Human papillomavirus type 16 late gene expression is regulated by cellular RNA processing factors in response to epithelial differentiation

Functional analysis of HPV-like particle-activated Langerhans cells in vitro

Langerhans cells (LCs) are antigen-presenting cells responsible for initiating an immune response against human papillomaviruses (HPVs) entering the epithelial layer in vivo as they are the first immune cell that HPV comes into contact with. LCs become activated in response to foreign antigens, which causes internal signaling resulting in the increased expression of co-stimulatory molecules and the secretion of inflammatory cytokines. Functionally activated LCs are then capable of migrating to the lymph nodes where they interact with antigen-specific T cells and initiate an adaptive T-cell response in vivo. However, HPV has evolved in a manner that suppresses LC function, and thus the induction of antigen-specific T cells is hindered. While many methods exist to monitor the activity of LCs in vitro, the migration and induction of cytotoxic T cells is ultimately indicative of a functional immune response. Here, methods in analyzing functional migration and induction of antigen-specific T cells after stimulation of LCs with HPV virus-like particles in vitro are described.

Molecular analysis of human papillomavirus virus-like particle activated Langerhans cells in vitro

Langerhans cells (LC) are the resident antigen-presenting cells in human epithelium, and are therefore responsible for initiating immune responses against human papillomaviruses (HPV) entering the epithelial and mucosal layers in vivo. Upon proper pathogenic stimulation, LC become activated causing an internal signaling cascade that results in the up-regulation of co-stimulatory molecules and the release of inflammatory cytokines. Activated LC then migrate to lymph nodes where they interact with antigen-specific T cells and initiate an adaptive T-cell response. However, HPV manipulates LC in a suppressive manner that alters these normal maturation responses. Here, in vitro LC activation assays for the detection of phosphorylated signaling intermediates, the up-regulation of activation-associated surface markers, and the release of inflammatory cytokines in response to HPV particles are described.

Metagenomic assay for identification of microbial pathogens in tumor tissues

Screening for thousands of viruses and other pathogenic microorganisms, including bacteria, fungi, and parasites, in human tumor tissues will provide a better understanding of the contributory role of the microbiome in the predisposition for, causes of, and therapeutic responses to the associated cancer. Metagenomic assays designed to perform these tasks will have to include rapid and economical processing of large numbers of samples, supported by straightforward data analysis pipeline and flexible sample preparation options for multiple input tissue types from individual patients, mammals, or environmental samples. To meet these requirements, the PathoChip platform was developed by targeting viral, prokaryotic, and eukaryotic genomes with multiple DNA probes in a microarray format that can be combined with a variety of upstream sample preparation protocols and downstream data analysis. PathoChip screening of DNA plus RNA from formalin-fixed, paraffin-embedded tumor tissues demonstrated the utility of this platform, and the detection of oncogenic viruses was validated using independent PCR and deep sequencing methods. These studies demonstrate the use of the PathoChip technology combined with PCR and deep sequencing as a valuable strategy for detecting the presence of pathogens in human cancers and other diseases.

IMPORTANCE

This work describes the design and testing of a PathoChip array containing probes with the ability to detect all known publicly available virus sequences as well as hundreds of pathogenic bacteria, fungi, parasites, and helminths. PathoChip provides wide coverage of microbial pathogens in an economical format. PathoChip screening of DNA plus RNA from formalin-fixed, paraffin-embedded tumor tissues demonstrated the utility of this platform, and the detection of oncogenic viruses was validated using independent PCR and sequencing methods. These studies demonstrate that the PathoChip technology is a valuable strategy for detecting the presence of pathogens in human cancers and other diseases.

Inhibition of Langerhans cell maturation by human papillomavirus type 16: a novel role for the annexin A2 heterotetramer in immune suppression

High-risk human papillomaviruses (HPVs) are sexually transmitted viruses causally associated with several cancers. During its natural life cycle, HPV16, the most common high-risk genotype, infects the epithelial basal cells in a process facilitated through a recently identified receptor, the annexin A2 heterotetramer (A2t). During infection, HPV16 also interacts with Langerhans cells (LC), the APC of the epithelium, inducing immune suppression, which is mediated by the HPV16 L2 minor capsid protein. Despite the importance of these virus-immune cell interactions, the specific mechanisms of HPV16 entry into LC and HPV16-induced immune suppression remain undefined. An N-terminal peptide of HPV16 L2 (aa 108-126) has been shown to specifically interact with A2t. In this study, we show that incubation of human LC with this peptide blocks binding of HPV16. Inhibiting this interaction with an A2t ligand or by small interfering RNA downregulation of A2t significantly decreases HPV16 internalization into LC in an L2-dependent manner. A2t is associated with suppression of LC maturation as demonstrated through attenuated secretion of Th1-associated cytokines and decreased surface expression of MHC class II on LC exposed to A2t. Conversely, small molecule inhibition of A2t prevents HPV16-induced suppression of LC immune function as indicated by significantly increased secretion of inflammatory cytokines and surface expression of CD86 in HPV16 treated LC pre-exposed to A2t inhibitors. These results demonstrate that HPV16 suppresses LC maturation through an interaction with A2t, revealing a novel role for this protein.

Differential expression of HPV16 L2 gene in cervical cancers harboring episomal HPV16 genomes: influence of synonymous and non-coding region variations

We tested the hypothesis that (i) synonymous variations within the coding regions, and (ii) variations within the non-coding regions of HPV, influence cervical cancer (CaCx) pathogenesis under the impact of intact HPV16 genomes. Whole genome sequence analysis of HPV16 isolates within 70 CaCx cases and 25 non-malignant samples revealed that synonymous variations were significantly higher within the E6 (p = 0.014), E5 (p = 0.001) and L2 (p = 0.0002) genes of HPV16 isolates within cases, compared to isolates within non-malignant samples. All of the 25 (100%) humanized codons identified within L2 ORF of the samples analyzed, were harbored by CaCx cases, while 8 out of 25 (32%) were harbored by HPV16 positive non-malignant samples (p = 3.87105E-07). L2 (mRNA and protein) expression was evident only among cases with episomal viral genomes and L2 mRNA expression correlated significantly with E2 gene copy numbers suggesting expression from all episomal genomes. Among such cases, Asian American (AA) isolates portrayed all of the humanized codons (100%; 4–6/sample) recorded within L2, which was significantly higher (p = 2.02E-7) compared to the European (E) isolates (22.8%; none or 1–2/sample). Additionally, majority of E variant isolates within cases (54/57; 94.7%) portrayed a variation (T4228C) within the short non-coding region (NCR2) between E5 and L2 genes, which portrays a weak promoter activity specific for L2 mRNA expression. This resulted in loss of 9 out of 14 miRNA binding sites (hsa-miR-548 family), despite the significant overexpression of miR548a-5p and miR548d-5p among such cases (28.64 and 36.25 folds, respectively), in comparison to HPV negative control samples. The findings exemplify the biological relevance of sequence variations in HPV16 genomes and highlight that episomal HPV16 in CaCx cases employ multiple mechanisms to sustain L2 expression, thereby justifying the potential role of L2 in such cancers, as opposed to those harboring viral integration.

The S100A10 subunit of the annexin A2 heterotetramer facilitates L2-mediated human papillomavirus infection

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.