Reativação e distribuição do DNA latente do herpesvírus bovino tipo 5 no encéfalo de ovinos infectados experimentalmente

Abstract

The biology of latent infection by bovine herpesvirus type 5 (BoHV-5) has been studied in cattle and rabbits, yet many aspects remain poorly understood. We herein investigated the suitability of lambs to investigate aspects of BoHV-5 latency. Thirteen six-month-old lambs inoculated intranasally (IN) with BoHV-5 strain SV-507/99 (titer of 10 6.8 TCID 50/ mL) shed the virus in nasal secretions in titers up 10 5.5 TCID 50/mL, during up to 11 days, developing virus neutralizing (VN) titers of 16 to 128 at day 30 post-inoculation (pi). The inoculated animals developed only a mild serous nasal secretion and transient hyperther- mia. Examination of brain sections of five lambs euthanized at day 30 pi by PCR revealed the presence of latent DNA in the trigeminal ganglia (TG, 5 out of five), olfactory bulbs (OB, 5/5), pons (2/5), cerebellum (2/5) and cerebral cortex (1/5). Administration of dexame- thasone (Dx, n=4) or flumethasone (FluM, n=4) to eight latently infected lambs at day 65 pi resulted in virus reactivation and shedding by 3 out of 4 individuals in each group. Virus shedding in nasal secretions started at day 3 post-treatment and lasted up to five days (1-5) in Dx treated lambs (titers up to 10 2.8TCID 50/mL), was delayed and lasted up to three days (1-3) in FluM-treated lambs (titers up to 10 2.1 TCID 50/mL). PCR examination of the brains of animals submitted to reactivation, at day 30 post-treatment, showed a pattern of distri- bution of latent viral DNA fairly similar to that found in those not submitted to reactivation. In summary, the ability of BoHV-5 to establish latent infection, the consistent colonization of TGs and OBs by latent viral DNA and virus reactivation induced by corticosteroid treat- ment are promising findings towards the use of lambs to study selected aspects of BoHV-5 latency.