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Host acceptability and suitability of four cereal stemborers (Lepidoptera) commonly occurring in eastern Africa, Sesamia calamistis Hampson, Busseola fusca (Fuller) (both Noctuidae), Chilo partellus Swinhoe (Crambidae), and Eldana saccharina Walker (Pyralidae), for a West African strain of Sturmiopsis parasitica (Curran) (Diptera: Tachinidae) were assessed. In addition, the outcome of multi-parasitism was studied using a local strain of the endoparasitic Cotesia sesamiae Cameron (Hymenoptera: Braconidae) as the competing parasitoid. Various parasitism sequences and time intervals between parasitism were chosen. Parasitism increased linearly with the number of planidia used per larvae and was 80% with eight planidia. All species were accepted for larviposition, but suitability varied greatly; parasitism was 75.2, 37.9, 34.8, and 23.8% with S. calamistis, B. fusca, E. saccharina, and Ch. partellus, respectively. Sturmiopsis parasitica outcompeted Co. sesamiae irrespective of the time interval between parasitism, and whether it was the first or second species to parasitize. This was mainly due to a longer egg-to-cocoon development time and a high cocoon-to-adult mortality in Co. sesamiae. The implications of these results for expanding the geographic range of the West African strain of the tachinid in Africa are discussed. [ABSTRACT FROM AUTHOR]

Background: Erythrocyte invasion by merozoites is an essential step in Plasmodium falciparum infection and leads to subsequent disease pathology. Proteins both on the merozoite surface and secreted from the apical organelles (micronemes, rhoptries and dense granules) mediate the invasion of erythrocytes; some of the molecules have been regarded as targets in the development of an anti-malaria vaccine. Recently, a subgroup of rhoptry neck proteins (PfRON2, PfRON4 and PfRON5) associated with the microneme protein apical membrane antigen AMA1 has been described as components of the moving junction complex that assists merozoite invasion into erythrocytes. However, unlike PfRON2, PfRON4 and PfRON5, the latest study suggested that PfRON3 might be located in the rhoptry bulb and participates in a novel PfRON complex (PfRON2, 3 and 4), but does not form a complex with AMA1. Additionally, the full-length PfRON3 protein possesses three transmembrane regions at the N-terminus, which is highly conserved among RON3 orthologues in the genus Plasmodium, Toxoplasma gondii and Eimeria tenella. Overall, these findings suggest that PfRON3 may play an important role in merozoite invasion into erythrocytes., Results: PfRON3 was primarily expressed during the late trophozoite stage, with a peak in transcription levels at 40 hours post-invasion. The subcellular localization of PfRON3 was confirmed that it is a merozoite rhoptry bulb protein. Additionally, the recombinant form of PfRON3 protein bound to the erythrocyte and was recognized by sera collected from malaria endemic areas in Africa, and anti-PfRON3 antibodies significantly inhibited merozoite invasion into erythrocytes., Methods: The expression of PfRON3 was analysed via real-time quantitative PCR, and the recombinant PfRON3 proteins were generated with an Escherichia coli expression system. The subcellular localization of PfRON3 was assessed with immunoelectron microscopy and immunofluorescence assay (IFA). The recognition PfRON3 by malaria immune sera was analysed with an enzyme-linked immunosorbent assay (ELISA). Erythrocyte-binding assays were performed using recombinant PfRON3 proteins and invasion inhibition assays were carried out with PfRON3-specific antibodies., Conclusion: This study confirmed that PfRON3 is a rhoptry protein with an erythrocyte-binding property, which is likely associated red blood cell invasion. PfRON3 is a potential vaccine candidate.