Expansion, reexpansion, and recall-like expansion of Vgamma2Vdelta2 T cells in smallpox vaccination and monkeypox virus infection.

Little is known about the in vivo kinetics of T-cell responses in smallpox/monkeypox. We showed that macaque Vgamma2Vdelta2 T cells underwent 3-week-long expansion after smallpox vaccine immunization and displayed simple reexpansion in association with sterile anti-monkeypox virus (anti-MPV) immunity after MPV challenge. Virus-activated Vgamma2Vdelta2 T cells exhibited gamma interferon-producing effector function after phosphoantigen stimulation. Surprisingly, like alphabeta T cells, suboptimally primed Vgamma2Vdelta2 T cells in vaccinia virus/cidofovir-covaccinated macaques mounted major recall-like expansion after MPV challenge. Finally, Vgamma2Vdelta2 T cells localized in inflamed lung tissues for potential regulation. Our studies provide the first in vivo evidence that viruses, despite their inability to produce exogenous phosphoantigen, can induce expansion, reexpansion, and recall-like expansion of Vgamma2Vdelta2 T cells and stimulate their antimicrobial cytokine response.