Background: It is hypothesised that Th₂ immunological environment associated with Schistosoma mansoni infection might favour replication of HIV-1 in co-infected individuals, results in increased viral loads. On the other hand, deworming using praziquantel might result in reduction of HIV-1 viral loads and increased CD4⁺ cell counts. This study was therefore, carried out to compare HIV -1 plasma loads, CD4-Th2-lymphocytes and the effects of praziquantel treatment on HIV-1 plasma loads and CD4+ cell counts among HIV-1 seropositive individuals infected or uninfected with S. mansoni .

Methodology: A 9-month prospective longitudinal study was conducted among HIV-1 infected individuals aged 21-55 years with CD4⁺ cell counts ≥ 350cells/µL in fishing villages of North-Western Tanzania. Single stool samples were examined for S. mansoni eggs using Kato Katz technique at 6-month follow-up and 12 weeks after treatment. Venous blood samples were collected at baseline, at three and six-month follow-up and 12 weeks after praziquantel treatment for HIV-1 plasma viral loads and CD4⁺ cell quantification.

Results: Of the 50 HIV-1 infected participants at baseline, 44% (22/50, 95%CI; 30.58-58.35) were found to be co-infected with S. mansoni at 6-month follow-up with a mean of 93.26GM-epg (95%CI: 60.42-143.95). The median CD4⁺ cell counts did not differ significantly between individuals infected with HIV-1 and those co-infected with HIV-1 and S. mansoni at baseline ( P =0.62), 3-month ( P =0.64) and 6-month ( P =0.41) follow-up. Monthly decrease in CD4⁺ cells did not differ significantly between the two groups at all follow-up points (-30.39cell/µL versus -31.35cells/µL, P =0.89). Those infected with S. mansoni had a significantly higher mean log₁₀ HIV-1 plasma viral load at baseline (5.98 ± 3.06 versus 9.21 ± 1.91copies/ml, P <0.0001) and 3-month follow-up (8.19 ± 2.17 versus 9.44 ± 1.99copies/ml, P <0.042) compared to those infected with HIV-1 only. This difference was not evident at the time of S. mansoni diagnosis at 6-month time point. Praziquantel treatment in co-infected individuals (n=12) did not result in any change in CD4⁺ cell counts and mean HIV-1 plasma viral loads (t=-0.9156, P =0.38), comparing baseline and 3-month follow-up after treatment. No correlation was observed between log S. mansoni egg counts and log₁₀ HIV-1 RNA viral loads (r=-0.066, P =0.77) at six-month follow-up in co-infected individuals (n=22).

Conclusion: HIV-1 plasma viral loads varied significantly among mono and co-infected individuals at baseline and 3-month follow-up. However, CD4⁺ cell counts did not vary between the two groups at all follow-up time points. Praziquantel treatment of co-infected individuals did not result in changes in CD4⁺ cell counts and HIV-1 plasma viral loads.