HealthDay News — HIV-infected patients lose immunity to smallpox despite childhood vaccination and immune reconstitution with antiretroviral therapy, according to a study published online Dec. 23 in The Journal of Infectious Diseases.

Archana Thomas, from the Oregon Health & Science University in Beaverton, and colleagues conducted a matched cohort study involving 50 pairs of HIV+ and HIV− women. To measure T cells elicited after childhood smallpox vaccination, total memory T cell responses were measured after anti-CD3 stimulation or after vaccinia virus stimulation. Vaccinia-specific antibodies were measured.

The researchers found that after anti-CD3 stimulation, there was no difference between HIV+ and HIV− individuals in terms of CD4+ responses, although significantly higher T cell responses were seen among HIV+ individuals. In contrast, among HIV+ individuals, there was a significant loss in vaccinia-specific CD4+ T cell memory, while antiviral CD8+ T cell memory remained intact. Among HIV− individuals, vaccinia-specific antibodies were maintained indefinitely (half-life, infinity), but among HIV+ individuals, they declined rapidly (half-life, 39 years).

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“These data suggest that despite successful use of antiretroviral therapy, HIV infection is associated with a significant loss in virus-specific CD4+ T cell memory and antiviral antibody responses that may leave a sizeable proportion of HIV+ people at increased risk for virus-associated disease manifestations,” the authors write.

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