Fig. 2

Intra-species correlations and cross-species reactivities to serological responses to recombinant Plasmodium spp. antigens. The immunoreactivities of the named antigens from each Plasmodium species to diagnosed patient sera were quantified by ELISA and their pairwise correlation determined (a). For P. falciparum, P. vivax, P. ovale and P. malariae infections, sera were obtained from Swedish travellers to malaria-endemic regions increasing the chances of a mono-infection; P. knowlesi infections were from Malaysian patients. Spearman correlations for each antigen pair show some expected clusters of correlations within a species, especially for P. falciparum and P. vivax where more samples were available, and potential cross-reactivity between antigens across species were identified. b Serological responses to P. falciparum and P. vivax HPzz orthologues are likely to be cross-reactive despite low sequence identity between orthologues. The immunoreactivity to the P. falciparum and P. vivax HPzz antigens are plotted for each patient with their diagnosis indicated. c Responses to P. knowlesi and P. vivax P12 orthologues show no evidence of cross-reactivity despite high primary protein sequence identity between orthologues. p values from a t-distribution significance test are indicated by asterisks. *p < 0.05; **p < 0.01; ***p < 0.001