Genetic variability in cysteine protease genes ofHaemonchus contortus

Abstract

To increase the existent genetic variability in cysteine proteases, a polymorphism study was performed in Haemonchus contortus by comparing 2 different strains of the parasite: North American (NA) and Spanish (SP) strains. For this purpose, the polymorphism of 5 previously reported genes (AC-1, AC-3, AC-4, AC-5 and GCP-7) were analysed by PCR-SSCP and sequencing procedures. Based on the SSCP results, a total of 20 different alleles were identified for the 5 loci assessed. Except locus AC-5, all the loci were polymorphic. Loci AC-1, AC-3, AC-4 and GCP-7 showed 5, 8, 2 and 4 alleles, respectively. The allelic frequencies ranged from 0.0070 to 0.8560 and were significantly different between strains. In addition, nucleotide diversity analyses showed a significant variation within and between strains. The variations in the nucleotide sequence of the different alleles were translated in some cases into changes in the amino acid sequence. Evidence of genetic variability in cysteine proteases from two different strains of H. contortus for the same set of genes had not been previously reported.

Characterization of proteinases in different isolates of adult Haemonchus contortus

“…Cysteine proteinases are y35 kDa in size, suggesting that differences in the peptide profile at higher molecular weight are unlikely to be significant in terms of the ability of this complex to protect against different strains of H. contortus. However, at a genetic level, variability between cysteine proteinases expressed by the Moredun and American strains of H. contortus has been demonstrated previously (Rehman & Jasmer, 1998 ;Skuce et al 1999) and, more recently, between North American and Spanish strains (Ruiz et al 2004), although the functional implications remain to be evaluated. Further work is required to determine whether this genetic variability extends to the ISE and White River strains of H. contortus described in this study.…”

An AC-5 cathepsin B-like protease purified fromHaemonchus contortusexcretory secretory products shows protective antigen potential for lambs

“…AC-5 is described to be, among five CBL tested in two H. contortus isolates, the only homozygote and monoallelic CBL gene whereas the others were extremely polymorphic [24]. Therefore, AC-5 may be a particularly good vaccine target.…”