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

Abstract

Pesq. Vet. Bras. 31(12):1090-1096, dezembro 2011 1090 RESUMO.-A biologia da infecção latente pelo herpesvírus bovino tipo 5 (BoHV-5) tem sido estudada em bovinos e coelhos, mas vários aspectos permanecem desconhecidos. Este artigo relata uma avaliação de ovinos jovens como modelo para o estudo da infecção latente pelo 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 hyperthermia. Examination of brain sections of ϐive lambs euthanized at day 30 pi by PCR revealed the presence of latent DNA in the trigeminal ganglia (TG, 5 out of ϐive), olfactory bulbs (OB, 5/5), pons (2/5), cerebellum (2/5) and cerebral cortex (1/5). Administration of dexamethasone (Dx, n=4) or ϐlumethasone (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 ϐive days (1-5) in Dx treated lambs (titers up to 10 2.8 TCID 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 distribution 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 treatment are promising ϐindings towards the use of lambs to study selected aspects of BoHV-5 latency.