HPV16 infection of HaCaTs is dependent on β4 integrin, and α6 integrin processing

Molecular aspects of cervical cancer: a pathogenesis update

Cervical cancer (CC) is a significant health problem, especially in low-income countries. Functional studies on the human papillomavirus have generated essential advances in the knowledge of CC. However, many unanswered questions remain. This mini-review discusses the latest results on CC pathogenesis, HPV oncogenesis, and molecular changes identified through next-generation technologies. Interestingly, the percentage of samples with HPV genome integrations correlates with the degree of the cervical lesions, suggesting a role in the development of CC. Also, new functions have been described for the viral oncoproteins E5, E6, and E7, resulting in the acquisition and maintenance of cancer hallmarks, including proliferation, immune response evasion, apoptosis, and genomic instability. Remarkably, E5 oncoprotein affects signaling pathways involved in the expression of interferon-induced genes and EGFR-induced proliferation, while E6 and E7 oncoproteins regulate the DNA damage repair and cell cycle continuity pathways. Furthermore, next-generation technologies provide vast amounts of information, increasing our knowledge of changes in the genome, transcriptome, proteome, metabolome, and epigenome in CC. These studies have identified novel molecular traits associated with disease susceptibility, degree of progression, treatment response, and survival as potential biomarkers and therapeutic targets.

Identification of immune infiltration and immune-related biomarkers of periprosthetic joint infection

Background

The immune response associated with periprosthetic joint infection (PJI) is an emerging but relatively unexplored topic. The aim of this study was to investigate immune cell infiltration in periprosthetic tissues and identify potential immune-related biomarkers.

Methods

The GSE7103 dataset from the GEO database was selected as the data source. Differentially expressed genes (DEGs) and significant modular genes in weighted correlation network analysis (WGCNA) were identified. Functional enrichment analysis and transcription factor prediction were performed on the overlapping genes. Next, immune-related genes from the ImmPort database were matched. The protein-protein interaction (PPI) analysis was performed to identify hub genes. CIBERSORTx was used to evaluate the immune cell infiltration pattern. Spearman correlation analysis was used to evaluate the relationship between hub genes and immune cells.

Results

A total of 667 DEGs were identified between PJI and control samples, and 1847 PJI-related module genes were obtained in WGCNA. Enrichment analysis revealed that the common genes were mainly enriched in immune and host defense-related terms. TFEC, SPI1, and TWIST2 were the top three transcription factors. Three hub genes, SDC1, MMP9, and IGF1, were identified in the immune-related PPI network. Higher levels of plasma cells, CD4+ memory resting T cells, follicular helper T cells, resting mast cells, and neutrophils were found in the PJI group, while levels of M0 macrophages were lower. Notably, the expression of all three hub genes correlated with the infiltration levels of seven types of immune cells.

Conclusion

The present study revealed immune infiltration signatures in the periprosthetic tissues of PJI patients. SDC1, MMP9, and IGF1 were potential immune-related biomarkers for PJI.

Myosin 9 and N-glycans jointly regulate human papillomavirus entry

Persistent high-risk HPV infection is closely associated with cervical cancer development, and there is no drug targeting HPV on the market at present, so it is particularly important to understand the interaction mechanism between HPV and the host which may provide the novel strategies for treating HPV diseases. HPV can hijack cell surface heparan sulfate proteoglycans (HSPGs) as primary receptors. However, the secondary entry receptors for HPV remain elusive. We identify myosin-9 (NMHC-IIA) as a host factor that interacts with HPV L1 protein and mediates HPV internalization. Efficient HPV entry required myosin-9 redistribution to the cell surface regulated by HPV-hijacked MEK-MLCK signaling. Myosin-9 maldistribution by ML-7 or ML-9 significantly inhibited HPV pseudoviruses infection in vitro and in vivo. Meanwhile, N-glycans, especially the galactose chains, may act as the decoy receptors for HPV, which can block the interaction of HPV to myosin-9 and influence the way of HPV infection. Taken together, we identify myosin-9 as a novel functional entry receptor for high-risk HPV both in vitro and in vivo, and unravel the new roles of myosin-9 and N-glycans in HPV entry, which provides the possibilities for host targets of antiviral drugs.

The clinical development of antibody-drug conjugates for non-small cell lung cancer therapy

Despite the emergence of molecular targeted therapy and immune checkpoint inhibitors as standard first-line treatments for non-small cell lung cancer (NSCLC), their efficacy in some patients is limited by intrinsic and acquired resistance. Antibody-drug conjugates (ADCs), a revolutionary class of antitumor drugs, have displayed promising clinical outcomes in cancer treatment. In 2022, trastuzumab deruxtecan (Enhertu) was approved for treating HER2-mutated NSCLC, thereby underscoring the clinical value of ADCs in NSCLC treatment strategies. An increasing number of ADCs, focusing on NSCLC, are undergoing clinical trials, potentially positioning them as future treatment options. In this review, we encapsulate recent advancements in the clinical research of novel ADCs for treating NSCLC. Subsequently, we discuss the mechanisms of action, clinical efficacy, and associated limitations of these ADCs.

Viruses Binding to Host Receptors Interacts with Autophagy

Viruses must cross the plasma membrane to infect cells, making them eager to overcome this barrier in order to replicate in hosts. They bind to cell surface receptors as the first step of initiating entry. Viruses can use several surface molecules that allow them to evade defense mechanisms. Various mechanisms are stimulated to defend against viruses upon their entry into cells. Autophagy, one of the defense systems, degrades cellular components to maintain homeostasis. The presence of viruses in the cytosol regulates autophagy; however, the mechanisms by which viral binding to receptors regulates autophagy have not yet been fully established. This review discusses recent findings on autophagy induced by interactions between viruses and receptors. It provides novel perspectives on the mechanism of autophagy as regulated by viruses.

Recent Advances in Our Understanding of the Infectious Entry Pathway of Human Papillomavirus Type 16

Papillomaviruses are a diverse viral species, but several types such as HPV16 are given special attention due to their contribution towards the pathogenesis of several major cancers. In this review, we will summarize how the knowledge of HPV16 entry has expanded since the last comprehensive HPV16 entry review our lab published in 2017.

How DNA and RNA Viruses Exploit Host Chaperones to Promote Infection

To initiate infection, a virus enters a host cell typically via receptor-dependent endocytosis. It then penetrates a subcellular membrane, reaching a destination that supports transcription, translation, and replication of the viral genome. These steps lead to assembly and morphogenesis of the new viral progeny. The mature virus finally exits the host cell to begin the next infection cycle. Strikingly, viruses hijack host molecular chaperones to accomplish these distinct entry steps. Here we highlight how DNA viruses, including polyomavirus and the human papillomavirus, exploit soluble and membrane-associated chaperones to enter a cell, penetrating and escaping an intracellular membrane en route for infection. We also describe the mechanism by which RNA viruses—including flavivirus and coronavirus—co-opt cytosolic and organelle-selective chaperones to promote viral endocytosis, protein biosynthesis, replication, and assembly. These examples underscore the importance of host chaperones during virus infection, potentially revealing novel antiviral strategies to combat virus-induced diseases.

Design, modeling and 3D printing of a personalized cervix tissue implant with protein release function

Cervical cancer induced by human papillomavirus (HPV) causes severe morbidity worldwide. Although cervical conization has been widely accepted as the most conventional surgery against cervical cancer, tissue defects and high recurrence rates have a significant negative impact on women's mental and physical health. Herein we developed an implantable, personalized cervical implant with drug release function using 3D printing technology. The cervical implant was designed in cone-shape with hieratical porous structures according to the clinical data, 3D-printed using polyurethane by low-temperature deposition manufacturing (LDM), and finished by lyophilization. Anti-HPV protein was loaded into the porous structure under negative pressure afterwards. Elastic biomedical polyurethane and the porous structure ensured that these cervical implants were equipped with tailored mechanical properties comparable to physiological cervix tissue. Cytotoxicity and cytocompatibility tests indicated that these 3D-printed cervical implants supported cell adhesion and growth. More importantly, the cervical implants with regulated pores could help to quantitatively control the loading and release of anti-HPV protein to inhibit dissociative viruses near the cervix validly. As a result, the 3D-printed cervical implants in the present study showed considerable potential for use as functional tissue implants against HPV infection after cervical conization.

A vaccine-based nanosystem for initiating innate immunity and improving tumor immunotherapy

The unsatisfactory response rate of immune checkpoint blockade (ICB) immunotherapy severely limits its clinical application as a tumor therapy. Here, we generate a vaccine-based nanosystem by integrating siRNA for Cd274 into the commercial human papillomavirus (HPV) L1 (HPV16 L1) protein. This nanosystem has good biosafety and enhances the therapeutic response rate of anti-tumor immunotherapy. The HPV16 L1 protein activates innate immunity through the type I interferon pathway and exhibits an efficient anti-cancer effect when cooperating with ICB therapy. For both resectable and unresectable breast tumors, the nanosystem decreases 71% tumor recurrence and extends progression-free survival by 67%. Most importantly, the nanosystem successfully induces high response rates in various genetically modified breast cancer models with different antigen loads. The strong immune stimulation elicited by this vaccine-based nanosystem might constitute an approach to significantly improve current ICB immunotherapy.

Immune checkpoint blockade (ICB) immunotherapy efficacy has still limitations. Here, the authors generate a vaccine that integrates CD274 siRNA into the L1 protein of human papillomavirus, which cooperates with ICB by activating innate immunity in breast cancer models.

Anatomy of a viral entry platform differentially functionalized by integrins α3 and α6

During cell invasion, human papillomaviruses use large CD151 patches on the cell surface. Here, we studied whether these patches are defined architectures with features for virus binding and/or internalization. Super-resolution microscopy reveals that the patches are assemblies of closely associated nanoclusters of CD151, integrin α3 and integrin α6. Integrin α6 is required for virus attachment and integrin α3 for endocytosis. We propose that CD151 organizes viral entry platforms with different types of integrin clusters for different functionalities. Since numerous viruses use tetraspanin patches, we speculate that this building principle is a blueprint for cell-surface architectures utilized by viral particles.

Host receptors: the key to establishing cells with broad viral tropism for vaccine production

Cell culture-based vaccine technology is a flexible and convenient approach for vaccine production that requires adaptation of the vaccine strains to the new cells. Driven by the motivation to develop a broadly permissive cell line for infection with a wide range of viruses, we identified a set of the most relevant host receptors involved in viral attachment and entry. This identification was done through a review of different viral entry pathways and host cell lines, and in the context of the Baltimore classification of viruses. In addition, we indicated the potential technical problems and proposed some solutions regarding how to modify the host cell genome in order to meet industrial requirements for mass production of antiviral vaccines. Our work contributes to a finer understanding of the importance of breaking the host–virus recognition specificities for the possibility of creating a cell line feasible for the production of vaccines against a broad spectrum of viruses.

NRF2, p53, and p16: Predictive biomarkers to stratify human papillomavirus associated head and neck cancer patients for de-escalation of cancer therapy

Patients with HPV associated (HPV^+ve) head and neck squamous cell carcinoma (HNSCC), particularly oropharyngeal cancer, show better treatment response, higher survival rates, and lower risks of recurrence as compared to HPV^-ve HNSCC patients. Despite increased sensitivity to treatment modality, HPV^+ve HNSCC patients are subjected to the same intensive anti-cancer therapy as HPV^-ve HNSCC patients and thus subjecting them to unwarranted long-term toxicity. To identify predictive biomarkers for risk-stratification, we have analyzed the mutational spectrum, and the evidence suggests that gain-of-function mutations in the NRF2 pathway are highly prevalent in HPV^-ve HNSCC. At the same time, it is rare in HPV^+ve HNSCC tumors. We have reviewed the importance of gain-of-NRF2 function and loss of p53 in the prognosis of HNSCC patients and discussed a predictive scoring system using a combination of HPV status (p16), NRF2 pathway and p53 to stratify HPV^+ve HNSCC into good versus poor responders, which could immensely help in guiding future de-escalation treatment approaches in patients with HPV^+ve HNSCC.

The Underlying Mechanism of 3-Hydroxyphthalic Anhydride-Modified Bovine Beta-Lactoglobulin to Block Human Papillomavirus Entry Into the Host Cell

We have previously demonstrated that 3-hydroxyphthalic anhydride (3HP)-modified bovine beta-lactoglobulin (3HP-β-LG) is highly effective in inhibiting entry of pseudovirus (PsV) of high- and low-risk human papillomavirus (HPV) into the target cell. Intravaginally applied 3HP-β-LG-containing vaginal gel could significantly inhibit HPV infection and reduce viral load in the cervical region. However, we still do not understand the underlying molecular mechanism by which 3HP-β-LG is able to inhibit HPV infection. Here, though, we showed that 3HP-β-LG did not inactivate HPV PsV, but rather blocked entry of HPV PsV into the target cell via its interaction with virus, not cell. It bound to the positively charged region in the HPV L1 protein, suggesting that 3HP-β-LG binds to HPV L1 protein through the interaction between the negatively charged region in 3HP-β-LG and the positively charged region in HPV L1 protein, thus competitively blocking the binding of HPV to the receptor on the basement membrane in vaginal mucosa. Although 3HP-modified chicken ovalbumin (3HP-OVA) also carries high net negative charges, it exhibited no anti-HPV activity, suggesting that the interaction between 3HP-modified protein and HPV L1 protein relies on both electrostatic and matchable conformation of the binding sites in both proteins. When topically applied, 3HP-β-LG did not enter the host cell or blood circulation. These findings suggest that 3HP-β-LG targets HPV L1 protein and blocks HPV entry into the host cell, thus being safe and effective for topical application in the treatment of HPV infection.

Current strategies against persistent human papillomavirus infection (Review)

Human papillomavirus (HPV) is the most common sexually transmitted infection, exhibiting a tropism for the epidermis and mucosae. The link between persistent HPV infection and malignancies involving the anogenital tract as well as the head and neck has been well‑established, and it is estimated that HPV‑related cancers involving various anatomical sites account for 4.5% of all human cancers. Current prophylactic vaccines against HPV have enabled the prevention of associated malignancies. However, the sizeable population base of current infection in whom prophylactic vaccines are not applicable, certain high‑risk HPV types not included in vaccines, and the vast susceptible population in developing countries who do not have access to the costly prophylactic vaccines, put forward an imperative need for effective therapies targeting persistent infection. In this article, the life cycle of HPV, the mechanisms facilitating HPV evasion of recognition and clearance by the host immune system, and the promising therapeutic strategies currently under investigation, particularly antiviral drugs and therapeutic vaccines, are reviewed.

How non-enveloped viruses hijack host machineries to cause infection

Viruses must navigate the complex endomembranous network of the host cell to cause infection. In the case of a non-enveloped virus that lacks a surrounding lipid bilayer, endocytic uptake from the plasma membrane is not sufficient to cause infection. Instead, the virus must travel within organelle membranes to reach a specific cellular destination that supports exposure or arrival of the virus to the cytosol. This is achieved by viral penetration across a host endomembrane, ultimately enabling entry of the virus into the nucleus to initiate infection. In this review, we discuss the entry mechanisms of three distinct non-enveloped DNA viruses-adenovirus (AdV), human papillomavirus (HPV), and polyomavirus (PyV)-highlighting how each exploit different intracellular transport machineries and membrane penetration apparatus associated with the endosome, Golgi, and endoplasmic reticulum (ER) membrane systems to infect a host cell. These processes not only illuminate a highly-coordinated interplay between non-enveloped viruses and their host, but may provide new strategies to combat non-enveloped virus-induced diseases.

Genome-wide association study of cervical cancer suggests a role for ARRDC3 gene in human papillomavirus infection

The development of cervical cancer is initiated by human papillomavirus (HPV) infection and involves both viral and host genetic factors. Genome-wide association studies (GWAS) of cervical cancer have identified associations in the HLA locus and two loci outside HLA, but the principal genes that control infection and pathogenesis have not been identified. In the present study, we performed GWAS of cervical cancer in East Asian populations, involving 2609 cases and 4712 controls in the discovery stage and 1461 cases and 3295 controls in the follow-up stage. We identified novel-significant associations at 5q14 with the lead single nucleotide polymorphism (SNP) rs59661306 (P = 2.4 × 10-11) and at 7p11 with the lead SNP rs7457728 (P = 1.2 × 10-8). In 5q14, the chromatin region of the GWAS-significant SNPs was found to be in contact with the promoter of the ARRDC3 (arrestin domain-containing 3) gene. In our functional studies, ARRDC3 knockdown in HeLa cells caused significant reductions in both cell growth and susceptibility to HPV16 pseudovirion infection, suggesting that ARRDC3 is involved in the infectious entry of HPV into the cell. Our study advances the understanding of host genes that are responsible for cervical cancer susceptibility and guides future research on HPV infection and cancer development.

Papillomaviruses and Endocytic Trafficking

Endocytic trafficking plays a major role in transport of incoming human papillomavirus (HPVs) from plasma membrane to the trans Golgi network (TGN) and ultimately into the nucleus. During this infectious entry, several cellular sorting factors are recruited by the viral capsid protein L2, which plays a critical role in ensuring successful transport of the L2/viral DNA complex to the nucleus. Later in the infection cycle, two viral oncoproteins, E5 and E6, have also been shown to modulate different aspects of endocytic transport pathways. In this review, we highlight how HPV makes use of and perturbs normal endocytic transport pathways, firstly to achieve infectious virus entry, secondly to produce productive infection and the completion of the viral life cycle and, finally, on rare occasions, to bring about the development of malignancy.

Superinfection Exclusion between Two High-Risk Human Papillomavirus Types during a Coinfection

Superinfection exclusion is a common phenomenon whereby a single cell is unable to be infected by two types of the same pathogen. Superinfection exclusion has been described for various viruses, including vaccinia virus, measles virus, hepatitis C virus, influenza A virus, and human immunodeficiency virus. Additionally, the mechanism of exclusion has been observed at various steps of the viral life cycle, including attachment, entry, viral genomic replication, transcription, and exocytosis. Human papillomavirus (HPV) is the causative agent of cervical cancer. Recent epidemiological studies indicate that up to 50% women who are HPV positive (HPV⁺) are infected with more than one HPV type. However, no mechanism of superinfection exclusion has ever been identified for HPV. Here, we show that superinfection exclusion exists during a HPV coinfection and that it occurs on the cell surface during the attachment/entry phase of the viral life cycle. Additionally, we are able to show that the minor capsid protein L2 plays a role in this exclusion. This study shows, for the first time, that superinfection exclusion occurs during HPV coinfections and describes a potential molecular mechanism through which it occurs.IMPORTANCE Superinfection exclusion is a phenomenon whereby one cell is unable to be infected by multiple related pathogens. This phenomenon has been described for many viruses and has been shown to occur at various points in the viral life cycle. HPV is the causative agent of cervical cancer and is involved in other anogenital and oropharyngeal cancers. Recent epidemiological research has shown that up to 50% of HPV-positive individuals harbor more than one type of HPV. We investigated the interaction between two high-risk HPV types, HPV16 and HPV18, during a coinfection. We present data showing that HPV16 is able to block or exclude HPV18 on the cell surface during a coinfection. This exclusion is due in part to differences in the HPV minor capsid protein L2. This report provides, for the first time, evidence of superinfection exclusion for HPV and leads to a better understanding of the complex interactions between multiple HPV types during coinfections.

Subcellular Trafficking of the Papillomavirus Genome during Initial Infection: The Remarkable Abilities of Minor Capsid Protein L2

Since 2012, our understanding of human papillomavirus (HPV) subcellular trafficking has undergone a drastic paradigm shift. Work from multiple laboratories has revealed that HPV has evolved a unique means to deliver its viral genome (vDNA) to the cell nucleus, relying on myriad host cell proteins and processes. The major breakthrough finding from these recent endeavors has been the realization of L2-dependent utilization of cellular sorting factors for the retrograde transport of vDNA away from degradative endo/lysosomal compartments to the Golgi, prior to mitosis-dependent nuclear accumulation of L2/vDNA. An overview of current models of HPV entry, subcellular trafficking, and the role of L2 during initial infection is provided below, highlighting unresolved questions and gaps in knowledge.

HPV entry into cells

Human papillomavirus (HPV) is a sexually transmitted virus responsible for the development of cervical cancer, anal cancer, head and throat cancers, as well as genital area warts. A major focus of current HPV research is on preventing the virus from entering a cell and transferring its genetic material to the nucleus, thus potentially preventing the development of cancer. Although the available HPV vaccines are extremely successful, approximately 15 additional cancer-causing HPVs have been identified that the vaccines do not protect against. Therefore, roughly 150,000 cancer cases will not be prevented annually with the current vaccines. Research efforts focused on the basic cell biology of HPV infection have a goal of identifying common infectious events that may lead to inexpensive vaccines or anti-virals to prevent infection by most, if not all, HPVs. In this review we attempt to summarize what is known regarding the process of HPV binding, entry, and intracellular trafficking.

Gold-nanoparticles coated with the antimicrobial peptide esculentin-1a(1-21)NH2 as a reliable strategy for antipseudomonal drugs

Naturally occurring antimicrobial peptides (AMPs) hold promise as future therapeutics against multidrug resistant microorganisms. Recently, we have discovered that a derivative of the frog skin AMP esculentin-1a, Esc(1-21), is highly potent against both free living and biofilm forms of the bacterial pathogen Pseudomonas aeruginosa. However, bringing AMPs into clinics requires to overcome their low stability, high toxicity and inefficient delivery to the target site at high concentrations. Importantly, peptide conjugation to gold nanoparticles (AuNPs), which are among the most applied inorganic nanocarriers in biomedical sciences, represents a valuable strategy to solve these problems. Here we report that covalent conjugation of Esc(1-21) to soluble AuNPs [AuNPs@Esc(1-21)] via a poly(ethylene glycol) linker increased by ∼15-fold the activity of the free peptide against the motile and sessile forms of P. aeruginosa without being toxic to human keratinocytes. Furthermore, AuNPs@Esc(1-21) resulted to be significantly more resistant to proteolytic digestion and to disintegrate the bacterial membrane at very low concentration (5nM). Finally, we demonstrated for the first time the capability of peptide-coated AuNPs to display a wound healing activity on a keratinocytes monolayer. Overall, these findings suggest that our engineered AuNPs can serve as attractive novel biological-derived material for topical treatment of epithelial infections and healing of the injured tissue.

STATEMENT OF SIGNIFICANCE

Despite conjugation of AMPs to AuNPs represents a worthwhile solution to face some limitations for their development as new therapeutics, only a very limited number of studies is available on peptide-coated AuNPs. Importantly, this is the first report showing that a covalent binding of a linear AMP via a poly(ethylene glycol) linker to AuNPs highly enhances antipseudomonal activity, preserving the same mode of action of the free peptide, without being harmful. Furthermore, AuNPs@Esc(1-21) are expected to accelerate recovery of an injured skin layer. All together, these findings suggest our peptide-coated AuNPs as attractive novel nanoscale formulation to treat bacterial infections and to heal the injured tissue.

Human papillomavirus in oropharyngeal cancer: The changing face of a disease

The last decade has brought about an unexpected rise in oropharyngeal squamous cell carcinoma (OPSCC) primarily in white males from the ages of 40-55years, with limited exposure to alcohol and tobacco. This subset of squamous cell carcinoma (SCC) has been found to be associated with human papillomavirus infection (HPV). Other Head and Neck Squamous Cell carcinoma (HNSCC) subtypes include oral cavity, hypopharyngeal, nasopharyngeal, and laryngeal SCC which tend to be HPV negative. HPV associated oropharyngeal cancer has proven to differ from alcohol and tobacco associated oropharyngeal carcinoma in regards to the molecular pathophysiology, presentation, epidemiology, prognosis, and improved response to chemoradiation therapy. Given the improved survival of patients with HPV associated SCC, efforts to de-intensify treatment to decrease treatment related morbidity are at the forefront of clinical research. This review will focus on the important differences between HPV and tobacco related oropharyngeal cancer. We will review the molecular pathogenesis of HPV related oropharyngeal cancer with an emphasis on new paradigms for screening and treating this disease.

Furin Cleavage of L2 during Papillomavirus Infection: Minimal Dependence on Cyclophilins

Despite an abundance of evidence supporting an important role for the cleavage of minor capsid protein L2 by cellular furin, direct cleavage of capsid-associated L2 during human papillomavirus 16 (HPV16) infection remains poorly characterized. The conserved cleavage site, close to the L2 N terminus, confounds observation and quantification of the small cleavage product by SDS-PAGE. To overcome this difficulty, we increased the size shift by fusing a compact protein domain, the Propionibacterium shermanii transcarboxylase domain (PSTCD), to the N terminus of L2. The infectious PSTCD-L2 virus displayed an appreciable L2 size shift during infection of HaCaT keratinocytes. Cleavage under standard cell culture conditions rarely exceeded 35% of total L2. Cleavage levels were enhanced by the addition of exogenous furin, and the absolute levels of infection correlated to the level of L2 cleavage. Cleavage occurred on both the HaCaT cell surface and extracellular matrix (ECM). Contrary to current models, experiments on the involvement of cyclophilins revealed little, if any, role for these cellular enzymes in the modulation of furin cleavage. HPV16 L2 contains two consensus cleavage sites, Arg5 (2RHKR5) and Arg12 (9RTKR12). Mutant PSTCD-L2 viruses demonstrated that although furin can cleave either site, cleavage must occur at Arg12, as cleavage at Arg5 alone is insufficient for successful infection. Mutation of the conserved cysteine residues revealed that the Cys22-Cys28 disulfide bridge is not required for cleavage. The PSTCD-L2 virus or similar N-terminal fusions will be valuable tools to study additional cellular and viral determinants of furin cleavage.

IMPORTANCE

Furin cleavage of minor capsid protein L2 during papillomavirus infection has been difficult to directly visualize and quantify, confounding efforts to study this important step of HPV infection. Fusion of a small protein domain to the N terminus greatly facilitates direct visualization of the cleavage product, revealing important characteristics of this critical process. Contrary to the current model, we found that cleavage is largely independent of cyclophilins, suggesting that cyclophilins act either in parallel to or downstream of furin to trigger exposure of a conserved N-terminal L2 epitope (RG-1) during infection. Based on this finding, we strongly caution against using L2 RG-1 epitope exposure as a convenient but indirect proxy of furin cleavage.

Griffithsin and Carrageenan Combination To Target Herpes Simplex Virus 2 and Human Papillomavirus

Extensive preclinical evaluation of griffithsin (GRFT) has identified this lectin to be a promising broad-spectrum microbicide. We set out to explore the antiviral properties of a GRFT and carrageenan (CG) combination product against herpes simplex virus 2 (HSV-2) and human papillomavirus (HPV) as well as determine the mechanism of action (MOA) of GRFT against both viruses. We performed the experiments in different cell lines, using time-of-addition and temperature dependence experiments to differentiate inhibition of viral attachment from entry and viral receptor internalization. Surface plasmon resonance (SPR) was used to assess GRFT binding to viral glycoproteins, and immunoprecipitation and immunohistochemistry were used to identify the specific glycoprotein involved. We determined the antiviral activity of GRFT against HSV-2 to be a 50% effective concentration (EC₅₀) of 230 nM and provide the first evidence that GRFT has moderate anti-HPV activity (EC₅₀ = 0.429 to 1.39 μM). GRFT blocks the entry of HSV-2 and HPV into target cells but not the adsorption of HSV-2 and HPV onto target cells. The results of the SPR, immunoprecipitation, and immunohistochemistry analyses of HSV-2 combined suggest that GRFT may block viral entry by binding to HSV-2 glycoprotein D. Cell-based assays suggest anti-HPV activity through α₆ integrin internalization. The GRFT-CG combination product but not GRFT or CG alone reduced HSV-2 vaginal infection in mice when given an hour before challenge (P = 0.0352). While GRFT significantly protected mice against vaginal HPV infection when dosed during and after HPV16 pseudovirus challenge (P < 0.026), greater CG-mediated protection was afforded by the GRFT-CG combination for up to 8 h (P < 0.0022). These findings support the development of the GRFT-CG combination as a broad-spectrum microbicide.

Beyond RGD: virus interactions with integrins

Viruses successfully infect host cells by initially binding to the surfaces of the cells, followed by an intricate entry process. As multifunctional heterodimeric cell-surface receptor molecules, integrins have been shown to usefully serve as entry receptors for a plethora of viruses. However, the exact role(s) of integrins in viral pathogen internalization has yet to be elaborately described. Notably, several viruses harbor integrin-recognition motifs displayed on viral envelope/capsid-associated proteins. The most common of these motifs is the minimal peptide sequence for binding integrins, RGD (Arg-Gly-Asp), which is known for its role in virus infection via its ability to interact with over half of the more than 20 known integrins. Not all virus-integrin interactions are RGD-dependent, however. Non-RGD-binding integrins have also been shown to effectively promote virus entry and infection as well. Such virus-integrin binding is shown to facilitate adhesion, cytoskeleton rearrangement, integrin activation, and increased intracellular signaling. Also, we have attempted to discuss the role of carbohydrate moieties in virus interactions with receptor-like host cell surface integrins that drive the process of internalization. As much as possible, this article examines the published literature regarding the role of integrins in terms of virus infection and virus-encoded glycosylated proteins that mediate interactions with integrins, and it explores the idea of targeting these receptors as a therapeutic treatment option.

Papillomavirus Infectious Pathways: A Comparison of Systems

The HPV viral lifecycle is tightly linked to the host cell differentiation, causing difficulty in growing virions in culture. A system that bypasses the need for differentiating epithelium has allowed for generation of recombinant particles, such as virus-like particles (VLPs), pseudovirions (PsV), and quasivirions (QV). Much of the research looking at the HPV life cycle, infectivity, and structure has been generated utilizing recombinant particles. While recombinant particles have proven to be invaluable, allowing for a rapid progression of the HPV field, there are some significant differences between recombinant particles and native virions and very few comparative studies using native virions to confirm results are done. This review serves to address the conflicting data in the HPV field regarding native virions and recombinant particles.

A Dual Role for the Nonreceptor Tyrosine Kinase Pyk2 during the Intracellular Trafficking of Human Papillomavirus 16

The infectious process of human papillomaviruses (HPVs) has been studied considerably, and many cellular components required for viral entry and trafficking continue to be revealed. In this study, we investigated the role of the nonreceptor tyrosine kinase Pyk2 during HPV16 pseudovirion infection of human keratinocytes. We found that Pyk2 is necessary for infection and appears to be involved in the intracellular trafficking of the virus. Small interfering RNA-mediated reduction of Pyk2 resulted in a significant decrease in infection but did not prevent viral entry at the plasma membrane. Pyk2 depletion resulted in altered endolysosomal trafficking of HPV16 and accelerated unfolding of the viral capsid. Furthermore, we observed retention of the HPV16 pseudogenome in the trans-Golgi network (TGN) in Pyk2-depleted cells, suggesting that the kinase could be required for the viral DNA to exit the TGN. While Pyk2 has previously been shown to function during the entry of enveloped viruses at the plasma membrane, the kinase has not yet been implicated in the intracellular trafficking of a nonenveloped virus such as HPV. Additionally, these data enrich the current literature on Pyk2's function in human keratinocytes.

IMPORTANCE

In this study, we investigated the role of the nonreceptor tyrosine kinase Pyk2 during human papillomavirus (HPV) infection of human skin cells. Infections with high-risk types of HPV such as HPV16 are the leading cause of cervical cancer and a major cause of genital and oropharyngeal cancer. As a nonenveloped virus, HPV enters cells by interacting with cellular receptors and established cellular trafficking routes to ensure that the viral DNA reaches the nucleus for productive infection. This study identified Pyk2 as a cellular component required for the intracellular trafficking of HPV16 during infection. Understanding the infectious pathways of HPVs is critical for developing additional preventive therapies. Furthermore, this study advances our knowledge of intracellular trafficking processes in keratinocytes.

Remodeling of extracellular matrix by normal and tumor-associated fibroblasts promotes cervical cancer progression

Background

Comparison of tissue microarray results of 29 cervical cancer and 27 normal cervix tissue samples using immunohistochemistry revealed considerable reorganization of the fibrillar stroma of these tumors.

Preliminary densitometry analysis of laminin-1, α-smooth muscle actin (SMA) and fibronectin immunostaining demonstrated 3.8-fold upregulation of laminin-1 and 5.2-fold increase of SMA in the interstitial stroma, indicating that these proteins and the activated fibroblasts play important role in the pathogenesis of cervical cancer. In the present work we investigated the role of normal and tumor-associated fibroblasts.

Methods

In vitro models were used to throw light on the multifactorial process of tumor-stroma interaction, by means of studying the cooperation between tumor cells and fibroblasts. Fibroblasts from normal cervix and cervical cancers were grown either separately or in co-culture with CSCC7 cervical cancer cell line. Changes manifest in secreted glycoproteins, integrins and matrix metallo-proteases (MMPs) were explored.

Results

While normal fibroblasts produced components of interstitial matrix and TGF-β1 that promoted cell proliferation, cancer-associated fibroblasts (CAFs) synthesized ample amounts of laminin-1. The following results support the significance of laminin-1 in the invasion of CSCC7 cells: 1.) Tumor-associated fibroblasts produced more laminin-1 and less components of fibrillar ECM than normal cells; 2.) The production of laminin chains was further increased when CSCC7 cells were grown in co-culture with fibroblasts; 3.) CSCC7 cells were capable of increasing their laminin production; 4.) Tumor cells predominantly expressed integrin α6β4 laminin receptors and migrated towards laminin. The integrin profile of both normal and tumor-associated fibroblasts was similar, expressing receptors for fibronectin, vitronectin and osteopontin. MMP-7 secreted by CSCC7 cells was upregulated by the presence of normal fibroblasts, whereas MMP-2 produced mainly by fibroblasts was activated in the presence of CSCC7 cells.

Conclusions

Our results indicate that in addition to degradation of the basement membrane, invasion of cervical cancer is accomplished by the remodeling of the interstitial stroma, which process includes decrease and partial replacement of fibronectin and collagens by a laminin-rich matrix.

Human papillomavirus induced transformation in cervical and head and neck cancers

Human papillomavirus (HPV) is one of the most widely publicized and researched pathogenic DNA viruses. For decades, HPV research has focused on transforming viral activities in cervical cancer. During the past 15 years, however, HPV has also emerged as a major etiological agent in cancers of the head and neck, in particular squamous cell carcinoma. Even with significant strides achieved towards the screening and treatment of cervical cancer, and preventive vaccines, cervical cancer remains the leading cause of cancer-associated deaths for women in developing countries. Furthermore, routine screens are not available for those at risk of head and neck cancer. The current expectation is that HPV vaccination will prevent not only cervical, but also head and neck cancers. In order to determine if previous cervical cancer models for HPV infection and transformation are directly applicable to head and neck cancer, clinical and molecular disease aspects must be carefully compared. In this review, we briefly discuss the cervical and head and neck cancer literature to highlight clinical and genomic commonalities. Differences in prognosis, staging and treatment, as well as comparisons of mutational profiles, viral integration patterns, and alterations in gene expression will be addressed.