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Newly arrived refugees offer insights into malaria epidemiology in their countries of origin. We evaluated asymptomatic refugee children within 7 days of arrival in Uganda from South Sudan and the Democratic Republic of Congo (DRC) in 2022 for parasitemia, parasite species, and Plasmodium falciparum drug resistance markers. Asymptomatic P. falciparum infections were common in both populations. Coinfection with P. malariae was more common in DRC refugees. Prevalences of markers of aminoquinoline resistance (PfCRT K76T, PfMDR1 N86Y) were much higher in South Sudan refugees, of antifolate resistance (PfDHFR C59R and I164L, PfDHPS A437G, K540E, and A581G) much higher in DRC refugees, and of artemisinin partial resistance (ART-R; PfK13 C469Y and A675V) moderate in both populations. Prevalences of most mutations differed from those seen in Ugandans attending health centers near the refugee centers. Refugee evaluations yielded insights into varied malaria epidemiology and identified markers of ART-R in 2 previously little-studied countries.
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Antimaláricos , Resistencia a Medicamentos , Malaria Falciparum , Plasmodium falciparum , Proteínas Protozoarias , Refugiados , Humanos , Uganda/epidemiología , Antimaláricos/uso terapéutico , Antimaláricos/farmacología , Resistencia a Medicamentos/genética , Prevalencia , Preescolar , Plasmodium falciparum/efectos de los fármacos , Plasmodium falciparum/genética , Malaria Falciparum/epidemiología , Malaria Falciparum/parasitología , Malaria Falciparum/tratamiento farmacológico , Femenino , Masculino , Niño , Proteínas Protozoarias/genética , Lactante , Proteínas de Transporte de Membrana/genética , Proteínas Asociadas a Resistencia a Múltiples Medicamentos/genética , Sudán/epidemiología , Biomarcadores/sangre , Artemisininas/uso terapéutico , Artemisininas/farmacología , Parasitemia/epidemiología , Parasitemia/tratamiento farmacológico , Plasmodium malariae/genética , Plasmodium malariae/efectos de los fármacosRESUMEN
Equity in access to genomic technologies, resources, and products remains a great challenge. This was evident especially during the coronavirus disease 2019 (COVID-19) pandemic when the majority of lower middle-income countries were unable to achieve at least 10% population vaccination coverage during initial COVID-19 vaccine rollouts, despite the rapid development of those vaccines. Sickle cell disease (SCD) is an inherited monogenic red blood cell disorder that affects hemoglobin, the protein that carries oxygen through the body. Globally, the African continent carries the highest burden of SCD with at least 240,000 children born each year with the disease. SCD has evolved from a treatable to a curable disease. Recently, the UK medical regulator approved its cure through clustered regularly interspaced short palindromic repeat (CRISPR)-based treatment, whereas the US Food and Drug Administration has equally approved two SCD gene therapies. This presents a remarkable opportunity to demonstrate equity in public health genomics. This CRISPR-based treatment is expensive and therefore, a need for an ambitious action to ensure that they are affordable and accessible where they are needed most and stand to save millions of lives.
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In modern medicine, vaccination is one of the most effective public health strategies to prevent infectious diseases. Indisputably, vaccines have saved millions of lives by reducing the burden of many serious infections such as polio, tuberculosis, measles, pneumonia, and tetanus. Despite the recent recommendation by the World Health Organization (WHO) to roll out RTS,S/AS01, this malaria vaccine still faces major challenges of variability in its efficacy partly due to high genetic variation in humans and malaria parasites. Immune responses to malaria vary between individuals and populations. Human genetic variation in immune system genes is the probable cause for this heterogeneity. In this review, we will focus on human genetic factors that determine variable responses to vaccination and how variation in immune system genes affect the immunogenicity and efficacy of the RTS,S/AS01 vaccine.
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Vacunas contra la Malaria , Malaria Falciparum , Malaria , Humanos , Lactante , África , Variación GenéticaRESUMEN
BACKGROUND: Anti-malarial drug resistance may be limited by decreased fitness in resistant parasites. Important contributors to resistance are mutations in the Plasmodium falciparum putative drug transporter PfMDR1. METHODS: Impacts on in vitro fitness of two common PfMDR1 polymorphisms, N86Y, which is associated with sensitivity to multiple drugs, and Y184F, which has no clear impact on drug sensitivity, were evaluated to study associations between resistance mediators and parasite fitness, measured as relative growth in competitive culture experiments. NF10 P. falciparum lines engineered to represent all PfMDR1 N86Y and Y184F haplotypes were co-cultured for 40 days, and the genetic make-up of the cultures was characterized every 4 days by pyrosequencing. The impacts of culture with anti-malarials on the growth of different haplotypes were also assessed. Lastly, the engineering of P. falciparum containing another common polymorphism, PfMDR1 D1246Y, was attempted. RESULTS: Co-culture results were as follows. With wild type (WT) Y184 fixed (N86/Y184 vs. 86Y/Y184), parasites WT and mutant at 86 were at equilibrium. With mutant 184 F fixed (N86/184F vs. 86Y/184F), mutants at 86 overgrew WT. With WT N86 fixed (N86/Y184 vs. N86/184F), WT at 184 overgrew mutants. With mutant 86Y fixed (86Y/Y184 vs. 86Y/184F), WT and mutant at 86 were at equilibrium. Parasites with the double WT were in equilibrium with the double mutant, but 86Y/Y184 overgrew N86/184F. Overall, WT N86/mutant 184F parasites were less fit than parasites with all other haplotypes. Parasites engineered for another mutation, PfMDR1 1246Y, were unstable in culture, with reversion to WT over time. Thus, the N86 WT is stable when accompanied by the Y184 WT, but incurs a fitness cost when accompanied by mutant 184F. Culturing in the presence of chloroquine favored 86Y mutant parasites and in the presence of lumefantrine favored N86 WT parasites; piperaquine had minimal impact. CONCLUSIONS: These results are consistent with those for Ugandan field isolates, suggest reasons for varied haplotypes, and highlight the interplay between drug pressure and fitness that is guiding the evolution of resistance-mediating haplotypes in P. falciparum.
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Antimaláricos/farmacología , Aptitud Genética , Proteínas Asociadas a Resistencia a Múltiples Medicamentos/genética , Mutación , Plasmodium falciparum/genética , Cloroquina/farmacología , Haplotipos , Lumefantrina/farmacología , Proteínas Asociadas a Resistencia a Múltiples Medicamentos/metabolismo , Plasmodium falciparum/efectos de los fármacos , Quinolinas/farmacologíaRESUMEN
BACKGROUND: Malaria is one of the most serious infectious diseases in the world. The malaria burden is greatly affected by human immunity, and immune responses vary between populations. Genetic diversity in KIR and HLA-C genes, which are important in immunity to infectious diseases, is likely to play a role in this heterogeneity. Several studies have shown that KIR and HLA-C genes influence the immune response to viral infections, but few studies have examined the role of KIR and HLA-C in malaria infection, and these have used low-resolution genotyping. The aim of this study was to determine whether genetic variation in KIR and their HLA-C ligands differ in Ugandan populations with historically varied malaria transmission intensity using more comprehensive genotyping approaches. METHODS: High throughput multiplex quantitative real-time PCR method was used to genotype KIR genetic variants and copy number variation and a high-throughput real-time PCR method was developed to genotype HLA-C1 and C2 allotypes for 1344 participants, aged 6 months to 10 years, enrolled from Ugandan populations with historically high (Tororo District), medium (Jinja District) and low (Kanungu District) malaria transmission intensity. RESULTS: The prevalence of KIR3DS1, KIR2DL5, KIR2DS5, and KIR2DS1 genes was significantly lower in populations from Kanungu compared to Tororo (7.6 vs 13.2%: p = 0.006, 57.2 vs 66.4%: p = 0.005, 33.2 vs 46.6%: p < 0.001, and 19.7 vs 26.7%: p = 0.014, respectively) or Jinja (7.6 vs 18.1%: p < 0.001, 57.2 vs 63.8%: p = 0.048, 33.2 vs 43.5%: p = 0.002, and 19.7 vs 30.4%: p < 0.001, respectively). The prevalence of homozygous HLA-C2 was significantly higher in populations from Kanungu (31.6%) compared to Jinja (21.4%), p = 0.043, with no significant difference between Kanungu and Tororo (26.7%), p = 0.296. CONCLUSIONS: The KIR3DS1, KIR2DL5, KIR2DS5 and KIR2DS1 genes may partly explain differences in transmission intensity of malaria since these genes have been positively selected for in places with historically high malaria transmission intensity. The high-throughput, multiplex, real-time HLA-C genotyping PCR method developed will be useful in disease-association studies involving large cohorts.
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Variaciones en el Número de Copia de ADN , Genotipo , Antígenos HLA-C/genética , Canales de Potasio de Rectificación Interna/genética , Niño , Preescolar , Antígenos HLA-C/metabolismo , Humanos , Lactante , Ligandos , Malaria Falciparum/transmisión , Canales de Potasio de Rectificación Interna/metabolismo , UgandaRESUMEN
Mutations that mediate resistance of Plasmodium falciparum to aminoquinoline antimalarials are selected by prior drug use and may alter parasite fitness, but associations with clinical presentations are uncertain. We evaluated genotypes in samples from a case-control study of determinants of severe malaria in Ugandan children 4 months to 10 years of age. We studied 274 cases with severe malaria matched by age and geography to 275 uncomplicated malaria controls and 179 asymptomatic parasitemic controls. The overall prevalence of mutations of interest (considering mixed results as mutant) was 67.0% for PfCRT K76T, 8.5% for PfMDR1 N86Y, 71.5% for PfMDR1 Y184F, and 14.7% for PfMDR1 D1246Y. Compared to asymptomatic controls, the odds of mutant PfCRT 76T were lower for uncomplicated (odds ratio, 0.42 [95% confidence interval, 0.24 to 0.72]; P < 0.001) or severe (0.56 [0.32 to 0.97]; P = 0.031) malaria; the odds of mutant PfMDR1 86Y were lower for uncomplicated (0.33 [0.16 to 0.65]; P < 0.001) or severe (0.21 [0.09 to 0.45]; P < 0.001) malaria; and the odds of mutant PfMDR1 1246Y were higher for uncomplicated (1.83 [0.90 to 3.98]; P = 0.076) or severe (2.06 [1.01 to 4.55]; P = 0.033) malaria. The odds of mutant PfMDR1 184F were lower in severe than asymptomatic (0.59 [0.37 to 0.92]; P = 0.016) or uncomplicated (0.61 [0.41 to 0.90]; P = 0.009) malaria. Overall, the PfCRT 76T and PfMDR1 86Y mutations were associated with decreased risk of symptomatic malaria, PfMDR1 1246Y was associated with increased risk of symptomatic malaria, and PfMDR1 184F was associated with decreased risk of severe malaria. These results offer insights into parasite genotypes in children with different presentations, although the basis for the identified associations is likely complex.
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Antimaláricos , Resistencia a Medicamentos , Malaria Falciparum , Aminoquinolinas/uso terapéutico , Antimaláricos/uso terapéutico , Estudios de Casos y Controles , Niño , Preescolar , Genotipo , Humanos , Lactante , Malaria Falciparum/tratamiento farmacológico , Proteínas Asociadas a Resistencia a Múltiples Medicamentos/genética , Plasmodium falciparum/genética , Proteínas Protozoarias/genética , UgandaRESUMEN
In sub-Saharan Africans, maternal mortality is unacceptably high, with >400 deaths per 100,000 births compared with <10 deaths per 100,000 births in Europeans. One-third of the deaths are caused by pre-eclampsia, a syndrome arising from defective placentation. Controlling placentation are maternal natural killer (NK) cells that use killer-cell immunoglobulin-like receptor (KIR) to recognize the fetal HLA-C molecules on invading trophoblast. We analyzed genetic polymorphisms of maternal KIR and fetal HLA-C in 484 normal and 254 pre-eclamptic pregnancies at Mulago Hospital, Kampala, Uganda. The combination of maternal KIR AA genotypes and fetal HLA-C alleles encoding the C2 epitope associates with pre-eclampsia [P = 0.0318, odds ratio (OR) = 1.49]. The KIR genes associated with protection are located in centromeric KIR B regions that are unique to sub-Saharan African populations and contain the KIR2DS5 and KIR2DL1 genes (P = 0.0095, OR = 0.59). By contrast, telomeric KIR B genes protect Europeans against pre-eclampsia. Thus, different KIR B regions protect sub-Saharan Africans and Europeans from pre-eclampsia, whereas in both populations, the KIR AA genotype is a risk factor for the syndrome. These results emphasize the importance of undertaking genetic studies of pregnancy disorders in African populations with the potential to provide biological insights not available from studies restricted to European populations.
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Población Negra/genética , Centrómero , Preeclampsia/prevención & control , Receptores KIR/genética , Población Blanca/genética , Femenino , Humanos , Preeclampsia/genética , EmbarazoRESUMEN
Background: In a recent trial of intermittent preventive treatment in pregnancy (IPTp) in Uganda, dihydroartemisinin-piperaquine (DP) was superior to sulfadoxine-pyrimethamine (SP) in preventing maternal and placental malaria. Methods: We compared genotypes using sequencing, fluorescent microsphere, and quantitative polymerase chain reaction assays at loci associated with drug resistance in Plasmodium falciparum isolated from subjects receiving DP or SP. Results: Considering aminoquinoline resistance, DP was associated with increased prevalences of mutations at pfmdr1 N86Y, pfmdr1 Y184F, and pfcrt K76T compared to SP (64.6% vs 27.4%, P < .001; 93.9% vs 59.2%, P < .001; and 87.7% vs 75.4%, P = .03, respectively). Increasing plasma piperaquine concentration at the time of parasitemia was associated with increasing pfmdr1 86Y prevalence; no infections with the N86 genotype occurred with piperaquine >2.75 ng/mL. pfkelch13 propeller domain polymorphisms previously associated with artemisinin resistance were not identified. Recently identified markers of piperaquine resistance were uncommon and not associated with DP. Considering antifolate resistance, SP was associated with increased prevalence of a 5-mutation haplotype (pfdhfr 51I, 59R, and 108N; pfdhps 437G and 581G) compared to DP (90.8% vs 60.0%, P = .001). Conclusions: IPTp selected for genotypes associated with decreased sensitivity to treatment regimens, but genotypes associated with clinically relevant DP resistance in Asia have not emerged in Uganda.
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Antimaláricos/uso terapéutico , Resistencia a Medicamentos , Malaria Falciparum/tratamiento farmacológico , Plasmodium falciparum/genética , Polimorfismo Genético/genética , Artemisininas/uso terapéutico , Combinación de Medicamentos , Femenino , Humanos , Malaria Falciparum/parasitología , Plasmodium falciparum/efectos de los fármacos , Embarazo , Pirimetamina/uso terapéutico , Quinolinas , Sulfadoxina/uso terapéuticoRESUMEN
We assessed Plasmodium falciparum drug resistance markers in parasites collected in 2012, 2013, and 2015 at 3 sites in Uganda. The prevalence and frequency of parasites with mutations in putative transporters previously associated with resistance to aminoquinolines, but increased sensitivity to lumefantrine (pfcrt 76T; pfmdr1 86Y and 1246Y), decreased markedly at all sites. Antifolate resistance mutations were common, with apparent emergence of mutations (pfdhfr 164L; pfdhps 581G) associated with high-level resistance. K13 mutations linked to artemisinin resistance were uncommon and did not increase over time. Changing malaria treatment practices have been accompanied by profound changes in markers of resistance.
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Antimaláricos/farmacología , Resistencia a Medicamentos/genética , Genes Protozoarios , Plasmodium falciparum/efectos de los fármacos , Adolescente , Aminoquinolinas/farmacología , Artemisininas/farmacología , Estudios Transversales , ADN Protozoario/aislamiento & purificación , Etanolaminas/farmacología , Femenino , Fluorenos/farmacología , Antagonistas del Ácido Fólico/farmacología , Humanos , Lumefantrina , Malaria Falciparum/tratamiento farmacológico , Proteínas de Transporte de Membrana/genética , Proteínas de Transporte de Membrana/metabolismo , Proteínas Asociadas a Resistencia a Múltiples Medicamentos/genética , Proteínas Asociadas a Resistencia a Múltiples Medicamentos/metabolismo , Mutación , Plasmodium falciparum/genética , Polimorfismo de Nucleótido Simple , Proteínas Protozoarias/genética , Proteínas Protozoarias/metabolismo , Análisis de Secuencia de ADN , UgandaRESUMEN
BACKGROUND: Plasmodium falciparum genetic polymorphisms that mediate altered drug sensitivity may impact upon virulence. In a cross-sectional study, Ugandan children with infections mutant at pfcrt K76T, pfmdr1 N86Y, or pfmdr1 D1246Y had about one-fourth the odds of symptomatic malaria compared to those with infections with wild type (WT) sequences. However, results may have been confounded by greater likelihood in those with symptomatic disease of higher density mixed infections and/or recent prior treatment that selected for WT alleles. METHODS: Polymorphisms in samples from paired episodes of asymptomatic and symptomatic parasitaemia in 114 subjects aged 4-11 years were followed longitudinally in Tororo District, Uganda. Paired episodes occurred within 3-12 months of each other and had no treatment for malaria in the prior 60 days. The prevalence of WT, mixed, and mutant alleles was determined using multiplex ligase detection reaction-fluorescent microsphere assays. RESULTS: Considering paired episodes in the same subject, the odds of symptomatic malaria were lower for infections with mutant compared to WT or mixed sequence at N86Y (OR 0.26, 95% CI 0.09-0.79, p = 0.018), but not K76T or D1246Y. However, symptomatic episodes (which had higher densities) were more likely than asymptomatic to be mixed (for N86Y OR 2.0, 95% CI 1.04-4.0, p = 0.036). Excluding mixed infections, the odds of symptomatic malaria were lower for infections with mutant compared to WT sequence at N86Y (OR 0.33, 95% CI 0.11-0.98, p = 0.046), but not the other alleles. However, if mixed genotypes were grouped with mutants in this analysis or assuming that mixed infections consisted of 50% WT and 50% mutant genotypes, the odds of symptomatic infection did not differ between infections that were mutant or WT at the studied alleles. CONCLUSIONS: Although infections with only the mutant pfmdr1 86Y genotype were associated with symptomatic infection, this association could primarily be explained by greater parasite densities and therefore greater prevalence of mixed infections in symptomatic children. These results indicate limited association between the tested polymorphisms and risk of symptomatic disease and highlight the value of longitudinal studies for assessing associations between parasite factors and clinical outcomes.
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Enfermedades Asintomáticas , Resistencia a Medicamentos , Malaria Falciparum/patología , Parasitemia/patología , Plasmodium falciparum/clasificación , Plasmodium falciparum/efectos de los fármacos , Polimorfismo Genético , Adulto , Niño , Preescolar , Femenino , Frecuencia de los Genes , Genotipo , Humanos , Lactante , Estudios Longitudinales , Malaria Falciparum/parasitología , Masculino , Mutación Missense , Parasitemia/parasitología , Plasmodium falciparum/genética , Plasmodium falciparum/aislamiento & purificación , UgandaRESUMEN
Dihydroartemisinin-piperaquine (DP) offers prolonged protection against malaria, but its impact on Plasmodium falciparum drug sensitivity is uncertain. In a trial of intermittent preventive treatment in schoolchildren in Tororo, Uganda, in 2011 to 2012, monthly DP for 1 year decreased the incidence of malaria by 96% compared to placebo; DP once per school term offered protection primarily during the first month after therapy. To assess the impact of DP on selection of drug resistance, we compared the prevalence of key polymorphisms in isolates that emerged at different intervals after treatment with DP. Blood obtained monthly and at each episode of fever was assessed for P. falciparum parasitemia by microscopy. Samples from 160 symptomatic and 650 asymptomatic episodes of parasitemia were assessed at 4 loci (N86Y, Y184F, and D1246Y in pfmdr1 and K76T in pfcrt) that modulate sensitivity to aminoquinoline antimalarials, utilizing a ligase detection reaction-fluorescent microsphere assay. For pfmdr1 N86Y and pfcrt K76T, but not the other studied polymorphisms, the prevalences of mutant genotypes were significantly greater in children who had received DP within the past 30 days than in those not treated within 60 days (86Y, 18.0% versus 8.3% [P = 0.03]; 76T, 96.0% versus 86.1% [P = 0.05]), suggesting selective pressure of DP. Full sequencing of pfcrt in a subset of samples did not identify additional polymorphisms selected by DP. In summary, parasites that emerged soon after treatment with DP were more likely than parasites not under drug pressure to harbor pfmdr1 and pfcrt polymorphisms associated with decreased sensitivity to aminoquinoline antimalarials. (This study has been registered at ClinicalTrials.gov under no. NCT01231880.).
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Artemisininas/farmacología , Malaria Falciparum/tratamiento farmacológico , Plasmodium falciparum/efectos de los fármacos , Polimorfismo Genético , Quinolinas/farmacología , Adolescente , Antimaláricos/farmacología , Niño , Femenino , Humanos , Malaria Falciparum/parasitología , Masculino , Proteínas de Transporte de Membrana/genética , Proteínas Asociadas a Resistencia a Múltiples Medicamentos/genética , Plasmodium falciparum/genética , Profilaxis Pre-Exposición , Proteínas Protozoarias/genética , UgandaRESUMEN
BACKGROUND: Malaria remains a public health challenge in sub-Saharan Africa with Plasmodium falciparum being the principal cause of malaria disease morbidity and mortality. Plasmodium falciparum virulence is attributed, in part, to its population-level genetic diversity-a characteristic that has yet to be studied in Rwanda. Characterizing P. falciparum molecular epidemiology in an area is needed for a better understand of malaria transmission and to inform choice of malaria control strategies. METHODS: In this health-facility based survey, malaria case clinical profiles and parasite densities as well as parasite genetic diversity were compared among P. falciparum-infected patients identified at two sites of different malaria transmission intensities in Rwanda. Data on demographics and clinical features and finger-prick blood samples for microscopy and parasite genotyping were collected(.) Nested PCR was used to genotype msp-2 alleles of FC27 and 3D7. RESULTS: Patients' variables of age group, sex, fever (both by patient report and by measured tympanic temperatures), parasite density, and bed net use were found differentially distributed between the higher endemic (Ruhuha) and lower endemic (Mubuga) sites. Overall multiplicity of P. falciparum infection (MOI) was 1.73 but with mean MOI found to vary significantly between 2.13 at Ruhuha and 1.29 at Mubuga (p < 0.0001). At Ruhuha, expected heterozygosity (EH) for FC27 and 3D7 alleles were 0.62 and 0.49, respectively, whilst at Mubuga, EH for FC27 and 3D7 were 0.26 and 0.28, respectively. CONCLUSIONS: In this study, a higher geometrical mean parasite counts, more polyclonal infections, higher MOI, and higher allelic frequency were observed at the higher malaria-endemic (Ruhuha) compared to the lower malaria-endemic (Mubuga) area. These differences in malaria risk and MOI should be considered when choosing setting-specific malaria control strategies, assessing p. falciparum associated parameters such as drug resistance, immunity and impact of used interventions, and in proper interpretation of malaria vaccine studies.
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Antígenos de Protozoos/genética , Variación Genética , Malaria Falciparum/epidemiología , Plasmodium falciparum/genética , Proteínas Protozoarias/genética , Adolescente , Adulto , Anciano , Niño , Preescolar , Estudios Transversales , Femenino , Frecuencia de los Genes , Humanos , Lactante , Malaria Falciparum/parasitología , Masculino , Persona de Mediana Edad , Reacción en Cadena de la Polimerasa , Rwanda/epidemiología , Análisis de Secuencia de ADN , Adulto JovenRESUMEN
We explored associations between Plasmodium falciparum drug resistance-mediating polymorphisms and clinical presentations in parasitemic children enrolled in a cross-sectional survey in Tororo, Uganda, using a retrospective case-control design. All 243 febrile children (cases) and 243 randomly selected asymptomatic children (controls) were included. In a multivariate analysis adjusting for age, complexity of infection, and parasite density, the prevalence of wild-type genotypes was significantly higher in febrile children compared to asymptomatic children (pfcrt K76T: odds ratio [OR] 4.41 [95% confidence interval {CI}, 1.28-15.1]; pfmdr1 N86Y: OR 4.08 [95% CI, 2.01-8.31], and pfmdr1 D1246Y: OR 4.90 [95% CI, 1.52-15.8]), suggesting greater virulence for wild-type parasites.
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Resistencia a Medicamentos , Malaria Falciparum/patología , Malaria Falciparum/parasitología , Plasmodium falciparum/efectos de los fármacos , Plasmodium falciparum/genética , Polimorfismo Genético , Adolescente , Estudios de Casos y Controles , Niño , Preescolar , Estudios Transversales , Femenino , Humanos , Lactante , Masculino , Proteínas de Transporte de Membrana/genética , Proteínas Asociadas a Resistencia a Múltiples Medicamentos/genética , Plasmodium falciparum/aislamiento & purificación , Plasmodium falciparum/patogenicidad , Proteínas Protozoarias/genética , Estudios Retrospectivos , Uganda , VirulenciaRESUMEN
BACKGROUND: Malaria remains a major public health problem, and its control has been hampered by drug resistance. For a number of drugs, Plasmodium falciparum single nucleotide polymorphisms (SNPs) are associated with altered drug sensitivity and can be used as markers of drug resistance. Several techniques have been studied to assess resistance markers. The most widely used methodology is restriction fragment length polymorphism (RFLP) analysis. The ligase detection reaction fluorescent microsphere (LDR-FM) assay was recently shown to provide high throughput assessment of P. falciparum SNPs associated with drug resistance. The aim of this study was to validate the reliability and accuracy of the LDR-FM assay in a field setting. METHODS: For 223 samples from a clinical trial in Tororo, Uganda in which P. falciparum was identified by blood smear, DNA was extracted from dried blood spots, genes of interest were amplified by PCR, amplicons were analysed by both RFLP and LDR-FM assays, and results were compared. RESULTS: SNP prevalence (wild type/mixed/mutant) with RFLP analysis was 8/5/87% for pfcrt K76T, 34/37/29% for pfmdr1 N86Y, 64/17/19% for pfmdr1 Y184F, and 42/21/37% for pfmdr1 D1246Y. These prevalences with the LDR-FM assay were 7/5/88%, 31/24/45%, 62/20/18%, and 48/19/33% for the four SNPs, respectively. Combining mixed and mutant outcomes for analysis, agreement between the assays was 97% (K=0.77) for pfcrt K76T, 79% (K=0.55) for pfmdr1 N86Y, 83% (K=0.65) for pfmdr1 Y184F, and 91% (K=0.82) for pfmdr1 D1246Y, with most disagreements due to discrepant readings of mixed genotypes. CONCLUSION: The LDR-FM assay provides a high throughput, relatively inexpensive and accurate assay for the surveillance of P. falciparum SNPs associated with drug resistance in resource-limited countries.
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Resistencia a Medicamentos , Técnicas de Diagnóstico Molecular/métodos , Pruebas de Sensibilidad Parasitaria/métodos , Plasmodium falciparum/genética , Polimorfismo de Nucleótido Simple , Preescolar , ADN Protozoario/genética , ADN Protozoario/aislamiento & purificación , Femenino , Ensayos Analíticos de Alto Rendimiento , Humanos , Lactante , Ligasas/metabolismo , Estudios Longitudinales , Malaria Falciparum/parasitología , Masculino , Microesferas , Plasmodium falciparum/efectos de los fármacos , Reacción en Cadena de la Polimerasa , UgandaRESUMEN
Background: Understanding COVID-19's impact on children is vital for public health policy, yet age-specific data is scarce, especially in Uganda. This study examines SARS-CoV-2 seroprevalence and risk factors among Ugandan children at two timepoints, along with COVID-19-related knowledge and practices in households, including adult vaccination status. Methods: Baseline surveys were conducted in 12 communities from April to May 2021 (post-Alpha wave) and follow-up surveys in 32 communities from November 2021 to March 2022 (Omicron wave). Household questionnaires and blood samples were collected to test for malaria by microscopy and for SARS-CoV-2 using a Luminex assay. Seroprevalence was estimated at both the survey and community level. Mixed-effects logistic regression models assessed the association between individual and household factors and SARS-CoV-2 seropositivity in children, adjusting for household clustering. Results: More households reported disruptions in daily life at baseline compared to follow-up, though economic impacts lingered. By the follow-up survey, 52.7% of adults had received at least one COVID-19 vaccine dose. Overall seroprevalence in children was higher at follow-up compared to baseline (71.6% versus 19.2%, p < 0.001). Seroprevalence in children ranged across communities from 6-37% at baseline and 50-90% at follow-up. At baseline, children from the poorest households were more likely to be infected. Increasing age remained the only consistent risk factor for SARS-CoV-2 seroconversion at both timepoints. Conclusions: Results indicate that a larger number of children were infected by the Delta and Omicron waves of COVID-19 compared to the Alpha wave. This study is the largest seroprevalence survey in children in Uganda, providing evidence that most children were infected with SARS-CoV-2 before the vaccine was widely available to pediatric populations. Pediatric infections were vastly underreported by case counts, highlighting the importance of seroprevalence surveys in assessing disease burden when testing and reporting rates are limited and many cases are mild or asymptomatic.
RESUMEN
Killer cell immunoglobulin-like receptor (KIR) genes are expressed by natural killer cells and encoded by a family of genes exhibiting considerable haplotypic and allelic variation. HLA-C molecules, the dominant ligands for KIR, are present in all individuals and are discriminated by two KIR epitopes, C1 and C2. We studied the frequencies of KIR genes and HLA-C1 and C2 groups in a large cohort (n = 492) from Kampala, Uganda, East Africa and compared our findings with published data from other populations in sub-Saharan Africa (SSA) and several European populations. We find considerably more KIR diversity and weaker linkage disequilibrium in SSA compared to the European populations and describe several novel KIR genotypes. C1 and C2 frequencies were similar to other SSA populations with a higher frequency of the C2 epitope (54.9 %) compared to Europe (average 39.7 %). Analysis of this large cohort from Uganda in the context of other African populations reveals variations in KIR and HLA-C1 and C2 that are consistent with migrations within Africa and potential selection pressures on these genes. Our results will help understand how KIR/HLA-C interactions contribute to resistance to pathogens and reproductive success.
Asunto(s)
Genética de Población , Antígenos HLA-C/genética , Haplotipos/genética , Receptores KIR/genética , África del Sur del Sahara/epidemiología , ADN de Neoplasias/genética , Genotipo , Humanos , Ligandos , Desequilibrio de Ligamiento , Reacción en Cadena de la Polimerasa , Polimorfismo Conformacional Retorcido-Simple , Uganda/epidemiología , Reino Unido/epidemiologíaRESUMEN
Natural killer (NK) cells likely play an important role in immunity to malaria, but the effect of repeated malaria on NK cell responses remains unclear. Here, we comprehensively profiled the NK cell response in a cohort of 264 Ugandan children. Repeated malaria exposure was associated with expansion of an atypical, CD56neg population of NK cells that differed transcriptionally, epigenetically, and phenotypically from CD56dim NK cells, including decreased expression of PLZF and the Fc receptor γ-chain, increased histone methylation, and increased protein expression of LAG-3, KIR, and LILRB1. CD56neg NK cells were highly functional and displayed greater antibody-dependent cellular cytotoxicity than CD56dim NK cells. Higher frequencies of CD56neg NK cells were associated with protection against symptomatic malaria and high parasite densities. After marked reductions in malaria transmission, frequencies of these cells rapidly declined, suggesting that continuous exposure to Plasmodium falciparum is required to maintain this modified, adaptive-like NK cell subset.
Asunto(s)
Células Asesinas Naturales , Malaria , Niño , Humanos , Antígeno CD56/metabolismo , Plasmodium falciparum , Receptores FcRESUMEN
Artemisinin resistance (AR) emerged in South East Asia 13 years ago and the identification of the resistance conferring molecular marker, Plasmodium falciparum Kelch 13 (Pfk13), 7 years ago has provided an invaluable tool for monitoring AR in malaria endemic countries. Molecular Pfk13 surveillance revealed the resistance foci in the Greater Mekong Subregion, an independent emergence in Guyana, South America, and a low frequency of mutations in Africa. The recent identification of the R561H Pfk13 AR associated mutation in Tanzania, Uganda and in Rwanda, where it has been associated with delayed parasite clearance, should be a concern for the continent. In this review, we provide a summary of Pfk13 resistance associated propeller domain mutation frequencies across Africa from 2012 to 2020, to examine how many other countries have identified these mutations. Only four African countries reported a recent identification of the M476I, P553L, R561H, P574L, C580Y and A675V Pfk13 mutations at low frequencies and with no reports of clinical treatment failure, except for Rwanda. These mutations present a threat to malaria control across the continent, since the greatest burden of malaria remains in Africa. A rise in the frequency of these mutations and their spread would reverse the gains made in the reduction of malaria over the last 20 years, given the lack of new antimalarial treatments in the event artemisinin-based combination therapies fail. The review highlights the frequency of Pfk13 propeller domain mutations across Africa, providing an up-to-date perspective of Pfk13 mutations, and appeals for an urgent and concerted effort to monitoring antimalarial resistance markers in Africa and the efficacy of antimalarials by re-establishing sentinel surveillance systems.
Asunto(s)
Antimaláricos , Artemisininas , Malaria Falciparum , África/epidemiología , Antimaláricos/farmacología , Antimaláricos/uso terapéutico , Artemisininas/farmacología , Artemisininas/uso terapéutico , Resistencia a Medicamentos/genética , Humanos , Malaria Falciparum/tratamiento farmacológico , Malaria Falciparum/epidemiología , Mutación , Plasmodium falciparum/genética , Proteínas Protozoarias/genéticaRESUMEN
Malaria is one of the deadliest infectious diseases in the world. Immune responses to Plasmodium falciparum malaria vary among individuals and between populations. Human genetic variation in immune system genes is likely to play a role in this heterogeneity. Natural killer (NK) cells produce inflammatory cytokines in response to malaria infection, kill intraerythrocytic Plasmodium falciparum parasites by cytolysis, and participate in the initiation and development of adaptive immune responses to plasmodial infection. These functions are modulated by interactions between killer-cell immunoglobulin-like receptors (KIRs) and human leukocyte antigens (HLAs). Therefore, variations in KIR and HLA genes can have a direct impact on NK cell functions. Understanding the role of KIRs and HLAs in immunity to malaria can help to better characterize antimalarial immune responses. In this review, we summarize the different KIRs and HLAs associated with immunity to malaria thus far.
Asunto(s)
Variación Genética , Antígenos HLA/genética , Inmunidad/genética , Malaria/genética , Malaria/inmunología , Haplotipos/genética , Humanos , Malaria/parasitología , Plasmodium falciparum/fisiologíaRESUMEN
BACKGROUND: Evidence for association between sickle cell and alpha thalassemia trait and severe malaria is compelling. However, for these polymorphisms associations with uncomplicated malaria, and for G6PD deficiency associations with uncomplicated and severe malaria, findings have been inconsistent. We studied samples from a three-arm case-control study with the objective of determining associations between common host erythrocyte polymorphisms and both uncomplicated and severe malaria, including different severe malaria phenotypes. METHOD: We assessed hemoglobin abnormalities, α-thalassemia, and G6PD deficiency by molecular methods in 325 children with severe malaria age-matched to 325 children with uncomplicated malaria and 325 healthy community controls. Conditional logistic regression was used to measure associations between specified genotypes and malaria outcomes. RESULTS: No tested polymorphisms offered significant protection against uncomplicated malaria. α-thalassemia homozygotes (_α/_α) had increased risk of uncomplicated malaria (OR 2.40; 95%CI 1.15, 5.03, p = 0.020). HbAS and α-thalassemia heterozygous (_α/αα) genotypes protected against severe malaria compared to uncomplicated malaria (HbAS OR 0.46; 0.23, 0.95, p = 0.036; _α/αα OR 0.51; 0.24, 0.77; p = 0.001) or community (HbAS OR 0.23; 0.11, 0.50; p<0.001; _α/αα; OR 0.49; 0.32, 0.76; p = 0.002) controls. The α-thalassemia homozygous (_α/_α) genotype protected against severe malaria when compared to uncomplicated malaria controls (OR 0.34; 95%CI 0.156, 0.73, p = 0.005), but not community controls (OR 1.03; 0.46, 2.27, p = 0.935). Stratifying by the severe malaria phenotype, compared to community controls, the protective effect of HbAS was limited to children with severe anemia (OR 0.17; 95%CI 0.04, 0.65; p = 0.009) and that of _α/αα to those with altered consciousness (OR 0.24; 0.09, 0.59; p = 0.002). A negative epistatic effect was seen between HbAS and _α/αα; protection compared to uncomplicated malaria controls was not seen in individuals with both polymorphisms (OR 0.45; 0.11, 1.84; p = 0.269). G6PD deficiency was not protective against severe malaria. CONCLUSION: Associations were complex, with HbAS principally protective against severe anemia, _α/αα against altered consciousness, and negative epistasis between the two polymorphisms.