HAART and CD4+ T cells protect positive people from toxoplasmic encephalitis

A study of the French Hospital Database on HIV that compares the incidence and risk factors for toxoplasmic encephalitis before and after the widespread introduction of highly active antiretroviral therapy (HAART) concludes that HAART and immune recovery help protect people from HIV-related toxoplasmosis.

The protection provided by cotrimoxazole against toxoplasmic encephalitis (TE) is greater when HAART boosts the patient’s CD4+ T cell count, report Dr Sophie Abgrall and colleagues at L’Institut National de la Santé et de la Recherche Médicale at Paris, France. And they go on to say, in the 15 November issue of the journal Clinical Infectious Diseases, that in some patients prophylaxis with cotrimoxazole can be safely discontinued.

The researchers studied the occurrence of TE in 19,598 positive people between 1992 and 1995, before the use of HAART, and compared them with 17,016 positive people between 1996 and 1998, after the introduction of HAART. All those studied had CD4+ T cell counts of 200 or fewer cells/mm3. They found that the incidence of TE decreased from 3.9 cases per 100 person years in the first period, to 1.0 cases per 100 person years in the second period.

After adjustment for know risk factors for TE, patients who received cotrimoxazole prophylaxis had a lower risk of TE – down by 36 per cent in the period before HAART, and by 46 per cent in the period after HAART was introduced. For patients treated with cotrimoxazole at inclusion, discontinuation of cotrimoxazole increased the risk of TE in both periods.

The risk of TE was significantly increased in patients with CD4+ T cell counts below 100 cells/mm3 and in patients with higher levels of plasma HIV RNA. Among patients whose CD4+ T cell counts increased to greater that 200 cells/mm3 while taking HAART, the incidence of TE was 0.1 cases per 100 person years and was not increased by the discontinuation of cotrimoxazole.

The researchers conclude: “This prospective cohort study further supports the efficacy of cotrimoxazole prophylaxis in protection against toxoplasmic encephalitis, with a further protective effect of HAART and immune recovery, and a deleterious effect of cotrimoxazole discontinuation in immunodeficient patients.”

“Prophylaxis against toxoplasmosis and potent antiretroviral therapies are still necessary for strongly immunodeficient HIV-infected patients when immunosuppression progresses,” they write, adding that “discontinuation of cotrimoxazole prophylaxis seems feasible for patients who have a sustained increase in the CD4 cell count to more than 200 million cells/L during HAART.”