Current In Vitro and In Vivo Models to Study MCPyV-Associated MCC.

Merkel cell polyomavirus (MCPyV) is the only human polyomavirus currently known to cause human cancer. MCPyV is believed to be an etiological factor in at least 80% of cases of the rare but aggressive skin malignancy Merkel cell carcinoma (MCC). In these MCPyV+ MCC tumors, clonal integration of the viral genome results in the continued expression of two viral proteins: the viral small T antigen (ST) and a truncated form of the viral large T antigen. The oncogenic potential of MCPyV and the functional properties of the viral T antigens that contribute to neoplasia are becoming increasingly well-characterized with the recent development of model systems that recapitulate the biology of MCPyV+ MCC. In this review, we summarize our understanding of MCPyV and its role in MCC, followed by the current state of both in vitro and in vivo model systems used to study MCPyV and its contribution to carcinogenesis. We also highlight the remaining challenges within the field and the major considerations related to the ongoing development of in vitro and in vivo models of MCPyV+ MCC.

A Novel In Vitro Culture Model System to Study Merkel Cell Polyomavirus-Associated MCC Using Three-Dimensional Organotypic Raft Equivalents of Human Skin.

Merkel cell polyomavirus (MCPyV) is a human polyomavirus causally linked to the development of Merkel cell carcinoma (MCC), an aggressive malignancy that largely arises within the dermis of the skin. In this study, we recapitulate the histopathology of human MCC tumors in vitro using an organotypic (raft) culture system that is traditionally used to recapitulate the dermal and epidermal equivalents of skin in three dimensions (3D). In the optimal culture condition, MCPyV+ MCC cells were embedded in collagen between the epidermal equivalent comprising human keratinocytes and a dermal equivalent containing fibroblasts, resulting in MCC-like lesions arising within the dermal equivalent. The presence and organization of MCC cells within these dermal lesions were characterized through biomarker analyses. Interestingly, co-culture of MCPyV+ MCC together with keratinocytes specifically within the epidermal equivalent of the raft did not reproduce human MCC morphology, nor were any keratinocytes necessary for MCC-like lesions to develop in the dermal equivalent. This 3D tissue culture system provides a novel in vitro platform for studying the role of MCPyV T antigens in MCC oncogenesis, identifying additional factors involved in this process, and for screening potential MCPyV+ MCC therapeutic strategies.

Stress keratin 17 enhances papillomavirus infection-induced disease by downregulating T cell recruitment.

High-risk human papillomaviruses (HPVs) cause 5% of human cancers. Despite the availability of HPV vaccines, there remains a strong urgency to find ways to treat persistent HPV infections, as current HPV vaccines are not therapeutic for individuals already infected. We used a mouse papillomavirus infection model to characterize virus-host interactions. We found that mouse papillomavirus (MmuPV1) suppresses host immune responses via overexpression of stress keratins. In mice deficient for stress keratin K17 (K17KO), we observed rapid regression of papillomas dependent on T cells. Cellular genes involved in immune response were differentially expressed in the papillomas arising on the K17KO mice correlating with increased numbers of infiltrating CD8+ T cells and upregulation of IFNγ-related genes, including CXCL9 and CXCL10, prior to complete regression. Blocking the receptor for CXCL9/CXCL10 prevented early regression. Our data provide a novel mechanism by which papillomavirus-infected cells evade host immunity and defines new therapeutic targets for treating persistent papillomavirus infections.

Characteristics and Risk Factors for Mortality in Paediatric In-Hospital Cardiac Events in Singapore: Retrospective Single Centre Experience.

Introduction: There is limited data on paediatric resuscitation outcomes in Asia. We aimed to describe outcomes of paediatric in-hospital cardiac arrests (IHCA) and peri-resuscitation factors associated with mortality in our institution. Materials and Methods: Using data from our hospital's code registry from 2009 to 2014, we analysed all patients younger than 18 years of age with IHCA who required cardiopulmonary resuscitation (CPR). Exposure variables were obtained from clinical demographics, CPR and post-resuscitation data. Outcomes measured were: survival after initial CPR event and survival to hospital discharge. We analysed categorical and continuous variables with Fisher's exact and Wilcoxon rank- sum tests respectively. Statistical significance was taken as P <0.05. Results: We identified 51 patients in the study period. Median age of patients was 1.9 (interquartile range [IQR]: 0.3, 5.5) years. Twenty-six (51%) patients had bradycardia as the first-recorded rhythm. The most common pre-existing medical condition was respiratory-related (n = 25, 48%). Thirty-eight (75%) achieved sustained return of spontaneous circulation, 24 (47%) survived to paediatric intensive care unit (PICU) discharge and 23 (45%) survived to hospital discharge. Risk factors for hospital mortality included: age, duration of CPR, adrenaline, calcium or bicarbonate administration during CPR, Paediatric Index of Mortality (PIM)- II scores, first recorded post-resuscitation pH and hyperglycaemia within 24 hours of resuscitation. Conclusion: We demonstrated an association between clinical demographics (age, PIM-II scores), CPR variables (duration of CPR and administration of adrenaline, calcium or bicarbonate) and post-resuscitation laboratory results (first recorded pH and hyperglycaemia within 24 hours) with PICU survival. The availability and quality of post- resuscitation care may have implications on survival after paediatric IHCA.