Association between HLA type and antibody response to malaria sporozoite and gametocyte epitopes is not evident in immune Papua New Guineans.

HLA-A,B,C and DR types were determined for 46 adults living in the Madang area of Papua New Guinea. Sera from these individuals were tested by ELISA for antibodies against: (i) sonicated schizont extract of Plasmodium falciparum; (ii) circumsporozoite repeat regions of P. falciparum and P. vivax; and (iii) epitopes on the 230 and 48/45 kD gametocyte antigens of P. falciparum. All sera were from highly immune individuals and reacted strongly to the schizont antigen. The proportions responding to circumsporozoite repeat regions were 60.7% and 23.9% for P. falciparum and P. vivax, respectively. Between 32.6 and 47.8% of adults responded to each gametocyte epitope as assessed by inhibition of monoclonal antibodies. The limited number of alleles present at each HLA locus which is characteristic of coastal Papua New Guinea was observed. Five HLA-DR alleles were detected, of which only three (HLA-DR2, 4 and w5) were present at frequencies over 0.12. All individuals possessed at least one DR2,4 or w5 allele, and 96% of individuals possessed DR2, or 4 or both. There was no evidence for association between HLA type and antibody response to circumsporozoite repeat regions or the gametocyte epitopes. Homozygotes for DR2 and 4 were able to respond to each antigen. These results imply that either there is no HLA restriction of the response to these antigens or that each DR type is responding to a different variant of the T-epitope. Even in the latter case the results are encouraging for the prospects of inclusion of an HLA-restricted T-epitope in a malaria vaccine for Papua New Guinea since a limited number of versions would be required to cover a population with an HLA profile similar to that in Madang.