Host Range In Culture Research Articles

Host range of Canine minute virus in cell culture

Canine minute virus (CnMV) is a member of the Bocavirus genus, together with Bovine parvovirus (BPV), which emerged as a new pathogen of dogs in 1967. The genus Bocavirus gained more recognition after the recent identification of Human bocavirus in pooled specimens from the respiratory tract of children. The cell culture host range of CnMV appears to be restricted to the Walter Reed canine cell (WRCC) line, although there is a report that indicates susceptibility of the Madin-Darby canine kidney (MDCK) cell line. In order to study the susceptibility of different cell lines to CnMV, the replication in cell cultures of canine, bovine, and human origin and the interaction of the virus with freshly isolated canine peripheral blood mononuclear cells were evaluated. The in vitro host range was unexpectedly wide. As shown by indirect fluorescent antibody and polymerase chain reaction assays, CnMV replicates efficiently in the A72 and MDCK canine cell lines. Bovine and human cell lines support the replication of CnMV less efficiently. In contrast, canine mononuclear blood cells are permissive to replication of CnMV in vitro. The present study revealed the ability of CnMV to replicate in continuous cell lines of different origin and, partially, in canine mononuclear cells.

Evolution of the feline-subgroup parvoviruses and the control of canine host range in vivo

A related group of parvoviruses infects members of many different carnivore families. Some of those viruses differ in host range or antigenic properties, but the true relationships are poorly understood. We examined 24 VP1/VP2 and 8 NS1 gene sequences from various parvovirus isolates to determine the phylogenetic relationships between viruses isolated from cats, dogs, Asiatic raccoon dogs, mink, raccoons, and foxes. There were about 1.3% pairwise sequence differences between the VP1/VP2 genes of viruses collected up to four decades apart. Viruses from cats, mink, foxes, and raccoons were not distinguished from each other phylogenetically, but the canine or Asiatic raccoon dog isolates formed a distinct clade. Characteristic antigenic, tissue culture host range, and other properties of the canine isolates have previously been shown to be determined by differences in the VP1/VP2 gene, and we show here that there are at least 10 nucleotide sequence differences which distinguish all canine isolates from any other virus. The VP1/VP2 gene sequences grouped roughly according to the time of virus isolation, and there were similar rates of sequence divergence among the canine isolates and those from the other species. A smaller number of differences were present in the NS1 gene sequences, but a similar phylogeny was revealed. Inoculation of mutants of a feline virus isolate into dogs showed that three or four CPV-specific differences in the VP1/VP2 gene controlled the in vivo canine host range.

Interferon-mediated persistent infection of Saint Louis encephalitis virus in a reptilian cell line.

A persistent infection with Saint Louis encephalitis (SLE) virus in a poikilothermic cell line TH-1 (turtle heart cells) was studied. Infected TH-1 cells were subcultured weekly at 31 degrees C for 1 year and continued to produce low levels (10(2) to 10(3) p.f.u./ml) of virus without obvious cytopathic effects or marked cyclic events. Indirect fluorescent antibody and infectious centre assays indicated that less than 1% of the cells were producing detectable virus proteins or infectious virus. Defective-interfering particles, temperature-sensitive mutants and DNA provirus were not detected. Interferon (IFN) mediation of the persistent infection as considered since the persistently infected cells (PIC) and normal TH-1 cells were resistant to heterologous virus challenge after treatment with virus-free culture fluid from PIC. A direct relationship was found between the m.o.i. and the amount of IFN produced, plateauing at an m.o.i. of approx. 10. The reptilian IFN was physically and chemically similar to mammalian and avian IFN. Certain biological markers of the SLE virus changed during the persistent infection. It was less virulent for mice, showed distinct differences in cell culture host range and had increased thermal lability.

Surface Antigens on Transplantable Tumor Cell Lines Producing Mouse Type C Viruses

A variety of transplantable mouse tumor lines were shown to contain murine type C viruses and virus-associated antigens. The type of virus isolated and antigens detected could not invariably be correlated with the original method of tumor induction, but testing of the majority of tumor lines for infectious virus at various levels of in vivo or in vitro passage yielded isolates that were consistent in tissue culture host range for each tumor. In contrast, during the course of in vivo transplantation, some of the lines underwent considerable change in the pattern of virus-associated cell-surface antigens. When the transplanted tumor lines were placed into culture, all showed some alteration in the detectable surface antigens. Upon retransplantation and passage of the cultured cells in mice, the surface antigens gradually returned to the original in vivo patterns and occasionally acquired additional type C virus-associated antigens not detected in the original tumor line. To test for association of antigens with infectious virus, appropriate tissue culture cell lines were infected with the viruses isolated from the tumors. In these infected indicator cells, some new virus-associated cell-surface and virion evelope antigens were detected, but the complete array of antigens found in the original tumor lines was not acquired. These findings indicated the presence of several different type C viruses in long transplanted cell lines and demonstrated that environmental and host cell factors may have major influences on expression of virus-associated antigens.

On Coniothyrium minitans and its parasitism of Sclerotinia species

Coniothyrium minkans is a hyperparasite of sclerotia of Sclerotinia sclerotiorum and, S. trifoliorum known from the U.S.A., Europe and New Zealand. Its host range in culture includes Sclerotinia minor and some strains of Botrytis cinerea, B. fabae and Sclerotium cepivorum . Inoculation experiments and general observations indicate that it is not pathogenic to green plants. The optimum temperature for growth on agar and for infection of S. sclerotiorum sclerotia is 20 ° but good growth and parasitism occur at 10 ° . Using a standardized infection test with a comparatively low concentration of C. minkans spores great variability is demonstrated in the susceptibility of different isolates of S. sclerotiorum . Sclerotia produced in agar culture are markedly more resistant to infection than those grown on autoclaved carrots. Application of inoculum in the form of pycnidial dust to sclerotia placed on compost results in high levels of infection.

Studies on Variation in Coxsackie A-9 Virus

Summary After 6 to 14 serial passages of Coxsackie A-9 virus in x-irradiated patas cultures, a strain was obtained which a) multiplied in patas cultures, b) was reduced in virulence for new born mice, and c) produced only small plaques (5 mm at 7 days) on both rhesus and patas monolayers. A single passage of the adapted virus either in mice or in rhesus cultures (both in fluid medium and under agar), shifted the virus population toward the original large plaque type and tissue culture host range. Reversion to the large plaque type was observed after 4–8 hr growth (single growth cycle) when the adapted virus at limiting dilutions was transferred to rhesus cultures. However, if harvests were made after 24–48 hr a mixed plaque size population was obtained. This was attributed to a slower growth rate in the adapted virus.