Interaction of HLA and age on levels of antibody to Plasmodium falciparum rhoptry-associated proteins 1 and 2

The Plasmodium falciparum rhoptry-associated proteins 1 and 2 (RAP1 and RAP 2) are candidate antigens for a subunit malaria vaccine. The design of the study, which looks at the acquisition of immunity to malaria from childhood to old age, has allowed us to document the interaction of HLA and age on l evels of antibody to specific malarial antigens. Antibodies reach maximum l evels to RAP1 after the age of 15 but to RAP2 only after the age of 30. The effect of HLA-DRB1 and -DQB1 and age on levels of antibody to rRAP1 and rR AP2 was analyzed with a multiple regression model in which all HLA alleles and age were independent variables. DQB1*0301 and -*03032 showed an age-dep endent association with levels of antibody to rRAP1, being significant in c hildren 5 to 15 years (P < 0.001) but not in individuals over 15 years of a ge. DRB1*03011 showed an age-dependent association with antibody levels to rRAP2; however, this association was in adults over the age of 30 years (P < 0.01) but not in individuals under the age of 30 years. No associations w ere detected between DRB1 alleles and RAP1 antibody levels or between DQB1 alleles and RAP2 antibody levels. Thus, not only the HLA allele but also th e age at which an interaction is manifested varies for different malarial a ntigens. The interaction may influence either the rate of acquisition of an tibody or the final level of antibody acquired by adults.