Characterisation of a polyomavirus in two foetal rhesus monkey kidney cell lines used for the growth of hepatitis A virus

Association Between Simian Virus 40 and Human Tumors

Simian virus 40 (SV40) is a small DNA tumor virus of monkey origin. This polyomavirus was administered to human populations mainly through contaminated polio vaccines, which were produced in naturally infected SV40 monkey cells. Previous molecular biology and recent immunological assays have indicated that SV40 is spreading in human populations, independently from earlier SV40-contaminated vaccines. SV40 DNA sequences have been detected at a higher prevalence in specific human cancer specimens, such as the brain and bone tumors, malignant pleural mesotheliomas, and lymphoproliferative disorders, compared to the corresponding normal tissues/specimens. However, other investigations, which reported negative data, did not confirm an association between SV40 and human tumors. To circumvent the controversies, which have arisen because of these molecular biology studies, immunological researches with newly developed indirect ELISA tests were carried out in serum samples from patients affected by the same kind of tumors as mentioned above. These innovative indirect ELISAs employ synthetic peptides as mimotopes/specific SV40 antigens. SV40 mimotopes do not cross-react with the homologous human polyomaviruses, BKPyV, and JCPyV. Immunological data obtained from indirect ELISAs, using SV40 mimotopes, employed to analyze serum samples from oncological patients, have indicated that these sera had a higher prevalence of antibodies against SV40 compared to healthy subjects. The main data on (i) the biology and genetics of SV40; (ii) the epidemiology of SV40 in the general population, (iii) the mechanisms of SV40 transformation; (iv) the putative role of SV40 in the onset/progression of specific human tumors, and (v) its association with other human diseases are reported in this review.

Genome Sequence of Bovine Polyomavirus 1 Detected in a Salers Cow (Bos taurus) from Catalonia, Spain

We identified a variant of the first bovine polyomavirus (BPyV1; family Polyomaviridae) in a lymph node of a Salers cow. As the 2 previously published genome sequences of this virus originated from fetal bovine serum and ground beef, respectively, this is the first BPyV1 genome that could be traced back to an individual.

Hamburger polyomaviruses

Epidemiological studies have suggested that consumption of beef may correlate with an increased risk of colorectal cancer. One hypothesis to explain this proposed link might be the presence of a carcinogenic infectious agent capable of withstanding cooking. Polyomaviruses are a ubiquitous family of thermostable non-enveloped DNA viruses that are known to be carcinogenic. Using virion enrichment, rolling circle amplification (RCA) and next-generation sequencing, we searched for polyomaviruses in meat samples purchased from several supermarkets. Ground beef samples were found to contain three polyomavirus species. One species, bovine polyomavirus 1 (BoPyV1), was originally discovered as a contaminant in laboratory FCS. A previously unknown species, BoPyV2, occupies the same clade as human Merkel cell polyomavirus and raccoon polyomavirus, both of which are carcinogenic in their native hosts. A third species, BoPyV3, is related to human polyomaviruses 6 and 7. Examples of additional DNA virus families, including herpesviruses, adenoviruses, circoviruses and gyroviruses were also detected either in ground beef samples or in comparison samples of ground pork and ground chicken. The results suggest that the virion enrichment/RCA approach is suitable for random detection of essentially any DNA virus with a detergent-stable capsid. It will be important for future studies to address the possibility that animal viruses commonly found in food might be associated with disease.

Simian virus 40 in humans

Simian virus 40 (SV40) is a monkey virus that was administered to human populations by contaminated vaccines which were produced in SV40 naturally infected monkey cells. Recent molecular biology and epidemiological studies suggest that SV40 may be contagiously transmitted in humans by horizontal infection, independently from the earlier administration of SV40-contaminated vaccines.SV40 footprints in humans have been found associated at high prevalence with specific tumor types such as brain and bone tumors, mesotheliomas and lymphomas and with kidney diseases, and at lower prevalence in blood samples from healthy donors. Contrasting reports appeared in the literature on the circulation of SV40 in humans by contagious transmission and its association, as a possible etiologic cofactor, with specific human tumors. As a consequence of the conflicting results, a considerable debate has developed in the scientific community. In the present review we consider the main results obtained by different groups investigating SV40 sequences in human tumors and in blood specimens, the putative role of SV40 in the onset/progression of specific human tumors, and comment on the hypotheses arising from these data.

Detection and molecular characterisation of bovine polyomavirus in bovine sera in New Zealand

AIM

To investigate the prevalence of bovine polyomavirus (BPyV) DNA in commercial batches of bovine serum products, cell lines and cattle in New Zealand and to characterise the viral DNA detected.

METHODS

Two nested polymerase chain reaction (PCR) assays were applied to detect BPyV in bovine sera. One was used to screen for the VP1 gene of BPyV DNA in: 140 batches of commercial bovine serum products, including 66 batches of fetal bovine serum (FBS), 34 batches of calf serum, and 40 batches of adult bovine serum (ABS)/plasma; 112 individual adult bovine sera; and 16 cell lines of various species origin. Fifty batches of serum samples were also tested, using the second nested PCR assay that screened for the Large T gene. Restriction fragment length polymorphism (RFLP) was conducted with 36 PCR products amplified from the VP1 gene of BPyV using EcoRI. Five selected VP1 PCR products were subjected to DNA sequencing and phylogenetic analysis.

RESULTS

BPyV DNA was detected in 46 (70%) batches of FBS, 11 (32%) batches of calf sera and two (5%) batches of ABS/plasma, an overall prevalence of 42%. None of 112 adult bovine sera was BPyV-positive. RFLP analysis demonstrated a uniform digestion pattern in the majority (31/36) of amplicons tested, while the remaining PCR amplicons did not show enzyme cleavage. Sequence analysis of the PCR products (a 263 base pair (bp) fragment of the VP1 gene) obtained from five batches of FBS showed 96.2-98.9% homology to that of published sequences of BPyV.

CONCLUSION

BPyV is a frequent contaminant of commercial bovine serum in New Zealand. The incidence of BPyV in adult bovine serum products is much lower than in FBS and calf serum. Genomic variations exist among different viruses. The clinical significance of the high prevalence of BPyV DNA in bovine serum products is yet to be determined.

Characterization of a new polyomavirus (Polyomavirus papionis-2) isolated from baboon kidney cell cultures

Viruses with papovavirus morphology were seen in fluids from baboon kidney cell cultures on three separate occasions (isolates A, B, and C). The size of the virions, 47.9 nm, placed the virus in the polyomavirus genus. It grew well in baboon kidney and Vero cells and less well in human embryo lung (HEL) fibroblasts. The virus could not be identified as the previously described baboon polyomavirus, SA 12, or as any of the other known primate polyomaviruses BK, JC or SV 40, the non-primate viruses mouse polyoma, K, rabbit kidney vacuolating virus (RKV) or bovine polyomavirus (FRKV) by immunofluorescence, immune electron microscopy or hemagglutination inhibition (HI) tests. A rabbit antiserum to the new virus (isolate A) reacted only with the three isolates and not with the other primate polyomaviruses studied. Thirteen percent of 118 wild-caught baboons (Papio anubis) had HI antibody to the new polyomavirus and 21 percent were seropositive for SA 12; only two baboons had antibody to both viruses. These results suggest that in baboons there are two antigenically distinct polyomaviruses which circulate independently. The two viruses may also be distinguished by their hemagglutinating properties: SA 12 agglutinated erythrocytes from a wider range of species but only the newly recognized polyomavirus agglutinated baboon erythrocytes. We propose that the two baboon viruses, SA 12 and the new virus, should be named Polyomavirus papionis-1 and Polyomavirus papionis-2 respectively.

Enhancement of hepatitis A propagation in tissue culture with 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole

The adenosine analog 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB) was found to increase the production of hepatitis A (HAV) antigen in two monkey kidney cell lines (Frhk-4 and Vero cells). DRB, a known inhibitor of the synthesis of messenger RNA, caused moderate changes in cell morphology. However, Frhk-4 cells could be maintained for several weeks at 80 microM of DRB, the concentration that caused maximal enhancement on HAV. DRB should be present from about the time of virus inoculation and its strongest effect was seen at low multiplicities of infection. Using radioimmunofocus assay it could be shown that DRB increased the amount of infectious virus. DRB treatment was applied in primary isolation of HAV from feces. In nine of ten strains HAV antigen expression was strongly increased and in six of the ten strains infectivity of harvested material increased by one 10log or more. DRB thus seems to be a useful enhancer of HAV growth in tissue culture.

Cytopathology, plaque assay, and heat inactivation of hepatitis A virus strain HM175

Hepatitis A virus (HAV) strain HM175 derived after repeated subculture of persistently infected B-SC-1 cells caused a specific cytopathic effect upon acute infection of B-SC-1 cells. The virus formed visible plaques on B-SC-1 cell monolayers after 9 to 14 days of incubation at 34 degrees C, and virus can therefore be titrated by plaque assay. Virus could be re-isolated from plaques of infected cells, which allows the clonal isolation of HAV variants. The stability of a plaque-purified variant of HAV at elevated temperatures exceeded that of poliovirus type 1, but this variant is less stable than previously reported strains of HAV.

Human exposure to bovine polyomavirus: a zoonosis?

A competitive-type solid phase radioimmunoassay (RIA) was developed for the detection of antibody to bovine polyomavirus. Comparison of RIA and counter-immunoelectrophoresis (CIE) results on 273 cattle sera indicated that both techniques were detecting antibody of like specificity. Human sera from 256 blood donors, 219 people recently vaccinated against polio, rubella or rabies, 50 immunosuppressed patients and 472 people with various occupational exposure to cattle were tested for antibody to bovine polyomavirus, the foetal rhesus monkey kidney strain, (anti-FRKV) by RIA. Apart from one blood donor and one of 108 rabies vaccinees only those in close contact with cattle possessed anti-FRKV. Compared with 62 per cent seropositive in the natural hosts, cattle, 71 per cent of veterinary surgeons, 50 per cent of cattle farmers, 40 per cent of abattoir workers, 16 per cent of veterinary institute technical staff and 10 per cent of veterinary students were anti-FRKV positive. Our findings indicate that the theoretical hazard of FRKV infection from undetected contamination of current tissue culture derived vaccines may, in practice, be remote. Proposed wider use of primate kidney cells as substrates for new vaccines may increase this risk.

Attempted isolation of viruses from myasthenia gravis thymus

A systematic study of thymus homogenates and cell suspensions from 13 patients with myasthenia gravis (MG) of recent onset, and 6 non-myasthenic controls, has failed to detect or isolate virus by cell culture with 'rescue techniques', electron microscopy, or intracerebral inoculation into neonatal mice. These results do not support the case for persistent viral infection in the thymus, and impose constraints on hypotheses of a viral aetiology of MG.