In chronic HIV infection, antiretroviral therapy–induced normalization of CD4⁺ T cell counts (immune reconstitution [IR]) is associated with a decreased incidence of opportunistic diseases. However, some individuals remain at risk for opportunistic diseases despite prolonged normalization of CD4⁺ T cell counts. Deficient Epstein-Barr virus (EBV)-specific CD4⁺ T cell function may explain the occurrence of EBV-associated opportunistic malignancy—such as primary central nervous system (PCNS) lymphoma—despite recovery of absolute CD4⁺ T cell counts. Absolute CD4⁺ T cell counts and EBV-specific CD4⁺ T cell-dependent interferon-γ production were assessed in six HIV-positive individuals prior to development of PCNS lymphoma (“cases”), and these values were compared with those in 16 HIV-infected matched participants with no sign of EBV-associated pathology (“matched controls”) and 11 nonmatched HIV-negative blood donors. Half of the PCNS lymphoma patients fulfilled IR criteria (defined here as CD4⁺ T cell counts ≥500/μl blood). EBV-specific CD4⁺ T cells were assessed 0.5–4.7 y prior to diagnosis of lymphoma. In 0/6 cases versus 13/16 matched controls an EBV-specific CD4⁺ T cell response was detected (p = 0.007; confidence interval for odds ratio [0–0.40]). PCNS lymphoma patients also differed with regards to this response significantly from HIV-negative blood donors (p < 0.001, confidence interval for odds ratio [0–0.14]), but there was no evidence for a difference between HIV-negative participants and the HIV-positive matched controls (p = 0.47). Irrespective of absolute CD4⁺ T cell counts, HIV-positive patients who subsequently developed PCNS lymphoma lacked EBV-specific CD4⁺ T cell function. Larger, ideally prospective studies are needed to confirm these preliminary data, and clarify the impact of pathogen-specific versus surrogate marker-based assessment of IR on clinical outcome.

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