New Approach for Untangling the Role of Uncommon Calcium-Binding Proteins in the Central Nervous System

Rabies virus infection is associated with variations in calbindin D-28K and calretinin mRNA expression levels in mouse brain tissue

Rabies virus (RABV) infection leads to a fatal neurological outcome in humans and animals and is associated with major alterations in cellular gene expression. In this study, we describe the effects of RABV infection on the mRNA expression levels of two genes, encoding the Ca²⁺-binding proteins (Ca-BPs) calbindin D-28K (Calb1) and calretinin (Calb2), in the brains of BALB/c mice. Sixty 4-week-old mice were divided into two test groups and one control group. Mice were inoculated intramuscularly with either a street rabies virus (SRV) strain or a challenge virus standard (CVS-11) strain and sacrificed at 3-day intervals up to day 18 postinfection. A direct fluorescent antibody test (DFAT) was used to verify the presence of RABV antigen in brain tissues, and real-time quantitative PCR (RT-PCR) was used to assess gene expression. Infection with both RABV strains resulted in significant (p < 0.05) increases in Calb1 and Calb2 expression in the test animals when compared with the controls at various time points in the study. Correlation analysis indicated very weak insignificant (p > 0.05) negative and positive relationships, respectively, between Calb1 expression (r = -0.04) and Calb2 expression (r = 0.08) with viral load (CVS-11 strain). Insignificant (p > 0.05) relationships were also observed Calb1 expression (r = -0.28) and Calb2 expression (r = 0.06) and viral load for the SRV strain.The observed alterations in Calb1 and Calb2 expression in this study indicate possible impairments in neuronal Ca²⁺ buffering and Ca²⁺ homeostasis as a result of RABV infection and, consequently, possible involvement of calbindin-D28K and calretinin in the neuropathogenesis of rabies.