Estudos dos mecanismos associados às alterações clinicopatológicas, parâmetros imunes e aspectos neuroquímicos na infecção por Herpesvírus Bovino 5 (BoHV-5) no modelo murino

Abstract

Meningoencephalitis caused by bovine Herpesvirus type 5 (BoHV-5) is a disease with high lethality in cattle, non-specific treatment and non-specific vaccine for the pathogen. Animals up to two years of age are more affected, with less predominance in adult cattle, cause economic impacts and are present mainly in the countries of South America. Studies involving this pathogenesis in murine models are scarce. Our main objective was to characterize the clinicopathological changes, immune and neurochemical profiles in C57BL/6 mice infected with BoHV-5. We also evaluated the participation of TLRs 3/7/9 during intracranial infection by BoHV-5, using the Mutum sample. Our results demonstrated that after three days of infection, animals infected with 107 TCID50 of BoHV-5 showed clinical signs associated with different degrees of meningoencephalitis, characterized by formation of perivascular cuffs, reactive gliosis and hemorrhagic foci at different regions of the brain. Furthermore, higher immunoexpression for GFAP and Iba-1 was observed in the central nervous system of infected animals. Immunopositive cells for cleaved caspase-3 have been observed around some blood vessels in the brain of infected mice. Brain levels of brain-derived neurotrophic factor (BDNF), neural growth factor (NGF) and glial-derived neurotrophic factor (GDNF) and fractalkine protein (CX3CL1) were analyzed by ELISA. The infected mice showed lower concentrations of the neurotrophic factor BDNF, greater expression of the cytokines and chemokines IL-12p70, TNF, IL-10, IFN-γ, IL-6 and CCL-2 and we did not find differences in the levels of expression of fractalkine between animals infected and uninfected. Using the RT-qPCR technique, we evaluated the expression of eighty-four genes related to innate and adaptive immune responses in infection caused by BoHV-5 in mice. As a result, we obtained 23 genes related to the innate, adaptive and standard recognition receptors more expressed in infected mice, compared to mock mice. In addition, the participation of Toll like receptors (TLRs) 3, 7, 9 after infection with 104 TCDI50 of BoHV-5 in C57BL/ 6 mice was evaluated. The infection promoted significant weight loss until the third day in both groups of wild type and TLR3/7/9-/- deficient animals, with no statistical difference between infected wild animals and TLR3/7/9-/-. Both infected wild-type and TLR3/7/9 deficient animals had similar frequency of clinical signs, degrees of meningitis and a significant decrease of BDNF, suggesting that other via could activate the immune responses to BoHV-5 infection in C57BL/ 6 mice. BDNF may be involved with anti-apoptotic and neuroprotective effects during infection and post-infection tissue damage may be related to intense brain inflammation, microgliosis and astrocytosis. The chemokines and cytokines IL-12p70, TNF, IL-10, IFN-γ, IL-6 and CCL-2 proved to be important in neuropathology, as well as the trigger caused by inflammation-associated genes demonstrated in the present study.