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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.

Bovine papillomavirus type 2 (BPV-2) infection has been associated with urinary bladder tumours in adult cattle grazing on bracken fern-infested land. In this study, we investigated the simultaneous presence of BPV-2 in whole blood and urinary bladder tumours of adult cattle in an attempt to better understand the biological role of circulating BPV-2. Peripheral blood samples were collected from 78 cattle clinically suffering from a severe chronic enzootic haematuria. Circulating BPV-2 DNA was detected in 61 of them and in two blood samples from healthy cows. Fifty of the affected animals were slaughtered at public slaughterhouses and neoplastic proliferations in the urinary bladder were detected in all of them. BPV-2 DNA was amplified and sequenced in 78 % of urinary bladder tumour samples and in 38.9 % of normal samples as a control. Circulating episomal BPV-2 DNA was detected in 78.2 % of the blood samples. Simultaneous presence of BPV-2 DNA in neoplastic bladder and blood samples was detected in 37 animals. Specific viral E5 mRNA and E5 oncoprotein were also detected in blood by RT-PCR and Western blot/immunocytochemistry, respectively. It is likely that BPV-2 can persist and be maintained in an active status in the bloodstream, in particular in the lymphocytes, as a reservoir of viral infection that, in the presence of co-carcinogens, may cause the development of urinary bladder tumours. INTRODUCTIONBovine papillomaviruses (BPVs) are species-specific, double-stranded DNA viruses responsible for cutaneous and mucosal neoplastic lesions. They are small non-enveloped viruses with an icosahedral capsid. Their open reading frames (ORFs) are divided into early (E) and late (L) regions. The early region encodes non-structural proteins E1 to E7, of which, E5, E6 and E7 are known to be oncoproteins. The late region encodes structural proteins L1 and L2 forming the capsid. Bovine papillomavirus type 2 (BPV-2) is classified in the genus Deltapapillomavirus, species 4, the biological properties of which are characterized by the induction of fibropapillomas in cattle and sarcoids in equids (Brandt et al., 2008;Chambers et al., 2003;de Villiers et al., 2004). BPV-2 infection in the presence of environmental carcinogens, such as ptaquiloside (PT) of bracken fern (Pteridium aquilinum), has been associated with urinary bladder neoplastic lesions in adult cattle, in which chronic enzootic haematuria (CEH) is the most important clinical sign (Campo, 1997; Campo et al., 1992;Hopkins, 1986).The effect of the route of viral infection, and the synergistic relationship between BPV-2 and immunosuppressive and oncogenic compounds present in the bracken fern in the malignant progression of bladder lesions (Campo, 1997; Campo et al., 1992; Jarrett et al., 1978;Reddy & Fialkow, 1983;Stocco dos Santos et al., 1998) are not well-known, thus deserving further investigations.To date, the BPV-2 genome has been detected in lymphocytes during latent papillomavirus infection in cattle (Campo et al., 1994). In addition, the occurrence of horiz...

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A minor groove binder (MGB) probe assay was developed to discriminate between type 2-based vaccines and field strains of canine parvovirus (CPV). Considering that most of the CPV vaccines contain the old type 2, no longer circulating in canine population, two MGB probes specific for CPV-2 and the antigenic variants (types 2a, 2b and 2c), respectively, were labeled with different fluorophores. The MGB probe assay was able to discriminate correctly between the old type and the variants, with a detection limit of 10(1) DNA copies and a good reproducibility. Quantitation of the viral DNA loads was accurate, as demonstrated by comparing the CPV DNA titres to those calculated by means of the TaqMan assay recognising all CPV types. This assay will ensure resolution of most diagnostic problems in dogs showing CPV disease shortly after CPV vaccination, although it does not discriminate between field strains and type 2b-based vaccines, recently licensed to market in some countries.