Simian virus 40 is present in human lymphomas and normal blood

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.

Viral microRNA effects on persistent infection of human lymphoid cells by polyomavirus SV40

BACKGROUND

Polyomaviruses, including simian virus 40 (SV40), display evidence of lymphotropic properties. This study analyzed the nature of SV40-human lymphocyte interactions in established cell lines and in primary lymphocytes. The effects of viral microRNA and the structure of the viral regulatory region on SV40 persistence were examined.

RESULTS

SV40 DNA was maintained in infected B cell and myeloid cell lines during cell growth for at least 28 days. Limiting dilution analysis showed that low amounts of SV40 DNA (~2 copies per cell) were retained over time. Infected B cells remained viable and able to proliferate. Genome copies of the SV40 microRNA-null mutant persisted at higher levels than the DNA of wild-type viruses. Complex viral regulatory regions produced modestly higher DNA levels than simple regulatory regions. Viral large T-antigen protein was detected at low frequency and at low levels in infected B cells. Following infection of primary lymphocytes, SV40 DNA was detected in CD19+ B cells and CD14+ monocytes, but not in CD3+ T cells. Rescue attempts using either lysates of SV40-infected B lymphocytes, coculture of live cells, or infectious center assays all showed that replication-competent SV40 could be recovered on rare occasions. SV40 infections altered the expression of several B cell surface markers, with more pronounced changes following infections with the microRNA-null mutant.

CONCLUSION

These findings indicate that SV40 can establish persistent infections in human B lymphocytes. The cells retain low copy numbers of viral DNA; the infections are nonproductive and noncytolytic but can occasionally produce infectious virus. SV40 microRNA negatively regulates the degree of viral effects on B cells.

SIGNIFICANCE

Lymphocytes may serve as viral reservoirs and may function to disseminate polyomaviruses to different tissues in a host. To our knowledge, this report is the first extensive analysis of viral microRNA effects on SV40 infection of human lymphocytes.

Serum IgG Antibodies from Pregnant Women Reacting to Mimotopes of Simian Virus 40 Large T Antigen, the Viral Oncoprotein

Simian virus 40 (SV40) large T antigen (LT) coding sequences were revealed in different human samples, whereas SV40 antibodies (Ab) were detected in human sera of cancer patients and healthy individuals, although with a lower prevalence. Previous studies carried out by the neutralization assay gave a SV40 seroprevalence, in the general population, up to 8%, although higher rates, 12%, were detected in kidney transplant children, in a group of HIV-positive patients, and in healthy females. In this study, serum samples from pregnant women, together with those from non-pregnant women, were analyzed to check the prevalence of IgG Ab reacting to SV40 LT antigens. Serum samples were collected from pregnant and non-pregnant women, with the same mean age. Women were in the range of 15-48 years old. Samples were assayed by an indirect ELISA employing specific SV40 LT mimotopes as antigens, whereas functional analysis was performed by neutralization of the viral infectivity in cell cultures. As a control, sera were analyzed for Ab against BK polyomavirus (BKPyV), which is a human polyomavirus homologous to SV40. Statistical analyses employed chi-square with Yates' correction, and Student's t tests. Indirect ELISAs indicated that pregnant women tested SV40 LT-positive with a prevalence of 17% (23/134), whereas non-pregnant women had a prevalence of 20% (36/180) (P > 0.05). Ab against BKPyV were detected with a prevalence of 80% in pregnant women and with a prevalence of 78% in non-pregnant women. These data indicate that SV40 infects at a low prevalence pregnant women. We may speculate that SV40, or a close human polyomavirus still undetected, could be transmitted from mother to fetus.

Neutralizing and IgG antibodies against simian virus 40 in healthy pregnant women in Italy

OBJECTIVE

Polyomavirus simian virus 40 (SV40) sequences have been detected in various human specimens and SV40 antibodies have been found in human sera from both healthy individuals and cancer patients. This study analyzed serum samples from healthy pregnant women as well as cord blood samples to determine the prevalence of SV40 antibodies in pregnancy.

METHODS

Serum samples were collected at the time of delivery from two groups of pregnant women as well as cord bloods from one group. The women were born between 1967 and 1993. Samples were assayed by two different serological methods, one group by neutralization of viral infectivity and the other by indirect ELISA employing specific SV40 mimotopes as antigens. Viral DNA assays by real-time polymerase chain reaction were carried out on blood samples.

RESULTS

Neutralization and ELISA tests indicated that the pregnant women were SV40 antibody-positive with overall prevalences of 10.6% (13/123) and 12.7% (14/110), respectively. SV40 neutralizing antibodies were detected in a low number of cord blood samples. Antibody titers were generally low. No viral DNA was detected in either maternal or cord bloods.

CONCLUSIONS

SV40-specific serum antibodies were detected in pregnant women at the time of delivery and in cord bloods. There was no evidence of transplacental transmission of SV40. These data indicate that SV40 is circulating at a low prevalence in the northern Italian population long after the use of contaminated vaccines.

Post-transplant lymphoproliferative disorders are not associated with IgG4 sclerosing disease

BACKGROUND

Although the majority of post-transplant lymphoproliferative disorder (PTLD) cases are associated with Epstein-Barr virus (EBV), 20-42% of cases are EBV negative (EBV-N). The antigenic stimulus that drives EBV-N PTLD is unknown, but is likely heterogeneous. A common feature of PTLD, regardless of EBV status, is an abnormal polytypic lymphoplasmacytic infiltrate. Immunglobulin-G4 (IgG4) syndrome is also characterized by a polytypic lymphoplasmacytic infiltrate with a predominance of IgG4-positive (IgG4-P) plasma cells.

METHODS

We investigated the possibility of an association between EBV-N PTLD and IgG4 syndrome. Of 33 evaluated PTLD cases, 9 (27%) were EBV-N. EBV-N PTLD cases showed longer transplantation-to-diagnosis times than EBV-positive cases.

RESULTS

A single patient had a preceding benign duodenal biopsy with focally prominent IgG4-P plasma cells; however, no clinical data supported IgG4 syndrome, precluding an association between IgG4 syndrome and subsequent EBV-N PTLD in this patient.

CONCLUSION

As none of 29 evaluable cases of PTLD (including all 9 EBV-N cases) were associated with an increase in IgG4-P plasma cells, IgG4 syndrome does not appear to play a role in the etiology of EBV-N PTLD. The significance of these findings and the current understanding of the etiology of EBV-N PTLD are discussed.

The influence of the environment on the development of thyroid tumors: a new appraisal

Most epidemiological studies concerning differentiated thyroid cancers (DTC) indicate an increasing incidence over the last two decades. This increase might be partially explained by the better access to health services worldwide, but clinicopathological analyses do not fully support this hypothesis, indicating that there are carcinogenetic factors behind this noticeable increasing incidence. Although we have undoubtedly understood the biology and molecular pathways underlying thyroid carcinogenesis in a better way, we have made very little progresses in identifying a risk profile for DTC, and our knowledge of risk factors is very similar to what we knew 30-40 years ago. In addition to ionizing radiation exposure, the most documented and established risk factor for DTC, we also investigated the role of other factors, including eating habits, tobacco smoking, living in a volcanic area, xenobiotics, and viruses, which could be involved in thyroid carcinogenesis, thus, contributing to the increase in DTC incidence rates observed.

Spontaneous and experimental malignancies in non-human primates

Contrary to earlier established opinion that tumors in monkeys are found rarely, now the large material confirms that monkey tumors are frequent phenomenon. Tumor incidence clearly increases with age. Frequencies of benign and malignant tumors of various locations and histogenesis are slightly different. Tumors of hematopoietic system are the most frequent. Sporadic cases and enzootic outbreaks of lymphomas are described for different kinds of monkeys, including apes, and probably are caused by viruses. Two viruses were isolated by us from sick monkeys - the retrovirus C-type STLV-1 and the herpes virus papio HVP. Inoculation of virus cultures into monkeys and rabbits induces neoplasms. Monkey neoplasms can be induced by exposure to various chemical agents, and by oncogenic and non-oncogenic viruses. There is no strict species specificity of tumor viruses. The role of polyoma viruses in neoplasms etiology is discussed.

Ethnic differences in polyomavirus simian virus 40 seroprevalence among women in Houston, Texas

OBJECTIVE

To examine the prevalence and distribution among racial/ethnic groups of polyomavirus SV40 antibodies in women in Houston, Texas.

METHODS

Women in three different cohorts reflecting the evolving demographics of Houston were evaluated for frequency of SV40 antibodies using a plaque-reduction neutralization assay.

RESULTS

Women in cohort A (enrolled 1972-1973) were 68% (145/212) African-American and 32% Caucasian; the overall frequency of SV40 neutralizing antibodies was 7%. Women in cohort B (enrolled 1975-1977) were Caucasian with an overall frequency of SV40 neutralizing antibodies of 18% (37/211). Women in cohort C (enrolled 1993-1995) were 50% (199/400) African-American, 25% Caucasian, and 25% Hispanic; the overall frequency of SV40 neutralizing antibodies was 10%. Logistic regression analysis for cohort A showed no difference in SV40 neutralizing antibodies with respect to race/ethnicity, pregnancy status, number of previous pregnancies, or history of sexually transmitted diseases. For cohort C, race/ethnicity was identified as a significant factor associated with SV40 neutralizing antibodies, with Hispanics having a seroprevalence of 23% compared to 5-6% in the other two groups (p = 0.01).

CONCLUSIONS

A significantly higher SV40 seroprevalence was found among Hispanics than other racial/ethnic groups in the city of Houston. Findings are compatible with a model that certain population groups potentially exposed to SV40-contaminated oral poliovaccines have maintained cycles of SV40 infections.

Association Between SV40 and Non-Hodgkin's Lymphoma

Millions of people worldwide were inadvertently exposed to live simian virus 40 (SV40) between 1955 and 1963 through immunization with SV40-contaminated polio vaccines. Although the prevalence of SV40 infections in humans is not known, numerous studies suggest that SV40 is a pathogen resident in the human population today. SV40 is a potent DNA tumor virus that is known to induce primary brain cancers, bone cancers, mesotheliomas, and lymphomas in laboratory animals. SV40 oncogenesis is mediated by the viral large tumor antigen (T-ag), which inactivates the tumor suppressor proteins p53 and pRb. During the last decade, independent studies using different molecular biology techniques have shown the presence of SV40 DNA, T-ag, or other viral markers in primary human brain and bone cancers and malignant mesotheliomas. Evidence suggests that there may be geographic differences in the frequency of these virus-positive tumors. Recent large independent controlled studies have shown that SV40 T-ag DNA is significantly associated with human non-Hodgkin's lymphoma (NHL). In our study, we analyzed systemic NHL from 76 HIV-1-positive and 78 HIV-1-negative patients, and nonmalignant lymphoid samples from 79 HIV-1-positive and 107 HIV-1-negative patients without tumors; 54 colon and breast carcinoma samples served as cancer controls. We used polymerase chain reaction (PCR) followed by Southern blot hybridization and DNA sequence analysis to detect DNAs of polyomaviruses and herpesviruses. SV40-specific DNA sequences were detected in 64 (42%) of 154 NHL, none of 186 nonmalignant lymphoid samples, and none of 54 control cancers. For NHL from HIV-1-positive patients, 33% contained SV40 DNA and 39% Epstein Barr virus (EBV) DNA, whereas NHLs from HIV-1-negative patients were 50% positive for SV40 and 15% positive for EBV. Few tumors were positive for both SV40 and EBV. Human herpesvirus type 8 was not detected. SV40 sequences were found most frequently in diffuse large B cell and follicular-type lymphomas. We conclude that SV40 is significantly associated with some types of NHL and that lymphomas should be added to the types of human cancers associated with SV40.

JCV/BKV and SV40 viral load in lymphoid tissues of young immunocompetent children from an area of north-east Italy

Polyomavirus infection occurring during childhood is followed by a lifelong latency in immunocompetent subjects. The major site of polyomavirus persistence are the uroepithelial cells which leads to oral transmission. It has recently been hypothesized that tonsils could be a possible reservoir. The role of tonsil, adenoid, and peripheral blood mononuclear cells (PBMCs) as possible sites of JCV, BKV, and SV40 latency in young healthy children was assessed. Two hundred fifteen fresh specimens, including 57 tonsil, 80 adenoid, and 78 PBMC samples from 80 immunocompetent children (mean age 4.8 years) were analyzed to determine the viral load by quantitative real-time PCR. The human herpes virus 6 (HHV-6) was tested as a lymphotropic reference virus. Polyomavirus was detected in 5/80 (6.2%) children while HHV-6 infection affected 27/80 children (33.7%) (P < 0.001). SV40 was detected in one adenoid sample, while footprints of BKV were found in one adenoid and three tonsil samples. JCV was never found in all samples. Polyomavirus sequences were not detected in the 78 blood samples. One adenoid and two tonsils from three children (1.4%) were positive for both polyomavirus and HHV-6. Infections were characterized by low replication rates ranging typically from 1 x 10e(2)/5.5 x 10e(4) to 6.8 x 10e(3)/8.5 x 10e(4) viral copies/number of cells. In conclusion, tonsils and adenoids of children could effectively harbor BKV and SV40, although only very few cells proved to be infected. Nevertheless, the low prevalence of polyomavirus, in comparison with the lymphotropic HHV-6, suggests that these tissues are unlikely to be the preferred site of polyomavirus latency, at least in younger children.

High Prevalence of SV40 Infection in Patients with Nodal Non-Hodgkin's Lymphoma But Not Acute Leukemia Independent of Contaminated Polio Vaccines in Taiwan

Recent studies have linked simian virus 40 (SV40) to non-Hodgkin's lymphoma (NHL), especially in countries in which people were exposed to contaminated polio vaccines prior to 1963. In Taiwan, nearly all children were not exposed to contaminated polio vaccine during this period; the relationship between SV40 infection and hematological malignancies is unclear and deserves to be studied. Using PCR amplification of SV40 large T antigen DNA, confirmed by Southern blot hybridization and sequence analysis, 91 frozen lymph nodes from NHL patients were examined. Thirteen (14.3 percent) showed positive for SV40. All other test samples, including diagnostic bone marrow from patients with acute leukemia, peripheral blood from 10 relatives of SV40 positive-patients and 91 age-matched normal volunteers, and 5 reactive hyperplastic lymphoid tissues, showed negative. These results may reflect that human-to-human transmission of SV40 is independent of contaminated polio vaccines; and SV40 is possibly associated with the development of NHL in Taiwan (p = 0.0001). Prospective studies are needed to determine the prevalence of SV40 infections in our and other human populations and to explore the means of transmission of the virus.

Molecular identification of simian virus 40 infection in healthy Italian subjects by birth cohort

Simian virus SV40, an oncogenic virus in rodents, was accidentally transmitted to humans through the Poliovirus vaccine during the years 1955 to 1963. If the vaccination program were the major source of human infection, then differences in SV40 infection rates by cohort of birth should be observed. The aim of this study was to address this issue. In 134 healthy Italian Caucasian subjects, 15 DNA samples were positive for SV40 by nested polymerase chain reaction and DNA sequencing. The prevalence of genomic infection did not differ across cohorts of birth from 1924 to 1983, however DNA sequencing revealed viral strain differences in individuals born before 1947 and after 1958. While horizontal transmission following the introduction of the polio vaccine could explain the presence of SV40 DNA in younger people, our results also suggest the possibility that other sources of the virus may also be involved in human SV40 infection.

Lack of protein expression of the Simian virus 40 large T antigen in human lymphomas

Several studies have detected Simian virus 40 (SV40) deoxyribonucleic acid sequences in human tumor tissues, including lymphomas, mainly by the polymerase chain reaction, but these data were not confirmed by subsequent investigations. Regional differences in the distribution of the SV40 and/or technical difficulties have been taken into account to explain these divergent results, but because only a few such studies dealt with the expression of SV40 proteins in tumor tissues, we investigated the expression of the SV40 large T antigen in human lymphomas by immunohistochemistry. Tissue microarrays containing Non-Hodgkin's-lymphomas and Hodgkin's-lymphomas were constructed utilizing archival samples encompassing the years 1974--2001 from Italian, Swiss and Austrian patients. Expression of the SV40 large T antigen was analysed by highly specific and sensitive immunohistochemistry using a mouse monoclonal antibody. Protein expression of the large T antigen was not detected in 655 Non-Hodgkin's-lymphomas or in 337 Hodgkin's- lymphomas. The results suggest the absence of an association between SV40 large T antigen and human lymphomas.

Detection of polyomavirus SV40 in tonsils from immunocompetent children

BACKGROUND

BK virus (BKV), JC virus (JCV) and simian virus 40 (SV40) are nonenveloped DNA viruses, members of the family Polyomaviridae. BK and JC viruses establish persistent infections in humans, and evidence suggests that SV40 can infect humans, as well. Whether persistence occurs in the lymphoid system is unknown.

METHODS

Paraffin-embedded tonsils from 220 immunocompetent children (mean age 9.3 years) were examined by polymerase chain reaction (PCR) to detect viral DNA of BKV, JCV, SV40, and Epstein-Barr virus (EBV).

RESULTS

Polyomavirus-specific DNA sequences were detected in 8.3% (29/351) of specimens collected from 220 children. Twenty-one (9.5%) children had polyomavirus DNA present in at least one tonsil, with sequences identified as SV40 (n=20) and BKV (n=1). Polyomavirus JCV was not detected. Among patients positive for SV40, 8 of 14 (57%) contained viral DNA in both available tonsils. EBV DNA was detected in 99 (28.2%) samples from 67 (30.5%) patients. Eleven samples (3.1%) from 8 (3.6%) children were positive for both polyomavirus and EBV. SV40-positive children were significantly older than the SV40-negative subjects (P<0.001). T-antigen expression was detected in an SV40 DNA-positive tonsil by immunohistochemistry.

CONCLUSIONS

These results suggest that SV40 can infect tonsils, that lymphoid tissue may represent a site for polyomavirus persistence, and that immunohistochemistry is not a useful detection assay when there are very few virus-infected cells in a tissue.

Detection of simian virus 40 DNA sequences in Egyptian patients with different hematological malignancies

SV40 DNA sequences have been detected in non-Hodgkin's lymphoma patients. A link between SV40 and NHL is biologically plausible since SV40 causes hematological malignancies in laboratory rodents. We investigated 266 Egyptian cases of hematological malignancies (158 NHL, 54 HD, 26 ALL, 13 AML, 8 CLL, 7 CML) and 34 subjects as a control for detection of SV40 DNA using nested PCR. SV40 DNA sequences were found in (53.8%) of NHL, (29.6%) of HD and in (40.7%) of different types of leukemia cases. Frequency of SV40 DNA sequences was higher in NHL patients compared with those with the other tumors and control group (p < 0.05). The highest frequency was in Burkitt's lymphoma followed by diffuse large B-cell lymphoma. The present study suggests that SV40 is significantly associated with non-Hodgkin's lymphoma and most probably acts as a cofactor in the pathogenesis of these tumors. This could lead to new diagnostic, therapeutic, and preventive approaches.

Detection and typing of BKV, JCV, and SV40 by multiplex nested polymerase chain reaction

A multiplex nested polymerase chain reaction (PCR) method was developed for detecting and differentiating simultaneously the DNA of polyomaviruses JC, BK, and SV40 in a single tube. In the first amplification step the same set of primers was used to amplify a conserved DNA region of the large T antigen gene of JCV, BKV, and SV40. The second round was carried out using a set of primers designed to obtain products of different size for each related virus. Subsequently, the sensitivity of the multiplex nested PCR was maximized by optimizing parameters such as primer, magnesium, and dNTP concentrations. The sensitivity of the method ranged between 1 and 10 copies of the polyomavirus genome. The assay was then used for detecting polyomavirus DNA in urine, serum, and biopsy specimens from renal transplant recipients. Based on the results obtained, the multiplex nested PCR developed in our study represents a useful tool for supporting the diagnosis of polyomavirus infection and could be used for epidemiological purposes and to better define the role of polyomaviruses in human pathology.

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.

Polyomaviruses and human diseases

Polyomaviruses are small, nonenveloped DNA viruses, which are widespread in nature. In immunocompetent hosts, the viruses remain latent after primary infection. With few exceptions, illnesses associated with these viruses occur in times of immune compromise, especially in conditions that bring about T cell deficiency. The human polyomaviruses BKV and JCV are known to cause, respectively, hemorrhagic cystitis in recipients of bone marrow transplantation and progressive multifocal leukoencephalopathy in immunocompromised patients, for example, by HIV infection. Recently, transplant nephropathy due to BKV infection has been increasingly recognized as the cause for renal allograft failure. Quantitation of polyomavirus DNA in the blood, cerebrospinal fluid, and urine, identification of virus laden "decoy cells" in urine, and histopathologic demonstration of viral inclusions in the brain parenchyma and renal tubules are the applicable diagnostic methods. Genomic sequences of polyomaviruses have been reported to be associated with various neoplastic disorders and autoimmune conditions. While various antiviral agents have been tried to treat polyomavirus-related illnesses, current management aims at the modification and/or improvement in the hosts' immune status. In this chapter, we provide an overview of polyomaviruses and briefly introduce its association with human diseases, which will be covered extensively in other chapters by experts in the field.

Insertional Mutagenesis by Replication-Deficient Retroviral Vectors Encoding the Large T Oncogene

Insertion sites of replication-deficient retroviral vectors may trigger clonal dominance of hematopoietic cells in vivo. Here, we tested whether this would also be the case when using vectors that express powerful oncogenes, such as the large tumor antigen (TAg) of simian virus 40. TAg inactivates the tumor-suppressor proteins p53 and Rb by virtue of a chaperone-like activity. Primary hematopoietic stem/progenitor cells transduced with retroviral vectors encoding TAg-induced histiocytic sarcoma (HS) or myeloid leukemia (ML) in transplanted mice (average survival of 21 weeks). Retrovirally introducing TAg into pretransformed 32D cells generated a monocytic leukemia, with faster kinetics ( approximately 8 weeks). Leukemic clones showed retroviral insertions in genes contributing to all known TAg cooperation pathways, acting mitogenic and/or modulating apoptosis (such as BclX, Crk, Pim2, Csfr1/Pdgfrb, Osm/Lif, Axl, Fli, Sema4b, Sox4). 32D-derived monocytic leukemias showed hits in Pim2 and Max proto-oncogenes, or the chaperone Hspa4, plus additional signaling genes. Vector-mediated insertional mutagenesis thus revealed a broad spectrum of potential TAg complementation genes. These findings have important implications for the use of retroviral transgenesis in cancer research, and the expression of signaling genes in somatic gene therapy.

Presence of simian virus 40 DNA sequences in diffuse large B-cell lymphomas in Tunisia correlates with aberrant promoter hypermethylation of multiple tumor suppressor genes

The simian virus SV40 (SV40), a potent DNA oncogenic polyomavirus, has been detected in several human tumors including lymphomas, mainly in diffuse large B-cell type (DLBCL). However, a causative role for this virus has not been convincingly established. Hypermethylation in promoter regions is a frequent process of silencing tumor suppressor genes (TSGs) in cancers, which may be induced by oncogenic viruses. In this study, we investigated the relationship between the presence of SV40 DNA sequences and the methylation status of 13 TSGs in 108 DLBCLs and 60 nontumoral samples from Tunisia. SV40 DNA presence was investigated by PCR assays targeting the large T-antigen, the regulatory and the VP1 regions. Hypermethylation was carried out by methylation-specific PCR. SV40 DNA was detected in 63/108 (56%) of DLBCL and in 4/60 (6%) of nontumoral samples. Hypermethylation frequencies for the tested TSGs were 74% for DAPK, 70% for CDH1, SHP1, and GSTP1, 58% for p16, 54% for APC, 50% for p14, 39% for p15, 19% for RB1, 15% for BLU, 3% for p53, and 0% for p300 and MGMT. No hypermethylation was observed in nontumoral samples. Hypermethylation of SHP1, DAPK, CDH1, GSTP1 and p16 genes were significantly higher in SV40-positive than in SV40-negative DLBCL samples (p values ranging from 0.0006 to <0.0001). Our findings showed a high prevalence of SV40 DNA in DLBCLs in Tunisia. The significant association of promoter hypermethylation of multiple TSGs with the presence of SV40 DNA in DLBCLs supports a functional effect of the virus in those lymphomas.

Molecular and clinical perspectives of polyomaviruses: emerging evidence of importance in non-kidney transplant populations

JC virus (JCV), BK virus (BKV) and simian virus 40 (SV40) are deoxyribonucleic acid (DNA) viruses, members of the family Polyomaviridae. These viruses establish persistent infections, and reactivate from latency in their host under immunosuppression. During the last few years there has been recognition of the morbidity related to polyomaviruses, particularly BKV in kidney transplant recipients. More importantly, recent studies indicate the potential implication of JCV, BKV, and SV40 in renal dysfunction among nonrenal organ transplant patients. Polyomaviruses are tumor-inducing viruses and animal models have provided evidence of the oncogenicity of these pathogens. Although data are not conclusive, molecular studies suggest an association of BKV and SV40 with malignancies among solid organ transplant patients. As new and potent immunosuppressive agents are introduced into clinical practice, it is believed that the incidence of polyomavirus-related diseases in organ transplantation might increase. This review evaluates the biologic and epidemiologic features of these 3 viruses, the data regarding their infections in nonkidney organ transplant patients and describes future directions in the management and research of these opportunistic pathogens.

Simian virus 40 in posttransplant lymphoproliferative disorders

Simian virus 40 (SV40) is an oncogenic DNA virus, which is an emergent pathogen implicated in some human malignancies, including B-cell lymphomas. As with other malignancies that occur during immunosuppression, it is hypothesized that SV40 infections may be associated with some posttransplant lymphoproliferative disorders (PTLDs). Specimens were tested initially for Epstein-Barr virus (EBV) by in situ hybridization for EBV-encoded small RNA and/or by immunohistochemical staining for EBV-latent membrane protein 1. Coded DNA specimens extracted from formalin-fixed, paraffin-embedded tissues from 22 PTLD cases were examined by polymerase chain reaction using primers for the SV40 large tumor antigen (T-ag) gene and confirmed by sequence analysis. In addition, samples were assessed for the expression of SV40 T-ag by immunohistochemical staining. Epstein-Barr virus was detected in 18 (82%) of 22 PTLD cases. Simian virus 40 T-ag sequences were detected in 2 (13%) of the 16 cases with amplifiable DNA: one with EBV-negative T-cell PTLD and the other with EBV-positive B-cell monomorphic PTLD. Immunohistochemical staining showed expression of SV40 T-ag in 1 of 2 cases containing viral DNA sequences and in none of the SV40 T-ag DNA-negative samples. Expression of SV40 T-ag was restricted to malignant cells and not to reactive lymphocytes. These results suggest that SV40 may be associated with a small subset of PTLD cases. Additional studies are needed to determine the role of SV40 in EBV-negative PTLD.

No evidence for simian virus 40 DNA sequences in malignant non-Hodgkin lymphomas

DNA sequences coding for simian virus 40 (SV40) large T antigen have been detected at different frequencies in human non-Hodgkin's lymphomas (NHL) by PCR techniques as well as immunohistochemistry. A highly sensitive quantitative real-time PCR specific for a sequence of SV40 large T antigen was established to test whether SV40 DNA is present in malignant lymphomas of German patients. Thirty-three lymph node samples obtained from 27 patients with NHL and 6 patients with Hodgkin's disease (HD) were tested in addition to 48 samples of peripheral blood mononuclear cells (PBMNC) from patients with NHL containing between 0.1% and >90% circulating lymphoma cells determined by PCR. Fourteen lymph nodes obtained from patients with other diseases than malignant lymphomas and 47 PBMNC samples from healthy volunteers served as controls. All samples from patients with malignant lymphomas and all controls were negative for SV40 DNA by quantitative real-time. In contrast, EBV-DNA could be detected in 29 of 46 DNA preparations isolated from lymph nodes (63%) and in 20 of 47 DNA preparations from PBMNC. EBV-positive samples contained between 5 and 80,000 EBV copies per 100,000 cells. Our results do not support the hypothesis that SV40 plays a major role in the etiology of malignant lymphomas and, in addition, they exclude a clonal SV 40 infection of malignant lymphoma cells in all samples investigated.

Specific and quantitative detection of human polyomaviruses BKV, JCV, and SV40 by real time PCR

BACKGROUND

The polyomaviruses that infect humans, BK virus (BKV), JC virus (JCV), and simian virus 40 (SV40), typically establish subclinical persistent infections. However, reactivation of these viruses in immunocompromised hosts is associated with renal nephropathy and hemorrhagic cystitis (HC) caused by BKV and with progressive multifocal leukoencephalopathy (PML) caused by JCV. Additionally, SV40 is associated with several types of human cancers including primary brain and bone cancers, mesotheliomas, and non-Hodgkin's lymphoma. Advancements in detection of these viruses may contribute to improved diagnosis and treatment of affected patients.

OBJECTIVE

To develop sensitive and specific real time quantitative polymerase chain reaction (RQ-PCR) assays for the detection of T-antigen DNA sequences of the human polyomaviruses BKV, JCV, and SV40 using the ABI Prism 7000 Sequence Detection System.

STUDY DESIGN

Assays for absolute quantification of the viral T-ag sequences were designed and the sensitivity and specificity were evaluated. A quantitative assay to measure the single copy human RNAse P gene was also developed and evaluated in order to normalize viral gene copy numbers to cell numbers.

RESULTS

Quantification of the target genes is sensitive and specific over a 7 log dynamic range. Ten copies each of the viral and cellular genes are reproducibly and accurately detected. The sensitivity of detection of the RQ-PCR assays is increased 10- to 100-fold compared to conventional PCR and agarose gel protocols. The primers and probes used to detect the viral genes are specific for each virus and there is no cross reactivity within the dynamic range of the standard dilutions. The sensitivity of detection for these assays is not reduced in human cellular extracts; however, different DNA extraction protocols may affect quantification.

CONCLUSION

These assays provide a technique for rapid and specific quantification of polyomavirus genomes per cell in human samples.

Does simian virus 40 cause non-Hodgkin lymphoma? A review of the laboratory and epidemiological evidence

Recently, several studies have reported the detection of DNA from simian virus 40 (SV40), a macaque polyomavirus, in tumor tissues obtained from non-Hodgkin lymphoma (NHL) patients. SV40 accidentally contaminated poliovirus vaccines administered to millions of individuals in 1955-1962. A link between SV40 and NHL is biologically plausible because SV40 causes hematological malignancies in laboratory rodents. However, detection of SV40 DNA in human NHL tumors has not been confirmed by other laboratories. Casting doubt on an association between SV40 and NHL, follow-up studies of recipients of SV40-contaminated poliovirus vaccines have not revealed these individuals to be at increased risk of NHL. Furthermore, 2 recent case-control studies of NHL documented only infrequent SV40 antibody reactivity among NHL cases, and the prevalence of SV40 antibodies was similar in cases and controls. This review summarizes recent laboratory and epidemiological studies bearing on the question of whether SV40 is a cause of NHL in humans. The strengths and weaknesses of these data are discussed, and a framework for considering the collected evidence is presented. Many of the considerations raised in this review apply to the evaluation of data regarding other cancers, such as mesothelioma, brain tumors, and various sarcomas, for which an etiologic link with SV40 also has been proposed.

Is there an association between SV40 contaminated polio vaccine and lymphoproliferative disorders? An age-period-cohort analysis on Norwegian data from 1953 to 1997

Between 1955 and 1963, an estimated number of 150 million people in various parts of the world, including Norway, received poliomyelitis vaccine possibly contaminated with infectious simian virus 40 (SV40). Human studies have investigated the hypothesised association between SV40 and various cancers, but the results have so far been contradicting. The aim of the present study was to examine Norwegian cancer incidence data to assess a possible association between birth cohorts assumed to have been subjected to the vaccine and the incidence rate of lymphoproliferative disorders (excluding Hodgkin's lymphoma), further subdivided into non-Hodgkin's lymphoma (NHL), lymphocytic leukemia and plasma cell neoplasms. Between 1953 and 1997, the incidence rate of lymphoproliferative diseases combined increased about 3-fold in both males and females. Subgroup analysis showed that this increase was largely attributable to NHL. Age-period-cohort modelling of the subgroups, as well as of all groups combined, showed that the cohort effect was more prominent than the period effect. However, the variations in incidence patterns across the birth cohorts did not fit with the trends that would be expected if a SV40 contaminated vaccine did play a causative role. Thus, our data do not support the hypothesis of an association between the vaccine and any subgroup of lymphoproliferative diseases.

Simian virus 40 tumor antigen expression and immunophenotypic profile of AIDS-related non-Hodgkin's lymphoma

Simian virus 40 (SV40) is associated with some systemic non-Hodgkin's lymphomas (NHL) among HIV-positive patients, based on assays for viral DNA sequences. To investigate the possible production of the viral transforming protein, we examined age-matched case-control specimens from patients with HIV/AIDS for the expression of SV40 large tumor antigen (T-ag). Masked specimens initially examined by polymerase chain reaction (PCR) for polyomavirus and herpesvirus DNA sequences were assessed for the expression of SV40 T-ag and phenotypic lymphocyte markers by immunohistochemistry (IHC). Fifty-five systemic NHL and 25 nonmalignant lymphoid and malignant nonlymphoid tissue control cases from two HIV community programs in Texas and New Jersey were scored for IHC positivity without knowledge of the PCR results. IHC showed expression of SV40 T-ag among B-cell lymphomas, whereas none of the control tissue samples were positive for T-ag (12/55, 22% vs. 0/25, 0%; P = 0.01). SV40 T-ag expression was detected only in B-cell lymphoma specimens that contained SV40 DNA sequences. Not all lymphoma cells in a positive specimen stained for T-ag, and the reaction was lower intensity than observed in SV40 hamster tumors. SV40 T-ag was demonstrated in both primary and recurrent tumors from one patient. A germinal center B-cell-like (GCB) profile was more frequently expressed by SV40-positive tumors than in Epstein-Barr virus (EBV)-related lymphomas (10/12, 83% vs. 6/13, 46%; P = 0.05), whereas a non-GCB phenotype was more frequent in EBV-positive than in SV40-positive lymphomas (7/13, 54% vs. 2/12, 17%; P = 0.05). This study shows that SV40 gene expression occurs in a fraction of cells in some B-cell lymphomas among patients with HIV/AIDS.

Polyomavirus interstitial nephritis and concurrent post-transplant lymphoma in a renal allograft: coincidence or more?

We describe a case of an Epstein-Barr virus (EBV)-negative post-transplant large B-cell non-Hodgkin lymphoma located in the renal allograft, spleen, liver and left inguinal lymph node of a renal recipient and accompanied by a simultaneous polyomavirus-associated nephropathy. To our knowledge, this is the first report of a simultaneous polyomavirus infection and post-transplant lymphoproliferative disorder.

Evidence against a role for SV40 in human mesothelioma

SV40 has been implicated in the etiology of 40% to 60% of human mesotheliomas. These studies could have important medical implications concerning possible sources of human infection and potential therapies if human tumors are induced by this agent. We did PCR-based analysis to detect SV40 large T antigen DNA in human mesotheliomas. None of 69 tumors in which a single copy gene was readily amplified contained detectable SV40 large T antigen sequences. Under these conditions, it was possible to detect one copy of integrated SV40 DNA per cell in a mixture containing a 5,000-fold excess of normal cells using formalin-fixed preparations. Kidney, a known reservoir of SV40 in monkeys, from some of these individuals were also negative for SV40 large T antigen sequences. A subset of mesotheliomas was analyzed for SV40 large T antigen expression by immunostaining with a highly specific SV40 antibody. These tumors as well as several human mesothelioma cell lines previously reported to contain SV40 large T antigen were negative for detection of the virally encoded oncoprotein. Moreover, mesothelioma cell lines with wild-type p53 showed normal p53 function in response to genotoxic stress, findings inconsistent with p53 inactivation by the putative presence of SV40 large T antigen. Taken together, these findings strongly argue against a role of SV40 by any known transformation mechanism in the etiology of the majority of human malignant mesotheliomas.

Absence of simian virus 40 (SV40) DNA in lymphoma samples from Tasmania, Australia

AIMS

It has been postulated that the recent world-wide increase in the incidence of non-Hodgkin's lymphoma (NHL) may have been caused by human infection with simian virus 40 (SV40) (a lymphotropic monkey virus that was introduced to man from contaminated poliovirus vaccines between 1955 and 1963); therefore, we set out to determine the incidence of SV40 DNA positivity in lymphoma samples from patients in Tasmania, Australia.

METHODS

One hundred lymph node samples, 50 from patients with lymphomas and 50 from controls, were tested using PCR amplification of three SV40-specific primer pairs followed by dot-blot hybridisation.

RESULTS

All of the samples tested contained amplifiable DNA, but none contained amplifiable SV40 sequences with any of the primer sets used.

CONCLUSIONS

Our results demonstrate absence of SV40 in the lymphoid tissues of our study population in Tasmania, Australia. SV40 does not explain the increasing incidence of NHL in our population.

Lack of association of polyomavirus and herpesvirus types 6 and 7 in human lymphomas

BACKGROUND

The association of viruses with several human tumors has been studied for almost 100 years, and it remains a very controversial issue. Due to the fact that the presence of polyomaviruses and herpes viruses reportedly are associated with lymphomas, albeit with striking results and differences between the many studies, the authors undertook a study into the presence of viral sequences of polyomavirus (BK virus, JC virus, and especially simian virus 40 [SV40]) in human lymphomas in an attempt to explain this contradictory association. To complete the study, the presence of different virus types from the herpesviriridae family were analyzed, such as herpesvirus type 6 (HHV6), HHV7, HHV8, and Epstein-Barr virus, in human lymphomas.

METHODS

DNA was isolated from 83 frozen human lymphoma samples, and different polymerase chain reaction techniques were used to find polyomavirus and herpesvirus sequences in these samples. To assess the incidence of the presence of sequences in lymphomas, a parallel analysis was made of 53 samples from normal donor spleen lymphocytes. Positive samples were analyzed for polyomavirus sequences by immunohistochemistry.

RESULTS

Polyomavirus sequences were detected in 9 of 83 lymphomas (11%), and SV40 sequences could be confirmed in only 1 lymphoma. Immunohistochemistry for large-T antigen was negative in all samples. Herpesviruses were detected in 53 of 83 lymphomas (63.9%), were detected more frequently in Hodgkin lymphomas (80%) than in non-Hodgkin lymphomas (58.7%), and were detected in > 60% of normal spleen lymphocytes.

CONCLUSIONS

The current results did not support a clear association of polyomavirus and HHV6 or HHV7 with lymphomas; HHV6 and HHV7 sequences were detected in a similar percentage of normal samples and lymphomas. The lack of significant differences between normal and malignant lymphocytes and the absence of viral protein expression in the tumor cells did not allow the establishment of a clinical correlation between polyomaviruses or HHVs (HHV6, HHV7, HHV8) and lymphomas. Nevertheless, because viral products can be lost during tumor progression, and because host factors can modulate the oncogenic role of some viruses, the hypothetical role of these viruses cannot be discarded completely.

Antibody Responses to Simian Virus 40 T Antigen: A Case-Control Study of Non-Hodgkin Lymphoma

A possible role for SV40, a macaque polyomavirus, in non-Hodgkin lymphoma (NHL) in humans was raised recently by the reported detection of SV40 DNA in tumor tissue. Animals with SV40-induced tumors frequently produce high-level antibodies against T antigen, the SV40 oncoprotein. In this study, we assessed whether SV40 T antibody measured in humans supported a relationship between SV40 and NHL. Subjects were sampled from a U.S. population-based case-control study of NHL, according to presence of antibodies against capsids of SV40 and BK, a related human polyomavirus (n = 85 cases, n = 95 controls). T antibody was measured by enzyme immunoassay. We also evaluated serum specimens from SV40-infected and SV40-uninfected macaques (n = 19 and n = 8, respectively), SV40-uninfected hamsters (n = 5), and hamsters with SV40-induced tumors (n = 10). Hamsters with SV40-induced tumors all produced robust SV40 T antibody [median absorbance, 0.99), whereas SV40-uninfected hamsters and macaques had much lower levels (median absorbance, 0.05 and 0.04, respectively). NHL cases, controls, and SV40-infected macaques resembled these latter two groups, generally showing only low-level T antibody (median absorbance, 0.03, 0.04, and 0.04, respectively). Overall, only five cases (6%) and five controls (5%) had T antibody responses classified as seropositive (odds ratio, 1.2; 95% confidence interval, 0.3-4.6). Interestingly, all 10 humans with T antibody responses also showed antibody responses to BK capsid. We found no association between the presence of T antibody and NHL, arguing against SV40 as a cause of NHL. Infrequent and low-level T antibody responses among humans could represent cross-reactivity to BK virus T antigen.

The epidemiology of non-Hodgkin's lymphoma

The incidence of non-Hodgkin's lymphoma (NHL) has doubled over the past two decades in the US and most other westernized countries. While improved cancer reporting, changes in lymphoma classification, and increases in AIDS-associated lymphomas have contributed to the startling escalation of disease incidence, these factors are estimated to account for only about 50% of the increase in observed incidence. The elucidation of etiologic factors and their mechanistic role in the pathogenesis of this malignancy are critical to advancements in disease prevention and treatment. Current evidence suggests that factors/conditions that precipitate either chronic antigenic stimulation or immunosuppression may provide a preferential milieu for development of NHL. High rates of lymphoma have been observed among individuals with autoimmune disease, organ transplants, and primary or acquired immunodeficiencies. Ultraviolet radiation, previously demonstrated to have an immunosuppressive effect, has also been suggested as a possible risk factor for NHL. Several pathogens have been linked to the risk of lymphoma, including Epstein-Barr virus, human immunodeficiency virus, human T-cell lymphotropic virus-1, Helicobacter pylori, hepatitis C, and simian virus 40. Whether these microbes are responsible for specific genetic mutations that initiate tumor growth, antigenic stimulation leading to B-cell proliferation, and increased potential of random cell replication errors, or immunosuppression, which thereby promotes tumor growth, has not been clearly delineated. Other exogenous factors which have been implicated in lymphomagenesis are chemicals and agricultural exposures, hair dyes, and blood transfusions. We must build on our current knowledge regarding the etiology of NHL in order that prevention, treatment, and ultimately, cure of this malignancy becomes a reality.

Case-Control Study of Simian Virus 40 and Non-Hodgkin Lymphoma in the United States

BACKGROUND

Recent studies have reported detection of simian virus 40 (SV40) DNA in tumor tissues from 15%-43% of U.S. non-Hodgkin lymphoma (NHL) patients. SV40 accidentally contaminated U.S. poliovirus vaccines that were widely administered from 1955 through 1962. However, epidemiologic data linking SV40 with NHL are lacking.

METHODS

We obtained serum samples from 724 incident NHL case patients and 622 control subjects from a population-based U.S. case-control study. SV40 serostatus was analyzed by two independent laboratories (designated A and B) using similar virus-like particle (VLP) enzyme immunoassays. Associations with serostatus were assessed with logistic regression, adjusting for sex, race, birth year, and study site. VLPs for the human polyomaviruses BK and JC were used in competitive inhibition experiments to assess the specificity of SV40 reactivity. Statistical tests were two-sided.

RESULTS

SV40 antibody results from the two laboratories were correlated (R = 0.59; P<.001). Laboratories A and B detected SV40 seropositivity in 7.2% and 9.8% of NHL case patients, respectively, and in 10.5% and 9.6% of control subjects, respectively. SV40 seropositivity was not associated with increased NHL risk (laboratory A: adjusted odds ratio [OR] = 0.68, 95% confidence interval [CI] = 0.46 to 1.00; laboratory B: adjusted OR = 1.02, 95% CI = 0.71 to 1.47). SV40 seropositivity was not associated with NHLs of any specific histology or site. Among subjects born before 1963, 1.0%-1.6% showed SV40-specific reactivity, i.e., SV40 reactivity confirmed in competitive inhibition experiments, whereas (based on limited data) none born subsequently demonstrated SV40-specific reactivity.

CONCLUSIONS

In persons born before 1963, the presence of SV40-specific antibodies, although rare, could reflect exposure to SV40-contaminated vaccines. Nevertheless, NHL risk was unrelated to serologic evidence of SV40 exposure or infection.

Emergent human pathogen simian virus 40 and its role in cancer

The polyomavirus simian virus 40 (SV40) is a known oncogenic DNA virus which induces primary brain and bone cancers, malignant mesothelioma, and lymphomas in laboratory animals. Persuasive evidence now indicates that SV40 is causing infections in humans today and represents an emerging pathogen. A meta-analysis of molecular, pathological, and clinical data from 1,793 cancer patients indicates that there is a significant excess risk of SV40 associated with human primary brain cancers, primary bone cancers, malignant mesothelioma, and non-Hodgkin's lymphoma. Experimental data strongly suggest that SV40 may be functionally important in the development of some of those human malignancies. Therefore, the major types of tumors induced by SV40 in laboratory animals are the same as those human malignancies found to contain SV40 markers. The Institute of Medicine recently concluded that "the biological evidence is of moderate strength that SV40 exposure could lead to cancer in humans under natural conditions." This review analyzes the accumulating data that indicate that SV40 is a pathogen which has a possible etiologic role in human malignancies. Future research directions are considered.

Inability of simian virus 40 to establish productive infection of lymphoblastic cell lines

Lymphoblastic cell lines were infected with simian virus 40 (SV40) and then monitored for evidence of a productive infection. No evidence of early gene expression was found 2 days following infection, as determined by assaying viral mRNAs and early antigens. Furthermore, only small amounts of virus could be detected by plaque assay 2 days after infection, and levels slowly declined until they were undetectable after a few weeks in culture. Thus, human lymphocytes are not readily infectible with SV40 and do not provide a simple model for studying interactions of SV40 with a human cell type.

Activation of simian virus 40 promoter by HTLV-I Tax protein: role of NF-κB and CBP

HTLV-I is implicated with adult T-cell leukemia and certain other clinical disorders. The viral Tax protein is regarded as a key element in HTLV-I pathogenicity due to its ability to activate a wide variety of cellular regulatory factors. As such, Tax may likely activate also latent infection of certain other pathogenic viruses whose expression is modulated by cellular transcription factors. Therefore, investigation of Tax effect on the expression of these viruses is of particular clinical importance, since HTLV-I infection of carriers harboring such latent viruses may trigger their related diseases. In this study we focused on simian virus 40 and demonstrated that Tax activates the promoter of this virus through NF-kappaB-associated pathway. Furthermore, we show that this activation requires an interaction of the NF-kappaB factor p65(RelA) with CBP, which depends on PKA-mediated phosphorylation of p65(RelA). Finally, the present study proves that the nuclear Tax plays a critical role in Tax-induced NF-kappaB-mediated SV40 activation.

SV40-positive brain tumor in scientist with risk of laboratory exposure to the virus

Simian virus 40 (SV40) is a DNA tumor virus known to induce cancers in laboratory animals. There are numerous reports of the detection of SV40 DNA and/or proteins in human malignancies of the same types as those induced by SV40 in animals, including brain cancers. However, known exposure to the virus has not yet been linked directly to cancer development in a specific individual. Here we describe the detection of SV40 sequences in the meningioma of a laboratory researcher who had a probable direct exposure to SV40 and subsequently developed a tumor positive for viral DNA sequences indistinguishable from those of the laboratory source. This case suggests a link between viral exposure and tumor development.

Immunohistochemical investigation of SV40 large T antigen in Hodgkin and non-Hodgkin's lymphoma

DNA sequences from simian virus 40 (SV40) have been detected in various human tumors, including non-Hodgkin's lymphomas (NHLs), by highly sensitive PCR techniques. However, there is a strong debate as to whether SV40 is present in lymphoma cells. Using immunohistochemistry and tissue microarrays, we investigated a series of French and Canadian cases of Hodgkin's lymphomas (HLs) and NHLs and tried to detect the SV40 large T antigen using routine paraffin sections with standard and highly sensitive catalyzed system amplification methods. None of the cases of HLs (n = 250) or NHLs (n = 232) were found to contain a single large T antigen-positive cell, whereas 2 positive controls were repeatedly stained. Therefore, our results do not support the hypothesis that SV40 is implicated in the etiology of human lymphomas.

Simian virus 40 infection in humans and association with human diseases: results and hypotheses

Simian virus 40 (SV40) is a monkey virus that was introduced in the human population by contaminated poliovaccines, produced in SV40-infected monkey cells, between 1955 and 1963. Epidemiological evidence now suggests that SV40 may be contagiously transmitted in humans by horizontal infection, independent of the earlier administration of SV40-contaminated poliovaccines. This evidence includes detection of SV40 DNA sequences in human tissues and of SV40 antibodies in human sera, as well as rescue of infectious SV40 from a human tumor. Detection of SV40 DNA sequences in blood and sperm and of SV40 virions in sewage points to the hematic, sexual, and orofecal routes as means of virus transmission in humans. The site of latent infection in humans is not known, but the presence of SV40 in urine suggests the kidney as a possible site of latency, as it occurs in the natural monkey host. SV40 in humans is associated with inflammatory kidney diseases and with specific tumor types: mesothelioma, lymphoma, brain, and bone. These human tumors correspond to the neoplasms that are induced by SV40 experimental inoculation in rodents and by generation of transgenic mice with the SV40 early region gene directed by its own early promoter-enhancer. The mechanisms of SV40 tumorigenesis in humans are related to the properties of the two viral oncoproteins, the large T antigen (Tag) and the small t antigen (tag). Tag acts mainly by blocking the functions of p53 and RB tumor suppressor proteins, as well as by inducing chromosomal aberrations in the host cell. These chromosome alterations may hit genes important in oncogenesis and generate genetic instability in tumor cells. The clastogenic activity of Tag, which fixes the chromosome damage in the infected cells, may explain the low viral load in SV40-positive human tumors and the observation that Tag is expressed only in a fraction of tumor cells. "Hit and run" seems the most plausible mechanism to support this situation. The small tag, like large Tag, displays several functions, but its principal role in transformation is to bind the protein phosphatase PP2A. This leads to constitutive activation of the Wnt pathway, resulting in continuous cell proliferation. The possibility that SV40 is implicated as a cofactor in the etiology of some human tumors has stimulated the preparation of a vaccine against the large Tag. Such a vaccine may represent in the future a useful immunoprophylactic and immunotherapeutic intervention against human tumors associated with SV40.

SV40 Tag DNA sequences, present in a small proportion of human hepatocellular carcinomas, are associated with reduced survival

AIMS

To study the association between simian virus 40 (SV40) and human hepatocarcinogenesis.

METHODS

Polymerase chain reaction (PCR) to detect SV40 large T antigen (Tag) DNA was performed on: 50 human hepatocellular carcinoma (HCCs) diagnosed between 1978 and 1989 (cohort A); 20 cases of alcoholic liver cirrhosis from the same period; and 20 HCCs diagnosed after 1997 (cohort B). PCR to detect SV40 regulatory sequence and SV40 Tag immunohistochemistry were performed on selected cases from cohorts A and B. Amplified products were directly sequenced. Immunohistochemistry for p53 and pRb and clinicopathological analyses were performed on selected cases from cohorts A and B. Complete survival data were collected for cohort A.

RESULT

SV40 Tag DNA was found in five cohort A HCCs but not in alcoholic liver cirrhosis cases or cohort B HCCs. Neither SV40 regulatory sequence nor SV40 Tag protein were demonstrated in Tag DNA positive HCCs. No clinicopathological differences existed between Tag DNA positive and negative HCCs, but the presence of Tag DNA was associated with reduced disease specific survival. Relatively fewer Tag DNA positive than negative HCCs expressed p53, but loss of pRb expression was similar in the two groups. Patients with Tag DNA positive HCCs were unlikely to have received SV40 contaminated poliovirus vaccine.

CONCLUSIONS

SV40 Tag DNA is present in a small proportion of historical HCCs and may contribute to their pathogenesis and influence their outcome. The source of the virus is uncertain and more recent HCCs show no evidence of SV40.