[Show abstract][Hide abstract] ABSTRACT: Papillomaviruses are a family of slowly evolving DNA viruses and their evolution is commonly linked to that of their host species. However, while Bovine Papillomavirus-1 (BPV-1) primarily causes warts in its natural host the cow, it can also cause locally aggressive and invasive skin tumours in equids known as sarcoids, and thus provides a rare contemporary example of cross-species transmission of a papillomavirus. Here we describe the first phylogenetic analysis of BPV-1 in equine sarcoids, to our knowledge, allowing us to explore the evolutionary history of BPV-1 and investigate its cross-species association with equids. A phylogenetic analysis of the BPV-1 transcriptional promoter region (the long control region or LCR) was conducted on 15 bovine and 116 equine samples from four continents. Incorporating previous estimates for evolutionary rates in papillomavirus implies that the genetic diversity in the LCR variants is ancient and predates domestication of both equids and cattle. The phylogeny demonstrates geographic segregation into an ancestral group (African, South American and Australian samples), and a more recently derived, largely European clade. While our data are consistent with BPV-1 originating in cattle, we find evidence of multiple, likely relatively recent, cross-species transmission events into horses. We also demonstrate the high prevalence of one particular sequence variant (variant 20), and suggest this may indicate this variant shows a fitness advantage in equids. Our results add to the accumulating evidence that host specificity in papillomaviruses is more flexible than previously assumed.
Full-text · Article · Sep 2014 · Journal of General Virology
[Show abstract][Hide abstract] ABSTRACT: The cutaneous beta human papillomavirus (beta HPV) types appear to be involved in skin carcinogenesis. However, only a few
beta HPVs have been investigated so far. Here, we compared the properties of E6 and E7 oncoproteins from six uncharacterized
beta HPVs (14, 22, 23, 24, 36, 49). Only HPV49 E6 and E7 immortalized primary human keratinocytes and efficiently deregulated
the p53 and pRb pathways. Furthermore, HPV49 E6, similarly to E6 from the oncogenic HPV16, promoted p53 degradation.
Full-text · Article · Dec 2011 · Journal of Virology
[Show abstract][Hide abstract] ABSTRACT: Papillomaviruses (PVs) are established agents of human and animal cancers. They infect cutaneous and mucous epithelia. High Risk (HR) Human PVs (HPVs) are consistently associated with cancer of the uterine cervix, but are also involved in the etiopathogenesis of other cancer types. The early oncoproteins of PVs: E5, E6 and E7 are known to contribute to tumour progression. While the oncogenic activities of E6 and E7 are well characterised, the role of E5 is still rather nebulous. The widespread causal association of PVs with cancer makes their study worthwhile not only in humans but also in animal model systems. The Bovine PV (BPV) system has been the most useful animal model in understanding the oncogenic potential of PVs due to the pivotal role of its E5 oncoprotein in cell transformation. This review will highlight the differences between HPV-16 E5 (16E5) and E5 from other PVs, primarily from BPV. It will discuss the targeting of E5 as a possible therapeutic agent.
[Show abstract][Hide abstract] ABSTRACT: It is unclear what level of neutralizing antibody is sufficient to protect cattle from experimental bovine papillomavirus type 4 (BPV4) challenge. Markedly lower, and often undetected, serum neutralizing antibody titers were associated with protection in cattle vaccinated with BPV4 L2 as compared to L1 VLP. We hypothesized that vaccination with concatemers of the N-terminal protective epitopes of L2 derived from multiple animal papillomavirus types would enhance the breadth and strength of immunity. Therefore we generated a multimeric L2 antigen derived from three bovine and three canine papillomavirus types with divergent phenotypes and purified it from bacteria. Mice vaccinated three times with this six type L2 vaccine formulated in alum or RIBI adjuvant generated robust serum neutralizing antibody titers against BPV1, BPV4 and canine oral papillomavirus (COPV). Furthermore, vaccination with this six type L2 vaccine formulated in adjuvant, like BPV1 L1 VLP, protected the mice from experimental challenge with BPV1 pseudovirus.
[Show abstract][Hide abstract] ABSTRACT: Equine sarcoids represent the most common skin tumours in equids worldwide, characterized by extensive invasion and infiltration of lymphatics, rare regression and high recurrence after surgical intervention. Bovine papillomavirus type 1 (BPV-1) activity is necessary for the transformation phenotype of equine fibroblasts. Among the many changes induced by BPV-1, matrix metalloproteinase 1 (MMP-1) upregulation contributes to the invasiveness of equine fibroblasts. However, it is not yet known how BPV-1 proteins regulate equine MMP-1 expression. To elucidate this mechanism, the equine MMP-1 promoter was cloned and analysed. A putative activator protein-1 (AP-1)-binding site was demonstrated to be crucial for upregulated MMP-1 promoter activity by BPV-1. BPV-1 E6 and E7 proteins increased MMP-1 promoter activity, and inhibition of BPV-1 gene expression by small interfering RNA significantly reduced the promoter activity. c-Jun and Fra-1, two components of the AP-1 transcription factor complex, were overexpressed and activated by BPV-1 in equine fibroblasts. Finally, BPV-1 E5, E6 and E7 proteins increased MMP-1 mRNA and protein expression. In conclusion, the expression of MMP-1 can be enhanced by BPV-1 oncoproteins E6 and E7 through the AP-1 transcription factor and by E5 via an indirect mechanism. These findings shed light on the mechanism of BPV-1-mediated equine fibroblast infiltration and indicate that both BPV-1 oncoproteins and AP-1 could be potential targets for equine sarcoid therapy.
Preview · Article · Jul 2011 · Journal of General Virology
[Show abstract][Hide abstract] ABSTRACT: Equine sarcoids represent the most common skin tumours in equids worldwide, characterized by extensive invasion and infiltration of lymphatics, rare regression and high recurrence after surgical intervention. Bovine papillomavirus type-1 (BPV-1) and less commonly BPV-2 are the causative agents of the diseases. It has been demonstrated that BPV-1 viral gene expression is necessary for maintaining the transformation phenotype. However, the underlying mechanism for BPV-1 transformation remains largely unknown, and the cellular factors involved in transformation are not fully understood. Previously mitogen-activated protein kinase (MAPK) signalling pathway has been shown to be important for cellular transformation. This study investigated the role of p38 MAPK (p38) in the transformation of equine fibroblasts by BPV-1. Elevated expression of phosphorylated p38 was observed in BPV-1 expressing fibroblasts due to the expression of BPV-1 E5 and E6. The phosphorylation of the MK2 kinase, a substrate of p38, was also enhanced. Inhibition of p38 activity by its selective inhibitor SB203580 changed cell morphology, reduced the proliferation of sarcoid fibroblasts and inhibited cellular invasiveness, indicating the indispensable role of p38 in BPV-1 transformation of equine fibroblasts. These findings provide new insights into the pathogenesis of equine sarcoids and suggest that p38 could be a potential target for equine sarcoid therapy.
Preview · Article · Apr 2011 · Journal of General Virology
[Show abstract][Hide abstract] ABSTRACT: Equine sarcoids represent the most common skin tumours in equids worldwide, characterised by extensive invasion and infiltration of lymphatics, rare regression and high recurrence after surgical intervention. Bovine papillomavirus type-1 (BPV-1) activity is necessary for the transformation phenotype of equine fibroblasts. Among the many changes induced by BPV-1, MMP-1 upregulation contributes to the invasiveness of equine fibroblasts. However it is yet unknown how BPV-1 proteins regulate equine MMP-1 expression. To elucidate the mechanism, equine MMP-1 promoter was cloned and analysed. A putative AP-1 BS was demonstrated to be crucial for upregulated MMP-1 promoter activity by BPV-1. BPV-1 E6 and E7 increased MMP-1 promoter activity, and inhibition of BPV-1 genes expression by siRNA significantly reduced the promoter activity. c-Jun and Fra-1, two components of the AP-1 transcription factor complexes are overexpressed and activated by BPV-1 in equine fibroblasts. Finally BPV-1 E5, E6 and E7 increased MMP-1 mRNA and protein expression. In conclusion the expression of MMP-1 can be enhanced by BPV-1 oncoproteins E6 and E7 through AP-1 transcription factor, and by E5 via an indirect mechanism. These findings shed light on the mechanism of BPV-1 mediated equine fibroblast infiltration and indicate that both BPV-1 oncoproteins and AP-1 can be potential targets for equine sarcoid therapy.
[Show abstract][Hide abstract] ABSTRACT: Equine sarcoids represent the most common skin tumours in equids worldwide, characterized by localized invasion, rare regression and high recurrence following surgical intervention. Bovine papillomavirus type 1 (BPV-1) and less commonly BPV-2 are now widely recognized as the causative agents of the disease. Fibroblasts isolated from sarcoids are highly invasive. Invasion is associated with a high level of viral gene expression and matrix metalloproteinase upregulation. However, it remains unclear to what extent BPV-1 proteins are involved in the transformation of equine cells. To address this question, the individual viral genes E5, E6 and E7 were overexpressed in normal equine fibroblasts (EqPalF cells) and in the immortal but not fully transformed sarcoid-derived EqS02a cell line. The proliferation and invasiveness of these cell lines were assessed. E5 and E6 were found to be responsible for the enhanced cell proliferation and induction of increased invasion in EqS02a cells, whilst E7 appeared to enhance cell anchorage independence. Knockdown of BPV-1 oncogene expression by small interfering RNA reversed the transformed phenotype of sarcoid fibroblasts. Together, these observations strongly suggest that BPV-1 proteins play indispensable roles in the transformation of equine fibroblasts. These data also suggest that BPV-1 proteins are potential drug targets for equine sarcoid therapy.
Preview · Article · Dec 2010 · Journal of General Virology
[Show abstract][Hide abstract] ABSTRACT: HPV-16 is the major causes of cervical cancer. Persistence of infection is a necessary event for progression of the infection to cancer. Among other factors, virus persistence is due the viral proteins fighting the immune response. HPV-16 E5 down-regulates MHC/HLA class I, which is much reduced on the cell surface and accumulates in the Golgi apparatus in cells expressing E5. This effect is observed also in W12 cells, which mimic early cervical intraepithelial progression to cervical cancer. The functional effect of MHC I down-regulation on human CD8 T cells is not known, because of the need for HLA-matched, HPV-specific T cells that recognise E5 expressing-cells. Here we employ a heterologous cell/MHC I system which uses mouse cells expressing both E5 and HLA-A2, and A2-restricted CTLs; we show that the E5-induced reduction of HLA-A2 has a functional impact by reducing recognition of E5 expressing cells by HPV specific CD8+ T cells.
[Show abstract][Hide abstract] ABSTRACT: The 1st International Workshop on Papillomavirus E5 Oncogene was held in Capri, Italy, 27-28 May 2010. Here we present a brief report of the various lectures which addressed the multiple facets of the E5 protein.
[Show abstract][Hide abstract] ABSTRACT: BPV-1 and less commonly BPV-2 are associated with the pathogenesis of equine skin tumours termed sarcoids. We recently documented the transcriptional changes that are induced by BPV-1 in equine fibroblasts using microarray analyses. TLR4 expression was found to be significantly down-regulated by BPV-1. In the present study, we show that TLR4 expression is significantly decreased following the exogenous expression of BPV-1 E2 and E7 in primary equine fibroblasts. The results were confirmed by the demonstration of increased TLR4 expression following siRNA suppression of BPV-1 E2 and E7 viral gene expression. These data imply that BPV-1 is able to subvert the innate immune response by downregulation of TLR4.
[Show abstract][Hide abstract] ABSTRACT: The E5 oncoprotein of human papillomavirus type 16 downregulates surface MHC Class I and interacts with the heavy chain of the MHC complex via the first hydrophobic domain, believed to form the first helical transmembrane region (TM1) of E5. TM1 contains 4 equally spaced di-leucine (LL1-LL4) motifs. Di-leucine motifs have been implicated in protein-protein interactions and as localization signals. To see if any of the 4 di-leucine motifs of TM1 are involved in MHC downregulation by E5, we mutated each LL pair into valine pairs (VV1-VV4), as mutation of leucine to valine is not expected to cause major structural alterations in E5. We found that all 4 mutations disrupted the intracellular location of E5 and abrogated its MHC I downregulating activity; however VV2 and VV4 mutants were still able to interact physically with the MHC I heavy chain (HC) in vitro, while VV1 and VV3 mutants had lost this activity. We conclude that LL1 and LL3 are necessary for the interaction with HC, but LL2 and LL4 are not. However all 4 LL motifs are responsible for the proper localization of E5 in the Golgi/ER, and the displacement of E5 from this location contributes to the abrogation of MHC I downregulation. LL1 and LL3 motifs are expected to be on one face of the TM1 helix and LL2 and LL4 on the opposite face. We propose that E5 interacts with HC via LL1 and LL3 and that all 4 di-leucine motifs act as a targeting signal.
Preview · Article · Apr 2010 · International Journal of Cancer
[Show abstract][Hide abstract] ABSTRACT: Papillomaviruses are DNA viruses that cause tumours of the skin in humans and animals. The natural host of bovine papillomavirus is cattle, but also equids, resulting in tumours termed sarcoids. Matrix metalloproteinase 1 (MMP-1) expression is up-regulated in sarcoid fibroblasts and tumours. We extended our observation to other MMPs and determined whether MMPs induced invasion of sarcoid fibroblasts. Collagenase (MMP-1) and Gelatinase (MMP-2, MMP-9) were over-expressed in sarcoid fibroblasts and tumours. The fibroblasts were invasive in a 3D/matrigel invasion assay system. Inhibition of MMP by GM6001 significantly reduced invasion. E2 siRNA treatment of sarcoid fibroblasts decreased the expression of the viral genes and of MMP-2 and -9, leading to a dramatic reduction of invasion. This demonstrates that BPV-1 induces over-expression of MMPs contributing to invasiveness of sarcoid fibroblasts. Inhibition of E2 by siRNA leads to abrogation of invasion suggesting that E2 is a good target for sarcoid treatment.
[Show abstract][Hide abstract] ABSTRACT: Vaccines against the human papillomaviruses (HPVs) most frequently associated with cancer of the cervix are now available. These prophylactic vaccines, based on virus-like particles (VLPs), are extremely effective, providing protection from infection in almost 100% of cases. However, the vaccines present some limitations: they are effective primarily against the HPV type present in the vaccine, are expensive to produce, and need a cold chain. Vaccines based on the minor capsid protein L2 have been very successful in animal models and have been shown to provide a good level of protection against different papillomavirus types. The potential of L2-based vaccines to protect against many types of HPVs is discussed.
Full-text · Article · Nov 2009 · Journal of Virology
[Show abstract][Hide abstract] ABSTRACT: Human papillomavirus type 16 (HPV-16) is the cause of cervical cancer. The HPV genome encodes three transforming proteins, E5, E6 and E7, E6 and E7 are the main transforming proteins of HPV, while the role of E5 is still poorly understood. Using three dimensional organotypic raft cultures we show that HaCaT human keratinocytes expressing HPV-16 E5 form a very perturbed epithelium, with simultaneous hyperkeratinization of some cells and defective differentiation of other cells. The basal layer is disturbed and many cells invade the collagen matrix. Many cells among the differentiated layers show characteristics of basal cells: progression through the cell cycle, expression of cytokeratin 14, lack of cytokeratin 1 and production of matrix metalloproteases (MMP). Using deletion mutants which encompass the three hydrophobic domains of E5, we have assigned the ability to promote invasion of the matrix to the first hydrophobic domain, and the capacity to induce MMP9 to the C-terminal four amino acids. We also show that invasion and production of MMP9 can be dissociated, as mutants that are still capable of invasion do not produce MMP9 and vice versa
Preview · Article · Oct 2009 · Journal of General Virology
[Show abstract][Hide abstract] ABSTRACT: Bovine papillomavirus type 1 is one of the aetiological agents of equine sarcoids. The viral major oncoprotein E5 is expressed in virtually all sarcoids, sarcoid cell lines and in vitro-transformed equine fibroblasts. To ascertain whether E5 behaves in equine cells as it does in bovine cells, we introduced the E5 open reading frame into fetal equine fibroblasts (EqPalF). As observed in primary bovine fibroblasts (BoPalF), E5 by itself could not immortalize EqPalF and an immortalizing gene, such as human telomerase (hTERT/hT), was required for the cells to survive selection. The EqPalF-hT-1E5 cells were morphologically transformed, elongated with many pseudopodia and capable of forming foci. Equine major histocompatibility complex class I (MHC I) was inhibited in these cells at least at two levels: transcription of MHC I heavy chain was inhibited and the MHC I complex was retained in the Golgi apparatus and prevented from reaching the cell surface. We conclude that, as in bovine cells and tumours, E5 is a player in the transformation of equine cells and the induction of sarcoids, and a potential major cause of MHC I downregulation and hence poor immune clearance of tumour cells.
Preview · Article · Sep 2009 · Journal of General Virology
[Show abstract][Hide abstract] ABSTRACT: BPVs are double stranded DNA viruses that can infect several species other than the natural host, cattle, including equids. In equids, BPV-1, and, less commonly BPV-2, infection gives rise to fibroblastic tumours of the skin. Whilst a causal relationship between BPV-1/2 and equine sarcoids is now well established, how the disease is transmitted is not known. In this study we show BPV-1 DNA can be detected in flies trapped in the proximity of sarcoid-affected animals. Sequence analysis of the BPV-1 LCR from flies indicates that flies harbour BPV-1 LCR sequence variants II and IV which are commonly detected in equine sarcoids. These data suggest that flies may be able to transmit BPV-1 between equids.
[Show abstract][Hide abstract] ABSTRACT: Equine sarcoids are skin tumours of horses caused by infection with BPV-1 or 2. Maintenance and replication of the viral genome depend upon the viral proteins E1 and E2. We examined the effects of an E2 specific siRNA on E2 and E1 viral gene expression, viral load and cell growth in BPV-1 transformed sarcoid-derived cells. Transfection with E2-siRNA caused a reduction in E2 and E1 mRNA expression as well as viral load, growth inhibition and decreased anchorage-independent growth. siRNA treated cells showed significantly higher apoptosis rates than control cells. Thus sequence specific targeting of E2 provides a powerful strategy to eliminate BPV-1 genomes and induce cell death in BPV-1 transformed cells.
[Show abstract][Hide abstract] ABSTRACT: Papillomas and fibropapillomas may occur in the skin and in different organs in animals. Ten different genotypes of bovine papillomavirus (BPV) have been identified. BPV-1 through BPV-10 are all strictly species-specific, but BPV-1/2 may also infect other species such as equids, inducing fibroblastic tumors. BPV-1 and BPV-2 are associated with fibropapillomas in cattle; these tumors are formed by excessive proliferation of virus-infected dermal fibroblasts and epidermal keratinocytes. Nine water buffalo (Bubalus bubalis) were examined for the presence of multiple cutaneous and perivulvar tumors. Cutaneous and perivulvar fibropapillomatosis were confirmed histologically. Negative-stain transmission electron microscopic examination revealed papillomavirus-like particles in the fibropapillomas, and papillomaviral DNA was also detected by the polymerase chain reaction. The amplified long control region (LCR) DNA sequence was identical to that of BPV-1. The BPV-1 E5 oncoprotein was strongly expressed in the tumor cells thus confirming a causal role of the virus. This article represents the first report of cutaneous, perivulvar, and vulvar fibropapilloma associated with BPV-1 infection in the water buffalo and describes another example of cross-species infection by BPV-1.
No preview · Article · Apr 2009 · Veterinary Pathology