Impaired CD4-cell immune reconstitution upon HIV therapy in patients with toxoplasmic encephalitis compared to patients with pneumocystis pneumonia as AIDS indicating disease

OBJECTIVES: There is only little data on immune reconstitution in antiretroviral naïve AIDS-patients with toxoplasmosis. The observation of several cases with reduced increase of CD4-cells upon start of antiretroviral treatment (ART) prompted us to investigate the topic using the ClinSurv cohort. METHODS: 17 German HIV treatment centers contribute to ClinSurv, a multicentre observational cohort under the auspices of the Robert Koch Institute. We retrospectively selected all antiretroviral-naïve patients with toxoplasmic encephalitis (TE) and -as comparator group -with pneumocystosis (PCP) between January 1999 and December 2005. RESULTS: A total of 257 patients were included in the analysis, 61 with TE and 196 with PCP. Demographic baseline data showed differences with regard to gender, transmission group, and baseline CD4(+ )counts (60.9 vs. 44.7/μl, p = 0.022). After ART-initiation the increase in CD4(+ )lymphocytes was lower in the TE-versus the PCP-group in the first, second and fourth three-month-period (74.4 vs. 120.3/μl, p = 0.006; 96.6 vs. 136.2/μl, p = 0.021; 156.5 vs. 211.5/μl, p = 0.013). Viral load (VL) was higher in the PCP-group at baseline (4.46 log(10)cop/ml vs. 5.00 log(10)cop/ml, p = 0.008), while virological success of ART was equal. CONCLUSIONS: Our data show for the first time that the average CD4(+ )T-cell increase of patients with toxoplasmosis is impaired compared to PCP-patients. Most clinicians would not be prepared to discontinue follow-up TE-therapy unless CD4(+ )counts of 200/μl are reached. Explanation for our finding might be the myelosuppressive side effect of pyrimethamine, possible interactions of toxoplasmosis therapy with ART, or an unknown direct biological influence of toxoplasmosis on immune restoration.