Investigation of Hazara Virus as a model for Crimean Congo Hemorrhagic Fever Virus.

Hazara virus (HAZV) is a member Nairoviridae family and belongs to the same serogroup as Crimean-Congo hemorrhagic fever virus (CCHFV), which is considered a severe public health threat. The absence of any preventive or therapeutic treatment against the CCHF disease places the virus in the high-risk group and required to study at biosafety level (BSL) 4. On the other hand, HAZV, a member of the same serogroup, has not been reported as a pathogen for humans. For this reason, HAZV constitutes a model for CCHFV, taking into account it's serological and phylogenetic similarity to CCHFV, and allows it studied in BSL-2. The NPs encoded by CCHFV and HAZV S segments are 59% similar to each other. In many bunyaviruses such as CCHFV, NP creates a high immune response and is used to detect antibodies against the virus. It is worthwhile to study the whole virus and HAZV NP to characterize the similarities between HAZV and CCHFV and utilize HAZV as a model for CCHFV infection. In this study, antigenic similarities between the two viruses were demonstrated by antibodies produced in different species (mouse and rabbit) against whole CCHFV and CCHFV NP, as well as CCHF convalescent human sera. For this purpose, whole virus HAZV and HAZV NP and as positive control CCHFV NP were used as antigens to conduct enzyme immunoassays (EIA) and western blotting with the above-mentioned antibodies. As a negative control, non-immunized rabbit or healthy human sera were used. As a result of the tests performed, a strong cross-reaction between HAZV and KKKAV was revealed. These results have drawn the preference for HAZV and CCHFAV NP' and the whole virus for significant similarities in humoral immune response and that HAZV can be used as a model for CCHFV. These results underlined that HAZV and CCHFV NPs and the whole virus share important similarities in humoral immune response and that HAZV can be used as a model for CCHFV