GABA treatment reduces pneumonitis and viral load in MHV-1-infected mice: (A) GABA treatment reduces lung coefficient index. Mice were inoculated with MHV-1 and placed on plain water (control) or water containing GABA (20 mg/mL) immediately (GABA0) or 3 days post-infection (GABA3). The lungs were harvested and weighed when an animal became moribund or at 14 days post-infection. Data shown are the mean lung coefficient index ± SEM for each group from two separate studies. *** p < 0.001 and ** p < 0.01 for GABA0 and GABA3 (respectively) vs. control water-treated group by Student’s t-test; (B,C) Histopathological features in the lungs of untreated and GABA-treated mice at 6 days post-MHV-1 infection. Representative images of H&E-stained lung sections (magnification ×200) from (B) untreated mice and (C) GABA-treated (beginning immediately following inoculation) mice. Red arrows point to hyaline-like membranes and black arrows indicate local consolidation. The scale bar is 50 µm; (D) Quantitative analysis of the degrees of pneumonitis in the lungs based on the number of hyaline-like membranes, % of pulmonary areas with obvious inflammatory infiltrates in lung parenchyma, and the % of area with inflammatory consolidation (as described in Materials and Methods). Data are expressed as the mean pneumonitis score ± SEM of each group (n = 5 mice per group per time point in two independent experiments); (E) Kinetics of MHV-1 replication in the lungs. Mice were inoculated with MHV-1 and immediately placed on plain water (control) or water containing GABA (20 mg/mL) and 3 or 6 days later, their lungs were harvested for determination of viral load. Concurrently, another group of MHV-1-inoculated mice was given water containing GABA (20 mg/mL) beginning 3 days post-infection, and the viral load in their lungs was determined 6 days post-infection. The data shown are the mean TCID50/g of lung tissue ± SEM at the indicated days. GABA0 mice (blue square symbol) received GABA immediately after inoculation and GABA3 mice (orange triangle symbol) received GABA beginning 3 days post-infection. n = 5 mice per group at each time point. * p < 0.05 by Student’s t-test.