Mucosotropic, high-risk human papillomaviruses (HPV) are sexually transmitted viruses that are causally associated with the development of cervical cancer. The most common high-risk genotype, HPV16, is an obligatory intracellular virus that must gain entry into host epithelial cells and deliver its double stranded DNA to the nucleus. HPV capsid proteins play a vital role in these steps. Despite the critical nature of these capsid protein-host cell interactions, the precise cellular components necessary for HPV16 infection of epithelial cells remains unknown. Several neutralizing epitopes have been identified for the HPV16 L2 minor capsid protein that can inhibit infection after initial attachment of the virus to the cell surface, which suggests an L2-specific secondary receptor or cofactor is required for infection, but so far no specific L2-receptor has been identified. Here, we demonstrate that the annexin A2 heterotetramer (A2t) contributes to HPV16 infection and co-immunoprecipitates with HPV16 particles on the surface of epithelial cells in an L2-dependent manner. Inhibiting A2t with an endogenous annexin A2 ligand, secretory leukocyte protease inhibitor (SLPI), or with an annexin A2 antibody significantly reduces HPV16 infection. With electron paramagnetic resonance, we demonstrate that a previously identified neutralizing epitope of L2 (aa 108–120) specifically interacts with the S100A10 subunit of A2t. Additionally, mutation of this L2 region significantly reduces binding to A2t and HPV16 pseudovirus infection. Furthermore, downregulation of A2t with shRNA significantly decreases capsid internalization and infection by HPV16. Taken together, these findings indicate that A2t contributes to HPV16 internalization and infection of epithelial cells and this interaction is dependent on the presence of the L2 minor capsid protein.

of the lower extremity are often misdiagnosed as cellulitis (aka "pseudocellulitis") and treated with antibiotics and/or hospitalization. There is limited data on the cost and complications from misdiagnosed cellulitis. OBJECTIVE To characterize the national health care burden of misdiagnosed cellulitis in patients admitted for treatment of lower extremity cellulitis. DESIGN, SETTING, AND PARTICIPANTSCross-sectional study using patients admitted from the emergency department (ED) of a large urban hospital with a diagnosis of lower extremity cellulitis between June 2010 and December 2012. Patients who were discharged with a diagnosis of cellulitis were categorized as having cellulitis, while those who were given an alternative diagnosis during the hospital course, on discharge, or within 30 days of discharge were considered to have pseudocellulitis. A literature review was conducted for calculation of large-scale costs and complication rates. We obtained national cost figures from the Medical Expenditure Panel Survey (MEPS), provided by the Agency for Healthcare Research and Quality (AHRQ) for 2010 to calculate the hospitalization costs per year attributed to misdiagnosed lower extremity pseudocellulitis.EXPOSURES The exposed group was composed of patients who presented to and were admitted from the ED with a diagnosis of lower extremity cellulitis. MAIN OUTCOMES AND MEASURESPatient characteristics, hospital course, and complications during and after hospitalization were reviewed for each patient, and estimates of annual costs of misdiagnosed cellulitis in the United States. RESULTSOf 259 patients, 79 (30.5%) were misdiagnosed with cellulitis, and 52 of these misdiagnosed patients were admitted primarily for the treatment of cellulitis. Forty-four of the 52 (84.6%) did not require hospitalization based on ultimate diagnosis, and 48 (92.3%) received unnecessary antibiotics. We estimate cellulitis misdiagnosis leads to 50 000 to 130 000 unnecessary hospitalizations and $195 million to $515 million in avoidable health care spending. Unnecessary antibiotics and hospitalization for misdiagnosed cellulitis are projected to cause more than 9000 nosocomial infections, 1000 to 5000 Clostridium difficile infections, and 2 to 6 cases of anaphylaxis annually.CONCLUSIONS AND RELEVANCE Misdiagnosis of lower extremity cellulitis is common and may lead to unnecessary patient morbidity and considerable health care spending.

Human papillomaviruses (HPVs) infect epithelia and can lead to the development of lesions, some of which have malignant potential. HPV type 16 (HPV16) is the most oncogenic genotype and causes various types of cancer, including cervical, anal, and head and neck cancers. However, despite significant research, our understanding of the mechanism by which HPV16 binds to and enters host cells remains fragmented. Over several decades, many HPV receptors and entry pathways have been described. This review puts those studies into context and offers a model of HPV16 binding and entry as a framework for future research. Our model suggests that HPV16 binds to heparin sulfate proteoglycans (HSPGs) on either the epithelial cell surface or basement membrane through interactions with the L1 major capsid protein. Growth factor receptors may also become activated through HSPG/growth factor/HPV16 complexes that initiate signaling cascades during early virion-host cell interactions. After binding to HSPGs, the virion undergoes conformational changes, leading to isomerization by cyclophilin B and proprotein convertasemediated L2 minor capsid protein cleavage that increases L2 N terminus exposure. Along with binding to HSPGs, HPV16 binds to ␣6 integrins, which initiate further intracellular signaling events. Following these primary binding events, HPV16 binds to a newly identified L2-specific receptor, the annexin A2 heterotetramer. Subsequently, clathrin-, caveolin-, lipid raft-, flotillin-, cholesterol-, and dynamin-independent endocytosis of HPV16 occurs. Since the discovery of human papillomaviruses (HPVs), researchers in the field have sought to identify the mechanism by which these viruses enter host cells. Although much work has been done to date and many possible receptors have been identified, a clearly defined description of the entry of HPVs has remained controversial. In many cases of viral infection, our understanding of simple binding and uptake through a singular mechanism has given way to a model of a more complex interaction between several specific receptors, coreceptors, and cofactors (1-3). The purpose of this review is to synthesize the known data regarding HPV type 16 (HPV16) binding proteins at the cell surface, and their associated molecules, and attempt to connect them, if possible, into a testable framework of binding and entry. Due to the fact that HPVs are a diverse group of over 150 viruses, this review focuses primarily on the most common of the cancer-causing genotypes, HPV16, while making it clear when non-HPV16 genotypes are reviewed. The development of several HPV particle production systems has allowed researchers to begin to delineate the mechanisms behind viral entry; however, important differences between particles developed in vitro made direct comparisons challenging. Therefore, not only HPV16 structure but also the multiple forms the virus structure takes in the laboratory are discussed below. Finally, due to the tropism of HPV16 for human epithelial cells during a natural infection, this rev...

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