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P Twumasi

Publications and source records attributed to P Twumasi.

6 recordsLinked to original sources
PubMed1992

Rosette formation in Plasmodium falciparum isolates and anti-rosette activity of sera from Gambians with cerebral or uncomplicated malaria.

The ability of Plasmodium falciparum-infected red blood cells (RBC) to form spontaneous erythrocyte rosettes was studied in 130 fresh isolates from Gambian children with cerebral or uncomplicated malaria from August to November 1990. All isolates (24 of 24) from patients with cerebral malaria formed rosettes, but only 61 of 106 isolates from children with uncomplicated malaria formed rosettes. The mean rate of rosette formation in isolates from children with cerebral malaria (28.3%) was significantly greater than that in isolates from children with uncomplicated malaria (8.5%). Giant rosettes were more frequently formed in isolates from patients with cerebral malaria than in those from patients with uncomplicated malaria. Sera of children with cerebral disease generally lacked anti-rosette activity, while many sera from children with uncomplicated malaria showed strong anti-rosette activity when tested against the patients' ow parasites. Some sera that were devoid of autologous rosette-disrupting activity were able to disrupt rosettes formed in other isolates, indicating the presence of different rosette formation mechanisms. Forty percent (6 of 15) of the sera from patients with cerebral malaria caused microagglutination of the patients' own uninfected and infected RBC, while only 10% (3 of 31) of sera from children with uncomplicated disease caused microagglutination. The ability of infected RBC to bind to melanoma cells grown in vitro did not differ between patients with cerebral or uncomplicated malaria. The results of this study, taken in conjunction with our previous findings, establish a strong association between rosette formation in P. falciparum-infected RBC and cerebral malaria.

Adolescent↗
PubMed1991

Common west African HLA antigens are associated with protection from severe malaria.

A large case-control study of malaria in West African children shows that a human leucocyte class I antigen (HLA-Bw53) and an HLA class II haplotype (DRB1*1302-DQB1*0501), common in West Africans but rare in other racial groups, are independently associated with protection from severe malaria. In this population they account for as great a reduction in disease incidence as the sickle-cell haemoglobin variant. These data support the hypothesis that the extraordinary polymorphism of major histocompatibility complex genes has evolved primarily through natural selection by infectious pathogens.

Animals↗
PubMed1990

TNF concentration in fatal cerebral, non-fatal cerebral, and uncomplicated Plasmodium falciparum malaria.

Plasma levels of tumour necrosis factor (TNF) were significantly higher in 178 Gambian children with uncomplicated malaria due to Plasmodium falciparum than in 178 children with other illnesses. 110 children with cerebral malaria were studied shortly after admission to hospital; 28 subsequently died. Compared with the children with uncomplicated malaria, mean plasma TNF levels were twice as high in cerebral malaria survivors and ten times as high in the fatal cases. Although high TNF levels were associated with high parasitaemia and with hypoglycaemia, they predicted fatal outcome in cerebral malaria independently of parasitaemia and glucose concentrations. Concentrations of interleukin-1 alpha, but not interferon gamma, were also related to the severity of malaria. We conclude that increased TNF production is a normal host response to P falciparum infection, but that excessive levels of production may predispose to cerebral malaria and a fatal outcome.

Animals↗
PubMedDate not supplied

Sensitivity of Plasmodium falciparum in The Gambia to co-trimoxazole.

In The Gambia co-trimoxazole is used widely to treat children with an acute respiratory infection (ARI). Because malaria may sometimes be mistaken for ARI, some children with malaria are treated with co-trimoxazole. Therefore, we investigated the sensitivity of Gambian isolates of Plasmodium falciparum to this drug. Six days after the start of treatment with co-trimoxazole 3.3% of blood films of 65 asymptomatic subjects were positive, and 7.7% were positive after 21 d. One of 10 patients with ARI and malaria treated with co-trimoxazole had a positive blood film 3 d after the start of treatment but was negative thereafter. All 10 patients recovered satisfactorily. Thirty 'wild' isolates of P. falciparum were tested in vitro against co-trimoxazole at a ration of 5 parts sulphamethoxazole (SMZ) to 1 part trimethoprim (TMP). The mean EC50s, using a 36 h assay, were 1.2 x 10(-7) and 2.5 x 10(-8) M for SMZ and TMP respectively. When a [3H]hypoxanthine incorporation assay was employed, values of 5.7 x 10(-7) M for SMZ and 1.2 x 10(-7) M for TMP were obtained. These values are well below the peak plasma concentration. Our findings suggest that co-trimoxazole is effective against falciparum malaria in The Gambia. However, if it were to be used widely, the parasite would be likely to develop resistance to this and other dihydrofolate reductase inhibitor antimalarials.

Animals↗