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BackgroundVariant surface antigens (VSA) exposed on the membrane of Plasmodium falciparum infected erythrocytes mediate immune evasion and are important pathogenicity factors in malaria disease. In addition to the well-studied PfEMP1, the small VSA families RIFIN, STEVOR and PfMC-2TM are assumed to play a role in this process.MethodsThis study presents a detailed comparative characterization of the localization, membrane topology and extraction profile across the life cycle of various members of these protein families employing confocal microscopy, immunoelectron microscopy and immunoblots.ResultsThe presented data reveal a clear association of variants of the RIFIN, STEVOR and PfMC-2TM proteins with the host cell membrane and topological studies indicate that the semi-conserved N-terminal region of RIFINs and some STEVOR proteins is exposed at the erythrocyte surface. At the Maurer’s clefts, the semi-conserved N-terminal region as well as the variable stretch of RIFINs appears to point to the lumen away from the erythrocyte cytoplasm. These results challenge the previously proposed two transmembrane topology model for the RIFIN and STEVOR protein families and suggest that only one hydrophobic region spans the membrane. In contrast, PfMC-2TM proteins indeed seem to be anchored by two hydrophobic stretches in the host cell membrane exposing just a few, variable amino acids at the surface of the host cell.ConclusionTogether, the host cell surface exposure and topology of RIFIN and STEVOR proteins suggests members of these protein families may indeed be involved in immune evasion of the infected erythrocyte, whereas members of the PfMC-2TM family seem to bear different functions in parasite biology.Electronic supplementary materialThe online version of this article (doi:10.1186/s12936-015-0784-2) contains supplementary material, which is available to authorized users.

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Schistosomiasis remains a serious world-wide public health problem with a still unfulfilled need for routine cost-effective methods of diagnosis. Such methods are required not only for people in endemic areas, but increasingly for tourists who may have become infected during visits to such places. This article reviews the wide range of immunoassays and antigenic preparations that have been shown to have potential for diagnosis of schistosomiasis by the indirect method of antibody detection. Antigens in native form derived from cercariae, adult worms and eggs are considered, as well as schistosome antigens produced by recombinant DNA technology and the schistosome cross-reactive antigen, keyhole limpet haemocyanin (KLH). Respective advantages and disadvantages of antibody detection, circulating antigen detection and parasitological methods of diagnosis are analysed. It is suggested that due to the relative insensitivity of both parasitology and antigen detection, antibody detection methods could find increasing use in situations of low infection intensity.