Nosema bombycis, a pathogen of silkworm pebrine, is an obligate unicellular eukaryotic parasite. It is reported that the spore wall proteins have essential functions in the adherence and infection process of microsporidia. To date, the information related to spore wall proteins from microsporidia is still limited. Here, a 44 kDa spore wall protein NbSWP16 was characterized in N. bombycis. In NbSWP16, a 25 amino acids signal peptide and 3 heparin binding motifs were predicted. Interestingly, a region that contains 3 proline-rich tandem repeats lacking homology to any known protein was also present in this protein. The immunofluorescence analysis (IFA) demonstrated that distinct fluorescent signals were detected both on the surface of mature spores and the germinated spore coats. Immunolocation by electron microscopy revealed that NbSWP16 localized on the exospore regions. Finally, spore adherence analysis indicated that spore adherence to host cell was decreased more than 20% by anti-NbSWP16 blocking compared with the negative control in vitro. In contrast with anti-NbSWP16, no remarkable decrement inhibition was detected when antibodies of NbSWP16 and NbSWP5 were used simultaneously. Collectively, these results suggest that NbSWP16 is a new exospore protein and probably be involved in spore adherence of N. bombycis.

A genomic library of Babesia caballi DNA was constructed in the plasmid vector pUC13. The specificity of the clones for B. caballi was established by the lack of hybridization to Babesia equi, Babesia bovis, Babesia bigemina and equine DNA. Two probes, pBC11 and pBC191, were isolated that could detect 0·25 ng and 0·125 ng of B. caballi DNA, corresponding to a parasitaemia of 0·12% and 0·06% respectively. pBC191 could detect B. caballi parasites in the blood of an experimentally infected horse as well as in naturally infected horses.