Immune stimulation for the treatment of papilloma

OBJECTIVES

There is no curative therapy for recurrent respiratory papillomatosis. Unmethylated dinucleotides of cytosine and guanine (CpG) are potent immune stimulants that have shown efficacy against tumors as monotherapy, as vaccine adjuvants, and in combination with chemotherapies. We examined the therapeutic effect of CpG oligodeoxynucleotides in the treatment of papillomavirus in a cottontail rabbit model (CRPV).

METHODS

Twenty rabbits were infected with CRPV; 10 were treated with 11 weekly CpG inoculations while treatment control rabbits received intralesional saline solution. Eight rabbits (4 treatment, 4 control) were rechallenged with CRPV 17 weeks after the initial viral challenge and monitored for new papilloma development.

RESULTS

Papillomas developed in all 20 rabbits (100%) within 4 weeks of infection. The diagnosis was confirmed histologically. There was no difference in the average tumor burden between the treatment and control groups after 11 weeks of CpG treatments or after 9 additional weeks of observation. There was no difference between the groups in papilloma size at the site of the injections, nor was there eradication of papillomas at remote sites in either group. No new papillomas developed in any of the 8 animals that were rechallenged.

CONCLUSIONS

We have reproduced an effective mammalian papilloma model for preclinical immunotherapeutic testing. Despite the potency of CpG in triggering host immunity, CpG oligodeoxynucleotide did not show a therapeutic effect against the large papilloma burdens tested in this study. The lack of effect suggests that either enhanced papilloma antigen presentation or targeting of immune-evasive mechanisms used by the papillomas is needed to treat bulky disease with an immunotherapeutic strategy.

Joint action of a chemical carcinogen and a neoplastic virus to induce cancer in rabbits; results of exposing epidermal cells to a carcinogenic hydrocarbon at time of infection with the Shope papilloma virus

Areas of rabbit skin previously rendered hyperplastic with turpentine were scarified, inoculated with the Shope papilloma virus, and covered with a dressing that contained 20-methylcholanthrene (MC) or 9:10-dimethyl-1:2-benzanthracene (9:10). The dressing was left on until healing had been well completed, a matter of 5 to 7 days. The papillomas which subsequently arose often appeared later, were fewer, and remained less vigorous than those due to the action of virus alone, but throughout several months they appeared to differ from these in no other ways. Then, more or less abruptly, the large majority became carcinomatous, frequently at several situations, whereas with few exceptions the control growths underwent no such alteration. The cancers were of the sorts ordinarily deriving, by secondary change, from epidermal cells infected with the virus. Collateral data have made plain that the hydrocarbons acted in their carcinogenic capacity to bring on the cancers. Indeed in control tests 9: 10 sometimes conferred latent neoplastic potentialities on uninoculated epidermis exposed to it while healing after scarification, a fact disclosed months later by painting these expanses with chloroform until hyperplasia occurred. Under the promoting influence of this agent papillomas formed which had the distinctive morphology of those induced by the chemical carcinogens. So strong and enduring were the effects of MC and 9:10 as to cause cancers to arise from many virus papillomas which were retrogressing after months of proliferation, that is to say under circumstances ordinarily unfavorable to malignant change. The facts justify the conclusion that the virus and the hydrocarbons acted jointly and in their carcinogenic capacities.

Reinitiated expression of EJras transgene in targeted epidermal cells of transgenic rabbits by cottontail rabbit papillomavirus infection

Transgenic rabbits carrying the EJras oncogene have been established in our laboratory (Am. J. Pathol. 155 (1999) 315). The expression of the ras gene is targeted to the epidermal keratinocytes using the upstream regulatory region (URR) of the cottontail rabbit papillomavirus (CRPV). All of the transgenic rabbits develop keratoacanthomas at multiple sites in the skin at 2-3 days after birth, and the tumors spontaneously regress in 1.5-2 months. With regression of the keratoacanthomas, the rabbits appear normal and EJras expression is undetectable in their skin. To determine if CRPV infection would reinitiate the expression of the EJras transgene and make the rabbits more sensitive to tumorigenesis, the rabbits were infected with CRPV at 2 months of age when the keratoacanthomas had regressed. This study shows that CRPV infection of the transgenic rabbit skin could shorten the latency required for CRPV papilloma initiation, and significantly increase the tumor growth and persistence rate compared with non-transgenic rabbits. Furthermore, EJras expression became detectable in the CRPV induced papillomas in transgenic rabbits, but not in the papillomas of non-transgenic rabbits. These results indicate that CRPV infection is able to reinitiate the expression of the CRPV URR controlled EJras oncogene carried by the transgenic rabbits and that the expression of EJras can enhance the tumorigenesis of CRPV infection.

Tests of Buffergel for contraception and prevention of sexually transmitted diseases in animal models

BACKGROUND

BufferGel is a novel spermicidal and microbicidal gel formulated to maintain the natural protective acidity of the vagina by acidifying semen, which otherwise alkalinizes the vagina.

GOAL

To test the efficacy of BufferGel for preventing sexually transmitted infections and pregnancy in animal models.

STUDY DESIGN

Animals were challenged with pathogens or sperm after pretreatment with both test and control agents, or after no pretreatment, then evaluated for infection or pregnancy using standard methods.

RESULTS

BufferGel provided significant contraceptive efficacy in the rabbit, and significant protection against vaginal and rectal transmission of herpes simplex virus type 2 (HSV-2) in the mouse, vaginal transmission of Chlamydia trachomatis in the mouse, and skin transmission of cottontail rabbit papillomavirus in the rabbit. It did not protect against vaginal transmission of Neisseria gonorrhoeae in the mouse.

CONCLUSIONS

The protective efficacy of BufferGel in five of the six animal models suggests that this microbicide warrants clinical evaluation for both contraception and disease prevention.

Combination treatment with intralesional cidofovir and viral-DNA vaccination cures large cottontail rabbit papillomavirus-induced papillomas and reduces recurrences

We used the cottontail rabbit papillomavirus (CRPV) New Zealand White rabbit model to test a combination treatment of large established papillomas with intralesional cidofovir and DNA vaccination to cure sites and reduce recurrences. Intralesional 1% (wt/vol) (0.036 M) cidofovir treatment of rabbit papillomas led to elimination, or "cure," of the papillomas over a 6- to 8-week treatment period (N. D. Christenson, M. D. Pickel, L. R. Budgeon, and J. W. Kreider, Antivir. Res. 48:131-142, 2000). However, recurrences at periods from 1 to 8 weeks after treatment cessation were observed at approximately 50% of cured sites. DNA vaccinations with CRPV E1, E2, E6, and E7 were initiated either after or at the time of intralesional treatments, and the recurrence rates were observed. When DNA vaccinations were started after intralesional cures, recurrence rates were similar to those of vector-vaccinated rabbits. A small proportion of recurrent sites subsequently regressed (4 out of 10, or 40%) in the vaccinated group versus no regression of recurrences in the vector-immunized group (0 out of 19, or 0%), indicating partial effectiveness. In contrast, when DNA vaccinations were conducted during intralesional treatments, a significant reduction of recurrences (from 10 out of 19, or 53%, of sites in vector-immunized rabbits to 3 out of 20, or 15%, of sites in viral-DNA-immunized rabbits) was observed. DNA vaccination without intralesional treatments had a minimal effect on preexisting papillomas. These data indicated that treatment with a combination of antiviral compounds and specific immune stimulation may lead to long-term cures of lesions without the ensuing problem of papilloma recurrence.

A recombinant vaccinia virus containing the papilloma E2 protein promotes tumor regression by stimulating macrophage antibody-dependent cytotoxicity

Human papillomavirus infection is associated with cervical cancer. The E6 and E7 papillomavirus proteins are normally required for the maintenance of the malignant phenotype. Expression of these proteins in infected cells is negatively regulated by the binding of the papilloma E2 protein to the long terminal control region of the papilloma virus genome. The E2 protein can also promote cell arrest and apoptosis in HeLa cells. Therefore, it is clear that this protein has the potential of inhibiting the malignant phenotype. Because, anticancer vaccines based in vaccinia viruses have recently been shown to be an effective way to treat and to eradicate tumors, a recombinant vaccinia virus expressing the E2 gene of bovine papilloma virus (Modified Vaccinia Ankara, MVA E2) was created, to explore further the antitumor potential of the E2 protein. A series of rabbits, containing the VX2 transplantable papilloma carcinoma, were treated with MVA E2. An impressive tumor regression, up to a complete disappearance of tumor, was observed in most animals (80%). In contrast, very little or no regression was detected if the normal vaccinia virus was used. Lymphocytes isolated from MVA E2-treated rabbits did not show cytotoxic activity against tumor cells. However, in these animals a humoral immune response against tumor cells was observed. These antitumor antibodies were capable of activating macrophages to destroy tumor cells efficiently. These data indicate that injecting the MVA E2 recombinant vaccinia virus directly into the tumor results in a robust and long-lasting tumor regression. Data also suggest that antitumor antibodies are responsible, at least in part, for eliminating tumors by activating macrophage antibody-dependent cytotoxicity.

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.

The inhibitory effects of bryostatin 1 administration on the growth of rabbit papillomas

Bryostatin 1 is a protein kinase C modulator that shows antineoplastic activity in a variety of tumor systems. This study examined the effects of bryostatin 1 administration on papilloma growth in rabbits. Investigations of optimal route, dose, and schedule were performed. Several groups of rabbits were inoculated with cottontail rabbit papillomavirus (CRPV) DNA. Bryostatin 1 was administered i.v., both daily and weekly, and intralesionally both weekly and bi-weekly. Intralesionally dosed papillomas were examined histologically for immune cell infiltration. In weekly and daily i.v. trials, 2.5 and 1.0 microg/kg, respectively, showed the greatest overall reduction in tumor size. Bryostatin 1 administered intralesionally also slowed papilloma growth. Treated lesions had significantly higher numbers of heterophils and eosinophils.

Therapeutic evaluation of compounds in the SCID-RA papillomavirus model

A previous study by Kreider (Kreider et al., 1979) indicated that rabbit skin, which had been transplanted to immunodeficient nude mice, could be successfully infected with cottontail rabbit papillomavirus (CRPV). We have extended this observation in developing a rodent model for evaluation of compounds for activity against the papillomaviruses. In this model (called the SCID-Ra model), rabbit ear skin is transplanted to the dorsum of SCID mice and allowed to heal for 3 weeks. Infection with CRPV by scarification leads to the growth of warty lesions within 2 3 weeks in >95% of the animals. Topical and/or systemic therapy can be initiated at various times post infection (PI). Weekly lesion scores are recorded and compounds are evaluated for their ability to suppress wart growth when compared to untreated control mice. Ribavirin, which has had a suppressive effect both in the clinic for the treatment of respiratory papillomatosis and on the growth of warts in the rabbit back model, was evaluated and showed significant anti-proliferative activity with oral dosing. Both antiviral and antiproliferative compounds including podophyllin and 5-fluorouracil, which have been used clinically for the treatment of human papillomavirus (HPV) infections, were evaluated in this model. The anti-mitotic compound, Navelbine (vinorelbine tartrate), which is used for the treatment of non-small cell lung carcinoma was evaluated in this system and showed significant inhibition of wart growth with somewhat less topical cytotoxicity when compared to podophyllotoxin.

Studies of the mechanism of action of the Shope rabbit papilloma virus. I. Concerning the nature of the induction of arginase in the infected cells

These studies make plain that the Shope papilloma virus induces the production of an arginase in rabbit squamous epithelium, and provide evidence that the information for the synthesis of the enzyme is derived from the virus rather than the rabbit. This form of induction is therefore different from that brought about by chemicals such as galactosides (36). Striking differences were shown between the physiochemical properties of Shope virus-induced arginase and other arginases of domestic and Kansas cottontail rabbits. The absence of a requirement for manganese suggests the mechanism of splitting off urea from arginine by papilloma arginase probably differs from that of previously described arginases. These findings (particularly the experiments in which it was demonstrated that papilloma growth could be greatly reduced by giving animals supplemental arginine in the presence of small amounts of the arginase inhibitor, canavanine) provide evidence that suggests the following mechanism of action for the virus: viral DNA introduces into rabbit epithelium the information for the synthesis of an arginase for which the cells have no control mechanism. The arginase depletes cellular arginine and, in turn, the synthesis of arginine-rich nuclear histones (2), thereby freeing the nucleus for greater synthetic activity (4, 35), which results in more rapid growth of the papilloma cells. Domestic rabbit papillomas induced with purified virus derived from wild rabbit papillomas were shown to contain an antigen which reacts immunologically like a wild rabbit antigen. It was distinct from the arginase, the protein coat of the virus, and the Vx-2 antigen. The presence of the wild rabbit antigen seems indicative of integration of the virus DNA in the host genome of the wild rabbit. Other incidental findings include the description of a simple method, accurate to within 1 per cent, for determining the partial specific volume of a protein, and the description of a modification of the Richards and Schachman method (9) enabling the determination of the molecular weight and homogeneity of a protein with as little as 0.25 mg and with an accuracy of 2 per cent.

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.

A simplified 'coupled' probing approach for the detection of proteins on dot and western blots

Western blotting is one of the most commonly and widely used methods for identifying the presence of an antigen in biochemical studies. The present study describes a novel 'coupled blotting' approach that allows antigen on dot and Western blots to be simultaneously probed with primary and secondary probing reagents. The study utilized the highly sensitive enhanced chemiluminescence (ECL) detection system, purified E7 protein of cottontail rabbit papillomavirus (CRPV) and E7-specific antibodies. Comparison of the abilities of sequential primary antibody followed by secondary reagent and coupled treatments to detect E7 protein on blots showed no reduction in signal strength after coupled probing. The new 'coupled' probing has the advantage of saving hands-on time and buffer solutions over the standard procedure. Overall, the results suggest that the 'coupled blotting' is useful for the rapid detection of proteins without compromising quality.

Association of tumor necrosis factor-alpha gene expression and apoptotic cell death with regression of Shope papillomas

The objective of this study was to test the hypothesis that spontaneous regression of Shope papillomas involves tumor necrosis factor-alpha and apoptotic cell death of the papilloma cells. In situ hybridization using RNA probes of rabbit tumor necrosis factor-alpha revealed tumor necrosis factor-alpha mRNA in most of the numerous mononuclear cells infiltrating the upper dermis of regressing papillomas and at the dermoepidermal junction. Such cells in progressing papillomas were much fewer in number and were located in the deeper dermis. In situ terminal deoxynucleotidyl transferase assay demonstrated DNA strand breaks in many scattered epidermal keratinocytes of regressing papillomas but in only a few thin layers just beneath the horny layer in progressing papillomas. Electron microscopy demonstrated that regressing papillomas contained many apoptotic bodies and keratinocytes showing apoptotic changes such as chromatin condensation, degradation of condensed nuclei, surface protuberances, and a filamentous degeneration, as well as infiltrating lymphocytes and macrophages. We propose that tumor necrosis factor-alpha produced by infiltrating mononuclear cells probably plays a role in the papilloma regression.

Perilesional Interleukin-2 in the VX-2 Carcinoma in Rabbits: A Preliminary Investigation

Immune system amplification by perilesional injection of interleukin-2 is a promising adjuvant approach for treating squamous cell carcinoma of the head and neck. A pilot study was designed to develop an animal model bearing squamous cell carcinoma in which to test the efficacy of perilesional interleukin-2. Rabbits were inoculated intramuscularly with the papilloma virus-induced squamous carcinoma VX-2 cell line. Tumor regression and host lymphatic response after perilesional interleukin-2 were measured. Variable responses were found. Growth of tumor cells implanted from cell culture was rapid in most animals. Tumor growth was prevented in animals receiving 10,000 units of interleukin-2 per injection initiated 9 days after tumor inoculation. This inhibition approached statistical significance when compared with growth of saline controls. Histologic responses consisted primarily of plasma cell and eosinophil infiltration. The intensity of the inflammatory response did not correlate with interleukin-2 dose. A trend toward enhanced tumor growth was seen with lower doses of interleukin-2 and when inferleukin-2 therapy was initiated simultaneously with tumor inoculation. These findings suggest that high-dose recombinant interleukin-2 can prevent tumor growth if initiated after tumor inoculation. Whether this effect was caused by direct tumor cytotoxicity or mediated by the immune system is unclear. These preliminary results underscore the importance of understanding the effects of dose and schedule in the design of immunotherapy models before Clinical use.

Variable-region sequences for T-cell receptor-gamma and -delta chains of rabbit killer cell lines against Shope carcinoma cells

A rabbit gamma delta killer T-cell line against Shope carcinoma cells was established from peripheral blood lymphocytes (PBL) of a human T-lymphotropic virus type I (HTLV-I)-infected rabbit bearing Shope papilloma and carcinoma. Southern hybridization analysis of this cell line with an HTLV-I probe showed that the cell line contained multiple clones of HTLV-I-transformed cells, and three sublines with different integration patterns of the HTLV-1 genome were isolated by cloning of the cell line. In all these sublines T-cell receptor (TCR)-gamma and -delta genes were rearranged and expressed. A PCR-based analysis of the expression of variable (V) genes showed that the killer cell line preferentially expressed V gamma 1.1 and V delta 1 genes, whereas V gamma 2 and V delta 1 genes were dominantly expressed in normal PBL. Analysis of the junctional sequences of TCR-gamma and -delta genes which dictate the fine specificities of epitope recognition revealed that all three sublines expressed V gamma 1.1/V delta 1 genes without the nucleotide diversity at the V-J junctions.

Photodynamic therapy using m-tetra(hydroxyphenyl) chlorin. An animal model

OBJECTIVE

To evaluate the potent photosensitizer m-tetra (hydroxyphenyl) chlorin (m-THPC) by using rabbits with cottontail rabbit papillomavirus-induced tumors and the canine larynx as model systems.

DESIGN

Nonrandomized control trial.

SETTING

Division of ear, nose, and throat research at a tertiary care teaching hospital.

MATERIALS

Rabbits were used for relative retention ratio studies and tissue tolerance tests. Studies on the swelling of normal tissues in the larynx after photoactivation were done with canines.

INTERVENTION

Animals were injected with 0.3 mg/kg of m-THPC. At varying intervals, tissues were exposed to 652 nm of light.

OUTCOME MEASURES

Outcome measures consisted of four elements: (1) decay of plasma concentration over time, (2) interval to and duration of maximal ratio between drug concentration in normal tissue and tumor, (3) maximal permissible light exposure to normal tissue (skin and laryngeal mucosa) at an optimal interval, and (4) efficacy--number of tumors with partial and complete response.

RESULTS

The largest papilloma to skin ratio (10:1) occurred 4 to 8 days after drug injection. The rabbit skin damage threshold was 40 to 60 J/cm2 at 6 days. The canine laryngeal edema and erythema thresholds were 50 to 70 J. A 75% cure rate of papillomas was achieved with tumors that were less than 100 mm2 in area at light doses that ranged from 25 to 75 J/cm2.

CONCLUSIONS

m-THPC shows efficacy in treating papilloma virus-induced tumors. We present a protocol for rapid optimization of the factors required for tumor destruction with minimal normal tissue damage, thus permitting determination of an optimal therapeutic protocol for any photosensitizer.

Monoclonal antibody E6G6 recognizes glycolipids as a differentiation antigen in Shope carcinoma cells

Monoclonal antibody E6G6 preferentially reacted with well differentiated and non-tumorigenic Shope carcinoma cell lines but hardly reacted with undifferentiated and tumorigenic lines as determined by enzyme-linked immunosorbent assay, cytofluorometry and the complement dependent cytotoxicity test. Immunohistochemical analysis of the primary carcinoma tissue revealed that the antibody intensely stained keratinizing carcinoma cells with marked shrinkage whereas it did not stain normal epidermal keratinizing rabbit cells or benign tumor (Shope papilloma) cells, suggesting that the antigen expression in vivo was closely correlated with terminal differentiation of the carcinoma cells. Thin layer chromatography immunostaining revealed that the antigen was comprised of several neutral glycolipids and that differentiated cells contained about ten times more antigen than undifferentiated cells.

Topical CTC-96 accelerates wart growth in rabbits infected with cottontail rabbit papillomavirus

CTC-96, a cobalt containing complex, was tested as a putative topical therapeutic agent for the treatment of papillomavirus-induced tumors in our cottontail rabbit papillomavirus (CRPV)-rabbit model system. Following experimental infection of domestic rabbits with CRPV, CTC-96 was applied to infection sites twice daily, 5 days a week for a total of 8 weeks. Two levels of concentrations of aqueous CTC-96 were compared to placebo control-treated animals. With increasing dose of CTC-96 we observed tumors earlier, larger, and more often across eight infected sites on each animal.

Podofilox-induced regression of Shope papillomas may be independent of host immunity

We tested the hypothesis that infiltrating leukocytes might contribute to papilloma destruction following podofilox treatment. New Zealand White (NZW) rabbits were inoculated with cottontail rabbit papillomavirus (CRPV) onto abraded areas of the dorsal skin. At 21 d after viral inoculation, 5.0% podofilox solution was applied to some papillomas, whereas others were used as controls. Three rabbits were sacrificed at each of three different periods after treatment initiation (1, 4, and 7 d). Four monoclonal antibodies (MoAbs), RG-16 (for B cells), L11/135 (specific for T cells), 2C4 (specific for class II antigen), and Ki67 (specific for proliferating cells), were used in an immunohistochemical study. All positive cells and total cells in the field were counted with an ocular grid. After 1 d of treatment, proliferation of papilloma cells was strongly suppressed in treated papillomas, but leukocytic infiltration was not altered. At 4 d and 7 d of treatment, there were substantial increases (about two to three times) in the numbers of B and T cells and class II-expressing leukocytes. The upper layers of the papillomas were highly necrotic and cell proliferation was absent in all layers. These data support the view that podofilox has a direct toxic effect on papilloma tissue. Leukocyte infiltration is not strongly associated with papilloma tissue and may not contribute to papilloma destruction.

Morphometric analysis and identification of infiltrating leucocytes in regressing and progressing Shope rabbit papillomas

Spontaneous regressions of papillomavirus lesions frequently occur in both human and animal infections. The mechanism by which this occurs is currently unknown. Mononuclear infiltrates are found in regressing human and rabbit papillomas. To assess the potential functional role of these infiltrates in regression, we have characterized and quantitated the cell types present in regressing rabbit lesions. Forty New Zealand white rabbits were inoculated with cottontail rabbit papillomavirus (CRPV) at 2 sites on the dorsal skin. All tumors on 6 rabbits markedly decreased in volume within 6 to 8 weeks of inoculation. Tumors on 4 of these 6 regressor rabbits were studied by immunohistochemistry. Regressor papillomas had conspicuous leucocytic infiltrates, most concentrated at the epithelial basement membrane, and often obliterating the basal cells of the germinal layer. Infiltrating leucocytes were also concentrated in the subjacent dermis immediately beneath the basement membrane. The infiltrates gradually lessened at increased depths in the dermis. In contrast, progressor papillomas contained fewer leucocytes, which were randomly distributed in the dermis. The phenotype of the infiltrating leucocytes was examined in 4 regressing and 12 progressing papillomas. In regressing papillomas, infiltrating leucocytes were predominantly T cells (68.0%), with relatively few B cells (7.4%). Progressing papilloma dermis contained fewer T cells and B cells than regressing papillomas. Most of the infiltrating T cells in regressing papillomas were labelled with a rabbit MHC-class-II-specific monoclonal antibody (MAb) (2C4), in contrast to only a small number in progressing papillomas. In addition to the leucocytic infiltrates, keratinocytes in regressing, but not in progressing, papillomas, frequently exhibited strong 2C4 staining. These results demonstrate that infiltration with T cells expressing rabbit class II is characteristic of regressing Shope papillomas and strengthens the assertion that cell-mediated immunity is the mechanism of Shope papilloma regression.

Killer cell lines against Shope carcinoma cells in rabbits

Killer cell activity against Shope carcinoma cells was not detected in PBL nor in spleen cells from tumor-bearing B/J rabbits, but was induced by in vitro culture of these cells in the presence of IL-2 and X-irradiated carcinoma cells. HTLV-I-transformed killer cell lines were successfully obtained by the culturing of PBL from an HTLV-I-infected and tumor-bearing Chbb:HM rabbit. These killer cells included large cells with azurophilic granules in the cytoplasm and with a reniform nucleus, thus resembling large granular lymphocytes. The killer activity was similar against the Vx2K cell line from a random-bred rabbit and SCB cell lines from an B/J rabbit, suggesting the absence of MHC restriction.

High energy underwater shock wave treatment on implanted urinary bladder cancer in rabbits

The effects of focused high energy shock waves (SW) on the implanted urinary bladder cancer in rabbits were examined. The bladder cancer was exposed to 2000 to 8000 shots of focused SW under ultrasound guidance. Although only focal necrosis of the tumor was seen in the one day SW exposure, wider and deeper tumor necrosis was observed in the tumors following serial SW (2000 to 6000 shots, for two to three days). Eight to 10 day serial SW exposure (6000 to 8000 shots) decreased the tumor growth in comparison with that of the control. Lung metastases examined by periodic chest X-ray after SW treatment revealed that SW did not promote lung metastases. Pathological findings were also in accord with the X-ray examinations. Polyclonal antibody type 4 collagen was used for immunohistochemical staining of vascular wall in bladder cancer. Vascular wall destruction, not found in spontaneous necrotic tumor, were clearly visible in SW induced necrotic area. SW induces vascular damage in the tumor, which may be the primary cause promoting the tumor necrosis.

Suppression of interleukin-2 production and activity by factor(s) released by peripheral blood mononuclear cells during papillomavirus infections

Supernatant fluids from cultured peripheral blood mononuclear cells (PBMC) obtained from patients with extensive papillomavirus infections such as condyloma acuminatum (CA) and epidermodysplasia verruciformis (EV) depressed the proliferative responses of T cells to phytohemagglutinin-P (PHA-P) and the production of interleukin-2 (IL-2) from those preparations. Fluids from the same cultures also inhibited the mitogenic activity of IL-2 on CTLL-2 cells as IL-2-dependent target cells. These soluble suppressor factors (SSF) from PBMC were present in significantly higher concentrations in fluids from cultured PBMC from patients in comparison to healthy controls. A soluble suppressor factor was characterized also from cultured rabbit PBMC after the rabbits had been infected with Shope papillomaviruses. This suppressor factor likewise inhibited IL-2 production and IL-2 activity.

Effects of hyperthermia, radiotherapy and thermoradiotherapy on tumor microvascular permeability

Morphological changes in rabbit VX-2 tumor and its vascular permeability to ferritin following hyperthermia, radiotherapy and thermoradiotherapy were investigated by light and electron microscopy. Tumors treated by thermoradiotherapy successively showed a decrease in volume compared with those treated by hyperthermia or radiotherapy. Light microscopically, degenerative or necrotic changes progressed more widely in tumors treated by thermoradiotherapy than in those treated by hyperthermia or radiotherapy alone. When vascular permeability to ferritin was examined, an increase in tumor vascular permeability occurred at 1 day after hyperthermia or thermoradiotherapy, and at 3 days after radiotherapy. These results suggest that the early reaction of tumor microvasculature is a factor contributing to delayed cell death in tumors after thermoradiotherapy or hyperthermia.

Histological and molecular analysis of cottontail rabbit papillomavirus-induced papillomas treated with hematoporphyrin derivative photodynamic therapy

The clinical regression of cottontail rabbit papillomavirus-induced cutaneous papillomas on Dutch-belted rabbits following treatment with hematoporphyrin derivative photodynamic therapy was recently reported. Those papillomas that underwent total regression failed to recur at 18 months. Tissues from totally regressed papillomas and adjacent sites failed to reveal the presence of papilloma on histological examination. These findings were confirmed by the absence of viral DNA following analysis by Southern blots for cottontail rabbit papillomavirus viral copy number and DNA restriction pattern. Partially regressed papillomas and untreated papillomas revealed histologically typical papillary features with approximately equal amounts of viral DNA.

Hematoporphyrin derivative therapy of papillomas. Experimental study

Hematoporphyrin derivative has been shown to selectively localize in malignant tissues and chemically induced animal papillomas. It is a powerful photo-sensitizing agent that can cause destruction and death of tissues in which it has localized by the generation of singlet oxygen when activated by light of the appropriate wavelength (photodynamic therapy [PDT]). Laryngeal papillomas are rapidly growing benign epithelial neoplasms with a clinical course marked by multiple recurrences after surgical removal. Before considering PDT as a therapeutic modality in the treatment of this debilitating disease we developed an animal model for experimentation. Using the cottontail rabbit papillomavirus, sometimes referred to as the Shope papillomavirus, large cutaneous papillomas were induced on the backs of Dutch Belted rabbits. Following intravenous administration of hematoporphyrin derivative, PDT was delivered with white light. Marked regression of the papillomas was noted with replacement by normal hair-bearing skin. The clinical implications of this work to the control of laryngeal papillomatosis is discussed.

[Rabbit brain tumor model]

We have established the rabbit brain tumor model. The domestic rabbits (Japanese White) inplanted the VX2 rabbit epidermoid carcinoma cell were died within three weeks after the inplantation. These brains showed massive brain tumor remarkably infiltrating into the surrounding brain. The flowcytometry of intracerebral VX2 tumor revealed a monopeak at the 2C and relatively large amount of S-phase cells. We think that this brain tumor model is more convenient for the combination treatment with operation and chemotherapy, because the rabbit brain is larger and intravenous injection is more easy than the rat or mouse.

Collagenolytic activity of rabbit V2 carcinoma implanted in the nude mouse

The relative contribution of host cells and tumor cells to the production of collagenase and its regulation during tumorigenesis were studied with the use of a heterologous rabbit tumor-nude mouse host system. The V2 carcinoma, a malignant neoplasm of the New Zealand White rabbit, behaved as a nonmetastasizing, noninvasive tumor when implanted and grown in the inbred Swiss albino nude mouse. The extracts from both tumors contained similar levels of collagenase. Tumor explants also released enzyme into culture medium in both cases, but the rabbit tumor produced approximately 10 times more collagenase than the nude mouse. Freeze-thawing of the explants or treatment with cycloheximide markedly inhibited the appearance of enzyme in the medium from the rabbit tumor but not from the nude mouse tumor. The relative proportions of mouse- and rabbit-derived collagenase in the nude mouse tumor extracts and culture medium were determined with the use of antibodies specific for rabbit V2 tumor and mouse bone collagenases. Approximately 70% of the nude mouse tumor enzyme was derived from the rabbit tumor, and approximately 30% was derived from the mouse host. These findings indicate that the former might represent stored enzyme carried over during tumor transplantation into the nude mouse, whereas the latter might have originated from stimulation of host cells during tumorigenesis.

Spontaneous tumor regression: possible relationship to in vitro parameters of tumor immunity

Evidence is discussed from three animal systems (Shope papillomas in rabbits, Moloney sarcomas in mice, Schmidt-Ruppin-Rous sarcomas in Japanese quail) that immune reactions can be important in spontaneous tumor regression. In vitro studies performed in these systems indicate that blocking serum factors can thwart cell-mediated immune responses and that "unblocking" antibodies are often found in animals whose tumors have regressed. To what extent spontaneous regressions of human neoplasms are due to immunologic mechanisms is unknown; in 2 patients who had undergone spontaneous tumor regression, tumor cell cytotoxic lymphocytes and unblocking serum factors were detected. Better animal models and better knowledge about the mechanisms of tumor immune reactions are needed before tumor regression can be more successfully induced by immunologic manipulation (to what extent that will even be feasible in man is unknown).

[Interactions of Shope papilloma virus with SV40 in adult domestic rabbit cell lines derived from normal skin or from Shope papilloma virus infected skin (author's transl)]

Three cell lines from adult domestic rabbit are infected with SV40: LP 17 and LP 45 derived from normal skin and LP 42 PS derived from skin infected for 24 h with Shope papilloma virus. The fibroblastic morphology of the cultures is not changed. SV40 is not recovered and T antigen is only detected in LP 42 PS cell line after 29 passages. To know if Shope papilloma virus facilitates penetration of SV40, cultures of LP 45 are first infected with Shope papilloma virus for 2 h and for 24 h, then superinfected with SV40. There is no cellular alteration, and T antigen induced by SV40 is only detected in cells pretreated for 24 h with Shope papilloma virus, after 20 passages. When cultures LP 45 are infected with Shope papilloma virus neutralized with a high titer antiserum and superinfected with SV40, T antigen is not detected. Superinfected cells containing specific SV40 T antigen do not induce tumors either in new born hamsters or in rabbits but they are able to grow in colonies in soft agar. LP 42 PS cell line and LP 45 cells infected with Shope papilloma virus for 24 h containe Shope papilloma virus genome which is able to modify the permissivity of rabbit cells to SV40.

New Papovavirus Contaminating Shope Papillomata

A virus having the characteristics of the papovaviruses was isolated from several naturally occurring cottontail papillomata. Serologic and animal inoculation studies indicate that it is not Shope papilloma virus, but a previously undescribed, nonpathogenic agent of cottontail rabbits.

Organ cultures of newborn rabbit skin affected by rabbit papilloma virus

Small fragments of newborn rabbit skin were exposed to papilloma virus and transferred to tissue culture. Control cultures were treated the same way, but without addition of the virus. These cultures were then followed for 4 weeks. During the first ten days, the number of epidermal elements declined gradually in both test and control cultures. From the 10th day on, however, a marked proliferation of the remaining epidermal cells was observed in cultures exposed to the virus, whereas no further changes were noticed in the control cultures.