Transmission of experimentally-induced rat virus infection

The duration of transmission of rat virus (RV) infection was determined using Sprague-Dawley rats inoculated oronasally as juveniles (4 weeks old) or as infants (2 days old). Contact transmission from rats inoculated as juveniles was detected for 3 weeks, whereas transmission from rats inoculated as infants occurred for 10 weeks. Transmission continued for at least 7 weeks after seroconversion occurred in rats inoculated as infants. Two of three rats that had ceased to transmit infection harbored infectious virus as detected by explantation of kidney. Intrauterine transmission occurred only after pregnant dams were inoculated with large doses of virus and was more efficient when virus was inoculated intravenously than by the oronasal route. Enzyme immunoassay antibody titers to RV in offspring of previously infected dams decreased steadily during the first 13 weeks of life and 27 of 29 offspring tested by immunofluorescence assay at 12 or 13 weeks of age were seronegative. These results indicate that RV was transmitted by rats inoculated as infants for long periods after seroconversion occurred. They also suggest that the offspring of previously-infected dams were not infected. In utero transmission of RV-Y is unlikely to occur after oronasal inoculation unless rats are exposed to large doses of virus.     

Passive immunization against transmissible gastroenteritis virus in piglets by ingestion of milk of sows inoculated with attenuated virus.

Pregnant sows were inoculated with the attenuated strain, TO--163, of swine transmissible gastroenteritis virus. Suckling piglets born from them received challenge inoculation with the virulent virus at 3 days after birth, and examined for ability to prevent infection and the immunoglobulin (Ig) classes of antibody in milk. A pregnant sow was inoculated intramuscularly with a dose of 10(8.0) TCID50 and intranasally with a dose of 10(9.3) TCID50 of attenuated virus. Piglets born from it suffered from diarrhea after challenge inoculation, but none of them died eventually. Their dam was also affected with diarrhea for 4 to 7 days after challenge inoculation of them. Another pregnant sow was inoculated twice with 10(9.3) TCID50 of attenuated virus, first by the intramuscular and secondly by the intranasal route. Of nine piglets born from it, one excreted soft feces after challenge inoculation, but all survived to grow normally. Their dam manifested no clinical symptoms at all after challenge inoculation of them. The higher the titer of virus inoculated into pregnant sows, the higher the neutralizing antibody titer in serum and milk of the sows after farrowing. The puerperal sow which had received two doses of 10(9.3) TCID50 each of attenuated virus by the intramuscular and intranasal route, respectively, presented the highest neutralizing antibody titer of all the inoculated sows. This titer was 2,048 in serum and 14,183 in colostrum immediately after farrowing. In that sow IgG was the main class of immunoglobulins in neutralizing antibody in milk. Even the IgA antibody titer of that sow was higher than that of any other sow which had been administered with virus of low titer. It was 392 and 19 3 and 9 days, respectively, after farrowing.     

Role of primary and secondary maternal viremia in transplacental guinea pig cytomegalovirus transfer.

The modulation of the outcome of intrauterine guinea pig cytomegalovirus (GPCMV) infection by maternal viremia was investigated in the guinea pig model. Virus assay and in situ hybridization were used to study GPCMV infection of maternal blood, placentas, and fetuses following inoculation of pregnant guinea pigs by the subcutaneous, intracardiac, or intranasal route. Animals were inoculated in early gestation and were evaluated every 7 to 10 days throughout pregnancy. Although placental and fetal infections occurred in all groups examined, transfer of GPCMV to placentas and fetuses was most efficient in mothers inoculated subcutaneously. Primary viremia was followed by virus clearance from blood and by an episode of secondary viremia in the three groups of mothers examined. Placental and fetal infections in animals infected subcutaneously or intracardially were first detected at the time of primary viremia, persisted throughout gestation, and increased during secondary viremia. In contrast, placental and fetal infections in animals inoculated intranasally were demonstrated primarily during secondary viremia. Fetal infection was detected in all mothers with detectable primary and secondary viremia but in only 33% of mothers that experienced only primary viremia. These results suggest that secondary maternal viremia is associated with increased placental and fetal GPCMV infections.     

Experimental Maedi Infection in Sheep

Eight sheep were inoculated with Icelandic maedi strain M 88; 2 sheep served as control sheep and were in close contact with the inoculated ones. Four of the sheep were inoculated via the respiratory tract with 7×106 TGID50 of strain M88 and the other 4 intracerebrally with 5×105 TGID50 of the same strain. Maedi M88 strain was isolated from peripheral blood leukocytes of all inoculated sheep. There was a striking difference between the 2 groups in the appearance of demonstrable viremia after inoculation. Viremia could be demonstrated in the intrapulmonarily inoculated sheep within 2–6 months but not until 8–11 months after inoculation in the intracerebrally inoculated ones. This finding is thought most probably to reflect a weak neurotropism of the strain used. After the first demonstration of viremia, maedi virus has been recovered quite reqularly in peripheral leukocytes of all intrapulmonarily inoculated sheep, but less regularly in the intracerebrally inoculated ones. Maedi virus was isolated from 1 of the uninoculated control sheep 15 months after inoculation. The first clinical case with a clinical appearance suggesting combined involvement of maedi and visna was found among the intrapulmonarily inoculated sheep, 8% months after inoculation. Histopathological examination and virus isolation confirmed maedi. The cause of paraplegia could not be confirmed. No histopathological changes were found and no virus isolation was made from the central nervous system of this animal. One of the intracerebrally inoculated sheep died suddenly without any observed clinical signs 11 months after inoculation. Histopathological examination revealed pulmonary lesions of maedi, but no visna lesions in the central nervous system, although maedi virus was isolated from various parts of brain. None of the other experimental sheep displayed clinical signs of maedi or visna during the observation period of 18 months.     

Congenital abnormalities in newborn lambs following Akabane virus infection in pregnant ewes

To clarify the pathogenicity of Akabane virus for ovine embryos, pregnant ewes were inoculated intravenously with the virus. As a result, all of them were affected with viremia and showed an increase in neutralizing antibody 2 weeks after inoculation. The virus was recovered from many organs of embryos which were inoculated with it at 29--45 days of pregnancy and sacrificed 9--30 days later. In particular, some of these embryos which were sacrificed 15 days after inoculation were found suffering from systemic infection. A large quantity of virus was recovered from the organs all over the body of them. No virus, however was recovered from any organ of embryos which were inoculated with the virus at 81 days of pregnancy and sacrificed 30 days later. Abnormal changes were observed in neonatal lambs born from ewes inoculated with the virus at 30--50 days of pregnancy. They were especially severe when the virus was inoculated at 30 days of pregnancy. They consisted of ankylosis of the limbs, scoliosis, hydranencephaly, porencephaly, stillbirth with dwarfism, and death after birth with dwarfism and weakness. Nothing abnormal was found in any neonatal lambs born from ewes inoculated with the virus at 91--101 days of pregnancy. When embryos exceeded 64 days of intra-uterine life more than 29 days after virus inoculation, it was possible to detect immunoglobulin, IgM or IgG or both, and antibody from the serum. Attempts failed to detect either immunoglobulin from embryos less than 59 days of intrauterine life. No IgA was detected from the serum of any embryo. In almost all the neonatal lambs born from ewes inoculated with the virus at 28--101 days of pregnancy, neutralizing antibody was detected from the serum at the time of birth.     

番木瓜抗病突变体阻碍环斑病毒体内运转

应用RT－PCR一步法检测了PRSV Ys株系在感病番木瓜及其抗病突变体植株体内的运转动态,结果表明：在感病植株中,接种后48hr接种叶的未接种部位可检出病毒,第4天部分接种叶柄可检出病毒,第6天植株各部位均能检出病毒;而在抗病植株中,接种后可以而且仅能在接种部位检出病毒;因而认为抗病突变体能够阻碍病毒从接种部位运出及（或）向未接种部位运入。     

Mouse hepatitis virus S in weanling Swiss mice following intranasal inoculation

Three-week-old outbred mice were inoculated intranasally with a mildly pathogenic strain of mouse hepatitis virus (MHV-S). Tissues were analyzed for distribution of infectious virus, lesions, and viral antigen at intervals up to 49 days after inoculation. Sera were tested for neutralizing antibody to MHV-S. Within the first week of infection, virus was isolated from lung and brain of most mice and liver of one mouse, but not from blood, spleen, or intestine. Microscopic lesions consisted of mild olfactory mucosal necrosis, neuronal necrosis of olfactory bulbs and tracts, lymphoplasmacytic infiltrates and vacuolation in the brain, mild nonsuppurative pulmonary perivascular lymphocyte infiltration, focal interstitial pneumonia, and focal necrotizing hepatitis. The presence and distribution of MHV antigen, as determined by indirect immunofluorescence, correlated with virus recovery and acute lesions. No virus or antigen was demonstrable beyond day 7. Serum antibody was first detected on day 10, and titers peaked on day 28 after infection.     

Experimental studies on vertical infection of mice with Japanese encephalitis virus III. Effect of gestation days at the time of inoculation on placental and fetal infection

An experiment was carried out on the effect of gestation days at the time of inoculation on the establishment of experimental vertical infection with Japanese encephalitis virus in mice. In it, mice of the CFW strain in a closed colony were inoculated intravenously with a field strain at different times over a period from 3 to 12 days of gestation. After that, an attempt was made to recover the virus from the placenta and fetus to estimate the rate of infection. As a result, placental infection was established not when the virus was inoculated at 3 days of gestation, but when it was inoculated at 4 days of gestation or later. The rate of infection was relatively high when the virus was inoculated at 6 days of gestation or later. Fetal infection was established relatively frequently when the virus was inoculated some time between 7 and 10 days of gestation, but quite infrequently when the virus was inoculated at any other time than this. There was a difference in rate between placental and fetal infection at a given time of inoculation in days of gestation. This difference seemed to have been induced not by a difference in intensity of viremia appearing after inoculation, but by a difference in degree of development between placental and fetal tissues at the time of inoculation.     

Bovine Epizootic Fever

A virus, the Yamaguchi strain, was serially propagated in suckling hamsters, mice and rats, and hamster kidney BHK21-WI2 cells from a natural case in the 1966 outbreak of bovine epizootic fever, an acute febrile disease of cattle, resembling ephemeral fever, known in Japan since 1949. An acute phase blood from the natural case was first passaged in calves by intravenous inoculation, and a blood specimen at the second passage was used to initiate serial hamster passage. Infected hamsters died with nervous symptoms, and serial passage was readily accomplished by intracerebral inoculation with brain emulsions. The hamster passage line of virus was serially passaged by intracerebral inoculation in 1- or 2-day-old mice, and then in rats 1 or 2 days after birth, which developed fatal encephalitis. The hamster passage virus was also serially propagated with cytopathic effect in cultures of BHK21-WI2 cell cultures. These viral lines were shown to be neutralized by, and to produce specific complement-fixing antigen reactive with, convalescent sera of calves infected with the original Yamaguchi strain, confirming the identity of these lines as the Yamaguchi strain. The hamster passage line, when inoculated intravenously in calves, induced an acute febrile illness which was similar to bovine epizootic fever; all the inoculated calves had viremia and developed neutralizing and complement-fixing antibodies against the virus. Serological evidence for infection with this virus was obtained in natural cases in the 1966 outbreak. These findings seem to justify this virus to be the causative agent of bovine epizootic fever.     

Susceptibility of chickens to avian encephalomyelitis virus. III. Behavior of the virus in growing chicks.

A chick embryo-adapted strain of avian encephalomyelitis virus was inoculated subcutaneously and orally into 40-day-old (middle-aged) and 110-day-old (advanced-aged) chicks to examine the behavior of the virus in the chick body. In the middle-aged chicks, the virus appeared in the muscle at the site of inoculation, liver, spleen, pancreas, lumbar and cervical portions of the spinal cord, and brain 1 approximately 9 days after subcutaneous inoculation, and remained mostly in the central nervous system up to 17 days after the inoculation. The virus was found in large amounts in the muscle at the site of inoculation (10(3.1)), lumbar portion (10(2.5)) and cervical portion (10(2.1)) of the spinal cord, brain (10(1.9)), and in minute amounts in the other organs examined. It appeared in 11 of 21 organs examined. In the middle-aged chicks inoculated by the oral route, the virus was detected transiently in small amounts from esophagus, pancreas, and rectum 4 approximately 14 days after inoculation. In the advanced-aged chicks inoculated by the subcutaneous route, the virus was detected in titer of 10(2.1) approximately 10(3.0) from the muscle at the site of inoculation 2 approximately 7 days after inoculation. The virus was also found sporadically in several organs up to 17 days after inoculation. In the advanced-aged chicks inoculated by the oral route, no virus appeared in any organ, but these chicks turned to be weakly positive for neutralizing antibody in the 4th or later week after inoculation.     

番木瓜抗病突变体阻碍环斑病毒体内运转

应用RT-PCR一步法检测了PRSVYs株系在感病番木瓜及其抗病突变体植株体内的运转动态,结果表明在感病植株中,接种后48hr接种叶的未接种部位可检出病毒,第4天部分接种叶柄可检出病毒,第6天植株各部位均能检出病毒;而在抗病植株中,接种后可以而且仅能在接种部位检出病毒;因而认为抗病突变体能够阻碍病毒从接种部位运出及（或）向未接种部位运入。     

The movement of tobacco mosaic viruses and potato virus X through tomato plants

Tomato aucuba mosaic virus, tobacco mosaic virus and potato virus X took 3'5-4, 5 and 3 days respectively to move from inoculated tomato leaflets into the petioles and stems
On reaching the stem each virus usually first moved downward, but in some plants both upward and downward movement occurred simultaneously and in a few
upward movement occurred first.
All three viruses travelled through the stem at approximately the same rate. Each was capable of travelling more than 80 cm. during the first 12 hr. after entering the stem, giving a minimal average rate of about 8 cm. per hr.
Uninfected pieces of stem invariably occurred between infected pieces. Maximum lengths of stem through which virus particles had apparently passed without causing infection, were 44.5, 49 and 39 cm. for the three viruses.     

Duration of bluetongue viremia in experimentally infected American bison.

Six yearling American bison (Bison bison bison) bulls and one yearling ewe (Ovis aries) were inoculated intradermally and subcutaneously with 2 x 10(5) plaque forming units (pfu) of bluetongue (BT) virus serotype 11. Two uninoculated yearling bison bulls served as negative controls. Blood samples were collected for serology and virus isolation on 0, 4, 7, 11 and 14 days post-inoculation (dpi) and every 2 wk thereafter to 127 dpi. Every 4 wk a new ewe was inoculated with a pooled sample of whole blood from the six infected bison, and each sheep was monitored for 28 days for clinical signs of BT and seroconversion. Bluetongue viremia was detected in all six inoculated bison starting at 4 to 28 dpi and was no longer detectable from 42 dpi onward. Pooled blood samples collected at 28, 56, 84 and 112 dpi from the six infected bison were not infectious for sheep. The six infected bison seroconverted by 11 to 28 dpi on a competitive enzyme-linked immunosorbent assay and by 28 dpi on the serum neutralization test, and all remained seropositive thereafter. No clinical signs or lesions attributable to BT were observed in the infected bison or controls. There was evidence that a small amount of epizootic hemorrhagic disease virus type 2 had been present in the BT virus inoculum; reasons are given for concluding that this did not affect the results of the BT study.     

人巨细胞病毒AD169株感染家兔致病机理的初步研究

本文试用家兔作HCMV感染致病机制模型研究,用家兔荧光法及病毒再分离技术考证了感染期间的病毒血症动态。观察到兔在原发性病毒感染后的第13无病毒首先在单核细胞(MC)、淋巴细胞(LC)中显现,并向血浆排放病毒,进而随血道播散至全身组织,引起相应靶器官感染致病。     

Pathogenicity and distribution of avian nephritis virus (G-4260 strain) in inoculated laying hens

Specific-pathogen-free laying hens were inoculated intravenously with the G-4260 strain of avian nephritis virus (ANV). The distribution of the virus in organs, histological changes in main organs, the condition of laying, and egg transmission of the virus were examined in them. Over an experimental period of 27 days, no clinical sings were observed. In a chronological study on the distribution of the virus in organs, the virus was recovered from liver, kidney, jejunum, and rectum for 6 days postinoculation (PI). The virus titer in organ emulsion was the highest in the jejunum of all the main organs. The virus was recovered from the kidney for 8 days PI, although it was not so high in this organ. It was not recovered from the ovary or oviduct. Fluorescent antigens were not observed at all in any material. In a pathological examination, some local inflammatory changes were observed only in the kidney. There were no significant changes in the ovary, oviduct, or any other organ. Antibody appeared 10 days PI and was detectable even 27 days PI, although it was not so high in titer. There was no significant difference in the rate of egg-production between the infected and the sham inoculated groups. No virus was isolated from 111 fertile eggs laid by infected hens over a period from 2 to 27 days PI.     

Animal model of mucosally transmitted human immunodeficiency virus type 1 disease: intravaginal and oral deposition of simian/human immunodeficiency virus in macaques results in systemic infection, elimination of CD4+ T cells, and AIDS.

Chimeric simian/human immunodeficiency virus (SHIV) consists of the env, vpu, tat, and rev genes of human immunodeficiency virus type 1 (HIV-1) on a background of simian immunodeficiency virus (SIV). We derived a SHIV that caused CD4+ cell loss and AIDS in pig-tailed macaques (S. V. Joag, Z. Li, L. Foresman, E. B. Stephens, L. J. Zhao, I. Adany, D. M. Pinson, H. M. McClure, and O. Narayan, J. Virol. 70:3189-3197, 1996) and used a cell-free stock of this virus (SHIV(KU-1)) to inoculate macaques by the intravaginal route. Macaques developed high virus burdens and severe loss of CD4+ cells within 1 month, even when inoculated with only a single animal infectious dose of the virus by the intravaginal route. The infection was characterized by a burst of virus replication that peaked during the first week following intravenous inoculation and a week later in the intravaginally inoculated animals. Intravaginally inoculated animals died within 6 months, with CD4+ counts of <30/microl in peripheral blood, anemia, weight loss, and opportunistic infections (malaria, toxoplasmosis, cryptosporidiosis, and Pneumocystis carinii pneumonia). To evaluate the kinetics of virus spread, we inoculated macaques intravaginally and euthanized them after 2, 4, 7, and 15 days postinoculation. In situ hybridization and immunocytochemistry revealed cells expressing viral RNA and protein in the vagina, uterus, and pelvic and mesenteric lymph nodes in the macaque euthanized on day 2. By day 4, virus-infected cells had disseminated to the spleen and thymus, and by day 15, global elimination of CD4+ T cells was in full progress. Kinetics of viral replication and CD4+ loss were similar in an animal inoculated with pathogenic SHIV orally. This provides a sexual-transmission model of human AIDS that can be used to study the pathogenesis of mucosal infection and to evaluate the efficacy of vaccines and drugs directed against HIV-1.     

Herpesvirus simiae (B virus) antibody response and virus shedding in experimental primary infection of cynomolgus monkeys.

Four cynomolgus monkeys (Macaca fascicularis) were inoculated in the lips and tongues with B virus. Virus shedding and antibody responses were monitored for up to 50 days postinfection. Virus was isolated from the oral cavities of all monkeys at 6 days postinfection despite the absence of observable lesions. Virus was not isolated from genital swabs or serum. Antibodies to both B virus and herpes simplex virus were detected by neutralization between days 8 and 12. Virus-specific IgM and IgG antibodies were measured by antibody capture radioimmunoassay. IgM was first detected on day 6; by contrast, IgG did not appear until day 12. Antibodies reactive in a competitive radioimmunoassay appeared by day 12 and peaked at 30 to 40 days postinfection. This study provides data on which to base the diagnosis of primary B virus infection in cynomolgus monkeys.     

Resistance of Pepper Lines to the Movement of Cucumber Mosaic Virus

The multiplication and the migration of cucumber mosaic virus (CMV) were studied in greenhouse conditions in one susceptible ‘Yolo wonder’ and two resistant ‘Milord’ and ‘Vania’ pepper varieties. DAS-ELISA tests have revealed that the virus is replicated in inoculated leaves of the resistant varieties as high as in the susceptible variety. In the susceptible variety ‘Yolo wonder’, CMV migrated from the leaf lamina to the petiole two days after inoculation and it became systemic three days later regardless the season. In ‘Milord’ the virus migrated from the leaf lamina to the petiole five days after inoculation and it became systemic during the winter 16 days after inoculation. Whereas plants of the same genotype were not infected systemically during the summer. In ‘Vania’, during the two seasons, CMV spread from the blade to the petiole five days after inoculation, but the virus was not detected beyond the inoculated leaf. These results show that ‘Milord’ and ‘Vania’ are resistant to CMV migration. Therefore, the resistance to CMV migration is affected by plant genotype and temperature. The study of effect of pepper plant phenology on infection has revealed that resistance to CMV migration is also affected by the development stage of the plants.