HSV-1 infection and pathogenesis in the tree shrew eye following corneal inoculation.

Herpes simplex virus type I (HSV-1) infection causes inflammation in the cornea known as herpes simplex virus keratitis (HSK), a common but serious corneal disease. It is not entirely clear whether the virus during recurring infection comes from the trigeminal ganglia or the eye tissue, including the retina and ciliary ganglion. Because the tree shrew is closely related to primates and tree shrew eye anatomic structures are similar to humans, we studied HSV-1 corneal infection in the tree shrew. We found that HSK symptoms closely mimic those found in human HSK showing typical punctiform and dendritic viral keratitis during the acute infection period. Following the HSV-specific lesions, complications such as stromal scarring, corneal thickening (primary infection), opacity, and neovascularization were observed. In the tree shrew model, following ocular inoculation, the cornea becomes infected, and viral protein can be detected using anti-HSV-1 antibodies in the epithelial layer and retina neuronal ganglion cells. The HSV-1 transcripts, ICP0, ICP4, and LAT can be detected at 3 days post-infection (dpi), peaking at 5 dpi. After 2 weeks, ICP4 and ICP0 transcripts are reduced to a basal level, but the Latency Associated Transcripts (LATs) continue to accumulate. Interestingly, after the acute infection, we still detected abundant active HSV-1 in tree shrew eyes. Further, we found HSV-1 persistent in the ciliary ganglion and cornea. These findings are discussed in support of the tree shrew as a non-human primate HSK model, which could be useful for mechanistic studies of HSK.

Virus- and interferon-induced loss of inhibitory M2 muscarinic receptor function and gene expression in cultured airway parasympathetic neurons.

Viral infections increase vagally mediated reflex bronchoconstriction. Decreased function of inhibitory M2 muscarinic receptors on the parasympathetic nerve endings is likely to contribute to increased acetylcholine release. In this study, we used cultured airway parasympathetic neurons to determine the effects of parainfluenza virus and of interferon (IFN)-gamma on acetylcholine release, inhibitory M2 receptor function, and M2 receptor gene expression. In control cultures, electrically stimulated acetylcholine release increased when the inhibitory M2 receptors were blocked using atropine (10(-)5 M) and decreased when these receptors were stimulated using methacholine (10(-)5 M). Acetylcholine release was increased by viral infection and by treatment with IFN-gamma (300 U/ml). In these cells, atropine did not further potentiate, nor did methacholine inhibit, acetylcholine release, suggesting decreased inhibitory M2 receptor function and/or expression. Using a competitive reverse transcription-polymerase chain reaction method, we demonstrated that M2 receptor gene expression was decreased by more that an order of magnitude both by virus infection and by treatment with IFN. Thus, viral infections may increase vagally mediated bronchoconstriction both by directly inhibiting M2 receptor gene expression and by causing release of IFN-gamma which inhibits M2 receptor gene expression.

Detection of herpes simplex virus type 1 in human ciliary ganglia.

PURPOSE: To determine whether herpes simplex virus type 1 (HSV-1) DNA is present in the ciliary ganglion (CG). METHODS: Fifty CG and 47 trigeminal ganglia (TG) were resected from 63 formalin-fixed cadavers between 56 and 98 years of age that had been embalmed within 12 hours of death. The donors had no known active HSV infection at the time of death. DNA was extracted from all ganglia by proteinase-K digestion (TG) or digestion by a mild lysis buffer (CG). DNA was amplified by polymerase chain reaction for sequences from human chromosome 18, D18S1259 (positive control), and from the HSV-1 DNA polymerase gene, U(L)30. The amplified DNA was separated by agarose gel electrophoresis, transferred to nylon membranes, and hybridized with the appropriate digoxigenin-labeled probe that was detected by alkaline phosphatase-conjugated monoclonal antibody. RESULTS: The D18S1259 sequence was amplified from 47 TG and 30 CG samples. Of these samples, 32 (68.0%) of the 47 TG samples and 20 (66.6%) of the 30 CG samples were positive for the UL(30) HSV-1 sequence. CONCLUSIONS: Using amplification of HSV-1 DNA as a surrogate marker of latency, the finding that the frequency of HSV-1 in the CG was approximately the same as that of the TG suggests that the CG may be an additional site of HSV-1 latency in humans. Active infection in or reactivation of HSV-1 from non-TG sites may explain why this virus is able to infect sites, such as the retina, that have no direct connections to the trigeminal nerve.

Central neuronal circuit innervating the rat heart defined by transneuronal transport of pseudorabies virus.

We defined the central circuit innervating various regions of the rat heart using a neurotropic herpesvirus as a transneuronal tracer. Location of viral antigens in the brain after cardiac injection of three strains of pseudorabies virus (PRV) provided insight into vagal preganglionic neurons and their connected interneurons. At short survival times, labeled vagal preganglionic neurons were localized in both the nucleus ambiguus (NA) and the dorsal motor nucleus of the vagus (DMV), and in an arc-like band through the reticular formation between the NA and the DMV. The amount of DMV labeling was dependent on viral strain. Similar distributions of labeled neurons were observed following either ganglionic, sinoatrial node, or ventricular injections. At intermediate survival times postcardiac injection, the virus replicated in vagal preganglionic neurons and was trans-synaptically transported to interneurons observed primarily in the NA regions and in an arc-like band through the reticular formation. Labeled neurons were also observed in ventral regions of the nucleus of the solitary tract (NTS). At longer survival times, labeled neurons were found in various regions of the NTS with the most abundant label dorsal and dorsomedial to the solitary tract. Abundant neuronal labeling was also found in the intermediolateral cell column, the raphe nuclei, the caudal and rostral ventral lateral medulla, the A5 region, the locus coeruleus, and the lateral and paraventricular hypothalamic nuclei. These data define the central circuits including the interneuronal connections that innervate various cardiac targets.