Search

Objectives: This study was designed to determine if aspirin resistance is associated with clinical events.Background: Aspirin resistance, defined by platelet function testing and presumed clinical unresponsiveness to aspirin, has been previously reported by our group and others. However, little information exists linking the laboratory documentation of aspirin resistance and long-term clinical events.Methods: We prospectively enrolled 326 stable cardiovascular patients from 1997 to 1999 on aspirin (325 mg/day for > or =7 days) and no other antiplatelet agents. We tested for aspirin sensitivity by optical platelet aggregation using adenosine diphosphate (ADP) and arachidonic acid (AA). The primary outcome was the composite of death, myocardial infarction (MI), or cerebrovascular accident (CVA). Mean follow-up was 679 +/- 185 days. Aspirin resistance was defined as a mean aggregation of > or =70% with 10 microM ADP and > or =20% with 0.5 mg/ml AA.Results: Of the patients studied, 17 (5.2%) were aspirin resistant and 309 (94.8%) were not aspirin resistant. During follow-up, aspirin resistance was associated with an increased risk of death, MI, or CVA compared with patients who were aspirin sensitive (24% vs. 10%, hazard ratio [HR] 3.12, 95% confidence interval [CI] 1.10 to 8.90, p = 0.03). Stratified multivariate analyses identified platelet count, age, heart failure, and aspirin resistance to be independently associated with major adverse long-term outcomes (HR for aspirin resistance 4.14, 95% CI 1.42 to 12.06, p = 0.009).Conclusions: This study demonstrates the natural history of aspirin resistance in a stable population, documenting a greater than threefold increase in the risk of major adverse events associated with aspirin resistance. [ABSTRACT FROM AUTHOR]

Background: Patients with non-dysplastic Barrett's esophagus (ND-BE) and low-grade dysplasia (LGD) are typically monitored by periodic endoscopic surveillance, while those with high-grade dysplasia (HGD) and esophageal adenocarcinoma (EAC) are usually treated by more aggressive interventions like endoscopic mucosal resection, ablation or surgery. Therefore, the accurate grading of dysplasia in Barrett's esophagus (BE) is essential for proper patient care. However, there is significant interobserver and intraobserver variability in the histologic grading of BE dysplasia. The objective of this study was to create an immunohistochemical (IHC) panel that facilitates the grading of BE dysplasia and can be used as an adjunct to histology in challenging cases., Methods: 100 BE biopsies were re-graded for dysplasia independently by 3 subspecialized gastrointestinal pathologists. IHC staining for CDX2, p120ctn, c-Myc and Jagged1 proteins was then performed and assessed by two separate methods of semi-quantitative scoring. Scores were integrated using a principal component analysis (PCA) and receiver operating characteristic (ROC) curve., Results: Principal component analysis demonstrated the ability of this panel of proteins to segregate ND-BE/LGD and HGD/EAC, as the expression of the four proteins is significantly altered between the two subsets. Analysis of the receiver operating characteristic curve showed that this panel has the potential to aid in the grading of dysplasia in these two subcategories with both high sensitivity and specificity. While not able to discriminate between ND-BE and LGD, this panel of four proteins may be used as an adjunct to help discriminate subsets of ND-BE/LGD from HGD/EAC., Conclusions: We propose that the maximum utility of this IHC panel of CDX2, p120ctn, c-Myc, and Jagged1 proteins would be to distinguish between LGD and HGD in histologically challenging cases, given the aggressive interventions still used for HGD in many institutions, and hence may aid in the optimal patient management. The results of this initial study are promising, though further validation is needed before this panel can be used clinically, including future randomized prospective studies with larger patient cohorts from diverse locations.

Esophageal squamous cell carcinoma (ESCC) is an aggressive malignancy with a poor prognosis due to its highly invasive and metastatic potential. The molecular pathogenesis underlying the invasive mechanism of ESCC is not well known because of the lack of existing models to study this disease. p120-Catenin (p120ctn) and the epidermal growth factor receptor (EGFR) have each been implicated in several cancers, including ESCC. p120ctn is down-regulated in 60% of ESCC tumors, whereas EGFR is the most commonly overexpressed oncogene in ESCC. For these reasons, we investigated the cooperation between p120ctn and EGFR and its effect on ESCC invasion. We show that p120ctn down-regulation is commonly associated with EGFR overexpression. By using a three-dimensional culture system, we demonstrate that the inverse relationship between p120ctn and EGFR has biological implications. Specifically, p120ctn down-regulation coupled with EGFR overexpression in human esophageal keratinocytes (EPC1-PE) was required to promote invasion. Morphological comparison of EPC1-PE cells grown in three-dimensional culture and human ESCC revealed identical features, including significantly increased cellularity, nuclear grade, and proliferation. Molecular characteristics were measured by keratin expression patterns, which were nearly identical between EPC1-PE cells in three-dimensional culture and ESCC samples. Altogether, our analyses have demonstrated that p120ctn down-regulation and EGFR overexpression are able to mimic human ESCC in a relevant three-dimensional culture model., (Copyright © 2015 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.)

Numerous studies have demonstrated a link between elevated polyamine biosynthesis and neoplastic growth, but the specific contribution of spermine synthase to epithelial tumor development has never been explored in vivo. Mice with widespread overexpression of spermine synthase (CAG-SpmS) exhibit decreased spermidine levels, increased spermine and a significant rise in tissue spermine:spermidine ratio. We characterized the response of CAG-SpmS mice to two-stage skin chemical carcinogenesis as well as spontaneous intestinal carcinogenesis induced by loss of the Apc tumor suppressor in Apc (Min) (/+) (Min) mice. CAG-SpmS mice maintained the canonical increases in ornithine decarboxylase (ODC) activity, polyamine content and epidermal thickness in response to tumor promoter treatment of the skin. The induction of S-adenosylmethionine decarboxylase (AdoMetDC) activity and its product decarboxylated AdoMet were impaired in CAG-SpmS mice, and the spermine:spermidine ratio was increased 3-fold in both untreated and 12-O-tetradecanoylphorbol-13-acetate (TPA)-treated skin. The susceptibility to 7,12-dimethylbenz[a]anthracene (DMBA)/TPA skin carcinogenesis was not altered in CAG-SpmS mice, and SpmS overexpression did not modify the previously described tumor resistance of mice with targeted antizyme expression or the enhanced tumor response in mice with targeted spermidine/spermine-N ( 1) -acetyltransferase expression. CAG-SpmS/Min mice also exhibited elevated spermine:spermidine ratios in the small intestine and colon, yet their tumor multiplicity and size was similar to Min mice. Therefore, studies in two of the most widely used tumorigenesis models demonstrate that increased spermine synthase activity and the resulting elevation of the spermine:spermidine ratio does not alter susceptibility to tumor development initiated by c-Ha-Ras mutation or Apc loss.

A composite cytomegalovirus-immediate early gene enhancer/chicken β-actin promoter (CAG) was utilized to generate transgenic mice that overexpress human spermidine synthase (SpdS) to determine the impact of elevated spermidine synthase activity on murine development and physiology. CAG-SpdS mice were viable and fertile and tissue SpdS activity was increased up to ninefold. This increased SpdS activity did not result in a dramatic elevation of spermidine or spermine levels but did lead to a 1.5- to 2-fold reduction in tissue spermine:spermidine ratio in heart, muscle and liver tissues with the highest levels of SpdS activity. This new mouse model enabled simultaneous overexpression of SpdS and other polyamine biosynthetic enzymes by combining transgenic animals. The combined overexpression of both SpdS and spermine synthase (SpmS) in CAG-SpdS/CAG-SpmS bitransgenic mice did not impair viability or lead to overt developmental abnormalities but instead normalized the elevated tissue spermine:spermidine ratios of CAG-SpmS mice. The CAG-SpdS mice were bred to MHC-AdoMetDC mice with a >100-fold increase in cardiac S-adenosylmethionine decarboxylase (AdoMetDC) activity to determine if elevated dcAdoMet would facilitate greater spermidine accumulation in mice with SpdS overexpression. CAG-SpdS/MHC-AdoMetDC bitransgenic animals were produced at the expected frequency and exhibited cardiac polyamine levels comparable to MHC-AdoMetDC littermates. Taken together these results indicate that SpdS levels are not rate limiting in vivo for polyamine biosynthesis and are unlikely to exert significant regulatory effects on cellular polyamine content and function.

Epidermal growth factor receptor (EGFr) has been shown to be induced and activated in cells infected with HPV, suggesting that it may play a physiological role in viral replication or in the formation or maintenance of warts. To investigate this possibility, human foreskin tissue was infected with HPV11 and transplanted onto the renal capsule and the dermis of immunodeficient mice. The animals were treated orally or topically with the potent EGFr inhibitor CP-545130, with treatment starting either immediately following graft attachment, or following a 70 day period to allow development of warts. The rate of appearance of warts, wart size and number were monitored. In addition, we measured intra-lesional HPV replication levels and examined the morphology of the graft tissues. Analysis of the results showed no significant difference between placebo and compound-treated groups, despite high levels of compound present in the graft tissue. We conclude that EGFr kinase activity is not required for the development and maintenance of HPV-11-induced warts in this model.

The first product to be clinically evaluated as a microbicide contained the nonionic surfactant nonoxynol-9 (nonylphenoxypolyethoxyethanol; N-9). Many laboratories have used N-9 as a control compound for microbicide assays. However, no published comparisons of the results among laboratories or attempts to establish standardized protocols for preclinical testing of microbicides have been performed. In this study, we compared results from 127 N-9 toxicity and 72 efficacy assays that were generated in five different laboratories over the last six years and were performed with 14 different cell lines or tissues. Intra-assay reproducibility was measured at two-, three-, and fivefold differences using standard deviations. Interassay reproducibility was assessed using general linear models, and interaction between variables was studied using step-wise regression. The intra-assay reproducibility within the same N-9 concentration, cell type, assay duration, and laboratory was consistent at the twofold level of standard deviations. For interassay reproducibility, cell line, duration of assay, and N-9 concentration were all significant sources of variability (P < 0.01). Half-maximal toxicity concentrations for N-9 were similar between laboratories for assays of similar exposure durations, but these similarities decreased with lower test concentrations of N-9. Results for both long (>24 h) and short (<2 h) exposures of cells to N-9 showed variability, while assays with 4 to 8 h of N-9 exposure gave results that were not significantly different. This is the first analysis to compare preclinical N-9 toxicity levels that were obtained by different laboratories using various protocols. This comparative work can be used to develop standardized microbicide testing protocols that will help advance potential microbicides to clinical trials.

The present study was designed to provide a better understanding of the role played by AdoMetDC (S-adenosylmethionine decarboxylase), the key rate-controlling enzyme in the synthesis of spermidine and spermine, in controlling polyamine levels and the importance of polyamines in cardiac physiology. The alphaMHC (alpha-myosin heavy chain) promoter was used to generate transgenic mice with cardiac-specific expression of AdoMetDC. A founder line (alphaMHC/AdoMetDC) was established with a >100-fold increase in AdoMetDC activity in the heart. Transgene expression was maximal by 1 week of age and remained constant into adulthood. However, the changes in polyamine levels were most pronounced during the first week of age, with a 2-fold decrease in putrescine and spermidine and a 2-fold increase in spermine. At later times, spermine returned to near control levels, whereas putrescine and spermidine levels remained lower, suggesting that compensatory mechanisms exist to limit spermine accumulation. The alphaMHC/AdoMetDC mice did not display an overt cardiac phenotype, but there was an increased cardiac hypertrophy after beta-adrenergic stimulation with isoprenaline ('isoproterenol'), as well as a small increase in spermine content. Crosses of the alphaMHC/AdoMetDC with alphaMHC/ornithine decarboxylase mice that have a >1000-fold increase in cardiac ornithine decarboxylase were lethal in utero, presumably due to increase in spermine to toxic levels. These findings suggest that cardiac spermine levels are highly regulated to avoid polyamine-induced toxicity and that homoeostatic mechanisms can maintain non-toxic levels even when one enzyme of the biosynthetic pathway is greatly elevated but are unable to do so when two biosynthetic enzymes are increased.

A limitation in advancing the study of HIV-1 is the lack of a suitable small animal model system that allows for HIV-1 infection to be monitored within human target epithelium. Studies have demonstrated that HIV-1 can infect vaginal mucosa after sexual exposure; however, the primary target cells for HIV-1 in the vagina and interactions between these target cells are not completely defined. A mouse human vaginal xenograft model that recapitulates, histologically and cytochemically, the features of the human vaginal epithelial barrier has been developed in our laboratory. Results of experiments utilizing this system to characterize HIV-1 BaL and IIIB infections within human vaginal xenografts are reported here. HIV-1 RNA, spliced transcripts, and HIV-1 p24 core antigen protein were detected in the xenografts 7 days after infection. This unique system offers a small animal model for studying HIV-1 transmission and replication within the context of natural host tissue and for examining initial events and cell populations involved in the establishment of HIV-1 infection.

Recent epidemiological studies have found that women infected with both herpes simplex virus type 2 (HSV-2) and human papillomavirus (HPV) type 16 or HPV-18 are at greater risk of developing cervical carcinoma compared to women infected with only one virus. However, it remains unclear if HSV-2 is a cofactor for cervical cancer or if HPV and HSV-2 interact in any way. We have studied the effect of HSV-2 infection on HPV-11 gene expression in an in vitro double-infection assay. HPV transcripts were down-regulated in response to HSV-2 infection. Two HSV-2 vhs mutants failed to reduce HPV-16 E1;E4 transcripts. We also studied the effect of HSV-2 infection on preexisting experimental papillomas in a vaginal epithelial xenograft model. Doubly infected grafts demonstrated papillomatous transformation and the classical cytopathic effect from HSV-2 infection. HPV and HSV DNA signals were mutually exclusive. These studies may have therapeutic applications for HPV infections and related neoplasms.

A small animal model for the in vivo study of human immunodeficiency virus-1 and other fastidious infectious agents in human host target tissues is critical for the advancement of therapeutic and preventative strategies. Our laboratory has developed a human vaginal xenograft model that histologically recapitulates features of the human vaginal epithelial barrier. Vaginal xenografts were surgically implanted into C.B.-Igh-1(b)/IcrTac-Prkdc(scid) (SCID) and NOD/LtSz-scid/scid (NOD/SCID) mice, with and without human peripheral blood mononuclear cell reconstitution. Immunohistochemical staining of vaginal xenografts demonstrated that in the SCID strain healed vaginal xenografts did not retain intrinsic human immune cells at baseline levels, whereas the NOD/SCID strain supported retention of intrinsic human immune cell populations within the xenografts for at least 2 months after engraftment. In peripheral blood mononuclear cell-reconstituted NOD/SCID mice with vaginal xenografts, flow cytometric analyses detected human immune cell populations in the peripheral blood and immunohistochemical methods detected infiltration of human CD45+ cells in the mouse spleens and vaginal xenografts for at least 2 months after reconstitution. This optimized NOD/SCID human vaginal xenograft model may provide a unique small animal in vivo system for the study of human immunodeficiency virus-1 transmission and infection.

We determined the prevalence and clinical predictors of aspirin resistance by prospectively studying 325 patients with stable cardiovascular disease who were receiving aspirin (325 mg/day for > or =7 days) but no other antiplatelet agents. We also compared the detection of aspirin resistance with optical platelet aggregation, a widely accepted method, with a newer, more rapid method, the platelet function analyzer (PFA)-100, a whole blood test that measures platelet adhesion and aggregation ex vivo. Blood samples were analyzed in a blinded fashion for aspirin resistance by optical aggregation using adenosine diphosphate (ADP) and arachidonic acid, and by PFA-100 using collagen and/or epinephrine and collagen and/or ADP cartridges to measure aperture closure time. Aspirin resistance was defined as a mean aggregation of > or =70% with 10 microM ADP and a mean aggregation of > or =20% with 0.5 mg/ml arachidonic acid. Aspirin semiresponders were defined as meeting one, but not both of the above criteria. Aspirin resistance by PFA-100 was defined as having a normal collagen and/or epinephrine closure time (< or =193 seconds). By optical aggregation, 5.5% of the patients were aspirin resistant and 23.8% were aspirin semiresponders. By PFA-100, 9.5% of patients were aspirin resistant. Of the 18 patients who were aspirin resistant by aggregation, 4 were also aspirin resistant by PFA-100. Patients who were either aspirin resistant or aspirin semiresponders were more likely to be women (34.4% vs 17.3%, p = 0.001) and less likely to be smokers (0% vs 8.3%, p = 0.004) compared with aspirin-sensitive patients. There was a trend toward increased age in patients with aspirin resistance or aspirin semiresponders (65.7 vs 61.3 years, p = 0.06). There were no differences in aspirin sensitivity by race, diabetes, platelet count, renal disease, or liver disease.

A broad-spectrum vaginal microbicide must be effective against a variety of sexually transmitted disease pathogens and be minimally toxic to the cell types found within the vaginal epithelium, including vaginal keratinocytes. We assessed the sensitivity of primary human vaginal keratinocytes to potential topical vaginal microbicides nonoxynol-9 (N-9), C31G, and sodium dodecyl sulfate (SDS). Direct immunofluorescence and fluorescence-activated cell sorting analyses demonstrated that primary vaginal keratinocytes expressed epithelial cell-specific keratin proteins. Experiments that compared vaginal keratinocyte sensitivity to each agent during a continuous, 48-h exposure demonstrated that primary vaginal keratinocytes were almost five times more sensitive to N-9 than to either C31G or SDS. To evaluate the effect of multiple microbicide exposures on cell viability, primary vaginal keratinocytes were exposed to N-9, C31G, or SDS three times during a 78-h period. In these experiments, cells were considerably more sensitive to C31G than to N-9 or SDS at lower concentrations within the range tested. When agent concentrations were chosen to result in an endpoint of 25% viability after three daily exposures, each exposure decreased cell viability at the same constant rate. When time-dependent sensitivity during a continuous 48-h exposure was examined, exposure to C31G for 18 h resulted in losses in cell viability not caused by either N-9 or SDS until at least 24 to 48 h. Cumulatively, these results reveal important variations in time- and concentration-dependent sensitivity to N-9, C31G, or SDS within populations of primary human vaginal keratinocytes cultured in vitro. These investigations represent initial steps toward both in vitro modeling of the vaginal microenvironment and studies of factors that impact the in vivo efficacy of vaginal topical microbicides.

Sodium dodecyl sulfate (SDS), an alkyl sulfate surfactant derived from an organic alcohol, possesses surfactant properties but also denatures and unfolds both monomeric and subunit proteins. In preliminary experiments, we demonstrated that SDS is a potent inactivator of herpes simplex virus type 2 and human immunodeficiency virus type 1 at concentrations comparable to those used for the surfactant nonoxynol-9. We hypothesized that SDS might be capable of denaturing the capsid proteins of nonenveloped viruses. In this report, we demonstrate inactivation of rabbit, bovine, and human papillomaviruses after brief treatment with dilute solutions of SDS. Effective concentrations were nontoxic to rabbit skin and to split-thickness grafts of human foreskin epithelium. This is the first report of a microbicidal surfactant that will inactivate papillomaviruses. We propose that SDS is now a candidate microbicide for formulation and testing with humans.

Rabbit oral papillomavirus (ROPV) is a mucosatropic papillomavirus which naturally infects oral mucosal sites of domestic rabbits. In this study, we tested the hypothesis that rabbit genital mucosa is also susceptible to ROPV infection by using the athymic mouse xenograft system and adult immunocompetent rabbits. Subrenal xenografts of ROPV-infected rabbit vulvar and penile sheath tissues were strongly positive for ROPV infection by histologic, in situ hybridization, and Southern analyses. Direct inoculation of adult rabbit penises with infectious ROPV produced small raised lesions of approximately 1 by 1 by 1 mm that were ROPV positive by both in situ hybridization and Southern analyses and were also viral capsid antigen positive by immunohistological staining. Infection of rabbit genital tissues with ROPV may be a useful animal model for the study of genital tissue-targeting papillomaviruses.

The athymic mouse xenograft system was used to prepare infectious stocks of two additional anogenital tissue-targeting human papillomaviruses (HPVs) in a manner similar to that for the development of infectious stocks of HPV-11. An anal condyloma from a transplant patient was used as material for extraction of infectious virus, and human foreskin fragments were incubated with the virus suspension and transplanted subrenally into athymic mice. Partial viral sequencing indicated that two rare HPV types (HPV-40 and HPVLVX82/MM7) were concurrently present in both the patient condyloma and the foreskin xenografts, and passage of both types was achieved as a mixed infection with HPV-40 predominating. Xenografts that developed from simultaneous infection of human foreskin fragments with HPV-11, -40, and -LVX82/MM7 virions produced regionally separate areas of HPV-11 and -40 infection as determined by in situ hybridization. In addition, in situ hybridization with HPV-40 and HPVLVX82/MM7 DNA probes demonstrated that both of these HPV types were present as adjacent but separate infections within the same anal condyloma of the transplant patient. These studies indicate that multiple HPV types can simultaneously infect genital tissue and that each HPV type predominantly maintains regional separation within the same papilloma.

Several small, raised lesions from the underside of the tongue of domestic rabbits were isolated, and an extract prepared and tested for the presence of rabbit oral papillomavirus (ROPV). Two weeks after inoculation of this extract into the underside of rabbit tongues, multiple small discrete, grey-white nodules were observed that reached a maximum size of 2 mm in diameter by 5 weeks. These lesions showed typical ROPV pathology, and nuclei stained positive for papillomavirus (PV) group-specific antigen (GSA) by immunocytochemistry. Tissue fragments from rabbit tongues were incubated with a suspension of ROPV and placed subrenally into athymic mice. After 60 days, cysts were removed, sections cut for histology, and a virus stock prepared. GSA staining and in situ hybridization demonstrated that the xenografts were morphologically transformed with areas showing strong nuclear staining for viral capsid antigen and ROPV DNA. Extracts prepared from the pooled xenografts contained infectious ROPV as demonstrated by inoculation into the undersurface of tongues of nonimmune New Zealand White rabbits. The results demonstrated that stocks of infectious ROPV can be prepared in the athymic mouse xenograft system for use in studies on the experimental transmission of a mucosal-targeting animal papillomavirus.

Plasmids containing cottontail rabbit papillomavirus (CRPV) DNA can induce papillomas in vivo, but efficiency has been low. The aim of the present investigation was to explore some of the technical variables involved in inoculation of rabbits with recombinant CRPV DNA in attempts to improve both yield and consistency of papilloma induction. It was found that induction of epidermal hyperplasia, with either a mixture of turpentine and acetone or phorbol esters, produced a marked increase in papilloma yield. An additional powerful factor was the use of very vigorous, cutaneous scarification, sufficient to penetrate the papillary dermis and produce bleeding. When used in combination, papilloma yields were consistent and often reached 90-100% of inoculated sites. A number of other variables which did not consistently affect papilloma yield were tested. These included bleb and puncture injections, plasmid dose, vector type, occlusive dressings, lipofection reagent, carrier DNA, and different methods for plasmid DNA extraction and purification. It is concluded that the most important variables in improving papilloma yields were prior induction of epidermal hyperplasia and vigorous cutaneous scarification.

Baculovirus-expressed human papillomavirus type 11 (HPV-11) major capsid protein (L1) virus-like particles (VLPs) were produced in insect cells and purified on CsCl density gradients. The VLPs retained conformational neutralizing epitopes that were detected by a series of HPV-11-neutralizing monoclonal antibodies. Electron microscopy determined that the HPV-11 L1 VLPs were variable in size with a surface topography similar to that of infectious HPV-11. The VLPs were very antigenic, and induced high titres of neutralizing antibodies in rabbits and mice when used as an immunogen without commercial preparations of adjuvant. These VLP reagents may be effective vaccines for protection against HPV infections.

Daily academic classroom performance was recorded in a day hospital school using a commonly employed reading and math series as part of an 11-week double-blind, placebo controlled, crossover comparison of dextroamphetamine (d-AMPH) and methylphenidate (MPH) in 33 hyperactive boys. Students attempted more math and reading tasks while on either active drug. The percent correct and the number of attempted problems of the reading series improved with both drugs while the percent correct for the math series occurred with d-AMPH only. No dose-response relationship was found for either stimulant. Moderate, transient adverse effects were common for both drugs.

Monoclonal antibodies recognizing human papillomavirus type 11 (HPV-11) were prepared from BALB/c mice immunized with intact HPV-11 virions obtained from morphologically transformed human foreskin xenografts grown subrenally in athymic mice. Four of five monoclonal antibodies that were reactive by enzyme-linked immunosorbent assay only to intact virions neutralized HPV-11 infectivity in the athymic mouse xenograft system.

Warts of the hands and feet are common cutaneous diseases. Human papillomaviruses types 1 and 2 are probably responsible for most of the lesions. It is difficult to study these infections in the laboratory, since human papillomaviruses do not replicate in cell cultures or experimental animals. We have recently developed a system in which xenografts of human tissues were infected with HPV-11 and transplanted beneath the renal capsule of athymic mice. We now report the adaptation of this system to the induction of HPV-1 infection of xenografts of fetal human foot and hand skin. The experimentally produced warts have the same morphology as naturally occurring lesions. HPV-1 DNA and papillomavirus capsid antigen are abundant in the experimentally infected tissues.