Identification of Cathepsin L gene from Hyalomma anatolicum and its comparative sequence analysis with Rhipicephalus (Boophilus) micro plus and other hard ticks

Socio-economic impact of ticks and tick-borne diseases on animals and human beings have been further enhanced by increasing acaricide resistant tick population. To mitigate the problem, introduction of immunoprophylatic measures along with other components of integrated tick management (ITM) is a promising option. However, identification and validation of novel tick protective molecules are the biggest challenges to date. Moreover, genetic homogeneity of the targeted gene(s) among the targeted tick species, is one of the important requirement for development of cross-protective anti-tick vaccine. Cathepsin L (CathL), a cysteine protease, having potent haemoglobinase activity playing important role in digestion of blood acquired from the host, was amplified, cloned and sequenced from two important Indian tick species, Hyalomma anatolicum and Rhipicephalus (Boophilus) micro plus. The deduced amino acid sequence analysis of 939 bp and 1030 bp cloned CathL gene of reference tick H. anatolicum IVRI line II and R. (B.) micro plus line I, respectively, reveals sequence similarity of 87.9%. Whereas, sequence identity of IVRI line II and I ticks with other tick species was 57.3–89.5% and 57.7–98.5%, respectively. Phylogenetic analysis revealed HaCathL (H. anatolicum-Cathepsin L) and BmCathL (B. micro plus-Cathepsin L) have high degree ofsequence conservation with CathL from other tick species compared to bovine CathL. Bioinformatics and comparative analysis predicted many post-translational modification sites in variable numbers, amongst the CathL of ticks, mosquitoes, nematode and bovines.