Furthermore, the prevalence rate (2 test, = 0.02) and the level (Mann-Whitney test, = 0.0428) of IgG1 antibody were higher in LUF6000 protected than in unprotected children (figure 3B ?). the discipline parasites11 and may also become induced by targeted disruption of the EBA-175 gene.12 EBA-175 has a common part in merozoite invasion since the antibodies against region II block invasion pathways that do not involve sialic acid.13 It has been demonstrated that EBA-175 is also indicated on pre-erythrocytic parasites14 and that immunization with EBA-region II protects monkeys from challenge.15 Although EBA-175 antigen is likely to be involved in the development of protective immunity against malaria, the antibody response to EBA-175 in humans living in malaria endemic regions remains poorly characterized,16 including the response to EBA-peptide 4 which is expected to include a B-cell epitope.6 The aim of the present study was to measure antibodies directed against EBA peptide 4, as well as isotype distribution in school children living in Dienga, Gabon. The influence of age on the levels of these antibodies has been investigated, as well as their relationship with parasite denseness and event of medical malaria assault during a 12-month follow-up. Materials and Methods Subjects and field methods The town under study was Dienga in southeast Gabon where a medical, biological and parasitological follow-up was carried out among the primary school-going population during the whole malaria transmission time of year of 1995.17 Clinical and parasitological data allowed us to distinguish between protected and unprotected children. Briefly, protected children were defined as those who by no means presented during the whole survey having a febrile show (defined as axillary temp 37C) associated with neither parasitemia 400/l nor the presence of 4-aminoquinoline LUF6000 metabolite in urine. Unprotected children were defined as those who presented with at least one malaria assault defined as the association of fever and parasitemia 5000/l.17,18 The unique criterion of selection was the availability of sufficient quantity of plasma, which was acquired for 158 children. Moreover, from February 1995 to March 1996, all children were regularly screened for illness by finger prick blood sampling every 2 weeks and also whenever fever occurred. The solid blood PP2Abeta smears were prepared and stained with Giemsa. Parasite densities were recorded as the number of parasites/l of blood, assuming an average leukocyte count of 8000/l. Each value of parasite denseness was simultaneously modified to age and day of sampling by calculating the percentage of individual parasite denseness (parasite denseness + 1) to the geometric imply of all (parasite denseness + 1) ideals recorded at each day of sampling in LUF6000 the group of children of the same age. For each child who offered at least six recorded solid blood smears, the geometric mean of day and age modified (GMA) parasite densities LUF6000 was determined. For the need of statistical analysis, log-transformed values of the GMA parasite denseness were regarded as. Antigen and antibody measurements A synthetic peptide used as antigen was EBA-peptide 4 (aa 1062-1103:SNNEYKVNEREDERTLTKEYEDIVLKSHMNRESDDGELYDEN). This peptide was synthesized by Interactiva Biotechnology (Ulm, Germany). The plasma was collected from 158 children at the end of the follow-up. Antibodies were measured by enzyme-linked immunosorbent assay (ELISA) using 1 g/ml of EBA peptide 4, LUF6000 a 100-collapse diluted plasma and a 2,000-collapse diluted goat anti-human IgG (Fc specific) conjugated to alkaline phosphatase (Sigma,.