Evidence for and localization of vegetative viral DNA replication by autoradiographic detection of RNA-DNA hybrids in sections of tumors induced by Shope papilloma virus

High beta-HPV DNA loads and strong seroreactivity are present in epidermodysplasia verruciformis

Epidermodysplasia verruciformis (EV) is a rare disease, characterized by cutaneous warts and associated with a strong predisposition to beta-genus human papillomavirus (HPV). Earlier studies reported high copy numbers of HPV-DNA in nearly all skin tumors from EV patients, but neither HPV replication status in non-lesional skin nor anti-HPV seroreactivity in these patients have been reported yet. We therefore performed a comprehensive viral load analysis for the more common beta-HPV types on skin samples and plucked eyebrow hairs from four EV patients treated at our dermatology department. The results clearly demonstrate that they carry a multiplicity (up to eighteen types) of beta-HPV genotypes in both skin sites. Worthy of note, a high intrapatient concordance for specific types between hair bulbs and skin biopsies was observed and the same beta-PV profile was maintained over time. Viral load analysis revealed a load range between less than one HPV-DNA copy per 100 cells to more than 400 HPV-DNA copies per cell in both eyebrow hairs and skin proliferative lesions. Evaluation of seroreactivity to beta-HPV types in the four EV patients revealed that antibodies against the 16 beta-HPV were significantly more prevalent and showed higher titers than in the controls.

The utility of the K6/ODC transgenic mouse as an alternative short term dermal model for carcinogenicity testing of pharmaceuticals

The use of transgenic rodents may overcome many limitations of traditional cancer studies. Regulatory perspectives continue to evolve as new models are developed and validated. The transgenic mouse, K6/ODC, develops epidermal tumors when exposed to genotoxic carcinogens. In this study, K6/ODC mice were evaluated for model fitness and health robustness in a 36-week study to determine oncogenic risk of residual DNA in vaccines from neoplastic cell substrates. K6/ODC and C57BL/6 mice were treated with T24-H-ras expression plasmid, carrier vector DNA, or saline topically or by subcutaneous injection. One group of K6/ODC mice received 7,12-dimethylbenz-[a]anthracene [DMBA] dermally. Only DMBA-treated mice developed papillomas by six weeks, increasing in incidence to 25 weeks. By week 11, many K6/ODC mice showed severe dehydration and dermal eczema. By week 32, (6/8) surviving K6/ODC mice showed loss of mobility and balance. Microscopic evaluation of tissues revealed dermal/sebaceous gland hyperplasia, follicular dystrophy, splenic atrophy, and amyloid deposition/neutrophilic infiltration within liver, heart, and spleen, in all K6/ODC mice. Pathology was not detected in C57BL/6 mice. Progressive adverse health, decreased survival, and failure to develop papillomas to the H-ras plasmid suggest that K6/ODC mice may be an inappropriate alternative model for detection of oncogenic DNA and pharmaceutical carcinogenicity testing.

The bovine papillomavirus replicon

The bovine papillomavirus genome contains two cis-acting sequences which can serve as signals for replication. At least three virally encoded genes seem to be involved in plasmid replication: E6, E6/7 and E1. Mutations in either the E6 or the E7 open reading frame create plasmids that are maintained at a low copy number per cell. Mutations in the E1 open reading frame are absolutely lethal to replication. Complementation experiments show that these mutations define separate genes. Experiments are described which show that cells harbouring plasmids with mutations in either the E6 or the E7 open reading frame acquire an immunity to high copy-number plasmids. We suggest that either the cell or the virus encodes a repressor. The positive action of E6 and E6/7 modulates the activity of this repressor to allow for the high copy-number state. Though the viral oncogenes are capable of transforming cells separately when they are expressed as part of certain recombinant DNA expression systems, it is clear that, in the context of the entire viral replicon, interactions between the transforming functions and replication functions must exist.

Human papillomavirus: cause of epithelial lacrimal sac neoplasia?

PURPOSE

Epithelial tumours of the lacrimal sac are rare but important entities that may carry grave prognoses. In this study the prevalence and possible role of human papillomavirus (HPV) infection in epithelial tumours of the lacrimal sac were evaluated.

METHODS

Five papillomas and six carcinomas of the lacrimal sac were investigated for the presence of HPV using the polymerase chain reaction (PCR) technique. Fifteen specimens of dacryocystitis were included in the PCR reactions as controls. Furthermore, DNA in situ hybridization (ISH) and RNA ISH were performed.

RESULTS

Low-risk HPV types 6 or 11 were identified in all four lacrimal sac papillomas suitable for PCR analysis and in situ hybridization. Four of six lacrimal sac carcinomas harboured HPV. One carcinoma was positive for HPV 11 only, two carcinomas had concomitant infection with HPV 6 or 11 and high-risk HPV 16, and the remaining carcinoma was positive for HPV 16. All specimens of dacryocystitis were betaglobin-positive and HPV-negative. Using DNA ISH, two papillomas and a single carcinoma showed evidence for vegetative HPV 11 DNA replication, whereas no HPV 16 DNA replication was found in the five carcinomas tested. HPV 11 RNA was demonstrated in two papillomas.

CONCLUSIONS

By analysing 11 epithelial lacrimal sac papillomas and carcinomas using PCR, DNA ISH and RNA ISH, we found HPV DNA in all investigated transitional epithelium tumours of the lacrimal sac. HPV RNA was present in two of eight epithelial lacrimal sac tumours positive for HPV DNA. As RNA degrades fast in paraffin-embedded tissue, only a small fraction of DNA-positive tumours can be expected to be RNA-positive. We therefore suggest that HPV infection is associated with the development of lacrimal sac papillomas and carcinomas.

Variation in the nucleotide sequence of cottontail rabbit papillomavirus a and b subtypes affects wart regression and malignant transformation and level of viral replication in domestic rabbits

We previously reported the partial characterization of two cottontail rabbit papillomavirus (CRPV) subtypes with strikingly divergent E6 and E7 oncoproteins. We report now the complete nucleotide sequences of these subtypes, referred to as CRPVa4 (7,868 nucleotides) and CRPVb (7,867 nucleotides). The CRPVa4 and CRPVb genomes differed at 238 (3%) nucleotide positions, whereas CRPVa4 and the prototype CRPV differed by only 5 nucleotides. The most variable region (7% nucleotide divergence) included the long regulatory region (LRR) and the E6 and E7 genes. A mutation in the stop codon resulted in an 8-amino-acid-longer CRPVb E4 protein, and a nucleotide deletion reduced the coding capacity of the E5 gene from 101 to 25 amino acids. In domestic rabbits homozygous for a specific haplotype of the DRA and DQA genes of the major histocompatibility complex, warts induced by CRPVb DNA or a chimeric genome containing the CRPVb LRR/E6/E7 region showed an early regression, whereas warts induced by CRPVa4 or a chimeric genome containing the CRPVa4 LRR/E6/E7 region persisted and evolved into carcinomas. In contrast, most CRPVa, CRPVb, and chimeric CRPV DNA-induced warts showed no early regression in rabbits homozygous for another DRA-DQA haplotype. Little, if any, viral replication is usually observed in domestic rabbit warts. When warts induced by CRPVa and CRPVb virions and DNA were compared, the number of cells positive for viral DNA or capsid antigens was found to be greater by 1 order of magnitude for specimens induced by CRPVb. Thus, both sequence variation in the LRR/E6/E7 region and the genetic constitution of the host influence the expression of the oncogenic potential of CRPV. Furthermore, intratype variation may overcome to some extent the host restriction of CRPV replication in domestic rabbits.

In situ hybridisation in perspective

In the introduction to this review two questions were posed: is the technology associated with ISH ready for general use, and will the method become an important investigative tool? With the exception of the demonstration of some single and low copy sequences, non-radioactive ISH is now sufficiently developed and simplified to make it a routine technique. It is also clear that ISH will continue to have an important research role. In diagnostic pathology the technique is already providing valuable information and the present decade should see the development of many more diagnostic applications.

The 68-kilodalton E1 protein of bovine papillomavirus is a DNA binding phosphoprotein which associates with the E2 transcriptional activator in vitro

The E1 open reading frame of bovine papillomavirus type 1 encodes factors necessary for extrachromosomal maintenance of the viral genome in transformed cells. To facilitate biochemical characterization of the gene products encoded by this open reading frame, we have expressed the full-length E1 protein in a baculovirus-insect cell system. This protein was found to be phosphorylated and localized to the nucleus of infected cells. The E1 protein alone has affinity for DNA but appears to lack specificity for viral sequences. In addition, we present evidence that the E1 protein interacts with the virally encoded transcriptional activator E2 in vitro. These results are consistent with a model in which the E1 protein, as part of a complex with E2, interacts with specific DNA sequences in the viral genome.

Analysis of human papillomavirus type 16 late mRNA 3' processing signals in vitro and in vivo

In the human papillomavirus type 16 genome, three late mRNA putative 3' processing signals, designated LP1, LP2, and LP3, are located downstream of the late coding region. Our results show, both in vitro and in vivo, that in HeLa cells, the LP2 signal functions. Thus, the restriction in human papillomavirus type 16 late-gene expression observed in HeLa cells and other nondifferentiated epithelial cells is not achieved by regulation of late mRNA poly(A) site usage. Interestingly, alteration of three nucleotides in the GU-rich downstream sequence element converts the nonfunctional LP1 to an efficient 3' processing site, suggesting that LP1 may function in cell types other than HeLa, such as differentiated keratinocytes. Our transfection studies have identified a negative regulatory element located immediately upstream of the late mRNA 3' processing signals; this element was not associated with any alteration in 3' processing and may act as an mRNA instability element.

Loss of bovine papillomavirus DNA replication control in growth-arrested transformed cells

The bovine papillomavirus type 1 (BPV-1) genome replicates as a plasmid within the nuclei of BPV-1-transformed murine C127 cells at a constant multiple copy number, and spontaneous amplification of the viral DNA is rarely observed. We report here that a mutant BPV-1 plasmid within a contact-inhibited C127 cell line replicated as a stable multicopy plasmid in exponentially growing cells but amplified to a high level in confluent cell culture. In situ hybridization analysis revealed that most of the mutant viral DNA amplification occurred in a minor subpopulation of cells within the culture. These consisted of giant nondividing cells with greatly enlarged nuclei, a cell form which was specifically induced in stationary-phase cultures. These observations indicated that expression of a viral DNA replication factor was cell growth stage specific. Consistent with this hypothesis, considerable amplification of wild-type BPV-1 DNA associated with characteristic giant cell formation was observed in typical wild-type virus-transformed C127 cultures following a period of growth arrest achieved by serum deprivation. Further observations indicated that induction of the giant-cell phenotype was dependent on BPV-1 gene expression and implicated a viral E1 replication factor in this process. Moreover, heterogeneity in virus genome copy numbers within the giant-cell population suggested a complex regulation of induction of DNA synthesis in these cells. It appears that this process represents a mechanism employed by the virus to ensure maximal viral DNA synthesis within a growth-arrested cell. Fundamental questions concerning the integration of the virus-cell control circuitry in proliferating and resting cells are discussed.

Human papillomaviruses and carcinomas

The recognition of multiple types of human papillomaviruses has resulted in remarkable progress in the detection of persisting viral nucleic acid sequences in carcinomas. The consistent transcription in tumors of two early open reading frames, E6 and E7, with few exceptions (Lehn et al., 1985), indicates a role for the products of these genes in the induction and/or maintenance of the transformed state. A number of studies have shown that in vitro transformation can be achieved by transfection of E6/E7 DNA, and proteins encoded by these DNA sequences can be demonstrated in primary human keratinocytes immortalized by this DNA (Kaur et al., 1989). Mutagenesis experiments are needed to determine the absolute requirement for and function of these genes in transformation. A preferential association of some types with benign lesions while others may be frequently found in malignant tumors has been observed. HPV types 5 and 8 in epidermodysplasia verruciformis patients and types 16, 18, 31, 33, etc. in genital lesions are most frequently associated with progression to malignancy, whereas other types, such as HPV-6,-10, -11, and -20, are regularly identified in benign warts. Such distinctions are not absolute but provide the initial steps toward establishing a causal role for some human papillomaviruses in carcinomas. The need for well-designed epidemiological studies in concert with optimum molecular and serologic evaluations is evident (Armstrong et al., 1988). The data from human and animal studies indicate that papillomaviruses contribute significantly to the development of many, if not all, carcinomas, but we do not yet have a clear understanding of the importance of other interacting viral, chemical, or cellular factors. The application of gene cloning and non-stringent hybridization (Law et al., 1979) has provided us with an apparently ever-increasing catalog of human papillomaviruses. More effort is now required to establish their prevalence, the natural history of infection, and the mechanism of neoplastic transformation.

Viral and cellular oncogenes in papillomavirus-associated cancers

Papillomaviruses are one of several factors implicated in the aetiology of squamous cell carcinomas both in man and in animals. Their potential for malignant transformation is fully expressed when co-operation takes place between viral functions, cellular functions and chemical or physical co-carcinogens. This review presents a brief description of the viral transforming genes and of the cellular genes involved in transformation, and attempts to analyse how the co-operation between the two sets of genes is achieved.

Evaluation of methods for detecting human papillomavirus deoxyribonucleotide sequences in clinical specimens

Specimens from 26 condylomatous lesions, 24 invasive cancer cells, and 33 cervices, without evidence of the diseases, were tested for the presence of human papillomavirus (HPV) types 6, 11, 16, and 18 by Southern blot hybridization, in situ filter hybridization, or in situ tissue hybridization methods. A total of 89% (23 of 26) of the condylomatous lesions contained HPV DNAs, as determined by one or more of the methods. The positive rates for the detection of HPV DNA in condylomas by the different methods were 82% for Southern blot hybridization, 62% for in situ filter hybridization, and 72% for in situ tissue hybridization. Among the specimens from patients with cancer, HPV DNA was found in 83% (19 of 23) by one or more of the methods. Positive rates of 89 and 70%, respectively, were obtained for cancer lesions tested by the filter in situ and Southern blot hybridization methods; however, only 30% of those lesions were positive by the in situ tissue hybridization method. Thirteen percent of the control cervices were positive for HPV DNA by one or more of the assays. With respect to all disease categories, the methods had comparable sensitivities and specificities, except for the in situ tissue hybridization method, which revealed a specificity of 72% for condylomatous lesions and 30% for invasive cancer cells.

Hybridization histochemistry

The location of gene expression by hybridization histochemistry is being applied in many areas of research and diagnosis. The aim of this technique is to detect specific mRNA in cells and tissues by hybridization with a complementary DNA or RNA probe. Requirements for optimal specificity, sensitivity, resolution and speed of detection may not all be encompassed in one simple technique suitable for all applications, thus appropriate procedures should be selected for specific objectives. With reference to published procedures and our own extensive experience, we have evaluated fixatives, probes, labels and other aspects of the technique critical to the preservation and hybridization in situ of mRNA and detection and quantitation of hybrids.

Distribution pattern of human papilloma virus 16 genome in cervical neoplasia by molecular in situ hybridization of tissue sections

Using a highly sensitive method with single-stranded RNA probes, we analyzed the distribution pattern of HPV 16 DNA by in situ hybridization in CIN II (10 cases), CIN III (11 cases) and in invasive cervical carcinoma (17 cases). The technique used detected as little as 20-50 viral genomes per cell. This sensitive technique unmasked HPV 16 genomes in the basal cells of all forms of CIN. In CIN III viral genomes were present throughout the entire thickness of the epithelium. There was a striking difference in the distribution of viral DNA in CIN II compared with CIN III and invasive cancer. Variable viral genome distribution was observed in CIN II with the highest copy number in the area of epithelial differentiation. In contrast, CIN III showed a uniform distribution pattern of HPV genomes reflecting the lack of epithelial maturation. The majority of invasive carcinomas showed the same uniform distribution of the HPV 16 genomes as CIN III.

Complementation of a bovine papilloma virus low-copy-number mutant: evidence for a temporal requirement of the complementing gene

We identified a bovine papilloma virus function encoded by the E6/E7 gene, which is required for both BPV high-copy-number replication and maintenance of transformation of cultured cells. A cDNA copy of this gene was isolated and expressed from a retrovirus vector. We found that complete complementation of a BPV low-copy-number mutant (dl576) by the cDNA encoding the E6/E7 gene was temporally dependent. When both the E6/E7 cDNA and dl576 were introduced together into cells, wild-type replication and stable transformation resulted. In contrast, introduction of the complementing cDNA into cells already carrying dl576 led to only partial amplification of the resident mutant DNA accompanied by a restoration of the transformed phenotype. These results, along with other findings, suggest that the establishment of BPV plasmid replication occurs in two stages: an initial amplification of the incoming DNA followed by stable homeostatic replication which maintains the existing copy number.

Complementation of a bovine papilloma virus low-copy-number mutant: evidence for a temporal requirement of the complementing gene

We identified a bovine papilloma virus function encoded by the E6/E7 gene, which is required for both BPV high-copy-number replication and maintenance of transformation of cultured cells. A cDNA copy of this gene was isolated and expressed from a retrovirus vector. We found that complete complementation of a BPV low-copy-number mutant (dl576) by the cDNA encoding the E6/E7 gene was temporally dependent. When both the E6/E7 cDNA and dl576 were introduced together into cells, wild-type replication and stable transformation resulted. In contrast, introduction of the complementing cDNA into cells already carrying dl576 led to only partial amplification of the resident mutant DNA accompanied by a restoration of the transformed phenotype. These results, along with other findings, suggest that the establishment of BPV plasmid replication occurs in two stages: an initial amplification of the incoming DNA followed by stable homeostatic replication which maintains the existing copy number.

Amplification of a bovine papillomavirus-simian virus 40 chimera

A chimeric plasmid, pBOP, containing bovine papillomavirus (BPV) and the origin of replication from simian virus 40 (SV40) was constructed. The plasmid was established in mouse cells, where it was maintained stably as an autonomous BPV replicon. Lines carrying pBOP were fused to cells of COS-7, a simian line producing SV40 T antigen. Replication dependent on the SV40 origin and having the kinetics and approximate amplitude of an SV40 infection ensued. SV40 replication is therefore dominant over BPV replication, and the SV40 origin can conveniently be used to amplify lower-copy-number plasmids in mammalian cells.

Physical state and transcription of the cottontail rabbit papillomavirus genome in warts and transplantable VX2 and VX7 carcinomas of domestic rabbits

The physical state and the transcription of the genome of cottontail rabbit papillomavirus (CRPV) in non-virus-producing warts and in the VX2 and VX7 transplantable carcinomas of domestic rabbits were compared. The CRPV DNA present in VX2 and VX7 carcinomas (10 to 20 and 100 to 200 genome equivalents per diploid cell, respectively) was found to be entirely integrated into the cellular DNA, most probably as head-to-tail tandem repeats, in contrast to warts, in which viral DNA (10 to 100 copies per diploid cell) was found only as free, mainly monomeric, molecules. In the VX7 tumor, ca. 50% of the viral DNA molecules were found to be longer than one genome length, indicating that viral DNA rearrangements had occurred. A major viral transcript of 1,250 bases was detected in warts and in VX2 and VX7 carcinomas. Complementary sequences were localized within the E region, the putative transforming region inferred from the nucleotide sequence of the CRPV genome (I. Giri, O. Danos, and M. Yaniv, manuscript in preparation). Analysis of heteroduplexes formed between single-stranded CRPV DNA and polyadenylated RNAs from the VX2 tumor showed that the 1,250-base RNA resulted from the splicing of the sequences corresponding to the open reading frame E6 to those corresponding to the 3' third of E2. A second viral transcript, measuring 2,000 bases, was detected in warts and, in lesser amounts than the 1,250-base species, in VX2 carcinoma, and a 2,100-base RNA was found in VX7 carcinoma. Complementary sequences to these messengers were localized to the same part of the genome as the 1,250-base species and to a contiguous fragment situated upstream. Heteroduplex analysis showed that the 2,000-base species from VX2 carcinoma resulted from the splicing of the sequences corresponding to E6 and E7 to those corresponding to the 3' third of E2. The sequences spliced out upon the maturation of the two messengers of VX2 carcinoma correspond to E1, the two-thirds of E2, and most of E4. Additional transcripts were found in VX7 carcinoma, a major 3,100-base species transcribed from the E region, and several minor species, measuring from 2,400 bases, which all hybridize with a subgenomic fragment contained in the L region encoding the viral capsid polypeptides. This could account for the antiviral antibodies found in animals bearing the VX7 carcinoma.

HSV, CMV, and HPV in human neoplasia

We are studying the role of sexually transmitted viruses in the development of human tumors. The persistence of herpes simplex virus, cytomegalovirus, and human papillomavirus nucleic acid sequences has been examined using cloned viral DNA sequences as probes. The relationship of the viruses to various stages in the progression of neoplasia is examined, with particular reference to the role of viral and/or cellular genes in the initiation, promotion, and maintenance of the neoplastic phenotype. The human tumors of major interest in this context are carcinomas of the cervix, vulva, and anus and Kaposi's sarcoma. The minimal fragment of HSV-2 DNA detected in cervical tumors is contained within a 656-bp sequence that can be used in transfection experiments to transform rodent cells in vitro to a malignant phenotype. However, neither this fragment nor any other is consistently retained in cervical tumors, suggesting that this viral DNA may initiate but not maintain the transformed phenotype.

The search for a culture system for papillomavirus

Papillomaviruses induce tumors of keratinocytes. Vegetative viral DNA replication and virion assembly are seen in those cells which are in the process of keratinizing or are keratinized. To date, no cell culture system has been developed that permits expression of the complete viral life cycle. Keratinocytes infected in culture may harbor the virus as a stable, replicating episome, but they do not support vegetative viral growth, nor do they become immortalized or transformed. The major obstacle in using keratinocyte cultures may be related to a dual need for transformation and full differentiation. Some animal papillomaviruses have been shown to be capable of transforming cultured murine fibroblasts. The fibroblast model is useful for identifying the viral-transforming gene(s) and their products.

Unintegrated viral DNA sequences in a hamster tumor induced by bovine papilloma virus

A fibrosarcoma was induced in a hamster by bovine papilloma virus type 2 (BPV2). The content of BPV2 DNA sequences was measured by DNA-DNA and cRNA-DNA hybridizations. The tumor contained approximately 300 BPV2 genome equivalents per cell. Southern blot hybridization indicated that the viral DNA was in free form, the entire genome most likely being present. In situ hybridization with BPV2 cRNA showed that multiple genome copies were present in each cell. Neither virus particles nor virus coat antigens could be detected in the tumor. A cell line was established from the fibrosarcoma, and the cells contained multiple copies of the BPV2 genome. The latter was in free form, and all of the DNA sequences appeared to be present in multiple copies and in all cells. An extensive search failed to reveal the presence of virus or viral antigens.

Cervical carcinoma: detection of herpes simplex virus RNA in cells undergoing neoplastic change

3H-HSV-2 DNA has been hybridized in situ to frozen sectioned tissue from human cervical biopsies. RNA complementary to the virus-specific probe was detected in cells undergoing pre-malignant changes, but not in the cells of the fully developed squamous-cell cancer.

Multiple copies of Shope virus DNA are present in cells of benign and malignant non-virus-producing neoplasms

In an initial efforts to characterize the virological basis of neoplasia in the Shope papilloma-carcinoma system, the extent to which the viral genome is present in non-virus-producing benign and malignant tumors in domestic rabbits was established. Employing nick-translated radioactive viral DNA purified from productively infected papillomas on cotton tail rabbits as a probe, it was found that (i) papillomas, primary carcinomas, and metastatic carcinomas contain 10 to about 100 copies of the viral genome per diploid cell equivalent of DNA and (ii) viral DNA is present in detectable amounts in essentially all neoplastic cells. These results are consistent with the suggestion that continued presence of the viral genome is necessary for induction and maintenance of malignant as well as benign neoplasms.

Localization of viral DNA-replication in sections of human warts by nucleic acid hybridization with complementary RNA of human papilloma virus Type 1

Using complementary RNA of human papilloma virus type 1 (HPV1) and in situ hybridization techniques the localization of viral DNA replication was studied in sections of 38 human virus acanthomata from 31 different patients. In five cases significant labeling was detected by autoradiography. Labeling started always in the first or the second suprabasal cell layer and was strongly limited to the nuclei. A remarkable early beginning of the vacuolated process seemed to be correlated with the visible DNA replication. No labeling could be detected in the basal cell layer. This suggests that these cells contain at the most only a small number of viral genomes. Our findings represent only the situation in human warts definitely caused by HPV 1. We are not able to say, whether our negative hybridization results in the remaining warts indicate either the scarcity of viral genomes within these sections or their infection by a different agent.

Characterization of a new type of human papillomavirus that causes skin warts

A human papillomavirus (HPV) was isolated from the lesions of a patient (ML) bearing numerous hand common warts. This virus was compared with the well-characterized HPV found in typical plantar warts (plantar HPV). ML and plantar HPV DNAs have similar molecular weights (5.26 x 10(6) and 5.23 x 10(6), respectively) but were shown to be different by restriction enzyme analysis. When the cleavage products of both DNAs by endonuclease EcoRI, BamI, HpaI, or Hind were analyzed by electron microscopy, one, two, one, and four fragments were detected for ML HPV DNA instead of the two, one, two, and six fragments, respectively, detected for plantar HPV DNA. In contrast to plantar HPV DNA, a high proportion of ML HPV DNA molecules were resistant to these restriction enzymes. Most, if not all, of the molecules were either resistant to BamI and sensitive to EcoRI or sensitive to BamI and resistant to EcoRI. After denaturation and renaturation of the cleavage products of ML HPV DNA by a mixture of the two enzymes, the circular "heteroduplexes" formed showed one to three heterology loops corresponding to about 4 to 8% of the genome length. No sequence homology was detected between ML and plantar HPV DNAs by cRNA-DNA filter hybridization, by measuring the reassociation kinetics of an iodinated plantar HPV DNA in the presence of a 25-fold excess of ML HPV DNA, or by the heteroduplex technique. The two viruses had distinct electrophoretic polypeptide patterns and showed no antigenic cross-reaction by immunodiffusion or immunofluorescence techniques. Preliminary cRNA-DNA hybridization experiments, using viral DNAs from single or pooled plantar or hand warts, suggest that hand common warts are associated with viruses similar or related to ML HPV. The existence of at least two distinct types of HPVs that cause skin warts was demonstrated; they were provisionally called HPV type 1 and HPV type 2, with plantar HPV and ML HPV as prototypical viruses, respectively.

Bovine papilloma virus: presence of virus-specific DNA sequences in naturally occurring equine tumors

Four of five spontaneous benign equine connective tissue tumors of unknown etiology and a bovine papilloma virus (BPV)-induced equine tumor contained BPV-specific DNA sequences as determined by DNA-DNA hybridization of DNA from tumors with BPV DNA labeled in vitro. Analysis of the kinetics of reassociation indicated that 20-75% of the BPV genome was present in the various tumors. The number of partial BPV genome equivalents ranged from 60 to 500 copies per diploid quantity of cellular DNA. Thermal denaturation profiles of duplexes formed between labeled BPV DNA and DNA from tumor cells indicated two tumors contained viral DNA with base sequences identical to BPV DNA. Three tumors (including DNA from the BPV-induced tumor) contained BPV-related DNA sequences that were less thermally stable. The decrease in thermal denaturation temperature may be due to the presence of (adenine + thymine)-rich regions of the BPV genome in the tumor cells.

Human papillomavirus DNA: physical map

Human papillomavirus (HPV) DNA form I (supercoiled) was prepared from plantar warts. HPV DNA was cleaved with restriction enzymes obtained from the following sources: escherichia coli (EcoRI), Hemophilus influenzae strain Rd (both unfractionated Hind and aeparated HindII and HindIII enzymes) and Hemophilus parainfluenzae (HpaI). The cleavage products were analyzed by polyacrylamide gradient slab gel electrophoresis and electron microscopy. HPV DNA was cleaved into two fragments by EcoRI (87% and 13% of the genome) and into six fragments, ranging in size from 33.5 to 1.2% of the genome, by Hind endonucleases. The six Hind fragments result from the cleavage of three sequences recognized by HindII, two of which are also cleaved by HpaI, and of three sequence recognized by HindIII. The order of these fragments was determined by comparing their size with that of the fragments obtained with HindII, HindIII, HpaI, and the mixture of HindIII + Hpal. The two EcoRI cleavage sites were located on two adjacent Hind fragments and one of these sites has been taken for the zero point to construct a physical map. The treatment of superhelical HPV DNA with bacteriophage T4 gene 32 protein yields circular structures with a denaturation loop. The cleavage of these complexes with EcoRI and HindIII has shown two easily denatured regions which were located on the cleavage map.

Detection of virus-specific DNA sequences by quantitative in situ hybridization during infection with SV40

In situ hybridization has been used as a quantitative method to study the replication of SV40 during lytic infection. Various parameters have been defined such as fixation and denaturation of cytological preparations, concentration of complementary (3H)-cRNA and volume of buffer used for the hybridization reaction. When all these parameters are carefully controlled, a reproducibility of +/-10% can be obtained for the quantitative study of the system SV40-monkey kidney cells (CV-1). In this system, it is evident that the synthesis of viral DNA is not synchronized in confluent cells. Moreover, a proportion of 20 to 30% of cells are not labelled whatever the multiplicity of infection. In SV40-transformed cells, it was not possible to detect significantly the integrated genome due either to the small size of the genome or to the fact that the number of genome-equivalents integrated at the same place is too low to yield a radioactivitity superior to background level for long periods of exposure.

The virus of epidermodysplasia verruciformis: electron microscopic and fluorescent antibody studies

Five cases of epidermodysplasia verruciformis were studied for viral particles and antigens. In all benign lesions tested, viral particles and antigens were observed by electron microscopy of ultrathin sections and/or tissue extracts and by fluorescent antibody staining with an antiserum against human wart virus. Both viral particles and antigens were observed in the cells of the stratum granulosum and the stratum corneum and not in those of deeper layers. Viral particles and antigens were observed in nuclei. Viral particles resembled morphologically the virus of common human warts. In two, one on the forehead and the other on the inner aspect of the upper thigh, of six lesions showing the histology of early malignancy, viral particles were observed by electron microscopy of ultrathin sections and/or tissue extracts. Four advanced malignant lesions, two primary ulcerated squamous cell carcinomas and two recurrent carcinomas, were similarly studied. In none of them, were viral particles or antigens detected. These results suggest that (1) the virus of epidermodysplasia verruciformis is related with that of common human warts both morphologically and antigenically, (2) at least some of the virus-induced lesions of epidermodysplasia verruciformis become malignant, and (3) when the lesions are completely replaced with malignant cells, neither viral particles nor antigens are recognizable in them.

Detection of viral DNA sequences in adenovirus-transformed cells by in situ hybridization

Cytological preparations of cells transformed by members of three groups of human adenoviruses, adenovirus 12, 7, and 2, were annealed with radioactive complementary RNA (cRNA) (4 x 10(7) to 4.5 x 10(7) dpm/mug) prepared by copying viral DNA with the Escherichia coli DNA-directed RNA polymerase. These in situ hybridizations detected adenovirus-specific DNA sequences in interphase nuclei when transformed cells were annealed with homologous viral cRNA, but not with heterologous viral cRNA. The highest autoradiographic grain counts were found over adenovirus 7-transformed cell nuclei, next over adenovirus 12-, and the lowest over adenovirus 2-transformed cell nuclei. This is the same order as found by reassociation kinetic measurements (K. Fujinaga and M. Green, unpublished data).