Current guidelines recommend that primary Toxoplasma gondii prophylaxis can be safely discontinued in HIV and T. gondii co-infected patients with suppressed viraemia on antiretroviral therapy (ART) and a CD4 cell count >200 cells/mm3. Whether such a policy can be extended to patients with CD4 cell counts between 100-200 cells/mm3 is unknown.
The Collaboration of Observational HIV Epidemiological Research in Europe (COHERE) included data from from 10 European cohorts on 11,015 HIV and T. gondii co-infected patients who started taking ART after 1997. T. gondii infection was considered present if patients were T. gondii IgG antibody seropositive. Central nervous system (CNS) toxoplasmosis was diagnosed according to the 1993 CDC case definition. Multivariate Poisson regression models were used to model incidence rate ratios (IRRs) of CNS toxoplasmosis.
There were 99 CNS toxoplasmosis episodes during 79,220 person-years of follow-up (PYFU). The incidence of CNS toxoplasmosis stratified by current CD4 cell count, viral load (VL), and use of prophylaxis is shown in the figure. Among patients who had a current CD4 cell count of 100-200 cells/mm3 and a VL<400 copies/mL, incidence of CNS toxoplasmosis was 0.7 episodes per 1000 PYFU (95% CI, 0.02-4.0; 1 event during 1,390 PYFU) in those receiving T. gondii prophylaxis and 0.8 episodes per 1,000 PYFU (95% CI, 0.02-4.3; 1 event during 1,294 PYFU), in those who stopped prophylaxis. The incidence of CNS toxoplasmosis in virologically suppressed patients on ART (VL<400 copies/mL) with CD4 >200 cells/mm3 on or off primary T. gondii prophylaxis was 0.9 (95% CI, 0.1-3.3) and 0.2 (95% CI, 0.1-0.3) episodes per 1,000 PYFU, respectively. The predictors of CNS toxoplasmosis among patients with a current CD4 cell count above 100 cells/mm3 were: previous AIDS diagnosis (IRR, 2.86; 95% CI, 1.40–5.86; P=.004); doubling CD4 cell count/year (IRR, 0.30; 95% CI, 0.19–0.47; P<.001); and, detectable viral load (IRR, 4.25; 95% CI, 1.97–9.16; P<.001), whereas primary prophylaxis was not a significant predictor (IRR, 0.79; 95% CI, 0.33–1.87; P=.59).
The incidence of primary CNS toxoplasmosis among virologically suppressed patients on ART and who had CD4 cell counts >100 cells/mm3 was very low regardless of prophylaxis use. Extending current guidelines for safely discontinuing primary T. gondii prophylaxis to patients with CD4 counts of 100-200 cells/mm3 and suppressed VL would be appropriate.