Influence of antigen exposure on the loss of long-term memory to childhood vaccines in HIV-infected patients

The role of antigen exposure and of CD4 cell deficiency in the long-term persistence of immune memory to childhood vaccines remains uncertain, particularly during HIV infection. We analyzed in vaccinated ART-treated HIV+ patients with undetectable plasma HIV and CD4 cells >250/mm3 the persistence of two memory cell pools: effector IFNγ-producing and proliferative central memory T cells against two vaccines: (i) vaccinia against the eradicated smallpox virus, and (ii) BCG against Mtb, a persistent pathogen. None of the HIV+ patients had IFNγ-effector cells against VV while the one patient with BCG-specific effector T cells had a recent history of tuberculosis. Proliferative responses were detectable but showed significantly lower frequency and intensity of VV-specific than tuberculin-specific responses, independently of the CD4 nadir. Thus, differential patterns of persistence or recovery of T cell memory pools against childhood vaccines are observed in treated HIV infection that are governed by antigen exposure.