection. TCRδ−/− mice, which are deficient of γδ T cells, had impaired CHIKV-specific CD8+ T cell responses, antibody production and memory B cell responses following vaccination. Both antibody and CD8+ T cells of EILV/CHIKV-vaccinated mice were required for protection type I interferon receptor deficient mice from lethal WT CHIKV infection. Moreover, γδ T cells expanded quickly in response to EILV/CHIKV vaccination. TCRδ−/− mice, had lower levels of innate immune cytokines and impaired activation of antigen presenting cell (APCs). Overall, γδ T cells contribute to EILV/CHIKV-induced host protection by promoting APC maturation, T cell priming and the induction of humoral immune responses upon EILV/CHIKV vaccination. Dataset description: This dataset contains all PRISM files used to generate the accompanying figures in the manuscript. The PRISM files contain both the data tables used to generate the figures as well as the statistical analyses presented in the manuscript. Fig 1B-1C: Viral plaque assays for WT and TCRδ−/− mice challenged with CHIKV. Fig 2A-2F: CD8+ T cell responses in WT and TCRδ−/− mice following EILV/CHIKV vaccination and WT CHIKV challenge, as well as weight change (2E) and survival (2F) post-infection. Fig 3A-3H: Antibody and memory B cell responses in WT and TCRδ−/− mice following EILV/CHIKV vaccination, as well as plaque assays (3F), weight change (3G), and survival (3H) post-infection. Fig 4B-4C: Weight change (4B) and survival (4C) post-infection for mock control, WT and TCRδ−/− mice vaccinated i.p. with 108 PFU EILV/CHIK. At 28 DPV, pooled sera and purified CD8+ T cells of EILV/CHIKV-vaccinated WT and TCRδ−/− mice were transferred to AB6 mice 24 h before CHIKV infection. Fig 5A-5E: Splenocytes were collected at 2 and 4 DPV, counted and stained for CD3 and TCR γδ and analyzed using flow cytometry. (5A,B). Percent positive and total cell number of γδ T cells. n = 4–8. (5C). Blood cytokine levels measured by Q-PCR assay. (5D,E). At 5 DPV, splenic DCs and macrophages were stained for surface activation markers and analyzed by flow cytometry. Supp. Fig 1A-1B: Weight loss in EILV/CHIKV- vaccinated mice following WT CHIKV infection. Supp. Fig 2B: T cell responses in WT and TCRδ−/− mice following EILV/CHIKV vaccination. Supp. Fig 3: Memory B cell responses in WT and TCRδ−/− mice following EILV/CHIKV vaccination.