RESUMEN
Genetic host factors play a substantial role in susceptibility to and severity of malaria, which continues to cause at least one million deaths per year. Recently, members of the toll-like receptor (TLR) family have been shown to be involved in recognition of the etiologic organism Plasmodium falciparum: The glycosylphosphatidylinisitol anchor induces signaling in host cells via TLR-2 and -4, while hemozoin-induced immune activation involves TLR-9. Binding of microbial ligands to the respective TLRs triggers the release of pro-inflammatory cytokines via the TLR/IL-1 receptor (TIR) domain and may contribute to the host response, including pro-inflammatory cytokine induction and malarial fever. In a case-control study among 870 Ghanaian children, we examined the influence of TLR-2, -4, and -9 polymorphisms in susceptibility to severe malaria. TLR-2 variants common in Caucasians and Asians were completely absent. However, we found a new, rare mutation (Leu658Pro), which impairs signaling via TLR-2. We failed to detect any polymorphisms within the TLR-9/interleukin-1 receptor domain. Two frequent TLR-9 promoter polymorphisms did not show a clear association with malaria severity. In contrast, the TLR-4-Asp299Gly variant occurred at a high rate of 17.6% in healthy controls, and was even more frequent in severe malaria patients (24.1%, p<0.05). Likewise, TLR-4-Thr399Ile was seen in 2.4% of healthy children and in 6.2% of patients (p=0.02). TLR-4-Asp299Gly and TLR-4-Thr399Ile conferred an 1.5- and 2.6-fold increased risk of severe malaria, respectively. These findings suggest TLR4-mediated responses to malaria in vivo and TLR-4 polymorphisms to be associated with disease manifestation. However some gray areas also suggest the scope for further improvements.
Asunto(s)
Inmunidad Innata/genética , Malaria Falciparum/inmunología , Polimorfismo de Nucleótido Simple/inmunología , Receptor Toll-Like 4/genética , Niño , Preescolar , Femenino , Predisposición Genética a la Enfermedad , Ghana , Humanos , Lactante , Malaria Falciparum/genética , Masculino , Receptor Toll-Like 2/genética , Receptor Toll-Like 2/inmunología , Receptor Toll-Like 4/inmunología , Receptor Toll-Like 9/genética , Receptor Toll-Like 9/inmunologíaRESUMEN
Although chloroquine (CQ) monotherapy is now generally inadequate for the treatment of Plasmodium falciparum malaria in northern Ghana--recently, 58% of 225 children failed treatment by day 14--use of the drug continues because of its low cost and wide availability. The risk factors associated with CQ-treatment failure in this region of Africa, including the T76 mutation in the chloroquine resistance transporter (pfcrt) gene and the Y86 mutation in the multidrug resistance (pfmdr1) gene of P. falciparum, have now been investigated, and genotype-failure indices (GFI) have been calculated. Treatment failure was found to be associated with young age, poor nutritional status, pfcrt T76 and pfmdr1 Y86, and early treatment failure (ETF) was also associated with high parasitaemia. The presence and concentration of 'residual' CQ in the blood of patients immediately before they were treated with CQ for the present study appeared to have no effect on outcome. Presence at recruitment of pfcrt T76 or pfmdr1 Y86 or both mutations increased the risk of treatment failure by 3.2-, 2.4- and 4.5-fold, and the risk of ETF by 9.8-, 2.7- and 10.2-fold, respectively. The pfcrt T76 GFI for clinical and all treatment failures were 2.8 and 1.4, respectively. These indices were relatively low in the younger children, those with malnutrition, and those with high parasitaemias when treated. Residual CQ did not affect the GFI substantially. Both pfcrt T76 and, to a lesser extent, pfmdr1 Y86 would be useful tools for the surveillance of CQ resistance in northern Ghana. In the current transition phase to alternative first-line treatment for P. falciparum malaria, it should be possible to provide estimates of the level of CQ resistance by monitoring the prevalences of these mutations.
Asunto(s)
Transportadoras de Casetes de Unión a ATP/genética , Antimaláricos/uso terapéutico , Cloroquina/uso terapéutico , Malaria Falciparum/tratamiento farmacológico , Proteínas de la Membrana/genética , Proteínas Protozoarias/genética , Animales , Niño , Preescolar , Farmacorresistencia Microbiana , Femenino , Humanos , Lactante , Recién Nacido , Malaria Falciparum/complicaciones , Malaria Falciparum/parasitología , Masculino , Desnutrición/complicaciones , Proteínas de Transporte de Membrana , Mutación , Parasitemia/tratamiento farmacológico , Plasmodium falciparum/genética , Insuficiencia del TratamientoRESUMEN
In a study performed in Tamale, in the Northern region of Ghana, cystatin C, a new and sensitive indicator of the glomerular filtration rate (GFR), was used to estimate the frequency of renal dysfunction in 78 children with uncomplicated, Plasmodium falciparum malaria. The excretion in urine of albumin, immunoglobulin G and alpha1-microglobulin was also investigated. Plasma concentrations of cystatin C were found to be elevated in 17% of the children, indicating subclinical impairment of renal function. As most (85%) of the children had glomerular as well as tubular patterns of proteinuria, it appears that both glomerulonephritis and damage to tubular cells often occur in P. falciparum malaria.
Asunto(s)
Lesión Renal Aguda/complicaciones , Malaria Falciparum/complicaciones , Lesión Renal Aguda/fisiopatología , Albuminuria/complicaciones , Albuminuria/fisiopatología , alfa-Globulinas/orina , Preescolar , Cistatina C , Cistatinas/sangre , Inhibidores de Cisteína Proteinasa/sangre , Femenino , Ghana , Tasa de Filtración Glomerular/fisiología , Humanos , Inmunoglobulina G/orina , Túbulos Renales/fisiopatología , Malaria Falciparum/fisiopatología , Masculino , Inhibidores de Proteasas/orinaRESUMEN
Chloroquine (CQ) resistance in Plasmodium falciparum contributes to growing malaria-attributable morbidity and mortality in sub-Saharan Africa. However, the extent and degree of such resistance vary considerably between endemic areas. Data on CQ resistance in northern Ghana are almost entirely lacking. The therapeutic efficacy of CQ in uncomplicated malaria was therefore assessed, in a standard, 14-day protocol, in 225 children aged <5 years in Tamale, in the Northern region of Ghana. Early treatment failure (ETF) was observed in 11% of the children and late treatment failure in 18%. High initial parasite density and young age were independent predictors for ETF. Resistant parasitological responses (RI-RIII) were seen in 57% of the cases that could be classified. More than half of these responses occurred in children fulfilling the criteria for adequate clinical response (ACR), indicating a considerable lack of agreement between parasitological and clinical outcome. During the follow-up period, haemoglobin levels increased by approximately 1g/dl not only in patients with ACR but also in those who experienced clinical failure more than 1 week post-treatment. As CQ-treatment failure occurred in >25% of the children and more than half of the parasitological responses indicated resistance, current recommendations for the treatment of uncomplicated malaria in young children in northern Ghana have to be reconsidered.