Papillomavirus pseudovirions packaged with the L2 gene induce cross-neutralizing antibodies

BACKGROUND

Current vaccines against HPVs are constituted of L1 protein self-assembled into virus-like particles (VLPs) and they have been shown to protect against natural HPV16 and HPV18 infections and associated lesions. In addition, limited cross-protection has been observed against closely related types. Immunization with L2 protein in animal models has been shown to provide cross-protection against distant papillomavirus types, suggesting that the L2 protein contains cross-neutralizing epitopes. However, vaccination with L2 protein or L2 peptides does not induce high titers of anti-L2 antibodies. In order to develop a vaccine with the potential to protect against other high-risk HPV types, we have produced HPV58 pseudovirions encoding the HPV31 L2 protein and compared their capacity to induce cross-neutralizing antibodies with that of HPV L1 and HPV L1/L2 VLPs.

METHODS

The titers of neutralizing antibodies against HPV16, HPV18, HPV31 and HPV58 induced in Balb/c mice were compared after immunization with L2-containing vaccines.

RESULTS

Low titers of cross-neutralizing antibodies were detected in mice when immunized with L1/L2 VLPs, and the highest levels of cross-neutralizing antibodies were observed in mice immunized with HPV 58 L1/L2 pseudovirions encoding the HPV 31 L2 protein.

CONCLUSIONS

The results obtained indicate that high levels of cross-neutralizing antibodies are only observed after immunization with pseudovirions encoding the L2 protein. HPV pseudovirions thus represent a possible new strategy for the generation of a broad-spectrum vaccine to protect against high-risk HPVs and associated neoplasia.

Identification of neutralizing conformational epitopes on the human papillomavirus type 31 major capsid protein and functional implications

The aim of this study was to characterize the conformational neutralizing epitopes of the major capsid protein of human papillomavirus type 31. Analysis of the epitopes was performed by competitive epitope mapping using 15 anti-HPV31 and by reactivity analysis using a HPV31 mutant with an insertion of a seven-amino acid motif within the FG loop of the capsid protein. Fine mapping of neutralizing conformational epitopes on HPV L1 was analyzed by a new approach using a system displaying a combinatorial library of constrained peptides exposed on E. coli flagella. The findings demonstrate that the HPV31 FG loop is dense in neutralizing epitopes and suggest that HPV31 MAbs bind to overlapping but distinct epitopes on the central part of the FG loop, in agreement with the exposure of the FG loop on the surface of HPV VLPs, and thus confirming that neutralizing antibodies are mainly located on the tip of capsomeres. In addition, we identified a crossreacting and partially crossneutralizing conformational epitope on the relatively well conserved N-terminal part of the FG loop. Moreover, our findings support the hypothesis that there is no correlation between neutralization and the ability of MAbs to inhibit VLP binding to heparan sulfate, and confirm that the blocking of virus attachment to the extracellular matrix is an important mechanism of neutralization.

[HPV immunization for the prevention of cervical cancer]

CONTEXT

Human Papillomaviruses (HPV) infect epithelial cells of the skin and mucosae. Mucosal high-risk HPV types (mainly HPV 16 and 18) are involved in the development of cervical cancer, one of the most common cancers in young women. HPV infection is usually asymptomatic and clears spontaneously, but 10 - 15 % of high-risk HPV infections are persistent and increase the risk of precancerous and cancerous lesions of the cervix. Two HPV vaccines have been licensed to provide protection against cervical cancer.

OBJECTIVES

To report the different aspects of HPV infection in order to improve the understanding of the particular problems of HPV vaccination and to review the most recent findings related to HPV vaccines, particularly regarding the protective efficacy of vaccines and the roles of adjuvants and immune response in protection.

METHODS

Articles were selected from the PubMed database (National Library of Medicine- National Institute of Health) with the following Keywords "HPV", "Prevention", "HPV vaccines", "Immune response", "Antibody". Abstracts of oral presentations from international meetings were also selected for the more recent findings. a critical analysis of the majority of papers published was undertaken and relevant information summarized.

RESULTS

Virus-like particle production by expressing the major protein of the HPV capsid was carried out in the early 90's, leading to the recent development of two HPV vaccines. These vaccines are now licensed in many countries and have been demonstrated to be highly immunogenic. In subjects that are non-infected at the time of vaccination, HPV vaccines are highly effective in preventing persistent HPV 16 - 18 infections (90 %) and precursors lesions of cervical cancer associated with these two HPV types (close to 100 %). Clinical trials have also confirmed that HPV vaccines are well tolerated by recipients.

CONCLUSIONS

The present paper is a detailed review published in French on HPV vaccines, their efficacy in the prevention of HPV infections and unresolved questions regarding the use of HPV vaccines. This report also includes biological and immunological information to improve the understanding of HPV vaccination.

Merkel cell polyomavirus strains in patients with merkel cell carcinoma

We investigated whether Merkel cell carcinoma (MCC) patients in France carry Merkel cell polyomavirus (MCPyV) and then identified strain variations. All frozen MCC specimens and 45% of formalin-fixed and paraffin-embedded specimens, but none of the non-MCC neuroendocrine carcinomas specimens, had MCPyV. Strains from France and the United States were similar.

Human papillomavirus L1 protein expressed in tobacco chloroplasts self-assembles into virus-like particles that are highly immunogenic

Cervical cancer is the second most prevalent cancer in women worldwide. It is linked to infection with human papillomavirus (HPV). As the virus cannot be propagated in culture, vaccines based on virus-like particles have been developed and recently marketed. However, their high costs constitute an important drawback for widespread use in developing countries, where the incidence of cervical cancer is highest. In a search for alternative production systems, the major structural protein of the HPV-16 capsid, L1, was expressed in tobacco chloroplasts. A very high yield of production was achieved in mature plants (approximately 3 mg L1/g fresh weight; equivalent to 24% of total soluble protein). This is the highest expression level of HPV L1 protein reported in plants. A single mature plant synthesized approximately 240 mg of L1. The chloroplast-derived L1 protein displayed conformation-specific epitopes and assembled into virus-like particles, visible by transmission electron microscopy. Furthermore, leaf protein extracts from L1 transgenic plants were highly immunogenic in mice after intraperitoneal injection, and neutralizing antibodies were detected. Taken together, these results predict a promising future for the development of a plant-based vaccine against HPV.

BK virus and cancer in Uganda

As part of an epidemiological study of cancer in Uganda, we investigated the titre of antibodies against BK virus among 821 people with different cancer types and benign tumours. Among study participants, 790 were considered seropositive for anti-BK virus antibodies and all analyses were conducted on transformed data. The mean optical density (a measure of antibody titre) for all patients combined (including the 31 who were considered seronegative) was 1.03 (standard error 0.01), but was 5% higher in women than in men (P=0.05), and 8% higher among HIV seropositive than seronegative people (P=0.002). Otherwise, there were few consistent associations between anti-BK virus antibodies and any social and lifestyle factor investigated. Differences in the mean optical density for each cancer type were estimated using multivariate analysis of variance with adjustment for sex, age group and HIV serostatus, using all other patients as controls. The mean optical density was about 17% lower among those with oral cancer (optical density 0.86, standard error 0.06; P=0.01, based on 30 patients) and about 20% higher among those with prostate cancer (optical density 1.22, standard error 0.09; P=0.01, based on 11 cases) than among all other patients combined. The number of cases of each cancer was too small to exclude the possibility of these findings arising by chance. No other cancer site or type was significantly associated with low, or with high anti-BK virus antibody titres.

[Human papillomavirus (HPV) vaccines]

In the last 15 years, fifteen of the human papillomaviruses (HPVs) that infect the genital tract have been recognized as the etiological agents of cervical cancer. Cervical cancer is thus a cancer that could be prevented by immuniza- tion. The recently licensed HPV subunit vaccine and the availability of another prophylactic vaccine in the near future for types 16 and 18 make this a realizable goal. The safety, immunogenicity and efficacy demonstrated for two vaccines are very promising. Phase I and phase II clinical trials have determined the tolerance, immunogenicity, dose and schedule of injections and phase IIb and phase III clinical trials have demonstrated the high efficacy of these vaccines. More than 80 % protection against incident infections was observed and close to 100 % protection was observed against persistent infections associated with cervical lesions. Anti-HPV antibodies persisted for 4-5 years, with antibody titers 5 to 17 times higher than observed in control subjects with anti-HPV antibodies ac- quired after natural infection. However, there are still some unresolved questions such as duration of protection, need for booster dose, protective level of anti-HPV antibodies, and whether there is protection against infection with HPV types closely related to HPV-16 and HPV-18 but not incorporated in the vac- cines. For a maximum efficacy, papillomavirus vaccines must be administered to pre-adolescents and adolescents before the beginning of sexual activity. Vaccine coverage and hence the overall efficacy of vaccination against HPV will depend on public health policies, social attitudes and cost of the vaccines. HPV immu- nization should significantly reduce the incidence of cervical cancers in 10 to 30 years, and should reduce the number of treatments due to a significant reduction in precancerous lesions in the shorter term. These vaccines also have the potential to reduce the incidence of other cancers such as anal, vulval, vaginal, and penial cancers for which the HPV prevalence is lower or the association with HPV infection is weaker. HPV vaccination and screening of precancerous cervical lesions are complementary measures and the implementation of HPV vaccination is an opportunity to strengthen the health policies for prevention of cervical cancer.

Chapter 15: HPV vaccine use in the developing world

Human papillomavirus (HPV)-related morbidity and mortality from cervical cancer primarily occurs in the developing world, where, unfortunately, access to vaccines in general, and expensive newer vaccines in particular, is often more limited than in the industrialized world. In addition, secondary prevention methods such as HPV screening, Pap testing, or visual inspection are uncommon in the developing world. The HPV vaccine will be first introduced into the industrialized countries and it will then, over the course of time, become used in the developing countries. HPV vaccine should be introduced in the framework of comprehensive cervical cancer control, and offers an opportunity to bring together a wide range of constituents who have not to date worked closely on vaccination. Ultimately, the decision of whether and when a vaccine will be introduced will depend on individual countries. To prepare for decisions on HPV vaccine use, the sexual and reproductive health (SRH; including adolescent health), immunization, and cancer control communities need to work together to analyze the appropriate data and build international and national consensus. The timeframe for other newer vaccines, such as hepatitis B and Hib, has been measured in decades, and the challenge to the public sector is to greatly shorten the time needed to make HPV vaccines available and affordable for the developing world, where their impact will be greatest.

Identification of type-specific and cross-reactive neutralizing conformational epitopes on the major capsid protein of human papillomavirus type 31

The majority of the neutralizing epitopes of papillomaviruses (PV) are conformation-specific and have not been fully characterised. Studies have, to date, been limited to a few HPV types only. We analysed the epitopes on the major capsid protein (L1) of Human papillomavirus (HPV) type 31 using monoclonal antibodies (MAbs) generated against HPV-31 virus-like particles (VLPs). The type-specific MAbs against HPV-31 were all found to be neutralizing and recognized conformation-dependent epitopes. Two other MAbs directed against a conformational epitope were found to be cross-reactive with other HPV types, and one of them was found to be cross-neutralizing. Cross-reactive antibodies were further investigated using wild-type HPV-16 L1 VLPs and two mutants. The results obtained suggested the existence of a cross-neutralizing conformational epitope at the N-terminal part of the FG loop of the major capsid protein, and the other four cross-reactive MAbs recognized epitopes also located at the N-terminal part of the FG loop.

Antibody levels against BK virus and prostate, kidney and bladder cancers in the EPIC-Oxford cohort

In a case–control study nested within the EPIC-Oxford cohort, there were no statistically significant differences in the prevalence or titre of antibodies against BK virus measured in plasma taken prior to diagnosis between cases with cancer of the prostate (n=31), kidney (n=5) or bladder (n=9) and controls (n=45).

Genetic diversity of hepatitis B virus strains derived worldwide: genotypes, subgenotypes, and HBsAg subtypes

Sequences of 234 complete genomes and 631 hepatitis B surface antigen genes were used to assess the worldwide diversity of hepatitis B virus (HBV). Apart from the described two subgenotypes each for A and F, also B, C, and D divided into four subgenotypes each in the analysis of complete genomes supported by significant bootstrap values. The subgenotypes of B and C differed in their geographical distribution, with B1 dominating in Japan, B2 in China and Vietnam, B3 confined to Indonesia, and B4 confined to Vietnam, all strains specifying subtype ayw1. Subgenotype C1 was common in Japan, Korea, and China; C2 in China, South-East Asia, and Bangladesh, and C3 in the Oceania comprising strains specifying adrq-, and C4 specifying ayw3 is encountered in Aborigines from Australia. This pattern of defined geographical distribution was less evident for D1-D4, where the subgenotypes were widely spread in Europe, Africa, and Asia, possibly due to their divergence having occurred a longer time ago than for genotypes B and C, with D4 being the first split and still the dominating subgenotype of D in the Oceania. The genetic diversity of HBV and the geographical distribution of its subgenotypes provide a tool to reconstruct the evolutionary history of HBV and may help to complement genetic data in the understanding of the evolution and past migrations of man.

Mutations on the FG surface loop of human papillomavirus type 16 major capsid protein affect recognition by both type-specific neutralizing antibodies and cross-reactive antibodies

The aim of this study was to further characterize the conformational neutralizing epitopes present on the surface-exposed FG loop of human papillomavirus (HPV) type 16 L1 major capsid protein. We have generated previously two chimeric L1 proteins by insertion of a foreign peptide encoding an epitope of the hepatitis B core (HBc) antigen within the FG loop. In addition, three other chimeric L1 proteins were obtained by replacing three different FG loop sequences by the HBc motif and three others by point mutations. All these chimeric L1 proteins retained the ability to self-assemble into virus-like particles (VLPs), with the exception of the mutant with substitution of the L1 sequence 274-279 by the HBc motif. The eight chimeric VLPs were then analyzed for differential reactivity with a set of six HPV-16 and HPV-31 monoclonal antibodies that bound to conformational and linear epitopes. The binding patterns of these monoclonal antibodies confirmed that the FG loop contained or contributed to neutralizing conformational epitopes. The results obtained suggested that the H31.F7 antibody, an anti-HPV-31 cross-reacting and neutralizing antibody, recognized a conformational epitope situated before the 266-271 sequence. In addition, H16.E70 neutralizing antibody reactivity was reduced with L1 VLPs with an Asn to Ala point mutation at position 270, suggesting that Asn is a part of the epitope recognized by this antibody. This study contributes to the understanding of the antigenic structure of HPV-16 and -31 L1 proteins by confirming that the FG loop contributes to neutralizing epitopes and suggesting the existence of both type-specific and cross-reactive conformational epitopes within the FG loop.

Positively charged synthetic peptides from structural proteins of papillomaviruses abrogate human papillomavirus infectivity

Human papillomavirus (HPV) virus-like particles (VLP) and synthetic peptides corresponding to positively-charged sequences of the major and minor capsid proteins were tested for their efficacy in inhibiting the infectivity of HPV 31 pseudovirions by blocking virus entry into cells. A greater than 80% reduction of transfection was observed with one HPV-31 peptide at a concentration of 10 microg/ml. Moreover, the blocking was not type-specific since similar reduction in transfection was observed with peptides from other HPV types at a concentration of 60 microg/ml. This concentration was non-toxic for the cells. These findings indicate that some of the positively-charged sequences of the L1 and L2 HPV capsid proteins of papillomavirus are compounds that might be locally active against sexually transmitted papillomavirus. The findings provide further evidence that cellular glycosamino-glycans (GAGs) are functional receptors for HPVs.

Human papillomaviruses and cancer in Uganda

In a case-control study in Uganda, we examined associations between different cancer sites or types in relation to antibodies against human papillomaviruses (HPV)-16, -18 and -45. For each cancer site or type, the control group comprised all other cancers excluding those known, or thought to be associated with HPV infection (cancers of the uterine cervix, penis and eye). Among controls the seroprevalence of antibodies was 11% (68/616) against HPV-16, 5% (29/605) against HPV-18 and 6% (35/605) against HPV-45. Antibodies against HPV-16 were significantly associated with only two cancers: uterine cervix [prevalence of antibodies 27% (51/191); odds ratio (OR) 2.0, 95% confidence interval (CI) 1.2-3.1, P=0.01] and penis [prevalence of antibodies 27% (4/15); OR 6.4, 95% CI 1.7-24.3, P=0.01]. For both cancers, the risk increased with increasing anti-HPV-16 antibody titre (Ptrend=0.01 for each). No cancer site or type was significantly associated with antibodies against HPV-18 and -45.

Serology for human papillomavirus

Difficulties with serology for papillomavirus are associated with the large number of human papillomavirus, cross-reactions between papillomavirus, and to the diversity of lesions and target sites for infection. In addition, the expression of the papillomavirus in the superficial layers of the epithelium gives rise to the weak presentation to immunocompetent cells of viral antigens, which in turn gives rise to a weak serological response. Distinct efforts have been made in previous decades to develop more specific and sensitive serological assays. These former studies use fusion proteins and synthetic peptides, although they remain on the whole uninteresting, due to their lack of sensitivity and specificity. Only in the last few years, and principally due to the advent of various virus-like particles (VLP), have more sensitive and specific assays become available. This paper is available too at: http://www.insp.mx/salud/index.html.

Insertion of a foreign sequence on capsid surface loops of human papillomavirus type 16 virus-like particles reduces their capacity to induce neutralizing antibodies and delineates a conformational neutralizing epitope

The aims of this study were to generate chimeric human papillomavirus (HPV)-16 L1 virus-like particles (VLPs) in order to identify immunogenic domains and conformational neutralizing epitopes, and to characterize the regions where a foreign epitope could be introduced. We hypothesized that these regions could be on L1 protein loops since they are exposed on the surface of VLPs. The aims of this study were achieved by mutating HPV-16 L1 proteins. Six amino acids encoding for the epitope 78-83 (DPASRE) of the hepatitis B core (HBc) antigen were introduced within the different loops of the L1 protein at positions 56/57, 140/141, 179/180, 266/267, 283/284 or 352/353. All these chimeric L1 proteins were capable of self-assembly into VLPs. The antigenicity and immunogenicity of some of these VLPs were reduced compared to the levels observed with wild-type VLPs. All were nevertheless able to induce neutralizing antibodies. VLPs with insertion at position 266/267 induced lower levels of neutralizing antibodies, suggesting the involvement of residues situated on FG loop in L1 neutralizing epitopes. All the chimeric L1 proteins except the one with insertion at position 56/57 were also able to induce anti-HBc antibodies, thus suggesting exposure of the HBc epitope on the VLP surface. Taken together, our findings indicate the possibility of designing HPV-derived vectors that are less immunogenic and suggest positions for insertion of defined immune epitopes or cell ligands into L1 protein to be exposed on the surface of VLPs.

Population-based human papillomavirus prevalence in Lampang and Songkla, Thailand

To investigate the prevalence and determinants of human papillomavirus (HPV) infection, the primary cause of cervical cancer, we studied 1741 women >/=15 years of age from Lampang and Songkla, Thailand. Exfoliated cervical cells were collected for Papanicolaou smear screening and DNA detection of 36 different HPV types. Serum immunoglobulin G antibodies against L1 virus-like particles (anti-VLPs) of HPV-16, -18, -31, -33, and -58 were evaluated using enzyme-linked immunosorbent assay. Overall, 110 women (6.3%) were HPV DNA positive; the most common types were HPV-16, -52, and -72. The age-standardized prevalence of HPV DNA was higher among the 1035 women from Lampang (9.1%; 95% confidence interval [CI], 7.1-11.1) than among the 706 women from Songkla (3.9%; 95% CI, 2.3%-5.6%). Anti-VLPs were found in 21.8% of all women and were more frequent among women from Lampang (29.2%) than among women from Songkla (10.9%). Major risk factors for cervical HPV DNA were age <35 years, HSV-2 seropositivity, and having a husband with extramarital sexual partners.

Human papillomavirus types 16, 31, and 58 use different endocytosis pathways to enter cells

The early steps of the intracellular trafficking of human papillomavirus type 16 (HPV-16), -31, and -58 pseudovirions were studied by investigating the effects of drugs acting at defined points of endocytosis pathways on virus-like particle-mediated pseudoinfection by overexpression of a dominant-negative form of the Eps15 protein to inhibit clathrin-mediated endocytosis and by electron microscopy. The results obtained suggested the involvement of clathrin-mediated endocytosis in HPV-16 and HPV-58 entry and caveola-mediated endocytosis in HPV-31 entry.

Prevalence of human papillomavirus infection in women in Busan, South Korea

To investigate the prevalence of and the risk factors for human papillomavirus (HPV) infection in South Korea, we interviewed and examined a randomly selected sample of 863 sexually active women (age range = 20-74 years, median 44) and 103 self-reported virgins from Busan. The presence of DNA of 34 different HPV types in cervical exfoliated cells was tested among sexually active women by means of a PCR-based assay. IgG antibodies against L1 virus-like particles (anti-VLPs) of HPV types 16, 18, 31, 33 and 58 were also evaluated by means of ELISA. The overall prevalence of HPV DNA was 10.4% (95% confidence interval, CI: 8.5-12.7%). The most often found HPV DNA types were HPV 70, HPV 16 and HPV 33; 19.8% (95% CI: 17.2-22.0) of sexually active women had antibodies against one or more HPV types. The most common anti-VLPs were against HPV 18, 31 and 16. Prevalences standardized by age on the basis of the world standard population were 13.0% for HPV DNA and 17.1% for anti-VLPs. The concordance between the 2 HPV markers at an individual level was modest, but the risk factors for detection of HPV DNA and anti-VLPs were similar: number of lifetime sexual partners (odds ratio, OR for >/= 4 vs. 1 = 3.5 and 5.4, respectively), seropositivity for herpes simplex virus-2 antibodies (OR = 2.6 and 2.5, respectively) and being single or divorced. HPV DNA, but not anti-VLPs, were elevated among women whose husbands were thought by their wives to have extra-marital affairs and those who had undergone vasectomy. Among 103 virgins, 4.9% had anti-VLPs (1/73 among those aged 24 years or less).

Positively charged sequences of human papillomavirus type 16 capsid proteins are sufficient to mediate gene transfer into target cells via the heparan sulfate receptor

Using synthetic peptides we have shown that positively charged sequences present at the C terminus of the L1 protein and the N and C termini of the L2 protein of human papillomavirus type 16 (HPV-16) bind to both DNA and heparan sulfate receptors. Moreover, these short amino acid sequences are sufficient to mediate gene transfer in COS-7 cells. The L1 proteins of other HPVs were shown to contain one or two DNA- and heparin-binding sequences that have the capacity to transfer genes. These DNA-binding sequences also recognized the enhancing packaging sequence of bovine papillomavirus type 1. The results suggest that the L2 protein could participate in DNA packaging during maturation of virions.

Cervical cancer control, priorities and new directions

Cervical cancer is caused by infection with a range of high risk "oncogenic" human papillomavirus (HPV) types, and it is now accepted that >99% of cervical cancer is initiated by HPV infection. The estimated lifetime risk of cervical cancer is nevertheless relatively low (less than 1 in 20 for most community based studies). Although sensitivity and specificity of the available diagnostic techniques are suboptimal, screening for persistent HPV infection is effective in reducing the incidence of cervical cancer. Infection can be detected by molecular techniques or by cytological examination of exfoliated cervical cells. Persistent infection is the single best predictor of risk of cervical cancer. The latest findings of HPV and cervical cancer research need to be widely disseminated to the scientific and medical societies that are updating screening and management protocols, public health professionals, and to women and clinicians. This report reviews current evidence, clinical implications and directions for further research in the prevention, control and management of cervical cancer. We report the conclusions of the Experts' Meeting at the EUROGIN 2003 conference.

The epidemiology of conjunctival squamous cell carcinoma in Uganda

As part of a larger investigation of cancer in Uganda, we conducted a case-control study of conjunctival squamous cell carcinoma in adults presenting at hospitals in Kampala. Participants were interviewed about social and lifestyle factors and had blood tested for antibodies to HIV, KSHV and HPV-16, -18 and -45. The odds of each factor among 60 people with conjunctival cancer was compared to that among 1214 controls with other cancer sites or types, using odds ratios, estimated with unconditional logistic regression. Conjunctival cancer was associated with HIV infection (OR 10.1, 95% confidence intervals [CI] 5.2-19.4; P<0.001), and was less common in those with a higher personal income (OR=0.4, 95% CI 0.3-0.7; P<0.001)[corrected]. The risk of conjunctival cancer increased with increasing time spent in cultivation and therefore in direct sunlight (chi2 trend=3.9, P=0.05), but decreased with decreasing age at leaving home (chi2 trend=3.9, P=0.05), perhaps reflecting less exposure to sunlight consequent to working in towns, although both results were of borderline statistical significance. To reduce confounding, sexual and reproductive variables were examined among HIV seropositive individuals only. Cases were more likely than controls to report that they had given or received gifts for sex (OR 3.5, 95% CI 1.2-10.4; P=0.03), but this may have been a chance finding as no other sexual or reproductive variable was associated with conjunctival cancer, including the number of self-reported lifetime sexual partners (P=0.4). The seroprevalence of antibodies against HPV-18 and -45 was too low to make reliable conclusions. The presence of anti-HPV-16 antibodies was not significantly associated with squamous cell carcinoma of the conjunctiva (OR 1.5, 95% CI 0.5-4.3; P=0.5) and nor were anti-KSHV antibodies (OR 0.9, 95% CI 0.4-2.1; P=0.8). The 10-fold increased risk of conjunctival cancer in HIV infected individuals is similar to results from other studies. The role of other oncogenic viral infections is unclear.