Persistent infection of a lymphoma cell line by herpes simplex virus.

The peripheral blood cells from a patient with a B-cell lymphoma were established in long-term tissue culture. Two years after establishment of the cells in culture they were infected with herpes simplex virus type 2 and the productivity and duration of viral persistence investigated. One week after infection the lymphoblastoid cells were productively infected and have remained so for a period of over 3 years. Expression of a viral glycoprotein antigen was evaluated by using a fluorescein-labeled monoclonal anti-herpes simplex virus type 2 antibody and revealed a spectrum of staining reactions grading from a lightly stippled to very intense pattern. Polymerase chain reaction analysis of the infected cells revealed the presence of the herpes simplex virus type 2 DNA polymerase gene in the infected cells that was absent from the uninfected lymphoblastoid cells. These results taken together with the long-term growth characteristics of both the infected and uninfected lymphoblastoid cells suggest that this cell line may be a good model system for studying viral infection, viral replication, viral latency, and clinical application for the isolation of human herpes virus.

Triazole Seed Treatments Suppress Spore Production by Puccinia recondita, Septoria tritici, and Stagonospora nodorum from Wheat Leaves.

Treatments of winter wheat seed with the systemic triazole fungicides triadimenol (31 g a.i./100 kg = Baytan 30F at 1.5 fl oz/cwt) and difenoconazole (24 g a.i./100 kg = Dividend 3FS at 1.0 fl. oz/cwt) were tested for effect on asexual sporulation by Puccinia recondita, Septoria tritici, and Stagonospora nodorum. Spore production was measured on seedlings grown in a growth chamber (24°C day/15°C night, 12-h photoperiod) and inoculated with the pathogens 3, 5, or 7 weeks after sowing. Spore production was converted to a percentage of the non-treated control and regressed against weeks after planting when plants were inoculated. Linear models fit data for both fungicides against all three pathogens. According to the models, difenoconazole suppressed sporulation levels of P. recondita and Septoria tritici to 10% of the levels on plants from non-treated seed for about 3 weeks after sowing. Spore production for all three fungi was suppressed to 25% of the non-treated level for at least 4.2 weeks and to 50% for at least 6.5 weeks. Similarly, triadimenol suppressed all three pathogens to 50% of the non-treated level for at least 3.2 weeks. The two fungicides showed similar effects against S. tritici; however, difenoconazole showed significantly greater suppression of sporulation by P. recondita and Stagonospora nodorum compared with triadimenol. Responses occurred even though large concentrations of spores were used to inoculate plants and environmental conditions were optimized for spore production. Reduced sporulation should help protect fall-planted wheat seedlings and may significantly delay epidemics in the following spring.

Isolation of parainfluenza virus type 3 from cerebrospinal fluid associated with aseptic meningitis.

Parainfluenza virus type 3 has been isolated from the cerebral spinal fluid (CSF) from six individuals--four children and two adults--over a 10-year period. All had fever, and four had signs of meningitis. All recovered uneventfully, including one child undergoing chemotherapy for medulloblastoma. The clinical presentation of this child who developed parainfluenza virus type 3 meningitis is described, and the cases of five other individuals with parainfluenza virus type 3 isolated from the CSF are briefly reviewed. The paramyxovirus parainfluenza type 3, in addition to mumps virus, may be considered capable of infecting the central nervous system.

Enhanced infectivity of bluetongue virus in cell culture by centrifugation.

The effects of centrifugation of the infection of cell culture with bluetongue virus (BTV) were investigated. Baby hamster kidney cells were infected with BTV with or without centrifugation. Viral antigen was detected by immunofluorescence at 24 h in both centrifuged and noncentrifuged cultures. However, after 24 h of infection, the production of PFU in centrifuged cell cultures was 10- to 20-fold greater than that seen in cultures not centrifuged. In addition, centrifugation enhanced the direct detection of PFU from blood samples collected from a sheep experimentally infected with BTV.

In vitro neutralization of antigenic variants of bluetongue virus is related to in vivo protection.

Neutralization resistant variants of bluetongue virus serotype 10 were selected with a neutralizing monoclonal antibody. Three variants were selected for further characterization. One of these variants was completely resistant to neutralization, while the other two variants showed intermediate resistance to neutralization as compared to the parent virus. The completely resistant variant failed to bind the selecting monoclonal antibody as determined by immune precipitation and enzyme linked immunosorbent assay; whereas, the other two variants bound antibody to a similar extent as the parent virus as determined by these tests. The ability of the variants to bind monoclonal antibody correlated with passive protection in the newborn mouse model. These results indicate that the ability of the virus to bind antibody is directly related to in vivo protection and that in vitro neutralization and in vivo protection are also related.

Interference to oral superinfection of Aedes triseriatus infected with La Crosse virus.

Aedes triseriatus orally infected with a temperature-sensitive mutant of La Crosse virus were, at predetermined times post-infection, orally challenged with wild type La Crosse or Tahyna virus. Most mosquitoes challenged with wild type La Crosse virus within 24 hr of ingestion of the temperature-sensitive virus became superinfected. In contrast, the majority of mosquitoes challenged at 72 hr were resistant to superinfection. Mosquitoes challenged at 7 days or thereafter were refractory to superinfection with La Crosse or Tahyna virus. The onset of interference was correlated with virus titer and antigen expression in midgut cells.

A G1 glycoprotein epitope of La Crosse virus: a determinant of infection of Aedes triseriatus.

Arthropod-borne viruses (arboviruses) have specific vector-vertebrate host cycles in nature. The molecular basis of restriction of virus replication to a very limited number of vector species is unknown, but the present study suggests that viral attachment proteins are important determinants of vector-virus interactions. The principal vector of La Crosse (LAC) virus is the mosquito Aedes triseriatus, and LAC virus efficiently infects the mosquito when ingested. However, a variant (V22) of LAC virus, which was selected by growing the virus in the presence of a monoclonal antibody, was markedly restricted in its ability to infect Ae. triseriatus when it was ingested. Only 15% of the mosquitoes that ingested V22 became infected and 5% of these developed disseminated infections. In contrast, 89% of the mosquitoes that ingested LAC became infected and 74% developed disseminated infections. When V22 was passed three times in mosquitoes by feeding, a revertant virus, V22M3, was obtained that infected 85% of Ae. triseriatus ingesting this virus. In addition, V22M3 regained the antigenic phenotype and fusion capability of the parent LAC virus. These results suggest that the specificity of LAC virus-vector interactions is markedly influenced by the efficiency of the fusion function of the G1 envelope glycoprotein operating at the midgut level in the arthropod vector.

Evolution of bunyaviruses by genome reassortment in dually infected mosquitoes (Aedes triseriatus).

Aedes triseriatus mosquitoes became dually infected after ingesting two mutants of LaCrosse (LAC) virus simultaneously or after ingesting, by interrupted feeding, the two viruses sequentially within a 2-day period. After 2 weeks of incubation, approximately 25 percent of the vectors contained new virus genotypes as the result of RNA segment reassortment. New viruses were transmitted when the mosquitoes fed on mice. Viruses ingested more than 2 days after the initial infecting virus did not cause superinfection of the mosquito vectors.