title: In vitro reactivation of latent equid herpesvirus-1 from CD5+/CD8+ leukocytes indirectly by IL-2 or chorionic gonadotrophin.
abstract: IL-2 and equine chorionic gonadotrophin (eCG) initiated reactivation of equid herpesvirus-1 (EHV-1) from venous lymphocytes at a frequency of 1/10(-5). Indirect immunofluorescence showed that > 80% of virus-positive leukocytes were CD5+/CD8+ with the remaining 20% being CD5+/CD8-/CD4-. Cocultivation demonstrated that the reactivated virus was infectious. In addition, virus was reactivated in vitro from leukocytes of > 70% of horses by the mitogens phytohaemagglutinin (PHA) and pokeweed mitogen (PWM). Transfer of supernatants showed that IL-2 and eCG acted indirectly by causing the release of other mediators from adherent cells; these mediators then reactivated EHV-1 from T cells. Blocking experiments with anti-IL-2 showed that PWM and PHA acted via IL-2 but that eCG did not. This is the first clear definition of the lymphoid cells that harbour latent EHV-1 in vivo and correlates with current RT-PCR and in situ hybridization of latency-associated transcripts in lymphocytes. This method of reactivation in vitro can be used to detect horses carrying latent EHV-1 in vivo and also has the potential to dissect the sequence of events involved in reactivation in vitro.
authors.affiliation: Department of Pathology and Infectious Diseases, Royal Veterinary College, London, UK.
authors.forename: D J
authors.initials: DJ
authors.lastname: Smith
authors.forename: J
authors.initials: J
authors.lastname: Iqbal
authors.forename: A
authors.initials: A
authors.lastname: Purewal
authors.forename: A S
authors.initials: AS
authors.lastname: Hamblin
authors.forename: N
authors.initials: N
authors.lastname: Edington
mesh_terms: D000818:Animals; D018956:CD5 Antigens; D018414:CD8-Positive T-Lymphocytes / Q000821:virology*; D002478:Cells, Cultured; D006063:Chorionic Gonadotropin / Q000378:metabolism* / Q000494:pharmacology; D004861:Herpesvirus 1, Equid / Q000254:growth & development* / Q000502:physiology; D006736:Horses; D006801:Humans; D007376:Interleukin-2 / Q000378:metabolism* / Q000494:pharmacology; D016133:Polymerase Chain Reaction; D011817:Rabbits; D014775:Virus Activation; D017735:Virus Latency
chemical_list: D018956:CD5 Antigens; D006063:Chorionic Gonadotropin; D007376:Interleukin-2