Elevated TNF- and Soluble TNF Receptor in Degeneration Susceptible Mice with Experimental Coronavirus Retinopathy

Abstract

Abstract: : Purpose: Experimental coronavirus retinopathy (ECOR) is a retinal degeneration model system that is triggered by a virus and is composed of a genetic and autoimmune component. Increasing evidence suggests that TNF family members play a crucial role in immune-mediated disease processes. Therefore, we compared the levels of TNF-α and soluble TNF-α receptors (sTNFRs) in BALB/c (retinal degeneration susceptible) and CD-1 (retinal degeneration resistant) mice after viral infection. Methods: Mice were injected intravitreally with 5 µl of media (mock-injected) or media with MHV, strain JHM, at a concentration of approximately 1.35 x 10⁶ pfu/ml (virus-injected). Eyes and serum were collected at various time points after inoculation. Eyes were dissected and retinas removed for mRNA isolation followed by RT-PCR for TNF-α. Serum was assayed for the presence of TNF-α and TNF-α receptors by ELISA. Results: During the acute phase of infection (day 4) TNF-α mRNA was detected at higher levels within the retinas of degeneration susceptible BALB/c mice than in non-susceptible CD-1 mice. The serum concentration of TNF-α protein was significantly increased in virus-injected (p<0.005) compared to mock-injected BALB/c mice. In contrast, serum concentrations of TNF-α were not significantly different between virus-injected and mock-injected CD-1 mice. Moreover, sera from 100% of infected BALB/c mice contained TNF-α protein compared to just 25% of the CD-1 mice. In virus-injected BALB/c mice, serum concentrations of sTNFR1 were also elevated significantly compared to mock-injected mice (p< 0.0005). In virus-injected CD-1 mice sTNFR1 was not elevated. While concentrations of sTNFR2 were elevated in both BALB/c (p< 0.00005) and CD-1 (p< 0.005) infected mice compared to their mock-injected controls early in infection (day 4), concentrations of sTNFR2 were significantly higher in infected BALB/c as compared to CD-1 mice (p< 0.0005). Conclusions: These studies demonstrate that TNF-α and sTNFRs are elevated in virus-infected retinal degeneration susceptible BALB/c mice and that these molecules may participate in retinal degenerative processes.

Keywords: cytokines/chemokines • retina • autoimmune disease