Antibodies to human papillomavirus 16, 18, 58, and 6b major capsid proteins among Japanese females

Profiling of serum antibodies against human papillomavirus antigens in Korean women with cervical intraepithelial neoplasia and cervical cancer

Sero-epidemiological studies of human papillomavirus (HPV) have been undertaken over the last two decades. In this study, the prevalences of nine serum antibodies (anti-E6, E7 and L1 antibodies of HPV types 16, 18, and 58) were evaluated in normal (control) Korean women and women with cervical intraepithelial neoplasia (CIN) I, CIN II, CIN III, and cervical cancer. The frequencies of all types of anti-HPV antibodies were higher in the CIN stages and cervical cancer than in normal women, and those of anti-HPV16 E6 and E7, anti-HPV18 E6 and E7, and anti-HPV58 E7 antibodies were higher in the cervical cancer group than in the CIN stages. The frequencies of antibodies against HPV16, 18, and 58 E7 tended to increase with increasing severity of cervical lesions. However, there were few differences in the frequencies of antibodies against the L1 antigens of HPV16, 18 and 58 in cervical cancer versus CIN stages. The anti-HPV antibodies were detected in 26.5% of normal, 46.3% of CIN I, 62.5% of CIN II, 51.6% of CIN III, and 75% of cancers when any of the nine antigens was used as a criterion. Correlations between HPV DNA positivity and seropositivity for anti-HPV E6, E7, or L1 antibodies were found only in HPV16 DNA-positive cervical cancers for anti-HPV16 E6 and L1 antibodies. In addition, strong positive correlations in seropositivity were found between anti-HPV16 E7 and anti-HPV58 E7 antibodies, and between anti-HPV18 E6 and anti-HPV58 E6 antibodies. These findings should advance global profiling of the seroprevalences of antibodies against HPV antigens.

Human papillomavirus seropositivity and subsequent risk of HIV acquisition in rural South African women

OBJECTIVE

This study aimed to provide a population-based estimate of human papillomavirus (HPV) seropositivity for women in a rural African context and to evaluate the impact of HPV serostatus on subsequent acquisition of HIV outside a clinical setting.

DESIGN

A random sample of women participating in a longitudinal, population-based HIV survey combined with a case-control study.

METHODS

Blood samples of women participating in a single round of population-based HIV surveillance (N = 1049) in a rural South African population were used to measure vaccine-preventable HPV seropositivity (types 6, 11, 16, and 18) in the general population in 2010. Using results from the repeat HIV surveys, a case-control analysis was then performed comparing HPV sero-status in samples taken from HIV sero-converting women (prior to infection with HIV) against samples from HIV-uninfected, sexually-active controls matched 1:1 according to 5-year age band (377:377). Unconditional multivariable logistic regression with multiple imputations was used to control for sociodemographic and behavioral variables associated with HIV acquisition.

RESULTS

Human papillomavirus seropositivity in the population-based sample of women was 20.8% (95% confidence interval [CI], 18.3-23.4), and HIV prevalence was 27.6% (95% CI, 24.9-30.4). In the case-control analysis, allowing for variables known to be associated with HIV incidence, HPV seropositivity was associated with nearly 2.5 times the odds of subsequent acquisition of HIV (adjusted odds ratio, 2.33 [95% CI, 1.61-3.39]; P < 0.001).

CONCLUSIONS

These results suggest that HPV vaccination before or soon after sexual debut could lower HIV infection risk. Randomized trials that quantify the impact of HPV vaccination in girls on the risk of acquiring HIV are urgently required.

Human papillomavirus infection and the risk of cervical cancer in Japan

Infection with a high-risk human papillomavirus (HPV) is established as a major risk factor for cervical cancer. In Japan, eight HPV genotypes (16, 18, 31, 33, 35, 45, 52 and 58) confer a much higher risk of cervical cancer and its immediate premalignant lesions (cervical intraepithelial neoplasia grade 3 [CIN 3]) than do other high-risk and the low-risk HPV types. However, only a small fraction of infected women develop CIN 3 or invasive cervical cancer, suggesting the involvement of additional cofactors in cervical carcinogenesis. A multicenter prospective cohort study of Japanese women with low-grade cervical abnormalities has demonstrated that tobacco smoking is significantly associated with an increased risk of persistent low-grade cervical lesions, while the presence of human leukocyte antigen Class II DRB1*1302 protects against progression to CIN 3. Understanding the epidemiology of HPV infections and cervical cancer may improve prevention and lead to novel clinical management strategies for cervical precursor lesions. Viral and host factors that affect the risk of cervical cancer are discussed in this review.

Seroprevalence of human papillomavirus types 6, 11, 16 and 18 in Chinese women

BACKGROUND

Human papillomavirus (HPV) seroprevalence data have not previously been reported for different geographical regions of China. This study investigated the cross-sectional seroprevalence of antibodies to HPV 6, 11, 16, and 18 virus-like particles in Chinese women.

METHODS

Population-based samples of women were enrolled from 2006 to 2007 in 3 rural and 2 urban areas of China. Each consenting woman completed a questionnaire and provided a blood sample. Serum antibodies were detected using a competitive Luminex immunoassay that measures antibodies to type-specific, neutralizing epitopes on the virus-like particles.

RESULTS

A total of 4,731 women (median age 35, age range 14-54) were included, of which 4,211 were sexually active women (median age 37) and 520 virgins (median age 18). Low risk HPV 6 was the most common serotype detected (7.3%), followed by HPV 16 (5.6%), HPV 11 (2.9%), and HPV 18 (1.9%). Overall HPV seroprevalence to any type was significantly higher among sexually active women (15.8%) than virgins (2.5%) (P = 0.005). Overall seroprevalence among sexually active women gradually increased with age. Women from rural regions had significantly lower overall seroprevalence (Odds Ratio (OR) = 0.7; 95% CI: 0.6-0.9, versus metropolitan regions, P < 0.001). With increasing number of sexual partners, women were at higher risk of seropositivity of any type (OR = 2.6; 95% CI: 1.7-3.9 for > = 4 partners versus 1 partner, P < 0.001). Wives were at higher risk of seropositivity for HPV 16/18/6/11 when reporting having a husband who had an extramarital sexual relationship (OR = 2.0; 95% CI: 1.6-2.5, versus those whose husbands having no such relationship, P < 0.001). There was a strong association between HPV 16 seropositivity and presence of high-grade cervical lesions (OR = 6.5; 95% CI: 3.7-11.4, versus normal cervix, P < 0.001).

CONCLUSIONS

HPV seroprevalence differed significantly by age, geography, and sexual behavior within China, which all should be considered when implementing an optimal prophylactic HPV vaccination program in China.

Age-specific human papillomavirus antibody and deoxyribonucleic acid prevalence: a global review

PURPOSE

Global data on human papillomavirus (HPV) serological and deoxyribonucleic acid (DNA) prevalence are essential to optimize HPV prophylactic vaccination strategies.

METHODS

We conducted a global review of age-specific HPV antibody and studies with both antibody and DNA prevalence for HPV-16, -18, -6, and -11.

RESULTS

One hundred seventeen studies were included; participants' ages ranged from several hours to >90 years. HPV-16 seroprevalence was generally higher in Africa, Central and South America, and North America, more prevalent among women than among men, and peaked around ages 25-40 years. HPV-18 seroprevalence was generally lower than HPV-16 with a later age peak. Data were limited for HPV-6 and -11, both of which peaked at ages similar to HPV-18. Among 9-26-year-old females, HPV-16 seroprevalence ranged from 0%-31% in North America, 21%-30% in Africa, 0%-23% in Asia/Australia, 0%-33% in Europe, and 13%-43% in Central and South America. HPV-16/-18 DNA prevalence peaked 10-15 years before corresponding HPV-16/-18 antibody prevalence.

CONCLUSIONS

Females within the HPV vaccine-eligible age-group (9-26 years) had a range of dual HPV-16 DNA and serology negativity from 81%-87%, whereas 90%-98% were HPV-16 DNA negative. Serology and DNA data are lacking worldwide for females younger than age 15 years, the prime target group for vaccination.

Population-based human papillomavirus 16, 18, 6 and 11 DNA positivity and seropositivity in Chinese women

To optimize HPV vaccination implementation at the population-level in China, data are needed on age-specific HPV 16, 18, 6 and 11 prevalence. This cross-sectional, population-based study evaluated the age- and type-specific HPV 16, 18, 6 and 11 prevalence of DNA and serum antibodies among women in China. From July 2006 to April 2007, 17-54 year old women from three rural provinces (Xinjiang, Shanxi and Henan) and two cities (Beijing and Shanghai) provided cervical exfoliated cells for HPV DNA and liquid-based cervical cytology (SurePath). High- and low-risk HPV types were detected with HC-II (Qiagen), with genotyping of HPV-positive samples using Linear Array (Roche). HPV 16, 18, 6 and 11 serum antibodies were detected using a Luminex-based, competitive immunoassay (Merck). A total of 4,206 women with DNA and serum antibody results were included. HPV 16 DNA prevalence peaked in women aged 30-34 (4.2%) and 45-49 yr (3.8%), while HPV 18 DNA prevalence peaked at ages 40-44 yr (1.3%). Most women were dually DNA and serum antibody negative: HPV 16 (92.2%), 18 (97.2%), HPV 16 and 18 (90.2%), 6 (92.0%), 11 (96.6%), 6 and 11(89.9%) and HPV 16, 18, 6 and 11 (82.5%). Future national HPV vaccination programs in China should target younger women due to increased exposure to HPV types 16, 18, 6 and 11 with increasing age. Cumulative exposure of HPV may be underreported in this population, as cross-sectional data do not accurately reflect exposure to HPV infections over time.

Role of human papillomavirus types 16, 18, and 52 in recurrent cystitis and urinary bladder cancer among Egyptian patients

BACKGROUND

Bladder cancer is a common malignancy in Egypt. Human papillomavirus (HPV) could have a possible etiologic role in bladder carcinogenesis. We aimed to estimate the prevalence of HPV-16, -18, and -52 in Egyptian patients with bladder cancer or recurrent cystitis, and to study the correlation of type-specific HPV-immunoglobulin (Ig)G with polymerase chain reaction (PCR) results and different clinicopathologic parameters.

METHODS

This study was conducted on 60 inpatients of the Urosurgery Department at the Theodor Bilharz Research Institute (TBRI), who were identified histopathologically and clinically as cancer bladder (group I, 20 patients), cystitis (group II, 24 patients), and cancer bladder with cystitis (group III, 16 patients), and a fourth group of 20 healthy control subjects (for serologic testing). Patients were subjected to detection of HPV-16 and -18 DNA by PCR on bladder tissue biopsies (BTB) and buffy coat cells (BCC) and serum IgG antibodies to L1 capsids of HPV-16 and -52 IgG by enzyme-linked immunosorbent assay (ELISA).

RESULTS

HPV-16 and -18 DNA were detected in BTB (30% and 10%, respectively) with significantly higher rates (44.4%) in bladder cancer than cystitis cases (11.11%), with significant association with schistosomal affection (78.6% and 25%, respectively) and recurrence (48%, HPV-16). There was a significant association of transitional cell carcinoma (TCC) with HPV-16 in 69.2% and 61.1% of BCC and BTB, respectively. Multiple HPV types 16, 18, and 52 were significantly higher than single types (79.2% and 20.8%, respectively). The observed absolute association between seropositivity of HPV-52 (11.7%) and HPV-16 (26.7%) was significantly associated with TCC in patient groups only.

CONCLUSION

Our study confirmed the significant association of HPV-16, -18 and -52 with bladder cancer in Egyptian patients, with the suggestion of viral synergistic action in bladder carcinogenesis. Such HPV types were significantly associated with TCC tumors of low grade and high stage, with schistosomal affection and recurrence tendency. HPV serology would pave the way for better management and follow-up of patients and for optimal design and evaluation of HPV vaccination.

IgG antibodies to HPV16, 52, 58 and 6 L1-capsids and spontaneous regression of cervical intraepithelial neoplasia

To identify the predictive markers for spontaneous regression of cervical intraepithelial neoplasia (CIN), we examined whether IgG antibody responses to common human papillomavirus (HPV) L1-capsids correlate with CIN regression. In a cohort study, a total of 116 Japanese women with CIN grade I/II were tested for cervical HPV DNA and serum IgG antibodies to HPV16/52/58/6 L1-capsids. Our data suggest that baseline IgG reactivities to HPV L1-capsids do not serve as a predictive marker of CIN regression, in contrast to histological CIN grades and HPV DNA status.

Human papillomavirus 16 minor capsid protein L2 helps capsomeres assemble independently of intercapsomeric disulfide bonding

The human papillomavirus (HPV) capsomeres (pentamers of major capsid protein L1), which constitute along with L2 the virion capsid, can assemble themselves alone into the L1-capsid particles in vivo and in vitro, depending on intercapsomeric disulfide bonds. To study a possible role of L2 in capsid assembly, we examined the interaction between HPV16 L2 and capsomeres under the conditions that inhibit the formation of disulfide bonds in vitro and in vivo. The purified L2 bound to free capsomeres prepared by disassembling L1-capsids but not to the L1-capsids in vitro. And the L2 was found to help capsomeres assemble into smaller capsid-like particles independently of intercapsomeric disulfide bonding. Similar particles were obtained from the Sf9 cells co-infected with baculoviruses expressing L2 and an L1 mutant that lacks a C-terminal cysteine (C428S) and can form capsomeres but no capsids when expressed alone. These findings suggest that L2, which is known to bind both viral DNA and L1, may contribute to the formation of the virion by linking viral DNA and capsomeres and by helping capsomeres assemble before the virion capsid structure is completed by dintercapsomeric disulfide bonding.

Safety and immunogenicity of a peptide containing the cross-neutralization epitope of HPV16 L2 administered nasally in healthy volunteers

Amino acid (aa) 108-120 of L2 protein of human papillomavirus (HPV) type 16 contains a cross-neutralization epitope against genital HPV. We designed a placebo-controlled trial in healthy adults to evaluate the safety and immunogenicity of a synthetic peptide consisting of the aa 108-120 of HPV16 L2 (L2-108/120) region. A total of 13 volunteers were given nasal inoculations with 0.1 (n=5) or 0.5mg (n=5) doses of the peptides or placebo (n=3) without adjuvant at weeks 0, 4, and 12. Sera were collected before inoculation and at 6, 16 and 36 weeks. The inoculation caused no serious local and systemic complications. The inoculation generated anti-L2 antibodies binding to both HPV16 and 52 L1/L2-capsids in four of the five recipients in the 0.5mg group. Sera of the four recipients showed neutralizing activities against HPV16 and 52. Serological responses to the peptides were not found in the 0.1mg group and the placebo group recipients. This study suggests the L2-108/120 peptide is tolerable in humans and has the potential as a broad-spectrum prophylactic vaccine against genital HPV.

Mutational analysis of human papillomavirus type 16 major capsid protein L1: the cysteines affecting the intermolecular bonding and structure of L1-capsids

Human papillomavirus 16 major capsid protein L1 (composed of 505 amino acids (aa) including 12 cysteines) assembles by itself into virion-like icosahedral particles (L1-capsids), each of which is dissociated into 72 pentameric capsomeres when intermolecular disulfide bonds are disrupted. To identify the cysteines affecting the bonding and the structural integrity of the L1-capsids, we constructed a series of L1 mutants with substitution of serine for cysteine, which were expressed from recombinant baculoviruses in the insect Sf9 cells. From infected cells, the self-assembled L1-capsid fractions were purified by CsCl-equilibrium centrifugation and examined for velocity sedimentation profiles, for the presence of intermolecular bonding by SDS-PAGE with or without a reducing agent, for morphology under an electron microscope, and for susceptibility to trypsin digestion. Mutants C175S (C at aa 175 was replaced with S) and C185S were sedimented in sucrose-density gradients slightly slower than the wild type (WT) capsids, and mutant C428S stayed near the top as WT-capsomeres did. In the nonreducing SDS gel, where WT-capsids were separated into two bands of L1-trimers and L1-dimers, the C175S-trimer band was not detected, the C185S-dimer band was much less dense, and the C428S-trimer and C428S-dimer bands were not detected. Thus, it seems likely that C175, C185, and C428 are involved in L1 trimerization, in L1 dimerization, and in both, respectively. Morphologically, the C175S, C185S, and C428S fractions appeared to consist mostly of heterogeneous rod-shaped tubules, of smaller spherical particles, and of only capsomeres, respectively, whereas C102S, C229S, and C379S resembled WT. The C161S, C175S, C185S, C229S, C379S, and C428S capsids were more sensitive to degradation caused by trypsin than WT. The results indicate that C175, C185, and C428 are required for the normal assembly of L1-capsids through trimerization and dimerization of L1 bound by the intercapsomeric disulfide bonds between cysteines, and that C161, C229, and C379 are necessary for the integrity of L1-capsids probably through intramolecular bonding.

IgG antibodies to human papillomavirus 16, 52, 58, and 6 L1 capsids: case-control study of cervical intraepithelial neoplasia in Japan

In Japan, human papillomavirus (HPV) 16, 52, and 58 are most commonly associated with cervical intraepithelial neoplasia (CIN). By contrast, HPV6 is primarily associated with genital warts. This study was designed to evaluate the association between IgG antibody responses to common HPVs and the risk of CIN development within a Japanese population. CIN cases (n = 141) and controls (n = 109) were tested for cervical HPV DNA and serum IgG antibodies to L1 capsids of HPV16, 52, 58, and 6. Seropositivity to HPV16, 52, and 58 L1 capsids was significantly higher in CIN cases than in controls: 27%, 21%, and 31% versus 16%, 11%, and 11%, respectively (P < 0.05). HPV6 L1 seropositivity was not significantly associated with CIN lesions (P = 0.11). Presence of viral DNA for either HPV16, 52, or 58 correlated with a significant antibody response against the homologous L1 capsids but not heterologous L1 capsids. Furthermore, seropositivity to multiple types of HPV16, 52, and 58 was more strongly associated with an increased risk of CIN development than seropositivity to a single type (P for trend <0.001). These findings indicate that IgG antibodies to L1 capsids of HPV16, 52, and 58 represent an increased risk of CIN development, with antibodies to multiple types being indicative of a further increase in risk. The presence of CIN lesions in women with seropositivity to multiple types suggests that viral exposure to a given type may not be protective against infections by other types and subsequent CIN development.

Seroresponses to virus-like particles of human papillomavirus types 16, 18, 31, 33, and 45 in San people of Southern Africa

Virus-like particles (VLPs) of the high-risk human papillomavirus (HPV) types 16, 18, 31, 33, and 45 were used as antigen in enzyme-linked immunosorbent assay (ELISA) to determine the prevalence of serum IgG in a group of San people originally from Namibia, now residing in South Africa. The San children had low seroprevalence to all VLP types, but 26/115 (22.6%) of the children were seropositive to at least 1 VLP type. Among the adults, seroprevalence was significantly higher. The seroprevalence of antibodies in 101 San women to VLP-16 was 16.8%, VLP-18 18.8%, VLP-31 12.9%, VLP-33 17.8%, and VLP-45 22.8%. Five of the 11 men were seropositive: 2 for VLP-31, 1 for VLP-18, 1 for VLP-33, and 1 for VLP-45. Seroreactivity appeared to be type specific, except possibly to VLP-18 and -45. Of the adults, 50.5% were seropositive to at least 1 VLP type and 24.8% were seropositive to >1 VLP type. From this study, it is concluded that the San people are exposed to HPV-16, -18, -31, -33, and -45, with antibodies to VLP-45 being the most prevalent.

DNA vaccination of mice with plasmid expressing human papillomavirus 6 major capsid protein L1 elicits type-specific antibodies neutralizing pseudovirions constructed in vitro

Human papillomavirus 6 (HPV 6) causes benign condylomata. As a model for HPV vaccine development, we tested a HPV 6 DNA vaccine candidate, constructed by subcloning the major capsid protein (L1) gene into an expression plasmid having the cytomegalovirus promoter, for its immunogenicity in BALB/c mice. Three intracutaneous inoculations of the plasmid with a gene gun at 2-week intervals elicited anti-L1 serum antibodies. The antibodies were found to recognize highly type-specific, conformation-dependent epitopes, including those to neutralize pseudovirions capable of inducing beta-galactosidase in infected monkey COS-1 cells. The data support the idea that immunization with DNA capable of expressing HPV L1 can be used as an HPV vaccine strategy for humans.

Genetic alterations on chromosome 17p associated with response to radiotherapy in bulky cervical cancer

Chromosome 17 alterations are found in more cancers than those of any other chromosome, and frequently involve the p53 gene on 17p13. The aim of this study was to identify the correlations between the presence of loss of heterozygosity (LOH) and microsatellite instability (MI) on chromosome 17p13 in patients with cervical cancer and the patients' response to radiotherapy. A total of 50 patients were treated with definitive radiotherapy. We performed biopsies and took specimens from the tumour and venous blood of all patients. Tumour and normal DNAs were analysed by polymerase chain reaction for genetic losses and instability at three polymorphic microsatellite loci mapped to 17p13. Nineteen of the 50 tumours (38%) displayed a genetic alteration (GA) on 17p13, 16 (32%) were found to have LOH, and three (6%) showed MI. The sizes of the tumours of the GA-positive patients were significantly greater than those of the GA-negative patients (P = 0.009). The mean tumour diameter of all patients was 6 +/- 2.4 cm. We divided the patients into those with tumours smaller than 6 cm in diameter (n = 26) and those with tumours equal to or greater than 6 cm in diameter (n = 24). The former group survived significantly longer compared to the latter group (P = 0.0002). Among the patients with < 6 cm tumours, all six GA-positive patients are alive with no evidence of disease (NED), whereas of the 20 GA-negative patients, 18 have NED and two are alive with disease (AWD) or suffered cancer-caused death (CD). Thus, there was no correlation between GA and radiotherapy response in the tumours smaller than 6 cm. However, among the patients with > or = 6 cm tumours, two of the GA-positive patients have NED and 11 are AWD/CD, whereas seven of the GA-negative patients have NED and four are AWD/CD. Among the patients with > or = 6 cm tumours, the response to radiotherapy of the GA-positive patients were significantly poorer than those of the GA-negative patients (P = 0.02). In addition, the GA-negative patients survived significantly longer compared to the GA-positive patients (P = 0.026). The results of this study suggest that GA increases with tumour growth. Improved success in the management of bulky cervical cancer requires a better understanding of its biological behaviour.

Common neutralization epitope in minor capsid protein L2 of human papillomavirus types 16 and 6

Studies of virus neutralization by antibody are a prerequisite for development of a prophylactic vaccine strategy against human papillomaviruses (HPVs). Using HPV16 and -6 pseudovirions capable of inducing beta-galactosidase in infected monkey COS-1 cells, we examined the neutralizing activity of mouse monoclonal antibodies (MAbs) that recognize surface epitopes in HPV16 minor capsid protein L2. Two MAbs binding to a synthetic peptide with the HPV16 L2 sequence of amino acids (aa) 108 to 120 were found to inhibit pseudoinfections with HPV16 as well as HPV6. Antisera raised by immunizing BALB/c mice with the synthetic peptide had a cross-neutralizing activity similar to that of the MAb. The data indicate that HPV16 and -6 have a common cross-neutralization epitope (located within aa 108 to 120 of L2 in HPV16), suggesting that this epitope may be shared by other genital HPVs.

Balance of IgG subclasses toward human papillomavirus type 16 (HPV16) L1-capsids is a possible predictor for the regression of HPV16-positive cervical intraepithelial neoplasia

Human papillomavirus type 16 (HPV16) is known to be a major causative agent of cervical cancer. To test the hypothesis that an enhanced Th1 response favors the natural course of cervical intraepithelial neoplasia (CIN), we measured IgG subclasses toward HPV16 L1-capsids because IgG1/IgG2 balance reflects Th2 and Th1 responses, respectively. We examined IgG2/IgG1 ratios in sera from 67 anti-HPV16 L1-positive women; 18 were cytologically normal women, 29 were CIN patients, and 20 were cervical cancer patients. The IgG2 dominance (IgG2/IgG1 ratio >1) was observed in 94, 48, and 5%, respectively (p < 0.001). The regression rate of CIN lesions was significantly different between patients with and without IgG2 dominance: 83.3% (5/6) versus 16.7% (1/6), respectively (p < 0.05). These findings raise the possibility that IgG2 dominance toward HPV16 L1-capsids, i.e., Th1 dominance, may be a useful marker to predict viral clearance or the regression of HPV16-positive CIN.

In vitro construction of pseudovirions of human papillomavirus type 16: incorporation of plasmid DNA into reassembled L1/L2 capsids

Lack of permissive and productive cell cultures for the human papillomaviruses (HPVs) has hindered the study of virus-neutralizing antibodies and infection. We developed a cell-free system generating infectious HPV16 pseudovirions. HPV16 L1/L2 capsids, which had been self-assembled in insect cells (Sf9) expressing virion proteins L1 and L2, were disassembled with 2-mercaptoethanol (2-ME), a reducing agent, and reassembled by removal of 2-ME in the presence of a beta-galactosidase expression plasmid. Plasmid DNA purified together with the reassembled capsids was resistant to DNase I digestion. The reassembled pseudovirions mediated DNA transfer to COS-1 cells, as monitored by induced beta-galactosidase activity. Transfer was inhibited by anti-HPV16 L1 antiserum but not by antisera against L1s of HPV6 and HPV18. Construction in vitro of HPV pseudovirions containing marker plasmids would be potentially useful in developing methods to assay virus-neutralizing antibodies and to transfer exogenous genes to HPV-susceptible cells.

A surface immunodeterminant of human papillomavirus type 16 minor capsid protein L2

We used human papillomavirus type 16 (HPV-16) particles composed of capsid proteins L1 and L2 (L1/L2 capsids) as an antigen to produce mouse monoclonal antibodies (MAbs). Of 18 MAbs recognizing surface epitopes of L1/L2 capsids, 1 was an anti-L1 MAb and 17 were anti-L2 MAbs. Seven of 11 anti-L2 MAbs recognizing linear epitopes wer found to bind to a synthetic peptide with an HPV-16 L2 sequence of amino acids (aa) 69-81, which is within a highly conserved region among different HPVs. The synthetic peptide reacted with the human sera that had been shown to be positive for an antibody against HPV-16, -18, -58, or -6b capsids composed of L1 alone. The data suggest that the HPV-16 L2 region of aa 69-81 contains a type-common immunodeterminant exposed on the surface of HPV virions.