title: PBMCs are additional sites of productive infection of bovine papillomavirus type 2.
abstract: Bovine papillomavirus type 2 (BPV-2) is an oncogenic virus infecting both epithelial and mesenchymal cells. Its life cycle, similar to other papillomaviruses (PVs), appears to be linked to epithelial differentiation. Human and bovine PVs have been known to reside in a latent, episomal form in PBMCs; therefore, it is believed that blood cells, like all mesenchymal cells, function as non-permissive carriers. Here, for the first time in veterinary and comparative medicine, the BPV-2 E5 oncoprotein and the major structural L1 capsid protein, known to be expressed only in productive infections, were shown to occur in defined subsets of PBMCs. E5 oncoprotein was detected in sorted T- and B-cells as well as in monocytes by flow cytometry and Western blot analysis. However, CD4(+) and CD8(+) lymphocytes appeared to be the main circulating targets of the virus, thus possibly representing the most important reservoir of active BPV-2 in blood. L1 protein was identified by flow cytometry in a population of blood cells recognized as lymphocytes by morphological scatter properties. Western blot analysis was performed on lysates obtained from the sorted subpopulations of PBMCs and detected L1 protein in CD4(+) and CD8(+) cells only. Thus, this study showed that CD4(+) and CD8(+) lymphocytes are permissive for BPV-2 and are new, hitherto unknown sites of productive PV infection. In light of these observations, the life cycle of PVs needs to be revisited to gain novel insights into the epidemiology of BPV infection and the pathogenesis of related diseases.
authors.affiliation: Dipartimento di Patologia e Sanità Animale, Sezione di Malattie Infettive, Facoltà di Medicina Veterinaria, Università di Napoli Federico II, Napoli, Italy.
authors.forename: Sante
authors.initials: S
authors.lastname: Roperto
authors.affiliation: Dipartimento di Patologia Animale, Igiene e Sanità Pubblica Veterinaria, Facoltà di Medicina Veterinaria, Università di Milano, Milano, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Comazzi
authors.affiliation: Fondazione IRCCS Istituto Neurologico 'Carlo Besta', Milano, Italy.
authors.forename: Emilio
authors.initials: E
authors.lastname: Ciusani
authors.affiliation: Laboratorio di Virologia, Regina Elena Cancer Institute, Rome, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Paolini
authors.affiliation: Dipartimento di Patologia e Sanità Animale, Sezione Patologia Generale, Facoltà di Medicina Veterinaria, Università di Napoli Federico II, Napoli, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Borzacchiello
authors.affiliation: Dipartimento di Patologia e Sanità Animale, Sezione Patologia Generale, Facoltà di Medicina Veterinaria, Università di Napoli Federico II, Napoli, Italy.
authors.forename: Iolanda
authors.initials: I
authors.lastname: Esposito
authors.affiliation: Dipartimento di Patologia e Sanità Animale, Sezione Patologia Generale, Facoltà di Medicina Veterinaria, Università di Napoli Federico II, Napoli, Italy.
authors.forename: Roberta
authors.initials: R
authors.lastname: Lucà
authors.affiliation: Dipartimento di Patologia e Sanità Animale, Sezione Patologia Generale, Facoltà di Medicina Veterinaria, Università di Napoli Federico II, Napoli, Italy.
authors.forename: Valeria
authors.initials: V
authors.lastname: Russo
authors.affiliation: Dipartimento di Patologia e Sanità Animale, Sezione Patologia Generale, Facoltà di Medicina Veterinaria, Università di Napoli Federico II, Napoli, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Urraro
authors.affiliation: Laboratorio di Virologia, Regina Elena Cancer Institute, Rome, Italy.
authors.forename: Aldo
authors.initials: A
authors.lastname: Venuti
authors.affiliation: Dipartimento di Patologia e Sanità Animale, Sezione Patologia Generale, Facoltà di Medicina Veterinaria, Università di Napoli Federico II, Napoli, Italy.
authors.forename: Franco
authors.initials: F
authors.lastname: Roperto
mesh_terms: D000818:Animals; D052688:Bovine papillomavirus 1 / Q000235:genetics / Q000502:physiology*; D036022:Capsid Proteins / Q000235:genetics / Q000378:metabolism; D002417:Cattle; D002418:Cattle Diseases / Q000276:immunology / Q000821:virology*; D005260:Female; D015967:Gene Expression Regulation, Viral; D007963:Leukocytes, Mononuclear / Q000821:virology*
chemical_list: D036022:Capsid Proteins