Research Articles
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A research article reports the results of original research, assesses its contribution to the body of knowledge in a given area, and is published in a peer-reviewed scholarly journal. The faculty publications through published and on-going articles/researches are captured in this community
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Item A randomized, double-blind, placebo-controlled, dose-ranging trial of tafenoquine for weekly prophylaxis against Plasmodium falciparum(Clinical Infectious Diseases, 2003-03) Hale, B.R.; Owusu-Agyei, S.; Fryauff, D.J.; Koram, K.A.; Adjuik, M.; Oduro, A.R.; Prescott, W.R.; Baird, J.K.; Nkrumah, F.; Ritchie, T.L.; Franke, E.D.; Binka, F.N.; Horton, J.; Hoffman, S.L.Tafenoquine is a promising new 8-aminoquinoline drug that may be useful for malaria prophylaxis in non-pregnant persons with normal glucose-6-phosphate dehydrogenase (G6PD) function. A randomized, double-blind, placebo-controlled chemoprophylaxis trial was conducted with adult residents of northern Ghana to determine the minimum effective weekly dose of tafenoquine for the prevention of infection by Plasmodium falciparum. The primary end point was a positive malaria blood smear result during the 13 weeks of study drug coverage. Relative to the placebo, all 4 tafenoquine dosages demonstrated significant protection against P. falciparum infection: for 25 mg/week, protective efficacy was 32% (95% confidence interval [CI], 20%-43%); for 50 mg/week, 84% (95% CI, 75%-91%); for 100 mg/week, 87% (95% CI, 78%-93%); and for 200 mg/week, 86% (95% CI, 76%-92%). The mefloquine dosage of 250 mg/week also demonstrated significant protection against P. falciparum infection (protective efficacy, 86%; 95% CI, 72%-93%). There was little difference between study groups in the adverse events reported, and there was no evidence of a relationship between tafenoquine dosage and reports of physical complaints or the occurrence of abnormal laboratory parameters. Tafenoquine dosages of 50, 100, and 200 mg/week were safe, well tolerated, and effective against P. falciparum infection in this study population.Item Seasonal profiles of malaria infection, anaemia, and bednet use among age groups and communities in northern Ghana.(Tropical Medicine and International Health, 2003) Koram, K.A.; Owusu-Agyei, S.; Fryauff, D.J.; Anto, F.; Atuguba, F.; Hodgson, A.; Hoffman, S.L.; Nkrumah, F.K.We conducted all-age point prevalence surveys to profile the severity and seasonality of malaria and anaemia in Kassena-Nankana District of northern Ghana. Random cross-sectional surveys were timed to coincide with the end of low (May 2001) and high (November 2001) malaria transmission seasons and to yield information as to the potential value of haemoglobin (Hb) levels and parasitaemia as markers of malaria morbidity and/or malaria vaccine effect. Parasitaemia was found in 22% (515 of 2286) screened in May (dry-low transmission), and in 61% of the general population (1026 of 1676) screened in November (wet-high transmission). Malaria prevalence in May ranged from 4% (infants <6 months and adults 50–60 years) to 54% (children 5–10 years). Age-specific malaria prevalence in November ranged from 38% (adults 50–60 years) to 82% (children 5–10 years). Differences between low- and high-transmission periods in the prevalence of severe anaemia (SA) among young children (6–24 months) were unexpectedly comparable (low, 3.9%vs. high, 5.4%; P = 0.52) and greatly reduced from levels measured in this same community and age group in November 2000 (12.5%) and November 1996 (22.0%). Despite the lower frequency of anaemia/SA in young children surveyed in 2001, it was still clear that this condition was strongly associated with parasitaemia and that children under 5 years of age experienced a significant drop in their mean Hb levels by the end of the high transmission season. Prevalence of parasitaemia was significantly lower (P < 0.01) among infants and young children (<2 years) whose parents reported the use of bednets. There was a significantly lower risk of parasitaemia among infants [odds ratio (OR) 6–8] and young children (OR 3–4) living in the central, more urbanized sector of the study area.Item High frequency of circulating γδ T cells with dominance of the V(δ)1 subset in a healthy population.(International Immunology, 2000) Hviid, L.; Akanmori, B.D.; Loizon, S.; Kurtzhals, J.A.L.; Ricke, C.H.; Lim, A.; Koram, K.A.; Nkrumah, F.K.; Mercereau-Puijalon, O.; Behr, C.TCR γδ+ cells constitute <5% of all circulating T cells in healthy, adult Caucasians, and Vδ1+ cells constitute a minority of these cells. In contrast to TCR αβ+ cells, their repertoire is selected extrathymically by environmental antigens. Although increased frequencies of Vδ1+ cells are found in several diseases, their function remains obscure. Here we show that the frequency of peripheral blood γδ T cells in healthy West Africans is about twice that of Caucasians, mainly due to a 5-fold increase in Vδ1+ cells, which is consequently the dominant subset. No age dependency of Vδ1 frequencies was identified and the Vδ1+ cells in the African donors did not show preferential Vγ chain usage. Analysis of the CDR3 region size did not reveal any particular skewing of the Vδ1 repertoire, although oligoclonality was more pronounced in adults compared to children. The proportions of CD8+, CD38+ and CD45RAhiCD45RO– cells within the Vδ1+ subset were higher in the African than in the European donors, without obvious differences in expression of activation markers. No significant correlations between levels of Vδ1+ cells and environmental antigens or immunological parameters were identified. Taken together, the evidence argues against a CDR3-restricted, antigen-driven expansion of Vδ1+ cells in the African study population. Our study shows that high frequencies of TCR γδ+ cells with dominance of the Vδ1+ subset can occur at the population level in healthy people, raising questions about the physiological role of Vδ1+ T cells in the function and regulation of the immune system.Item Malaria vector studies in two ecological zones in southern Ghana.(African Entomology, 2001) Appawu, M.A.; Baffoe-Wilmot, A.; Afari, E.A.; Dunyo, S.; Koram, K.A.; Nkrumah, F.K.A two-year longitudinal malaria vector study was carried out in two communities, Dodowa and Prampram, located in the coastal forest and coastal savannah zones, respectively, of the Dangme West district of Ghana. Anopheles gambiae s.l. Giles was most prevalent in both study areas, followed by An. funestus Giles in Dodowa and An. pharoensis Theobald in Prampram. Anopheles gambiae s.s. occurred in sympatry with An. melas Theobald in Prampram. Small numbers of An. nili Theobald, An. hancocki Edwards, An. coustani Laveran, An. moucheti Evans and An. hargreavesi Evans were collected in Dodowa and their role in transmission was negligible. Anopheles gambiae s.l. and An. funestus were found to be the major human-biting species in Dodowa, while An. gambiae s.l. and An. pharoensis were the most common biting mosquitoes in Prampram. The overall biting rate of the anophelines at Dodowa was twice that at Prampram. Anopheles gambiae s.l. and An. funestus were identified as the main vectors of malaria by salivary gland dissections. Overall mean infectivity rate of both species was approximately 2.5 times higher at Dodowa than at Prampram. Anopheles pharoensis was not found to be infected with Plasmodium parasites. The intensity of malaria transmission at Dodowa, the coastal forest area, was about six times higher than Prampram, the coastal savanna area. Some aspects of control strategies are discussed.