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Ekala is in receipt of a fellowship from MIM/TDR grants (980072). Gabon, IgG, MSP 2, malaria INTRODUCTION The asexual blood stages of are responsible for the clinical manifestations of malaria and attempts have been made to identify asexual blood stage antigens that may be of importance in the development of immunity to the disease [1]. Several proteins are being investigated, among them the merozoite surface protein 1 and 2 (MSP1 and MSP2), which are considered as promising vaccine candidates [2]. Because of their extensive polymorphisms, MSP1 and MSP2 genes have been used widely for the characterization of infections [3] and specifically to determine the multiplicity of infections in residents from endemic areas [4C7]. It appears that infections with a large number of antigenically diverse parasite populations are required before acquiring an Ziprasidone hydrochloride effective antiparasite immunity. Thus, acquisition of clinical immunity and incomplete antiparasite immunity is reflected by asymptomatic carriage of parasites which occurs commonly in residents from malaria endemic areas. Some experiments performed have suggested that one of the mechanisms underlying clinical immunity to malaria in patients living in areas of endemicity is the inhibition of parasite multiplication by antibodies [8]. It is reasonable to assume that if protection is mediated by antibodies, there should be a relationship between the level and/or concentration of antibodies and the clinical outcome of the disease. Studies concerning the role of specific humoral immune responses in naturally developing clinical immunity to defined malaria antigens and/or epitopes are therefore important. While total IgG antibody responses have been analysed widely to determine immunological status of infected individuals [9,10], the precise allele specificity of the antibodies to polymorphic regions of merozoite surface proteins remains poorly investigated. We have previously shown, using 82 synthetic linear 15-mer peptides, overlapping on seven amino acids, which scanned a reference allele from each of the three allelic families of MSP1 gene and included a large array of sequence variants [11,12], the contribution of strain specific immunity to antiparasite immunity. An age-dependence in the recognition of the number of different MSP1 peptides by asymptomatic subjects was found with a particular increase after the age Ziprasidone hydrochloride of 14 years [11]. Using MSP2 recombinant proteins most of the studies showed that IgG antibodies represented a good surrogate measure of protection and suggested that protective effects are due probably to IgG specific for variable regions of MSP2 molecules [9,13,14]. It has been reported by Ranford-Cartwright [15] that the degree of antibody reactivity to MSP2 molecule was sequence-dependent. Moreover, Rzepczyk [16] have shown, using mouse models, that MSP2 peptides were able to elicit antibodies. They also showed that those peptides can induce the proliferation of peripheral blood lymphocytes from subjects living in Honiara, Solomon Islands where is endemic [17]. As clearly defined B epitopes have not yet been described, the use of peptides corresponding to the variable and conserved regions of MSP2 could be useful in order to detect and quantify allelic family-specific antibodies. The present work aimed to evaluate the presence and levels of MSP2 allelic family-specific antibodies in individuals, older than 6 months with either asymptomatic infections or uncomplicated malaria, residing in an urban area of Gabon where malaria transmission is high and perennial. The antibody responses to MSP2 peptides were assessed using a set of 15-mer synthetic peptides corresponding to blocks 1C3 of MSP2, including some variable sequences. To ensure homologous peptide presentation on ELISA plates, biotinylated peptides were used [11,12]. In order to assess the development of allelic family-specific humoral immune responses to MSP2, 25 Gabonese patients with symptomatic infections were followed-up one week after inclusion. We sought to gain a better understanding of mechanisms involved in parasite surface antigen-specific antibody responses. MATERIALS AND METHODS Study area The study was carried out from March 1998 to March 1999 in the city Ziprasidone hydrochloride of Franceville, a province of Haut-Ogoou, south-eastern Gabon and was Rabbit polyclonal to AMIGO2 approved by the ethical committee of the International Center for Medical Research of Franceville (CIRMF). In this region, malaria (due mainly to transmission marked by two rainy seasons from February to May and October to December [18]. Study population Inclusion of patients was undertaken after obtaining their informed consent or that of their guardians. Patients more than 6 months old were recruited at the Hospital of Franceville. According to our malaria case definition [11], 45 patients presenting uncomplicated malaria (T.