IMMUNOHISTOCHEMICAL EVALUATION OF THE EXPRESSION OF GLUTAMATE AMMONIA LIGASE IN THE BRAIN OF RABIES AFFECTED DOGS
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Date
2023-03-23
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COLLEGE OF VETERINARY AND ANIMAL SCIENCES MANNUTHY, THRISSUR, KERALA VETERINARY AND ANIMAL SCIENCES UNIVERSITY
Abstract
The current research work was designed with the objective of studying immunohistochemical localisation of glutamate ammonia ligase (GLUL) protein in different anatomical sites of brain in canine rabies as well as the comparison of
immunohistochemical signals in furious and dumb forms of the disease along with gross and histopathological changes in rabid dog brains. The carcasses of 219 rabies suspected dogs that were brought to the Department of Veterinary
Pathology, CVAS, Mannuthy, for necropsy between January 2021 and August 2022 formed the source of the samples in this study. One hundred and thirty-threebrain samples tested positive for dFAT were further confirmed by employing
polymerase chain reaction targeting N gene of rabies which yielded amplicon size of 533bp. Gross, cytological and histopathological alterations in brain of rabies were recorded. Immunohistochemical staining revealed localisation of GLUL in
glial cells in different anatomical sites of brain with different staining intensity. Diffuse strong immunopositivity was noticed in the microglial cells, astrocytic end feet process and axonal fibres in cerebellum, hippocampus, brainstem and
cerebrum in furious form. Whereas weak immunopositivity was noticed in all the four parts of brain in dumb form. Comparison of immunofluorescence with clinical forms of rabies revealed that furious form exhibited higher grade of
fluorescence where as lower grade of fluorescence was noticed in dumb form. Further, in different clinical forms of rabies, immunohistochemical localisation of GLUL was compared with immunofluorescence of the viral antigen. In furious
form of rabies, immunofluorescence was higher and immunopositivity for GLUL was stronger. The dumb form, in contrast, demonstrated low immunofluorescence and weak immunopositivity. Immunofluorescence and immunopositivity were positively correlated in both furious and dumb form. However, the significant assosciation and correlation between immunofluorescence and immunopositivity were greater in hippocampus and cerebellum (p< 0.01) compared to brainstem and cerebrum (p>0.05).Mechanism by which GLUL is increased and decreased in furious and dumb form respectively was substantiated from the present study. It is postulated that increased levels of GLUL leads to excitotoxic conditions manifested as furious form and decreased levels of GLUL leads to neurodegenerative changes manifested as dumb form.