Long-Term Follow-Up of T Cell Immunity Against Orthopoxviruses in People Living with HIV After Vaccination and...

After the 2022 mpox outbreak also outside Africa, risk groups including people living with HIV (PLWH) were vaccinated with the Modified Vaccinia Ankara-Bavarian Nordic vaccine (MVA-BN). Previous data on PLWH showed that two vaccinations induced specific T cell responses in 64% of the patients and natural monkeypox virus (MPXV) infection in 100%. The initial T cell response assay took place at a median of approximately 100 days post-vaccination and 300 days post-infection.

This study investigates the durability of T cell immunity in PLWH by retesting patients approximately two years after initial assessment. We were able to retest 27 of 33 vaccinated patients and 7 of 10 patients after MPXV infection. T cells were stimulated with the same orthopoxvirus-derived peptide pools as in the initial study, and interferon (IFN)-γ and interleukin (IL)-2 ELISpot assays were performed.

The ELISpot assays showed specific T cell responses in 59% and 86% of twice vaccinated and previously infected patients, respectively. Paired analysis revealed no significant differences between previous and current data (short- and long-term follow-up), with IL-2 ELISpot results showing positive correlations at both time points (r = 0.67, p = 0.0001). Long-term IFN-γ responses after MPXV infection were 4.3 times higher (p < 0.01), and IL-2 responses were 2.9 times higher (p = 0.05) than after vaccination.

Our data indicates that T cell responses to Orthopoxviruses remain overall stable for 2-3 years in PLWH, with long-term immunity being stronger after natural MPXV infection than after two vaccinations.