The Impact of Antiretroviral Therapy on Malaria Parasite Transmission

Abstract

Coendemicity between the human immunodeficiency virus (HIV) and Plasmodium parasites, the causative agents of acquired immunodeficiency syndrome (AIDS) and malaria, respectively, occurs in several regions around the world. Although the impact of the interaction between these two organisms is not well understood, it is thought that the outcome of either disease may be negatively influenced by coinfection. Therefore, it is important to understand how current first-line antiretroviral therapies (ART) might impact Plasmodium infection in these regions. Here, we describe the effect of 18 antiretroviral compounds and of first-line ART on the blood and sporogonic stages of Plasmodium berghei in vitro and in vivo. We show that the combination zidovudine + lamivudine + lopinavir/ritonavir (LPV/r), employed as first-line HIV treatment in the field, has a strong inhibitory activity on the sporogonic stages of P. berghei and that several non-nucleoside reverse transcriptase inhibitors (NNRTI) have a moderate effect on this stage of the parasite's life cycle. Our results expose the effect of current first-line ART on Plasmodium infection and identify potential alternative therapies for HIV/AIDS that might impact malaria transmission.

Keywords: HIV; Plasmodium; antiretroviral; coinfection; malaria.

FIGURE 1

In vitro activity of ARV compounds on P. berghei sporogonic stages. (A) Timeline of P. berghei sporogonic development and drug incubation periods. (B) Activity of ARV compounds on the conversion of zygotes/gametes into ookinetes. (C) Activity of ARV compounds on oocyst formation. (D) Activity of ARV compounds on oocyst development. All compounds were employed at 10 μM. Bars correspond to RLU measurements represented as the percentage of RLU of the DMSO control. Results are expressed as the mean ± SD. Statistically significant differences between control and treated conditions were analyzed using the Kruskal–Wallis test. N = 3–6. ***P < 0.001; **P < 0.01; *P < 0.05. Detailed statistical analysis is presented in Supplementary Table S2.

FIGURE 2

In vitro activity of ART on the P. berghei sporogonic stages. (A) Effect of first-line ART employed for adults and adolescents and for children under 3 years old and suggested substitutions on the conversion of zygotes/gametes into ookinetes. (B) Activity of first-line ART and suggested substitutions on oocyst formation. (C) Activity of first-line ART and suggested substitutions on oocyst development. All compounds were screened at 10 μM; TDF, tenofovir; 3TC, lamivudine; EFV, efavirenz; ETV, etravirine; RPV, rilpivirine; AZT, zidovudine; LPV/r, lopinavir/ritonavir; SQV, saquinavir; IDV, indinavir. RLU measurements represented as the percentage of RLU of the DMSO control. Statistically significant differences between control and treated conditions were analyzed using the Kruskal–Wallis test. Results are expressed as the mean ± SD. N = 3–4. ***P < 0.001; **P < 0.01; *P < 0.05.

FIGURE 3

In vivo activity of ART on blood and transmission stages of P. berghei. (A) Schematics of drug administration and sample collection schedules. (B–D) Activity of ART and suggested alternative drug combinations on P. berghei parasitemia (B), female (C), and male (D) gametocytemia in mice. Results are expressed as the mean percentage of syto 61-positive events ± SD for parasitemia, percentage of RFP⁺ events for female gametocytemia and percentage of GFP⁺ for male gametocytemia. (E) Impact of ART and suggested alternatives on P. berghei mosquito infection measured as oocyst intensity per mosquito. Results are represented individually by number of parasites per mosquito midgut. Horizontal red and black lines represent median and mean, respectively. (F) Prevalence of oocyst infection in mosquitoes infected with P. berghei expressed as the mean ± SD. (G) Average P. berghei oocyst infection intensity upon ART and suggested alternatives in infected mosquitoes. Box plot represent the median and 25th and 75th percentile. N = 2. ***P < 0.001; **P < 0.01. In (B–D), statistically significant differences between control and treated conditions for blood stage P. berghei development were analyzed using a non-linear regression analysis. In (E), Kruskal–Wallis test was used to calculate P values and determine the significance of parasite numbers. A chi-squared test was used to compare infection prevalence values in (F). Detailed statistical analysis is presented in Supplementary Table S3.