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1.  Cohort Profile: The Skin Cancer After Organ Transplant Study 
The Skin Cancer after Organ Transplant (SCOT) study was designed to investigate the link between genus beta human papillomavirus (HPV) and squamous cell skin cancer (SCSC). We focused on a population receiving immunosuppressive therapy for extended periods, transplant patients, as they are at extremely high risk for developing SCSC. Two complementary projects were conducted in the Seattle area: (i) a retrospective cohort with interview data from 2004 recipients of renal or cardiac transplants between 1995 and 2010 and (ii) a prospective cohort with interview data from 328 people on the transplant waiting lists between 2009 and 2011. Within the retrospective cohort, we developed a nested case–control study (172 cases and 337 control subjects) to assess risk of SCSC associated with markers of HPV in SCSC tumour tissue and eyebrow hair bulb DNA (HPV genotypes) and blood (HPV antibodies). In the prospective cohort, 135 participants had a 1-year post-transplant visit and 71 completed a 2-year post-transplant visit. In both arms of the cohort, we collected samples to assess markers of HPV infection such as acquisition of new types, proportion positive for each type, persistence of types at consecutive visits and number of HPV types detected. In the prospective cohort, we will also examine these HPV markers in relation to levels of cell-mediated immunity. The goal of the SCOT study is to use the data we collected to gain a more complete understanding of the role of immune suppression in HPV kinetics and of genus beta HPV types in SCSC. For more information, please contact the principal investigator through the study website:
PMCID: PMC3887562  PMID: 23171871
2.  Characteristics of Memory B Cells Elicited by a Highly Efficacious HPV Vaccine in Subjects with No Pre-existing Immunity 
PLoS Pathogens  2014;10(10):e1004461.
Licensed human papillomavirus (HPV) vaccines provide near complete protection against the types of HPV that most commonly cause anogenital and oropharyngeal cancers (HPV 16 and 18) when administered to individuals naive to these types. These vaccines, like most other prophylactic vaccines, appear to protect by generating antibodies. However, almost nothing is known about the immunological memory that forms following HPV vaccination, which is required for long-term immunity. Here, we have identified and isolated HPV 16-specific memory B cells from female adolescents and young women who received the quadrivalent HPV vaccine in the absence of pre-existing immunity, using fluorescently conjugated HPV 16 pseudoviruses to label antigen receptors on the surface of memory B cells. Antibodies cloned and expressed from these singly sorted HPV 16-pseudovirus labeled memory B cells were predominantly IgG (>IgA>IgM), utilized diverse variable genes, and potently neutralized HPV 16 pseudoviruses in vitro despite possessing only average levels of somatic mutation. These findings suggest that the quadrivalent HPV vaccine provides an excellent model for studying the development of B cell memory; and, in the context of what is known about memory B cells elicited by influenza vaccination/infection, HIV-1 infection, or tetanus toxoid vaccination, indicates that extensive somatic hypermutation is not required to achieve potent vaccine-specific neutralizing antibody responses.
Author Summary
There is an urgent need to better understand how to reliably generate effective vaccines, particularly subunit vaccines, as certain pathogens are considered to pose too great of a safety risk to be developed as live, attenuated or killed vaccines (e.g., HIV-1). The human papillomavirus (HPV) vaccines are two of the most effective subunit vaccines ever developed and have continued to show protection against HPV associated disease up to and beyond five years post-vaccination. Moreover, the target population for these vaccines have essentially no pre-existing immunity to the HPV types covered by the vaccine; therefore, these vaccines provide an excellent model for studying the immunity elicited by a highly effective subunit vaccine. As the HPV vaccines, like most vaccines, protect by generating antibodies, we are interested in characterizing the memory B cells elicited by the HPV vaccine. Memory B cells help to sustain antibody levels over time by rapidly differentiating into antibody secreting cells upon pathogen re-exposure. Although previous studies have provided evidence that the HPV vaccines elicit memory B cells, they did not characterize these cells. Here, we have isolated HPV-specific memory B cells from adolescent females and women who received the quadrivalent HPV vaccine and have cloned antibodies from these cells. Importantly, we find that these antibodies potently inhibit HPV and that the memory B cells from which they derive exhibit hallmarks of long-lived memory B cells.
PMCID: PMC4199765  PMID: 25330199
3.  Risk of squamous cell skin cancer after organ transplant associated with antibodies to cutaneous papillomaviruses, polyomaviruses, and TMC6/8 (EVER1/2) variants 
Cancer Medicine  2014;3(5):1440-1447.
Squamous cell skin cancer (SCSC) disproportionately affects organ transplant recipients, and may be related to increased viral replication in the setting of immune suppression. We conducted a nested case–control study among transplant recipients to determine whether SCSC is associated with antibodies to cutaneous human papillomaviruses (HPV), to genes associated with a rare genetic susceptibility to HPV (TMC6/TMC8), or to human polyomaviruses (HPyV). Cases (n = 149) had histologically confirmed SCSC, and controls (n = 290) were individually matched to cases on time since transplant, type of transplant, gender, and race. All subjects had serum drawn immediately prior to transplant surgery. Antibodies to 25 cutaneous HPVs and six HPyVs were assayed by detection of binding to virus-like particles, and 11 TMC6/8 variants were genotyped. After correction for multiple comparisons, only antibodies to HPV37 were associated with SCSC (OR 2.0, 95% CI 1.2–3.4). Common genetic variants of TMC6/8 were not associated with SCSC, but three variants in TMC8 (rs12452890, rs412611, and rs7208422) were associated with greater seropositivity for species 2 betapapillomaviruses among controls. This study suggests that some betaHPVs, but not polyomaviruses, may play a role in the excess risk of SCSC among transplant recipients.
PMCID: PMC4302694  PMID: 24913986
Cutaneous human papillomavirus; epidemiology; organ transplant; polyomavirus; squamous cell skin cancer
4.  Risk of Cervical Cancer Associated with Chlamydia trachomatis Antibodies by Histology, HPV Type, and HPV Cofactors 
Human papillomavirus (HPV) is the central etiologic factor for cervical cancer, and prior studies suggested C. trachomatis may act as an HPV cofactor. We examined the C. trachomatis—cervical cancer association by serotype, histology, HPV type in the tumor, and other HPV cofactors. We conducted a population-based study in the Seattle-Puget Sound area of 302 women with invasive squamous cell carcinomas (SCC), 185 women with adenocarcinomas of the cervix (AC), and 318 HPV seropositive control women. The risk of SCC associated with antibodies to C. trachomatis was increased (OR 1.6, 95% CI 1.1–2.2) but not for AC (OR 1.0, 95% CI 0.6–1.5). This association was independent of HPV type in the SCC tumor tissue. There was an association between specific serotypes of C. trachomatis and SCC for 6 of the 10 serotypes: B (OR 3.6, 95% CI 1.5–8.4), D (OR 2.1, 95% CI 1.2–3.5), E (OR 2.4, 95% CI 1.4–3.9), G (OR 3.0, 95% CI 1.1–7.9), I (OR 4.2, 95% CI 1.5–11.7), and J (OR 2.3, 95% CI 1.0–5.1), but not for the 4 types (C, F, H, and K) that were present at very low prevalence in this population. There was an increased risk of SCC, but not AC, associated with antibodies to C. trachomatis that was not serotype specific.
PMCID: PMC4049152  PMID: 17096345
Chlamydia trachomatis; HPV; cervical cancer; histologic type; microimmunofluorescence
Journal of medical virology  2009;81(4):713-721.
Human papillomavirus (HPV) RNA levels may be a more sensitive early indicator of predisposition to carcinogenesis than DNA levels. We evaluated whether levels of HPV-16 and HPV-18 DNA and messenger RNA (mRNA) in newly detected infections are associated with cervical lesion development. Female university students were recruited from 1990-2004. Cervical samples for HPV DNA, HPV mRNA, and Papanicolaou testing were collected tri-annually, and women were referred for colposcopically-directed biopsy when indicated. Quantitative real-time polymerase chain reaction of L1 and E7 DNA and E7 mRNA was performed on samples from women with HPV-16 and HPV-18 infections that were incidently detected by consensus PCR. Adjusting for other HPV types, increasing E7 cervical HPV-16 mRNA levels at the time of incident HPV-16 DNA detection were associated with an increased risk of cervical intraepithelial neoplasia grade 2 to 3 (HR per 1 log10 increase in mRNA=6.36,95%CI=2.00-20.23). Increasing HPV-16 mRNA levels were also associated with an increased risk of cervical squamous intraepithelial lesions; the risk was highest at the incident positive visit and decreased over time. Neither HPV-16 E7 DNA levels nor HPV-18 E7 DNA nor mRNA levels were significantly associated with cervical lesion development. Report of >1 new partner in the past 8 months (relative to no new partners) was associated with increased HPV mRNA (viral level ratio [VLR]=10.05,95%CI=1.09-92.56) and increased HPV DNA (VLR=16.80,95%CI=1.46-193.01). In newly detected HPV-16 infections, increasing levels of E7 mRNA appear to be associated with an increased risk of developing cervical pre-cancer.
PMCID: PMC3984467  PMID: 19235870
HPV; viral load; mRNA; cervical pre-cancer
6.  No evidence for human papillomavirus in the etiology of colorectal polyps 
While some studies have reported detection of oncogenic human papillomavirus (HPV) in colorectal tumors, others have not.
We examined the association between oncogenic HPV infection and colorectal polyps in a case-control study of individuals with colorectal adenomas (n=167), hyperplastic polyps (n=87), and polyp-free controls (n=250). We performed real-time PCR for HPV-16 /18 DNA, and SPF PCR covering 43 HPV types, on lesional and normal colorectal tissue samples. Plasma antibodies for oncogenic HPV types were assessed via a bead-based multiplex Luminex assay.
HPV DNA was not found in any of the 609 successfully assayed colorectal tissue samples from adenomas, hyperplastic polyps, normal biopsies adjacent to polyps, or normal biopsies of the rectum of disease-free controls. Also, there was no association between HPV seropositivity for all oncogenic HPV types combined, for either polyp type, and for men or women. When analyses were restricted to participants without a previous history of polyps, among men [adenomas (n=31), hyperplastic polyps (n=28), and controls (n=68)], there was an association between seropositivity and hyperplastic polyps when all oncogenic HPV types were combined (odds ratio=3.0; 95% confidence interval: 1.1–7.9).
Overall, our findings do not support an etiologic relationship between HPV and colorectal adenomas or hyperplastic polyps; however, our finding suggesting an association between HPV seropositivity and hyperplastic polyps in men may warrant further investigations.
After stringent controls for contamination and three methods to assess HPV infection, we report no evidence for HPV in the etiology of colorectal neoplasia for either men or women.
PMCID: PMC3236024  PMID: 21817125
HPV; colorectal adenomas; hyperplastic polyps; DNA; antibodies
7.  Serum Antibody Response Following Genital α9 Human Papillomavirus Infection in Young Men 
The Journal of Infectious Diseases  2011;204(2):209-216.
Background. Although the prevalence of human papillomavirus (HPV) genital infection is similarly high in males and females, seroprevalence is lower in males. This study assessed rates and determinants of seroconversion after detection of genital HPV infection in young men.
Methods. We investigated HPV type-specific seroconversion in a cohort of heterosexual male university students who had an α9 HPV type (HPV-16, -31, -33, -35, -52, -58, or -67) detected in the genital tract (n = 156). HPV DNA and antibodies were detected and typed using liquid bead-based multiplex assays. We calculated seroconversion using Kaplan–Meier survival analysis. Cox proportional hazards models with generalized estimating equations were used to examine associations with seroconversion.
Results. Within 24 months of detecting genital HPV infection, type-specific seroconversion ranged from 4% for HPV–52 to 36% for HPV-31. HPV-16 seroconversion at 24 months was 13% (95% confidence interval [CI], 7%–25%). Among incident HPV infections, ever cigarette smoking and infection site(s) (shaft/scrotum and glans/urine vs shaft/scrotum or glans/urine only) were positively associated with type-specific seroconversion.
Conclusions. For each of the α9 HPV types, type-specific seroconversion within 24 months was observed in 36% or less of infected men. Seroconversion might be related to cigarette smoking and genital site(s) infected.
PMCID: PMC3114468  PMID: 21673030
8.  Antibody responses in oral fluid following administration of prophylactic human papillomavirus vaccines 
The Journal of Infectious Diseases  2009;200(9):1452-1455.
We sought to determine whether oral fluid can be used to assess serum human papillomavirus (HPV) antibody status by enrolling women who had received a prophylactic HPV-16 vaccine in a new follow-up study. After the prophylactic HPV-6/11/16/18 vaccine was licensed in the United States, we administered it to consenting participants. The sensitivity of oral fluid, treating serology as the gold standard, before and after administration of the quadrivalent vaccine was 49.6% (95% confidence interval [CI]: 42.0%–57.3%) and 100% (95% CI: 92.0%–100%), respectively. Oral fluid may have the potential to be used for monitoring of prophylactic HPV vaccines in the future.
PMCID: PMC3392559  PMID: 19698077
Human papillomavirus; Prophylactic vaccines; Antibodies; Oral fluid
9.  Antibodies to Merkel cell polyomavirus T-antigen oncoproteins reflect tumor burden in Merkel cell carcinoma patients 
Cancer research  2010;70(21):8388-8397.
Merkel cell polyomavirus (MCPyV) is a common infectious agent that is likely involved in the etiology of most Merkel cell carcinomas (MCCs). Serum antibodies recognizing the MCPyV capsid protein, VP1, are detectable at high titer in nearly all MCC patients, and remain stable over time. Although antibodies to the viral capsid indicate prior MCPyV infection, they provide limited clinical insight into MCC because they are also detected in more than half of the general population. We investigated whether antibodies recognizing MCPyV large and small tumor-associated antigens (T-Ags) would be more specifically associated with MCC. Among 530 population control subjects, these antibodies were present in only 0.9% and were of low titer. In contrast, among 205 MCC cases, 40.5% had serum IgG antibodies that recognize a portion of T-Ag shared between small and large T-Ags. Among cases, titers of T-Ag antibodies fell rapidly (approximately 8 fold/year) in patients whose cancer did not recur, while they rose rapidly in those with progressive disease. Importantly, in several patients who developed metastases, the rise in T-Ag titer preceded clinical detection of disease spread. These results suggest that antibodies recognizing T-Ag are relatively specifically associated with MCC, do not effectively protect against disease progression, and may serve as a clinically useful indicator of disease status.
PMCID: PMC2970647  PMID: 20959478
Merkel cell carcinoma; Merkel cell polyomavirus; MCPyV; antibody; biomarker
10.  Identification of species-specific and cross-reactive epitopes in human polyomavirus capsids using monoclonal antibodies 
The Journal of general virology  2009;90(Pt 3):634-639.
The human antibody response to polyomavirus capsid proteins is not well characterized. Recombinant BK virus (BKV), JC virus (JCV) and simian virus 40 (SV40) virus-like particles (VLP) were produced in a baculovirus system, and mouse monoclonal antibodies (mAbs) to these proteins were generated using standard methods. Nine of 12 BKV mAbs showed neutralizing activity. The non-neutralizing antibodies also bound BKV pseudocapsids in an ELISA binding assay. Most antibodies recognized conformational species-specific epitopes, but several exceptions were found: (i) BKV mAb BK-F11 cross-reacted with a linear buried epitope common to both JCV and SV40 pseudocapsids, (ii) two of six JCV antibodies (JC-6.7 and JC-7.9) and two of 13 SV40 antibodies (VP1-H2 and VP1-I2) recognized linear buried epitopes common to all three viruses and (iii) SV40 antibody VP1-E5 recognized a linear surface epitope on JCV pseudocapsids.
PMCID: PMC3075566  PMID: 19218208
11.  Age of Diagnosis of Squamous Cell Cervical Carcinoma and Early Sexual Experience 
Given the established links between young age at first intercourse (AFI), number of sex partners, high-risk human papillomavirus infection, and squamous cell cervical cancer (SCC), we hypothesized that women diagnosed with SCC at younger ages would be more likely to report young AFI than women diagnosed later in life.
We performed a population-based investigation among invasive SCC cases who were diagnosed between 1986 and 2004, were 22 to 53 years old, and lived in the metropolitan Seattle-Puget Sound region (n=333). Using multivariate linear regression, we estimated coefficients and 95% confidence intervals (CI) to assess the association between age at SCC diagnosis and AFI (<15, 15–18, ≥19) and number of sex partners before age 20 (0, 1, 2–4, 5–14, 15+), accounting for birth year and other factors. Interactions were assessed using the likelihood ratio test.
The interval between AFI and SCC diagnosis ranged from 4 to 35 years. In a multivariate model, compared to SCC cases reporting AFI≥19, the mean age of diagnosis was 3.1 years younger for SCC cases reporting AFI<15 (CI: −5.8, −0.5) and 2.6 years younger for SCC cases reporting AFI 15–18 years (CI: −4.6, −0.6). Although number of sex partners before age 20 was associated with age at SCC diagnosis in a crude analysis, the association was not independent of AFI. However, in the AFI≥19 and AFI<15 groups, differences in effect were seen by number of sex partners before age 20 (p for interaction=0.08), with the association remaining strong and significant only in the AFI<15 group that had 2 or more partners before age 20 (coefficient: −4.2, CI: −6.3, −2.1).
Among younger and middle-aged women with SCC, early age of diagnosis was associated with early AFI, though the effect appeared to be modified by number of sex partners before age 20.
PMCID: PMC2667560  PMID: 19318437
Cervical Carcinoma; Sexual Initiation; Age
12.  Association of Merkel Cell Polyomavirus–Specific Antibodies With Merkel Cell Carcinoma 
Merkel cell polyomavirus (MCPyV) has been detected in approximately 75% of patients with the rare skin cancer Merkel cell carcinoma. We investigated the prevalence of antibodies against MCPyV in the general population and the association between these antibodies and Merkel cell carcinoma.
Multiplex antibody-binding assays were used to assess levels of antibodies against polyomaviruses in plasma. MCPyV VP1 antibody levels were determined in plasma from 41 patients with Merkel cell carcinoma and 76 matched control subjects. MCPyV DNA was detected in tumor tissue specimens by quantitative polymerase chain reaction. Seroprevalence of polyomavirus-specific antibodies was determined in 451 control subjects. MCPyV strain–specific antibody recognition was investigated by replacing coding sequences from MCPyV strain 350 with those from MCPyV strain w162.
We found that 36 (88%) of 41 patients with Merkel cell carcinoma carried antibodies against VP1 from MCPyV w162 compared with 40 (53%) of the 76 control subjects (odds ratio adjusted for age and sex = 6.6, 95% confidence interval [CI] = 2.3 to 18.8). MCPyV DNA was detectable in 24 (77%) of the 31 Merkel cell carcinoma tumors available, with 22 (92%) of these 24 patients also carrying antibodies against MCPyV. Among 451 control subjects from the general population, prevalence of antibodies against human polyomaviruses was 92% (95% CI = 89% to 94%) for BK virus, 45% (95% CI = 40% to 50%) for JC virus, 98% (95% CI = 96% to 99%) for WU polyomavirus, 90% (95% CI = 87% to 93%) for KI polyomavirus, and 59% (95% CI = 55% to 64%) for MCPyV. Few case patients had reactivity against MCPyV strain 350; however, indistinguishable reactivities were found with VP1 from strain 350 carrying a double mutation (residues 288 and 316) and VP1 from strain w162.
Infection with MCPyV is common in the general population. MCPyV, but not other human polyomaviruses, appears to be associated with Merkel cell carcinoma.
PMCID: PMC2773184  PMID: 19776382
13.  Cervical and Vulvar Cancer Risk in Relation to Joint Effects of Cigarette Smoking and Genetic Variation in Interleukin 2 
Cigarette smoking is an established co-factor to human papillomavirus (HPV) in the development of cervical and vulvar squamous cell carcinoma (SCC), and may influence risk through an immunosuppressive pathway. Genetic variation in interleukin 2 (IL2), associated in some studies with inhibition of HPV-targeted immunity, may modify the effect of smoking on the risk of HPV-related anogenital cancers. We conducted a population-based case-only study to measure the departure from a multiplicative joint effect of cigarette smoking and IL2 variation on cervical and vulvar SCC. Genotyping of four IL2 tagSNPs (rs2069762, rs2069763, rs2069777, and rs2069778) was performed in 399 cervical and 486 vulvar SCC cases who had been interviewed regarding their smoking history. Compared to cases carrying the rs2069762 TT genotype, we observed significant departures from multiplicativity for smoking and carriership of the TG or GG genotypes in vulvar SCC risk (interaction odds ratio (IOR)=1.67, 95% confidence interval (CI): 1.16, 2.41). Carriership of one of three diplotypes together with cigarette smoking was associated with either a supra-multiplicative (TGCT/GGCC, IOR=2.09, 95% CI: 0.98, 4.46) or sub-multiplicative (TTCC/TGTC, IOR=0.37, 95% CI: 0.16, 0.85 or TGCT/TGCC, IOR=0.37, 95% CI: 0.15, 0.87) joint effect in vulvar cancer risk. For cervical SCC, departure from multiplicativity was observed for smokers homozygous for the rs2069763 variant allele (TT versus GG or GT genotypes) (IOR=1.87, 95% CI: 1.00, 3.48), and for carriership of the TTCC/TTCC diplotype, (IOR=2.08, 95% CI: 1.01, 4.30). These results suggest that cervical and vulvar SCC risk among cigarette smokers is modified by genetic variation in IL2.
PMCID: PMC2497438  PMID: 18628433
Cervical cancer; Vulvar cancer; Effect modification; Interleukin 2; Cigarette smoking
14.  Identification of Human Papillomavirus Type 16 L1 Surface Loops Required for Neutralization by Human Sera†  
Journal of Virology  2006;80(10):4664-4672.
The variable surface loops on human papillomavirus (HPV) virions required for type-specific neutralization by human sera remain poorly defined. To determine which loops are required for neutralization, a series of hybrid virus-like particles (VLPs) were used to adsorb neutralizing activity from HPV type 16 (HPV16)-reactive human sera before being tested in an HPV16 pseudovirion neutralization assay. The hybrid VLPs used were composed of L1 sequences of either HPV16 or HPV31, on which one or two regions were replaced with homologous sequences from the other type. The regions chosen for substitution were the five known loops that form surface epitopes recognized by monoclonal antibodies and two additional variable regions between residues 400 and 450. Pretreatment of human sera, previously found to react to HPV16 VLPs in enzyme-linked immunosorbent assays, with wild-type HPV16 VLPs and hybrid VLPs that retained the neutralizing epitopes reduced or eliminated the ability of sera to inhibit pseudovirus infection in vitro. Surprisingly, substitution of a single loop often ablated the ability of VLPs to adsorb neutralizing antibodies from human sera. However, for all sera tested, multiple surface loops were found to be important for neutralizing activity. Three regions, defined by loops DE, FG, and HI, were most frequently identified as being essential for binding by neutralizing antibodies. These observations are consistent with the existence of multiple neutralizing epitopes on the HPV virion surface.
PMCID: PMC1472072  PMID: 16641259
15.  Humoral Immune Response Recognizes a Complex Set of Epitopes on Human Papillomavirus Type 6 L1 Capsomers†  
Journal of Virology  2005;79(15):9503-9514.
Although epitope mapping has identified residues on the human papillomavirus (HPV) major capsid protein (L1) that are important for binding mouse monoclonal antibodies, epitopes recognized by human antibodies are not known. To map epitopes on HPV type 6 (HPV6) L1, surface-exposed loops were mutated to the corresponding sequence of HPV11 L1. HPV6 L1 capsomers had one to six regions mutated, including the BC, DE, EF, FG, and HI loops and the 139 C-terminal residues. After verifying proper conformation, hybrid capsomers were used in enzyme-linked immunosorbent assays with 36 HPV6-seropositive sera from women enrolled in a study of incident HPV infection. Twelve sera were HPV6 specific, while the remainder reacted with both HPV6 and HPV11 L1. By preadsorption studies, 6/11 of these sera were shown to be cross-reactive. Among the HPV6-specific sera there was no immunodominant epitope recognized by all sera. Six of the 12 sera recognized epitopes that contained residues from combinations of the BC, DE, and FG loops, one serum recognized an epitope that consisted partially of the C-terminal arm, and three sera recognized complex epitopes to which reactivity was eliminated by switching all five loops. Reactivity in two sera was not eliminated even with all six regions swapped. The patterns of epitope recognition did not change over time in women whose sera were examined 9 years after their first-seropositive visit.
PMCID: PMC1181614  PMID: 16014913
16.  Identification of a Human Papillomavirus Type 16-Specific Epitope on the C-Terminal Arm of the Major Capsid Protein L1 
Journal of Virology  2003;77(21):11625-11632.
To characterize epitopes on human papillomavirus (HPV) virus-like particles (VLPs), a panel of mutated HPV-16 VLPs was created. Each mutated VLP had residues substituted from HPV-31 or HPV-52 L1 sequences to the HPV-16 L1 backbone. Mutations were created on the HPV-31 and −52 L1 proteins to determine if HPV-16 type-specific recognition could be transferred. Correct folding of the mutated proteins was verified by resistance to trypsin digestion and by binding to one or more conformation-dependent monoclonal antibodies. Several of the antibodies tested were found to bind to regions already identified as being important for HPV VLP recognition (loops DE, EF, FG, and HI). Sequences at both ends of the long FG loop (amino acids 260 to 290) were required for both H16.V5 and H16.E70 reactivity. A new antibody-binding site was discovered on the C-terminal arm of L1 between positions 427 and 445. Recognition of these residues by the H16.U4 antibody suggests that this region is surface exposed and supports a recently proposed molecular model of HPV VLPs.
PMCID: PMC229369  PMID: 14557648

Results 1-16 (16)