The carcinogenicity of human papillomavirus types reflects
Mark Schiffmana,*, Rolando Herrerob, Rob DeSallec, Allan Hildesheima, Sholom Wacholdera,
Ana Cecilia Rodriguezb, Maria C. Brattib, Mark E. Shermana, Jorge Moralesb, Diego Guillenb,
Mario Alfarob, Martha Hutchinsond, Thomas C. Wrighte, Diane Solomona, Zigui Chenf,
John Schusslerg, Philip E. Castlea, Robert D. Burkf
aDivision of Cancer Epidemiology and Genetics or Division of Cancer Prevention, National Cancer Institute, National Institutes of Health, U.S. Department of
Health and Human Services, Bethesda, MA, USA
bProyecto Epidemiolo ´gico Guanacaste, San Jose ´, Costa Rica
cDivision of Invertebrate Zoology, American Museum of Natural History, New York, NY, USA
dWomen and Infants_ Hospital, Providence, RI, USA
eCollege of Physicians and Surgeons of Columbia University, New York, NY, USA
fAlbert Einstein Cancer Center, Albert Einstein College of Medicine, Bronx, NY, USA
gInformation Management Services, Silver Spring, MA, USA
Received 17 February 2005; returned to author for revision 22 February 2005; accepted 1 April 2005
Available online 3 May 2005
Persistent infections with carcinogenic human papillomaviruses (HPV) cause virtually all cervical cancers. Cervical HPV types (n > 40)
also represent the most common sexually transmitted agents, and most infections clear in 1–2 years. The risks of persistence and neoplastic
progression to cancer and its histologic precursor, cervical intraepithelial neoplasia grade 3 (CIN3), differ markedly by HPV type. To study
type-specific HPV natural history, we conducted a 10,000-woman, population-based prospective study of HPV infections and CIN3/cancer
in Guanacaste, Costa Rica. By studying large numbers of women, we wished to separate viral persistence from neoplastic progression. We
observed a strong concordance of newly-revised HPV evolutionary groupings with the separate risks of persistence and progression to
CIN3/cancer. HPV16 was uniquely likely both to persist and to cause neoplastic progression when it persisted, making it a remarkably
powerful human carcinogen that merits separate clinical consideration. Specifically, 19.9% of HPV16-infected women were diagnosed with
CIN3/cancer at enrollment or during the five-year follow-up. Other carcinogenic types, many related to HPV16, were not particularly
persistent but could cause neoplastic progression, at lower rates than HPV16, if they did persist. Some low-risk types were persistent but,
nevertheless, virtually never caused CIN3. Therefore, carcinogenicity is not strictly a function of persistence. Separately, we noted that the
carcinogenic HPV types code for an E5 protein, whereas most low-risk types either lack a definable homologous E5 ORF and/or a
translation start codon for E5. These results present several clear clues and research directions in our ongoing efforts to understand HPV
Published by Elsevier Inc.
Laboratory and epidemiologic data suggest that persis-
tent infections with carcinogenic human papillomaviruses
(HPV) cause virtually all cervical cancers and substantial
fractions of other anogenital cancers worldwide, totaling
half a million anogenital cancers annually (Bosch and de
Sanjose, 2003; Bosch et al., 2002; zur Hausen, 2000). In
0042-6822/$ - see front matter. Published by Elsevier Inc.
* Corresponding author. Division of Cancer Epidemiology and Genetics,
National Cancer Institute, National Institutes of Health, U.S. Department of
Health and Human Services, Room 7066, 6120 Executive Boulevard,
Rockville, MD 20852, USA. Fax: +1 301 402 0916.
E-mail address: email@example.com (M. Schiffman).
Virology 337 (2005) 76 – 84
aggregate, cervical HPV types (n > 40) also represent the
most common sexually transmitted agents, and most infec-
tions clear without sequelae in 1–2 years (Ho et al., 1998;
Molanoetal.,2003;Richardson etal., 2003;Woodman et al.,
2001). Based on available cross-sectional and short-term
prospective data, the risks of persistence and neoplastic
progression differ markedly by HPV type, with genetically-
As follow-up data accumulate from long-term, large cohort
studies, we can now explore more fully the natural history
and prospective risks of the individual types, as a guide to
future research and prevention efforts (Lowy and Frazer,
2003; Schiffman and Kjaer, 2003). Specifically, we con-
ducted a 10,000-woman, population-based prospective study
Rica (Bratti et al., 2004; Herrero et al., 1997, 2000;
Schiffman et al., 2000). Here, we report the strong
concordance of HPV phylogenetic analysis with viral natural
history and carcinogenicity for the full range of anogenital
Fig. 1 shows the phylogeny of known genital HPV types
derived using a Bayesian methodology, with notation of
carcinogenic risk levels assigned by the large case-control
study conducted by the International Agency for Research
on Cancer (Munoz et al., 2003). This phylogenetic tree
based upon full genome alignments (compare to (de Villiers
et al., 2004; Van Ranst et al., 1992)) suggests that at least 3
ancestral papillomaviruses are responsible for the current
heterogeneous group of genital HPV genomes. The tree
shows a high degree of robustness (no nodes or ‘‘branch-
ings’’ have <70% support) and agreement among Bayesian
and the two maximum parsimony methods (Fig. 1). The
three major groups that emerged include alpha papilloma-
virus species a10, a8, a1 and a13; a9, a11, a7, a5 and a6;
and a4, a15, a3 and a2. Interestingly, established
carcinogenic types as defined by the IARC case-control
data are derived from a common ancestor. Also in Fig. 1,
we noted that the species a9, a11 and a7 containing
carcinogenic types can code for a homologous E5 protein,
whereas the others either lack a definable E5 ORF and/or
translation start codon for E5. As notable exceptions, the
a10 types, which cause venereal warts, can also code for an
The population-based results of the Guanacaste Project
(Fig. 2, explained in Materials and methods section)
demonstrated wide variability in type-specific prevalence
(Table 1). Notably, the more likely a viral type was to
persist, the more prevalent it was in the population (Spear-
man correlation coefficient 0.46, P = 0.005). The order of
the types in Table 1 matches the distribution of types in the
phylogenetic tree in Fig. 1; thus, proximity in the table
suggests phylogenetic relatedness. For example, at the top
are listed the closely related types from species a10, HPV6
and HPV11, which are not associated with cervical cancer,
but do produce venereal warts and laryngeal papillomatosis
(Kashima et al., 1996). Of note, they are far less common at
the cervix than is usually recognized.
Many HPV types, which share a common sexual route of
transmission, were found as mixed infections with prevalent
CIN3/cancer, resulting in generally elevated but confounded
estimates of the fraction of CIN3/cancer attributable to each
of them (Table 1). However, the hierarchically-adjusted
fractions showed that prevalent cases could be largely
attributed to HPV types within species a9 and a7. HPV16
had the highest prevalence and explained the greatest
fraction of CIN3/cancer of any type. Additional PCR testing
demonstrated HPV33 (a9) in 1 of 2 CIN3/cancer cases
originally typed as HPV11 alone, and HPV16 in the case
originally typed as HPV71 alone. We did not ‘‘correct’’ the
data based on additional testing, to minimize the chance of
biasing results toward our expectations.
With prevalent cases of CIN2, CIN3, and cancer
excluded, the cohort was followed for viral persistence
and incident neoplasia (CIN1 was considered a viral effect,
not a neoplastic outcome.) Among the infections that did
persist, the risk of CIN3/cancer diagnosed during prospec-
tive follow-up was convincingly elevated primarily for
HPV16. One-third of women with persistent HPV16
infection had incident CIN3/cancer. Therefore, in addition
to 42 (13.9%) HPV16-infected women with prevalent CIN3/
cancer, 18 developed incident CIN3/cancer. In contrast, the
risks of CIN3/cancer for other types in species a9 and for
types in species a7, a5, and a6 were lower. We observed no
cases of incident CIN3/cancer for types in species a3, a8,
a10, a13, and a15. In other words, within the limits of the
size of this study, the risk was not appreciably elevated
compared to the risk in initially HPV-negative women. Of
note, the population prevalences were as high for some of
these low-risk types, including HPV61, HPV62, HPV81,
HPV83 (a3) and HPV71 (a15) as for some of the types for
which we did observe CIN3/cancer. Therefore, we can be
relatively confident of the low risk posed by these common
types that rarely if ever led to CIN3/cancer.
Fig. 3 graphically summarizes the persistence and
progression data for the most prevalent species, with
HPV16 shown separately from the rest of a9. Although
CIN3 served as our stricter surrogate endpoint for cancer
risk, this summary figure includes reviewed, histologic
cases of CIN2 to provide a clinical perspective because
CIN2 is usually treated. Persistence without CIN3/cancer
was common in several species but only HPV16 and,
secondarily, the other types in a9, and those in a7, a5, and
a6 were at elevated risk of progression given persistence. In
general, the same types that caused CIN3 and cancer were
evident in cases of CIN2. Although the small numbers
precluded statistical analysis, it is noteworthy that the types
in species a7 were over-represented in follow-up invasive
cancers. Of the 9 cancers diagnosed during follow-up (i.e.,
M. Schiffman et al. / Virology 337 (2005) 76–84
missed during the baseline screening), three showed
persistent HPV18 (one demonstrated by repeated testing
of the previously-negative enrollment specimen), one
persistent HPV45, one HPV18 only at diagnosis, and three
persistent HPV16. One tested HPV negative at both times.
age groups, <30 and 30+, in order to see whether age
modified the trends we observed. HPV persistence rates
increased generally with age, as detailed in a more extensive
analysis published elsewhere (Castle et al., in press).
However, the ancillary analysis showed that relative, inter-
typic and inter-species differences in persistence and risk of
The combination of phylogenetic analysis and popula-
tion-based prospective epidemiology provided interesting
new insights. Phylogenetic grouping predicted the natural
history and carcinogenicity of individual HPV types, and
corroborated much of the recent cross-sectional data from
Fig. 1. PhylogeneticanalysisofanogenitalHPVtypes.Numbersonornearbranches(nodes)indicatesupportindicesfrom100bootstrapestimationsusingeachof
of (+/?) when an E5 ORF was identified but did not have a translation start codon present. The number in brackets indicate the a species of the types.
M. Schiffman et al. / Virology 337 (2005) 76–84
case-control studies and case series of cervical cancer
(Munoz et al., 2003). As the most important novel
epidemiologic contributions, 1) we showed that population
prevalence of individual types is correlated with viral
persistence and 2) we distinguished viral persistence from
neoplastic progression given viral persistence. Persistence
and progression are highly associated (Ho et al., 1995;
Nobbenhuis et al., 1999; Schlecht et al., 2001) and large
numbers of subjects must be followed for several years to
disentangle the two. We observed that the types and species
with presumed low cancer risk defined a priori by their
absence (i.e., they are not found alone) in cancer case series
showed varying degrees of persistence, but did not progress
to CIN3/cancer. In contrast, the most carcinogenic HPV
types concentrated in species a9 and a7 were distinguished
by elevated risk of progression given persistence, rather than
persistence alone. We also showed clearly that the role of
E5, which is a transforming protein in some papillomavi-
ruses (DiMaio and Mattoon, 2001), deserves further study
regarding its activities in infected cervical cells.
HPV16 was uniquely carcinogenic by all important
standards of risk, i.e., attributable fraction of prevalent
CIN3/cancer, probability of persistence, and probability
of incident CIN3/cancer given persistence. It has been
reported previously based on cross-sectional evidence that
approximately 50% of cervical cancers, and an even higher
percentage of non-cervical HPV-induced cancers (e.g., HPV-
positive oropharyngeal cancers), are caused by HPV16
(Bosch and de Sanjose, 2003; Herrero et al., 2003). To this,
we add that persistent HPV16 infection represents a
carcinogen with a very high positive predictive value of
serious neoplasia, deserving clinical evaluation and follow-
up. Few other exposures cause precancer/cancer in approx-
imately 20% of those exposed. HPV16 is now the primary
target of HPV vaccine trials (Koutsky et al., 2002; Lowy and
from other carcinogenic types in diagnostic kits, even if the
other types are not individually characterized. In previous
work, we and others have observed that most resolving
HPV16 infections cleared by 1–2 years after enrollment (Ho
et al., 1998; Richardson et al., 2003), suggesting a practical
endpoint to surveillance of persistently infected women
without evident lesions (yet). HPV18 also deserves special
lesions that are difficult to detect by cytology (Andersson et
al., 2001), shown perhaps by the presence of HPV18 (and
possibly HPV45, which is closely related) among the few
missed follow-up cancers in our study.
Despite the large size of this cohort, the stability of
estimates for the less common types was low and individual
confidence intervals were very broad. Also, it is possible that
some of the risk estimates for probability of persistence and
probability of CIN3/cancer could have been affected by
differential sensitivity of HPV testing method for different
HPV types (Gravitt et al., 2000). Specifically, the primer set
we used does not efficiently amplify some types, including
our type-specific HPV-infected subcohorts were defined at
enrollment, without distinction between new (incident) and
already persistent infections. Perhaps, on average, some of
the types had already persisted longer than others and were,
therefore, at altered risk of subsequent extended persistence
and progression to CIN3/cancer. In ongoing work, we are
following newly-infected women, to gain a more complete
Fig. 2. Guanacaste study population. Of the 10,049 women enrolled in the Guanacaste cohort, we excluded 583 virgins, 300 women without enrollment HPV
results, and 630 women with hysterectomies. Among 8536 women screened at enrollment, there were 55 CIN2, 73 CIN3 and 12 invasive cancer cases. In the
prospective cohort, we excluded women without any follow-up PCR results (803 no follow-up, 165 inadequate or no PCR results for collected specimens). We
also excluded 290 women with possible CIN 2 or worse at enrollment (including the 140 with confirmed, prevalent ?CIN2). There were 60 cases of incident
histologic CIN3 and 9 cases of cancer that occurred despite surveillance. For those censored during follow-up but prior to 5 years due to possible (even if not
confirmed) incident CIN2, CIN3, or cancer (n = 165) or for any other reason (e.g., death from other causes, relocation, n = 179), we analyzed the last specimen
prior to censoring and/or appropriate treatment.
M. Schiffman et al. / Virology 337 (2005) 76–84
infections with different HPV types.
Despite these acknowledged limitations, the consistency
of the genealogical inference represented by Fig. 1 with the
patterns of natural history data was remarkable. The HPV
genome is small enough (8 Kb) to permit a comprehensive
analysis of all its components and functions on a population
level. Through the study of HPV types and variants, we
wish to define the critical, specific viral sequences and
polymorphisms associated with immune evasion, persis-
tence, transformation (Fehrmann and Laimins, 2003), and
possible interactions between HPV and humans (Wang and
Hildesheim, 2003). In particular, we want to identify and
understand the genetic determinants that set HPV16 apart
from other closely-related types in species a9 and from
long-persisting but benign types in other species groups
Population-based HPV natural history and CIN3/cancer risk data from Guanacaste
Species (alpha)Type # of infected
# Prevalent CIN3/cancer # and % of persistence among
women <CIN2 at enrollmentc
# and % of CIN3/ICC among women
wit persistent type-specific HPVc,d
aThe fraction of prevalent cases of CIN3/cancer attributable to an HPV type was calculated as AF = % cases positive for that type ? (1 – 1/OR) where OR
represents the odds ratio associating that type and prevalent risk of CIN3/cancer. OR for a type = (number of cases positive for that type divided by number of
cases negative for that type) divided by (number of controls positive for that type divided by number of controls negative for that type). Two types (71 and 61)
had slightly negative AF, which were set to zero.
bIn the hierarchical analysis of attributable fraction, women with types accounting for a higher fraction of CIN3/cancer were excluded. For example, women
with the type accounting for the highest fraction of CIN3/cancer (i.e., HPV16) were excluded to find the next most important type (i.e., HPV58), and women
with either type were excluded to find the third, etc.
cWomen with prevalent or incident CIN2 were excluded to provide diagnostic certainty, because they represented equivocal cases. As a result, the percentages
in the table can not be exactly calculated directly from the counts of numbers of infections and outcomes.
dFour cases of CIN3 involved persistence of two types: 52/59, 16/33, 16/51, 51/70.
eSome cases of incident CIN3 arose without observed viral persistence of a defined type (i.e., they were HPV negative or had an undefined type at
enrollment). In some cases, we possibly missed the period of persistence by infrequent (5–7 year interval) measurement.
M. Schiffman et al. / Virology 337 (2005) 76–84
(e.g., a3). HPV molecular epidemiology now presents an
unparalleled opportunity to study carcinogenesis from the
molecular to the population level.
Materials and methods
Papillomavirus evolution is inferred from phylogenetic
analysis, in which the relatedness of viral DNA and
translated proteins from individual types is analyzed. Types
with smaller differences between them are presumed to be
more closely related, as displayed on the branchings of
evolutionary trees. We derived a phylogenetic tree using
standard approaches. Specifically, we used independent
Bayesian (Huelsenbeck, 2004) and maximum parsimony
methods (Swofford, 1998). The HPV genome is quite
small, permitting analysis based on most of its genes. All
component trees were based on the alignment of con-
catenated early and late open reading frames (E6, E7, E1,
E2, L2 and L1 ORF). The Bayesian tree was calculated
from a mixed data set containing alignments of both amino
acid and nucleotide sequences. Only informative sites were
kept for the two parsimony analyses, one based on
nucleotide sequences and the other based on amino acid
sequences. Bovine papillomavirus 1 was used as the
‘‘referent outgroup’’, meaning an independent point of
comparison to the human papillomaviruses under study. We
determined the presence of an E5 ORF since it is the only
ORF in the genome of genital HPVs showing significant
heterogeneity in its presence. (We consider the E5 ORF
identified in HPV16 as the bona fide E5, since the protein
has been identified in lesions (Kell et al., 1994)). HPV
genomes were examined for the presence of a homologous
E5 ORF based on the length and sequence similarity of
codon region between E2 and L2 ORFs by pairwise
alignment with the HPV16 E5 amino acid sequence. In
addition, we also checked the annotated file of each HPV
type in GenBank, NCBI.
The Guanacaste study population is outlined in Fig. 2.
The Guanacaste Project enrolled 10,049 (93.6% of eligible)
women by random sampling of the high-risk Costa Rican
province in 1993-1994, following approval by Costa Rican
and U.S. ethical boards and individual written informed
consent (Bratti et al., 2004; Herrero et al., 1997). A few,
intensively trained nurses screened adult women (age range
18–97) using cytology and cervicography (magnified
cervical images). The cytologic specimens were collected
with cervical brooms to create split-sample cytology
(conventional then liquid-based). Cells for HPV DNA
testing were collected using Dacron swabs placed into
Digene specimen transport medium, and kept at ?70- for
For both the cross-sectional (enrollment) and prospective
parts of this analysis, we excluded women with prior
hysterectomies (n = 630), who were virgins (n = 583),
who refused a pelvic exam (n = 291), or who were missing
enrollment HPV test results (n = 9). The remaining women
were categorized into several groups based on the results of
the screening exam; the groups were followed differently
according to perceived risk of developing CIN3/cancer. We
actively re-screened every 6–12 months those women
considered at elevated risk because of equivocal or mildly
abnormal cytology, HPV DNA positivity using the Hybrid
Capture Tube Test (Digene Corporation, Gaithersburg, MD),
a positive cervigram, or a lifetime report of >4 sexual
partners. A randomly-chosen, comparison group with
entirely normal findings at enrollment was also followed
Fig. 3. Outcomes of infections in the 5–7 year study, by species. For the most prevalent species, we graphed the additive percentages of prevalent CIN3/cancer
(black), prevalent CIN2 (gray), incident CIN3/cancer given viral persistence (blue), incident CIN2 given viral persistence (red) and viral persistence without
progression to CIN2/CIN3/cancer (green). To highlight its uniqueness, we showed HPV16 separately from the rest of species a9. The addition of prevalent and
incident CIN3/cancer yields a rough estimate of the absolute risk of CIN3/cancer for each species. Prevalent cases were assigned hierarchically (see Materials
and methods and Table 1). The percentage of incident CIN2/CIN3/cancer was calculated among women with follow-up. We noted above each bar the number
of infections with types in that species.
M. Schiffman et al. / Virology 337 (2005) 76–84
actively every year, while the remaining women with normal
screening results (n = 5,620) were assigned to passive
follow-up at 5–7 years, with 4,903 (87.2%) participating.
For the prospective analysis, the final analysis group
excluded women diagnosed with CIN2 or more severe
(?CIN2) at enrollment (n = 140) or missing follow-up PCR
results for any reason (n = 1,118). Missing follow-up was
strongly related to younger age, due to younger women
leaving Guanacaste for work (P < 0.0001, Pearson m2).
Because women were re-screened on different schedules
related to risk of CIN3/cancer, we concentrated on long-
term viral persistence, which we could examine for the
entire cohort. We chose the follow-up specimens from
return visits 5–7 years after enrollment except for women
referred to colposcopy earlier for possible incident CIN2 or
worse. From them, we tested the last available specimen.
Women had a mean of 3.2 visits (standard deviation = 2.0
visits), median of 2.0 visits, and a range of 2-10 visits
including enrollment and follow-up specimen collection
visits. The mean follow-up of the 7278 women in the
prospective analysis was 5.6 +/? 1.2 years (median 5.1).
All women with possible CIN2 or worse at any time,
detected by any screening technique including nurse
concern on gross examination (and whether ultimately
confirmed on initial or final histologic review) were referred
to colposcopy with guided biopsy of visible lesions. Women
diagnosed locally on initial histologic evaluation as CIN 2
or worse were treated by LEEP or by inpatient surgery if
needed; women treated with LEEP were re-examined at six-
month intervals to insure treatment success.
Although CIN2 was treated if diagnosed locally, it is not
an optimal surrogate endpoint for cancer risk because of
diagnostic variability and biologic variability. We wished to
be as certain as possible that we were studying risk for
cancer or its immediate precursor (Stoler and Schiffman,
2001). Therefore, histologic CIN2 was kept separate from
the primary CIN3/cancer analytic case group. CIN1 was
considered a morphologic consequence of HPV infection,
not serious neoplasia, and was not treated during follow-up
(Wright et al., 2003).
For study purposes (not clinical care), histology diag-
nosed locally as CIN2 or worse locally was reviewed by U.S.
pathologists (M.E.S. and T.C.W. for the enrollment cases;
M.E.S. and D.S. for the follow-up cases). The few cases of
glandular lesions were combined with comparably severe
squamous in situ or invasive carcinoma. The final assign-
ment of cases as invasive cancer, CIN3, CIN2, <CIN2 was
made by an algorithm based on independent masked
reviews. Only a few very difficult cases were adjudicated
by joint review, occasionally with consideration of cytologic
slides as well as histology.
For this analysis, we thoroughly examined each woman
at enrollment and 5–7 years later, to ascertain the HPV
type-specific risk of prevalent neoplasia, viral persistence,
and incident cervical neoplasia. Except for exclusion of
women with no follow-up from prospective rates, HPV
prevalences and risks were calculated without adjustment
for loss-to-follow-up because of the very high participa-
tion. In calculating the fractions of prevalent CIN3/cancer
attributable to individual HPV types, we accounted for
frequent multiple infections in cases (41% of the 85
prevalent CIN3/cancer cases had multiple infections,
yielding 138 case-associated infections in all) by hierarch-
ical analysis: HPV types were sorted according to
attributable risk of CIN3/cancer. When analyzing the
contribution of a given type, women with types accounting
for a higher fraction of CIN3/cancer were excluded. For
example, women with the type accounting for the highest
fraction of CIN3/cancer (i.e., HPV16) were excluded to
find the next most important type (i.e., HPV58), and
women with either type were excluded to find the third,
etc. The hierarchical approach might have underestimated
the risk of some types with low attributable fractions (e.g.,
HPV52), thus, crude and hierarchically-adjusted estimates
are both shown.
HPV testing methods
HPV DNAwas detected using MY09/M11 L1 consensus
primer PCR (MY09/11 PCR) with AmpliTaq Gold polyme-
rase as previously described (Castle et al., 2002; Herrero et
al., 2000; Qu et al., 1997). Briefly, an aliquot of the STM
specimen was lysed, and the specimen DNA was precipi-
tated by ammonium acetate/ethanol solution and then
pelleted by centrifugation. The DNA pellet was suspended
in 10 mM Tris, pH 8.0 with 0.1 mM EDTA and stored
frozen until used. Thermocyling conditions included initial
denaturation at 95 -C for 9 minutes; thereafter, each cycle
consisted of 95 -C for 60 seconds, 55 -C annealing for 60
seconds, and extension at 72 -C for 60 seconds for a total 40
cycles with a final extension at 72 -C for 5 minutes. A 100-
cell copy SiHa HPV DNA positive control, a 2-cell copy
SiHa HPV DNA positive control, and a 100-cell copy of
HuH7 HPV DNA negative control were used per every 48
PCR products were analyzed by gel electrophoresis and
then transferred to nylon filters. The filters were hybridized
overnight with radiolabeled generic probes for HPV (HPV
11, 16, 18, 51, 73 and 81 combined). Thereafter, HPV PCR
products were typed using dot blot hybridization with
biotinylated type-specific oligonucleotide probes for HPV
types: 2, 6, 11, 13, 16, 18, 26, 31-35, 39, 40, 42-45, 51-59,
61, 62, 64, 66-74v, 81-85, 82v (AE2), 89, AE9, and AE10.
Probes for HPV Types 2, 13, 34, 42-4, 57, 64, 69, 74, 82,
and AE9 were combined in dot blot hybridizations for
detection of rare types (dbmix). A specimen was considered
HPV positive, but uncharacterized, if it tested positive for
HPV DNA by the radiolabeled generic probe mix but was
not positive for any type specific probe.
M. Schiffman et al. / Virology 337 (2005) 76–84
The Guanacaste Project was supported by the National
Cancer Institute, National Institutes of Health, Department
of Health and Human Services contracts NO1-CP-21081,
NO1-CP-33061, NO1-CP-40542 and NO1-CP-506535. We
are grateful for the support of Costa Rican health authorities
and for the decade-long dedication of the superb project
staff. Dr. Burk was supported by National Cancer Institute
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