Four [formula omitted]ine [formula omitted]roteinase [formula omitted]hibitors (serpin) from the brown ear tick, Rhiphicephalus appendiculatus; cDNA cloning and preliminary characterization

Abstract

While development of an anti- Boophilus microplus vaccine is advanced and practical, work on other economically important ticks such as Rhipicephalus appendiculatus is still in its infancy. Guess PCR primers, designed from a consensus amino acid sequence (NAVYKFG) motif were used with rapid amplification of cDNA ends (RACE) to clone four cDNAs encoding ser ine p roteinase in hibitors (serpin) from the brown ear tick Rhipicephalus appendiculatus. The four genes designated as R. appendiculatus serpin (RAS) -1 to -4 encode polypeptides of 378, 380, 398 and 486 amino acids long, respectively. Sequence comparison of RAS-1 to -4 predicted amino acid sequences to the serpin-like hypothetical protein from Ixodes ricinus ( Leboulle et al., 2002) revealed closer structural similarities among tick serpins. Expression analysis by RT-PCR showed that RAS-1 to -4 are expressed in other tick organs in addition to salivary glands and midguts. Except for RAS-3 whose expression level appears to be equivalent in all tick organs, RAS-1, -2 and -4 are predominantly expressed in the salivary glands. We have discussed our findings with reference to development of vaccines against R. appendiculatus.