Exploring of Primate Models of Tick-Borne Flaviviruses Infection for Evaluation of Vaccines and Drugs Efficacy

Abstract

Tick-borne encephalitis virus (TBEV) is one of the most prevalent and medically important tick-borne arboviruses in Eurasia. There are overlapping foci of two flaviviruses: TBEV and Omsk hemorrhagic fever virus (OHFV) in Russia. Inactivated vaccines exist only against TBE. There are no antiviral drugs for treatment of both diseases. Optimal animal models are necessary to study efficacy of novel vaccines and treatment preparations against TBE and relative flaviviruses. The models for TBE and OHF using subcutaneous inoculation were tested in Cercopithecus aethiops and Macaca fascicularis monkeys with or without prior immunization with inactivated TBE vaccine. No visible clinical signs or severe pathomorphological lesions were observed in any monkey infected with TBEV or OHFV. C. aethiops challenged with OHFV showed massive hemolytic syndrome and thrombocytopenia. Infectious virus or viral RNA was revealed in visceral organs and CNS of C. aethiops infected with both viruses; however, viremia was low. Inactivated TBE vaccines induced high antibody titers against both viruses and expressed booster after challenge. The protective efficacy against TBE was shown by the absence of virus in spleen, lymph nodes and CNS of immunized animals after challenge. Despite the absence of expressed hemolytic syndrome in immunized C. aethiops TBE vaccine did not prevent the reproduction of OHFV in CNS and visceral organs. Subcutaneous inoculation of M. fascicularis with two TBEV strains led to a febrile disease with well expressed viremia, fever, and virus reproduction in spleen, lymph nodes and CNS. The optimal terms for estimation of the viral titers in CNS were defined as 8–16 days post infection. We characterized two animal models similar to humans in their susceptibility to tick-borne flaviviruses and found the most optimal scheme for evaluation of efficacy of preventive and therapeutic preparations. We also identified M. fascicularis to be more susceptible to TBEV than C. aethiops.

Recombinant domains III of Tick-Borne Encephalitis Virus envelope protein in combination with dextran and CpGs induce immune response and partial protectiveness against TBE virus infection in mice

“…PRNT50 was performed as described earlier [ 21 ]. Briefly, sequential dilutions of sera were prepared in 199 medium on Earle solution with addition of 2 % FBS (Gibco ThermoFisher Scientific, USA).…”

Lethal Experimental Tick-Borne Encephalitis Infection: Influence of Two Strains with Similar Virulence on the Immune Response

“…The 50% plaque reduction neutralization test (PRNT) was performed as described in Pripuzova et al (2013): serial 2-fold dilutions of serum were prepared in 0.2 ml volumes. Virus diluted to contain approximately 30–40 PFUs was then added at a volume of 0.2 ml to each serum dilution, and mixtures were incubated at 37°C for 1 h. Then, the virus–serum mixtures were inoculated into wells with PEK cell monolayer in a volume of 0.4 ml, and the cells were incubated for 1 h for adsorption of non-neutralized virus.…”

“…For antiviral Abs titration, ELISA was performed using the standard technique (Pripuzova et al, 2013) by the following scheme: 1st layer—non-inactivated virus antigen (Ag), 2nd layer—2-fold dilutions of the analyzed serum, 3rd layer—anti-mouse Abs (Anti-Mouse IgG IgA IgM (H+L) HRP-conjugated, Sigma-Aldrich).…”

Animal Models of Tick-Borne Hemorrhagic Fever Viruses

“…Neither AGM nor bonnet macaques infected with high dose of OHFV develop disease signs. Bonnet macaques do not display viremia or any pathologic manifestations while AGM support OHFV replication and may transiently display a hemolytic syndrome, accompanied with leukopenia, thrombocytopenic purpura and increases in serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) without other disease signs [ 16 , 20 ]. Therefore, the AGM model of OHF effectively mimics the mild to moderate disease symptoms of human OHF.…”