Members of this family are found in Babesia species. Though not in this Pfam family, rhoptry-associated proteins are also found in Plasmodium falciparum. Indeed, animal infection with Babesia may produce a pattern similar to human malaria [4]. Rhoptry organelles form part of the apical complex in apicomplexan parasites. Rhoptry-associated proteins are antigenic, and generate partially protective immune responses in infected mammals. Thus RAPs are among the targeted vaccine antigens for babesial (and malarial) parasites. However, RAP-1 proteins are encoded by by a multigene family; thus RAP-1 proteins are polymorphic, with B and T cell epitopes that are conserved among strains, but not across species [1,2,5]. Antibodies to Babesia RAP-1 may also be helpful in the serological detection of Babesia infections [3].

1: Structure, sequence, and transcriptional analysis of the Babesia bovis rap-1 multigene locus. Suarez CE, Palmer GH, Hotzel I, McElwain TF; Mol Biochem Parasitol 1998;93:215-224. PMID:9662706

2: Genetic variation in the dimorphic regions of RAP-1 genes and rap-1 loci of Babesia bigemina. Hotzel I, Suarez CE, McElwain TF, Palmer GH; Mol Biochem Parasitol 1997;90:479-489. PMID:9476795

3: Detection of equine antibodies to babesia caballi by recombinant B. caballi rhoptry-associated protein 1 in a competitive-inhibition enzyme-linked immunosorbent assay. Kappmeyer LS, Perryman LE, Hines SA, Baszler TV, Katz JB, Hennager SG, Knowles DP; J Clin Microbiol 1999;37:2285-2290. PMID:10364599

4: Modulation of host immune responses by protozoal DNA. Brown WC, Suarez CE, Shoda LK, Estes DM; Vet Immunol Immunopathol 1999;72:87-94. PMID:10614497

5: Helper T-cell epitopes encoded by the Babesia bigemina rap-1 gene family in the constant and variant domains are conserved among parasite strains. Brown WC, McElwain TF, Hotzel I, Suarez CE, Palmer GH; Infect Immun 1998;66:1561-1569. PMID:9529082