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

Potential role of viral infections in miscarriage and insights into the underlying molecular mechanisms

Intrauterine viruses can infect the decidua and placenta and cause adverse effects on the fetus during gestation. This review discusses the contribution of various viral infections to miscarriage and the molecular mechanisms by which viruses can cause devastating effects on healthy fetuses and induce miscarriage. Severe acute respiratory syndrome coronavirus 2 as newly emerged coronavirus was considered here, due to the concerns about its role during pregnancy and inducing miscarriage, as well. In this narrative review, an extensive literature search was conducted to find all studies investigating viral infections in miscarriage and their molecular mechanisms published over the past 20 years. The results of various studies investigating the roles of 20 viral infections in miscarriage are presented. Then, the mechanisms of pregnancy loss in viral infections were addressed, including alteration of trophoblast invasion and placental dysfunction, inducing excessive maternal immune response, and inducing apoptosis in the placental tissue. Viruses may cause pregnancy loss through different mechanisms and our knowledge about these mechanisms can be helpful for controlling or preventing viral infections and achieving a successful pregnancy.

Evaluation of the Humoral Response to Adeno-Associated Virus-Based Gene Therapy Modalities Using Total Antibody Assays

The number of viral vector-based gene therapies (GTx) continues to grow with two products (Zolgensma® and Luxturna®) approved in the USA as of March 2021. To date, the most commonly used vectors are adeno-associated virus-based (AAV). The pre-existing humoral immunity against AAV (anti-AAV antibodies) has been well described and is expected as a consequence of prior AAV exposure. Anti-AAV antibodies may present an immune barrier to successful AAV transduction and hence negatively impact clinical efficacy and may also result in adverse events (AEs) due to the formation of large immune complexes. Patients may be screened for the presence of anti-AAV antibodies, including neutralizing (NAb) and total binding antibodies (TAb) prior to treatment with the GTx. Recommendations for the development and validation of anti-AAV NAb detection methods have been presented elsewhere. This manuscript covers considerations related to anti-AAV TAb-detecting protocols, including the advantages of the use of TAb methods, selection of assay controls and reagents, and parameters critical to monitoring assay performance. This manuscript was authored by a group of scientists involved in GTx development representing eleven organizations. It is our intent to provide recommendations and guidance to industry sponsors, academic laboratories, and regulatory agencies working on AAV-based GTx viral vector modalities with the goal of achieving a more consistent approach to anti-AAV TAb assessment.

Ultrasensitive nucleic acid detection based on phosphorothioated hairpin-assisted isothermal amplification

Herein, we describe a phosphorothioated hairpin-assisted isothermal amplification (PHAmp) method for detection of a target nucleic acid. The hairpin probe (HP) is designed to contain a 5' phosphorothioate (PS)-modified overhang, a target recognition site, and a 3' self-priming (SP) region. Upon binding to the target nucleic acid, the HP opens and the SP region is rearranged to serve as a primer. The subsequent process of strand displacement DNA synthesis recycles the bound target to open another HP and produces an extended HP (EP) with a PS-DNA/DNA duplex at the end, which would be readily denatured due to its reduced thermal stability. The trigger then binds to the denatured 3' end of the EP and is extended, producing an intermediate double-stranded (ds) DNA product (IP). The trigger also binds to the denatured 3' end of the IP, and its extension produces the final dsDNA product along with concomitant displacement and recycling of EP. By monitoring the dsDNA products, the target nucleic acid can be identified down to 0.29 fM with a wide dynamic range from 1 nM to 1 fM yielding an excellent specificity to discriminate even a single base-mismatched target. The unique design principle could provide new insights into the development of novel isothermal amplification methods for nucleic acid detection.

Baculovirus-Derived Vectors for Immunization and Therapeutic Applications

Baculoviruses are arthropod-specific, enveloped viruses with circular, supercoiled double-stranded deoxyribonucleic acid genomes. While many viruses are studied to seek solutions for their adverse impact on human, veterinary, and plant health, the study of baculoviruses was stimulated initially by their potential utility to control insect pests. Later, the utility of baculovirus as gene expression vectors was evidenced leading to numerous applications. Several strategies are employed to obtain recombinant viruses that express large quantities of heterologous proteins. A major step forward was the development of bacmid technology (the construction of bacterial artificial chromosomes containing the genome of the baculovirus) which allows the manipulation of the baculovirus genome in bacteria. With this technology, foreign genes can be introduced into the bacmid by homologous and site-directed recombination or by transposition. Baculoviruses have been used to explore fundamental questions in molecular biology such as the nature of programmed cell-death. Moreover, the ability of baculoviruses to transduce mammalian cells led to the consideration of their use as gene-therapy and vaccine vectors. Strategies for genetic engineering of baculoviruses have been developed to meet the requirements of new application areas. Display of foreign proteins on the surface of virions or in nucleocapsid structures, the assembly of expressed proteins to form virus-like particles or protein complexes have been explored and validated as vaccines. The aim of this chapter is to update the areas of application of the baculoviruses in protein expression, alternative vaccine designs and gene therapy of infectious diseases and genetic disorders. Finally, we review the baculovirus-derived products on the market and in the pipeline for biomedical and veterinary use.

Molecular Detection of Adeno-Associated Virus DNA in Cases of Spontaneous and Therapeutic Abortion

BACKGROUND

Adeno-associated viruses (AAVs) have been found in human blood cells, cervical biopsies, and epithelial cell brushings, endometrium, and abortion material, which suggest their possible roles in the induction of miscarriage.

OBJECTIVE

In this case control study, the presence of AAV DNA in placental tissue of spontaneous and therapeutic abortions was compared.

METHOD

Placenta samples were evaluated for AAV DNA by hemi-nested PCR in miscarriages occurring in the first 24 weeks of pregnancy from therapeutic and spontaneous abortions.

RESULTS

Eighty-one therapeutic abortions (control group) and 83 spontaneous abortions (case group) were evaluated. Sixty-two (38.2%) of 164 abortions were AAV positive, including 35 (21.6%) spontaneous abortions and 27 (16.6%) therapeutic abortions.

CONCLUSION

There was no statistically significant difference between the presence of the AAV genome in spontaneous and therapeutic abortions. This observation was consistent with other studies in this area.

Viral vectors as vaccine carriers

This chapter reviews the performance of viral vectors based on adenoviruses or adeno-associated virus as vaccine carriers for infectious diseases. Replication-defective adenovirus vectors based on multiple human or non-human serotypes have consistently induced potent transgene product-specific B and T cell responses and are increasingly being explored in human clinical trials. The immunogenicity of most vectors based on adeno-associated virus vectors has been poor with the exception of a recently described hybrid vector from rhesus macaques that due to its ability to induce potent responses in mice warrant further investigation.

Emergence of infectious malignant thrombocytopenia in Japanese macaques (Macaca fuscata) by SRV-4 after transmission to a novel host

We discovered a lethal hemorrhagic syndrome arising from severe thrombocytopenia in Japanese macaques kept at the Primate Research Institute, Kyoto University. Extensive investigation identified that simian retrovirus type 4 (SRV-4) was the causative agent of the disease. SRV-4 had previously been isolated only from cynomolgus macaques in which it is usually asymptomatic. We consider that the SRV-4 crossed the so-called species barrier between cynomolgus and Japanese macaques, leading to extremely severe acute symptoms in the latter. Infectious agents that cross the species barrier occasionally amplify in virulence, which is not observed in the original hosts. In such cases, the new hosts are usually distantly related to the original hosts. However, Japanese macaques are closely related to cynomolgus macaques, and can even hybridize when given the opportunity. This lethal outbreak of a novel pathogen in Japanese macaques highlights the need to modify our expectations about virulence with regards crossing species barriers.

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.

Latest developments in the large-scale production of adeno-associated virus vectors in insect cells toward the treatment of neuromuscular diseases

Adeno-associated viral (AAV) vectors are gene vectors of choice for the development of gene therapy treatments for many rare diseases affecting various tissues including retina, central nervous system, liver, and muscle. The AAV based gene therapy approach became conceivable only after the development of easily scalable production systems including the Sf9 cell/baculovirus expression system. Since the establishment of the production of AAV in the Sf9/baculovirus system by the group of Rob Kotin, this new production system has largely been developed for optimizing the large scale production of different serotypes of AAV for preclinical and clinical purposes. Today this manufacturing system allows for the production of purified vector genome (vg) quantities of up to 2 × 10(15) for AAV1 using a 50L reactor and the scale up to larger reactor volumes is paralleled by a corresponding increase in the vector yield. This review presents the principles and achievements of the Sf9/baculovirus system for the production of AAV in comparison to other expression systems based on mammalian cells. In addition, new developments and improvements, which have not yet been implemented at a large scale, and perspectives for further optimization of this production system will be discussed. All of these achievements as well as further process intensifications are urgently needed for the production of clinical doses for the treatment of neuromuscular diseases for which estimated doses of up to 10(14)vg/kg body mass are required.

Detection of adeno-associated virus viremia in hematopoietic cell transplant recipients

Adeno-associated virus (AAV) is widely considered to be nonpathogenic, but the clinical epidemiology of this virus is limited. By use of polymerase chain reaction assays, we investigated the incidence and clinical significance of AAV viremia in a population of consecutive recipients of a hematopoietic cell transplant (HCT). Four (2.8%) of 145 patients developed AAV viremia after HCT. Viremia was low level and transient in all patients. Two patients were admitted to the hospital and died in proximity to AAV viremia (<7 weeks between diagnosis and death); however, AAV was not detected in tissue specimens obtained at autopsy. Thus, AAV does not appear to play a pathogenic role in organ-specific illness, even in a highly immunocompromised population.

Adeno-associated viruses

Adeno-associated virus (AAV) vectors have evolved over the past decade as a particularly useful gene -vector for in vivo applications. In contrast to oncoretro- and lentiviral vectors, this vector stays essentially episomal after gene transfer, making it safer because of the absence of insertional mutagenesis. AAV's non-pathogenicity is a further advantage. For decades, this vector could only be produced at a small scale for research purposes and, eventually, used at very small doses for clinical studies, because only transfection methods were available, which have limited scalability. However, since the development of scalable production methods, this bottleneck is resolved and, from a technical point of view, large quantities of AAV vectors can be produced, opening the possibility of using AAV vectors for whole body treatments in gene therapy trials. This chapter presents the basic principles of small- and large-scale production procedures as well as detailed procedure of small-scale production, purification, and analytical protocols for AAV vectors. In Chapter 10, the reader will find a large-scale production method based on the use of the insect cell/baculovirus system.

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.

Prevalence of serum IgG and neutralizing factors against adeno-associated virus (AAV) types 1, 2, 5, 6, 8, and 9 in the healthy population: implications for gene therapy using AAV vectors

Adeno-associated viruses (AAVs) are small, nonenveloped single-stranded DNA viruses that require helper viruses to facilitate efficient replication. Despite the presence of humoral responses to the wild-type AAV in humans, AAV remains one of the most promising candidates for therapeutic gene transfer to treat many genetic and acquired diseases. Characterization of the IgG subclass responses to AAV and study of the prevalence of both IgG and neutralizing factors to AAV types 1, 2, 5, 6, 8, and 9 in the human population are of importance for the development of new strategies to overcome these immune responses. Natural exposure to AAV types 1, 2, 5, 6, 8, and 9 can result in the production of antibodies from all four IgG subclasses, with a predominant IgG1 response and low IgG2, IgG3, and IgG4 responses. Prevalences of anti-AAV1 and -AAV2 total IgG determined by enzyme-linked immunosorbent assay were higher (67 and 72%) than those of anti-AAV5 (40%), anti-AAV6 (46%), anti-AAV8 (38%), and anti-AAV9 (47%). Furthermore, data showed that cross-reactions are important. The two highest neutralizing factor seroprevalences were observed for AAV2 (59%) and AAV1 (50.5%) and the lowest were observed for AAV8 (19%) and AAV5 (3.2%). Vectors based on AAV5, AAV8, and AAV9 may have an advantage for gene therapy in humans. Furthermore, among individuals seropositive for AAV5, AAV8, and AAV9, about 70-100% present low titers. Better characterization of the preexisting humoral responses to the AAV capsid and cross-reactivity will allow development of new strategies to circumvent AAV acquired immune responses.

Persistent adeno-associated virus 2 and parvovirus B19 sequences in post-mortem human cerebellum

We previously reported in a large cohort (N = 104) of post-mortem tissues the detection of both the non-pathogenic adeno-associated virus (AAV2) in approximately 13% and the pathogenic human parvovirus B19 (B19) in approximately 42% of human brains, particularly the dorsolateral prefrontal cortex. Multiple animal parvoviruses target the developing cerebellum (CBLM) resulting in hypoplasia and ataxia, but very little is known about the human parvoviruses and their ability to infect or cause disease in the CBLM. We have now confirmed in the above cohort the presence of AAV2 and B19 sequences in the CBLM. Our results show that approximately 27% and approximately 70% of human CBLM are positive by nested polymerase chain reaction for AAV2 and B19 sequences, respectively. We also document in a second cohort (N = 10) the presence of AAV2 (50%) and B19 (100%) sequences in the CBLM and correlate our results for B19 with studies from matched sera. Eighty percent (80%) of this cohort was positive for anti-B19 IgG, while none were IgM+, suggesting that most individuals had been previously infected with B19 but none acutely. To our knowledge, this study is the first to demonstrate that both AAV2 and B19 sequences are present at relatively high frequencies in the CBLM and are likely due to persistent rather than acute infection. Further studies will lead to insights into AAV2- and/or B19-CBLM interactions including mechanisms of infection, persistence, and possibly neuropathology, including cerebellar hypoplasia and ataxia.

Viruses and other infections in stillbirth: what is the evidence and what should we be doing?

In Australia, as in other developed countries, approximately 40-50% of stillbirths are of unknown aetiology. Emerging evidence suggests stillbirths are often multifactorial. The absence of a known cause leads to uncertainty regarding the risk of recurrence, which can cause extreme anguish for parents that may manifest as guilt, anger or bewilderment. Further, clinical endeavours to prevent recurrences in future pregnancies are impaired by lack of a defined aetiology. Therefore, efforts to provide an aetiological diagnosis of stillbirth impact upon all aspects of care of the mother, and inform many parts of clinical decision making. Despite the magnitude of the problem, that is 7 stillbirths per 1000 births in Australia, diagnostic efforts to discover viral aetiologies are often minimal. Viruses and other difficult to culture organisms have been postulated as the aetiology of a number of obstetric and paediatric conditions of unknown cause, including stillbirth. Reasons forwarded for testing stillbirth cases for infectious agents are non-medical factors, including addressing all parents' need for diagnostic closure, identifying infectious agents as a sporadic cause of stillbirth to reassure parents and clinicians regarding risk for future pregnancies, and to reduce unnecessary testing. It is clear that viral agents including rubella, human cytomegalovirus (CMV), parvovirus B19, herpes simplex virus (HSV), lymphocytic choriomeningitis virus (LCMV), and varicella zoster virus (VZV) may cause intrauterine deaths. Evidence for many other agents is that minimal or asymptomatic infections also occur, so improved markers of adverse outcomes are needed. The role of other viruses and difficult-to-culture organisms in stillbirth is uncertain, and needs more research. However, testing stillborn babies for some viral agents remains a useful adjunct to histopathological and other examinations at autopsy. Modern molecular techniques such as multiplex PCR, allow searches for multiple agents. Now that such testing is available, it is important to assess the clinical usefulness of such testing.

Synoviocyte infection with adeno-associated virus (AAV) is neutralized by human synovial fluid from arthritis patients and depends on AAV serotype

Intraarticular gene transfer with adeno-associated viral (AAV) vectors may allow efficient therapeutic transgene expression within the joint in diseases such as rheumatoid arthritis (RA), allowing high expression of the protein within the joint, preventing both systemic diffusion and side effects. However, humans demonstrate antibodies against AAV, which can influence gene transfer. To better understand critical obstacles to intraarticular gene therapy with AAV, we have previously shown that synovial fluid (SF) contains IgG to AAV that neutralizes chondrocyte infection in vitro. Our objective was therefore to compare neutralization exerted by SF from RA patients for four different AAV serotypes (AAV serotypes 1, 2, 5, and 8) on human primary synoviocytes. Serotype 2 infected synoviocytes most efficiently followed, in decreasing order, by serotypes 1, 5, and 8. SF from all patients partially inhibited infection of synoviocytes by at least one of the four serotypes. Infection with serotypes 1 and 2 was the most inhibited by SF, whereas inhibition was weak for serotypes 5 and 8. Last, we have shown that inhibition of AAV1/interleukin (IL)-4 infection of synoviocytes by SF could be reversed by increasing the number of AAV1/IL-4 particles, with a dose-dependent effect. We conclude that the most infectious AAV serotypes (1 and 2) in synoviocytes are also the serotypes most neutralized by SF. Thus, serotype 5 seems to demonstrate the best infection efficiency:immunogenicity ratio for local use in articular diseases. These data may be useful for tailoring intraarticular AAV-mediated gene therapy to individual patients.

Detection of adeno-associated virus 2 and parvovirus B19 in the human dorsolateral prefrontal cortex

Although animal parvoviruses have long been recognized as causes of brain pathology in multiple animal models, especially during early development, human parvoviruses are rarely thought of as neurotropic or causes of neuropathology in humans. However, several recent case reports have suggested possible associations of parvovirus B19 (B19) infection with various neurological and neuropsychiatric symptoms. Adeno-associated virus 2 (AAV2) is related to B19 but has thus far not been shown to be associated with any human disease but is of clinical interest because of the recent use of recombinant AAV vectors in human gene therapy, including gene delivery to the brain. To date, there have been no large-scale studies of the propensity of wild-type human parvoviruses to infect the brain. The Stanley Medical Research Institute Brain Collection offered a unique opportunity to study a large sample (n = 104) of dorsolateral prefrontal cortex (DLPC) DNAs isolated from unaffected control, schizophrenic, and bipolar disorder brains for the presence of parvoviral sequences. This is the first investigator-blinded study to document the presence of parvoviral sequences in the DLPC by utilizing highly sensitive nested polymerase chain reaction (nPCR) and DNA sequencing. Of the overall sample, 6.7% to 12.5% were positive for AAV2, and 14.4% to 42.3% were positive for B19 sequences, with no statistical differences among subgroups. This is the first report to demonstrate the presence of human parvoviruses in a large cohort of adult DLPC, which underscores the need to gain a better insight into the basic biology of parvovirus-brain interactions, including mechanisms of infection and persistence.

Serotype-specific detection of adeno-associated virus during laboratory preparation

Adeno-associated virus (AAV) is a small single-stranded DNA member of the family Parvoviradae with at least eight recognized human serotypes, several of which are being studied as candidate vectors for gene therapy. When multiple serotypes are handled in the same laboratory, it is critical to know the serotype of a sample with certainty. Here, a rapid and reliable PCR-based method is presented for the identification of serotypes 2, 3B or 6 and for screening for cross contamination. The PCR assay is based on the use of differentially annealing, serotype-specific primer pairs targeted to the hypervariable regions of the capsid coding region of the AAV genome. Identity is determined by the presence of a PCR product of size specific to each serotype. Multiplexing the reaction allows all serotypes to be queried in a single reaction tube and greatly diminishes the presence of false positives. The method is capable of detecting as little as 25 fg of a contaminating serotype and is potentially extensible to other AAV serotypes.

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.

Long-term expression and repeated administration of AAV type 1, 2 and 5 vectors in skeletal muscle of immunocompetent adult mice

Adeno-associated viral (AAV) vectors promote long-term gene transfer into muscle in many animal species. Increased expression levels may be obtained by using alternative serotypes in combination with repeated administrations. Here we compared AAV vectors based on serotypes 1, 2 and 5 in immunocompetent mice and assessed the feasibility of multiple administrations of either identical (readministration) or different (cross-administration) serotype-based vectors. A 1-year-long dose-response study confirmed the superiority of recombinant (r)AAV1, achieving transduction levels 5 to 10-fold higher than rAAV2 and rAAV5 in mouse skeletal muscle, respectively. Repeated administration demonstrated that increased gene transfer level was achieved with a second injection of rAAV1 following the first administration of rAAV2 or rAAV5. A readministration study with a vector encoding a different gene allowed the evaluation of gene expression from the second vector only. All three rAAVs were inhibited when the animals were previously exposed to the same serotype. In contrast, no significant change in gene expression from the second vector was observed in cross-administration. A humoral immune response was elicited against the viral capsid for all three serotypes following the initial exposure. Neutralizing antibody (NAB) levels correlated with the vector dose injected. No significant cross-reactivity of NAB from a given serotype toward another was observed in vitro. These data provide the first direct comparative evaluation of re- and cross-administration of rAAV1, rAAV2 and rAAV5 in muscle, and further indicate that rAAV1 is capable of transducing muscle tissue when cross-administered.

Correlation of human papillomavirus and adeno-associated virus 2 infection in cytology with Korean women

The purpose of our prospective study was to investigate the prevalence of adeno-associated virus (AAV) and human papillomavirus (HPV) 16 and/or HPV 18 infection in Korean women with normal cervical smears and those with HPV-associated cervical intraepithelial neoplasia (CIN) and cancer in cytobrush samples, and to evaluate the correlation between AAV 2 and HPV 16 and/or HPV 18 infection. AAV 2 was detected in CIN I (9.7%), CIN II (20%), CIN III (22.8%), and cancer (10%). HPV 16 was detected in CIN I (42%), CIN II (55%), CIN III (54.3%), and cancer (70%). HPV 18 was detected in CIN I (51.6%), CIN II (50%), CIN III (62.8%), and cancer (43.3%). HPV 16 or HPV 18 was detected in CIN I (18.3%), CIN II (80%), CIN III (71.4%), and cancer (80%). In normal and HPV-infected group, AAV 2 DNA was detected in 16.3% and 4.4% of samples, respectively. HPV 16 was detected in 10.2% of normal patients and in 44.4% of HPV-infected patients, and HPV 18 was detected in 12.2% of normal patients and in 40% of HPV-infected patients. HPV 16 or HPV 18 was detected in 18.3% of normal patients and in 57.7% of HPV infection. The correlation between AAV 2 and HPV 16 was statistically significant in normal and CIN I/II group only, and AAV 2 and HPV 16 and/or HPV 18 showed no correlation. Therefore, the correlation between AAV and HPV were not statistically significant. These data support the previous reports that AAV might not be associated with cervical tumorigenesis.

Current issues in adeno-associated viral vector production

Adeno-associated virus (AAV) is currently one of the most promising systems for human gene therapy. Numerous preclinical studies have documented the excellent safety profile of these vectors along with their impressive performances in their favored target, consisting of highly differentiated postmitotic tissues such as muscle, central nervous system and liver. Clinical trials have been conducted confirming these data, but also emphasizing the requirement of further high-tech developments of the production and purification procedures that would allow both scaling-up and improvement of vector batch quality, necessary to human application. The scope of this review will be the state of the art in the various production methods of recombinant AAV (rAAV), delimiting their respective perimeter of application and also their main advantages and drawbacks, and thereby shedding light on the main challenges to take in the near future to bring AAV vectors more widely into the clinics.

Mutations on the external surfaces of adeno-associated virus type 2 capsids that affect transduction and neutralization

Mutations were made at 64 positions on the external surface of the adeno-associated virus type 2 (AAV-2) capsid in regions expected to bind antibodies. The 127 mutations included 57 single alanine substitutions, 41 single nonalanine substitutions, 27 multiple mutations, and 2 insertions. Mutants were assayed for capsid synthesis, heparin binding, in vitro transduction, and binding and neutralization by murine monoclonal and human polyclonal antibodies. All mutants made capsid proteins within a level about 20-fold of that made by the wild type. All but seven mutants bound heparin as well as the wild type. Forty-two mutants transduced human cells at least as well as the wild type, and 10 mutants increased transducing activity up to ninefold more than the wild type. Eighteen adjacent alanine substitutions diminished transduction from 10- to 100,000-fold but had no effect on heparin binding and define an area (dead zone) required for transduction that is distinct from the previously characterized heparin receptor binding site. Mutations that reduced binding and neutralization by a murine monoclonal antibody (A20) were localized, while mutations that reduced neutralization by individual human sera or by pooled human, intravenous immunoglobulin G (IVIG) were dispersed over a larger area. Mutations that reduced binding by A20 also reduced neutralization. However, a mutation that reduced the binding of IVIG by 90% did not reduce neutralization, and mutations that reduced neutralization by IVIG did not reduce its binding. Combinations of mutations did not significantly increase transduction or resistance to neutralization by IVIG. These mutations define areas on the surface of the AAV-2 capsid that are important determinants of transduction and antibody neutralization.

Adeno-Associated Virus Pseudotype 5 Vector Improves Gene Transfer in Arthritic Joints

The potential for gene delivery to joints, using recombinant adeno-associated virus (rAAV) vectors for the treatment of rheumatoid arthritis (RA), has received much attention. Different serotypes have different virion shell proteins and, as a consequence, vary in their tropism for diverse tissues. The aim of this study was to compare the transduction efficiency of different AAV serotypes encoding murine secreted alkaline phosphatase (mSEAP) or Escherichia coli beta-galactosidase for intraarticular gene delivery in an experimental model of arthritis. The vectors contained AAV2 terminal repeats flanking the reporter gene in an AAV1, AAV2, or AAV5 capsid, producing the pseudotypes rAAV-2/1, rAAV-2/2, and rAAV-2/5. Left knee joints of mice with collagen-induced arthritis were injected and transgene expression was analyzed by chemiluminescence or direct in situ staining of frozen sections. We show for the first time that intraarticular gene transfer with AAV- 2/5 was far more efficient than with the other serotypes tested. Transgene expression was detectable as early as 7 days after injection, reached a maximum at 21 days, and was stably expressed for at least 130 days, whereas AAV-2/1- and AAV-2/2-mediated expression levels were barely detectable. These findings provide a practical application for future local AAV-mediated gene therapy trials in RA.

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.

Immune responses to adeno-associated virus and its recombinant vectors

Recombinant adeno-associated virus (rAAV) vectors have emerged as highly promising for use in gene transfer for a variety of reasons, including lack of pathogenicity and wide host range. In addition, all virus-encoded genes have been removed from standard rAAV vectors, resulting in their comparatively low intrinsic immunogenicity. For gene replacement strategies, transgenes encoded by rAAV vectors may induce less robust host immune responses than other vectors in vivo. However, under appropriate conditions, host immune responses can be generated against rAAV-encoded transgenes, raising the potential for their use in vaccine development. In this review, we summarize current understanding of the generation of both undesirable and beneficial host immune responses directed against rAAV and encoded transgenes, and how they might be exploited for optimal use of this promising vector system.

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.

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.

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.

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.

Detection of adeno-associated virus in human semen: does viral infection play a role in the pathogenesis of male infertility?

OBJECTIVE

To evaluate the occurrence of adeno-associated virus (AAV) DNA and/or human papillomavirus (HPV) DNA in the semen of infertile men as a possible factor in the pathogenesis of male infertility.

DESIGN

Descriptive pilot study.

SETTING

University-based diagnostic and research laboratory.

PATIENT(S)

Semen specimens were collected from 30 men with diagnosed infertility and from 8 control subjects.

INTERVENTION(S)

Diagnostic spermiograms were made and the semen specimens were separated into seminal fluid, nonspermatozoal cells, and spermatozoa using a Ficoll gradient technique.

MAIN OUTCOME MEASURE(S)

The presence of AAV and HPV DNA in the different fractions of the ejaculates from the infertile men and the control subjects was detected by polymerase chain reaction. Semen quality was analyzed according to World Health Organization guidelines.

RESULT(S)

Adeno-associated virus DNA was detected in 30% (9/30) of the ejaculates from the infertile men. No AAV DNA was found in the ejaculates from the 8 control subjects. In 8 of 9 samples, AAV DNA could be found only in the spermatozoal fraction of the specimen. Seven of 9 semen specimens that contained viral DNA also demonstrated oligoasthenozoospermia. Both AAV and HPV DNA was found in the spermatozoal fraction of 3 of 30 specimens.

CONCLUSION(S)

The data demonstrate for the first time the occurrence of AAV infection in human semen. Sperm motility seems to be affected by the presence of AAV.

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.

Human adeno-associated virus type 5 is only distantly related to other known primate helper-dependent parvoviruses

We have characterized 95% (4,404 nucleotides) of the genome of adeno-associated virus type 5 (AAV5), including part of the terminal repeats and the terminal resolution site. Our results show that AAV5 is different from all other described AAV serotypes at the nucleotide level and at the amino acid level. The sequence homology to AAV2, AAV3B, AAV4, and AAV6 at the nucleotide level is only between 54 and 56%. The positive strand contains two large open reading frames (ORFs). The left ORF encodes the nonstructural (Rep) proteins, and the right ORF encodes the structural (Cap) proteins. At the amino acid level the identities with the capsid proteins of other AAVs range between 51 and 59%, with a high degree of heterogeneity in regions which are considered to be on the exterior surface of the viral capsid. The overall identity for the nonstructural Rep proteins at the amino acid level is 54.4%. It is lowest at the C-terminal 128 amino acids (10%). There are only two instead of the common three putative Zn fingers in the Rep proteins. The Cap protein data suggest differences in capsid surfaces and raise the possibility of a host range distinct from those of other parvoviruses. This may have important implications for AAV vectors used in gene therapy.