Detection of adeno-associated virus DNA in human genital tissue and in material from spontaneous abortion

Pathogenicity and virulence of human adenovirus F41: Possible links to severe hepatitis in children

Over 100 human adenoviruses (HAdVs) have been isolated and allocated to seven species, A-G. Species F comprises two members-HAdV-F40 and HAdV-F41. As their primary site of infection is the gastrointestinal tract they have been termed, with species A, enteric adenoviruses. HAdV-F40 and HAdV-F41 are a common cause of gastroenteritis and diarrhoea in children. Partly because of difficulties in propagating the viruses in the laboratory, due to their restrictions on growth in many cell lines, our knowledge of the properties of individual viral proteins is limited. However, the structure of HAdV-F41 has recently been determined by cryo-electron microscopy. The overall structure is similar to those of HAdV-C5 and HAdV-D26 although with some differences. The sequence and arrangement of the hexon hypervariable region 1 (HVR1) and the arrangement of the C-terminal region of protein IX differ. Variations in the penton base and hexon HVR1 may play a role in facilitating infection of intestinal cells by HAdV-F41. A unique feature of HAdV-F40 and F41, among human adenoviruses, is the presence and expression of two fibre genes, giving long and short fibre proteins. This may also contribute to the tropism of these viruses. HAdV-F41 has been linked to a recent outbreak of severe acute hepatitis "of unknown origin" in young children. Further investigation has shown a very high prevalence of adeno-associated virus-2 in the liver and/or plasma of some cohorts of patients. These observations have proved controversial as HAdV-F41 had not been reported to infect the liver and AAV-2 has generally been considered harmless.

Gestational Viral Infections: Role of Host Immune System

Viral infections in pregnancy are major causes of maternal and fetal morbidity and mortality. Infections can develop in the neonate transplacentally, perinatally, or postnatally (from breast milk or other sources) and lead to different clinical manifestations, depending on the viral agent and the gestational age at exposure. Viewing the peculiar tolerogenic status which characterizes pregnancy, viruses could exploit this peculiar immunological status to spread or affect the maternal immune system, adopting several evasion strategies. In fact, both DNA and RNA virus might have a deep impact on both innate and acquired immune systems. For this reason, investigating the interaction with these pathogens and the host's immune system during pregnancy is crucial not only for the development of most effective therapies and diagnosis but mostly for prevention. In this review, we will analyze some of the most important DNA and RNA viruses related to gestational infections.

Vaginal and tumor microbiomes in gynecological cancer (Review)

Cervical, ovarian and endometrial cancer are the three most common types of gynecologic cancer. As a hub, the vagina connects the site of gynecological cancer with the external environment. Lactobacilli participate in the formation of a healthy vaginal microenvironment as the first line of defense against pathogen invasion; a dysbiotic vaginal microenvironment loses its original protective function and is associated with the onset, metastasis, poor efficacy and poor prognosis of gynecological cancer. The early diagnosis of cancer is the key to improve the survival time of patients with cancer. The screening of Porphyromonas, Sneathia and Atopobium vaginae, and other microbial markers, can assist the diagnosis of gynecological cancer, and screen out the high-risk population as early as possible. With the in-depth study of the microbes in tumor tissues, reasearchers have analyzed the immunological associations of microorganisms in tumor tissues. Due to the structural-functional interconnection between the organ of gynecological tumorigenesis and the vagina, the present study aims to review the relationship between vaginal and tumor microorganisms and gynecological cancer in terms of occurrence, screening, treatment and prognosis.

Adeno-associated virus infection and its impact in human health: an overview

Discovered as a contaminant of adenovirus stocks in the 1960s, adeno-associated virus (AAV) is a mono-stranded DNA virus that depends on helper factors to replicate. Even though AAV is endemic in the human population (35-80%), it is remarkable that many issues concerning the natural infection by this virus remain unanswered. In this study, we reflect on the main basic aspects of AAV biology and provide an overview of the studies exploring the impact of AAV infection on human health, focusing on three major research areas including, (i) cervical and (ii) liver cancer, and (iii) reproductive system disorders. Conflicting results have been obtained into the association of AAV infection with the occurrence of adverse reproductive outcomes, such as placental complications, spontaneous abortion, and fertility disorders, or with a protective role in HPV-related cervical carcinogenesis. Noteworthy, recent reports have identified AAV insertional mutagenesis as a novel risk factor for the development of hepatocellular carcinoma. This latest finding raises concern regarding the widespread usage of AAV vectors in liver-targeted gene therapy.

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.

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.

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.

Detection of Viral RNA Splicing in Diagnostic Virology

This chapter is the first one to introduce the detection of viral RNA splicing as a new tool for clinical diagnosis of virus infections. These include various infections caused by influenza viruses, human immunodeficiency viruses (HIV), human T-cell leukemia viruses (HTLV), Torque teno viruses (TTV), parvoviruses, adenoviruses, hepatitis B virus, polyomaviruses, herpesviruses, and papillomaviruses. Detection of viral RNA splicing for active viral gene expression in a clinical sample is a nucleic acid-based detection. The interpretation of the detected viral RNA splicing results is straightforward without concern for carry-over DNA contamination, because the spliced RNA is smaller than its corresponding DNA template.

Although many methods can be used, a simple method to detect viral RNA splicing is reverse transcription-polymerase chain reaction (RT-PCR). In principle, the detection of spliced RNA transcripts by RT-PCR depends on amplicon selection and primer design. The most common approach is the amplification over the intron regions by a set of primers in flanking exons. A larger product than the predicted size of smaller, spliced RNA is in general an unspliced RNA or contaminating viral genomic DNA. A spliced mRNA always gives a smaller RT-PCR product than its unspliced RNA due to removal of intron sequences by RNA splicing. The contaminating viral DNA can be determined by a minus RT amplification (PCR). Alternatively, specific amplification of a spliced RNA can be obtained by using an exon-exon junction primer because the sequence at exon-exon junction is not present in the unspliced RNA nor in viral genomic DNA.

A Molecular Epidemiological Investigation of Carriage of the Adeno-Associated Virus in Murine Rodents and House Shrews in China

OBJECTIVE

To investigate the prevalence of the adeno-associated virus (AAV) in murine rodents and house shrews in 4 provinces of China.

METHODS

A total of 469 murine rodents and 19 house shrews were captured between May 2015 and May 2017. Cap gene of AAV sequences was obtained to evaluate the genetic characteristics of rat AAV.

RESULTS

Rat AAVs were found in 54.7% (267/488) of throat swabs, 14.3% (70/488) of fecal samples, and 18.4% (41/223) of serum samples. Rat AAVs were detected in 3 species of murine rodents including Rattus norvegicus (34.8%), R. tanezumi (43.0%), and R. losea (2.3%), and house shrews (Suncus murinus) (26.1%) from the selected sampling sites. Fourteen near-full-length Cap gene sequences, ranging in length from 2,156 to 2,169 nt, were isolated from the fecal samples of R. norvegicus and R. tanezumi. These 14 sequences shared a high identity of 97.4% at the nucleotide level and 99.1% at the amino acid level. Phylogenetic analysis showed that the rat AAV formed a distinct clade, distinguishable from the AAV discovered in humans and in other animals.

CONCLUSIONS

A high prevalence of rat AAV that was highly conserved within the Cap gene was found in 3 common murine rodents and house shrews in China.

Adeno-Associated Virus Vectors and Stem Cells: Friends or Foes?

The infusion of healthy stem cells into a patient-termed "stem-cell therapy"-has shown great promise for the treatment of genetic and non-genetic diseases, including mucopolysaccharidosis type 1, Parkinson's disease, multiple sclerosis, numerous immunodeficiency disorders, and aplastic anemia. Stem cells for cell therapy can be collected from the patient (autologous) or collected from another "healthy" individual (allogeneic). The use of allogenic stem cells is accompanied with the potentially fatal risk that the transplanted donor T cells will reject the patient's cells-a process termed "graft-versus-host disease." Therefore, the use of autologous stem cells is preferred, at least from the immunological perspective. However, an obvious drawback is that inherently as "self," they contain the disease mutation. As such, autologous cells for use in cell therapies often require genetic "correction" (i.e., gene addition or editing) prior to cell infusion and therefore the requirement for some form of nucleic acid delivery, which sets the stage for the AAV controversy discussed herein. Despite being the most clinically applied gene delivery context to date, unlike other more concerning integrating and non-integrating vectors such as retroviruses and adenovirus, those based on adeno-associated virus (AAV) have not been employed in the clinic. Furthermore, published data regarding AAV vector transduction of stem cells are inconsistent in regards to vector transduction efficiency, while the pendulum swings far in the other direction with demonstrations of AAV vector-induced toxicity in undifferentiated cells. The variation present in the literature examining the transduction efficiency of AAV vectors in stem cells may be due to numerous factors, including inconsistencies in stem-cell collection, cell culture, vector preparation, and/or transduction conditions. This review summarizes the controversy surrounding AAV vector transduction of stem cells, hopefully setting the stage for future elucidation and eventual therapeutic applications.

AAV: An Overview of Unanswered Questions

AAV has been studied for 55 years and has been developed as a vector for about 35 years. By now, there is a fairly good idea of the dimensions of what would be useful to know to employ AAV optimally as a vector, but there are still many unanswered questions within the system. As with all biological systems, each good experiment raises further questions to answer. This article provides an overview of those areas in which unknown information can be identified and of those questions that have not yet been recognized. Some of these are touched on in the six review articles in this issue of Human Gene Therapy.

Risks associated with viral infections during pregnancy

Despite the prevalence of viral infections in the American population, we still have a limited understanding of how they affect pregnancy and fetal development. Viruses can gain access to the decidua and placenta by ascending from the lower reproductive tract or via hematogenous transmission. Viral tropism for the decidua and placenta is then dependent on viral entry receptor expression in these tissues as well as on the maternal immune response to the virus. These factors vary by cell type and gestational age and can be affected by changes to the in utero environment and maternal immunity. Some viruses can directly infect the fetus at specific times during gestation, while some only infect the placenta. Both scenarios can result in severe birth defects or pregnancy loss. Systemic maternal viral infections can also affect the pregnancy, and these can be especially dangerous, because pregnant women suffer higher virus-associated morbidity and mortality than do nonpregnant counterparts. In this Review, we discuss the potential contributions of maternal, placental, and fetal viral infection to pregnancy outcome, fetal development, and maternal well-being.

High Prevalence of Infectious Adeno-associated Virus (AAV) in Human Peripheral Blood Mononuclear Cells Indicative of T Lymphocytes as Sites of AAV Persistence

Seroepidemiology shows that infections with adeno-associated virus (AAV) are widespread, but diverse AAV serotypes isolated from humans or nonhuman primates have so far not been proven to be causes of human disease. In view of the increasing success of AAV-derived vectors in human gene therapy, definition of the in vivo sites of wild-type AAV persistence and the clinical consequences of its reactivation is becoming increasingly urgent. Here, we identify the presumed cell type for AAV persistence in the human host by highly sensitive AAV PCRs developed for the full spectrum of human AAV serotypes. In genomic-DNA samples from leukocytes of 243 healthy blood donors, 34% were found to be AAV positive, predominantly AAV type 2 (AAV2) (77%), AAV5 (19%), and additional serotypes. Roughly 11% of the blood donors had mixed AAV infections. AAV prevalence was dramatically increased in immunosuppressed patients, 76% of whom were AAV positive. Of these, at least 45% displayed mixed infections. Follow-up of single blood donors over 2 years allowed repeated detection of the initial and/or additional AAV serotypes, suggestive of fluctuating, persistent infection. Leukocyte separation revealed that AAV resided in CD3⁺ T lymphocytes, perceived as the putative in vivo site of AAV persistence. Moreover, infectious AAVs of various serotypes could be rescued and propagated from numerous samples. The high prevalence and broad spectrum of human AAVs in leukocytes closely follow AAV seroepidemiology. Immunosuppression obviously enhances AAV replication in parallel with activation of human cytomegalovirus (HCMV) and human herpesvirus 6 (HHV-6), reminiscent of herpesvirus-induced AAV activation.

IMPORTANCE

Adeno-associated virus is viewed as apathogenic and replication defective, requiring coinfection with adenovirus or herpesvirus for productive infection. In vivo persistence of a defective virus requires latency in specialized cell types to escape the host immune response until viral spread becomes possible. Reactivation from latency can be induced by diverse stimuli, including infections, typically induced upon host immunosuppression. We show for the first time that infectious AAV is highly prevalent in human leukocytes, specifically T lymphocytes, and that AAV is strongly amplified upon immunosuppression, along with reactivation of latent human herpesviruses. In the absence of an animal model to study the AAV life cycle, our findings in the human host will advance the understanding of AAV latency, reactivation, and in vivo pathogenesis.

Prolonged expression of an anti-HIV-1 gp120 minibody to the female rhesus macaque lower genital tract by AAV gene transfer

Topical microbicides are a leading strategy for prevention of HIV mucosal infection to women, however, numerous pharmacokinetic limitations associated with coitally-related dosing strategy have contributed to their limited success. Here we test the hypothesis that adeno-associated virus (AAV) mediated delivery of the b12 human anti-HIV-1 gp120 minibody gene to the lower genital tract of female rhesus macaques (Rh) can provide prolonged expression of b12 minibodies in the cervical-vaginal secretions. Gene transfer studies demonstrated that, of various GFP-expressing AAV serotypes, AAV-6 most efficiently transduced freshly immortalized and primary genital epithelial cells (PGECs) of female Rh in vitro. In addition, AAV-6-b12 minibody transduction of Rh PGECs led to inhibition of SHIV162p4 transmigration and virus infectivity in vitro. AAV-6-GFP could also successfully transduce vaginal epithelial cells of Rh when applied intra-vaginally, including p63+ epithelial stem cells. Moreover, intra-vaginal application of AAV-6-b12 to female Rh resulted in prolonged minibody detection in their vaginal secretions throughout the 79 day study period. These data provide proof-of-principle that AAV-6-mediated delivery of anti-HIV broadly neutralizing antibody (BnAb) genes to the lower genital tract of female Rh results in persistent minibody detection for several months. This strategy offers promise that an anti-HIV-1 genetic microbicide strategy may be possible in which topical application of AAV vector, with periodic reapplication as needed, may provide sustained local BnAb expression and protection.

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.

Ewing's Sarcoma: Development of RNA Interference-Based Therapy for Advanced Disease

Ewing's sarcoma tumors are associated with chromosomal translocation between the EWS gene and the ETS transcription factor gene. These unique target sequences provide opportunity for RNA interference(i)-based therapy. A summary of RNAi mechanism and therapeutically designed products including siRNA, shRNA and bi-shRNA are described. Comparison is made between each of these approaches. Systemic RNAi-based therapy, however, requires protected delivery to the Ewing's sarcoma tumor site for activity. Delivery systems which have been most effective in preclinical and clinical testing are reviewed, followed by preclinical assessment of various silencing strategies with demonstration of effectiveness to EWS/FLI-1 target sequences. It is concluded that RNAi-based therapeutics may have testable and achievable activity in management of Ewing's sarcoma.

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.

Stable human FIX expression after 0.9G intrauterine gene transfer of self-complementary adeno-associated viral vector 5 and 8 in macaques

Intrauterine gene transfer (IUGT) offers ontological advantages including immune naiveté mediating tolerance to the vector and transgenic products, and effecting a cure before development of irreversible pathology. Despite proof-of-principle in rodent models, expression efficacy with a therapeutic transgene has yet to be demonstrated in a preclinical nonhuman primate (NHP) model. We aimed to determine the efficacy of human Factor IX (hFIX) expression after adeno-associated-viral (AAV)-mediated IUGT in NHP. We injected 1.0-1.95 × 10(13) vector genomes (vg)/kg of self-complementary (sc) AAV5 and 8 with a LP1-driven hFIX transgene intravenously in 0.9G late gestation NHP fetuses, leading to widespread transduction with liver tropism. Liver-specific hFIX expression was stably maintained between 8 and 112% of normal activity in injected offspring followed up for 2-22 months. AAV8 induced higher hFIX expression (P = 0.005) and milder immune response than AAV5. Random hepatocellular integration was found with no hotspots. Transplacental spread led to low-level maternal tissue transduction, without evidence of immunotoxicity or germline transduction in maternal oocytes. A single intravenous injection of scAAV-LP1-hFIXco to NHP fetuses in late-gestation produced sustained clinically-relevant levels of hFIX with liver-specific expression and a non-neutralizing immune response. These data are encouraging for conditions where gene transfer has the potential to avert perinatal death and long-term irreversible sequelae.

Role of the infections in recurrent spontaneous abortion

Embryo-fetal infections have been reported to cause recurrent spontaneous abortions (RSAs) at a rate lower than 4%. The possible mechanisms include production of toxic metabolic byproducts, fetal or placental infection, chronic endometrial infection, and chorio-amnionitis. Viruses appear to be the most frequently involved pathogens, since some of them can produce chronic or recurrent maternal infection. In particular, cytomegalovirus during pregnancy can reach the placenta by viremia, following both primary and recurrent infection, or by ascending route from the cervix, mostly following reactivation. Another herpesvirus, herpes simplex virus type 2, less frequently type 1, causes recurrent infections of the genital tract, which can involve the feto-placental unit. Parvoviruses have also been implicated in the development of repeated fetal loss. Among bacterial infections, Chlamydia trachomatis, Ureaplasma urealyticum,and Mycoplasma hominis have been mostly associated with occurrence of RSA. An increased risk of abortion among women with bacterial vaginosis (BV) during early pregnancy was also shown, but questions arise about the role of chronic BV in its occurrence. Although a definitive relationship between recurrently active infections and RSA is still lacking, mostly due to difficulties in demonstrating the pathogenic role of each individual isolated pathogen, diagnosis and therapy of RSA-related infections should be attempted. The diagnosis of infectious agents as a possible cause of RSA might lead to a therapeutic approach with antiviral drugs and antibiotics or using immunoglobulins, which can display both anti-infective neutralizing and immunomodulating properties.

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.

AAV's anatomy: roadmap for optimizing vectors for translational success

Adeno-Associated Virus based vectors (rAAV) are advantageous for human gene therapy due to low inflammatory responses, lack of toxicity, natural persistence, and ability to transencapsidate the genome allowing large variations in vector biology and tropism. Over sixty clinical trials have been conducted using rAAV serotype 2 for gene delivery with a number demonstrating success in immunoprivileged sites, including the retina and the CNS. Furthermore, an increasing number of trials have been initiated utilizing other serotypes of AAV to exploit vector tropism, trafficking, and expression efficiency. While these trials have demonstrated success in safety with emerging success in clinical outcomes, one benefit has been identification of issues associated with vector administration in humans (e.g. the role of pre-existing antibody responses, loss of transgene expression in non-immunoprivileged sites, and low transgene expression levels). For these reasons, several strategies are being used to optimize rAAV vectors, ranging from addition of exogenous agents for immune evasion to optimization of the transgene cassette for enhanced therapeutic output. By far, the vast majority of approaches have focused on genetic manipulation of the viral capsid. These methods include rational mutagenesis, engineering of targeting peptides, generation of chimeric particles, library and directed evolution approaches, as well as immune evasion modifications. Overall, these modifications have created a new repertoire of AAV vectors with improved targeting, transgene expression, and immune evasion. Continued work in these areas should synergize strategies to improve capsids and transgene cassettes that will eventually lead to optimized vectors ideally suited for translational success.

The expanding range of parvoviruses which infect humans

The first human parvoviruses to be described (1960s) were the adeno-associated viruses (AAVs, now classed as dependoviruses), originally identified as contaminants of cell cultures, followed by parvovirus B19 (B19V) in 1974, the first parvovirus to be definitively shown to be pathogenic. More recently two new groups of parvoviruses, the human bocaviruses (HuBoV) and the Parv4 viruses have been identified. These four groups of human viruses are all members of different genera within the Parvovirus family, and have very different biology, epidemiology and disease associations from each other. This review will provide an overview of the virological, pathogenic and clinical features of the different human paroviruses, and how these new viruses and their variants fit into the current understanding of parvovirus infection.

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 serotype 2 induces cell-mediated immune responses directed against multiple epitopes of the capsid protein VP1

Adeno-associated virus serotype 2 (AAV-2) has been developed as a gene therapy vector. Antibody and cell-mediated immune responses to AAV-2 or AAV-2-transfected cells may confound the therapeutic use of such vectors in clinical practice. In one of the most detailed examinations of AAV-2 immunity in humans to date, cell-mediated and humoral immune responses to AAV-2 were characterized from a panel of healthy blood donors. The extent of AAV-2-specific antibody in humans was determined by examination of circulating AAV-2-specific total IgG levels in plasma from 45 normal donors. Forty-one donors were seropositive and responses were dominated by IgG1 and IgG2 subclasses. Conversely, AAV-2-specific IgG3 levels were consistently low in all donors. Cell-mediated immune recall responses were detectable in nearly half the population studied. In vitro restimulation with AAV-2 of peripheral blood mononuclear cell cultures from 16 donors elicited gamma interferon (IFN-γ) (ten donors), interleukin-10 (IL-10) (eight donors) and interleukin-13 (IL-13) (four donors) responses. Using a series of overlapping peptides derived from the sequence of the VP1 viral capsid protein, a total of 59 candidate T-cell epitopes were identified. Human leukocyte antigen characterization of donors revealed that the population studied included diverse haplotypes, but that at least 17 epitopes were recognized by multiple donors and could be regarded as immunodominant. These data indicate that robust immunological memory to AAV-2 is established. The diversity of sequences recognized suggests that attempts to modify the AAV-2 capsid, as a strategy to avoid confounding immunity, will not be feasible.

Reducing the risk of adeno-associated virus (AAV) vector mobilization with AAV type 5 vectors

Current adeno-associated virus (AAV) gene therapy vectors package a transgene flanked by the terminal repeats (TRs) of AAV type 2 (AAV2). Although these vectors are replication deficient, wild-type (wt) AAV2 prevalent in the human population could lead to replication and packaging of a type 2 TR (TR2)-flanked transgene in trans during superinfection by a helper virus, leading to "mobilization" of the vector genome from treated cells. More importantly, it appears likely that the majority of currently characterized AAV serotypes as well as the majority of new novel isolates are capable of rescuing and replicating AAV2 vector templates. To investigate this possibility, we flanked a green fluorescent protein transgene with type 2 and, the most divergent AAV serotype, type 5 TRs (TR2 or TR5). Consistent with AAV clades, AAV5 specifically replicated TR5 vectors, while AAV2 and AAV6 replicated TR2-flanked vectors. To exploit this specificity, we created a TR5 vector production system for Cap1 to Cap5. Next, we showed that persisting recombinant AAV genomes flanked by TR2s or TR5s were mobilized in vitro after addition of the cognate AAV Rep (as well as Rep6 for TR2) and adenoviral helper. Finally, we showed that a cell line containing a stably integrated wt AAV2 genome resulted in mobilization of a TR2-flanked vector but not a TR5-flanked vector upon adenoviral superinfection. Based on these data and the relative prevalence of wt AAV serotypes in the population, we propose that TR5 vectors have a significantly lower risk of mobilization and should be considered for clinical use.

Diverse IgG subclass responses to adeno-associated virus infection and vector administration

Humoral immune responses occur following exposure to Adeno-associated virus (AAV) or AAV vectors. Many studies characterized antibody responses to AAV, but human IgG subclass responses to AAV have not been previously described. In this study, IgG subclass responses were examined in serum samples of normal human subjects exposed to wild-type AAV, subjects injected intramuscularly with AAV vectors and subjects injected intravascularly with AAV vectors. A diversity of IgG subclass responses to AAV capsid were found in different subjects. IgG1 was found to be the dominant response. IgG2, IgG3, and IgG4 responses were also observed in most normal human subjects; IgG2 and IgG3 each represented the major fraction of total anti-AAV capsid IgG in a subset of normal donors. Subjects exposed to AAV vectors showed IgG responses to AAV capsid of all four IgG subclasses. IgG responses to AAV capsid in clinical trial subjects were inversely proportional to the level of pre-existing anti-AAV antibody and independent of the vector dose. The high levels of anti-AAV capsid IgG1 can mask differences in IgG2, IgG3, and IgG4 responses that were observed in this study. Analysis of IgG subclass distribution of anti-AAV capsid antibodies indicates a complex, non-uniform pattern of responses to this viral antigen. J. Med. Virol. 81:65-74, 2009. (c) 2008 Wiley-Liss, Inc.

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.

Placental inflammation and viral infection are implicated in second trimester pregnancy loss

OBJECTIVE

Second trimester pregnancy loss continues to be a poorly understood adverse obstetric outcome. A case control study was performed to determine if: (1) similar to early spontaneous preterm birth, second trimester loss is associated with histologic chorioamnionitis (HCA); and (2) if HCA is present, which organisms may mediate this placental inflammation.

STUDY DESIGN

Cases were patients with a spontaneous second trimester loss. Controls were patients who presented for induction of labor for fetal or maternal indications. Nested polymerase chain reaction (PCR) was performed on placental tissues to detect the presence of viruses and pathogenic and atypical bacteria. Chi-square and Fisher exact test were used to determine if HCA and/or the presence of virus or bacteria were significantly associated with second trimester loss. The associations of interest were adjusted for possible confounders using multivariable logistic regression.

RESULTS

HCA was more prevalent in cases (67%) than controls (16%) (P < .001). Seventy-nine percent (66/84) of cases and 44% (7/16) of controls were positive for any virus (P = .01). The rate of bacterial infection was similar in both cases and controls (P = .35). In multivariable logistic regression models, HCA (odds ratio [OR] 14.58, 2.62-81.15) and the presence of any virus (OR 6.62, 1.56-28.07) were independently associated with second trimester loss.

CONCLUSION

These studies demonstrate that spontaneous second trimester loss is strongly associated with HCA and viral infections.

Correlates of placental infection with cytomegalovirus, parvovirus B19 or human herpes virus 7

Vertical transmission of viruses is an important cause of morbidity in the fetus and neonate. Placental viral infection indicates risk of vertical transmission, but not always transmission to, or disease of the fetus. Specimens from mothers and babies from three groups-two prospective and one retrospective cohort-were tested for pathogens of teratogenic potential using multiplex PCR. Placental infection was present in 13% of the 105 samples collected. Assessment of the prospective cohorts showed cytomegalovirus (CMV) detected in 4% of placentae from unselected women, parvovirus B19 in 1% and Ureaplasma parvum in 1% of placentae. In a retrospective cohort of women at high risk of transmitting congenital infection due to seroconversion during pregnancy, miscarriage or stillbirth, CMV was detected in 64% and human herpes virus type 7 in 9% of placentae. Of 14 PCR-positive placentae, two were associated with the birth of a living symptomatic infant, two with stillbirth, one with miscarriage, and two with elective terminations of pregnancy. Directed laboratory assessment of women at high risk of transmitting congenital infection, on the basis of clinical or laboratory markers, is important for accurate diagnosis of adverse outcomes of pregnancy. However, routine screening for viruses in the placentae from women with a low-risk serological profile for transmitting congenital infection is unlikely to result in significant numbers of additional diagnoses and is confounded by inadequacy of current diagnostic methods. The major pathogen detected in all cases of placental infection associated with fetal death was human CMV.

Adeno-associated virus-2 (AAV-2) causes trophoblast dysfunction, and placental AAV-2 infection is associated with preeclampsia

Shallow invasion by extravillous trophoblast cells into the uterine wall reduces placental perfusion and causes placental dysfunction, but the one or more causes of shallow placental invasion are unknown. We hypothesized that infection with adeno-associated virus-2 (AAV-2) inhibits trophoblast invasion and is associated with preeclampsia, which is a common obstetric complication resulting from placental dysfunction. We determined that transformed extravillous trophoblast (HTR-8/SVneo) cells were susceptible to AAV-2 infection in the presence or absence of adenovirus, which provides helper function for AAV-2 replication, and that AAV-2 infection reduced invasion of HTR-8/SVneo cells through an extracellular matrix before cytopathic effects were detected. In a case-control study, AAV-2 DNA was found more frequently in trophoblast cells from cases of severe preeclampsia (22/40) than from normal term deliveries (5/27, P = 0.002). These results indicate that AAV-2 infection is a previously unidentified cause of placental dysfunction. Additional studies to determine the susceptibility of extravillous trophoblast to other viruses, and the mechanisms by which viral infection impairs placental function, are warranted.

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.

Adeno-associated virus type 2 increases proteosome-dependent degradation of p21WAF1 in a human papillomavirus type 31b-positive cervical carcinoma line

Adeno-associated virus type 2 (AAV2) seropositivity is negatively correlated with the development of human papillomavirus (HPV)-associated cervical cancer. We have begun analysis of the molecular mechanisms underlying AAV2-mediated onco-suppression through cell cycle regulation in HPV-infected keratinocytes isolated from a low-grade cervical lesion. AAV2 superinfection of HPV type 31b (HPV31b)-positive cells at early times postinfection resulted in degradation of the cyclin-dependent kinase (CDK) inhibitor p21(WAF1) protein in a proteosome-dependent manner. Downstream consequences of lowering p21(WAF1) levels included a proportional loss of cyclin E/CDK2 complexes bound to p21(WAF1). The loss of stable p21(WAF1)/cyclin E/CDK2 complexes coincided with an increase in CDK2-associated kinase activity and cyclin E levels. Both events have the potential to enhance the G(1)/S transition point mediated by active cyclin E/CDK2 complexes. Concurrently, cyclin A and E2F levels were decreased, conditions reminiscent of delayed entrance into the S phase of the cell cycle. On the other hand, infection of primary human foreskin keratinocytes with AAV2 resulted in upregulation of p21(WAF1) protein levels, reminiscent of a block in G(1) phase progression. We propose that by down regulating p21(WAF1), AAV2 initiates cell cycle activities leading to enhanced G(1)/S phase-like conditions which may be favorable for AAV2-specific functions and may lead to downstream interference with HPV-associated cervical cancer progression.

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.

Striatal delivery of rAAV-hAADC to rats with preexisting immunity to AAV

We tested the hypotheses that initial immunization of rats with rAAV might limit subsequent transduction by rAAV-hAADC when stereotaxically infused into the striatum and that the level of inhibition would correlate with AAV neutralizing antibody titers. Immunohistochemical detection of AADC and analysis by stereology revealed that the control group (no immunization) had the greatest volume of distribution of AADC (20.32 +/- 2.03 mm3) (+/-SD). There was a 58% decrease in spread (8.46 +/- 3.67 mm3, P < 0.008) in the high-dose immunization group (5 x 10(10) vg rAAV-null). Transduction weakly correlated with preexisting titer levels of neutralizing antibody at the time of intrastriatal rAAV-hAADC infusion. Only rats with neutralizing antibody titers of 1:1208 +/- 332 had significantly decreased AADC transgene expression compared to the unimmunized control group. Immunohistochemistry on serial sections for inflammatory markers including GFAP, CD11b, CD4, and CD8a revealed normal morphology and no cellular infiltration, suggesting little immune reaction in the CNS. We conclude that rAAV vectors can transduce brain tissue in the context of preexisting immunity, but that efficiency of transduction declines significantly in the presence of very high titers of neutralizing antibodies. These results have important implications for gene therapy for CNS disorders.

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.

Effect of adeno-associated virus-specific immunoglobulin G in human amniotic fluid on gene transfer

Intra-amniotic administration of adeno-associated virus (AAV) vector may be an effective way to deliver gene therapy for treatment of congenital pulmonary and intestinal disorders. In an effort to understand potential barriers to intra-amniotic gene therapy better, we determined whether human amniotic fluid (AF) could act as an inhibitor of AAV2-mediated gene transfer. AF samples were obtained from 21 different human pregnancies during routine amniocentesis at 16-20 weeks of gestation. An immortalized fetal human tracheal epithelial cell line (FHTE) was infected with AAV2 containing a luciferase reporter gene driven by the SV40 promoter in the presence and absence of each AF sample. Inhibition of transgene expression was observed in 8 (38%) of the AF samples (inhibitory AF) and resulted in luciferase levels of only 1.4% +/- 0.6% of those obtained with infection in normal media. Infections in 13 samples (62%) resulted in transgene expression comparable or in excess of infection in media alone (noninhibitory AF). Removal of immunoglobulin G (IgG) from inhibitory AF samples with Protein A returned luciferase expression to control levels (119% +/- 37% of control), suggesting the possible presence of inhibiting antibody. Eleven of the AF samples were evaluated by enzyme-linked immunosorbent assay (ELISA) for specific anti-AAV antibodies. All noninhibitory AF samples were negative (titers of < 1:20; n = 3), and 6 of the 8 inhibitory samples contained specific anti-AAV antibodies at titers ranging from 1:40 to 1:160. These studies demonstrate that AF from some individuals contains AAV-specific IgG that can inhibit gene transfer.

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.

Viral infection of the trophoblast: time to take a serious look at its role in abnormal implantation and placentation?

Fragmentary evidence suggests that trophoblast viral infection may play a role in placental dysfunction, leading to complications including spontaneous miscarriage, preeclampsia, fetal growth restriction and preterm birth. Here, we review the mechanisms underlying differentiation and gestational age-dependent infection of trophoblast cells and the consequences of in vitro infection on trophoblast function. The relationship between trophoblast infection by common viruses and pregnancy outcomes is also analyzed. We conclude that there is sufficient evidence linking placental infection by common viruses, including viruses thought to be non-pathogenic or to have low pathogenicity, to indicate that this effect contributes to poor pregnancy outcome.

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.

Recent advances in liver-directed gene therapy for dyslipidemia

As currently available preventive and therapeutic interventions for hypercholesterolemia are ineffective in a substantial proportion of patients, severe dyslipidemias associated with atherosclerotic vascular disease remain an important target for the development of novel gene therapies. The development of a safe and efficient gene transfer vector has been a major challenge in liver-directed gene therapy, but recently significant progress has been made in this area. Proof-of-principle experiments indicate that the transfer of lipid-modifying genes to the liver is an effective method to restore normal plasma lipids and protect against atherosclerosis. This article summarizes recent developments in liver-directed gene delivery and reviews data on the treatment of dyslipidemias and prevention of atherosclerosis in animals. The evidence presented suggests that some of the approaches taken in animals may be ready for clinical trials in the near future.

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.

The mechanisms of placental viral infection

The placenta is a dynamic organ whose structure and function change throughout pregnancy. There is compelling evidence that the placenta plays an integral role in the vertical transmission of viruses, such as cytomegalovirus and human immunodeficiency virus, from the mother to the fetus. Although the sequelae of congenital viral infection (i.e., fetal anomalies, intrauterine fetal death, and persistent postnatal infection) may be devastating, very little is known about the passage of viruses across the placenta and the pathologic consequences of placental viral infection. We postulate that the syncytiotrophoblast, which forms a continuous barrier between the maternal and fetal circulation, is relatively resistant to viral infection. In support of this hypothesis, we observed that the susceptibility of trophoblast cells to infection by adenovirus and herpes simplex virus and the expression of viral receptors were reduced as trophoblast cells terminally differentiated into syncytiotrophoblast. Conversely, we observed that undifferentiated, extravillous trophoblast cells, which are susceptible to adenovirus infection, underwent pathologic changes (i.e., apoptosis) when infected by adenovirus in the presence of decidual lymphocytes (which were used to simulate the maternal immune response to viral infection). Based on these findings, we speculate that viral infection of extravillous trophoblast cells may negatively impact the process of placental invasion and predispose the mother and fetus to adverse reproductive outcomes that result from placental dysfunction.