High prevalence of adeno-associated virus (AAV) type 2 rep DNA in cervical materials: AAV may be sexually transmitted

Harnessing the Natural Biology of Adeno-Associated Virus to Enhance the Efficacy of Cancer Gene Therapy

Adeno-associated virus (AAV) was first characterized as small “defective” contaminant particles in a simian adenovirus preparation in 1965. Since then, a recombinant platform of AAV (rAAV) has become one of the leading candidates for gene therapy applications resulting in two FDA-approved treatments for rare monogenic diseases and many more currently in various phases of the pharmaceutical development pipeline. Herein, we summarize rAAV approaches for the treatment of diverse types of cancers and highlight the natural anti-oncogenic effects of wild-type AAV (wtAAV), including interactions with the cellular host machinery, that are of relevance to enhance current treatment strategies for cancer.

Adeno-associated virus may play a protective role against human papillomavirus-induced cervical lesions independent of HIV serostatus

This study investigated the prevalence of adeno-associated virus (AAV) and human papillomavirus (HPV) DNA in cervical samples of HIV-seropositive and -seronegative women attending a clinic in south-eastern Brazil. Both viruses were investigated by polymerase chain reaction (PCR) and cytological exams were performed. AAV was typed by PCR and restriction fragment length polymorphism analysis. AAV prevalence was 19.7% (56/284), with 18.7% (21/112) and 20.3% (35/172) in HIV-positive and -negative women, respectively. AAV type 2 was the single virus type detected. AAV was detected with higher frequency in HPV-infected women ( P < 0.05) as was HPV in HIV-positive women ( P < 0.05). The AAV–HPV co-infected women showed a lower rate of atypical squamous cells of undetermined significance or cervical intraepithelial neoplasia development compared with those infected only with HPV. The prevalence of AAV2 confirms this type as the most common in human samples. This is the first report examining AAV in cervical samples of HIV-infected women and indicates that HIV infection does not appear to influence AAV prevalence or AAV–HPV co-infection.

Presence of DNA of adeno-associated virus in subfertile couples, but no association with fertility factors

BACKGROUND

Based on previous reports suggesting a role of adeno-associated virus (AAV) in miscarriage, the prevalence of AAV DNA in genital tracts of male and female partners of subfertile couples was determined to assess a potential association of AAV infection with clinically relevant parameters of male and female fertility.

METHODS

A prospective study was performed in the outpatient infertility clinic of a university-based hospital. Semen samples and endocervical material obtained from 146 male and 134 female partners of asymptomatic subfertile couples were analyzed for the presence of AAV DNA (using nested PCR). Patients' medical histories and details of clinical examinations were recorded. Semen quality, including sperm functional capacity and the presence of antisperm antibodies (ASA) and seminal white blood cells (WBC), was assessed in aliquots of the same ejaculate. Detailed examinations of the cervical factor and other variables of female subfertility were performed. Both partners were screened for bacterial infection.

RESULTS

The presence of AAV DNA in semen was not significantly related to semen quality, including sperm functional capacity or local ASA, nor was it coupled to the presence of AAV in the endocervical material of female partners. The presence of AAV DNA was not associated with the presence of other micro-organisms of the lower genital tract or with seminal WBC in men. AAV DNA in endocervical material was not related to a reduced quality of cervical mucus or to other female infertility factors.

CONCLUSIONS

The presence of AAV DNA in semen samples or endocervical swabs showed no significant association with clinically relevant infertility factors. However, longitudinal studies may clarify previous suggestions of an influence of AAV infection on early pregnancy problems.

Adeno-associated virus biology

Adeno-associated virus (AAV) was first discovered as a contaminant of adenovirus stocks in the 1960s. The development of recombinant AAV vectors (rAAV) was facilitated by early studies that generated infectious molecular clones, determined the sequence of the genome, and defined the genetic elements of the virus. The refinement of methods and protocols for the production and application of rAAV vectors has come from years of studies that explored the basic biology of this virus and its interaction with host cells. Interest in improving vector performance has in turn driven studies that have provided tremendous insights into the basic biology of the AAV lifecycle. In this chapter, we review the background on AAV biology and its exploitation for vectors and gene delivery.

Molecular detection of adeno-associated virus in cases of spontaneous and intentional human abortion

Pregnancy failure is a common event and often of unknown cause. Some viruses are thought to cause abortions including the adeno-associated viruses (AAV), viruses which are regarded as being without any definitive association to any human disease. This study investigated AAV infection in 81 human abortions, both spontaneous and intentional that occurred up to the 23rd week of gestation. Nucleic acid of AAV-2, 3, and 5 types from 118 decidual and chorionic tissues, collected from the patients in this study, was amplified by nested-PCR. In situ hybridization (ISH) was developed with a digoxigenin-labeled AAV probe in paraffin embedded tissues from the AAV positive cases. AAV was observed in 28.4% (23/81) of the cases, of which, 78.3% (18/23) were in the decidua and 21.7% (5/23) in the extravillous trophoblast, the chorionic plate, or chorionic villi fragments. AAV-2, the only type detected, occurred in 32.3% (22/68) and in 7.7% (1/13) of the spontaneous and intentional abortions, respectively. ISH revealed AAV in the decidua, chorionic tissue or chorionic plate and extravillous trophoblast. The detection of only AAV-2 type indicates that it is the most frequent in the population studied and/or shows tissue tropism. The presence of AAV in decidual or trophoblastic cells in cases of abortion, as observed by ISH, implies that the virus could jeopardize the pregnancy. The significant predominance in spontaneous cases suggests possibly a causal association between AAV and abortion.

Adeno-associated virus: a key to the human genome?

Adeno-associated viruses (AAV) are widely spread throughout the human population, yet no pathology has been associated with infection. This fact, together with the availability of simple molecular techniques to alter the packaged viral genome, has made AAV a serious contender in the search for an ideal gene therapy delivery vehicle. However, our understanding of the intriguing features of this virus is far from exhausted and it is likely that the mechanisms underlying the viral lifestyle will reveal possible novel strategies that can be employed in future clinical approaches. One such aspect is the unique approach AAV has evolved in order to establish latency. In the absence of a cellular milieu that will support productive viral replication, wild-type AAV can integrate its genome site specifically into a locus on human chromosome 19 (termed AAVS1), where it resides without apparent effects on the host cell until cellular conditions are changed by outside influences, such as adenovirus super-infection, which will lead to the rescue of the viral genome and productive replication. This article will introduce the biology of AAV, the unique viral strategy of targeted genome integration and address relevant questions within the context of attempts to establish therapeutic approaches that will utilize targeted gene addition to the human genome.

Adeno-associated virus type 2 induces apoptosis in human papillomavirus-infected cell lines but not in normal keratinocytes

The results of seroepidemiological studies suggest that infection with adeno-associated virus type 2 (AAV2) is negatively correlated with the incidence of human papillomavirus (HPV)-associated cervical cancer. We studied the potential of AAV2 oncosuppression of HPV and showed that HPV/AAV2 coinfection of cells culminated in apoptotic death, as determined by DNA laddering and caspase-3 cleavage. The induction of apoptosis coincided with AAV2 Rep protein expression; increased S-phase progression; upregulated pRb displaying both hyper- and hypophosphorylated forms; increased levels of p21(WAF1), p16(INK4), and p27(KIP1) proteins; and diminished levels of E7 oncoprotein. In contrast, normal keratinocytes that were infected with AAV2 or transfected with the cloned full-length AAV2 genome failed to express Rep proteins or undergo apoptosis. The failure of AAV2 to productively infect normal keratinocytes could be clinically advantageous. The delineation of the molecular mechanisms underlying the HPV/AAV2 interaction could be harnessed for developing novel AAV2-derived therapeutics for cervical cancer.

Cervical cancer isolate PT3, super-permissive for adeno-associated virus replication, over-expresses DNA polymerase delta, PCNA, RFC and RPA

BACKGROUND

Adeno-associated virus (AAV) type 2 is an important virus due to its use as a safe and effective human gene therapy vector and its negative association with certain malignancies. AAV, a dependo-parvovirus, autonomously replicates in stratified squamous epithelium. Such tissue occurs in the nasopharynx and anogenitals, from which AAV has been clinically isolated. Related autonomous parvoviruses also demonstrate cell tropism and preferentially replicate in oncogenically transformed cells. Combining these two attributes of parvovirus tropism, squamous and malignant, we assayed if AAV might replicate in squamous cervical carcinoma cell isolates.

RESULTS

Three primary isolates (PT1-3) and two established cervical cancer cell lines were compared to normal keratinocytes (NK) for their ability to replicate AAV. One isolate, PT3, allowed for high levels of AAV DNA replication and virion production compared to others. In research by others, four cellular components are known required for in vitro AAV DNA replication: replication protein A (RPA), replication factor C (RFC), proliferating cell nuclear antigen (PCNA), and DNA polymerase delta (POLD1). Thus, we examined PT3 cells for expression of these components by DNA microarray and real-time quantitative PCR. All four components were over-expressed in PT3 over two representative low-permissive cell isolates (NK and PT1). However, this super-permissiveness did not result in PT3 cell death by AAV infection.

CONCLUSION

These data, for the first time, provide evidence that these four cellular components are likely important for AAV in vivo DNA replication as well as in vitro. These data also suggest that PT3 will be a useful reagent for investigating the AAV-permissive transcriptome and AAV anti-cancer effect.

Induction of an antitumoral immune response by wild-type adeno-associated virus type 2 in an in vivo model of pancreatic carcinoma

We analyzed the immunologic impact of adeno-associated virus type 2 (AAV-2), a small single-stranded parvovirus with tumorsuppressive properties, on DSL6A pancreatic carcinoma in syngeneic rats. Established tumors of animals treated with AAV-2 or mock infected were resected (Ro), and DSL6A cells were rechallenged on the different site. Eleven (92%) of 12 mock-infected animals but only 3 (25%) of 12 AAV-2-treated animals redeveloped tumors. Adeno-associated virus type 2 infection provoked systemic raises in monocytes and neutrophils numbers and in levels of the proinflammatory monocyte chemoattractant protein 1 and interleukin 10. Adeno-associated virus type 2-treated tumors were infiltrated with monocytes, macrophages, natural killer cells, CD4+ T cells, and especially CD8+ T cells. In cytotoxicity assays, AAV-2-infected DSL6A tumor cells were recognized by lymphocytes from AAV-2-treated animals and from controls. Yet, uninfected DSL6A cells were exclusively killed by lymphocytes from AAV-2-treated animals. Additionally, those lymphocytes displayed high natural killer cell activity but failed to attack unrelated tumor targets. Taken together, these results suggest that the antiviral response toward AAV-2 cross-activates the immune system toward simultaneously present tumor disease. This and the known potential to significantly reduce toxic side effects of chemotherapy make nonpathogenic viruses such as AAV-2 as "1-agent combination therapy" to an interesting treatment option of residual tumor disease.

Detection of adeno-associated virus type 2 genome in cervical carcinoma

Adeno-associated virus (AAV) can impair the replication of other viruses. Adeno-associated virus seroprevalences have been reported to be lower among women with cervical cancer. In-vitro, AAV can interfere with the production of human papillomavirus virions. Adeno-associated virus-2 DNA has also been detected in cervical cancer tissue, although not consistently. To evaluate the role of AAV infection in relation to invasive cervical cancer, we performed a nested case–control study within a retrospectively followed population-based cohort. A total of 104 women who developed invasive cervical cancer on average 5.6 years of follow-up (range: 0.5 months–26.2 years) and 104 matched control-women who did not develop cervical cancer during the same follow-up time were tested for AAV and human papillomavirus by polymerase chain reaction. At baseline, two (2%) case-women and three (3%) control-women were positive for AAV-2 DNA. At the time of cancer diagnosis, 12 (12%) case-women and 3 (3%) matched control-women were positive for AAV-2 DNA. Persisting AAV infection was not evident. In conclusion, AAV-2 DNA was present in a low proportion of cervical cancers and we found no evidence that the presence of AAV in cervical smears of healthy women would be associated with reduced risk of cervical cancer.

Molecular characterization of adeno-associated viruses infecting children

Although adeno-associated virus (AAV) infection is common in humans, the biology of natural infection is poorly understood. Since it is likely that many primary AAV infections occur during childhood, we set out to characterize the frequency and complexity of circulating AAV isolates in fresh and archived frozen human pediatric tissues. Total cellular DNA was isolated from 175 tissue samples including freshly collected tonsils (n = 101) and archived frozen samples representing spleen (n = 21), lung (n = 16), muscle (n = 15), liver (n = 19), and heart (n = 3). Samples were screened for the presence of AAV and adenovirus sequences by PCR using degenerate primers. AAV DNA was detected in 7 of 101 (7%) tonsil samples and two of 74 other tissues (one spleen and one lung). Adenovirus sequences were identified in 19 of 101 tonsils (19%), but not in any other tissues. Complete capsid gene sequences were recovered from all nine AAV-positive tissues. Sequence analyses showed that eight of the capsid sequences were AAV2-like (approximately 98% amino acid identity), while the single spleen isolate was intermediate between serotypes 2 and 3. Comparison to the available AAV2 crystal structure revealed that the majority of the amino acid substitutions mapped to surface-exposed hypervariable domains. To further characterize the AAV capsid structure in these samples, we used a novel linear rolling-circle amplification method to amplify episomal AAV DNA and isolate infectious molecular clones from several human tissues. Serotype 2-like viruses were generated from these DNA clones and interestingly, failed to bind to a heparin sulfate column. Inspection of the capsid sequence from these two clones (and the other six AAV2-like isolates) revealed that they lacked arginine residues at positions 585 and 588 of the capsid protein, which are thought to be essential for interaction with the heparin sulfate proteoglycan coreceptor. These data provide a framework with which to explore wild-type AAV persistence in vivo and provide additional tools to further define the biodistribution and form of AAV in human tissues.

Generation of recombinant skin in vitro by adeno-associated virus type 2 vector transduction

It has long been recognized that skin may be a particularly good target for pharmacologic gene therapy and as a platform for the secretion of systemically distributed molecules. Adeno-associated virus type 2 (AAV) is a useful vector for skin gene therapy because skin is the natural host tissue for AAV, in which it functions as an autonomous parvovirus. We demonstrate here that recombinant (r) AAV vectors carrying the granulocyte-macrophage colony-stimulating factor (GM-CSF), human papillomavirus E6, or green fluorescent protein (GFP) transgene could transduce primary human keratinocytes in ex vivo culture. We further demonstrate that these transduced cells could be used to form a transgene-positive recombinant skin (r-skin), using the organotypic epithelial raft culture system. Transduction of keratinocytes was demonstrated by reverse transcriptase-polymerase chain reaction (RT-PCR) for RNA expression, enzyme-linked immunosorbent assay (ELISA) for product secretion, intracellular staining for protein expression, vector-chromosomal junction PCR and Southern blot analysis of proviral sequences, in situ immunohistochemistry analysis of protein expression, and ultraviolet light fluorescence for GFP expression. AAV/GM-CSF/Neo-infected keratinocyte/raft skins secreted GM-CSF at levels as high as 25 ng/cm(2) of skin and maintained expression to 60 days postinfection. These data support the utility and efficiency of AAV-based gene delivery to produce genetically altered keratinocytes and r-skin.

Human papillomavirus, cytomegalovirus, and adeno-associated virus infections in pregnant and nonpregnant women with cervical intraepithelial neoplasia

Two hundred eight cervical specimens from two groups of subjects, 165 nonpregnant women and 53 pregnant women with cervical intraepithelial neoplasia (CIN) of grades I to III, were positive by PCR analyses for human papillomaviruses (HPVs), adeno-associated virus type 2 (AAV 2), and human cytomegalovirus (HCMV) in 67, 6, and 4.1% of the cases, respectively. The presence of AAV 2 infection was more frequently associated with pregnancy (17 versus 2.4%) and HPV-positive cervices (odds ratio = 6.358) than HCMV was. Increased HPV infection was strongly associated (P < 0.001) with a higher CIN grade, but there is no evidence that AAV 2 and HCMV infections have any impact on CIN development.

Possible role of bacterial and viral infections in miscarriages

OBJECTIVE

To determine the role of infections in miscarriages. Chorionic villi from aborted material were subjected to cytogenetic evaluation and analyzed for the presence of Chlamydia trachomatis, Ureaplasma urealyticum, Mycoplasma hominis, human cytomegalovirus (HCMV), adeno-associated virus (AAV), and human papillomaviruses (HPV).

DESIGN

Retrospective study.

SETTING

University hospital and academic research institution.

MAIN OUTCOME MEASURE(S)

Karyotyping and detection of bacterial and viral DNA by means of polymerase chain reaction (PCR) in placenta specimens.

RESULT(S)

In 54 (50%) of 108 samples the karyotype was normal, in 38 (35%) samples it was abnormal, and in 16 (15%) samples karyotype was undetermined. No U. urealyticum, M. hominis, HCMV, or AAV-2 DNA was detected, while C. trachomatis DNA was detected in one (1%) and HPV DNA in eight (7%) samples. No significant correlation of HPV-positive findings with karyotype status was established.

CONCLUSION(S)

Our findings do not support a role of C. trachomatis, U. urealyticum, M. hominis, HCMV, or AAV infections in miscarriages during the first trimester of pregnancy. However, further investigation should be made to determine a possible involvement of HPVs in the development of genetic abnormalities of the fetus and in miscarriages.

Temporal acceleration of the human papillomavirus life cycle by adeno-associated virus (AAV) type 2 superinfection in natural host tissue

Epidemiologically, certain human papillomaviruses are positively associated with cervical cancer, while adeno-associated viruses (AAV-2) are negatively associated with this same cancer. Both HPV and AAV productively replicate in differentiating keratinocytes of the skin and interact with each other. However, AAV has a relatively fast life cycle, generating infectious progeny by the third to fourth day of an organotypic epithelial raft culture. In contrast, HPV is slow, generating infectious progeny only after 10-12 days. As earlier studies indicated that these two skin-tropic virus types significantly affect each other's life cycle, we investigated if the temporal kinetics of the slow HPV life cycle was affected by the fast AAV in raft cultures. Here it is shown that the presence of AAV-2 at a variety of multiplicities of infection (m.o.i.) resulted in early onset HPV-31b DNA replication. Using plasmids which each expressed only one of the four rep proteins, an enhancement affect was seen for all four rep proteins of AAV, with Rep40 having the highest activity. Furthermore, AAV (m.o.i. of 5) also resulted in a temporally accelerated production of HPV infectious units, seen as early as Day 4, with high levels of viral progeny being produced by Day 6.5. Like earlier studies at Day 12, histological differences were seen at Day 6.5 between AAV-infected and mock-infected HPV/rafts. These data suggest that under specific conditions the AAV rep trans-factors can positively regulate HPV gene expression in addition to the usual negative regulation that has been consistently observed by the rep proteins. These data also suggest that AAV has a significant effect upon the temporal kinetics of the HPV life cycle in natural host tissue. However, it is unclear if or how this AAV-induced fast HPV life cycle mechanistically correlates with lower rates of HPV-associated cervical disease.

Adeno-associated virus DNA in human gestational trophoblastic disease

Previous studies had shown a correlation between infection with the human adeno-associated virus (AAV) and spontaneous abortion in early pregnancy. Furthermore, AAV DNA had been detected in cells of the human trophoblast lines, Jeg-3, JAr, and BeWo, in cells of the human amnion line, FL, and in trophoblasts from amnion fluids. Infectious AAV virions could be isolated from amnion fluids. To further analyse AAV infection during pregnancy, we tested material from Gestational Trophoblastic Disease for the presence of AAV DNA. With 63 tissue samples from patients from Brazil, including 49 hydatiform moles and 14 choriocarcinomas, nested PCR was performed to detect the presence of AAV DNA. In addition, 15 samples from spontaneous abortions were analysed. AAV DNA was found in 43 samples (28/49 hydatiform moles, 4/14 choriocarcinomas, 11/15 miscarriage material). These findings confirm AAV infection of embryo-derived tissue in humans and further suggest a role of AAV in miscarriage and trophoblastic disease.

Adenoassociated virus type 2-induced inhibition of the human papillomavirus type 18 promoter in transgenic mice

The epithelium of the cervix uteri has been reported to be frequently coinfected with both human papillomaviruses (HPV) and helper virus-dependent adenoassociated viruses (AAV). Seroepidemiological data suggest that AAV infection could inhibit cervical cancer that is caused by specific ("high-risk") types of papillomaviruses. In vitro, infection with AAV type 2 (AAV-2) or transfection of AAV-2 early (rep) genes has been shown to inhibit transformation by papillomaviruses. To analyze the effects of AAV on HPV in vivo, we studied the influence of AAV-2 infection on the promoter activity of high-risk HPV type 18 (HPV-18) in mice, transgenic for sequences of the upstream regulatory region (URR) of HPV-18 controlling transcription of the reporter gene, lacZ. Transgenic animals (or tongue cells thereof, explanted and grown in culture) were treated with dexamethasone to induce the HPV-18 promoter. Simultaneously they were (i) infected with AAV, (ii) inoculated with AAV virus-like particles (VLPs; empty capsids), or (iii) mock infected. Inoculation with AAV-2 or VLPs inhibited activation of the HPV-18 promoter. In vitro, in baby hamster kidney cells transfected with the HPV-18-lacZ construct, tissue extracts from AAV-infected animals suppressed the HPV-18 URR to a similar extent as AAV infection did. Down-regulation of the HPV-18 promoter was less efficient with extracts from animals inoculated with VLPs and was not observed with extracts from uninfected or dexamethasone-treated animals. This indicates that AAV induces cellular factor(s) in vivo capable of mediating down-regulation of the HPV-18 promoter also in cells in vitro. In contrast, promoters of the low-risk HPV types (HPV-6, HPV-11) were not influenced by AAV infection as opposed to promoters of the high-risk types (HPV-18 and HPV-16).

DNA of adeno-associated virus (AAV) in testicular tissue and in abnormal semen samples

BACKGROUND

Human genital tissues, including spermatozoa, have been found to be frequently infected with the helper-virus dependent parvovirus, adeno-associated virus (AAV).

METHODS

To assess the role of AAV infection in disorders of the male reproductive system, semen samples from 95 men (including 73 men attending a fertility programme) and testicular samples from patients with azoospermia (n = 38) or prostate cancer (n = 8) were analysed using polymerase chain reaction for the presence of AAV DNA. Semen quality was assessed according to World Health Organization guidelines and the grade of atrophy of testicular biopsies was determined histomorphologically.

RESULTS

AAV DNA was detected in 38% (28/73) of ejaculates from men with abnormal semen analyses (oligoasthenozoospermia or asthenozoospermia) and in 4.6% of normal semen samples (1/22, P = 0.003). DNA from AAV helper-viruses (human papillomaviruses, cytomegalovirus) was detected at similar frequencies in normal and abnormal semen samples. In testes, AAV DNA was detected in 10 out of 38 biopsies from infertile men (26%), and in 2 out of 8 orchidectomy samples.

CONCLUSION

The data show an increased incidence of AAV infection with abnormal semen analysis. Detection of AAV DNA in the testes might point to a role for AAV infection in male infertility, possibly by interfering with spermatozoa development.

Altered biology of adeno-associated virus type 2 and human papillomavirus during dual infection of natural host tissue

Adeno-associated virus (AAV), a common genital virus, may have a "protective" role against human papillomavirus (HPV)-associated cervical cancer. Epidemiological studies indicate a negative correlation between AAV infection and the incidence of cervical cancer. In contrast, HPV is positively associated with cervical cancer. To investigate interactions between these two viruses we used the organotypic "raft" culture system. The raft culture system is capable of supporting the complete HPV life cycle. Raft tissues that were actively replicating HPV were superinfected with AAV type 2 (AAV-2). We observed a multiplicity of infection (m.o.i.)-dependent enhancement and inhibition of HPV DNA replication, concomitant with AAV-2 replication. The data suggest that at low m.o.i. of AAV-2 infection, HPV DNA replication was slightly increased compared to controls and AAV-2 replicated poorly. At high AAV-2 m.o.i., HPV DNA replication was reduced and AAV-2 replicated to high levels. AAV-2 replication was increased in the presence of HPV compared to primary human keratinocyte, squamous cell carcinoma, and HaCat raft cultures infected with AAV-2 alone. These data suggest that HPV may provide types of "enhancer/helper" functions for AAV-2 replication and progeny formation. Infection with AAV-2 had significant effects on epithelial morphology. During infection with low m.o.i. of AAV-2 the epithelium stratified to a greater extent than in controls. With high m.o.i. of AAV-2 infections, tissue cytopathic effects were observed, indicating an additional factor responsible for the effect of AAV-2 on HPV replication and infection. Our results demonstrate a complex interaction between AAV-2, HPV, and skin during dual infection.

Detection of adeno-associated virus DNA in female genital samples by PCR-ELISA

Adeno-associated viruses (AAV) are human parvoviruses that require helper function for their replication. Several studies have demonstrated that AAV DNA sequences can be found in the female genital tract but the incidence of infection seems very variable. A PCR-ELISA method detecting AAV DNA was developed for combining the specificity and the sensitivity of conventional PCR with an objective interpretation of the results. In the PCR-ELISA, a defined number of cells from cervical specimens were digested and amplified with concomitant digoxigenin labeling. Digoxigenin-labeled amplified products hybridized to a specific biotinylated probe were captured in streptavidin-coated microtiter wells by a biotin-streptavidin binding and were visualized by colorimetric immunoenzymatic reaction. PCR-ELISA was carried out in 110 cervical cytological specimens of women with or without the concomitant detectable presence of papillomavirus (HPV) DNA and the results were compared with those obtained by conventional PCR followed by dot blot hybridization. When compared to conventional PCR considered as reference standard, PCR-ELISA was found to be 98% sensitive and 96% specific. Out of the total 110 samples examined, 52.7% were positive for AAV DNA by both techniques, demonstrating a high prevalence of AAV infection in the uterine cervix. When analyzing samples with or without the presence of HPV DNA, 63.2 % of the samples were positive for HPV DNA and 41.5% of the samples were negative for HPV proved positive for AAV DNA by both PCR-ELISA and conventional PCR. Hence, PCR-ELISA, which can be completed in 1 day, proved to be a reliable method for an objective detection of AAV DNA in clinical samples. The present study showed a frequent infection of the cervical epithelium with AAV both in the presence and absence of HPV infection.

Detection of cervical infections in colposcopy clinic patients

The purpose of this study was to determine if Neisseria gonorrhoeae; Chlamydia trachomatis; herpes simplex virus; cytomegalovirus; Epstein-Barr virus; human herpesviruses 6, 7, and 8; or adeno-associated virus influenced the production of cervical intraepithelial neoplasia. Two hundred thirty-one cervical smear samples were tested for the presence of the organisms by PCR. In addition, human papillomavirus types in the samples were determined by PCR and classified into cancer risk types of high, moderate, and low. There was no link with cervical intraepithelial neoplasia status and detection of herpes simplex virus, cytomegalovirus, Epstein-Barr virus, human herpesviruses 6 and 8, gonorrhea, or chlamydia. However, high-grade cervical intraepithelial neoplasia was found more frequently with mixed infection by moderate-risk human papillomavirus types and human herpesvirus 7 than with these papillomavirus types alone. The presence of human herpesvirus 7 may increase the oncogenic potential of moderate-risk human papillomavirus types.

Adeno-associated virus is associated with a lower risk of high-grade cervical neoplasia

Adeno-associated virus (AAV) is a ubiquitous human helper-dependent parvovirus which may interact with human papillomaviruses (HPV) to modify a woman's risk of cervical neoplasia. This analysis was nested in a cohort study of low-income women receiving Pap smears as part of their family planning services. We selected cases (55 with high-grade cervical squamous intraepithelial lesions (HSIL) and 162 with low-grade LSIL) and controls (96 women with normal cervical cytology) and analyzed cervical DNA for AAV, using PCR amplification/dot blot hybridization, and HPV, using hybrid capture I. AAV positivity was associated with a significantly reduced risk of HSIL (age and HPV-adjusted odds ratio (aOR) = 0.32) yet not with LSIL (aOR = 0.78); 53.8% of HSIL, 66.9% of LSIL, and 70.7% of controls were AAV+. AAV appears to interact with HPV to reduce SIL risk; relative to the HPV-/AAV+ exposure, the respective aORs for HSIL and HPV+/AAV-, HPV+/AAV+, and HPV-/AAV+ were 17.0, 6.9, and 3.5. AAV+ was not associated with age, race, HPV status, or sexual or reproductive risk factors. These results strongly suggest that AAV may play a protective or inhibitory role in late stage cervical carcinogenesis. This conclusion needs to be verified in additional epidemiologic studies.

Evaluation of the possible protective role of adeno-associated virus type 2 infection in HPV-associated premalignant disease of the cervix

OBJECTIVE

Our objective was to examine the prevalence of adeno-associated virus (AAV) infection in women with normal cervical smears and those with HPV-associated cervical intraepithelial neoplasia (CIN).

METHODS

HPV typing was performed on DNA from cervical smears of 211 women with CIN (CIN 1 = 83, CIN 3 = 128) and 433 healthy women who had a normal cervical smear. HPV typing was performed on all cases and controls using type-specific oligonucleotide primers (HPV 16, 18, 31, 33). AAV DNA was amplified by nested PCR from the same samples. The amplified DNA were separated on 2% agarose gels, blotted, and hybridized to AAV-2 DNA labeled by random priming with [alpha-(32)P]dCTP to confirm specificity of amplification.

RESULTS

A total of 131 cases of CIN were positive for one of the HPV types either alone or in combination. HPV 16 was present in 120 (57%) cases, HPV 18 in 15 (7%), HPV 31 in 27 (13%), and HPV 33 in 15 (7%) and there were multiple HPV types detected in 34 (16%) cases. All of the controls were selected to be negative for HPV. A total of 6/433 (1.4%) control cervical smears and 4/211 (1.9%) of CIN (CIN1 = 2; CIN3 = 2) contained AAV DNA. No correlation between AAV and any clinical feature was observed.

CONCLUSIONS

These results are different from some that have been previously published and suggest that AAV DNA is not frequently present in either normal control cervical samples or cervical intraepithelial neoplasia. This does not support the hypothesis that AAV may be protective against cervical cancer. Further research is necessary to understand the natural history of AAV infection and its role in human disease.

Ubiquitous human adeno-associated virus type 2 autonomously replicates in differentiating keratinocytes of a normal skin model

Since its discovery in 1966, adeno-associated virus type 2 (AAV) has been described as a helper-dependent parvovirus. However, in this study we demonstrate that AAV undergoes its complete life cycle, devoid of helper viruses or genotoxic agents, in the organotypic epithelial raft tissue culture system, a model of normal skin. AAV progeny production directly correlated with epithelial differentiation, as nondifferentiating keratinocytes were defective for this activity. Large nuclear virus arrays of particles of approximately 26 nm (parvovirus size) were observed in the granular layers of the raft epithelium by electron microscopy. Additionally, dosage-dependent histologic changes, some of which might be interpreted as cytopathology, were induced in the AAV-infected epithelial tissues. These data suggest a new biological model for AAV; that is, AAV is an epithelial-tropic autonomous parvovirus that can alter normal squamous differentiation.

Productive replication of adeno-associated virus can occur in human papillomavirus type 16 (HPV-16) episome-containing keratinocytes and is augmented by the HPV-16 E2 protein

We used a sensitive assay to test whether an adeno-associated virus (AAV) productive replication cycle can occur in immortalized human keratinocytes carrying episomal human papillomavirus type 16 (HPV-16) DNA. Following transfection with cloned AAV DNA, infectious AAV was produced, and the infectivity was blocked by anti-AAV antiserum. The HPV-16 E2 protein substantially increased the yield of AAV. Other HPV early proteins did not, in our experiments, show this ability. E2 has been shown to be able to affect p53 levels and to block cell cycle progression at mitosis. We tested the effect of changes in p53 expression on AAV replication and found that large differences in the level of p53 did not alter AAV DNA replication. In extension of this, we found that cellular help for AAV in response to stress was also independent of p53. To test if a mitotic block could trigger AAV DNA replication, we treated the cells with the mitotic inhibitor nocodazole. AAV DNA replication was stimulated by the presence of nocodazole in these and a number of other cell types tested. Yields of infectious virus, however, were not increased by this treatment. We conclude that the HPV-16 E2 protein stimulates AAV multiplication in these cells and propose that this occurs independently of the effects of E2 on p53 and cell cycle progression. Since the effect of E2 was not seen in keratinocytes lacking the HPV-16 episome, we suggest that E2 can help AAV by working in concert with other HPV-16 proteins.

Update on the prevalence of serum antibodies (IgG and IgM) to adeno-associated virus (AAV)

In view of presumed non-pathogenicity, tumor suppressive properties, and site-specific integration of the viral genome the human parvovirus, adeno-associated virus (AAV) has gained great interest as a gene transduction vector. Data on the seroprevalence of antibodies to AAV vary between reports, probably due to the different serological methods used. In order to understand better the immune response to AAV during natural infection, sera from different age groups and various geographical regions were compared for AAV antibodies using an ELISA. The data show that the prevalence of antibodies to AAV is similar in Europe (Germany, France, and Switzerland), Brazil, and Japan, indicating worldwide infection. It was confirmed that infection takes place during childhood. However, declining seropositivity thereafter and a second increase of seropositivity after 30 years of age suggests reinfection or reactivation of latent virus in particular as the prevalence of IgM antibodies in adults is relatively high. Furthermore, pregnant women were found to be significantly more frequently seropositive than non-pregnant controls, hinting at a reactivation of persistent AAV (up to 80% of women carry AAV in genital tissue) in specific hormonal conditions, e.g., pregnancy. Cross-reaction of serum antibodies with the different AAV types (defined by complement fixation) was observed by ELISA and neutralization tests confirming earlier results. The results suggest an unstable AAV antibody response allowing lifelong reinfection or reactivation of persisting virus possibly due to partial immunotolerance after an infection in utero, at delivery or during early infancy.

Binding of the human papillomavirus type 16 p97 promoter by the adeno-associated virus Rep78 major regulatory protein correlates with inhibition

Human papillomavirus type 16 (HPV-16) infection is positively associated with cervical cancer, whereas adeno-associated virus (AAV) infection is negatively associated with this same cancer. In earlier studies these two virus types have been shown to directly interact, with AAV inhibiting or enhancing papillomavirus functions depending upon the specific circumstances. One defined interaction between these two viruses is the ability of the AAV Rep78 major regulatory protein to inhibit gene expression of the E6 promoter of BPV-1 (bovine papillomavirus type 1) and HPV types 16 and 18. As Rep78 is a DNA binding transcription factor, we considered whether Rep78 might bind HPV-16 DNA. Here, Rep78 is demonstrated to bind a 44-base pair region (nucleotides 14-56) within the HPV-16 p97 promoter using the electrophoretic mobility shift assay. This region is important for HPV-16 because it includes functional Sp1 and E2 protein binding motifs as well as part of the origin of replication. Furthermore, two Rep78 amino acid substitution mutants, at positions 77 or 64-65, were identified that did not recognize p97 DNA. Both of these Rep78 mutants were found to be defective for inhibition of p97 promoter activity in HeLa and T-47D nuclear extracts in vitro, in a transient chloramphenicol acetyltransferase assay, as well as defective for full inhibition of HPV-16-directed focus formation. These data, taken together, strongly suggest that the Rep78-p97 promoter interaction is at least partially responsible for Rep78-mediated inhibition of HPV-16. Finally, the finding that Rep78 specifically recognizes p97 DNA is surprising because the p97 promoter region contains no GAGC motifs, the core motif for Rep78 recognition. These data suggest that the p97 promoter may represent a new prototypical DNA target type for Rep78.

Evidence for infection of the human embryo with adeno-associated virus in pregnancy

Previous reports have demonstrated the presence of DNA of the human helper virus-dependent adeno-associated parvovirus (AAV) in uterine tissue and curettage material from early miscarriage. To examine infection of embryonic tissue during pregnancy, amnion fluids were analysed for the presence of AAV. Using polymerase chain reaction, AAV DNA was detected in 64 out of 238 DNA samples extracted from amnion cells. DNA of helper viruses were found in 12% (papillomavirus) and 18% (cytomegalovirus) of the samples (double infections with AAV in eight and nine cases, respectively). Furthermore, infectious AAV virions were found in 13 out of 43 AAV DNA-containing samples. In mothers with AAV DNA-positive amnion fluids, premature amniorrhexis and premature labour occurred significantly more frequently (P < 0.001). Using an immunofluorescence assay, 24% of newborn sera (unrelated to the amnion fluid samples) were found to contain IgM antibodies to AAV, in most cases paralleled by IgM antibodies in the mother's sera. The data demonstrate that AAV infection can occur in utero at early and at late stages of pregnancy. The observed complications at delivery should encourage studies to clarify possible pathological consequences of AAV infection in pregnancy and a possible latent infection of the fetus.

Adeno-associated virus and development of cervical neoplasia

Evidence from several sources has suggested that adeno-associated virus (AAV) infection might protect against cervical cancer, in part, by interfering with human papillomavirus (HPV)-induced tumorigenesis. Detection of AAV type 2 (AAV-2) DNA in cervical tissues has been reported. However, there have been few in vivo studies of women with cervical HPV infection or neoplasia, and these have reported inconsistent results. Therefore, we used polymerase chain reaction (PCR) assays targeted to the AAV-2 rep and cap genes to test tissue specimens from women in an epidemiological study of cervical neoplasia in Jamaica. We tested 105 women with low-grade cervical intraepithelial neoplasia (CIN-1), 92 women with CIN-3/carcinoma in situ or invasive cancer (CIN-3/CA), and 94 normal subjects. PCR amplification of human beta-globin DNA was found in almost all cervical specimens, indicating that these materials were adequate for PCR testing. The prevalence of HPV DNA, determined by HPV L1 consensus primer PCR was, as expected, strongly associated with presence and grade of neoplasia. Each of the AAV PCR assays detected as few as 10 copies of the virus genome. However, none of the 291 cervical specimens from Jamaican subjects tested positive for AAV DNA. Negative AAV PCR results were also obtained in tests of cervical samples from 79 university students in the United States. Exposure to AAV was assessed further by serology. Using a whole virus AAV-2 sandwich enzyme-linked immunosorbent assay, we found no relationship between AAV antibodies and presence or grade of neoplasia in either the Jamaican study subjects or women enrolled in a U.S. cervical cancer case (n = 74) -control (n = 77) study. Overall, the data provide no evidence that AAV infection plays a role in cervical tumorigenesis or that AAV commonly infects cervical epithelial cells.

Development of animal models for adeno-associated virus site-specific integration

The adeno-associated virus (AAV) is unique in its ability to target viral DNA integration to a defined region of human chromosome 19 (AAVS1). Since AAVS1 sequences are not conserved in a rodent's genome, no animal model is currently available to study AAV-mediated site-specific integration. We describe here the generation of transgenic rats and mice that carry the AAVS1 3.5-kb DNA fragment. To test the response of the transgenic animals to Rep-mediated targeting, primary cultures of mouse fibroblasts, rat hepatocytes, and fibroblasts were infected with wild-type wt AAV. PCR amplification of the inverted terminal repeat (ITR)-AAVS1 junction revealed that the AAV genome integrated into the AAVS1 site in fibroblasts and hepatocytes. Integration in rat fibroblasts was also observed upon transfection of a plasmid containing the rep gene under the control of the p5 and p19 promoters and a dicistronic cassette carrying the green fluorescent protein (GFP) and neomycin (neo) resistance gene between the ITRs of AAV. The localization of the GFP-Neo sequence in the AAVS1 region was determined by Southern blot and FISH analysis. Lastly, AAV genomic DNA integration into the AAVS1 site in vivo was assessed by virus injection into the quadriceps muscle of transgenic rats and mice. Rep-mediated targeting to the AAVS1 site was detected in several injected animals. These results indicate that the transgenic lines are proficient for Rep-mediated targeting. These animals should allow further characterization of the molecular aspects of site-specific integration and testing of the efficacy of targeted integration of AAV recombinant vectors designed for human gene therapy.

Recombinant adeno-associated virus-mediated expression of O6-alkylguanine-DNA-alkyltransferase protects human epithelial and hematopoietic cells against chloroethylating agent toxicity

Recombinant adeno-associated virus (rAAV) encoding the human O6-alkylguanine-DNA-alkyltransferase (hAT) protein and a selectable marker (Neo(r)) was used to transduce human cervical carcinoma (HeLa) cells and erythroleukemic (K562) cells and clones were selected using G418 (0.4 mg/ml). Thirteen HeLa clones were isolated, 9 of which survived for 2-3 months before cell death ensued, presumably owing to the loss of G418 resistance. Northern blot analysis of the remaining four clones, using a neo probe, showed high levels of RNA equivalent in size to the bicistronic RNA expected to be produced from this construct. Analysis of hAT activity showed that 2000-5000 fmol/mg protein was expressed relative to untransduced cells (800-900 fmol/mg protein). Cell survival analysis following exposure to the chloroethylating agent mitozolomide revealed that expression of hAT at levels two- to fourfold higher than background conferred significant resistance (p < 0.001) to the toxic effects of this drug. Two days following infection of K562 cells with the rAAV vector, immunoblot analysis showed that hAT protein was being produced. Three K562 clones, isolated using G418 selection, were studied in detail and were shown to express hAT activities of 1500, 1010, and 890 fmol/mg protein, respectively, at 40 days posttransduction (mock-transduced K562 cells contain <2 fmol of hAT/mg protein). As with HeLa cells, Northern blot analysis showed the production of an appropriately sized transcript and immunoblot analysis indicated that hAT protein was being produced. These clones were assayed for cell survival following exposure to mitozolomide. Expression of hAT at levels 800- to 1500-fold higher than background conferred significant resistance (p < 0.001) to the toxic effects of mitozolomide. We have therefore successfully conferred a protective advantage against mitozolomide toxicity to cells by rAAV-mediated hAT expression.

Detection of infectious adeno-associated virus particles in human cervical biopsies

Recently we reported that DNA of the human oncogenic papillomaviruses (HPV) and the tumor suppressive human helper virus-dependent parvoviruses, adeno-associated viruses type 2 (AAV-2), colocalize in cervical epithelium. To analyze whether infectious AAV particles are present in cervical tissue, we examined cervical biopsies from 36 patients with HPV-related lesions (squamous intraepithelial lesions) for the presence of AAV DNA and of infectious AAV. From each patient specimens from the lesion and from adjacent normal epithelium were analyzed. After PCR analysis AAV DNA-containing samples were purified by CsCl gradient centrifugation. The presence of AAV virions in CsCl gradients was analyzed and infectivity of AAV was determined. In addition, the biopsies were tested for the presence of HPV DNA. AAV DNA could be detected in biopsies from 23 of 36 patients. AAV particles were found in 11 AAV DNA-positive biopsies from 7 patients (lesions and/or normal tissue, respectively). AAV particles were found to be infectious virions in 10 of the 11 cases. These results demonstrate for the first time that infectious AAV can be isolated from human cervical biopsies, indicating a possible sexual transmission of AAV.

Discrimination between different types of human adeno-associated viruses in clinical samples by PCR

Persistent infection of human tissues with the helper virus-dependent parvovirus, adeno-associated virus (AAV) was detected by polymerase chain reaction (PCR) using primer pairs detecting AAV types 2, 3 or 5. In order to develop PCR protocols which discriminate between the different serotypes of AAV, the DNA of AAV-5 was sequenced partially and compared with the published sequences of AAV-2 and -3. Type specific oligonucleotides and specific probes which allow the distinction between human AAV types by PCR are described.

Adeno-associated virus Rep78 inhibits oncogenic transformation of primary human keratinocytes by a human papillomavirus type 16-ras chimeric

Seroepidemiologic studies demonstrate that adeno-associated virus (AAV) infection is negatively associated with cervical cancer. This inverse association may be due to an ability of AAV to inhibit the role of human papillomavirus (HPV) in cervical carcinogenesis. In support of this hypothesis AAV has been demonstrated to inhibit several papillomavirus types, including bovine papillomavirus type 1 and human papillomaviruses types 16 and 18 (HPV-16/18) in tissue culture. The AAV-encoded Rep78 protein was responsible for this inhibition. These previous studies, however, were largely carried out in immortalized mouse fibroblasts. This cell type is likely not to be the most accurate model cell type for studying HPV-associated cervical carcinogenesis. In this study it is demonstrated that AAV Rep78 protein inhibits oncogenic transformation of freshly explanted primary human foreskin keratinocytes by an HPV-16/ras chimeric genome. Such cells are the natural host cell type for HPV-16/18 infection. It is also demonstrated that the HPV-16 P97 promoter is specifically inhibited by Rep78 in a transient CAT assay. These data further extend our knowledge of the AAV-papillomavirus interaction and provide a model for investigating the negative association of AAV with cervical cancer.

The packaging capacity of adeno-associated virus (AAV) and the potential for wild-type-plus AAV gene therapy vectors

Because of its ability to integrate chromosomally and its non-pathogenic nature, adeno-associated virus (AAV) has significant potential as a human gene therapy vector. Here we investigate the maximum amount of DNA which can be inserted into the AAV genome and still allow efficient packaging into an infectious virus particle. Altered wild-type AAV genomes were constructed with inserts, which increased in size by 100 bp, ligated at map unit 96. These large wild-type-plus genomes were able to replicate and produce infectious virus, at levels slightly reduced but comparable to normal sized wild type, until the insert size reached 1 kb. These data indicate that the maximum effective packaging capacity of AAV is approximately 900 bp larger than wild type, or 119%. Furthermore, it is demonstrated that these large AAV genomes are able to latently infect cells by chromosomal integration as does wild-type AAV. These data suggest that therapy vectors carrying a foreign gene of 900 bp or less can be generated from AAV, by ligation into non-essential locations, and result in a recombinant AAV virus with a fully wild-type phenotype. Such wild-type-plus AAV vectors will have both advantages and disadvantages over defective recombinant AAV virus - the most important advantages being the ease in which high titers of infectious virus can be generated and the ability to specifically integrate within chromosome 19. Once the concern subsides over the presence of wild-type AAV in clinical applications, wild-type AAV vectors may find specific application niches for use in human gene therapy.

Human papillomavirus is more prevalent in first trimester spontaneously aborted products of conception compared to elective specimens

In this study the possible role of human papillomaviruses (HPV) in spontaneous abortions is addressed by assaying for HPV DNA in first trimester spontaneous and electively aborted products of conception materials enriched for chorionic villi. The presence of HPVs was measured by polymerase chain reaction (PCR) amplification and DNA dot blot hybridization using an internal probe. The "broad spectrum" HPV primers were directed to amplify E6/E7 junction sequences, while the probe was of an HPV-16 sequence with significant homology to HPV-6/11. The quantity and quality of isolated DNA was also analyzed and compared by observing the PCR amplification of a cellular sequence from the human beta-globin gene. Fifteen of the 25 spontaneous samples (60%) were found to be positive for HPV E6/E7 sequences. In comparison, only 3 of the 15 elective samples (20%) were positive. This is the first study of HPV in fetal materials to incorporate material from elective abortions as a control group. Although confounding contamination from the cervix and vagina can't be ruled out, these data are significant and strongly suggest that HPVs are elevated in spontaneously aborted products of conception. Furthermore, these results suggest the possibility that HPVs may be etiologic agents of at least some spontaneous abortions.