Comparison of the two different recombinant proteins representing region II of the duffy binding protein of plasmodium vivax by assaying for natural antibodies
Two different recombinant proteins representing region II of the Duffy Binding Protein of Plasmodium vivax, DBP and PvRII expressed in the bacculovirus and Eschericia coli vector systems, respectively, were compared by assaying the total immunoglobulin (IgM + IgG) responses of sera of patients with acute vivax malaria in an indirect ELISA. The patients were from two malaria endemic areas, Anuradhapura (n=64) and Kataragama (n=90), and a nonendemic area, Colombo (n=90). The antibody prevalence was 50% and 44% from Anuradhapura, 39% and 28% Kataragama and 57% and 41% from Colombo, for PvRII and DBP, respectively. The antibody prevalence for PvRII was higher than that for DBP in each test area, that was significant only in Colombo (p=0.001). The percentages of patients that they responded to both proteins were 34% (n=22), 19% (n=17) and 40% (n=36) from Anuradhapura, Kataragama and from Colombo, respectively. In comparison, a significantly lower (p=0.007) percentage of individuals from Kataragama responded to both proteins. Further 16% (n=10) from Anuradhapura, 19% (n=17) from Kataragama and 16% (n=14) from Colombo preferentially recognised PvRII, whereas, corresponding values for DBP were 9% (n=6), 10% (n=9) and 1% (n=1), respectively, where this difference was significant only in Colombo (p=0.031). Among the previously non-exposed patients from Colombo, 24% responded preferentially to PvRII whereas it was only 3% for DBP (p=0.021). On the other hand, of the previously exposed patients from Colombo, 10% preferentially responded to PvRII whereas no preferential recognition of DBP was observed (p=0.063). Thus the results of this study show a higher natural antibody response to recombinant protein PvRII, which represents the functional conformation of region II of the Duffy Binding Protein
