Fluorescent antibody detection of the antigens of the Shope papilloma virus in papillomas of the wild and domestic rabbit

Annular Cavity Design for Photoluminescent Polymer Optical Fiber Sensors

We present optimization results on the design of a polymer optical fiber single point sensor suitable for photoluminescence-based sensing. The single point sensing design consists of one or two annular cavities, separated by a small distance, milled into the fiber and subsequently filled with a thick solution of polymer, solvent, and photoluminescent molecules, which is then allowed to dry. The design is tested by varying the depth and length of a single cavity and utilizing two cavities with varying separations. Results from experiments show a maximum response at a separation of 2 mm for which we present an analytical explanation. A geometrical, numerical simulation model, taking into account both skew and meridional rays, is developed and shows very good agreement with the experimental results. The fiber design presents a general platform that has the potential for the fabrication of multi-point photoluminescent sensors, for which it is necessary to have several points along the fiber functionalized for sensing. Furthermore, the approach with polymer fibers and polymer sensing gels allows for a robust integration of the sensing matrix and the optical fiber, more so than is possible using glass optical fibers.

INDUCTION OF TUMORS IN DOMESTIC RABBITS WITH NUCLEIC ACID PREPARATIONS FROM PARTIALLY PURIFIED SHOPE PAPILLOMA VIRUS AND FROM EXTRACTS OF THE PAPILLOMAS OF DOMESTIC AND COTTONTAIL RABBITS

A deoxyribonucleic acid preparation which showed infectivity and tumorigenic activity in domestic rabbits was isolated from the papillomatous tissue of wild cottontail rabbits by phenolic deproteinization procedure. The activity of the preparation could be completely abolished by its exposure to a minute amount (0.02 microg/ml) of DNAase. Antisera against Shope papilloma virus did not block the tumorigenic activity of the preparation, and trypsin and chymotrypsin had no effect on it. The extraction with phenol of a partially purified virus preparation also yielded extracts with tumorigenic potency. Extracts obtained from the domestic rabbit papilloma and submitted to phenolic deproteinization also proved infective and tumorigenic in rabbits of this sort, although the level of "tumorigenicity" was much lower than that of the cottontail preparations. Tests for intact virus, carried out with half of the extracts yielded wholly negative findings.

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.

Studies on the Shope rabbit papilloma virus. II. The location of infective virus in papillomas of the cottontail rabbit

A method has been devised to determine the location of infective Shope virus in the papillomas of cottontail rabbits. Frozen sections of the growths were burned selectively with a microcautery to destroy either the keratinized or proliferating layer and the sections were then applied directly to the sensitized epidermis of domestic rabbits. No papillomas appeared when the keratohyaline and keratinized areas had been eliminated leaving the proliferating cell layer, whereas papillomas arose when the proliferating cell areas were destroyed leaving the keratohyaline and keratinized layers. The results indicate that infective Shope papilloma virus is situated mainly, perhaps entirely, in the keratohyaline and keratinized areas of cottontail papillomas. This is in accord with the previous disclosure by the fluorescence technique that virus antigen in demonstrable quantity is present only in these situations.

Are animal tumor virues always virus-like?

Three tumors initiated by well characterized viruses, but in which virus is not detectable by ordinary virological techniques, are discussed. The question of the possible state of the virus within these seemingly non-infectious tumors is considered, largely from the standpoint of findings with the rabbit papilloma virus. This agent in its natural host, the cottontail rabbit, is infective, can be seen as virus bodies with the electron microscope, and can be visualized with fluorescent antibody only in the upper keratinizing cells of individual papillomas. At the growing bases of such papillomas, where neoplasia is in active progress, no infective virus is demonstrable and viral bodies cannot be visualized by either the electron microscope or fluorescent antibody. A hypothesis is presented that rabbit papilloma virus exists in cottontail papillomas in two forms-one, the complete mature virus, composed of nucleic acid and protein, and the other, immature virus, composed of naked viral nucleic acid without its protein coating. The function of the mature papilloma virus is to initiate tumor formation,-that of the immature virus, to maintain neoplasia. In the non-infective domestic rabbit papilloma, the viral nucleic acid and protein fail to combine to form mature infective virus and, as in the cottontail papilloma, neoplasia is maintained by the activity of the viral nucleic acid alone.

THE SUSCEPTIBILITY OF CHICK EMBRYO SKIN ORGAN CULTURES TO INFLUENZA VIRUS FOLLOWING EXCESS VITAMIN A

The conversion of chick embryonic epidermis to mucous epithelium by excess vitamin A in organ culture as reported by Fell and Mellanby (5) was shown to be accompanied by a corresponding change of susceptibility to influenza and vaccinia viruses. Untreated epidermis of 10- to 12-day chick embryos supported the growth of influenza (PR8) virus in organ cultures and a maximum infectivity (EID(50)) titer was reached 2 to 3 days after infection. At the same time) the epidermis showed squamous keratinization, beginning about the 4th day of cultivation. Addition of excess vitamin A (40 microg per ml) to the skin organ culture induced the following changes: (a) mucous metaplasia of the epidermis which was usually first evident after 4 to 5 days in the vitamin A medium, (b) increase in the daily and maximum yield of influenza virus, if the epidermis had been grown for 4 or more days in the vitamin A medium before infection took place, and (c) decrease in the production of vaccinia virus under similar conditions. The maximum yield of both viruses remained unchanged, however, if excess vitamin A was introduced to the organ culture at the time of virus inoculation. The magnitude of increase in the yield of influenza virus in this organ culture system was found to be proportionally related to the concentration of vitamin A added 4 or more days before inoculation of this virus. Increasing doses of vitamin A however, had no effect on the short-term growth of influenza virus in tissue cultures of chorio-allantoic membrane. Observation on the early period (2 to 12 hours) of influenza virus growth initiated in the 4-day organ cultures of chick embryonic skin showed no significant difference in virus production between the normal and the vitamin A medium groups. The change of virus specificity apparently is not due to the presence of excess vitamin A per se, but appears to be related to the change of differentiation produced in the organ culture system.

Molecular and biological characterization of cottontail rabbit papillomavirus variant DNA sequences integrated in the VX7 carcinoma

The transplantable VX7 carcinoma was derived from a tumor induced by a recoverable strain of cottontail rabbit papillomavirus (CRPV) able to replicate in domestic rabbits. Low levels of late viral gene expression have been retained through serial propagation in rabbits. We have cloned and characterized the three major types of CRPV sequences integrated in this tumor, a genome-length 8-kb DNA molecule and two rearranged 9- and 3.8-kb molecules. The VX7 8-kb DNA displays only a few differences in its restriction map, when compared to the wild-type (wt) CRPV DNA. The VX7 9- and 3.8-kb DNAs derive from the VX7 8-kb DNA since they share the same restriction site polymorphism. The VX7 9-kb DNA contains a duplication of the E6 open reading frame. The VX7 3.8-kb DNA results from the deletion of most of the E region and the insertion, between the borders of the deletion, of 174-nucleotide-long segment of the long control region potentially driving the expression of a truncated L2 protein. Both VX7 9- and 3.8-kb species potentially allow the expression of abnormal E6 fusion proteins. Nineteen point mutations were detected in the 3.8-kb DNA, compared to the wt CRPV DNA. None of these molecules were able to induce warts in domestic rabbits, in contrast to wt CRPV DNA. Furthermore, when cloned VX7 DNAs were inoculated together with wt CRPV DNA, none of the VX7 CRPV sequences, as identifiable by their specific restriction enzyme cleavage patterns, could be detected in the resulting warts. This suggests that CRPV sequences integrated in the VX7 carcinoma are no longer able to replicate as episomes, which might be a prerequisite for the production of warts.

A novel spontaneous mutation of the bovine papillomavirus-1 genome

A cell clone (cl.2) having an atypical transformed morphology was isolated from a murine C127 cell culture experimentally infected with a bovine papillomavirus type 1 (BPV-1) virion preparation. cl.2 cells exhibited minimal transformed characteristics and contained multiple copies of a BPV-1 plasmid with a molecular size slightly less than that of the wild type viral genome. A simple deletion of 277 bp was mapped to the distal portion of the viral 69% transforming fragment where the early gene region merges with the late gene region. None of the recognized early open reading frames were affected by the deletion but sequences including the common early gene mRNA polyadenylation (poly(A] signal and several base pairs of the "distal" enhancer element were deleted. Transfection of C127 cultures with low molecular weight (Hirt) DNA prepared from cl.2 cells led to the appearance of transformed cell foci, and Southern blotting analysis of a cl.2 Hirt DNA-transformed cell line confirmed that the deletion did not destroy the ability to replicate as a high copy plasmid. Removal of the natural early poly(A) signal did not obligate use of the alternative natural viral poly(A) signal located towards the end of the late region. Instead, a new major early mRNA polyadenylation site was mapped close to the unique BamHI recognition sequence at the distal end of the transforming region. Our results underline previous observations that there is a block to the production of stable mRNAs from the late gene region in BPV-1-transformed C127 cells, yet this is not necessarily explained by premature termination of transcription within this region.

Identification of proteins encoded by the L1 and L2 open reading frames of human papillomavirus 1a

The human papillomavirus 1 (HPV-1) virion is composed of two virally encoded proteins: a 57,000-molecular-weight polypeptide (57K polypeptide), which is the product of the L1 open reading frame (ORF), and a 78K polypeptide, which is derived from the L2 ORF. The 57K (L1) product, which represents the major structural component, appears to be disulfide cross-linked in virus particles. The 78K (L2) protein is a minor component of the virion and does not appear to be disulfide linked either to the L1 gene product or to itself. Analysis of virus particles banding at different buoyant densities revealed differences in the L2 content of heavy-full and light-full virions. Antiserum prepared against a bacterially expressed fragment of the L1 ORF was found by immunofluorescence to cross-react with HPV-2 and bovine papillomavirus 1 virions in wart sections. No cross-reactivity was observed with antisera prepared against either the N- or C-terminal halves of the L2-encoded protein. Similarly, antisera prepared against purified virus particles (disrupted and nondisrupted) reacted only with an expressed fragment of the L1 ORF and not with either L2-encoded polypeptides or proteins derived from the E1, E2, E4, E6, or E7 ORFs. This indicates that the L1 protein contains the papillomavirus common antigens.

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.

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.

Genital warts and cervical cancer. III. Subclinical papillomaviral infection and cervical neoplasia are linked by a spectrum of continuous morphologic and biologic change

Human papillomaviral (HPV) infection is now widely advanced as an important etiologic factor in cervical cancer. This study was undertaken to clarify morphologic relationships within the biologic spectrum linking subclinical papillomaviral infection (SPI) to cervical intraepithelial (CIN). Two pathologists analyzed 72 colposcopic biopsies, using a semi-objective rating scheme that scored 24 different histologic criteria. Each individual criterion was checked for reproducibility, and validated against an objective measure of papillomaviral infection (immunoperoxidase staining) or premalignant change (microspectrophotometry). The individual criteria were then combined into histologic indices of benign warty change, presumed viral atypia, abnormal cell phenotype, and disturbed tissue maturation. Histologic expression of papillomaviral infection decreased with increasing degrees of premalignant change. Plotting the index of abnormal cell phenotype against that of disturbed tissue maturation produced a linear plot in which cases clustered into four diagnostic groups. The histologic indices of papillomaviral infection displayed significant curvilinear correlations with genotypic distortion, benign warty change being maximal in the CIN 1 range and presumed viral atypia in the CIN 2 range. Disturbance of nuclear DNA content also increased with worsening diagnosis; diploidy being most common in SPI (67%), polyploidy in CIN 1 (59%), and aneuploidy in CIN 2 (65%) and CIN 3 (82%). Conversely, capsid antigen production decreased from 36% in SPI to 9% in CIN 3. Three aneuploid epithelia were immunoperoxidase positive. These inverse relationships between late viral expression and nuclear distortion fit experimental models of viral oncogenesis. The gradual transition and morphologic overlap between diagnostic groups support the postulate that SPI and CIN are a single disease spectrum, in which differences are those of degree rather than of kind.

Integration and methylation of shope papilloma virus DNA in the transplantable Vx2 and Vx7 rabbit carcinomas

The Shope papilloma virus (SPV) DNA present in SPV-induced benign and malignant rabbit tumors, particularly in the transplantable carcinoma Vx2 and Vx7, was examined with regard to physical states and extent of methylation. Vx2 and Vx7 carcinomas contained 10-22 viral genomes per diploid cell, and domestic and cottontail rabbit papillomas 40-400 and 1000-8000, respectively. The digestion of Vx2 and Vx7 DNA with the restriction enzyme KpnI, which does not cleave SPV DNA, yielded a single virus-specific DNA band about nine times larger than the genome length, but EcoRI, which cuts the circular SPV DNA once, cleaved this DNA to the genome-size fragments. However, three or four weak bands which may contain viral segments linked to cellular sequences were also identified, and at least two were shared by both Vx2 and Vx7 carcinomas. The analysis with a set of MspI and HpaII, which discriminates the methylated DNA sequence -CC*GG-, showed that 10-40% of the sites of viral DNA are methylated in papillomas, 30-80% in primary carcinomas, and more than 90% in the transplantable carcinomas.

Genital warts and cervical cancer. II. Is human papillomavirus infection the trigger to cervical carcinogenesis?

Evidence of a biologically significant association between subclinical papillomavirus infection (SPI) and cervical neoplasia raises the question of whether this is a causal relationship. Human papillomavirus (HPV) infection of metaplastic epithelium in the cervical transformation zone is relatively common, producing latent infection in susceptible persons. The epidemiological characteristics of SPI and cervical cancer are essentially identical and there is a strong clinico-pathological association between condylomas and anogenital carcinoma. Tissue culture cells have been transformed from a normal to a neoplastic phenotype by animal papillomaviruses, and there is preliminary data reporting upon the successful identification of HPV genomic sequences in tumor cells. SPI commonly coexists with foci of cervical intraepithelial neoplasia (CIN). Areas of apparent transition are seen, and these two lesions are linked by a discernible spectrum of morphologic change. Such circumstantial evidence gives biological plausibility to the suggestion that HPV may be a cervical carcinogen. It is postulated that cervical neoplasia arises by progression from benign viral hyperplasia, through varying stages of koilocytotic atypia with associated dysplasia, to unremarkable carcinoma in situ. Invasion is presumed to reflect the emergence of an aggressive heteroploid clone, an age-related decline in host immune surveillance or an interaction of both factors.

Free cottontail rabbit papillomavirus DNA persists in warts and carcinomas of infected rabbits and in cells in culture transformed with virus or viral DNA

We have compared warts and carcinomas from cottontail and domestic rabbits for the presence of cottontail rabbit papillomavirus (CRPV) and the status of the viral DNA genome. Our studies indicate that benign warts from cottontail rabbits, whether found naturally or induced in the laboratory, contain large amounts of virus and on the average 1000 copies of the virus genome per cell. Both benign warts and carcinomas from domestic rabbits contain significantly reduced levels of virus relative to cottontail rabbit warts and an average of 100 copies of the virus genome per cell. A single sample of a naturally occurring cottontail rabbit carcinoma contained approximately 80 copies of the viral genome per cell. None of the tumors that we have analyzed thus far appear to have integrated viral genomes by Southern blot analysis of undigested and restriction endonuclease-digested DNA samples. Furthermore, the CRPV genome present in domestic rabbit carcinomas and a cottontail rabbit carcinoma appears identical by restriction endonuclease mapping to that present in papillomas of cottontail and domestic rabbits indicating that no major deletions or rearrangements of the CRPV genome had occurred during the progression of benign to malignant tumors nor was a variant of wild-type CRPV responsible for this phenomenon. Finally, we have demonstrated morphological transformation in vitro of NIH 3T3 and C127 cells upon infection with purified CRPV and upon transfection with purified CRPV DNA. Furthermore, single cell clones derived from transformed foci contain free forms of CRPV DNA that persist through continued passage in culture. Cells transformed by CRPV grow in soft agar in vitro and produce tumors in athymic nude mice.

Hepatitis B virus antigens in liver tissue in hepatocellular carcinoma and advanced chronic liver disease-relationship to liver cell dysplasia

Hepatitis B surface (HBs) and core (HBc) antigens (Ag) were studied in liver tissue in HBsAg seropositive patients with chronic liver disease complicated (n = 32) and not complicated (n = 36) by hepatocellular carcinoma. Both groups were matched by age, sex and underlying disease. There was no qualitative and quantitative difference in tissue HBsAg between the two groups. However, HBcAg was significantly less in quantity in hepatocytes of patients with hepatocellular carcinoma compared to chronic liver disease without cancer. Serum hepatitis B e antigen tested by radioimmunoassay was also less frequently positive in patients with hepatocellular carcinoma. These findings seem to suggest that hepatitis B virus replication becomes less active in the process of hepatocarcinogenesis. The relationship between intrahepatic hepatitis B antigens and liver cell dysplasia was also studied. In hepatocellular carcinoma, tissue hepatitis B antigens often coexisted in the same liver having liver cell dysplasia, but no such association was observed in chronic liver disease without cancer. However, no indication was obtained that the dysplastic cells harbor HBsAg more frequently than non-dysplastic cells.

Focal epithelial hyperplasia in rabbit oral mucosa

Several papules on the floor of the mouth and the ventral surface of the tongue of a zinc-deficient rabbit were studied by light and electron microscopy. These papules appeared to be consistent with focal epithelial hyperplasia of man and chimpanzees. There was a concurrence of cytoplasmic vacuolization with the appearance of viral particles within the nucleus. Intranuclear crystalline viral aggregates were frequently observed in the upper spinous cells.

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.

Clinical, histological and ultrastructural features of a possibly virus-induced oral leukoplakia

Two male patients with oral leukoplakias exhibiting a peculiar type of apparent dysplastic changes have been followed for 4 and 6 years, and a series of biopsies have been examined by light and electron microscopy. The apparent lack of normal epithelial stratification below the keratinized cell layers was mainly caused by the frequent appearance of large ballooned cells and multinuclear giant cells. The centre of the large ballooned cells contained aggregations of chromatin and evenly-dispersed microtubulus surrounded by a thick rim of tonofibril bundles. In the peripheral cytoplasm large numbers of smooth-surfaced endoplasmic reticulum were found, but no Golgi apparatus was observed. In addition, several autophagocytic bodies were recorded. Along the cell membrane only a few desmosomes were present, whereas aggregations of digested desmosomes were found in the cytoplasm. On the basis of the ultrastructural findings, it is suggested that the large ballooned cells represented epithelial cells arrested in early stages of mitotic division. The epithelial cells in interphase exhibited a normal ultrastructure except for large nucleoli with varying degrees of condensation of nucleolonema and vacuolization. Further, atypical dense granular aggregations and strands of fine fibrillar material were recorded in the nuclei. It is suggested that this new type of oral leukoplakia has a viral etiology.

Focal epithelial hyperplasia in a group of South Africans: Its ultrastructural features

Electron microscopic observation of samples of tissues from lesions diagnosed as focal epithelial hyperplasia revealed the presence of viral particles in six (possibly seven) of 13 cases examined. Viral particles were intranuclear and varied from sparsely scattered to densely packed. A crystalline arrangement was present in one case. The chromatin of affected cells was typically condensed into clumps and thick bands, and the nuclear membrane was usually absent in pronounced cases. The nuclei of the basal and prickle cells were frequently indented and the chromatin peripherally condensed. Numbers of lysosomal-like organelles were observed in many of these cells. The ballooning epithelial cells with their mitosis-like aberrations observed with light microscopy consisted of a rim of tonofilaments and organelles and a homogeneous granular center interspersed with dense areas. It is suggested that the nuclear characteristics and numerous lysosomes observed in basal and prickle cells are cellular changes induced by the viral infection and that the mitosis-like aberrations represent a bizarre and arrested form of mitosis.

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.

Expression of Epstein-Barr viral capsid, complement fixing, and nuclear antigens in stationary and exponential phase cultures

Three continuous lymphoblastoid cell lines, 2 productive of nucleocapsids and 1 nonproductive line, were studied for their content of Epstein-Barr viral (EBV) antigens during transition from stationary to logarithmic phase growth. As a preliminary step, viable cells were separated from degenerating ones in discontinuous gradients of serum albumin. Viral capsid antigens were found in both living and dead cells of the 2 producer lines; however, complement fixing (CF) antigens and nuclear antigen were detected only in viable cell subpopulations. The content of antigen detectable in extracts of viable cells by complement fixation remained constant in replicating and resting cultures; further, all viable cells of the 3 lines demonstrated intranuclear antigen by anticomplement immunofluorescence in all stages of growth. In contrast, the proportion of cells with viral capsid antigen in the producer lines increased 7- to 24-fold following entry of resting populations into the phase of exponential growth.The results suggest that expression of viral capsid antigens is discontinuous and is initiated in response to events in log phase, possibly DNA synthesis or mitosis. Expression of the complement fixing and nuclear antigens in continuous in viable cells. These findings emphasize the intimate relationship of the CF and nuclear antigen to the transformed state and suggest that study of this antigen complex will shed light on the mechanisms of lymphocyte transformation by EBV.

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

The occurrence and localization of vegetative viral DNA replication was studied in sections of tumors induced by the rabbit Shope papilloma virus, in cottontail and domestic rabbit papillomas, in primary domestic rabbit carcinoma, and in transplantable VX2 carcinoma, by in situ hybridization of radioactive RNA complementary to viral DNA. Vegetative viral DNA replication and viral protein synthesis were compared by means of cytological hybridization and immunofluorescence techniques on adjacent frozen sections. Vegetative viral DNA replication is completely repressed in the proliferating cellular layers of these tumors, which suggests a provirus state of the viral genome, as in other cells transformed by oncogenic DNA viruses. Vegetative viral DNA replication is induced, after initiation of the keratinization, in cells of cottonail rabbit papillomas, where it is usually followed by viral protein synthesis; this illustrates the influence of the physiological state of the host cell on the control of viral functions. Vegetative viral DNA replication is deteced only in a few cells of domestic rabbit papillomas, at the end of the keratinization process; this observation provides indirect evidence that the DNA synthesis specifically induced in these tumors after the onset of keratinization reflects mostly the induction of cellular DNA synthesis.

The detection of a viral interfering substance in the Shope papilloma and the Vx7 and Vx2 carcinomas

In vivo assay of Shope papilloma protein extract and in vitro assay of extracts from Shope papilloma, Vx7 and Vx2 carcinomas showed strong interferon-like activity in the papilloma and moderate activity in the carcinomas. The interpretation is that the presence of viral nucleic acid in all three tumors stimulated the production of this substance even though fluorescent antibody studies reveal the protein coat only in the papilloma and Vx7.

Papova virus group

The papilloma, polyoma, and vacuolating agents seem to form a natural group of tumor viruses, for which the name papova virus group is proposed. Members of the group have the following properties: 45 mmicro diameter, deoxyribonucleic acid core, 42 capsomeres, absence of essential lipids, thermal resistance, slow growth cycle with multiplication within the cell nucleus, and tumorigenicity.