HSV-1 Lacking the Beclin-Binding Domain (BBD) of ICP34.5 Does Not Induce Retinitis in the Injected Eye Following Anterior Chamber (AC) Inoculation

Abstract

Purpose: : The autophagy response induced by HSV-1 infection is antagonized by the neurovirulence gene product, ICP34.5, which binds to the essential autophagy protein Beclin1 (Atg6) via the Beclin-binding domain (BBD). The purpose of this study was to determine if lack of the BBD affects viral spread and ocular infection.

Methods: : Female BALB/c mice were injected with 1 x 10⁴ PFU of BBD-deficient HSV-1 (Δ68H) or its marker-rescued counterpart (Δ68HR) via the AC route. Ipsilateral eyes, contralateral eyes and brains were collected at several times p.i., examined by plaque assay for replicating virus, real time RT-PCR for T cell and B cell activation genes and interferon response genes, and by H and E and HSV-1 staining for morphology and location of HSV-1 infected cells, respectively.

Results: : In injected eyes, Δ68H replicated equivalently to Δ68HR at day 1 or 2 p.i. However, by day 3 p.i., significantly more replicating virus was recovered from Δ68HR infected injected eyes than from Δ68H injected eyes. In Δ68HR infected mice, the entire retina of the injected eye was infected and necrotic retinitis was seen. In contrast, widespread HSV-1 infection and retinitis were not observed in the retina of Δ68H-injected eyes. Both strains of HSV-1 spread to the brain by day 3 p.i.; however, CNS infection and encephalitis were more severe in Δ68HR infected mice. In the retina of the uninoculated contralateral eye, many HSV-1+ cells and retinitis were detected in both Δ68H and Δ68HR infected mice beginning on day 6 p.i. and virus titers in the uninoculated eye were similar for both groups. In Δ68H injected eyes, real time PCR for T cell and B cell activation genes revealed that IFN-γ, Cd40lg, Cd8b1, Cd3g, Tnfsf14, Cxcr5, IL10 and Nos2 were upregulated (≥3 fold) compared with Δ68HR injected eyes while type 1 interferon mRNA was lower in Δ68H injected eyes.

Conclusions: : Since infection in the retina of the injected eye and in the brain was less severe in Δ68H infected mice, these observations suggest that autophagy plays a role in controlling HSV-1 infection perhaps by more rapid induction of the adaptive immune response.

Keywords: herpes simplex virus • retinitis • pathology: experimental