Interaction of immune and central nervous systems: contribution of anti-viral Thy-1+ cells to demyelination induced by coronavirus JHM.

The murine coronavirus JHM (JHMV or MHV-4) has been intensively studied as an experimental model of viral-induced demyelination; nonetheless, the degree to which demyelination results from direct viral cytolysis of oligodendroglia or immunological mechanisms remains controversial. To examine the contribution of immunity to the pathogenesis of JHMV in the central nervous system (CNS), mice were exposed to immunosuppressive doses of x-irradiation 3 days post infection and observed for clinical and pathological evidence of acute and subacute demyelination. Irradiated mice were found to have a nearly thousand-fold increase in central nervous system virus titer, as well as the presence of both abundant virus and viral antigen in white matter cells with the morphological characteristics of oligodendrocytes. Nonetheless, infected, irradiated mice had little or no evidence of demyelination or destruction of CNS cells. Adoptive transfers of spleen cells from syngeneic JHMV-immunized donors into irradiated JHMV-infected mice were carried out in order to determine the effect of immune reconstitution on pathogenesis. Splenocytes from JHMV-immune donors, but not naive donors or donors immunized with irrelevant antigen, completely restored demyelination in irradiated, JHMV-infected recipients. Depletion of Thy-1+ cells by treatment with monoclonal antibody and complement abolished the ability to transfer demyelination. We conclude that: 1) JHMV infection of the CNS does not result in acute or subacute demyelination in the absence of an intact immune response, and 2) viral-specific Thy-1+ cells are an essential element in the induction of demyelinating CNS lesions that result from JHMV infection.

Psychological stress and susceptibility to the common cold.

BACKGROUND: It is not known whether psychological stress suppresses host resistance to infection. To investigate this issue, we prospectively studied the relation between psychological stress and the frequency of documented clinical colds among subjects intentionally exposed to respiratory viruses. METHODS: After completing questionnaires assessing degrees of psychological stress, 394 healthy subjects were given nasal drops containing one of five respiratory viruses (rhinovirus type 2, 9, or 14, respiratory syncytial virus, or coronavirus type 229E), and an additional 26 were given saline nasal drops. The subjects were then quarantined and monitored for the development of evidence of infection and symptoms. Clinical colds were defined as clinical symptoms in the presence of an infection verified by the isolation of virus or by an increase in the virus-specific antibody titer. RESULTS: The rates of both respiratory infection (P less than 0.005) and clinical colds (P less than 0.02) increased in a dose-response manner with increases in the degree of psychological stress. Infection rates ranged from approximately 74 percent to approximately 90 percent, according to levels of psychological stress, and the incidence of clinical colds ranged from approximately 27 percent to 47 percent. These effects were not altered when we controlled for age, sex, education, allergic status, weight, the season, the number of subjects housed together, the infectious status of subjects sharing the same housing, and virus-specific antibody status at base line (before challenge). Moreover, the associations observed were similar for all five challenge viruses. Several potential stress-illness mediators, including smoking, alcohol consumption, exercise, diet, quality of sleep, white-cell counts, and total immunoglobulin levels, did not explain the association between stress and illness. Similarly, controls for personality variables (self-esteem, personal control, and introversion-extraversion) failed to alter our findings. CONCLUSIONS: Psychological stress was associated in a dose-response manner with an increased risk of acute infectious respiratory illness, and this risk was attributable to increased rates of infection rather than to an increased frequency of symptoms after infection.

Light intensity-associated eye lesions of Fischer 344 rats in long-term studies.

Albino rats and mice are sensitive to light and the recommended illumination of animal rooms (75-125 ft-candles) is known to cause retinal damage. When a room is illuminated by ceiling lights, animals in the cages of the top row and, to some extent, in the side columns of cage racks will be exposed to higher light intensity than those in the other cages of the rack. In 2-yr chemical carcinogenicity studies of the National Toxicology Program (previously the Carcinogenicity Bioassay Program of the National Cancer Institute), Fischer 344 rats were group-housed in hanging drawer-type clear polycarbonate cages. During the course of the chronic studies, a number of rats developed opacity of the eye. Ocular examination indicated chronic uveitis, deep interstitial keratitis, cataract formation leading to panophthalmitis, and in severe cases, phthisis bulbi. Histologic examination showed cataract and retinal degeneration. Incidences of these lesions were highest (greater than 55%) in the rats of the top rows and lowest in those of the bottom rows (less than 10%) of cages with no relation to chemical treatment, indicating an association with light intensity. The incidence of these eye lesions was markedly decreased (less than 15%) by decreasing the light intensity of the animal room to less than 50 ft-candles at 5 ft from the floor and rotating the cages in each column of a rack from top to bottom when cages or racks were changed.

Experimental Parker's coronavirus infection in Wistar rats.

Specific Pathogen Free (SPF) male Wistar rats were inoculated intranasally with Parker's rat coronavirus (PRC), then killed at various intervals post-inoculation (pi). PRC inoculated rats had transient respiratory signs. Intermandibular swelling was evident in some rats at 6-8 days pi. During the acute stages of the disease, inflammatory lesions were present in the respiratory tract and in the salivary and lacrimal glands. Regenerative lesions were observed in the salivary and lacrimal glands at 2 weeks pi. Inoculated rats seroconverted at 8-14 days pi, and significant coronaviral antibody titers were present in inoculated rats examined at 21 days pi with PRC. Changes in the respiratory tract and salivary and lacrimal glands were identical in incidence, distribution and nature to those observed in sialodacryoadenitis (SDA) virus inoculated Wistar rats. Thus, in the absence of viral isolation and characterization, "rat coronavirus infection" is a more appropriate term than either PRC infection or sialodacryoadenitis (SDA).

Pathogenesis of H13 nephropathogenic infectious bronchitis virus.

A nephropathogenic Massachusetts strain of infectious bronchitis virus (IBV) designated H13-IBV was isolated from the kidneys of commercial broilers. H13-IBV caused respiratory distress, depression, and diarrhea in specific-pathogen-free chickens. Gross renal lesions included pale coloration, swelling, and urate deposition. Histologic renal changes were interstitial mononuclear cell infiltration and degeneration and necrosis of tubular epithelial cells. Lesions in respiratory tissues included thickening and edema of the air sacs, congestion of the tracheal mucosa, and frothy serous exudate. Histologic tracheal lesions were deciliation, mucous gland distortion, inflammatory cell infiltration, and squamous metaplasia. Clinically, H13-IBV was highly pathogenic in birds infected at 1 day of age and mildly pathogenic in birds infected at 4 weeks of age. Kidney lesions were of marked severity only in birds infected at 1 day of age. Tracheal lesions were similar in severity in both age groups.

[The frequency and pathogenesis of feline infectious peritonitis (FIP)]. / Untersuchungen zur Häufigkeit und zur Pathogenese der Felinen Infektiösen Peritonitis (FIP).

Between 1980 and 1987 about 10% of the cats which underwent a post mortem examination at the Institute of Veterinary Pathology of the Freie Universität Berlin were infected with feline infectious peritonitis (FIP). The exudative, granulomatous or mixed form of the FIP are all symptoms of the same disease whose clinical picture is dependent on the state of the cellular immunity. Statistically there is no significant relationship between the form of the FIP and the age of the cats. A breed or a sex disposition is also not apparent. 42 organs and/or tissue samples were taken from a total of 30 cats and were examined both histologically and immunohistochemically. The antigen is located, above all, in the mesothelium and the cells of the mononuclear phagocyte system, whereas the parenchymatous inflammation foci show little evidence of the FIP-virus-antigen. The antigen is, however, also found in the nerve cells. Within the framework of a second viraemia, occurring after infection of the mesothelium (polyserositis), a perivasculitis non purulenta generalisata occurs. Possible excretory organs of the antigen are the respiratory, digestive and urinary tract.

Epitope-specific antibody responses to virulent and avirulent feline infectious peritonitis virus isolates.

Feline infectious peritonitis virus (FIPV) has been isolated several times from infected cats. Some of these isolates vary markedly in their ability to cause disease. Specific-pathogen-free cats were inoculated with the avirulent FIPV-UCD-2 isolate or the extremely virulent FIPV-79-1146 isolate or both. After 1 month, cats which had received FIPV-79-1146 were either dead or showed clinical signs of FIP. All cats which received only FIPV-UCD-2 remained healthy up to 6 months after inoculation. Antibody-mediated immune enhancement of disease was not observed in cats which received FIPV-UCD-2 before inoculation with FIPV-79-1146. Monoclonal antibodies which recognized type-specific epitopes on each of the structural polypeptides of these two viruses were used in competitive-inhibition enzyme-linked immunosorbent assays to analyze the humoral immune responses of the cats. All cats produced antibodies to epitopes found on the homologous virus. In addition, cats inoculated with FIPV-79-1146 also produced antibodies which inhibited the binding of the anti-FIPV-UCD-2 E1 monoclonal antibody. One cat inoculated twice with FIPV-UCD-2 produced antibodies which inhibited the binding of the anti-FIPV-79-1146 N- and E1-specific monoclonal antibodies. Competitive enzyme-linked immunosorbent assays may prove useful in distinguishing cats which are infected with virulent FIPV isolates from cats infected with avirulent feline coronaviruses.

An outbreak of avian urolithiasis on a large commercial egg farm.

A significant outbreak of avian urolithiasis was observed on a large commercial egg farm. From the initial outbreak site (a single laying house), the incidence of urolithiasis slowly spread in the ensuing months to numerous other laying houses. Increasing mortality associated with urolithiasis commenced during late growout to early lay and then leveled off when egg production peaked. At the height of the outbreak, mortality was typically 0.5% per week; 75% of this mortality was due to urolithiasis. The clinical and pathologic features of this condition are described. Both infectious bronchitis virus (IBV) and fowl adenoviruses were isolated from organ homogenates of sampled birds. A clone of the IBV strain was found to induce nephritis in specific-pathogen-free white leghorns.

Coronavirus JHM induced demyelinating disease: specific domains on the E2-protein are associated with neurovirulence.

Infections of rodents by murine coronaviruses can lead to chronic diseases of the central nervous system. These infections are interesting systems to study mechanisms which could be relevant for the pathogenesis of certain human diseases. One major factor influencing the outcome of infection is related to the virus. To understand the virological basis for neurovirulence we compared JHM-virus isolates with different biological properties. JHM-Wt causes only acute disease, JHM-Ts43 a demyelinating encephalomyelitis and a virus shedded from persistently infected cells (JHM-Pi) is not virulent at all. The spread of these viruses in glial cell cultures reflects their different neurovirulence for animals. The peplomer E2 of these viruses reveals structural and antigenic differences. We characterised the epitopes of E2 with a panel of monoclonal antibodies. Four epitopes are associated with regions important for neutralisation, cell fusion and attachment. More than five epitopes are not related to such functions. Epitopes differ in their location and accessibility on the E2 protein subunits between JHM-Wt, JHM-Ts43 and JHM-Pi. To identify epitopes in regions important for pathogenesis, we performed animal studies with variants selected by monoclonal antibodies. Variants changed in a defined epitope (E2-Ba) induce in Balb/c mice a chronic disease. Variants changed in only one of the other three neutralisation epitopes induce acute disease. These results support and extend the observation that the peplomer protein E2 is a major determinant for virulence and antigenic variability of coronaviruses 1,4,5,6,8,10,17,19,22,23. Increasing evidence had been obtained that certain structural features of this protein are important for the cell tropism of the virus. Furthermore, this protein influences strongly the type and specificity of immune responses against viral and host antigens. The highly advanced knowledge on structure and replication of coronaviruses will be of great value to analyze further mechanisms leading to inflammatory demyelinating diseases associated with a persistent virus infection.

Virologic and immunologic aspects of feline infectious peritonitis virus infection.

A number of feline coronavirus isolates have been characterized over the last few years. These isolates consist of what we have referred to as feline enteric coronaviruses (FECVs) and feline infectious peritonitis viruses (FIPVs). FECVs cause a transient enteritis in kittens but no systemic illness. FIPVs, in contrast, cause a systemic and usually fatal disease syndrome characterized either by an exudative serositis or a disseminated granulomatous disease. Although the diseases they cause are quite different, FECVs and FIPVs are antigenically and morphologically indistinguishable from each other. FECVs have a strict tropism for mature intestinal epithelial cells and do not appear to replicate in macrophages. In contrast, FIPVs, appear to spread rapidly from the intestinal mucosa and replicate in macrophages. Experiments will be presented, and literature cited, that will allow us to make the following assumptions about the pathogenesis of FIPV infection: 1) FIPVs and FECVs represent a spectrum of viruses that differ only in infectivity (ability to evoke seroconversion following oral infection) and virulence (ability to cause FIP), 2) field isolates are generally nearer to FECVs in behavior than laboratory isolates made from animal passaged material, 3) immunity to FIPV appears to be of the premunition type and is maintained for as long as the infection persists in a reactivatable form, 4) strains of feline coronaviruses that do not cause systemic disease, such as FECVs or low virulence FIPVs, can actually sensitize cats to infection with virulent FIPV strains, 5) FeLV infection interferes with established FIP immunity and allows for the reactivation of disease in healthy carriers, 6) FIPV may be passaged from queen to kitten either in utero or during neonatal life, and 7) kittens infected by their mothers with FIPV do not usually develop FIP but become immune carriers of the virus for a period of 5-6 months; recovery from the carrier state is associated with a loss of premunition immunity.

In vivo and in vitro models of demyelinating disease: endogenous factors influencing demyelinating disease caused by mouse hepatitis virus in rats and mice.

Intracerebral inoculation of JHM virus (JHMV), the neuropathic strain of mouse hepatitis virus, into Wistar Furth, Wistar Lewis, and Fischer 344 rats at various ages indicated that Wistar Furth rats are more susceptible to the virus than are the other strains. Fischer 344 and Wistar Lewis rats were more resistant to inoculation at 2 and 5 days of age and completely resistant by 10 days of age. In contrast, Wistar Furth rats which were very susceptible at both 2 and 5 days of age remained susceptible until 21 days of age. Intracerebral challenge of an F1 cross between Wistar Furth and Wistar Lewis rats at 10 days of age indicated that resistance to JHMV infection is dominant. Cyclophosphamide treatment 28 days after intracerebral inoculation exacerbated an inapparent infection, leading to paralysis in eight of nine and death in six of nine Wistar Furth test rats. In such immunosuppressed animals, grey- and white-matter lesions were noted throughout the central nervous system, in contrast to the purely demyelinating lesions noted previously. Since rats, unlike mice, were not susceptible to disease after intracerebral injection with the serorelated viscerotropic strain MHV-3, we wished to extend our understanding of the neurological disease process elicited by the two viruses in rodents. For this reason, various mouse strains, including some with recognized immunodeficiencies, were challenged by different routes of inoculation. Intraperitoneal infection of nude and beige mice with JHMV indicated that lack of natural killer cell functions does not markedly enhance the susceptibility to virus, whereas T-cell activity appears to be essential for resisting infection. JHMV and MHV-3 replication in peritoneal macrophages from highly resistant A/J mice was reduced in comparison with that noted in macrophages from susceptible C57BL6/J mice. An initial intraperitoneal inoculation of JHMV was able to protect C57BL6/J mice against fatal intracerebral challenge within 3 days, whereas A/J mice remained susceptible beyond day 3. The protective effect did not appear to result from increased levels of circulating interferon, preceded elevation in serum JHMV-neutralizing antibody titers, and persisted for at least several weeks after intraperitoneal inoculation. Based on the combined studies described here and on previous work by us and others, it appears that the factors influencing the outcome of coronavirus disease in rodents are age at inoculation, route of challenge, genetic constitution of the virus and host, and competence of the immune system, particularly cellular immunity involving T-cells.