Electron microscope observations on tubular structures in cells infected with herpes simplex virus type 2

In Vitro Replication of Chelonid Herpesvirus 5 in Organotypic Skin Cultures from Hawaiian Green Turtles (Chelonia mydas)

Fibropapillomatosis (FP) is a tumor disease of marine turtles associated with chelonid herpesvirus 5 (ChHV5), which has historically been refractory to growth in tissue culture. Here we show, for the first time, de novo formation of ChHV5-positive intranuclear inclusions in cultured green turtle cells, which is indicative of active lytic replication of the virus. The minimal requirements to achieve lytic replication in cultured cells included (i) either in vitro cultures of ChHV5-positive tumor biopsy specimens (plugs) or organotypic cultures (rafts) consisting of ChHV5-positive turtle fibroblasts in collagen rafts seeded with turtle keratinocytes and (ii) keratinocyte maturation induced by raising raft or biopsy cultures to the air-liquid interface. Virus growth was confirmed by detailed electron microscopic studies that revealed intranuclear sun-shaped capsid factories, tubules, various stages of capsid formation, nuclear export by budding into the perinuclear space, tegument formation, and envelopment to complete de novo virus production. Membrane synthesis was also observed as a sign of active viral replication. Interestingly, cytoplasmic particles became associated with keratin filaments, a feature not seen in conventional monolayer cell cultures, in which most studies of herpesvirus replication have been performed. Our findings draw a rich and realistic picture of ChHV5 replication in cells derived from its natural host and may be crucial not only to better understand ChHV5 circulation but also to eventually complete Koch's postulates for FP. Moreover, the principles described here may serve as a model for culture of other viruses that are resistant to replication in conventional cell culture.IMPORTANCE A major challenge in virology is the study of viruses that cannot be grown in the laboratory. One example is chelonid herpesvirus 5 (ChHV5), which is associated with fibropapillomatosis, a globally distributed, debilitating, and fatal tumor disease of endangered marine turtles. Pathological examination shows that ChHV5 is shed in skin. Here we show that ChHV5 will grow in vitro if we replicate the complex three-dimensional structure of turtle skin. Moreover, lytic virus growth requires a close interplay between fibroblasts and keratinocytes. Finally, the morphogenesis of herpesviral growth in three-dimensional cultures reveals a far richer, and likely more realistic, array of capsid morphologies than that encountered in traditional monolayer cell cultures. Our findings have applications to other viruses, including those of humans.

Efficacy of oral administration of live herpes simplex virus type 1 as a vaccine

Mice given herpes simplex virus type 1 (HSV-1) (Miyama +GC strain) intragastrically via a stainless-steel cannula were rendered immune to subsequent lethal intraperitoneal (i.p.) challenge with HSV-1. The orally administered HSV-1 was completely inactivated in the stomach within a few minutes of inoculation. However, systemic immunity was established 14 days after oral inoculation with the virus and retained for up to 6 months. The mechanisms of establishing systemic immunity were investigated by means of adoptive transfer comparisons. When splenic cells from HSV-1-immunized mice were transplanted into nonimmunized mice, all of the recipient mice survived after a lethal i.p. challenge with the virus. Immunity was not established in antithymocyte serum-treated mice or by transfer of serum from immunized to nonimmunized mice. In addition, all HSV-1-immunized mice died after lethal challenge with HSV-2 and influenza virus A. These findings suggest that the immunity was virus specific, with T lymphocytes playing a major role in its establishment. The present study therefore supports the possibility of oral immunization with live HSV-1 as a vaccine.

Two cases of necrotizing myelopathy associated with malignancy caused by herpes simplex virus type 2

Two cases of necrotizing myelopathy were autopsied; one was complicated with lung carcinoma and the other with chronic type adult T cell leukemia (ATL leukemia). To our knowledge, they were the first cases of their type in Japan. In both cases, necrosis of the spinal cord was observed in the gray and white matter along most of its extent. Marked changes were found in the lumbar segment. The patients were not treated with intravenous cancer chemotherapy or irradiation. Immunohistochemical and electron microscopic examination revealed an extremely strong infection of herpes simplex virus (HSV) type 2. However, HSV type 1 and cytomegalovirus antigens were not detected.

Filamentous structures associated with Epstein-Barr virus-infected cells

After the onset of Epstein-Barr virus DNA and protein synthesis 10 h after superinfection of Raji cells (a cell line containing Epstein-Barr virus DNA but not producing virus), filamentous structures 25 nm in diameter and 0.2 to 1.4 micrometers in length could be detected in the cell cytoplasm by electron microscopy. These structures banded in metrizamide gradients with viral DNA and proteins, but at a density different from that of virions or nucleocapsids. These filaments, enriched in a 155,000-dalton protein similar in size to a major nucleocapsid protein of Epstein-Barr virus, may represent intermediates in viral nucleocapsid assembly.

Non-inflammatory herpes simplex hepatitis in an adult with chronic neutropenia

We report the case of a young woman with chronic neutropenia, in whom hepatitis, extensive herpetic eruption and herpes simplex viremia developed after genital herpetic ulceration. Although severe liver necrosis was present, the patient's death did not result from hepatic failure. No inflammatory cell infiltration was found circumscribing the multiple necrotic foci in the liver. This absence of inflammatory cell infiltration reflects the host's inability to normally restrain herpes simplex virus dissemination and, in this patient, might be the consequence of chronic neutropenia.

Tubular structures in the cervix of mice experimentally infected with herpes simplex virus type 2

Experimental infection of the C3H/N mouse genital tract was demonstrated after intravaginal inoculation with herpes simplex virus type 2 (HSV-2). About 75% of the infected animals died by Day 7, and 75% of the surviving animals had severe vaginitis or neurological signs on Day 7. Titers of the virus recovered from vaginal secretions of infected animals reached a maximum on Day 2 and gradually decreased until Day 7. On the other hand, under the electron microscope, virus particles and tubular structures could be found in the nuclei of infected cells of the cervix in the 1st, 2nd and 4th days after infection. All cases in which virus particles could be found in the nuclei of infected cells were also positive for tubular structures and vice versa. These observations indicate that in situ diagnosis of HSV-2 infection can be made in the mouse model. The same method would be applicable for the diagnosis of human HSV-2 infection.

Herpes simplex virus (HSV) infection of organotypic nerve cell cultures. Tubule-like structures in the nuclei of cells infected with type 2 but not with type 1 virus

In HSV-2 infected cultures, intranuclear tubule-like structures were found more commonly in fibroblasts and central nervous system (CNS) neurons than in oligodendrocytes, astrocytes, satellite and Schwann cells, but were found least often in peripheral neurons.

Effects of antimetabolites on the production of tubular structures in Vero cells infected with herpes simplex virus type 2

Treatment of Vero cells infected with herpes simplex virus type 2 with the proper concentrations of hydroxyurea (HU) reduced the production of infectious virus and markedly increased the accumulation of tubular structures in the nuclei when the drug was added within 6 hours after infection. Similar accumulation of tubular structures in the infected nuclei was also observed when infected cells were treated with phosphonoacetic acid at proper concentrations. The release of HU-treated, herpes simplex virus type 2-infected cells from the drug-induced blocking of synthesis of infectious virus resulted in the marked decrease of tubular structures coincidentally with the beginning of production of infectious virus. The data suggest the possibility that the disappearance of tubular structures may be related to the active production of infectious virus.