Association of a novel mutation in the plasmodium falciparum chloroquine resistance transporter with decreased piperaquine sensitivity

Background. Amplified copy number in the plasmepsin II/III genes within Plasmodium falciparum has been associated with decreased sensitivity to piperaquine. To examine this association and test whether additional loci might also contribute, we performed a genome-wide association study of ex vivo P. falciparum susceptibility to piperaquine. Methods. Plasmodium falciparum DNA from 183 samples collected primarily from Cambodia was genotyped at 33 716 genomewide single nucleotide polymorphisms (SNPs). Linear mixed models and random forests were used to estimate associations between parasite genotypes and piperaquine susceptibility. Candidate polymorphisms were evaluated for their association with dihydroartemisinin- piperaquine treatment outcomes in an independent dataset. Results. Single nucleotide polymorphisms on multiple chromosomes were associated with piperaquine 90% inhibitory concentrations (IC90) in a genome-wide analysis. Fine-mapping of genomic regions implicated in genome-wide analyses identified multiple SNPs in linkage disequilibrium with each other that were significantly associated with piperaquine IC90, including a novel mutation within the gene encoding the P. falciparum chloroquine resistance transporter, PfCRT. This mutation (F145I) was associated with dihydroartemisinin-piperaquine treatment failure after adjusting for the presence of amplified plasmepsin II/III, which was also associated with decreased piperaquine sensitivity. Conclusions. Our data suggest that, in addition to plasmepsin II/III copy number, other loci, including pfcrt, may also be involved in piperaquine resistance

Observational cohort study of HIV-infected African children.

Item does not contain fulltextBACKGROUND: Most information about children living with HIV is based on follow up from children identified through mother-to-child transmission studies. Children identified through voluntary counseling and testing (VCT) represent a unique cohort that has not been previously described in the literature. METHODS: Children who were found to have HIV infection through VCT were offered enrollment in this study. They were evaluated monthly and encouraged to return to the clinic any time they were ill. Thorough evaluation was performed for every illness. RESULTS: Forty-five children were enrolled in the study. Many of the participants (33%) had a serious acute disease at the time of enrollment. The most common diagnoses were symptomatic malaria and pneumonia. The children were more ill than adults who were enrolled in a simultaneous study and had a higher death rate (37 versus 15 deaths per 100 person-years of observation). The mortality rate was 22%. Undernutrition and low CD4 cell count were independently associated with increased risk of death. CONCLUSIONS: Malawian children found to be HIV-infected through VCT had a high morbidity and mortality rate, highlighting the potential benefit of trimethoprim-sulfamethizole prophylaxis and available antiretroviral therapy

Impact of HIV-associated immunosuppression on malaria infection and disease in Malawi.

Item does not contain fulltextBACKGROUND: Human immunodeficiency virus (HIV) infection and malaria coexist in much of Africa. Previous studies differ in their findings on the interactions between the 2 infections. METHODS: Adults living with HIV infection in Blantyre, Malawi, were enrolled in a longitudinal observational study from September 2002 to August 2004. Malaria blood smears were obtained monthly and for any illness suggestive of malaria. Complete evaluations of all illness episodes were conducted, regardless of malaria smear results. RESULTS: The incidence of clinical malaria episodes was higher in participants with CD4 cell counts 500 cells/mm3. The trend was preserved when increasingly specific definitions of malaria disease were used. The prevalence of malaria infection was not associated with CD4 cell count. In per-visit analysis, lower CD4 cell counts were associated with higher incidences of pneumonia, sepsis, and tuberculosis but not of malaria. Severe malaria was rare, with only 3 cases in 591 person-years of observation. Parasite density and CD4 cell count were independent risk factors for fever. CONCLUSIONS: Profoundly immunosuppressed adults with HIV infection require more-frequent treatment for uncomplicated malaria, but malaria infection and disease are less strongly associated with HIV-associated immunosuppression than are other opportunistic infections. Where malaria is common, the high incidence of fever found among immunosuppressed adults may lead to misclassification of illness episodes as malaria

A community-based study of the incidence of trimethoprim-sulfamethoxazole-preventable infections in Malawian adults living with HIV.

Item does not contain fulltextThe benefits of trimethoprim-sulfamethoxazole (TS) prophylaxis reported for persons living with HIV in Cote d'Ivoire are difficult to extrapolate to sub-Saharan African countries where bacterial resistance to TS is higher and cross-resistance between TS and sulfadoxine-pyrimethamine (SP) may impair SP efficacy for malaria treatment. We conducted a community-based cohort study to measure the incidence of potentially TS-preventable illnesses in Blantyre, Malawi. We found a high incidence of malaria, invasive bacterial infections, and probable bacterial pneumonias but low rates of Pneumocystis jiroveci pneumonia, isosporiasis, and Toxoplasma encephalitis. Most bacterial isolates were resistant to TS but sensitive to azithromycin, a possible alternative to TS. Clinical trials are needed to determine the role of TS or alternative regimens for prophylaxis against secondary infections among people living with HIV in sub-Saharan Africa. These should also assess benefit in patients receiving antiretroviral therapy

A research agenda for malaria eradication: vaccines.

Contains fulltext : 97591.pdf (publisher's version ) (Open Access)Vaccines could be a crucial component of efforts to eradicate malaria. Current attempts to develop malaria vaccines are primarily focused on Plasmodium falciparum and are directed towards reducing morbidity and mortality. Continued support for these efforts is essential, but if malaria vaccines are to be used as part of a repertoire of tools for elimination or eradication of malaria, they will need to have an impact on malaria transmission. We introduce the concept of "vaccines that interrupt malaria transmission" (VIMT), which includes not only "classical" transmission-blocking vaccines that target the sexual and mosquito stages but also pre-erythrocytic and asexual stage vaccines that have an effect on transmission. VIMT may also include vaccines that target the vector to disrupt parasite development in the mosquito. Importantly, if eradication is to be achieved, malaria vaccine development efforts will need to target other malaria parasite species, especially Plasmodium vivax, where novel therapeutic vaccines against hypnozoites or preventive vaccines with effect against multiple stages could have enormous impact. A target product profile (TPP) for VIMT is proposed and a research agenda to address current knowledge gaps and develop tools necessary for design and development of VIMT is presented

Genome-wide and fine-resolution association analysis of malaria in West Africa

We report a genome-wide association (GWA) study of severe malaria in The Gambia. The initial GWA scan included 2,500 children genotyped on the Affymetrix 500K GeneChip, and a replication study included 3,400 children. We used this to examine the performance of GWA methods in Africa. We found considerable population stratification, and also that signals of association at known malaria resistance loci were greatly attenuated owing to weak linkage disequilibrium (LD). To investigate possible solutions to the problem of low LD, we focused on the HbS locus, sequencing this region of the genome in 62 Gambian individuals and then using these data to conduct multipoint imputation in the GWA samples. This increased the signal of association, from P = 4 × 10(-7) to P = 4 × 10(-14), with the peak of the signal located precisely at the HbS causal variant. Our findings provide proof of principle that fine-resolution multipoint imputation, based on population-specific sequencing data, can substantially boost authentic GWA signals and enable fine mapping of causal variants in African populations