Simian virus 40 sequences in blood specimens from healthy individuals of Casale Monferrato, an industrial town with a history of asbestos pollution

Our plain-English summary of Simian virus 40 sequences in blood specimens from healthy individuals of Casale Monferrato, an industrial town with a history of asbestos pollution, by C. Pancaldi, V. Balatti, R. Guaschino, et al (The Journal of Infection, 2009).

The study

• Authors: C. Pancaldi, V. Balatti, R. Guaschino, F. Vaniglia, A. Corallini, F. Martini, L. Mutti, M. Tognon
• Journal: The Journal of Infection
• Published: 2009;58(1):53-60
• Cited by: 26 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objective: Asbestos is considered the main agent in causing the onset of the malignant pleural mesothelioma (MM), a fatal cancer of increasing incidence worldwide. Other factors may contribute to the onset/progression of MM, such as genetic predisposition and infection by oncogenic viruses, like simian virus 40 (SV40). SV40 was administered to human populations mainly with SV40-contaminated anti-polio vaccines. SV40 footprints have been detected in specific human tumours, including MM, and in healthy blood donors. The aim of this study was to verify the presence of SV40 sequences in buffy coats of healthy blood donors, inhabitants of Casale Monferrato, where MM is 10 times more prevalent compared to other areas.

Methods: DNA from 148 buffy coats of healthy blood donors were qualitatively and quantitatively PCR analyzed for SV40 sequences.

Results: SV40 sequences were detected in 24 out of 148 (16%) samples. Quantitative real time PCR analyses carried out in SV40-positive samples indicated a viral copy number in the range of 10-10,000 per 100,000 cells.

Conclusions: SV40 sequences are present in blood samples of healthy donors from Casale Monferrato with a prevalence similar to that reported in previous investigations of healthy donors from asbestos-free areas. Altogether these data suggest that SV40 is circulating in the human population.

In plain English

This laboratory study looked for DNA of simian virus 40 (SV40), a monkey virus, in blood from 148 healthy blood donors in Casale Monferrato, an Italian town with a history of asbestos pollution and a high rate of malignant pleural mesothelioma. The samples were collected over about two months in 2006. Using nested PCR, the authors found SV40 sequences in 24 of 148 samples (16%). Rates in the different age groups ranged from 14.3 to 25%, with no statistically significant differences between them. Of the 24 positive samples, 16 were also positive for a second region of the virus and 17 for a third. In the 22 positive samples that were measured, viral amounts ranged from 10 to 10,000 copies per 100,000 cells. A commercial DNA extraction kit, used on 37 samples, found only 5% positive. The authors did not measure asbestos in the donors' blood. They concluded that the SV40 rate did not differ substantially from some earlier studies in Italy, Japan and the USA and was lower than in other studies, and that their results suggest SV40 is circulating in the human population.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory molecular epidemiology survey: blood samples tested for SV40 DNA by PCR. There was no comparison group within the study; results were compared with earlier published studies.
• Who was studied: 148 healthy blood donors living in Casale Monferrato, Italy. Buffy coats (white blood cell fractions) were collected at the local transfusion centre over about two months in 2006. Ages ranged from 20 to 69.
• Exposure: Residence in Casale Monferrato, a town the authors describe as heavily exposed to asbestos until 1986 because of an asbestos cement factory. No fiber type is named, and individual asbestos exposure was not measured. The quantity actually measured was SV40 DNA in blood.
• Main results:
  • SV40 large T antigen (Tag) sequences were found in 24 of 148 blood samples (16%).
  • By age group, the share of positive samples ranged from 14.3% to 25%, with no statistically significant differences between age groups.
  • Of the 24 Tag-positive samples, 16 were also positive for the Tag intron region, a test the authors used to reduce the risk of false positives from laboratory plasmid contamination.
  • Of the 24 Tag-positive samples, 17 were also positive for the SV40 regulatory region.
  • Nine randomly selected regulatory-region sequences all matched the wild-type SV40 776 strain.
  • In 22 positive samples measured by real-time quantitative PCR, all were confirmed positive. Copy numbers ranged from 10 to 10,000 (printed as "104" through scanning damage; Table 3 confirms 10,000). Of these 22 samples, 9 had 10 to 100 copies, 8 had 100 to 1000, 4 had 1000 to 10000, and 1 had 10000.
  • One of the 22 measured samples had a high viral load, about one viral copy per 10 cells.
  • In 37 randomly chosen samples extracted with a commercial kit, only 5% were SV40-positive, compared with 16% using the chemical (phenol-chloroform-isoamyl alcohol) extraction method.
• The authors' conclusion: The authors concluded that, despite the asbestos pollution, the SV40 prevalence in healthy blood donors from Casale Monferrato did not differ substantially from that reported in some earlier studies in Italy, Japan and the USA, and was lower than in other studies. They wrote that asbestos in the environment did not favour the spread of SV40 infection, at least among the donors studied. They wrote that their results suggest the SV40 virus is circulating in the human population.
• Limitations the authors state:
  • The level of asbestos in the donors' blood samples was not analyzed.
  • Because DNA came from frozen buffy coats, the authors could not check whether the virus was replicating in the sample with the high viral load.
  • Differences in sample size and in DNA extraction and PCR methods between studies may explain differing SV40 prevalence figures, which affects comparison with earlier studies.

Topics

Medical terms in this study, explained in our Lexicon: Casale Monferrato, Pleural Mesothelioma, SV40.

Related studies

• Simian virus 40 transformation, malignant mesothelioma and brain tumors — F. Qi, M. Carbone, et al. (2011)
• Evaluation of simian virus-40 as a biological prognostic factor in Egyptian patients with malignant pleural mesothelioma — A.R. Zekri, A.A. Bahnassy, et al. (2007)
• Human mesotheliomas contain the simian virus-40 regulatory region and large tumor antigen DNA sequences — H.I. Pass, J.S. Donington, et al. (1998)
• Evidence against a role for SV40 infection in human mesotheliomas and high risk of false-positive PCR results owing to presence of SV40 sequences in common laboratory plasmids — F. López-Ríos, P.B. Illei, et al. (2004)
• Mesothelioma mortality in Europe: impact of asbestos consumption and simian virus 40 — K. Leithner, A. Leithner, et al. (2006)
• No association between simian virus 40 and diffuse malignant mesothelioma of the pleura in Iranian patients: a molecular and epidemiologic case-control study of 60 patients — Z. Mohammad-Taheri, S.A. Nadji, et al. (2013)

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