Antigen-specific T cell responses induced by Towne cytomegalovirus (CMV) vaccine in CMV-seronegative vaccine recipients.

BACKGROUND

Towne cytomegalovirus (CMV) vaccine is safe and immunogenic, though its protective efficacy has yet to be optimized.

OBJECTIVE

Describe antigen-specific T cell responses to Towne vaccination.

STUDY DESIGN

3000 pfu Towne CMV vaccine were given to 12 CMV-seronegative volunteers. CMV-specific CD4+ and CD8+ T cell proliferation and IFNgamma expression were measured by flow cytometry after stimulation with CMV lysate or peptides.

RESULTS

All vaccinees developed CD4+ and CD8+ T cell proliferation and CD4+ T cell IFNgamma responses to multiple CMV antigens, but their CD8+ T cells had low or undetectable IFNgamma responses to pp65 peptide pool. The seven HLA-A2+ subjects had higher CD8+ T cell proliferation and IFNgamma responses to IE than pp65, and two never developed CD8+ T cell IFNgamma responses to pp65. Peak CD4+ T cell IFNgamma responses to CMV lysate were lower than values observed in natural CMV seropositives. Initial CD4+ and CD8+ T cell responses to lysate and pp65 waned after 12 months to levels that were lower than those in healthy CMV seropositives, while vaccinees' CD8+ T cell responses to IE were robust and prolonged.

CONCLUSION

Correlating CMV antigen-specific T cell responses with clinical protective efficacy may facilitate future CMV vaccine development.