People who have schistosome infection at the time of HIV-seroconversion develop adverse HIV outcomes more slowly than those who do not have schistosome infection, according to a study published in PLOS Neglected Tropical Diseases.
Previous research has indicated that the presence of schistosome infection increased the risk for HIV and raising HIV viral concentrations. As a result, researchers investigated the effect of a schistosome infection on HIV. They hypothesized that the presence of schistosome parasites at the time of acquiring the HIV-1 infection would negatively impact the antiviral immune response and cause HIV to progress twice as fast or lead to death when compared with people who did not have a schistosome infection at the time of HIV-1 seroconversion.
Using a large cohort from the TAZAMA project, which is based on longitudinal HIV-testing data from northwest Tanzania, study investigators identified individuals who became HIV-1-seropositive between September 2006 and February 2016. To be included in the study, participants also needed to have a dried blood spot or serum available for schistosome infection testing.
Researchers analyzed the results of participants who had seroconverted to HIV-1 (N=172). Using a competing risk analysis, the researchers evaluated differences in reaching CD4 counts of <350 cells/μL or death in participants with (n=43) and without (n=129) schistosome infections. Surprisingly, an 82% reduction in risk was observed for people who had the schistosome infection (subHazard Ratio = 0.18 [95% CI, 0.068-0.500], P =.001), even after adjusting for demographic, clinical, and time-dependent covariates.
Study limitations included approximations of seroconversion dates and the inability to test for viral loads and additional related markers.
Researchers concluded their study by noting that “schistosome infection at the time of HIV-1 acquisition may delay HIV-1 disease progression. Complementary findings from a variety of other studies of HIV-1/helminth co-infections strengthen the likelihood that this result is not spurious. Plausible mechanisms by which schistosome infection could delay HIV-1 disease progression include induction of Th17 or T reg cells or disrupting the Th17/Treg ratio. This work highlights the need for additional studies to examine these immunological interactions between the two pathogens on a longer-term scale.”
This study was supported by the NIH and a Kellan Junior Faculty Fellowship from Weill Cornell Medicine.
Colombe S, Machemba R, Mtenga B, et al. Impact of schistosome infection on long-term HIV/AIDS outcomes [published on July 2, 2018]. PLOS Neglected Tropical Diseases. doi: 10.1371/journal. pntd.0006613