Emmanuel Arinaitwe

Artemether-Lumefantrine Versus Dihydroartemisinin-Piperaquine for Falciparum Malaria: A Longitudinal, Randomized Trial in Young Ugandan Children

BACKGROUND Artemisinin-based combination therapies are now widely recommended as first-line treatment for uncomplicated malaria. However, which therapies are optimal is a matter of debate. We aimed to compare the short- and longer-term efficacy of 2 leading therapies in a cohort of young Ugandan children. METHODS A total of 351 children aged 6 weeks to 12 months were enrolled and followed up for up to 1 year. Children who were at least 4 months of age, weighted at least 5 kg, and had been diagnosed as having their first episode of uncomplicated malaria were randomized to receive artemether-lumefantrine or dihydroartemisinin-piperaquine. The same treatment was given for all subsequent episodes of uncomplicated malaria. Recrudescent and new infections were distinguished by polymerase chain reaction genotyping. Outcomes included the risk of recurrent malaria after individual treatments and the incidence of malaria treatments for individual children after randomization. RESULTS A total of 113 children were randomized to artemether-lumefantrine and 119 to dihydroartemisinin-piperaquine, resulting in 320 and 351 treatments for uncomplicated falciparum malaria, respectively. Artemether-lumefantrine was associated with a higher risk of recurrent malaria after 28 days (35% vs 11%; P = .001]). When the duration of follow-up was extended, differences in the risk of recurrent malaria decreased such that the overall incidence of malaria treatments was similar for children randomized to artemether-lumefantrine, compared with those randomized to dihydroartemisinin-piperaquine (4.82 vs 4.61 treatments per person-year; P = .63). The risk of recurrent malaria due to recrudescent parasites was similarly low in both treatment arms. CONCLUSIONS Artemether-lumefantrine and dihydroartemisinin-piperaquine were both efficacious and had similar long-term effects on the risk of recurrent malaria. Clinical trials registration. NCT00527800.

Malaria Transmission, Infection, and Disease at Three Sites with Varied Transmission Intensity in Uganda: Implications for Malaria Control

The intensification of control interventions has led to marked reductions in malaria burden in some settings, but not others. To provide a comprehensive description of malaria epidemiology in Uganda, we conducted surveillance studies over 24 months in 100 houses randomly selected from each of three subcounties: Walukuba (peri-urban), Kihihi (rural), and Nagongera (rural). Annual entomological inoculation rate (aEIR) was estimated from monthly Centers for Disease Control and Prevention (CDC) light trap mosquito collections. Children aged 0.5-10 years were provided long-lasting insecticidal nets (LLINs) and followed for measures of parasite prevalence, anemia and malaria incidence. Estimates of aEIR were 2.8, 32.0, and 310 infectious bites per year, and estimates of parasite prevalence 7.4%, 9.3%, and 28.7% for Walukuba, Kihihi, and Nagongera, respectively. Over the 2-year study, malaria incidence per person-years decreased in Walukuba (0.51 versus 0.31, P = 0.001) and increased in Kihihi (0.97 versus 1.93, P < 0.001) and Nagongera (2.33 versus 3.30, P < 0.001). Of 2,582 episodes of malaria, only 8 (0.3%) met criteria for severe disease. The prevalence of anemia was low and not associated with transmission intensity. In our cohorts, where LLINs and prompt effective treatment were provided, the risk of complicated malaria and anemia was extremely low. However, malaria incidence was high and increased over time at the two rural sites, suggesting improved community-wide coverage of LLIN and additional malaria control interventions are needed in Uganda.

IFNγ/IL-10 Co-producing Cells Dominate the CD4 Response to Malaria in Highly Exposed Children

Although evidence suggests that T cells are critical for immunity to malaria, reliable T cell correlates of exposure to and protection from malaria among children living in endemic areas are lacking. We used multiparameter flow cytometry to perform a detailed functional characterization of malaria-specific T cells in 78 four-year-old children enrolled in a longitudinal cohort study in Tororo, Uganda, a highly malaria-endemic region. More than 1800 episodes of malaria were observed in this cohort, with no cases of severe malaria. We quantified production of IFNγ, TNFα, and IL-10 (alone or in combination) by malaria-specific T cells, and analyzed the relationship of this response to past and future malaria incidence. CD4+ T cell responses were measurable in nearly all children, with the majority of children having CD4+ T cells producing both IFNγ and IL-10 in response to malaria-infected red blood cells. Frequencies of IFNγ/IL10 co-producing CD4+ T cells, which express the Th1 transcription factor T-bet, were significantly higher in children with ≥2 prior episodes/year compared to children with <2 episodes/year (P<0.001) and inversely correlated with duration since malaria (Rho = −0.39, P<0.001). Notably, frequencies of IFNγ/IL10 co-producing cells were not associated with protection from future malaria after controlling for prior malaria incidence. In contrast, children with <2 prior episodes/year were significantly more likely to exhibit antigen-specific production of TNFα without IL-10 (P = 0.003). While TNFα-producing CD4+ T cells were not independently associated with future protection, the absence of cells producing this inflammatory cytokine was associated with the phenotype of asymptomatic infection. Together these data indicate that the functional phenotype of the malaria-specific T cell response is heavily influenced by malaria exposure intensity, with IFNγ/IL10 co-producing CD4+ T cells dominating this response among highly exposed children. These CD4+ T cells may play important modulatory roles in the development of antimalarial immunity.

Protective efficacy of co-trimoxazole prophylaxis against malaria in HIV exposed children in rural Uganda: a randomised clinical trial

Objective To evaluate the protective efficacy of co-trimoxazole prophylaxis against malaria in HIV exposed children (uninfected children born to HIV infected mothers) in Africa. Design Non-blinded randomised control trial Setting Tororo district, rural Uganda, an area of high malaria transmission intensity Participants 203 breastfeeding HIV exposed infants enrolled between 6 weeks and 9 months of age Intervention Co-trimoxazole prophylaxis from enrolment until cessation of breast feeding and confirmation of negative HIV status. All children who remained HIV uninfected (n=185) were then randomised to stop co-trimoxazole prophylaxis immediately or continue co-trimoxazole until 2 years old. Main outcome measure Incidence of malaria, calculated as the number of antimalarial treatments per person year. Results The incidence of malaria and prevalence of genotypic mutations associated with antifolate resistance were high throughout the study. Among the 98 infants randomised to continue co-trimoxazole, 299 malaria cases occurred in 92.28 person years (incidence 3.24 cases/person year). Among the 87 infants randomised to stop co-trimoxazole, 400 malaria cases occurred in 71.81 person years (5.57 cases/person year). Co-trimoxazole prophylaxis yielded a 39% reduction in malaria incidence, after adjustment for age at randomisation (incidence rate ratio 0.61 (95% CI 0.46 to 0.81), P=0.001). There were no significant differences in the incidence of complicated malaria, diarrhoea, pneumonia, hospitalisations, or deaths between the two treatment arms. Conclusions Co-trimoxazole prophylaxis was moderately protective against malaria in HIV exposed infants when continued beyond the period of HIV exposure despite the high prevalence of Plasmodium genotypes associated with antifolate resistance. Trial registration Clinical Trials NCT00527800

Increasing incidence of malaria in children despite insecticide-treated bed nets and prompt anti-malarial therapy in Tororo, Uganda

BackgroundThe burden of malaria has decreased in parts of Africa following the scaling up of control interventions. However, similar data are limited from high transmission settings.MethodsA cohort of 100 children, aged six weeks to 10 months of age, were enrolled in an area of high malaria transmission intensity and followed through 48 months of age. Children were given a long-lasting insecticide-treated bed net (LLIN) at enrolment and received all care, including monthly blood smears and treatment with artemisinin-based combination therapy (ACT) for uncomplicated malaria, at a dedicated clinic. The incidence of malaria was estimated by passive surveillance and associations between malaria incidence and age, calendar time and season were measured using generalized estimating equations.ResultsReported compliance with LLINs was 98% based on monthly routine evaluations. A total of 1,633 episodes of malaria were observed, with a median incidence of 5.3 per person-year (PPY). There were only six cases of complicated malaria, all single convulsions. Malaria incidence peaked at 6.5 PPY at 23 months of age before declining to 3.5 PPY at 48 months. After adjusting for age and season, the risk of malaria increased by 52% from 2008 to 2011 (RR 1.52, 95% CI 1.10-2.09). Asymptomatic parasitaemia was uncommon (monthly prevalence <10%) and rarely observed prior to 24 months of age.ConclusionsIn Tororo, despite provision of LLINs and prompt treatment with ACT, the incidence of malaria is very high and appears to be rising. Additional malaria control interventions in high transmission settings are likely needed.Trial registrationCurrent Controlled Trials Identifier NCT00527800

Novel serologic biomarkers provide accurate estimates of recent Plasmodium falciparum exposure for individuals and communities

Significance Widely available accurate estimates of malaria exposure are essential for targeting and evaluation of public health interventions. Antibody responses to the malaria parasite can provide information on past exposure, but to date, most such measurements have been based on responses to a small number of parasite proteins chosen by convenience rather than utility and have not provided quantitative information on an individual’s exposure. Our results generated by screening hundreds of responses in children with known exposure histories indicate that responses to a few appropriately selected antigens can provide such information. This new approach can be transformed into high-throughput, low-cost, field-based assays useful for surveillance of malaria and has the potential to be translated into similar tools for other infectious diseases. Tools to reliably measure Plasmodium falciparum (Pf) exposure in individuals and communities are needed to guide and evaluate malaria control interventions. Serologic assays can potentially produce precise exposure estimates at low cost; however, current approaches based on responses to a few characterized antigens are not designed to estimate exposure in individuals. Pf-specific antibody responses differ by antigen, suggesting that selection of antigens with defined kinetic profiles will improve estimates of Pf exposure. To identify novel serologic biomarkers of malaria exposure, we evaluated responses to 856 Pf antigens by protein microarray in 186 Ugandan children, for whom detailed Pf exposure data were available. Using data-adaptive statistical methods, we identified combinations of antibody responses that maximized information on an individual’s recent exposure. Responses to three novel Pf antigens accurately classified whether an individual had been infected within the last 30, 90, or 365 d (cross-validated area under the curve = 0.86–0.93), whereas responses to six antigens accurately estimated an individual’s malaria incidence in the prior year. Cross-validated incidence predictions for individuals in different communities provided accurate stratification of exposure between populations and suggest that precise estimates of community exposure can be obtained from sampling a small subset of that community. In addition, serologic incidence predictions from cross-sectional samples characterized heterogeneity within a community similarly to 1 y of continuous passive surveillance. Development of simple ELISA-based assays derived from the successful selection strategy outlined here offers the potential to generate rich epidemiologic surveillance data that will be widely accessible to malaria control programs.

Comparative Impacts Over 5 Years of Artemisinin-Based Combination Therapies on Plasmodium falciparum Polymorphisms That Modulate Drug Sensitivity in Ugandan Children

BACKGROUND Artemisinin-based combination therapies, including artemether-lumefantrine (AL) and dihydroartemisinin-piperaquine (DP), are recommended to treat uncomplicated falciparum malaria. Sensitivities to components of AL and DP are impacted by polymorphisms in pfmdr1 and pfcrt. We monitored changes in prevalences of polymorphisms in Tororo, Uganda, from 2008 to 2012. METHODS Polymorphic loci in pfmdr1 and pfcrt were characterized in samples from 312 children randomized to AL or DP for each episode of uncomplicated malaria (50 samples per arm for each 3-month interval) utilizing a fluorescent microsphere assay. Treatment outcomes and impacts of prior therapies were also characterized. RESULTS Prevalence increased significantly over time for pfmdr1 N86 (AL: odds ratio [OR], 2.08 [95% confidence interval {CI}, 1.83-2.38]; DP: 1.41 [95% CI, 1.25-1.57]), pfmdr1 D1246 (AL: 1.46 [95% CI, 1.29-1.64]; DP: 1.36 [95% CI, 1.23-1.50]), and pfcrt K76 (AL: 3.37 [95% CI, 1.85-6.16]; DP: 5.84 [95% CI, 1.94-17.53], and decreased for pfmdr1 Y184 (AL: 0.78 [95% CI, .70-.86]; DP: 0.84 [95% CI, .76-1.50]); changes were consistently greater in the AL arm. Recent AL treatment selected for pfmdr1 N86, D1246, and 184F in subsequent episodes; DP selected for the opposite alleles. CONCLUSIONS Genotypes with decreased sensitivity to AL components increased over time. This increase was greater in children receiving AL, suggesting that the choice of treatment regimen can profoundly influence parasite genetics and drug sensitivity. CLINICAL TRIALS REGISTRATION NCT00527800.

Mind the Gap: House Structure and the Risk of Malaria in Uganda

Background Good house construction may reduce the risk of malaria by limiting the entry of mosquito vectors. We assessed how house design may affect mosquito house entry and malaria risk in Uganda. Methods 100 households were enrolled in each of three sub-counties: Walukuba, Jinja district; Kihihi, Kanungu district; and Nagongera, Tororo district. CDC light trap collections of mosquitoes were done monthly in all homes. All children aged six months to ten years (n = 878) were followed prospectively for a total of 24 months to measure parasite prevalence every three months and malaria incidence. Homes were classified as modern (cement, wood or metal walls; and tiled or metal roof; and closed eaves) or traditional (all other homes). Results A total of 113,618 female Anopheles were collected over 6,765 nights. 6,816 routine blood smears were taken of which 1,061 (15.6%) were malaria parasite positive. 2,582 episodes of uncomplicated malaria were diagnosed after 1,569 person years of follow-up, giving an overall incidence of 1.6 episodes per person year at risk. The human biting rate was lower in modern homes than in traditional homes (adjusted incidence rate ratio (IRR) 0.48, 95% confidence interval (CI) 0.37–0.64, p<0.001). The odds of malaria infection were lower in modern homes across all the sub-counties (adjusted odds ratio 0.44, 95%CI 0.30–0.65, p<0.001), while malaria incidence was lower in modern homes in Kihihi (adjusted IRR 0.61, 95%CI 0.40–0.91, p = 0.02) but not in Walukuba or Nagongera. Conclusions House design is likely to explain some of the heterogeneity of malaria transmission in Uganda and represents a promising target for future interventions, even in highly endemic areas.

Loss and dysfunction of Vδ2+ γδ T cells are associated with clinical tolerance to malaria

Loss and dysfunction of γδ T cells is associated with tolerance to P. falciparum infection. Tolerating Malaria Individuals living in malaria-endemic regions may develop “clinical immunity”—they still get infected with the parasite, but don’t show signs of infection. Jagannathan et al. now report one possible explanation for this malarial tolerance. They found that a subset of innate-like lymphocytes—γδ T cells—are lost in patients with repeated malaria exposure. What’s more, the γδ T cells that remain behave differently than the proinflammatory cells in people without prior malaria infection; they produce lower amounts of cytokines and express immunoregulatory genes. Therefore, although the patients may be asymptomatic, they likely do not effectively clear the infection and could serve as reservoirs for propagating disease. Although clinical immunity to malaria eventually develops among children living in endemic settings, the underlying immunologic mechanisms are not known. The Vδ2+ subset of γδ T cells have intrinsic reactivity to malaria antigens, can mediate killing of Plasmodium falciparum merozoites, and expand markedly in vivo after malaria infection in previously naïve hosts, but their role in mediating immunity in children repeatedly exposed to malaria is unclear. We evaluated γδ T cell responses to malaria among 4-year-old children enrolled in a longitudinal study in Uganda. We found that repeated malaria was associated with reduced percentages of Vδ2+ γδ T cells in peripheral blood, decreased proliferation and cytokine production in response to malaria antigens, and increased expression of immunoregulatory genes. Further, loss and dysfunction of proinflammatory Vδ2+ γδ T cells were associated with a reduced likelihood of symptoms upon subsequent P. falciparum infection. Together, these results suggest that repeated malaria infection during childhood results in progressive loss and dysfunction of Vδ2+ γδ T cells that may facilitate immunological tolerance of the parasite.

The association between malnutrition and the incidence of malaria among young HIV-infected and -uninfected Ugandan children: a prospective study.

BackgroundIn sub-Saharan Africa, malnutrition and malaria remain major causes of morbidity and mortality in young children. There are conflicting data as to whether malnutrition is associated with an increased or decreased risk of malaria. In addition, data are limited on the potential interaction between HIV infection and the association between malnutrition and the risk of malaria.MethodsA cohort of 100 HIV-unexposed, 203 HIV-exposed (HIV negative children born to HIV-infected mothers) and 48 HIV-infected children aged 6 weeks to 1 year were recruited from an area of high malaria transmission intensity in rural Uganda and followed until the age of 2.5 years. All children were provided with insecticide-treated bed nets at enrolment and daily trimethoprim-sulphamethoxazole prophylaxis (TS) was prescribed for HIV-exposed breastfeeding and HIV-infected children. Monthly routine assessments, including measurement of height and weight, were conducted at the study clinic. Nutritional outcomes including stunting (low height-for-age) and underweight (low weight-for-age), classified as mild (mean z-scores between -1 and -2 during follow-up) and moderate-severe (mean z-scores < -2 during follow-up) were considered. Malaria was diagnosed when a child presented with fever and a positive blood smear. The incidence of malaria was compared using negative binomial regression controlling for potential confounders with measures of association expressed as an incidence rate ratio (IRR).ResultsThe overall incidence of malaria was 3.64 cases per person year. Mild stunting (IRR = 1.24, 95% CI 1.06-1.46, p = 0.008) and moderate-severe stunting (IRR = 1.24, 95% CI 1.03-1.48, p = 0.02) were associated with a similarly increased incidence of malaria compared to non-stunted children. Being mildly underweight (IRR = 1.09, 95% CI 0.95-1.25, p = 0.24) and moderate-severe underweight (IRR = 1.12, 95% CI 0.86-1.46, p = 0.39) were not associated with a significant difference in the incidence of malaria compared to children who were not underweight. There were no significant interactions between HIV-infected, HIV-exposed children taking TS and the associations between malnutrition and the incidence of malaria.ConclusionsStunting, indicative of chronic malnutrition, was associated with an increased incidence of malaria among a cohort of HIV-infected and -uninfected young children living in an area of high malaria transmission intensity. However, caution should be made when making causal inferences given the observational study design and inability to disentangle the temporal relationship between malnutrition and the incidence of malaria.Trial RegistrationClinicalTrials.gov: NCT00527800.