[Revelation of the list of occupational diseases and diagnostic criteria for occupational diseases].

The list of occupational diseases reflecting the latest advances in the identification and recognition of occupational diseases, and providing guidance on the protection of workers' health rights and interests and the prevention, recording, notification and compensation of related occupational diseases. Diagnostic criteria for occupational diseases are an important basis for making diagnoses attributable to occupational diseases, and provide a theoretical basis for health monitoring of occupational groups and occupational hygiene supervision. This thesis starts with the definition of the occupational disease elaborates in detail the development history of list of occupational diseases in International Labour Organization (ILO) , compares the list of occupational diseases in China (2013 version) with the list of occupational diseases in international (2010 version) , and then introduces in detail the latest diagnostic standards of the major occupational diseases. And finally, it puts forward relevant suggestions on the list and diagnostic level of China's occupational diseases, so as to provide certain insights for the further improvement of the list and diagnostic standards of occupational diseases.

[Preliminary application of postoperative fast track transfer to intensive care unit for the geriatric hip fractures under enhanced recovery after surgery].

Objective: To develop a fast track transfer to intensive care unit (ICU) for the perioperative high-risk elderly patients after hip fracture surgery and analyze the preliminary clinical effect of the application. Methods: From January 2014 to December 2017, before the application of postoperative fast track transfer to ICU, the clinical data of 195 elderly patients with hip fracture were included in a retrospective analysis. Among 195 hip fracture patients, 18 were transferred to ICU post operation (non-fast track group). Multivariate logistic regression analysis was applied to investigate relevant risk factors for transferring to ICU after hip fracture surgery. Based on risk factors acquired from the analysis and clinical experience, the fast track transfer to ICU for the perioperative high-risk elderly patients after hip fracture surgery was constructed according to the preliminary and experiential criteria. From January 2018 to December 2019, the clinical data of 70 patients (fast track group) who were transferred to ICU after hip fracture surgery through the fast track were collected and compared with non-fast track group. Results: Multivariate regression analysis revealed that American Society of Anesthesiologists classification(≥Ⅲ) (OR=4.260, 95%CI:1.157-15.683, P=0.029), pre-hospital stage (≥48 h) (OR=4.301, 95%CI:1.212-15.266, P=0.024), hemoglobin concentration at admission(<90 g/L) (OR=7.979, 95%CI:1.936-32.889, P=0.004), coronary heart disease as one comorbidity(OR=6.063, 95%CI:1.695-21.693, P=0.006) were independent risk factors for transferring to ICU after hip fracture surgery. There were no significant difference in gender, age, fracture type, hemoglobin concentration at admission and time of pre-hospital stage between the non-fast track group and fast track group(all P>0.05). However, the number of comorbidities in the fast track group was significantly higher than that in the non-fast track group (Z=-1.995, P=0.046). The time to surgery, postoperative hospital stay, and length of hospital stay in fast track group were all significantly less than those in non-fast track group (Z=-2.121, -2.726, -3.130, all P<0.05). Also, there were fewer medical consultations needed and fewer patients who stayed in ICU more than or equal to 2 nights in fast track group than that in non-fast track group(all P<0.05). There were no significant difference in the rate of patients who transferred from the general ward to ICU after transferring from ICU to the general ward, the proportion of patients who received more than or equal to 4 departments, operation time, hospitalization expense, mortality during hospitalization, 30-day mortality and 90-day mortality after operation between the two groups(all P>0.05). Conclusions: The fast track constructed in this study can reduce time to surgery, postoperative hospitalization stay and length of hospitalization stay for the perioperative high-risk elderly patients with hip fractures and is a specific clinical application of eras concept based on multidisciplinary team.

[Risk factors of cirrhosis combined with sarcopenia and their impact on clinical outcomes].

Objective: To study the occurrence of sarcopenia in patients with liver cirrhosis, and to explore their risk factors and impact on clinical outcomes. Methods: 199 hospitalized cases with liver cirrhosis were collected for nutritional risk screening, anthropometric measurement and blood biochemical examination. The body composition analysis was measured based on the skeletal muscle content of the four limbs to calculate the appendicular skeletal muscle mass index (ASMI). Patients were divided into sarcopenia and non-sarcopenia group and the relevant indexes of both groups were compared to screen for factors affecting the occurrence of sarcopenia. During the follow-up of 48 months, the survival and complications of the both groups were compared. Statistical analysis was performed using t-test, χ(2) test and logistic regression analysis in terms of different data. Results: The incidence of sarcopenia in cirrhosis was 36.7%, with the highest prevalence in patients with recurrent hepatic encephalopathy (62.5%), followed by patients with abdominal ascites / pleural effusion (37.6%). The incidence of sarcopenia was significantly higher in those with nutritional risk than in those without nutritional risk (P < 0.05). However, even among those without nutritional risk, 14.8% had combined sarcopenia. The body mass index (BMI), upper arm muscle circumference (AMC), and body cell mass (BCM) of the sarcopenia group were lower than those of the non-sarcopenia group (P < 0.05), and the edema index (ECW/TBW) was higher than the latter (P < 0.05). Multivariate analysis showed that age, gender, BMI, and complications of hepatic encephalopathy were the main influencing factors of cirrhosis combined with sarcopenia (P < 0.05). During the follow-up period, the sarcopenia group had a higher mortality rate than non-sarcopenia goup (P < 0.05), and the incidence of recurrent abdominal ascites/pleural effusion, hepatic encephalopathy, and infection was also significantly elevated (P < 0.05). Conclusion: Sarcopenia is one of the manifestations of malnutrition in patients with liver cirrhosis, which increases the risk of mortality and other complications, and has adverse impact on the clinical outcome. Additionally, older age, male sex, low BMI and recurrent hepatic encephalopathy has higher risk for developing sarcopenia.

[Research advances of sarcopenia in chronic liver disease].

Sarcopenia is the main constituent of malnutrition and is a frequent complication of chronic liver diseases, which affects up to 70% of patients with advanced liver diseases. It has been associated with adverse clinical outcomes and prognosis, including poor quality of life, development of other complications and reduction in survival rate of non-transplant patients and transplant recipients. Chronic liver disease causes alteration in glucose metabolism, lipid oxidation, ketogenesis and protein catabolism, leading to the loss of adipose and muscle tissue. In addition, inadequate nutrients intake and limited or lack of physical activity perpetuate the reduction of muscle mass. Recently, the roles and mechanisms of muscle growth-related hormones, hyperammonemia-mediated signaling pathways and gut microbiota have been recognized. In view of its impact in chronic liver disease, sarcopenia can be considered as a powerful prognostic factor and a useful additional tool in the global assessment of patients with advanced liver disease. Rational nutritional intervention, appropriate physical exercise, effective ammonia lowering strategies, hormone supplements and targeted molecular therapy (use of myostatin blockers), and liver transplantation, may improve sarcopenia, but still needs more studies for validation.

[Nutritional status and energy metabolism characteristics in patients with nonalcoholic fatty liver disease].

Objective: To study the nutritional status and energy metabolic characteristics of patients with nonalcoholic fatty liver disease (NAFLD), and to provide evidence for clinical evaluation and intervention. Methods: A total of 359 NAFLD patients diagnosed on ultrasound from June 2015 to March 2017 were selected as study subjects and divided into mild, moderate to severe fatty liver disease group and 50 healthy subjects as control group. The changes of ICW, ECW, body fat, skeletal muscle, protein and visceral fat area (VFA) of patients and controls were analyzed by using body composition analyzer. The energy metabolism index was measured by the oxidation rate of resting energy expenditure(REE), respiratory quotient (RQ), and the oxidation rates of the three nutrients (CHO %, FAT %, and PRO %). According to different types of data, non-parametric tests like Kruskal-Wallis or χ(2) were used for this analysis. Results: Compared with the mild fatty liver group and the control group, the moderate and severe fatty liver group the BMI, waist circumference, waist-hip ratio were significantly elevated (P-value < 0.001), and their serum alanine aminotransferase, triglyceride, total cholesterol, high-density lipoprotein, low-density lipoprotein, FBS levels were significantly increased (P value < 0.05). The Body composition analysis showed that there was no significant difference in skeletal muscle content between the three groups (P = 0.067). The ICW, ECW, protein, body fat content of moderate and severe fatty liver group were significantly higher than those of mild fatty liver group and control group (P < 0.01), but there was no significant difference between the mild fatty liver group and the control group. There was significant difference in the VFA between the three groups, while VFA in the moderate and severe fatty liver group was significantly increased. Metabolic results showed that the RQ of patients with moderate-severe fatty liver and mild fatty liver were 0.72 ± 0.08 and 0.78 ± 0.06, respectively, which were lower than those of the control group (0.80 ± 0.02), P = 0.004. Resting energy expenditure (REE) was not significantly different between moderate and severe fatty liver group and mild fatty liver group (P = 0.207), but both were significantly higher than those of the control group (P < 0.001). The percentages of CHO, FAT and PRO in moderate and severe fatty liver group were 19.49% ± 9.71%, 66.23% ± 12.54% and 14.22% ± 6.11% respectively. Compared with the control group, CHO % decreased, and FAT % increased. Conclusion: NAFLD patients have different extent of nutritional imbalance and energy metabolism disorders, the use of Body Composition analyzer and metabolic cart can comprehensively assess and monitor NAFLD patient's nutrition and energy metabolism status, to provide a basis for clinical intervention.

Expression of EpCAM and Wnt/ ß-catenin in human colon cancer.

The aims of this study were to explore the correlation between the expression of EpCAM and the Wnt/ß-catenin pathway in human colon cancer and its clinical significance for the evaluation of cancer prognosis. Samples from colon cancer, para-carcinoma, or benign intestinal tissue from individual patients (50) and from normal intestinal mucosal tissues (20) were obtained from the Pathology Department of the Shandong Province Binzhou People's Hospital (Shandong, China). Immunohistochemistry was used to detect the expression levels of EpCAM and ß-catenin proteins in these tissues, and the prognoses of the patients from whom the samples were derived were determined on follow-up examination. The corresponding in vitro mechanistic siRNA experiments were subsequently performed in the human colon cancer cell line HCT116 to observe the regulatory effects of silencing EpCAM expression on the Wnt/ß-catenin pathway. From these analyses, we determined that the expression levels of EpCAM and ß-catenin were higher in cancer tissues compared with other tissues from the same patient, and that the expression of EpCAM and Wnt/ß- catenin in colon cancers were positively correlated. The prognostic analysis showed an inverse correlation between EpCAM and Wnt/ß- catenin expression and patient prognosis. A further examination of cellular mechanisms confirmed that the silencing of EpCAM led to decreased expression of Wnt/ß-catenin, and thus reduced proliferation and increased the apoptosis ratio in the cells. These results suggest that suppression of EpCAM might be a new approach for treating colon cancer.

The proliferative and migratory effects of physical injury and stromal cell-derived factor-1α on rat cardiomyocytes and fibroblasts.

OBJECTIVE: This study aims to explore the effects of physical injury and stromal cell-derived factor-1α (SDF-1α) on the proliferation of cardiomyocytes and chemotactic effects of cardiomyocytes on the migration of cardiac fibroblasts. MATERIALS AND METHODS: Isolation and primary culture of rat cardiomyocytes and cardiac fibroblasts were performed; scratching was employed to induce physical injury on cells which were cultured with SDF-1α at different concentrations; proliferation ability of cardiomyocytes was checked with CCK-8 assay and migratory ability of cardiac fibroblasts under the chemotaxis of cardiomyocytes was detected with Transwell assay. RESULTS: SDF-1α enhanced the proliferation ability of cardiomyocytes with physical injury, especially at the concentration of 80 µg/L when the proliferation rate of cardiomyocytes increased most markedly. Moreover, physically injured cardiomyocyte that was cultured with SDF-1α significantly elevated migratory ability of cardiac fibroblasts, which tended to be more obvious along with the chemotactic culture time. CONCLUSIONS: SDF-1α enhanced the proliferation ability of cardiomyocytes with physical injury, and physically injured cardiomyocyte that was cultured with SDF-1α promoted the migration of cardiac fibroblasts.

Rationally engineered nanoparticles target multiple myeloma cells, overcome cell-adhesion-mediated drug resistance, and show enhanced efficacy in vivo.

In the continuing search for effective cancer treatments, we report the rational engineering of a multifunctional nanoparticle that combines traditional chemotherapy with cell targeting and anti-adhesion functionalities. Very late antigen-4 (VLA-4) mediated adhesion of multiple myeloma (MM) cells to bone marrow stroma confers MM cells with cell-adhesion-mediated drug resistance (CAM-DR). In our design, we used micellar nanoparticles as dynamic self-assembling scaffolds to present VLA-4-antagonist peptides and doxorubicin (Dox) conjugates, simultaneously, to selectively target MM cells and to overcome CAM-DR. Dox was conjugated to the nanoparticles through an acid-sensitive hydrazone bond. VLA-4-antagonist peptides were conjugated via a multifaceted synthetic procedure for generating precisely controlled number of targeting functionalities. The nanoparticles were efficiently internalized by MM cells and induced cytotoxicity. Mechanistic studies revealed that nanoparticles induced DNA double-strand breaks and apoptosis in MM cells. Importantly, multifunctional nanoparticles overcame CAM-DR, and were more efficacious than Dox when MM cells were cultured on fibronectin-coated plates. Finally, in a MM xenograft model, nanoparticles preferentially homed to MM tumors with ∼10 fold more drug accumulation and demonstrated dramatic tumor growth inhibition with a reduced overall systemic toxicity. Altogether, we demonstrate the disease driven engineering of a nanoparticle-based drug delivery system, enabling the model of an integrative approach in the treatment of MM.

A novel cytotoxic T lymphocyte epitope analogue with enhanced activity derived from cyclooxygenase-2.

Cyclooxygenase-2 is a promising target for cancer immunotherapy. Here, we designed the analogues p321-9L and p321-1Y9L (YLIGETIKL) from cyclooxygenase-2-derived native peptide p321. Then, we tested the binding affinity and stability of the analogues and their ability to elicit specific immune response both in vitro (from PBMCs of HLA-A*02⁺ healthy donors) and in vivo (from HLA-A2.1/K(b) transgenic mice). Our results indicated that the activity of cytotoxic T lymphocytes induced by p321-9L and p321-1Y9L was more potent than that of p321. In conclusion, the epitope analogue, especially p321-1Y9L, may be a good candidate which could be used to the immunotherapy of patients with tumours expressing cyclooxygenase-2.

Microstructure and antibacterial property of in situ TiO(2) nanotube layers/titanium biocomposites.

The TiO(2) nanotube layer was in situ synthesized on the surface of pure titanium by the electrochemical anodic oxidation. The diameter of nano- TiO(2) nanotubes was about 70~100 nm. The surface morphology and phase compositions of TiO(2) nanotube layers were observed and analyzed using the scanning electron microscope (SEM). The important processing parameters, including anodizing voltage, reaction time, concentration of electrolyte, were optimized in more detail. The photocatalytic activity of the nano- TiO(2) nanotube layers prepared with optimal conditions was evaluated via the photodegradation of methylthionine in aqueous solution. The antibacterial property of TiO(2) nanotube layers prepared with optimal conditions was evaluated by inoculating Streptococcus mutans on the TiO(2) nanotube layers in vitro. The results showed that TiO(2) nanotube layers/Ti biocomposites had very good antibacterial activity to resist Streptococcus mutans. As a dental implant biomaterial, in situ TiO(2) nanotube layer/Ti biocomposite has better and wider application prospects.

Identification of a novel CD8+ T cell epitope derived from cancer-testis antigen MAGE-4 in oesophageal carcinoma.

MAGE-4 is considered as an attractive cancer-testis (CT) antigen for tumour immunotherapy, and it is overexpressed in oesophageal carcinoma (EC). To identify MAGE-4-derived HLA-A2 restricted epitopes, native peptides and their analogues were predicted with prediction programs. The native peptide, p286 (KVLEHVVRV), and its analogues, p286-1Y2L and p286-1Y2L9L, showed potent binding affinity and stability towards HLA-A*0201 molecule. Cytotoxic T lymphocytes (CTLs) induced by p286-1Y2L9L could release IFN-γ in ELISPOT assay. In cytotoxicity assay, p286-1Y2L9L showed the capability to induce specific CTLs which could lyse the target cancer cells from both PBMCs of healthy donors and HLA-A2.1/K(b) transgenic mice. Our results indicated that the peptide p286-1Y2L9L could serve as a novel candidate epitope to develop peptide vaccines against oesophageal carcinoma.

Genomic organization, alternative splicing and tissues expression of porcine CREB3L4 gene.

CREB3L4 (cAMP response element binding protein3 like 4) belongs to mammalian CREB/ATF subfamily transcription factors featuring a unique putative transmembrane domain lined to the bZIP region in their C-terminals. We report here the cloning of porcine CREB3L4 and its alternative splicing variant. The open reading frame of normal CREB3L4 covers 1,188 bp and encodes a 395-amino acid polypeptide, whereas its variant encodes a C-terminal truncated protein comprising only 271 amino acids. The genomic sequence of porcine CREB3L4 spans approximately 6 kb consisted of ten exons and nine introns, and maps closely to Jumping translocation breakpoint gene in a head-to-head manner on the q arm of Sus Scrofa chromosome 4. Tissue expression analysis by RT-PCR indicates that normal porcine CREB3L4 is ubiquitously expressed with relatively high abundance in stomach, liver, cerebellum, and is a predominant form in various tissues, whereas the splicing variant is expressed at extremely low level in all examined tissues. Our study will lay the groundwork for the further investigation on the physiological function of CREB3L4 in pig models.

[Nphe1]nociceptin(1-13)-NH2 antagonizes nociceptin-induced hypotension, bradycardia, and hindquarters vasodilation in the anesthetized rat.

The purpose of this study was to investigate the effects of [Nphe1]nociceptin(1-13)-NH2 on nociceptin-induced decreases in mean arterial pressure (MAP), heart rate (HR), and hindquarters vascular bed resistance (HVBR) of the anesthetized rat. The results showed that i.c.v. or i.v. [Nphe1]nociceptin(1-13)-NH2 (1.5-12 nmol/kg and 5-120 nmol/kg, respectively) could antagonize the depressor effects of i.c.v. or i.v. nociceptin (3 and 30 nmol/kg, respectively) on MAP and HR. Furthermore, [Nphe1]nociceptin(1-13)-NH2 (5-120 nmol/kg) could reverse nociceptin (30 nmol/kg)-induced decrease of HVBR. However, [Nphe1]nociceptin(1-13)-NH2 had no significant effects on similar effects induced by morphine. Our results suggest that [Nphe1]nociceptin(1-13)-NH2 acts as a selective antagonist of the nociceptin receptor in the cardiovascular system of the rat.

Association of bovine papillomavirus type 1 with microtubules.

Transport of BPV-1 virus from the cell membrane to the nucleus was studied in vitro in CV-1 cells. At reduced temperature (4 degrees C), BPV-1 binding to CV-1 cells was unaffected but there was no transport of virions across the cytosol. Electron microscopy showed BPV-1 virions in association with microtubules in the cytoplasm, a finding confirmed by co-immunoprecipitation of L1 protein and tubulin. Internalization of virus was unimpaired in cells treated with the microtubule-depolymerizing drug nocodazole but virions were retained in cytoplasmic vesicles and not transported to the nucleus. We conclude that a microtubule transport mechanism in CV-1 cells moves intact BPV-1 virions from the cell surface to the nuclear membrane.

Type specific and genotype cross reactive B epitopes of the L1 protein of HPV16 defined by a panel of monoclonal antibodies.

Mouse monoclonal antibodies (mAbs) were raised against the major capsid protein, L1, of human papillomavirus type 16 (HPV16), produced in Escherichia coli with the expression plasmid pTrcL1. Epitope specificity could be assigned to 11 of these 12 antibodies using a series of linear peptides and fusion proteins from HPV16. One mAb (MC53) recognized a novel linear epitope that appears to be unique to the HPV16 genotype. A further 11 mAbs were characterized as recognizing novel and previously defined linear and conformational epitopes shared among more than one HPV genotype. The apparently genotype specific mAb could be useful for the development of diagnostic tests for vegetative virus infection in clinical specimens.

Mucosal immunisation with papillomavirus virus-like particles elicits systemic and mucosal immunity in mice.

It has been shown previously that recombinant virus-like particles (VLPs) of papillomavirus can induce VLP-specific humoral and cellular immune responses following parenteral administration. To test whether mucosal administration of bovine papillomavirus type 1 (BPV1) VLPs could produce mucosal as well as systemic immune responses to VLPs, 50 micrograms chimeric BPV1 VLPs containing an HPV16 E7 CTL epitope (BPVL1/E7 VLP) was administered intranasally to mice. After two immunisations, L1-specific serum IgG and IgA were observed. L1-specific IgG and IgA were also found in respiratory and vaginal secretions. Both serum and mucosal antibody inhibited papillomavirus VLP-induced agglutination of RBC, indicating that the antibody induced by mucosal immunisation may recognize conformational determinants associated with virus neutralisation. For comparison, VLPs were given intramuscularly, and systemic and mucosal immune responses were generally comparable following systemic or mucosal delivery. However, intranasal administration of VLP induced significantly higher local IgA response in lung, suggesting that mucosally delivered HPV VLP may be more effective for mediating local mucosal immune responses. Intranasal immunisation with HPV6b L1 VLP produced VLP-specific T proliferative responses in splenocytes, and immunisation with BPVL1 VLP containing an HPV16 E7 CTL epitope induced E7-specific CTL responses. We conclude that immunisation with papillomavirus VLPs via mucosal and intramuscular routes, without adjuvant, can elicit specific antibody at mucosal surfaces and also systemic VLP epitope specific T cell responses. These findings suggest that mucosally delivered VLPs may offer an alternative HPV VLP vaccine strategy for inducing protective humoral immunity to anogenital HPV infection, together with cell-mediated immune responses to eliminate any cells which become infected.

Identification of the alpha6 integrin as a candidate receptor for papillomaviruses.

Papillomaviruses (PVs) bind in a specific and saturable fashion to a range of epithelial and other cell lines. Treatment of cells with trypsin markedly reduces their ability to bind virus particles, suggesting that binding is mediated via a cell membrane protein. We have investigated the interaction of human PV type 6b L1 virus-like particles (VLPs) with two epithelial cell lines, CV-1 and HaCaT, which bind VLPs, and a B-cell line (DG75) previously shown not to bind VLPs. Immunoprecipitation of a mixture of PV VLPs with [35S]methionine-labeled cell extracts and with biotin-labeled cell surface proteins identified four proteins from CV-1 and HaCaT cells of 220, 120, 87, and 35 kDa that reacted with VLPs and were not present in DG75 cells. The alpha6beta4 integrin complex has subunits corresponding to the VLP precipitated proteins, and the tissue distribution of this complex suggested that it was a candidate human PV receptor. Monoclonal antibodies (MAbs) to the alpha6 or beta4 integrin subunits precipitated VLPs from a mixture of CV-1 cell proteins and VLPs, whereas MAbs to other integrin subunits did not. An alpha6 integrin-specific MAb (GoH3) inhibited VLP binding to CV-1 and HaCaT cells, whereas an anti-beta4 integrin MAb and a range of integrin-specific and other MAbs did not. Furthermore, human laminin, the natural ligand for the alpha6beta4 integrin, was able to block VLP binding. By use of sections of monkey esophagus, the distribution of alpha6 integrin expression in the basal epithelium was shown to coincide with the distribution of bound VLPs. Taken together, these data suggest that VLPs bind specifically to the alpha6 integrin subunit and that integrin complexes containing alpha6 integrin complexed with either beta1 or beta4 integrins may act as a receptor for PV binding and entry into epithelial cells.

Epithelial cells display separate receptors for papillomavirus VLPs and for soluble L1 capsid protein.

We examined the distribution of putative receptors for papillomavirus (PV) capsid proteins on various cell types, using either Hexahis HPV6b L1 fusion protein or synthetic HPV6b virus-like particles (VLPs). Specific, saturable binding of VLPs to CV-1 cells was demonstrated using 35S-labeled VLPs, with an average receptor number of 1 x 10(4)/cell and a binding affinity constant (Ka) of 4 x 10(7) M. VLP binding was quantitated by flow cytometry using a monoclonal antibody to the L1 capsid protein. Intense staining of epithelial and mesenchymal cells was observed. Some immature bone marrow-derived cells bound VLPs weakly, while the majority of B lymphoma cells demonstrated no binding. Binding to 12 of 16 VLP receptor positive cell lines was abolished by trypsin pretreatment of cells. Removal of cellular sialic acid or O-linked oligosaccharides separately did not affect VLP binding, which was enhanced about 25% when cells were pretreated with both neuraminidase and O-glycosidase. Culture of cells with sufficient tunicamycin to inhibit Concanavalin A binding did not diminish the binding of VLPs. Denatured L1 protein, either from VLPs or expressed from Escherichia coli as a Hexahis fusion protein, bound to a trypsin-resistant structure on a range of cell types and did not block the binding of VLPs to cells. Dual-fluorescence assay with a Burkitt lymphoma line BL72 demonstrated that Hexahis L1 protein and VLPs bind to separate cell surface molecules on BL72 cells. We conclude that the first binding of PV virus to cells is via a widely distributed membrane protein receptor(s) and that subsequent processing of particles may involve other non-trypsin-sensitive structure(s) also displayed on the cell membrane.