THE PROBLEM OF THE SIGNIFICANCE OF THE INCLUSION BODIES FOUND IN THE SALIVARY GLANDS OF INFANTS, AND THE OCCURRENCE OF INCLUSION BODIES IN THE SUBMAXILLARY GLANDS OF HAMSTERS, WHITE MICE, AND WILD RATS (PEIPING)

Persistent viral replication and the development of T-cell responses after intranasal infection by MCMV

Natural transmission of cytomegalovirus (CMV) has been difficult to observe. However, recent work using the mouse model of murine (M)CMV demonstrated that MCMV initially infects the nasal mucosa after transmission from mothers to pups. We found that intranasal (i.n.) inoculation of C57BL/6J mice resulted in reliable recovery of replicating virus from the nasal mucosa as assessed by plaque assay. After i.n. inoculation, CD8⁺ T-cell priming occurred in the mandibular, deep-cervical, and mediastinal lymph nodes within 3 days of infection. Although i.n. infection induced "memory inflation" of T cells specific for the M38_316-323 epitope, there were no detectable CD8⁺ T-cell responses against the late-appearing IE3_416-423 epitope, which contrasts with intraperitoneal (i.p.) infection. MCMV-specific T cells migrated into the nasal mucosa where they developed a tissue-resident memory (T_RM) phenotype and this could occur independently of local virus infection or antigen. Strikingly however, virus replication was poorly controlled in the nasal mucosa and MCMV was detectable by plaque assay for at least 4 months after primary infection, making the nasal mucosa a second site for MCMV persistence. Unlike in the salivary glands, the persistence of MCMV in the nasal mucosa was not modulated by IL-10. Taken together, our data characterize the development of local and systemic T-cell responses after intranasal infection by MCMV and define the nasal mucosa, a natural site of viral entry, as a novel site of viral persistence.

Encephalitis Caused by Murine Cytomegalovirus in Newborn and Weanling Mice

Lesions in mice inoculated intracerebrally with murine cytomegalovirus varied with age of the animals. Inoculation of suckling mice led to severe necrotizing encephalitis followed by cerebral malformation characterized by destruction of the sub-ventricular zone of the forebrain, areas of cerebral cortex and hippocampus. Symmetrical, mineralized, partially cavitated lesions developed in these areas as a sequel of infection. Infection of 3-week-old mice led to mild, nonsuppurative meningoencephalitis accompanied by ependymitis and focal ependymal denudation without apparent sequelae.

THE VISCERAL LESIONS PRODUCED IN MICE BY THE SALIVARY GLAND VIRUS OF MICE

Extensive visceral lesions containing intranuclear inclusions have been produced in mice by intraperitoneal and intracerebral inoculations of the homologous salivary gland virus. Rarely small pancreatic lesions containing inclusions have been encountered 2 weeks after subcutaneous inoculation. Many of the animals injected intraperitoneally died between the 4th and 7th day after inoculation. In spite of the extensive lesions produced in the liver and spleen, the virus could not be transferred with an emulsion of these organs.

A rat cytomegalovirus infection model as a tool for immunotoxicity testing

A rat cytomegalovirus infection model for use in immunotoxicity testing has been developed. In resistance against viruses, natural killer cells and cytotoxic T-cells play an important role. Therefore, this model complements other rat host resistance models for immunotoxicity testing, i.e. existing bacterial and parasitic infection models in which cytotoxic T-cells and natural killer cells play a minor role. Host resistance against cytomegalovirus infections in the rat was determined by titrating infectious virus levels in organs after cytomegalovirus infection in an in vitro infectivity test denoted as the Plaque Forming Unit (PFU) Test. In this test, homogenates of different organs were investigated for infectious virus titers on rat embryonic cell monolayers. We demonstrated that in the salivary gland, the major target organ for rat cytomegalovirus, virus was detectable from 8 days onward after intraperitoneal infection. To show that this model is suitable for the detection of immunotoxicity four different methods for immunosuppression were investigated: 1. gamma-irradiation, 2. congenitally athymic rats, 3. chemically induced immunosuppression, 4. ultraviolet-B (UVB) irradiation. Rat cytomegalovirus titers in the salivary glands of irradiated (500 rad 1 day prior to infection) or congenitally athymic rats were significantly increased as compared to non-irradiated rats and euthymic control rats respectively. In TOX-Wistar rats, given 20 or 80 mg bis(tri-n-butyltin)oxide (TBTO) per kg food beginning 6 weeks before cytomegalovirus infection, a regimen known to have immunotoxic effects, cytomegalovirus titers in the salivary glands were significantly increased as compared to non-TBTO-treated cytomegalovirus infected rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Spontaneous disseminated cytomegalic inclusion disease in an ageing laboratory mouse

An untreated C57BL/6NCrlBR male mouse in a life-long longevity study, killed in extremis at 761 days of age, had mild focal necrotic hepatitis and extensive focal necrotic adrenalitis. Characteristic cytomegalic cells bearing intranuclear and cytoplasmic inclusions and cytoplasmic vacuoles were seen in necrotic areas. Scattered intranuclear inclusions were also seen in the reticulum cells of the spleen and acinar epithelium of the submaxillary glands. We believe this to be the first report of spontaneous disseminated cytomegalic inclusion disease in aged mice.

The isolation and partial characterisation of a cytomegalovirus from the brown rat, Rattus norvegicus

This report describes the isolation and partial characterisation of a cytomegalovirus (CMV) from the wild brown rat (Rattus norvegicus). The isolate was sensitive to ether and heat treatment at 56 degrees C/30 minutes, and had a characteristic herpes virus morphology. In rat embryo fibroblast cells, new virus was detectable by 18 hours after inoculation. The cytopathic effect consisted of a focal rounding of cells which developed to involve the entire monolayer. Inoculation of newborn rats produced mortality of 67-75 per cent which was reduced to 33-46 per cent by intra-peritoneal inoculation or tissue culture passage. Highest virus concentrations were found in the liver and spleen 14 days after inoculation. The virus was also pathogenic (to a lesser extent) to newborn BALB/c mice. It was related to the Osborn strain of mouse CMV by fluorescent-antibody testing but distinct by the serum-neutralisation test.

ELECTRON MICROSCOPY OF SALIVARY GLAND VIRUSES

A human and a mouse strain of the salivary gland virus have been examined by electron microscopy. The human strain was transmitted, prior to examination, to tissue cultures derived from human myometrial cells, while the mouse strain was examined in mice inoculated intraperitoneally. The nuclear forms associated with both strains of virus were morphologically similar. Nuclear inclusions, composed of particles interspersed with dense clumped chromatin, were a striking feature of infected cells. The cytoplasmic forms were of 2 types-one a 300 to 500 mmicro homogeneous dense spherical form, and the other a target-like form composed of a central dense dot in a pale zone surrounded by a dense shell-the entire configuration measuring 100 to 180 mmicro. The target-like particle appeared to be identical in both strains. The spherical cytoplasmic forms in cells infected with the human strain appeared to be solid, while in cells infected with the mouse strain there was evidence of formation of target-like forms within the spheres. Possible mechanisms by which infection of the cell may occur, as well as possible mechanisms and sites of multiplication of virus, are discussed.

Inclusion disease in childhood

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FURTHER STUDIES ON THE SUBMAXILLARY GLAND VIRUSES OF RATS AND GUINEA PIGS

1. It has not been possible to increase the virulence of the submaxillary gland viruses of guinea pigs and rats, either by reducing the resistance of the animals by exposure to X-ray, or by the addition of testicular extract (Duran-Reynals factor). 2. In guinea pigs and wild rats with spontaneously infected submaxillary glands, the kidney has been found to contain the virus in the absence of demonstrable pathological changes. 3. Direct injection of these viruses into the kidney produces only mild, circumscribed lesions. 4. The viruses, following subcutaneous injection into white rats and guinea pigs, are widely distributed 2 weeks after injection. They are present in the submaxillary glands, cervical lymph nodes, kidney, and lung. They were not demonstrable at this time in the blood, liver, or spleen. 5. By the intratracheal injection of large doses of virus in guinea pigs and rats, an interstitial bronchopneumonia with thickening of the alveolar and bronchial walls and the presence of acidophilic inclusion bodies, can be produced. 6. No evidence was obtained to indicate that the multiplication of bacteria in the lung is greatly enhanced by the injection of these viruses.