Ubiquitous Human Adeno-Associated Virus Type 2 Autonomously Replicates in Differentiating Keratinocytes of a Normal Skin Model

Abstract

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

Parvovirus B‐19 Infection During Pregnancy

“…Another parvovirus, dependovirus, has been isolated in humans. However, it is not believed to cause illness, and is only thought to infect humans when it is associated with an adenovirus 5 . Cytological properties that are characteristic of parvovirus B-19 infection include giant pronormoblasts, cytoplasmic vacuolization, immature chromatin and large eosinophilic nuclear inclusion bodies 4 .…”

Molecular Biosafety

“…On the other hand, some characteristics of AAV may increase risks, including the following: detection in embryonic tissue (Burguete et al, 1999;Dutheil et al, 1997;Kiehl et al, 2002), an association with male infertility (Erles et al, 2001;Mehrle et al, 2004), the ability to replicate in some cases without a helper virus (Meyers et al, 2000), and the capability of integrating into the host genome (Miller et al, 2002). AAV is an unusual virus that can not only integrate into the host genome, but also is inserted preferentially at a specific site (on human chromosome 19).…”

Immune responses to adeno-associated virus and its recombinant vectors

“…The requirement of helper functions from another virus for AAV productive infection is generally accepted, although an as-yet unconfirmed study reported that AAV2 could replicate autonomously in normal skin keratinocytes. 16 The AAV genome is comprised of a 4.7 kb, single-stranded DNA flanked by GC-rich inverted terminal repeats (ITRs) (Figure 1). The ITRs serve as cis-active elements that are required for encapsidation and serve as elements for self-primed DNA replication.…”