Chronic fatigue in children: clinical features, Epstein-Barr virus and human herpesvirus 6 serology and long term follow-up.

During a 2-year period, 23 patients (14 girls, 9 boys) with chronic fatigue were referred to the Pediatric Infectious Disease Clinic of a tertiary care center, representing 19% of all out-patients seen in that clinic during that time. The median age was 14 years and the median duration of symptoms before referral was 6 months; 65% had missed at least 2 weeks of school and 30% required a home tutor. There were few positive physical findings and no elevation of white blood cell count (median, 7000/mm3) or erythrocyte sedimentation rate (median, 5 mm/hour). Twenty-five percent had no evidence of Epstein-Barr virus infection, 15% had current or recent infection and 60% had past infection; 33% of the latter had detectable antibody to early antigen but the titers were low. Human herpesvirus 6 titers in 8 patients were similar to those in age- and sex-matched controls. Of 17 patients contacted after a median of 26 months, 76% reported definite improvement, although 38% of these still experienced occasional symptoms. In this referral population chronic fatigue was a common presenting complaint, was associated with marked degrees of dysfunction and bore no relationship to Epstein-Barr virus or human herpesvirus 6 infection. In most children the disorder was self-limited, although a minority were persistently or severely affected.

A review of the molecular mechanism of HSV-1 latency.

The neurotropic herpes viruses, as typified by herpes simplex virus type 1, are noted for their ability to form latent infections. The latent infection differs from the acute infection both in gene expression and the physical state of the viral genome. Latency can be divided into several stages--establishment, maintenance of reactivation--each of which are active areas of research. This review describes the molecular biology of HSV-1 latency and presents the current level of understanding of the molecular mechanism of HSV-1 latency.

Latent herpes simplex virus type 1 gene expression in ganglia innervating the human gastrointestinal tract.

Using in situ hybridization, we demonstrated that latent herpes simplex virus type 1 (HSV-1) gene expression is prevalent in human adult nodose ganglia. This suggests that infection of gastrointestinal sensory nerves, probably through swallowed virus-laden oral secretions, occurs commonly and that HSV-1 reactivating from this site may play a role in recurrent gastrointestinal disorders.

Oral inoculation with herpes simplex virus type 1 infects enteric neuron and mucosal nerve fibers within the gastrointestinal tract in mice.

Herpes simplex virus type 1 (HSV-1) is commonly encountered first during childhood as an oral infection. After this initial infection resolves, the virus remains in a latent form within innervating sensory ganglia for the life of the host. We have previously shown, using a murine model, that HSV-1 placed within the lumen of the esophagus gains access to nerves within the gut wall and establishes a latent infection in sensory ganglia (nodose ganglia) of the tenth cranial nerve (R. M. Gesser, T. Valyi-Nagy, S. M. Altschuler, and N. W. Fraser, J. Gen. Virol. 75:2379-2386, 1994). Peripheral processes of neurons in these ganglia travel through the vagus nerve and function as primary sensory receptors in most of the gastrointestinal tract, relaying information from the gut wall and mucosal surface to secondary neurons within the brain stem. In the work described here, we further examined the spread of HSV-1 through the enteric nervous system after oral inoculation. By immunohistochemistry, HSV-1 was found to infect myenteric ganglia in Auerbach's plexus between the inner and outer muscle layers of the gut wall, submucosal ganglia (Meisner's plexus), and periglandular ganglion plexuses surrounding submucosal glands. Virus-infected nerve fibers were also seen projecting through the mucosal layer to interact directly with surface epithelial cells. These intramucosal nerve fibers may be a conduit by which intraluminal virus is able to gain access to the enteric nervous system from the gastrointestinal lumen.

Restricted herpes simplex virus type 1 gene expression within sensory neurons in the absence of functional B and T lymphocytes.

Herpes simplex virus type I (HSV-1) establishes a latent infection in sensory ganglion neurons. During latency no viral-specific proteins are detected and virus gene expression is restricted to the latency-associated transcripts. We report here that trigeminal ganglia of mice with severe combined immunodeficiency contain individual sensory neurons exhibiting restricted viral gene expression characteristic of latency; this occurred during acute (4-6 days) infection with the wild-type HSV-1 strain 17+ and after prolonged (4 weeks) infection with the replication impaired HSV-1 mutant in 1814. These results indicate that T and B lymphocytes, while important for the recovery from viral infections, are not required for the establishment or maintenance of latency in neurons.

Upper airway obstruction in association with perinatally acquired herpes simplex virus infection.

Two cases of neonatal upper respiratory tract obstruction caused by herpes simplex virus are described. Infection of the upper respiratory tract with this virus should be included in the differential diagnosis of fever and stridor during the neonatal period.

Reactivation of herpes simplex virus from latently infected mice after administration of cadmium is mouse-strain-dependent.

It was previously reported that administration of cadmium (Cd) to CBA mice latently infected with herpes simplex virus (HSV) results in a high incidence of virus reactivation in vivo. In the present study, Cd-inducible reactivation was used to compare CBA with four other laboratory mouse strains. HSV reactivation, as measured by the recovery of infectious particles from latently infected trigeminal ganglia following Cd treatment, occurred predominantly in the CBA strain and was almost entirely absent from other strains tested. There was no correlation of strain-dependent Cd toxicity with the recovery of infectious virus. In situ examination of Cd-treated ganglia from latently infected CBA and BALB/c mice revealed that viral antigens were expressed exclusively in CBA specimens, but that viral replicative transcripts were expressed in both strains, although more strongly in CBA than in BALB/c specimens. We conclude that Cd treatment had induced reactivation of HSV from both mouse strains, and that the reactivation process was completed in CBA but not in BALB/c mice.

Oral-oesophageal inoculation of mice with herpes simplex virus type 1 causes latent infection of the vagal sensory ganglia (nodose ganglia).

Herpes simplex virus type 1 (HSV-1) gingivostomatitis during childhood is known to result in a latent infection of the trigeminal ganglion neurons, which innervate the oral mucosa. During latency the viral genome is maintained in a non-infectious state. However, stimuli such as stress, fever or localized trauma can cause HSV-1 to reactivate in neurons and produce recrudescent disease in the peripheral tissues. Recently, HSV-1 proteins and nucleic acids have been detected in biopsies from human duodenal and gastric ulcers, raising the possibility that HSV-1 latency within the enteric nervous system is involved in this chronic recurrent gastrointestinal disorder. The studies in mice described here were done to determine whether HSV-1 latency could be established in neurons that innervate the murine gut. We found that after either intraperitoneal or oral-oesophageal inoculation of mice, HSV-1 establishes a latent infection in nodose ganglia of the vagus nerve, whose sensory neurons project to the gastrointestinal tract. This animal model of HSV-1 latency in the vagal sensory ganglia will be useful to examine the possible relationship between HSV-1 and recurrent gastrointestinal disease.

Oral inoculation of SCID mice with an attenuated herpes simplex virus-1 strain causes persistent enteric nervous system infection and gastric ulcers without direct mucosal infection.

BACKGROUND: After placement of herpes simplex virus type 1 (HSV-1) into the esophageal lumen of BALB/c mice, the virus replicated in enteric neurons within the esophagus and stomach and was transported to the sensory ganglia of the vagus nerve (nodose ganglia), where viral replication also occurs and where ultimately a long term latent infection is established. This described infection of immunocompetent mice primarily involved neuronal cells and associated satellite cells. EXPERIMENTAL DESIGN: Severe combined immunodeficient (SCID) mice were orally infected with an attenuated strain of HSV-1 to better identify sites of viral involvement in the gastrointestinal tract, particularly the mucosa. RESULTS: Three to five weeks after oral inoculation of SCID mice with HSV-1 strain in1814, a persistent viral infection of the gastrointestinal tract was established in most of the mice. Extensive viral replication was detected by immunohistochemistry throughout pathways of the vagus nerve and within the intrinsic enteric nervous system. Despite this ultimately fatal infection, viral replication in the gut occurred almost exclusively in enteric neurons and their processes; viral proteins were occasionally seen in smooth muscle cells immediately adjacent to heavily infected enteric ganglia. More than 50% of these persistently infected mice, when killed 18 to 31 days postinoculation, had gastric ulcers that were identified grossly and histologically. Only one of the 40 gastric ulcers was found to contain viral Ag. The remaining ulcers, although devoid of viral proteins, were found adjacent to virus-infected ganglia. CONCLUSIONS: HSV-1 can enter enteric neurons with minimal initial mucosal involvement, and once inside the nervous system, the virus is contained there despite the absence of a specific host immune response. Furthermore, chronically infected enteric neurons may provide an indirect mechanism for the pathogenesis of gastric ulcers in these immune-deficient mice.

The herpes simplex virus type 1 strain 17+ gamma 34.5 deletion mutant 1716 is avirulent in SCID mice.

Laboratory animal models are important tools for the identification of avirulent herpes simplex virus type 1 (HSV-1) strains which have potential for use in humans as vaccine strains or gene therapy vectors. We have studied an HSV-1 17+ variant, 1716, that has a deletion in the gamma 34.5 gene and which replicates poorly in the footpads of mice and is unable to grow in the mouse central nervous system or dorsal root ganglia (DRG) of the peripheral nervous system following peripheral inoculation. However, 1716 is known to be capable of establishing latent infections in the DRG of mice. Here we show that 1716 is avirulent after ocular infection and has low virulence after intracranial inoculation in SCID mice. Since SCID mice are much more sensitive to HSV-1 infection than immunocompetent mice, our results clearly demonstrate the drastically reduced virulence of the variant 1716 and provide additional support for the hypothesis that this variant would be avirulent in humans.