Schistosomiasis and Impaired Response to Antiretroviral Therapy Among HIV-Infected Patients in Tanzania

Abstract

Schistosomiasis affects over 230 million people worldwide, 90% of whom live in sub-Saharan Africa(1). Data suggests helminthic infections like schistosomiasis may hasten HIV progression in co-infected patients(2,3). Helminths induce chronic immune activation, shifting from a T-helper cell type 1 (Th1) to type 2 (Th2) immune response. Th2-lymphocytes down-regulate cytotoxic effects of CD8+ T-lymphocytes, leading to an altered cytokine profile with increased viral replication(4–7). Studies have shown that treating ascariasis or filariasis improves CD4+ T-cell counts (CD4 counts) and viral loads in HIV-infected patients(8, 9). Little research has explored the specific interaction between schistosomiasis and HIV, but one study yielded concerning results. Antiretroviral therapy (ART)-naive HIV-infected patients with schistosome co-infection who were randomized to delayed anti-schistosome treatment with praziquantel after three months had larger increases in HIV RNA levels and greater declines in CD4 counts than patients treated immediately(10). Despite this possible interaction, schistosomiasis screening is not currently recommended for HIV-infected patients in many endemic countries, including Tanzania. Also, no study has yet assessed impact of schistosomiasis on ART response. We hypothesized that schistosome infection may adversely affect HIV-infected patients’ responses to ART. We conducted a retrospective cohort study to explore this issue at Bugando Medical Centre (BMC) near Lake Victoria in Tanzania, where schistosomiasis is hyper-endemic.