Allelic polymorphism at three unlinked loci coding for blood stage proteins of <i>Plasmodium falciparum</i> was studied serologically, using a panel of 27 monoclonal antibodies. The proteins, MSP1, MSP2 and Exp-1, exhibited 39, 8 and 2 serotypes respectively, among 567 Gambian, Nigerian, and Brazilian clinical isolates. In each of two years, within an urban/periurban study area in the Gambia, the observed number of 3-locus combinations was in accordance with expectations assuming random assortment between the loci, i.e. panmixia in the <i>P.falciparum</i> population. A mean of 2.0 <i>P.falciparum</i> clones was detected in patients from this area. Two clones within an individual were more frequently identical at the MSP1 locus than two clones picked randomly from the local population, indicating that non-identical sibling parasites are sometimes acquired from a single mosquito bite. Parasites isolated from children who sleep in the same room are very frequently identical at all three loci, suggesting that a single mosquito may inoculate more than one human on a given occasion. Intragenic recombination in the MSP1 gene accounts for much of the extensive allelic polymorphism detected serologically. Putative epitopes for several monoclonal antibodies are mapped on the basis of allelic sequence-serology correlations. Strong non-random associations between epitopes at different domains of MSP1 are broadly similar in three countries, which could be a result of differential selection on recombinant alleles. The frequencies of polymorphic epitopes of MSP1, MSP2 and Exp-1 remained stable over seven years in the Gambian study area, rare epitopes remained at a low frequency compared to common alternatives, suggesting that some of these polymorphisms are not maintained by frequency-dependent selection. Little evidence was obtained for association between patients' blood groups and merozoite surface protein polymorphisms, although one statistical association between blood group O and epitope 8F6/49 on MSP2 should be tested further.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:643392 |
| Date | January 1992 |
| Creators | Conway, David Joseph |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/13456 |
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