Antibodies against papillomavirus antigens in cervical secretions from condyloma patients

Natural and vaccine-induced B cell-derived systemic and mucosal humoral immunity to human papillomavirus

Introduction: Human papillomavirus (HPV) are the causative agent of mucosal neoplasia. Both cervical, anal and oropharyngeal cancers incidence is constantly increasing, making the HPV infection, a significant worldwide concern. Together, the CD8+ T cytotoxic cell-mediated response and the HPV-specific antibody response control most of the HPV infections before the development of cancers.Areas covered: We searched the MEDLINE and EMBASE databases and identified 228 eligible studies from 1987 to 2019 which examines both naturally acquired and vaccine induced humoral immunity against HPV infection in female and male subjects from worldwide origin. Herein, we synthesize current knowledge on the features of systemic and mucosal humoral immunity against HPV. We discuss the issues of the balance between the viral clearance or the escape to the host immune response, the differences between natural and vaccine-induced HPV-specific antibodies and their neutralizing capability. We also discuss the protection afforded after natural infection or following prophylactic vaccination.Expert opinion: Understanding the antibody response induced by HPV infection has led to the design of first-generation prophylactic vaccines. Now, prophylactic vaccination induces protective and long-lasting antibody response which would also strengthened the natural moderate humoral response in people previously exposed to the virus.

Infection and vaccine-induced HPV-specific antibodies in cervicovaginal secretions. A review of the literature

Background

Human papillomavirus (HPV) infects and propagates in the cervical mucosal epithelium. Hence, in addition to assessing systemic immunity, the accurate measurement of cervical immunity is important to evaluate local immune responses to HPV infection and vaccination. This review discusses studies that investigated the presence of infection and vaccine-induced HPV-specific antibodies in cervicovaginal secretions (CVS).

Methods

We searched the two main health sciences databases, PubMed and the ISI Web of Science, from the earliest dates available to March 2019. From the eligible publications, information was extracted regarding: (i) study design, (ii) the reported HPV-specific antibody concentrations in CVS (and the associated serum levels, when provided), (iii) the CVS collection method, and (iv) the immunoassays used.

Results

The systematic search and selection process yielded 44 articles. The evidence of HPV-specific antibodies in CVS after natural infection (26/44) and HPV vaccination (18/44) is discussed. Many studies indicate that HPV-specific antibody detection in CVS is variable but feasible with a variety of collection methods and immunoassays. Most CVS samples were collected by cervicovaginal washing or wicks, and antibody presence was mostly determined by VLP-based ELISAs. The moderate to strong correlation between vaccine-induced antibody levels in serum and in CVS indicates that HPV vaccines generate antibodies that transudate through the cervical mucosal epithelium.

Conclusion

Although HPV-specific antibodies have lower titres in CVS than in serum samples, studies have shown that their detection in CVS is feasible. Nevertheless, the high variability of published observations and the lack of a strictly uniform, well-validated method for the collection, isolation and quantification of antibodies indicates a need for specific methods to improve and standardize the detection of HPV-specific antibodies in CVS.

Age-specific prevalence of infection with human papillomavirus in females: a global review

PURPOSE

Global data on age-specific prevalence of human papillomavirus (HPV) infection overall, and for high-risk HPV types 16 and 18, are essential for the future implementation of HPV prophylactic vaccines for cervical cancer prevention.

METHODS

A systematic review of peer-reviewed publications was conducted to summarize worldwide data on genital HPV-DNA prevalence in women. Studies with clear descriptions of polymerase chain reaction or hybrid capture detection assays were included.

RESULTS

A total of 346,160 women were included in 375 studies. Of 134 studies with age-stratified HPV prevalence data (116 low sexual risk populations, 18 high sexual risk populations), over 50% were from Europe and the Middle East (38%) and North America (19%), with smaller proportions from Asia and Australia (21%), Central and South America (11%), and Africa (10%). Across all geographical regions, data on HPV prevalence were generally limited to women over 18 years of age. Consistently across studies, HPV infection prevalence decreased with increasing age from a peak prevalence in younger women (< or =25 years of age). In middle-aged women (35-50 years), maximum HPV prevalence differed across geographical regions: Africa (approximately 20%), Asia/Australia (approximately 15%), Central and South America (approximately 20%), North America (approximately 20%), Southern Europe/Middle East (approximately 15%), and Northern Europe (approximately 15%). Inconsistent trends in HPV prevalence by age were noted in older women, with a decrease or plateau of HPV prevalence in older ages in most studies, whereas others showed an increase of HPV prevalence in older ages. Similar trends of HPV 16 and/or 18 prevalence by age were noted among 12 populations with available data.

DISCUSSION

Genital HPV infection in women is predominantly acquired in adolescence, and peak prevalence in middle-aged women appears to differ across geographical regions. Worldwide variations in HPV prevalence across age appear to largely reflect differences in sexual behavior across geographical regions. Further studies of HPV prevalence in adolescents are needed for all geographic regions.

Serological study in Tunisian cervical cancer patients

OBJECTIVE

The aim of this study is to use a novel ELISA, based on five recombinant HPV-16 and HPV-18 proteins, for detection HPV-specific antibodies in a case-control study.

PATIENTS AND METHODS

L1, E6 and E7 genes have been over expressed in Escherichia coli as double fused proteins. These recombinant proteins were used in a GST-capture ELISA as coating antigens. Human sera were collected from women with cervical cancer. Negative human sera were collected from patients apparently healthy and may be affected by other infectious agents.

RESULTS

Most of the sera showed a positive reactivity to at least one of the HPV-16 or HPV-18 proteins (52/71). A percentage of 39.50% of the sera from HPV-16 infected women and 21.12% of the sera from women infected by HPV-18 genotype recognised at least one of the HPV-16 or HPV-18 proteins. Sera showed different reactivity to L1, E6 and E7 antigens, and only a few serum samples reacted to L1, E6 and E7 HPV-16, E6 and E7 HPV-18 (co-infection). Differences of reactivity between cases and controls were significant (P<0.0001).

CONCLUSION

This novel ELISA, based on recombinant HPV-16 and HPV-18 antigens, is able to detect antibodies in women infected by HPV genotypes. The assay is easy to perform and has low cost, making it suitable for monitoring the natural history of HPV infections as well as for detecting pre-existing HPV antibodies in women who receive vaccination.

Mecanismos de resposta imune às infecções

O conhecimento dos principais mecanismos de defesa imune contra os diversos agentes infecciosos permite a compreensão da patogênese das doenças infectoparasitárias e das várias estratégias do hospedeiro e do parasita. O sistema imunológico atua numa rede de cooperação, envolvendo a participação de muitos componentes estruturais, moleculares e celulares. Nesse cenário encontra-se o delicado equilíbrio entre a saúde e a doença, em que tanto a deficiência quanto o exagero resultam em dano tecidual. Este artigo explora esses aspectos e algumas abordagens terapêuticas que surgem desse entendimento.

Antibodies against human papillomavirus type 16 and 18 E6 and E7 proteins in cervicovaginal washings and serum of patients with cervical neoplasia

Serum antibodies against the E6 and E7 proteins of human papillomavirus (HPV) 16 and 18 are associated with cervical cancer. The aim of this study was to investigate the presence of local antibodies against HPV in cervicovaginal washings (CWs). In this study antibodies against the native HPV16 and HPV18 E6/E7 proteins were detectable in CWs (48%) and sera (29%) from patients with cervical cancer (n = 21) utilizing a sandwich protein enzyme-linked immunosorbent assay (ELISA). In paired CWs and sera from patients with cervical intraepithelial neoplasia (n = 38) and from healthy women (n = 22) no antibodies against these proteins were found. In 10 of 11 patients, the antibody response corresponded with the HPV type in the cervical smear and/or tumor tissue, which indicates the HPV type specificity of the assay. In 7 of 11 patients with antibody reactivity against HPV16 or HPV18 E6 and/or E7 proteins a higher level of antibody reactivity in the CWs than in the paired serum samples was found at similar inputs of total IgG. This suggests that the antibodies in the CWs against the investigated HPV proteins in these patients were locally produced.

Epidemiologic and mucosal immunologic aspects of HPV infection and HPV-related cervical neoplasia in the lower female genital tract: a review

Human papillomavirus (HPV) infections are known to play an important role in the pathogenesis of cervical neoplasia. Considering the morbidity and mortality of cervical cancer, infection with HPV can be regarded as a worldwide problem, especially in developing countries. Currently, many studies focus on the development of both prophylactic and therapeutic HPV vaccines. Crucial for these vaccination protocols to be successful is that they will result in a long-lasting ability to generate an immune response that will eliminate the virus. HPV transmission and subsequent infection is a local event in the lower female genital tract and therefore the efficacy of vaccines against this locally transmitted infection can be best assessed by parameters of local immunity. In this review we describe both the epidemiology of HPV-related cervical neoplasia and the general aspects of mucosal immunity in the female genital tract while focusing on the local humoral immunity in HPV-related cervical neoplasia.

IgG antibodies against human papillomavirus type 16 E7 proteins in cervicovaginal washing fluid from patients with cervical neoplasia

Little information is available about the cervicovaginal mucosal antibodies against human papillomavirus (HPV) proteins. In this study specific IgG antibodies against HPV 16 E7 protein were determined in paired samples of cervicovaginal washing fluid and serum from patients with cervical cancer (n = 22), cervical intraepithelial neoplasia (CIN) (n = 38), healthy individuals (n = 22), and serum from children (n = 41) by a radioactive immunoprecipitation assay (RIPA). HPV 16 E7 specific IgG antibodies were found in cervicovaginal washings (n = 8) and in sera (n = 8) of the patients with cervical cancer. About 60% of the patients with HPV 16 positive cervical cancer had HPV 16 E7 specific IgG antibodies. Titration studies showed that the IgG antibody reactivity in cervicovaginal washings was higher than in the paired serum samples of six patients with cervical cancer (P < 0.001). In the CIN group we found no IgG reactivity in the serum, but in five patients we found a low IgG reactivity in the cervicovaginal washings. No IgG reactivity was found in cervicovaginal washings and sera from healthy individuals and sera from children. HPV 16 E7 specific IgG antibodies seem to be locally produced in a number of patients with HPV 16 positive (pre)malignant cervical lesions. For more definitive evidence for the local production of these antibodies immunostaining should be performed to demonstrate the presence of specific anti-HPV 16 E7 IgG producing plasma cells in the cervical epithelium.

Immunomanipulative strategies for the control of human papillomavirus associated cervical disease

Three vaccine strategies that target human papillomavirus (HPV) are likely to be effective in the control of HPV-associated preneoplastic and neoplastic lesions of the uterine cervix. 1. Immunotherapy for HPV-associated cervical cancer targeted at two nonstructural PV proteins expressed in cancer cells (E6 and E7). 2. Vaccines against existing HPV infection and early premalignant lesions targeted at early viral proteins expressed in suprabasal stem cells of infected anogenital epithelium. 3. Prophylactic vaccines to prevent HPV infection involving immunization with genetically engineered virus-like particles to elicit neutralizing antibody. Strategies 1 and 2 will need to evoke cytotoxic T-cell (CTL) mediated responses.

Cervical mucus antibodies against human papillomavirus type 16, 18, and 33 capsids in relation to presence of viral DNA

To investigate whether cervical mucus antibodies against human papillomavirus (HPV) capsids are associated with the detection of HPV DNA or HPV-related cytological diagnoses, 611 samples of cervical secretions from 359 women referred to a colposcopy clinic were tested by an enzyme-linked immunosorbent assay for the presence of immunoglobulin A (IgA) antibodies against HPV capsids of HPV type 16, 18, or 33 and for the presence of cervical HPV DNA by PCR. Among subjects with at least one cervical sample positive for HPV type 16 (HPV-16) DNA, 28.1% also had at least one HPV-16 IgA-positive cervical sample (odds ratio [OR] = 2.9; P = 0.0003). IgA to HPV-18 was also more common among HPV-18 DNA-positive subjects (OR = 3.1; P = 0.0325) and IgA to HPV-33 was more common among HPV-33 DNA-positive subjects (OR = 4.2; P = 0.0023). Cervical IgA antibodies to HPV-16 were also more common among patients with cervical intraepithelial neoplasia, particularly among patients with cervical intraepithelial neoplasia grade I (P < 0.0005). The data indicate that an HPV type-restricted IgA antibody response against HPV capsids is detectable in cervical mucus and is associated with a concomitant cervical HPV infection.

Conization for cervical intraepithelial neoplasia is followed by disappearance of human papillomavirus deoxyribonucleic acid and a decline in serum and cervical mucus antibodies against human papillomavirus antigens

OBJECTIVE

Our purpose was to investigate whether conization for cervical intraepithelial neoplasia eliminates human papillomavirus deoxyribonucleic acid and effects the levels of serum and cervical mucus antibodies against human papillomavirus antigens.

STUDY DESIGN

Analysis of paired cervical brush and serum samples taken from 23 women with cervical intraepithelial neoplasia before and 16 to 27 months after conization was performed for presence of human papillomavirus deoxyribonucleic acid by polymerase chain reaction and for human papillomavirus antibodies by enzyme-linked immunosorbent assay.

RESULTS

Four women had recurrent cervical intraepithelial neoplasia, whereas 19 women were disease free. Eighteen of 23 women were positive for human papillomavirus deoxyribonucleic acid before treatment. At follow-up only the 4 women with recurrent cervical intraepithelial neoplasia were positive. Serum immunoglobulin G levels and A levels and immunoglobulin A levels in cervical mucus against most of the tested human papillomavirus antigens had declined at follow-up.

CONCLUSIONS

Human papillomavirus deoxyribonucleic acid was regularly eliminated and human papillomavirus antibody levels, especially local immunoglobulin A, declined after efficient treatment, suggesting that conization may be effective for treating the underlying human papillomavirus infection.

Analysis of human immunoglobulin-degrading cysteine proteinases of Trichomonas vaginalis

Trichomonas vaginalis is a protozoan parasite that causes a widely distributed sexually transmitted disease (STD). Since immunoglobulin G (IgG) antibodies to specific trichomonad immunogens are found in serum and vaginal washes (VWs) from patients with trichomoniasis, a potential mechanism of immune evasion by this parasite might be the ability of T. vaginalis proteinases to degrade human immunoglobulins (Igs). Incubation of human IgG with lysates of T. vaginalis organisms resulted in time- and concentration-dependent degradation of the heavy chain. Secretory IgA was degraded similarly. Inhibitors of cysteine proteinases, when added to trichomonal lysates, abolished IgG and IgA degradation, while EDTA, a metalloproteinase inhibitor, did not. Substrate-gel electrophoresis with human IgG, IgM, or IgA copolymerized with acrylamide revealed several distinct cysteine proteinases in both lysates and culture supernatants from logarithmically growing parasites that degraded all classes of human antibodies. Trichomonal lysates and supernatants of numerous isolates tested all had Ig-degrading activity. Finally, proteolytic activity against IgG was detected in most (26 of 33; 78%) VWs from patients with trichomoniasis. In contrast, 18 of 28 (65%) VWs from women without trichomoniasis or from patients infected with other STDs had no detectable proteinases when tested in an identical manner. The other 10 of these 28 VWs (35%) had smaller amounts of detectable Ig-degrading proteinases. These differences in Ig-degrading proteinase activity between patients with and without trichomoniasis, regardless of coinfecting STDs, were statistically significant (P = 0.001). These results illustrate that T. vaginalis is capable of degrading human Igs.

A vaccine conjugate of 'ISCAR' immunocarrier and peptide epitopes of the E7 cervical cancer-associated protein of human papillomavirus type 16 elicits specific Th1- and Th2-type responses in immunized mice in the absence of oil-based adjuvants

TraT protein, known as ISCAR (= Immunostimulatory Carrier), is one of a family of integral membrane proteins (Imps) of Escherichia coli representing powerful carrier molecules which when injected into experimental animals generate substantial antibody and T proliferative responses to molecules conjugated to it. We extend these findings to show that ISCAR functions to stimulate Th1- and Th2-type responses, including specific cytotoxic T cells and tumour protection. We report here that by conjugating to ISCAR a 19mer peptide containing linear B epitopes, a T helper (Th) epitope, and a H-2b-restricted T cytotoxic (CTL) epitope of E7 protein of human papillomavirus type 16 (HPV16), and immunizing C57B1/6 (H-2b) mice, we elicited (i) specific IgG2a and IgG1 antibodies; (ii) IL-2 and IL-4 production by specifically recalled lymph node cells in vitro; (iii) cytotoxic T lymphocytes which specifically killed both E7 peptide-pulsed, and whole E7 gene-transfected tumour target cells; and (iv) in vivo protection against an E7 gene-transfected tumour cell inoculum. These findings have implications for the design of vaccines to stimulate immune responses to endogenously processed target antigens (e.g. tumour-associated antigens) without the unwanted side effects of oil-based adjuvants. In addition they support the case for a E7-targeted therapeutic vaccine for HPV-associated human cervical cancer.

A two-site enzyme immunoassay for quantitation of human papillomavirus type 16 particles

A group of human papillomaviruses (HPV), in particular HPV type 16, are the major cause of anogenital dysplasias, which are precursors of anogenital cancer. The mode of transmission, extent of infectivity and natural history of infection are incompletely understood because methods to quantify shedding of viral particles have not been available. A two-site ELISA was developed to detect and quantify HPV-16 particles. Rabbits and guinea pigs were immunized with a series of peptides from the L1 and L2 capsid proteins of HPV-16. Among rabbit antipeptide sera tested for use as capture antibodies, only sera against one peptide bound detectable amounts of virus. Guinea pig antisera against several peptides were used as reporter antibodies to detect bound virus particles. If antisera against the same peptide were used both as capture antibody and reporter antibody, only intact particles were detected. Disrupted particles were quantified using antibodies against one L1 peptide as capture antibody and antibodies against other L1 peptides as reporter antibody. The lowest detectable amount of virus was 3 ng (0.06 micrograms/ml). There was no detectable cross-reaction with HPV type 6 or 11. The assay could be used both with cervical swabs in several common sample collection buffers and with surgical material solubilized in NP40-containing extraction buffers. Among 15 surgically removed condyloma acuminata, only 1 specimen was found to contain HPV-16 particles, at a concentration of 375 ng/ml (1.1 micrograms/specimen). Among 29 cervical swab samples from patients with koilocytotic atypia, 9 samples were found to contain virus. The results indicate that this assay is useful for large-scale studies on shedding of HPV particles.

Seric and local antibodies against a synthetic peptide of HPV16

An ELISA method was used to detect IgG and IgA directed against a synthetic peptide derived from the E2 ORF of the human papillomavirus (HPV) 16 in sera and in cervico-vaginal secretions from 20 women without evidence of HPV infection and from 41 women with histological diagnosis of HPV infection. The proportion of IgA positive sera (63.4% in the case-group vs. 20.0% in the control-group) and secretions (48.8% in the case-group vs. 15.0% in the control-group) was significantly higher in women with HPV infection and seemed to increase with the severity of the cervical lesion. Such a difference was not found for specific IgG. Comparing, for each patient, the antibody level in the serum and in the secretions, we found that the amount of IgA was at mean 2.4 times higher in the sera than in the secretions.

Immunization of mice with HPV vaccinia virus recombinants generates serum IgG, IgM, and mucosal IgA antibodies

To assess the utility of vaccinia virus recombinants in the development of an immune response against HPV capsid antigens, 5-week-old C57B16 female mice were administered either purified HPV 1 capsids produced by a vaccinia virus recombinant or the recombinant vaccinia virus itself. Animals were boosted at Week 4 with either agent. Mice developed a serum IgG antibody response in all the administration protocols that was directed mainly against native L1 epitopes. Mice injected initially with the vaccinia virus recombinant and boosted with purified capsids had a higher titer antibody response (P = 0.024) with more mice responding to a greater extent. All mice produced a serum IgM response that preceded the IgG response by approximately 2 weeks and lasted 1-3 weeks. The IgM response was directed against native L1 epitopes. Although no serum IgA was detected, IgA could be detected in vaginal secretions of mice that were immunized or boosted with the vaccinia virus vector. These results indicate that an extensive humoral immune response to HPV can be elicited using vaccinia virus recombinants.

Human papillomavirus DNA and anti-HPV secretory IgA antibodies in cytologically normal cervical specimens

Cervical specimens collected from 163 cytologically healthy women were screened for the presence of human papillomavirus (HPV) DNA and anti-HPV secretory IgA antibodies. HPV DNA was detected by a general primer mediated polymerase chain reaction (PCR), which amplifies a conserved region from the L1 ORF of genital HPVs. The PCR products were typed by restriction enzyme digestion. A total of 35 samples (21.5%) were positive for HPV DNA (13 samples for HPV 6, 6 for HPV 16, 3 for HPV 18, and 13 for untypeable HPV X). HPV DNA positivity was significantly higher among women under 25 years of age (34.8%) than among the older patients (12.4%) (P < 0.001). An enzyme-linked immunosorbent assay (ELISA) using synthetic peptide antigens was carried out to detect local secretory IgA antibodies against the following HPV specific antigens: HPV 16 E2, HPV 16 E7, HPV 16 L1, HPV 16 L2, and HPV 11 L2. Thirty-four secretions (20.9%) were found to react with at least one of the oligopeptides. Anti-HPV IgA positivity was the highest among women aged 25-32 years, and it was significantly lower in both the younger and the older age groups (P < 0.05). Correlation between HPV DNA and anti-HPV IgA detection was rather weak: anti-peptide IgA positivity was 34.3% (12 of 35) among HPV DNA positive patients compared to 17.2% (22 of 128) among HPV DNA negative women (P < 0.05). The fluctuating course of latent HPV infections should be considered in evaluating the low level of correlation between HPV DNA and anti-HPV IgA positivity.

Evaluation of serum antibody response to a newly identified B-cell epitope in the minor nucleocapsid protein L2 of human papillomavirus type 16

The aim of this work was to identify B-cell epitopes in the minor nucleocapsid (L2) protein of human papillomavirus (HPV) type 16 and characterization of allied antibody response. Serum samples of 513 individuals (323 women with various degrees of cervical atypia, 150 men and 40 small children) were available for the study. Synthetic peptides overlapping the L2 protein of HPV 16 twice were applied in ELISA for epitope scanning and antibody determination. An HPV 16 L2 derived dodecamer SGYIPANTTIPF (amino acids 391-402) proved to be the major B-cell epitope. Both IgA antipeptide antibody positivity (range 7-28%) and mean IgA antibody levels (range 13.2 EIU to 42.4 EIU, P < 0.05) increased with the degree of cervical atypia, whereas antipeptide IgG antibodies showed an opposite trend. During a 2-years follow-up significantly (P < 0.0005) decreasing IgA antibody levels to the SGYIPANTTIPF peptide were associated with regression of koilocytotic atypia. Analysis of anti-peptide IgA antibodies of 118 women with known HPV type revealed that a majority of positives had HPV 16/18 DNA. It was concluded that antibody response to the newly discovered peptide was partially type- and disease-specific. Our results also suggest an impairment of the IgG but not IgA class antibody response to HPV 16 in patients with persistent cervical HPV infection.