Epidemiological Evidence Regarding a Causal Association Between SV40-contaminated Poliovirus Vaccines and Human Cancer

Transcription

1 Epidemiological Evidence Regarding a Causal Association Between SV40-contaminated Poliovirus Vaccines and Human Cancer

2 Overview of the Controversy SV40, a natural infection of Asian macaques, contaminated poliovirus vaccines late 1950s - early 1960s. SV40 is oncogenic in rodents and can transform human cells in vitro. Most epidemiologic studies have found no association of cancer risk with SV40-contaminated poliovirus vaccine. An increasing number of laboratory studies have reported SV40 DNA in human tumors.

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4 Simian Virus 40 (SV40) Common asymptomatic infection of Asian macaques Polyomavirus Family - small, nonenveloped viruses with icosahedral capsids, and circular double stranded DNA genomes SV40 shares substantial genomic, antigenic and biologic similarities to human Polyomaviruses (BKV + JCV)

5 Laboratory-Induced Tumors in Rodents Laboratory-Induced Tumors in Rodents Adapted from T.F. Hogan et al., 1991 Site and Histology JCV BKV SV40 CNS choroid plexus yes yes ependymoma yes yes yes glioblastoma yes medulloblastoma yes neuroblastoma yes yes pineocytoma yes yes retinoblastoma yes Lymph nodes histiocytic lymphoma yes yes Pancreas malignant insulinoma yes Pleura mesothelioma yes Sarcomas osteosarcoma yes yes hemangioma yes leiomyosarcoma yes rhabdomyosarcoma yes

6 Human Exposure to SV40

7 Sources of Known Human Exposure to SV40 in the United States *Adapted from Shah and Nathanson, AJE 1976;103:1-12. Product Live RSV Inactivated Adenovirus Vaccine IPV OPV Route Respiratory Injected Injected Oral SV40 Titers High Low Mostly low High Years Exposed Volunteers (n<100) Military Recruits (n=100,000) General Population Volunteers (n=10,000)

8 SV40 Contamination of Poliovirus Vaccine in the United States Rhesus monkey kidney cell cultures used to grow poliovirus for vaccine SV40 discovered as contaminant of IPV SV40 found to be tumorigenic in rodents US government required all vaccines to be free of SV40, but earlier lots not withdrawn Given 1 yr storage, and 6 mo shelf life, SV40 contamination was widespread from start of Mass Immunization Program in 1955 to early 1963.

9 Percent Vaccinated by Age/Birth Cohort (1961) Determined from by national household sample surveys conducted annually by the Bureau of the Census

10 Level of SV40 Exposure Through IPV Formaldehyde inactivates SV40 albeit less than poliovirus. Common manufacturing practices limited SV40 levels in many vaccine lots, but titers varied by batch, and producer. Shah (1976) % of vaccines had live SV40. Some high, most probably low. Census Bureau household surveys showed 75% age <20 received 3+ immunizations as of 1961 (more by 1963). OVERALL: Injection w/low titers of live SV40 appears to have been common in vaccinees.

11 Initial Epidemiologic Studies

12 Investigator Fraumeni (1963) Stewart and Hewitt (1965) Innis (1968) Exposure IPV in children ages 6-8 Children (vaccine unspecified) IPV in children Design Cohort w/ 4yrs followup Case- Control Epidemiologic Studies of SV40- Contaminated Vaccines and Human Cancer Case- Control Subjects All U.S. children 6-8 yo as of May 1955 compared by IPV SV40 titer 999 leukemias, 1108 other CA, matched controls 816 miscellaneous CA, matched controls Assn. None None High overall rate of CA

13 Epidemiologic Studies of SV40- Contaminated Vaccines and Human Cancer Investigator Exposure Design Subjects Assn. Fraumeni (1970) Mortimer (1981) IPV and OPV in neonates Cohort w/ years followup 1073 exposed newborns None Heinonen (1973) Farwell (1979, 1984) Maternal vaccination w/ OPV and IPV Maternal vaccination w/ IPV Cohort w/ 4 years followup Case- Control IPV = 18,342 OPV = 3,056 None = 24, medulloblastoma and population controls High rates of neural tumors High rates of exposure

14 Recent Epidemiologic Findings in Europe

15 SV40 and Human Cancer in Germany Geissler E. Prog Med Virol. Melnick (ed). Krager,, Basil 37:211 (1990) Exposed: 885,783 children (born ) received SV40-contaminated OPV Unexposed: 891,321 children (born ) Cancer Astrocytoma Ependymoma Glioma Medulloblastoma Meningioma Oligondendroglioma Other brain tumors Sarcomas Other Total (*number of cases) Exposed 65* Unexposed

16 SV40 and Human Cancer in Sweden Olin P. Dev Biol Stand. 1998; 94: 227. Exposed: Children (born ) who received SV40-contaminated IPV Unexposed: Closest older and younger birth cohorts that did not have exposure Tumor Ependymoma Association None All Brain Cancers Osteosarcoma Pleural Mesothelioma None None None

17 Recent Epidemiologic Findings in the United States

18 Strickler et al., JAMA 1998; 279:

19 Ependymoma incidence among children ages 0-40 in Connecticut, before ( ), 1954), during ( ), 1964), and after ( ) 1969) mass immunization with SV40-contaminated IPV. Incidence per 100,000 Person-Years Period of Vaccine Contamination Five Year Period

20 Strickler et al., JAMA 1998; 279:

21 Summary of findings in U.S. birth cohorts exposed to SV40 as infants or as young children We studied Brain Cancers, Ependymomas, Osteosarcomas, Mesotheliomas No epidemic or increases in cancer rates attributable to exposure to SV40- contaminated poliovirus vaccines could be discerned

22 Risk of Pleural Mesothelioma Among Persons Exposed to SV40-contaminated Poliovirus Vaccine as Adults

23 Age-Standardized Incidence Rates of Pleural Mesothelioma in SEER, by Sex 2 Males Rate per 100,000 person-years Both Females Year

24 Absolute Number of Pleural Mesothelioma Cases in Women SEER = 12 million women (1991) million (1997)

25 Age-Specific Pleural Mesothelioma Rates in SEER 20 Males 20 Females Rate per 100,000 person-years Year Year

26 Summary and Implications of Descriptive Data Pleural mesothelioma was persistently rare among women, even though men and women received SV40- contaminated poliovirus vaccine in similar numbers. The small number of female cases that did occur mainly involved the oldest age groups, least likely to have ever received poliovirus vaccine. The results among women are inconsistent with an independent effect of SV40-contaminated vaccine exposure and risk of pleural mesothelioma.

27 Summary and Implications of Descriptive Data (cont) Some investigators have suggested that exposure to SV40-contaminated vaccine might have specifically increased the risk of asbestos-negative tumors. However, our findings suggest that the number of asbestos-negative cases, if any, that might be attributable to SV40-contaminated vaccine exposure, would be a fraction of the low number of cases in women, plus a similar small number in men. The persistent rarity of female pleural mesothelioma, also suggests that even if alternative sources of exposure to SV40 exist, they have not had a substantial independent effect on the risks of pleural mesothelioma.

28 Age-Period Period-Cohort Model To obtain a comprehensive statistical assessment of trends in pleural mesothelioma incidence we used the ageperiod-cohort model. The age-period-cohort model estimates the expected pleural mesothelioma incidence rate as a function of age, calendar year, and birth cohort. The model simultaneously accounts for birth cohort effects, the effects associated with aging, and temporal trends that may have impacted all age groups in the population at once.

29 Results of the Age-Period Period-Cohort Model for Pleural Mesothelioma Males

30 Differences between adjacent birth cohort effects in relation to differences in exposure to SV40- contaminated poliovirus vaccine

31 Summary of Age-Period Period-Cohort Model Results The age-period-cohort model provided a comprehensive statistical assessment of trends in mesothelioma incidence. Among men, birth cohort effects showed a pattern of moderation in risk beginning with the birth cohort, consistent with reported trends in occupational asbestos exposure. However, there was no evidence of an accelerated risk in subsequent birth cohorts with higher exposure to SV40- contaminated poliovirus vaccine.

32 Conclusions of Mesothelioma Study Neither the descriptive data or age-period-cohort models suggested an independent relation of mesothelioma with SV40-contaminated poliovirus vaccine. It is also unlikely that an interaction between SV40 and asbsestos explains increases in mesothelioma rates. Rate increases were greatest in elderly, those least likely to be vaccinated, whereas rates in heavily exposed age groups stable. Age-period cohort model found no evidence of an accelerated risk in birth cohorts with higher SV40 exposure. Most reports of SV40 DNA in mesothelioma have not detected differences in prevalence according to asbestos exposure.

33 Other Epidemiologic Studies of SV40- contaminated poliovirus vaccine and human cancer in the United States Engels et al. will be presented. Fisher et al. No significant associations.

34 Summary of Epidemiology Studies No studies in the U.S. or in Europe that directly examined the tumors putatively associated with SV40 found significantly increased risks in those exposed to SV40- contaminated poliovirus vaccine.

35 Molecular Epidemiology Studies

36 Assessment of Human Mesothelioma for SV40 DNA Strickler et al., Cancer Epidemiol Biomarkers Prev 5: , 475, 1996 SPECIMENS 50 pleural mesotheliomas Negative controls - SV40-negative BSC-1 cells Positive controls titrations of COS-1 cells PCR ASSAYS SV40 SV.for3/SV.Rev bp fragment of SV40 PYV.for/SV.Rev bp of BKV, JCV, and SV40 Control - GH20/PC bp of human beta-globin

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38 Case-Control Control Comparison of SV40 Neutralizing Antibodies Strickler et al., Cancer Epidemiol Biomarkers Prev 5: , 475, 1996 Serum Specimens - NCI Immunodiagnosis Serum Bank 34 pleural mesothelioma patients 33 osteosarcoma patients 35 controls SV40 plaque inhibition assay Results None were fully neutralizing Only 3 meso, 1 osteo, 1 control >50% neutralizing

39 Studies of SV40 and NHL Author Lab Tissue N % Martini-98 Rizzo-98 David-01 Vilchez-02 Shivapurkar-02 Martini Carbone Miller Butel Gazdar NHL Hodgkin s Benign Nodes NHL Benign Prolif. NHL Normal blood NHL Benign Nodes Normal blood NHL Hodgkin s Normal blood Breast Cancer Colon % 16% 33% 10% 24% 14% 16% 42% 0% 0% 43% 9% 0% 10% 5%

40 12 mesothelioma specimens Tested in 4 labs with 2 assays Negative controls = water Testa et al. Lab Assay 1 12/12 12/12 12/12 9/12 Assay 2 11/12 10/12 9/12 12/12 Higher than expected prevalence w/ no clear negatives. Did not exclude possibility of contamination in tissue processing.

41 Standard of Care in Molecular Epidemiology Studies All specimens masked (integrity of study) Tissues tested in replicate (reproducibility) Normal tissue (contamination during processing; sectioning or DNA extraction) Positive/Negative laboratory controls (sensitivity and specificity) Adequate sample size to assess the above

42 International SV40 Working Group Study: Evaluation of Assays for Detection of SV40 DNA in Human Mesotheliomas Cancer Epidemiol Biomarkers Prev 10: , 532, 2001 First study to have labs w/conflicting results test the same specimens 9 laboratories / 15 PCR assays Majority that presented findings (pos and neg) at workshop, SV40: a possible human pathogen Specimens: collected/prepared and masked by 3rd parties 25 replicate tumor samples (to measure reproducibility) 25 Normal lung (to rule out contamination) Pos / Neg lab prepared controls (Sensitivity/Specificity)

43 n=10 n=10 n=25 n=50 Tumor Specimens: Fresh frozen mesothelioma tumors w/ high content of cancer cells Each specimen contained 2 g of genomic DNA Pilot studies confirmed: (i) The DNA extraction method obtained low wt and genomic DNA (ii) Low molecular weight DNA was present in test specimens (iii) Inhibitors of PCR were not present in test specimens (iv) Human ß-globin could be amplified from test specimens

44 Results of Multi-laboratory laboratory Study None of the human pleural mesothelioma specimens tested were reproducibly positive for SV40 DNA in any of the 15 PCR assays conducted in the 9 laboratories.

45 Negative Results in SV40 DNA Studies De Mattei 1994 ependymoma/ choroid plexus, glioma, other CNS Krainer 1995 ependymoma Strickler 1996 pleural mesothelioma Volter 1998 meningioma Mulatero 1999 mesothelioma Weggen 2000 ependymoma,medulloblastoma, meningioma Int SV40 Grp 2001 mesothelioma Gordon 2002 mesothelioma Hubner 2002 mesothelioma

46 Epidemiologic Assessment of Causality Strength of Association Mixed results in SV40 PCR studies. Few non-amplification studies. No serologic support for SV40/cancer association. Epidemiologic studies have had null results. Gradient- No evidence. Temporality No evidence. Epidemiologic studies have null results.

47 Epidemiologic Assessment of Causality Specificity of Association Poor Specificity A wide range of biologically unrelated tumors that do not share risk factors are said to be SV40-associated. Biologic Plausibility SV40 is widely recognized as a tumorigenic virus. Human tumors include types induced by SV40 in rodents. However BKV/JCV induce same tumors in rodents as SV40. Levels of SV40 very low (<< 1 copy/cell), requiring new concepts of tumorigenicity.

48 Basic Questions Relevant to Causality (if SV40 is present in tumors) What are the risk factors for infection with SV40? Are the risk factors for infection the same as for the cancers putatively associated with SV40? Does exposure to SV40 precede cancer? Is greater SV40 exposure associated with risk of cancer? Is prevalence of infection greater in those who were immunized with SV40-contaminated vaccines? What other modes of SV40 transmission exist, if any?

49 Causality Map You are here: Causality Proven SV40 HPV

50 Collaborators National Cancer Institute James J. Goedert Philip S. Rosenberg Susan S. Devesa Joseph F. Fraumeni, Jr. Johns Hopkins Keerti V. Shah Richard Daniel

51 Number of Poliovirus Cases in the U.S. by Year 25 Thousands