Bos taurus papillomavirus activity in peripheral blood mononuclear cells: demonstrating a productive infection

Abstract

ABSTRACT. Bovine papillomavirus (BPV) is an oncogenic virus with mucous and epithelial tropism. Possible productive virus infection in other tissues, such as blood, has been hypothesized. In order to investigate this possibility, three samples of skin papillomas and blood were collected from bovines with BPV infection and five samples of peripheral blood and one sample of normal tissue were collected from a calf without BPV infection. Peripheral blood mononuclear cells (PBMCs) were isolated from whole blood and examined by reverse transcription-polymerase chain reaction, immunofluorescence, in situ hybridization, and electron microscopy. The tissue samples were examined for histopathological and (2015) immunohistochemical features. The skin papillomas showed the presence of DNA sequences of BPV-2, BPV-11, and a putative virus type. The blood samples showed DNA sequences of BPV-1, 2, and 4 simultaneously. Immunohistochemistry showed BPV L1 protein in both epithelium and stroma and BPV E2 protein in koilocytes. In situ hybridization confirmed the presence of BPV DNA in PBMCs and immunofluorescence showed nuclear labeling of E2 and L1 BPV proteins in PBMCs. The transcription analysis revealed transcripts of BPV-1 L1, BPV-2 L2, and BPV-4 E7 in blood and papilloma samples of BPV-infected cattle. The comet assay revealed high levels of host cell DNA damage upon BPV infection. Electron microscopy analysis of PBMCs identified the presence of particles in the cytoplasm that are consistent with papillomavirus in size and shape. The productive infection of PBMCs with BPV has been previously discussed and this study provides evidence indicating that PBMCs are a target of BPV.

Bovine papillomavirus productive infection in cell cultures: First evidences

“…Due to this paradigm, little attention has been given to the primary cultures derived from BPV-infected tissues as model to study the pathogenic mechanism of PVs. However, in last decades, studies have described the presence of BPV DNA sequences, transcripts, proteins and virus-like particles in sites before not recognized as permissive to productive infection due to the absence of cell differentiation, including peripheral blood [51,52] and placenta [53]. Similar results have been also described in humans, in which sequences of HPV were verified in blood and semen [54,55].…”

“…Considering that the L1 protein expression is verified in sites of viral assembly, once this protein is able to self-organize in pentameric structures that composes the BPV capsid [66], L1 immunodetection is pointed out as the main evidence of productive infection [51,67]. Based on BPV DNA sequences identification and L1 immunodetection, Roperto et al [52] and Melo et al [51] described the productive infection in lymphocytes and, later in placenta [53].…”

“…Based on these data, the different cell lines, in the sixth passage (P6), were subjected to EM analysis. Under EM, BPV virions are visualized as non-enveloped isometric particles, with electron-dense spherical morphology and a diameter of 45-60 nm [51,59,69].…”

Genetics and metabolic deregulation following cancer initiation: A world to explore

“…Both viruses have common genetic, morphological and pathogenic characteristics [127], can be disseminated by hematology pathway [28,[128][129][130][131], turning then a public health problem [132]. Moreover, BPV is considered a study prototype of oncogenic process [133].…”

“…For this reason, mutagen identification has been explored [13][14][15][16], since to avoid the long term exposure to these mutagens can be considered a protective method against cancer. Currently, it is known that several drugs [16][17][18], organic [19][20][21][22] and inorganic chemical compounds [23,24] and biological agents, including viruses [12,[25][26][27][28][29][30][31][32][33] are able to induce DNA damage.…”