SCHISTOSOMA-JAPONICUM - HETEROGENEITY IN PARAMYOSIN GENES

Paramyosin is an integral muscle protein found in many invertebrates i ncluding schistosomes, and is considered an important candidate vaccin e antigen in schistosomiasis. The characterisation of natural molecula r variation in vaccine antigens including paramyosin is important beca use strain-specific vaccination may be necessary against schistosomias is japonica. We have isolated partial cDNAs encoding paramyosin from a n adult, Chinese strain Schistosoma japonicum gene library. Two Of the se cDNAs (B6 and Y6) encode the same region of paramyosin but their nu cleotide sequences differ at eight positions and their deduced amino a cid sequences differ by an arginine/cysteine substitution, demonstrati ng intrastrain variation in paramyosin. Southern blot analysis of geno mic DNA from the Chinese and Philippine strains of S. japonicum demons trated strain-related RFLPs at the paramyosin locus, and suggested tha t more than one copy of the paramyosin gene was present in the S. japo nicum genome. PCR-based RFLP analysis which exploited restriction site differences between B6 and Y6 showed that paramyosin genotype B6 was much more common in schistosome populations and verified the existence of introns in the paramyosin gene(s) of S. japonicum.