Malaria merozoite surface area protein 1 (MSP1) is cleaved in an
Malaria merozoite surface area protein 1 (MSP1) is cleaved in an essential step during erythrocyte invasion. control of MSP1 goes to completion during the successful invasion of a red blood cell, suggesting that it is a necessary step. Monoclonal antibodies (MAbs) that prevent invasion inhibit secondary processing of MSP1, suggesting that this is definitely their mechanism of action (4). Blocking antibodies (10) are not inhibitory but interfere with inhibitory antibody activity by competing for binding to the merozoite surface. This suggests an immune evasion mechanism to avoid the action of protecting antibodies (11). Here we present evidence that natural illness may induce both antibodies that inhibit MSP1 secondary processing and antibodies that block this inhibition. Prevalence of parasites. This study was carried out at Igbo-Ora and Idere in southwestern Nigeria. After educated consent was from their parents or guardians, children were recruited relating to a protocol that was examined and authorized by the Joint Honest Committee of the College of Medicine and the University or college College Hospital, Ibadan, Nigeria. parasitemia was common both at the end of the rainy time of year and in the middle of the dry time of year (Fig. ?(Fig.1),1), with no significant difference in the age distribution of the infected children between the two EPO906 time points. Overall, the rate of parasitemia declined with age (data not shown). FIG. 1. Prevalence of malaria parasitemia EPO906 among 343 children, 10 days to 15 years old, during the dry season (January to March 1999) and among 365 children with the same age distribution at the end of the rainy season (October to November 1999), at Idere and … Antibodies to MSP119 measured by ELISA. Plasma samples from 708 donors were analyzed by enzyme-linked immunosorbent assay (ELISA) for antibodies to recombinant MSP119 (6). The samples were diluted at a 1:25 ratio and then in twofold dilutions to 1 1:3,200; the reciprocal end point titer (the highest dilution that gave an absorbance value above that of the negative controls) was EPO906 log transformed, and data were expressed as geometric mean log reciprocal titers. There were no differences in the geometric mean log reciprocal titers between those individuals who had parasitemia (2.58) and those who did not (2.56) or between sexes (> 0.05, data not shown). In both the dry and the wet seasons, the mean log reciprocal titer for children under 12 months old (2.4) was the same as that for 12- to 60-month-old children. When samples collected during the dry season were compared, the antibody titers determined were higher for children of 6 years than for those of 5 years of age (< 0.01); in contrast, there was a decline with age in antibody titers for the plasma samples collected during the rainy season, though the difference between the two groups was not significant (> 0.05) (data Mouse Monoclonal to beta-Actin. not shown). Antibody-mediated inhibition of MSP142 processing. Plasma samples from 50 children, 1 month to 15 years of age, who were chosen randomly from the group of 343 children seen in the dry season were assayed for MSP1 processing-inhibitory activity. Merozoites were prepared according to the procedures of Blackman (1), and processing assays were performed essentially as described previously (4, 10). MSP142 and MSP133 were identified by enhanced chemiluminescence and exposure to autoradiographic film. The densities of the MSP142 and MSP133 bands were measured after a short exposure (2 to 5 s, in the linear density response range) with Scion (Frederick, Md.) image software. The relative proportion of MSP133 was calculated by use of the formula + is the amount of MSP142 remaining at the end of the assay and is the amount of MSP133 produced. The percentage of MSP142 processing was calculated by the formula 100(? ? are the relative proportions of MSP133 produced, respectively, in the reaction buffer alone, in the zero-hour control (levels of MSP133 present at the start of the assay), and in the presence of MAb or the plasma sample being tested. Of the 50 plasma samples analyzed at random, the results for 20 are shown (Fig. ?(Fig.2).2). Three examples, BP89, BP100, and NW46 (from donors aged 13, 11 and 6 years, respectively), demonstrated full inhibition of supplementary control of MSP1. Three additional examples, Identification19, NW69, and NW48 (from donors aged 2 weeks and 6 and 7 years, respectively), demonstrated significant inhibition of.