A naturally occurring epizootic caused by Sendai virus in breeding and aging rodent colonies. II. Infection in the rat.

Sendai virus infected a hysterectomy derived, barrier maintained breeding colony and a conventional aging rat colony. The virus produced seroconversion in the colonies followed by a 7-month period of decreasing titers. Clinical signs were absent during the months when titers were highest, and there was no increase in mortality, but multifocal interstitial pneumonia with perivascular and peribronchial cuffing by lymphocytes and plasma cells was present in rat lungs examined histologically. Such lesions were absent before the period of seroconversion. During the months of declining titers, the interstitial and perivascular lesions decreased in frequency and severity. The peribronchial lesions did not decrease, however, and were still present in many rats 7 months after the acute infection. Attempts to isolate the virus from weanling rats were unsuccessful.     

Virus transmission to man from Phlebotomus flies: role of the Tuscany virus (Bunyaviridae, Phlebovirus) in the etiology of infections of the central nervous system

During field studies on the ecology of arboviruses in Italy, strains of a new virus were isolated from sand flies, mostly females, of a pure colony of Phlebotomus perniciosus collected in a central Italian region (Tuscany). The prototype was named Toscana (TOS) virus, assigned to the Phlebotomus fever serogroup of arboviruses (family Bunyaviridae, genus Phlebovirus) and registered in 1980 in the International Catalogue of Arboviruses. Neutralizing antibodies to TOS virus were detected in human sera. Serologic surveys were carried out to estimate the natural distribution of TOS virus in Italy and it was shown that antibodies to this virus could be detected in humans mainly of the Tuscany region. In particular, a high infection rate (24.8%) was observed among residents of the province of Florence. Furthermore, several patients with a diagnosis of aseptic meningitis presented a serologic response which reflected a recent infection with TOS virus in the Tuscany and Marche regions. Consequently, between 1980 and 1986 studies were conducted at selected sites of the Tuscany region to determine the possible occurrence of vectors and presence of foci of TOS virus and to assess its public health importance. As a result of these investigations, several virus strains were isolated from pools of wild caught Ph. perniciosus and Ph. perfiliewi. Of the virus isolates obtained, 37 were identified as TOS virus and 47 as a new serotype, member of the Phlebotomus fever group. For this virus we suggested the name of Arbia (ARB) virus, Arbia being the river flowing across both Florence and Siena provinces from which the isolates originated.(ABSTRACT TRUNCATED AT 250 WORDS)     

Respiratory disease associated with parainfluenza Type I (Sendai) virus in a colony of marmosets (Callithrix jacchus)

An outbreak of acute respiratory disease was observed in a colony of marmosets (Callithrix jacchus). Parainfluenza Type I (Sendai) virus was isolated from the lungs and from throat swabs of 2 animals which showed clinical signs of disease. A rising titre of serum neutralizing antibody to the virus isolated was detected in several affected animals. Approximately 50% of the colony showed clinical signs of disease, and 3 animals died. The duration of illness ranged from 3 to 16 days.     

Pox infection in white rats.

2 pox outbreaks among white rats in a breeding colony are described. The infection occurred in 3 different forms: pulmonary, dermal and mixed. Apparently healthy animals appeared to be virus carriers. The virus isolated belonged to the genus Orthopoxvirus of Poxviridae family, and was very close to cowpox virus. It differed from reference strains of cowpox virus in having a lower ceiling temperature and a higher pathogenicity for white rats.     

Experimental infection studies of Pasteurella pneumotropica and V-factor dependent Pasteurellaceae for F344-rnu rats.

To investigate the pathogenicities of P. pneumotropica (Pp) and V-factor dependent Pasteurellaceae (VFDP) in immunodeficient rats, experimental infections of F344-rnu rats were performed using 3 strains (ATCC 35149, CNP 160 and RPZ) of Pp and 4 strains (V6, V7, V8 and V9) of VFDP. Four animals per experimental group were inoculated twice on day 0 and post-inoculation day (PID) 14 with bacterial suspension intranasally. Two animals from each group were sacrificed on PID 60 and 120, and examined. In the animals inoculated with strains of Pp, sneezing was observed in some animals inoculated with strains ATCC 35149 and CNP 160 until PID 31. No clinical signs were observed in other animals. The strains were mainly isolated from the nasal cavity and trachea on PID 60, and the nasal cavity, trachea and lung on PID 120. Inflammation and necrosis of nasal cavity mucosa were observed in all animals inoculated with strains ATCC 35149 and CNP 160 in a histopathologic examination. No histopathological changes were observed in any other animal. In the animals inoculated with strains of VFDP, neither clinical disorder nor histopathological change was observed. The strains were mainly isolated from the trachea on PID 60, and from the trachea and lungs on PID 120. From these results, the pathogenicity of Pp in immunodeficient rats appears to differ by strain, and VFDP appears to be non-pathogenic in immunodeficient rats.     

Transformation of isolated rat hepatocytes with simian virus 40

Rat hepatocytes were transformed by simian virus 40 (SV40). Hepatocytes from two different strains of rats and a temperature-sensitive mutant (SV40tsA 1609), as well as wild-type virus were used. In all cases, transformed cells arose from approximately 50% of the cultures containing hepatocytes on collagen gels or a collagen gel-nylon mesh substratum. Cells did not proliferate in mock-infected cultures. SV40-transformed hepatocytes were epithelial in morphology, retained large numbers of mitochondria, acquired an increased nucleus to cytoplasm ratio, and contained cytoplasmic vacuoles. Evidence that these cells were transformed by SV40 came from the findings that transformants were 100% positive for SV40 tumor antigen expression, and that SV40 was rescued when transformed hepatocytes were fused with monkey cells. All SV40-transformed cell lines tested formed clones in soft agarose. Several cell lines transformed by SV40tsA 1609 were temperature dependent for colony formation on plastic dishes. Transformants were diverse in the expression of characteristic liver gene functions. Of eight cell lines tested, one secreted 24% of total protein as albumin, which was comparable to albumin production by freshly plated hepatocytes; two other cell lines produced 4.2 and 5.7%, respectively. Tyrosine aminotransferase activity was present in five cell lines tested but was inducible by dexamethasone treatment in only two. We conclude from these studies that adult, nonproliferating rat hepatocytes are competent for virus transformation.     

Strain and age-related changes in the localization of intestinal CD161+ natural killer cells and CD8+ intraepithelial lymphocytes along the longitudinal crypt axis in inbred rats

Using a cell position approach, this study indicates that the frequency of CD161(+) natural killer (NK) cells in the epithelia of DA rats was greater than that of WKAH and F344 rats. We further divided the epithelia into proliferating and differentiated regions according to the localization of BrdU-incorporated cells. Comparison between the different regions indicates that a majority of CD161(+) NK cells were located in the proliferating region. With age, a decline in the number of CD161(+) NK cells and CD8(+) intraepithelial lymphocytes (IELs) was observed in the distal colon, especially in the proliferating region of all three strains. Taken together with our previous report that DA rats have far stronger resistance in the colon to preneoplastic lesion than do other strains, these results indicate that CD161(+) NK cells play an important role in immune-surveillance at the bottom of the crypt.     

Epizootiological observations of natural and experimental infection with sialodacryoadenitis virus in rats

The epizootiology of sialodacryoadenitis (SDA) was studied in experimentally and naturally infected rats. The infectivity of SDA virus (SDAV) in intranasally infected rats was lost by seven days after infection as determined by contact transmission. After experimental infection, SN antibody appeared earlier and titers were detectable longer than CF antibody. The prevalence of SN antibody-positive rats in naturally infected colonies remained high, whereas an increase in the prevalence of CF antibody-positive rats appeared to coincide with the introduction or resurgence of SDAV. A SDAV-free colony was established by allowing recovered dams to litter in a separate room. A spontaneous cessation of SDAV infection also was observed in an enzootically-infected colony. Clinical observations indicated that SDA can occur as a mild or asymptomatic disease, and that its clinical expression may vary from one inbred strain to another.     

Downregulation of p56(lck) tyrosine kinase activity in T cells of squirrel monkeys (Saimiri sciureus) correlates with the nontransforming and apathogenic properties of herpesvirus saimiri in its natural host

Herpesvirus saimiri is capable of transforming T lymphocytes of various primate species to stable growth in culture. The interaction of the T-cellular tyrosine kinase p56(lck) with the transformation-associated viral protein Tip has been shown before to activate the kinase and provides one model for the T-cell-specific transformation by herpesvirus saimiri subgroup C strains. In contrast to other primate species, squirrel monkeys (Saimiri sciureus) are naturally infected with the virus without signs of lymphoma or other disease. Although the endogenous virus was regularly recovered from peripheral blood cells from squirrel monkeys, we observed that the T cells lost the virus genomes in culture. Superinfection with virus strain C488 did not induce growth transformation, in contrast to parallel experiments with T cells of other primate species. Surprisingly, p56(lck) was enzymatically inactive in primary T-cell lines derived from different squirrel monkeys, although the T cells reacted appropriately to stimulatory signals. The cDNA sequence revealed minor point mutations only, and transfections in COS-7 cells demonstrated that the S. sciureus lck gene codes for a functional enzyme. In S. sciureus, the tyrosine kinase p56(lck) was not activated after T-cell stimulation and enzymatic activity could not be induced by Tip of herpesvirus saimiri C488. However, the suppression of p56(lck) was partially released after administration of the phosphatase inhibitor pervanadate. This argues for unique species-specific conditions in T cells of S. sciureus which may interfere with the transforming activity and pathogenicity of herpesvirus saimiri subgroup C strains in their natural host.     

MHC and non-MHC genes regulate elimination of lymphocytic choriomeningitis virus and antiviral cytotoxic T lymphocyte and delayed-type hypersensitivity mediating T lymphocyte activity in parallel

The course of systemic infection with lymphocytic choriomeningitis virus was studied in mouse strains differing in the MHC or non-MHC background. Virus clearance rates differed significantly between H-2 identical strains as well as between congenic strains differing in the H-2L subregion, indicating that both H-2 and non-H-2 genes may influence the elimination of this virus. Differences in virus spread prior to appearance of the immune response could not explain the observed differences in clearance rate. On the other hand, inefficient clearance always correlated with low T cell responsiveness measured in terms of virus-specific cytotoxicity and delayed-type hypersensitivity, whereas no correlation was found with regard to NK cell activity and antiviral antibody response. Analysis of F1 progeny between H-2 identical high and low responder strains showed that low responsiveness with regard to all three parameters was recessive, indicating that natural tolerance is not the mechanism explaining non-MHC dependent low responsiveness in this system. The implications of these findings are discussed with specific reference to the role of MHC genes in controlling resistance to infectious diseases.     

Phenotype and genotype of Candida albicans strains isolated from pregnant women with recurrent vaginitis

Fourteen out of 80 pregnant women receiving prenatal care presented signs and symptoms of recurrent vaginal candidiasis. Candida albicans strains were isolated from 12 patients (85.7%), and these were submitted to morphotyping (morphological characteristics of the colony), antifungal typing (pattern of sensitivity to amphotericin B, 5-fluorcytosine, myconazole, ketoconazole and fluconazole) and genotyping (electrophoretic migration of DNA fragments digested with EcoRI and HinfI). Alteration of morphotype and antifungal type was observed in 50% of the patients, but the genotype of the strains isolated from the same patients at different times was identical in all subjects. The predominant morphotypes presented continuous fringes and the basic changes observed among antifungal types was the emergence of strains resistant to myconazole, which was the drug used for the treatment of the first episode of vaginitis. We conclude that recurrent vaginal candidiasis is caused by the persistence of a single yeast genotype that undergoes morphological and behavioral changes in the presence of antifungal agents due to the selective pressure to which it is submitted. This revised version was published online in August 2006 with corrections to the Cover Date.     

Diminished reproduction, failure to thrive, and altered immunologic function in a colony of T-cell receptor transgenic mice: possible role of Citrobacter rodentium

Citrobacter rodentium from an undetermined source was detected in a breeding colony of T-cell receptor transgenic mice housed in a conventional mouse facility in which murine hepatitis virus had been endemic and Helicobacter spp. had been detected. Citrobacter rodentium, isolated from blood, spleen, and colon, correlated with a significant increase in mortality and morbidity in this breeding colony. Transgenic mice of all ages were affected by chronic debilitation, loss in reproductive efficiency, rectal prolapse, and acute death, resulting in the near loss of these noncommercially available strains. Several alterations in immunologic parameters were observed, including outgrowth of an unusual population of cells in the spleen and blood, reduction in ascites production, loss of the capacity of peritoneal exudate cells to serve as feeders for the cloning of long-term T-cell lines, and inhibition of antigen-specific cytotoxic T-cell activity. These altered immune functions also were apparent in commercially-derived nontransgenic mice cohoused with the infected colony and in overtly healthy transgenic and nontransgenic littermates. Citrobacter rodentium and murine hepatitis virus were eliminated ultimately on rederivation of the affected strains by embryo transfer. However, the rapid decrease in the health of the colony necessitated more immediate action. To reduce mortality and allow breeding to continue during rederivation of the transgenic lines, animals were treated with enrofloxacin and moved to a barrier facility. Antibiotic therapy significantly reduced morbidity and mortality, markedly increased litter size and frequency, and resulted in the normalization of many of the immunologic assays. The involvement of C. rodentium in altering viability of the colony and perturbing immunologic assays is suggested by correlation of the onset of the syndrome with the appearance of Citrobacter sp. and its resolution with the elimination of Citrobacter sp. from the colony. Whether infection with Citrobacter alone is causative or whether superinfection of murine hepatitis virus- and Helicobacter-infected mice is required remains to be determined.     

Deletions in the genomes of pseudorabies virus vaccine strains and existence of four isomers of the genomes

As part of a study designed to identify the genes responsible for the virulence of pseudorabies virus, we have mapped the genomes of two independently derived vaccine strains (Bartha and Norden) by restriction enzyme analysis. The structures of these genomes have been compared with that of the genome of a laboratory strain previously mapped, of restriction fragments which had been cloned. The genome of the Bartha strain was found to be very similar to that of other pseudorabies virus strains, except that a deletion of approximately 2.7 X 10(6) daltons was found in the unique short (US) region. This deletion was also observed in the genome of the Norden vaccine strain but was not observed in the genomes of any other pseudorabies virus strains that have been studied (more than 20). The genome of the Norden strain differs from that of other pseudorabies virus strains in several other respects as well. The most important difference is that in contrast to all other pseudorabies virus strains analyzed to date, which contain a type 2 herpesvirus DNA molecule (in which the US region only inverts itself relative to the unique long [UL] region), the genome of the Norden strain is a type 3 molecule in which both the US and the UL regions of the genome invert themselves, giving rise to four isomeric forms of the genome. The ability of the UL region to invert itself is probably related to the fact that a sequence normally present in all other pseudorabies virus strains at the end of the UL only is found also in inverted form at the junction of the UL and the internal inverted repeat in the Norden strain.     

Protection by Live, Attenuated Simian Immunodeficiency Virus against Heterologous Challenge

We examined the ability of a live, attenuated deletion mutant of simian immunodeficiency virus (SIV), SIVmac239Delta3, which is missing nef and vpr genes, to protect against challenge by heterologous strains SHIV89.6p and SIVsmE660. SHIV89.6p is a pathogenic, recombinant SIV in which the envelope gene has been replaced by a human immunodeficiency virus type 1 envelope gene; other structural genes of SHIV89.6p are derived from SIVmac239. SIVsmE660 is an uncloned, pathogenic, independent isolate from the same primate lentivirus subgrouping as SIVmac but with natural sequence variation in all structural genes. The challenge with SHIV89.6p was performed by the intravenous route 37 months after the time of vaccination. By the criteria of CD4(+) cell counts and disease, strong protection against the SHIV89.6p challenge was observed in four of four vaccinated monkeys despite the complete mismatch of env sequences. However, SHIV89.6p infection was established in all four previously vaccinated monkeys and three of the four developed fluctuating viral loads between 300 and 10,000 RNA copy equivalents per ml of plasma 30 to 72 weeks postchallenge. When other vaccinated monkeys were challenged with SIVsmE660 at 28 months after the time of vaccination, SIV loads were lower than those observed in unvaccinated controls but the level of protection was less than what was observed against SHIV89.6p in these experiments and considerably less than the level of protection against SIVmac251 observed in previous experiments. These results demonstrate a variable level of vaccine protection by live, attenuated SIVmac239Delta3 against heterologous virus challenge and suggest that even live, attenuated vaccine approaches for AIDS will face significant hurdles in providing protection against the natural variation present in field strains of virus. The results further suggest that factors other than anti-Env immune responses can be principally responsible for the vaccine protection by live, attenuated SIV.     

Preliminary studies of the complement fixation test to confirm the diagnosis of bovine ephemeral fever

A strain of bovine ephemeral fever (BEF) virus isolated in China in 1976 was adapted to growth in tissue cultures. A baby hamster kidney complement fixing (CF) antigen, stable at -20 degrees C for at least 120 days, was prepared from the BEF virus grown in tissue culture and used to test bovine sera for antibodies to that virus. CF antibodies were detected in all of 31 cattle after convalescence from experimental infection with BEF virus, in 208 (98%) of 213 cattle observed to have shown clinical ephemeral fever in an epidemic, in 96 cattle in these herds which did not show clinical signs of ephemeral fever and 16 cattle from herds in northern China outside the epidemic area. The CF antibodies to BEF virus were found to persist in 34 (89%) of 38 cattle which were bled 6 years after natural exposure to ephemeral fever. The CF antigen is economical to prepare and is suitable to differentiate ephemeral fever from other viral infections with which it could possibly be confused on clinical appearance.     

Immunogenic activity of temperature sensitive mutation of herpes simplex virus type-1 in mono- and polyvalent conditions with different attenuated strains of virus. II. Analysis of humoral immunologic response induced by mutants of temperature sensitive herpes simplex type-1 virus in polyvalent systems

The ability of mutant ts HSV-1 on 45 passage to induction of IgG antibody response in the presence of other attenuated viral strain, like measles, mumps, rubella was evaluated, and the effect of mutant ts HSV-1 on humoral immunity induced by attenuated measles and mumps strains was also tested. The obtained results clearly indicated that even immunization with other RNA virus strains had no effect on IgG antibody response to mutant ts HSV-1. Significant differences were observed in IgG antibody responses to mumps and measles between groups of guinea pigs immunized with these viruses alone or together with other viruses. This was especially observed in the case of mumps virus. It clearly shows that change of virus concentration rates in polyvalent schema of immunization is needed.     

Viral infectious and chromosome aberrations in Bank Vole from natural and laboratory populations]

The frequency of chromosome damage was studied in the carriers of virus of the hemorrhagic fever with renal syndrome (Puumala virus) and in noninfected animals from two laboratory colonies and two natural populations of bank vole. In the laboratory colony, where Puumala virus persisted for three years, multiaberrant ("rogue") cells were found in the bone marrow; the mean frequencies of both structural and numeral chromosome abnormalities were significantly enhanced. In the other laboratory colony, no Puumala virus was detected during all 30 years of its existence, but the mean frequencies of structural chromosome damage were increased to the same degree probably due to the prolonged breeding under laboratory conditions, which resulted in suppression of immunity and DNA repair. The voles from the natural populations were more resistant to the clastogenic viral effect, but they also had multiaberrant cells which served as indicators of viral infection. The data obtained support the hypothesis that viral infections increase mutation rate, contributing thereby to the evolution process.     

Pathogenesis of a newly isolated rat virus in newborn and juvenile rats.

The pathogenesis of the UT-1 strain, a newly isolated rat virus (RV), in juvenile and newborn rats was examined. Intracerebrally (ic) inoculated newborns developed severe pantropic infections resulting in emaciation, stunted growth, diarrhea, dehydration and icterus, and died 13 to 15 days after the inoculation. Newborns inoculated intraperitoneally (ip) developed similar, but milder diseases. The virus replicated in all the organs tested, which was followed by severe viremia. Histopathologically, diffuse vacuolation and necrosis of the hepatocytes were observed in the liver. Juvenile rats inoculated with the virus showed neither clinical signs nor histopathologic lesions, although viral recovery and antibody production were observed. Thus, we conclude that the UT-1 strain of RV caused asymptomatic infections in juvenile rats, and fatal infections with hepatic lesions in newborn rats.     

Association of SAIDS/RF-related signs with current or past SAIDS type 2 retrovirus infection in a colony of Celebes black macaques

The 83 members of the Celebes black macaque (Macaca nigra) colony were screened for viremia with simian acquired immunodeficiency syndrome (SAIDS) type 2 retrovirus and antibodies against the retrovirus. On the basis of this screening, the Celebes colony was divided into four groups: retrovirus-positive/seropositive (virus+/Ab+); retrovirus-negative/seropositive (virus-/Ab+); retrovirus-positive/seronegative (virus+/Ab-); and retrovirus-negative/seronegative (virus-/Ab-). Monkeys in the virus+/Ab+ group displayed more major clinical signs and required medication more times than monkeys in the other groups. In contrast, monkeys in the virus-/Ab- group had fewer health problems than monkeys in the other groups. The five monkeys that had surgically confirmed retroperitoneal fibromatosis (RF), palpable abdominal masses, or both, were in the virus+/Ab+ group. Some of the monkeys in groups with current or past retrovirus infection were well clinically. There were no statistically significant differences in the mitogen reactivities of mononuclear cells obtained from monkeys of the different groups.