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

Area of Science:

• Immunology
• Virology
• Vaccinology

Background:

• The Eilat (EILV)/chikungunya virus (CHIKV) vaccine offers single-dose protection against wild-type CHIKV in animal models.
• The specific immune mechanisms behind this vaccine-induced protection are not fully understood.
• Gamma delta (γδ) T cells are known to mitigate tissue inflammation and damage during wild-type CHIKV infection.

Purpose of the Study:

• To investigate the role of γδ T cells in the host protection conferred by EILV/CHIKV vaccination.
• To elucidate the immune mechanisms by which γδ T cells contribute to vaccine-induced immunity against CHIKV.

Main Methods:

• Utilized γδ T cell-deficient (TCRδ^-/-) mice to assess the impact of γδ T cell absence on vaccine efficacy.
• Analyzed CHIKV-specific CD8+ T cell responses, antibody production, and memory B cell generation post-vaccination.
• Measured innate immune cytokine levels and antigen-presenting cell (APC) activation in vaccinated mice.

Main Results:

• TCRδ^-/- mice exhibited impaired CHIKV-specific CD8+ T cell, antibody, and memory B cell responses after EILV/CHIKV vaccination.
• γδ T cells rapidly expanded following EILV/CHIKV vaccination.
• TCRδ^-/- mice showed reduced innate immune cytokine levels and defective APC activation.
• Both antibodies and CD8+ T cells from vaccinated mice were essential for protecting interferon receptor-deficient mice against lethal CHIKV challenge.

Conclusions:

• γδ T cells play a significant role in EILV/CHIKV-induced host protection against wild-type CHIKV infection.
• These cells enhance vaccine efficacy by promoting APC maturation and T cell priming.
• γδ T cells are critical for inducing robust humoral immune responses following EILV/CHIKV vaccination.