Charakterisierung der Vakzinekandidaten Major Sperm Protein und Paramyosin von Dictyocaulus viviparus

Infections with the bovine lungworm induce a protective immunity in cattle hosts that prevents clinical symptoms for some month. This immunological feature provides the basis for the development of a vaccine based on recombinantly expressed antigens. Nucleic acid characterisation of the Major sperm protein (MSP) resulted in an mRNA sequence comprising 472 bp of which 381 bp belong to the coding sequence. The msp gene consists of 537 bp due to insertion of one intron. The transcript of the muscle structure protein paramyosin (pmy) is 3207 bp in length, whereas the respective genomic sequence counts 11,558 bp due to 19 intron insertions. Phylogenetic analysis showed that the expressed protein, which is encoded by 2631 bp and consists of 876 amino acids, is more closely related to pmy of arthropods than to that of trematodes and cestodes. Recombinant prokaryotic expression of pmy resulted in a functionally active protein binding bovine collagen as well as bovine IgG. In trematodes and cestodes, these two binding features are assumed to be involved in immune evasion mechanisms. Quantitative real time PCR resulted in an expected transcription profile for MSP by showing a very high transcription rate in adult males, whereas transcription in hypobiotic fifth stage larvae was relatively low and negligible in all other developmental stages. Maximum pmy transcription was observed in first stage larvae, which show highly active movement and rapid development. The results of the presented thesis characterise the two vaccine candidates on a molecular and bioinformatic level and with regard to their transcription pattern throughout the parasite’s life cycle. Furthermore, it was shown for the first time that nematode paramyosin has potential immune evasive properties and thus might exhibit extramuscular functions as well.