Identification and characterization of vaccine candidates against Hyalomma anatolicum-Vector of Crimean-Congo haemorrhagic fever virus.

Crimean-Congo haemorrhagic fever (CCHF) is a tick borne viral disease reported from different parts of the world. The distribution of the CCHF cases are linked with the distribution of the principal vector, Hyalomma anatolicum in the ecosystem. Presently, vector control is mainly dependent on repeated application of acaricides, results in partial efficacy and generated acaricide resistant tick strains. Amongst the different components of integrated management programme, immunization of hosts is considered as one of the sustainable component. To restrict CCHF virus spreading, use of anti-Hyalomma vaccines appears as a viable solution. Accordingly, present study was under taken to characterize and evaluate vaccine potential of two conserved molecules, ferritin2 (FER2) and tropomyosin (TPM). Silencing of the genes conferred a cumulative reduction (rejection + unable to engorge) of 61.3% in FER2 and 70.2% in TPM respectively. Furthermore, 44.2% and 72.7% reduction in engorgement weight, 63.6% and 94.9% reduction in egg masses in FER2 and TPM silenced ticks in comparison to LUC-control group was recorded. The recombinant protein, rHaFER2 was characterized as 35 kDa protein with pI of 5.84 and possesses iron binding domains. While rHaTPM is a 51kDa protein with pI of 4.94 having calcium binding domains. Immunization of cross-bred calves by rHaFER2 conferred 51.7% and 51.2% protection against larvae and adults of H. anatolicum challenge infestations. While rHaTPM conferred 63.7% and 66.4% protection against larvae and adults infestations, respectively. The results were comparable with the data generated by RNAi and it clearly showed the possibility for the development of anti-hyalomma vaccine to manage CCHF virus and Theileria annulata infection in human and animals.