The response to Epstein-Barr virus infection in Sjögren's syndrome

To assess the response to Epstein-Barr virus (EBV) infection in patients with primary Sjögren's syndrome (SS), the frequency of detection of EBV DNA was studied in salivary gland biopsies and the antibody and idiotypic response to the virus was compared with healthy controls and infectious mononucleosis (IM). Viral DNA, detected by in-situ hybridization, was found in biopsies from two out of 12 patients with SS and six out of 10 controls. IgG, IgA and IgM antibodies to the virus, measured by ELISA using synthetic peptides (early antigen and EBNA-1) and a cloned fusion protein (EBNA-1), were normal in sera from 20 patients with SS, whereas infectious mononucleosis patients showed an increase in IgM antibodies to EBNA-1 and IgG antibodies to early antigen. One similarity between infectious mononucleosis and Sjögren's syndrome was a significant increase in the germline heavy chain idiotype G6 in both diseases, suggesting activation of similar B-cell subsets. It is possible that this is due to EBV, though the low frequency of EBV DNA in biopsies and the normal levels of EBV antibodies in SS does not lend any evidence that the virus itself is the causative agent.

Enhancement of virus transmission by tick salivary glands

Previous studies have demonstrated that Thogoto (THO) virus is transmitted from infected to uninfected ticks cofeeding on an uninfected guinea-pig, although the guinea-pig does not develop a detectable viraemia. To investigate this mode of transmission, guinea-pigs were infected with uninfected Rhipicephalus appendiculatus nymphs prior to inoculation with either a mixture of THO virus and tick salivary gland extract, or with THO virus alone. The number of ticks that acquired the virus from feeding on animals inoculated with a mixture of virus and salivary gland extract was 10-fold greater than the number that became infected by feeding on animals inoculated with virus alone. The increase in the number of ticks that became infected was greatest when the salivary glands used in the inoculum were derived from uninfected ticks, which had partially fed for a period of 6 days. Viraemia was not detected in any of the guinea-pigs tested during the experiments. These results indicate that THO virus transmission is enhanced by factor(s) associated with the salivary glands of ticks, and that these factor(s) may facilitate 'non-viraemic' transmission between infected and uninfected ticks.

[The fractions, functions, methods of isolation and the significance for transmission of causative agents of the saliva of ixodid ticks]

The authors present a review on the structure and functions of salivary glands of the Ixodidae ticks, attaching to the host's skin by means of a cement fraction: current ideas on the neurohormonal regulation of salivary function are presented. The method of obtaining various saliva fractions--cement-containing and liquid--from unfed infected ticks belonging to 3 genera (Hyalomma, Dermacentor and Ixodes)--by parenteral administration of secretotropic substances is described. The first portions of saliva, both liquid and cement-forming, are shown to contain tick-borne encephalitis viruses in amounts sufficient for the infection of animals. Epidemiological value of the presence of viruses in the cement cork formed in the host's skin and in the first portion of liquid saliva is discussed.

Detection of Epstein-Barr virus DNA by polymerase chain reaction in blood and tissue biopsies from patients with Sjogren's syndrome

Polymerase chain reaction has been used to detect increased levels of EBV DNA in salivary gland (SG) biopsies and PBL from patients with Sjogren's syndrome (SS). These results suggest that EBV, which has a normal site of latency in a small number of SG epithelial cells, may be reactivated in SS patients and provide a target for immune attack. The great sensitivity of polymerase chain reaction (PCR) and the ability to analyze very small tissue biopsies (37) make this technique well suited for clinical diagnosis. Specific methods to prevent artefactual contamination of tissue biopsy DNA with viral DNA of other samples (i.e., lyophilization of samples before DNA extraction) and the use of an internal positive control (i.e., inclusion of primers for a single copy human gene) during PCR amplification are presented. Since EBV reactivation occurs with markedly increased frequency in patients with lymphoproliferative and immunodeficiency diseases, as well as transplant recipients receiving cyclosporin A (10), rapid methods of viral detection such as PCR may allow better monitoring of medications and early detection of EBV-related lymphomas that may arise in these patients.

Anatomical basis of Thogoto virus infection in BHK cell culture and in the ixodid tick vector, Rhipicephalus appendiculatus

Infection by Thogoto (THO) virus, a tick-borne virus related to the orthomyxoviruses, has been compared in vertebrate cell culture and in Rhipicephalus appendiculatus ticks using infectivity titrations, immunofluorescence, and immune electron microscopy with colloidal gold markers to detect cell surface and intracellular antigens. Morphogenesis of THO virus in cell culture was similar to that of influenza virus, with polymorphic virus particles budding at the plasma membrane. In the tick, THO viral infection caused no obvious pathology; virions or budding profiles were not observed in electron micrographs, although replication, trans-stadial persistence and transmission to a susceptible host occur. THO virus was not detected in the salivary glands of trans-stadially infected ticks until about 7 days after the commencement of feeding on a host. The synganglion (brain) appears to be the major organ involved in trans-stadial persistence of the virus; viral antigens were detected in the neural cortex (cell bodies) but not in nerve fibres and axons. The detection of THO viral antigen in basement membranes and connective tissue, but its absence from nerve fibres, suggests that dissemination occurs via the haemolymph rather than a neural route.

Site-restricted persistent cytomegalovirus infection after selective long-term depletion of CD4+ T lymphocytes

We have established a murine model system for exploring the ability of a CD4 subset-deficient host to cope with cytomegalovirus infection, and reported three findings. First, an antiviral response of the CD8 subset of T lymphocytes could be not only initiated but also maintained for a long period of time despite a continued absence of the CD4 subset, whereas the production of antiviral antibody proved strictly dependent upon help provided by the CD4 subset. Second, no function in the defense against infection could be ascribed as yet to CD4-CD8- T lymphocytes, which were seen to accumulate to a new subset as a result of depletion of the CD4 subset. This newly arising subset did not substitute for CD4+ T lymphocytes in providing help to B lymphocytes, and was also not effective in controlling the spread of virus in host tissues. As long as a function of these cells in the generation and maintenance of a CD8 subset-mediated response is not disproved, caution is indicated with concern to an autonomy of the CD8 subset. Third, even though with delay, the CD8+ effector cells raised in the CD4 subset-deficient host were able of clear vital tissues from productive infection and to restrict asymptomatic, persistent infection to acinar glandular epithelial cells in salivary gland tissue.

Epstein-Barr virus in the sublabial salivary gland in Sjögren's syndrome

The proposed role of Epstein-Barr virus (EBV) in salivary gland destruction in Sjögren's syndrome (SS) prompted the authors to study the presence of EBV-DNA (hybridohistochemistry) and EBV-encoded proteins (immunohistochemistry) in sublabial salivary glands taken from eight patients with primary and five with secondary SS and from 16 controls. DNA probes and anti-EBV antibodies were controlled for activity by assessment of human blood B-lymphocytes after in vitro infection with EBV. None of the tissues investigated manifested the presence of EBV proteins (nuclear antigen, early antigen R, membrane antigen, or viral capsid antigen). The salivary gland biopsies of four patients with primary SS and two with secondary SS showed EBV-DNA in epithelial cells of acini and ducts but not in other components. The authors data contrast with those of Fox and colleagues (J Immunol 1986;137:3162-3168), who reported that about half of the patients with SS have EBV early antigen D in epithelium of the sublabial salivary gland. The authors conclude that an active EBV infection associated with EBV protein synthesis does not occur in the diseased salivary gland of patients with SS, but the presence of EBV-DNA in the glands does not exclude a possible role of EBV in the disorder.

Persistence of Epstein-Barr virus in salivary gland biopsies from healthy individuals and patients with Sjögren's syndrome

Salivary gland biopsies from 12 patients with primary Sjögren's syndrome and 10 controls were examined for Epstein-Barr virus (EBV) DNA by in-situ hybridization and for EBV proteins by immunofluorescence and peroxidase techniques. Viral DNA was found in biopsies from two out of 12 patients with primary Sjögren's syndrome and six out of the 10 controls. The DNA and early antigen were in epithelial cells lining the ducts and acini, early antigen expression being limited to the luminal side of the epithelium. In eight biopsies studied with other antibodies, membrane antigen was identified in both acini and ducts but viral capsid antigen and Epstein-Barr nuclear antigen were not detected. EBV was found in biopsies from five of the controls without inflammation or Class II expression. This suggests that, in health, persistence and replication occur without inducing an immune response, possibly due to the restricted expression of early antigen on the luminal of the epithelium, away from immune surveillance. The inflammation in Sjögren's syndrome could be due to a breakdown of this unusual mechanism for viral persistence leading to a vigorous immune response to the virus. However our study provides no evidence to suggest that EBV infection load is increased in this disease.

Replication, tissue tropisms and transmission of yellow fever virus in Aedes albopictus

Experimental studies undertaken to ascertain the dynamics of yellow fever virus replication in an introduced strain (Houston) of the Asian mosquito, Aedes albopictus (Skuse), indicate that this species is an efficient vector of yellow fever virus. Replication of virus in Ae. albopictus could be detected 3 d after feeding on a suspension containing 7.2 log10 Vero cell plaque forming units (PFU) per ml of virus; peak titres (3.5 log10 PFU/mosquito) occurred 7 d after exposure. Viral antigen, visualized by immunofluorescence, was first detected in midgut cells 4 d after exposure and appeared in fat cells 7 d after exposure. The only other mosquito tissues revealing viral antigen were the salivary glands, brain, and occasionally cells of the suboesophageal ganglion. Viral antigen was not detected in any of the tissues of the reproductive tract, nor could viral genomic ribonucleic acid (RNA) be detected in these tissues by RNA-RNA molecular hybridization in situ. We detected no vertical transmission of yellow fever virus in 6180 F1 adult progeny produced from infected females. The extrinsic incubation period at 26.7 degrees C was 9 d. We conclude that the Houston strain of Ae. albopictus is a competent vector of yellow fever virus and can serve as bridging vector between the jungle yellow fever cycle and the urban cycle in New World ecosystems.

The distribution of Rift Valley fever virus in the mosquito Culex pipiens as revealed by viral titration of dissected organs and tissues

Distribution of Rift Valley fever virus (RVFV) was studied in the mosquito Culex pipiens. Mosquitoes were dissected on days 1-7 after an infectious bloodmeal, and RVFV plaque assays were performed on the legs, posterior midgut, ovaries, salivary glands, thoracic ganglia, and remaining organs and tissues (remnants). On days 7-12 and 14 following an infectious bloodmeal, mosquitoes were tested for their ability to transmit virus and then dissected. Dissemination (systemic infection) rates averaged 22% on days 1-14 and transmission rates 33% on days 7-14. There were no significant differences in the viral titers of midgut samples among the nondisseminated infected (virus limited to alimentary canal), disseminated infected nontransmitting, and transmitting groups of mosquitoes. The sequence of infection of the organs and tissues studied appeared to be as follows: midgut, hemolymph, remnants: salivary glands, ovaries, and thoracic ganglia. Some individuals were found to have disseminated infections as early as 12 hr following an infectious bloodmeal. Trauma, simulated by vigorous shaking immediately following the viremic bloodmeal, did not affect either infection or dissemination rates.

Preliminary studies of the development of Anaplasma marginale in salivary glands of adult, feeding Dermacentor andersoni ticks

On each day of feeding on susceptible calves, salivary glands obtained from groups of adult ticks that transmitted Anaplasma marginale were examined for A marginale colonies by use of light microscopy and transmission electron microscopy. On day 8 of feeding, salivary glands were examined, using fluorescein-labeled antibody and methyl green-pyronine stain. Use of fluorescein-labeled antibody consistently revealed small numbers of fluorescent foci in salivary gland acinar cells obtained from ticks that had fed for 8 days. Colonies of A marginale were seen by transmission electron microscopy only in salivary gland acini of male ticks; these colonies could not be identified, using light microscopy, in companion 1-micron plastic sections stained with Mallory stain. Methyl green-pyronine stain, used commonly to detect theilerial parasites in tick salivary glands, did not differentiate A marginale from cytoplasmic inclusions normally found in salivary gland acinar cells.

Distribution of a macaque immunosuppressive type D retrovirus in neural, lymphoid, and salivary tissues

Simian acquired immune deficiency syndrome (SAIDS) in rhesus macaques (Macaca mulatta) at the California Primate Research Center is caused by a type D retrovirus designated SAIDS retrovirus serotype 1 (SRV-1). This syndrome is characterized by profound immunosuppression and death associated with opportunistic infections. Neurologic signs and lesions have not been described as part of this syndrome. The distribution of SRV-1 in the salivary glands, lymph nodes, spleens, thymuses, and brains of eight virus-infected rhesus macaques was examined by immunohistochemistry. Electron microscopy, in situ RNA hybridization, and Southern blot hybridization were also performed on selected tissues to detect viral particles, RNA, and DNA, respectively. In seven of eight SRV-1-infected animals, the transmembrane envelope glycoprotein (gp20) of SRV-1 was present in three or more tissues, but never in the brain. In the remaining animal, no viral antigen was detected in any tissue. In this same group of animals, viral nucleic acid was detected in the lymph nodes of six of six animals by Southern blot hybridization, in the salivary glands of two of five animals by both Southern blot and in situ hybridizations, and, surprisingly, in the brains of three of three animals by Southern blot and of three of five animals by in situ hybridization, including the one animal in which viral gp20 was undetectable. None of these animals had neurologic signs or lesions. The detection of viral nucleic acid in the absence of viral antigen in the brain suggests latent SRV-1 infection of the central nervous system.

Togavirus-associated pathologic changes in the midgut of a natural mosquito vector

Arthropod-borne viruses were not previously believed to cause discernible pathologic changes in their natural mosquito vectors. We report cytopathologic lesions in the midgut of the mosquito, Culiseta melanura, 2 to 5 days after oral infection with eastern equine encephalomyelitis virus. Sloughing of densely staining, heavily infected epithelial cells into the midgut lumen was observed by light and transmission electron microscopy, along with degeneration of cells within the epithelium. Pathological changes in midgut epithelial cells sometimes included loss of brush border and basal lamina integrity. Disruption of the midgut basal lamina could result in bypassing of barriers to virus dissemination within the mosquito and allow rapid transmission to occur. Alternatively, luminal sloughing of heavily infected midgut epithelial cells may serve to modulate mosquito infections. These findings challenge previous beliefs regarding the benign nature of arbovirus-invertebrate host relationships.

[Biological properties of variants of the rabies street virus]

Experiments in dogs inoculated intracerebrally with biological variants of paralytic (PRV) and convulsive (CRV) rabies virus isolated from the Yak strain population of street rabies virus demonstrated distinct differences in the biological properties of the variants PRV induced in dogs paralytic rabies with a short incubation period (average 6.4 days) and CRV induced an atypical convulsive form characterized by attacks of tonic convulsions of the body, legs, and head twitching, and a longer incubation period (18.5 and 9.6 days, respectively). This explains a wide variability of the biological properties of street rabies virus strains.

Growth characteristics in cell culture and pathogenicity in mice of two terrestrial rabies strains indigenous to Canada

Two strains of street rabies virus from striped skunks (Mephitis mephitis) were used to infect either a murine neuroblastoma (NA 1300) or a baby hamster kidney (BHK-21/C13) cell culture and the cell infection rates were noted during 4 days postinfection. These cultures were then passaged for four consecutive passages, and the viruses obtained in the supernatant fluids of passage 4 were then treated as original isolates and used to infect both neuroblastoma and baby hamster kidney cells. The mortality period in Swiss white mice caused by the various virus suspensions was noted. The virus strain from the brain of skunks from Saskatchewan infected neuroblastoma and baby hamster kidney cells equally well, produced similar virus titres in supernatant fluids after four subcultures in both cell types, and appeared to produce similar mortality periods in mice from either the original brain tissue or from cell culture supernatant fluids. On the other hand, the virus from the brains of skunks from Ontario readily infected neuroblastoma but poorly infected baby hamster kidney cell cultures. Passage of this strain through four subcultures in both cell types produced virus titres in the supernatant fluids of equal magnitude. However, reisolation of the virus from the supernatant fluid of passage 4 in neuroblastoma cell cultures showed a similar pattern to that from the original brain, while the virus from baby hamster kidney cell passage supernatant fluid was considerably altered. Although the mortality period in mice was similar with virus from the brain and neuroblastoma cell cultures, this period was shortened when mice were inoculated with baby hamster kidney culture supernatant virus.(ABSTRACT TRUNCATED AT 250 WORDS)

Reactivation of Epstein-Barr virus in Sjögren's syndrome

Sjögren's syndrome (SS) is an autoimmune disease characterized by lymphocytic infiltration and destruction of salivary and lacrimal glands. This condition may be limited to glandular tissues or may be associated with other autoimmune disorders such as rheumatoid arthritis or systemic lupus erythematosus. Since the environmental factors that initiate SS are unknown, we have investigated the potential role of Epstein-Barr virus (EBV), cytomegalovirus (CMV) and other viruses. We observed that epithelial cells in salivary gland biopsies of SS patients contained antigens reactive with monoclonal antibodies against EBV-associated antigens. These antigens were not found in other tissues of SS patients and were absent in salivary gland biopsies from normals and patients with other autoimmune diseases lacking SS. Also, the content of EBV DNA in the saliva of SS patients was significantly greater than in age- and sex-matched controls or individuals with other autoimmune disorders. These studies provide one of the first examples where a specific viral agent may be implicated in perpetuating a chronic autoimmune disease. However, great caution must be used before an etiologic role can be attributed to an ubiquitous agent such as EBV.

Replication of mumps virus in mouse: transient replication in lung and potential of systemic infection

A mumps virus strain, which replicated in mouse lung after aerosol inhalation, was obtained by selective replication of a wild strain in L929 cells and by further passaging in mice by intraperitoneal inoculation. All of infected mice survived and rechallenge of the survived mice with the same virus resulted in no virus growth in the lung. Treatment of infected mice with antiserum against interferon (IFN) or asialo GM1 delayed virus clearance from lung. Mice at 5 weeks of age were also sensitive to the virus as well as those at 1 week. When injected intravenously, the virus could grow not only in lung but also in salivary glands, heart and spleen. Furthermore, the virus replicated in liver, spleen, pancreas and testis after intraperitoneal inoculation. Antibody response of mice infected by aerosol inhalation was slower than that of intraperitoneally infected ones in either IgG or IgM production. These results indicated that the adapted virus replicated in mouse lung by a natural route of infection and had a potential to cause systemic infection in mouse.

9-(1-3-Dihydroxy-2-propoxymethyl)guanine prevents death but not immunity in murine cytomegalovirus-infected normal and immunosuppressed BALB/c mice

Immunosuppressed (from treatment with cortisone acetate and anti-thymocyte globulin) and control adult female BALB/c mice, latently infected with murine cytomegalovirus (MCMV) or lethally challenged (10(6) PFU) with MCMV intraperitoneally, were treated with 9-(1-3-dihydroxy-2-propoxymethyl)guanine (DHPG) intraperitoneally. A dose of 3 mg/kg reduced mortality by 50% in lethally challenged normal mice; 10 mg/kg was required in immunosuppressed mice. When 15 mg/kg was given, the onset of treatment could be delayed for 64 h after lethal challenge. DHPG did not prevent the establishment of latent MCMV infection or immunosuppression-induced reactivation. The antibody titer to MCMV in DHPG-treated mice which survived lethal challenge was 41 (reciprocal of geometric mean) 4 to 5 weeks after inoculation; such mice survived a second lethal challenge. When antiserum treatment was begun 64 h and DHPG was begun 72 h after a lethal challenge, most mice survived; most did not when either treatment alone was begun at those times. In summary, DHPG effectively treated lethal MCMV infection even in immunosuppressed mice and even when treatment onset was delayed for 64 h. Treatment did not alter the establishment or reactivation of latent infections or the induction of effective immunity. The administration of DHPG coupled with antiserum treatment may be even more effective than the administration of either alone.

The pathogenesis of Japanese encephalitis virus in Culex tritaeniorhynchus mosquitoes

Culex tritaeniorhynchus were inoculated intrathoracically with mosquito and human strains of Japanese encephalitis virus and maintained at 26 degrees C or 32 degrees C. Virus titration and localization of viral antigen by avidin-biotin immunoperoxidase staining were done at intervals up to 21 days. Marked differences were noted in the tempo of organ involvement at the 2 temperatures; at both there was initial infection of fat body cells followed by selective infection of the central nervous system (CNS), with consistent infection of cells of the compound eye, patchy involvement of cephalic, thoracic and abdominal ganglia and no infection of Johnston's organ. CNS infection was always present 4 days after infection, when salivary gland involvement was first seen at 32 degrees C; at 26 degrees C CNS infection preceded salivary gland infection by 2 weeks. Late involvement of gut cells, pericardial cells and oviducts was also found, with no involvement of muscle.

Genetically determined resistance to lethal murine cytomegalovirus infection is mediated by interferon-dependent and -independent restriction of virus replication

Susceptibility of 4-week-old mice of different strains to lethal murine cytomegalovirus (MCMV) infection was studied. Strains homozygous for H-2k and C57BL strains were resistant to greater than or equal to 10(5.5) PFU. B10.BR mice congenic for C57BL background genes and H-2k were about 10-fold more resistant than either C3H/HeN or C57BL strains. BALB/c mice (H-2d) were susceptible (50% lethal dose, 10(5.05) PFU). This susceptibility was dominant over resistance associated with H-2k but not that associated with C57BL background genes. The dominant susceptibility trait segregated in backcross mice as if carried by a single gene. Virus replication in spleen cells in vivo correlated with susceptibility to lethal infection. A similar trend was found in tests of salivary glands. Replication of MCMV in vitro in cultures of adherent spleen cells and primary mouse embryo cells correlated with replication in vivo. Neutralization of interferon (IFN) in cultures of adherent spleen cells reversed H-2k-linked restriction of viral replication but had minor effects on cells of other strains. Natural killer cell responses to infection were often higher in more resistant strains, but B10.BR mice developed minimal natural killer cell responses. Specific antibody and cytotoxic T cell responses in B10.BR mice were similar or lower than in other strains. Thus, resistance to lethal MCMV infection was not immunologically mediated, was dependent on and reflected by the capacity of cells from a given mouse strain to support replication in vivo and in vitro, and was IFN dependent and recessive if linked to H-2k but IFN independent when associated with C57BL background genes.

Adult Ixodes dammini on rabbits: a hypothesis for the development and transmission of Borrelia burgdorferi

A histological study of unfed Ixodes dammini adults has shown that the Lyme disease spirochete can be found in the midgut diverticula of these ticks and is presumably carried over from the nymphal stage. Sequential histology of the early stages of ticks feeding on a rabbit showed that spirochetes began to divide and were located in close proximity or attached to the epithelial cells of the diverticulae. Evidence for division was obtained by the higher number of spirochetes per tick after a three-day feeding period than in the unfed females. Although the mechanism is unclear, some spirochetes become systemic by the fifth day of feeding and can be detected in low numbers in other tick organs. Spirochetes were also noted in the feeding cavities created by I. dammini in the dermis after five days of attachment. Spirochetes were not detected in salivary glands or in the feces of I. dammini during the feeding period.

The effect of biological response modifiers on chronic and latent murine cytomegalovirus infections

Host-mediated antiviral effect of 2 biological response modifiers (BRM), OK-432, and PS-K, against murine cytomegalovirus (MCMV) was evaluated in chronically or latently infected mice. In the early stage of chronic MCMV infection, the BRM-induced resistance was evidenced by decrease in infectious viruses replicated in the salivary glands and by augmented cytotoxic activity of the spleen cells against YAC-1 cells and MCMV-infected mouse embryonic fibroblasts (MEF). In the late stage of chronic MCMV infection, the BRM treatment did not eliminate MCMV from the mice, but did prevent exacerbation of MCMV infection in the salivary glands induced by administration of cyclophosphamide (CY). In mice latently infected by MCMV, BRM treatment suppressed CY-induced reactivation of MCMV in the salivary glands. It was suggested that the antiviral effect of BRM against MCMV in chronically or latently infected mice was based on activation of natural killer (NK) cells and cytotoxic T lymphocytes (CTL).