The viral DNA sequences in mouse C127 cells transformed by bovine papillomavirus type 1 (BPV-1) virions, by full-length linear BPV-1 DNA, or by a defined transforming subgenomic DNA segment of BPV-1 were examined by reassociation kinetics and blot hybridization. In all cases, the transformed cells contained multiple copies ofBPV-1 DNA, present exclusively as supercoiled or nicked circular extrachromosomal molecules or as a slowly migrating complex of circular viral DNA molecules. In the transformed cell lines established from cells transfected with full-length linear BPV-1 DNA, there was recircularization of the input DNA which in some cases resulted in the loss of the restriction site used in the linearization of the DNA. In the transformed cell lines established with the defined subgenomic segment there was circularization of the DNA accompanied by the acquisition of new sequences or duplication and rearrangement of the BPV-1 sequences. In contrast to other well-studied virus transformation systems, no integration of the BPV-1 genome into the host chromosome could be detected under conditions sensitive enough to detect 0.14.2 viral genome equivalent. It was concluded that maintenance oftransformation may be mediated by nonintegrated viral DNA.Cellular transformation induced by several DNA and RNA viruses has been studied in considerable detail. In most of these systems, cellular transformation is accompanied by integration of the viral sequences required for the maintenance of transformation. Plasmid viral DNA forms have been described in cells transformed by certain DNA viruses, but almost always in association with integrated viral DNA. The papillomaviruses represent a tumor virus system which for technical reasons has received relatively little attention. The papillomaviruses along with the polyomaviruses comprise the papovavirus family (Papovaviridae) (1). Despite the morphologic similarities of their virion and genomic structures, the papillomaviruses and the polyomaviruses are separate groups ofviruses, distinguished by biological, serological, and biochemical features (2-4).The papillomaviruses are widely distributed in nature and induce benign skin tumors (warts) in their natural hosts which include humans, cattle, rabbits, dogs, sheep, chaffinches, and horses. Most papillomaviruses are highly host specific, and this property, together with the lack of an adequate tissue culture system for their propagation, has hampered studies of their molecular biology and genetics. Recently, this liability has been partially circumvented by molecularly cloning the genomes of a number of different papillomaviruses in Escherichia coli by using the certified plasmid pBR322 as cloning vector (5, 6).Whereas the proliferative changes induced by most papillomaviruses are limited to epidermal cells, lesions induced by the bovine fibropapillomaviruses (BPV-1 and BPV-2) are exceptional in that they consist of both epidermal and mesenchymal proliferative components (7). These BPVs also differ in that they can induce ...

No abstract

No abstract

Papillomaviruses are a family of nonenveloped DNA viruses that infect the skin or mucosa of their vertebrate hosts. The viral life cycle is closely tied to the differentiation of infected keratinocytes. Papillomavirus virions are released into the environment through a process known as desquamation, in which keratinocytes lose structural integrity prior to being shed from the surface of the skin. During this process, virions are exposed to an increasingly oxidative environment, leading to their stabilization through the formation of disulfide cross-links between neighboring molecules of the major capsid protein, L1. We used time-lapse cryo-electron microscopy and image analysis to study the maturation of HPV16 capsids assembled in mammalian cells and exposed to an oxidizing environment after cell lysis. Initially, the virion is a loosely connected procapsid that, under in vitro conditions, condenses over several hours into the more familiar 60-nm-diameter papillomavirus capsid. In this process, the procapsid shrinks by ~5% in diameter, its pentameric capsomers change in structure (most markedly in the axial region), and the interaction surfaces between adjacent capsomers are consolidated. A C175S mutant that cannot achieve normal inter-L1 disulfide cross-links shows maturation-related shrinkage but does not achieve the fully condensed 60-nm form. Pseudoatomic modeling based on a 9-Å resolution reconstruction of fully mature capsids revealed C-terminal disulfide-stabilized “suspended bridges” that form intercapsomeric cross-links. The data suggest a model in which procapsids exist in a range of dynamic intermediates that can be locked into increasingly mature configurations by disulfide cross-linking, possibly through a Brownian ratchet mechanism.

Several immunodeficiencies are associated with high susceptibility to persistent and progressive human papillomavirus (HPV) infection leading to a wide range of cutaneous and mucosal lesions. However, the HPV types most commonly associated with such clinical manifestations in these patients have not been systematically defined. Here, we used virion enrichment, rolling circle amplification, and deep sequencing to identify circular DNA viruses present in skin swabs and/or wart biopsy samples from 48 patients with rare genetic immunodeficiencies, including patients with warts, hypogammaglobulinemia, infections, myelokathexis (WHIM) syndrome, or epidermodysplasia verruciformis (EV). Their profiles were compared with the profiles of swabs from 14 healthy adults and warts from 6 immunologically normal children. Individual patients were typically infected with multiple HPV types; up to 26 different types were isolated from a single patient (multiple anatomical sites, one time point). Among these, we identified the complete genomes of 83 previously unknown HPV types and 35 incomplete genomes representing possible additional new types. HPV types in the genusGammapapillomaviruswere common in WHIM patients, whereas EV patients mainly shed HPVs from the genusBetapapillomavirus.Preliminary evidence based on three WHIM patients treated with plerixafor, a leukocyte mobilizing agent, suggest that longer-term therapy may correlate with decreased HPV diversity and increased predominance of HPV types associated with childhood skin warts.IMPORTANCEAlthough some members of the viral familyPapillomaviridaecause benign skin warts (papillomas), many human papillomavirus (HPV) infections are not associated with visible symptoms. For example, most healthy adults chronically shedGammapapillomavirus(Gamma) virions from apparently healthy skin surfaces. To further explore the diversity of papillomaviruses, we performed viromic surveys on immunodeficient individuals suffering from florid skin warts. Our results nearly double the number of knownGammaHPV types and suggest that WHIM syndrome patients are uniquely susceptible toGammaHPV-associated skin warts. Preliminary results suggest that treatment with the drug plerixafor may promote resolution of the unusualGammaHPV skin warts observed in WHIM patients.