Patogenia da infecção aguda e latente pelo herpesvírus bovino tipo 5 e por recombinante com deleção no gene da timidina quinase em ovinos

• Ano de defesa: 2013
• Autor(a) principal: Cadore, Gustavo Cauduro
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Santa Maria; BR; Medicina Veterinária; UFSM; Programa de Pós-Graduação em Medicina Veterinária
• Palavras-chave em Português: Herpesvírus recombinantes; Sítios de latência; TK; Modelo animal; Recombinant herpesvirus; Sites of latency; Animal model; CNPQ::CIENCIAS AGRARIAS::MEDICINA VETERINARIA
• Link de acesso: http://repositorio.ufsm.br/handle/1/4086

Bovine herpesvirus type 5 (BoHV-5) is an alphaherpesvirus associated with meningoencephalitis, an important disease of cattle in South America. Alphaherpesvirus recombinants have been used to study the function of gene products and also for vaccine production. In particular, the gene encoding the enzyme thymidine kinase (tk) has been deleted to produce attenuated strains. Thymidine kinase is required for efficient replication of these viruses in the central nervous system (CNS), and its deletion or inactivation is associated with reduction of virulence. Thus, the present study aimed to investigate the pathogenesis and to characterize clinically and virologically the acute and latent infection by BoHV-5 (strain SV-507/99) and by tk-deleted recombinant (BoHV-5tkΔ) in lambs. Chapter 1 reports the characterization of latent by BoHV-5 infection in lambs. During acute infection, lambs inoculated with BoHV-5 (SV-507/99) shed virus in nasal secretions during up to 11 days and developed viral neutralizing antibodies in titers ranging from 16 to 128. Administration of corticosteroids during latency (day 65 pi) resulted in virus reactivation and shedding for 3 to 8 days in titers up to 64. Thus, it is proposed that sheep can be used as animal models for studying the biology of latent infection by BoHV-5. In Chapter 2, was investigated the ability of BoHV-5tkΔ to establish and reactivate latent infection in lambs. After viral inoculation, the recombinant virus retained the ability to replicate in the nose of the lambs. At day 40 pi, latent viral DNA was detected in the trigeminal ganglia (TG) in all inoculated animals. However real time PCR demonstrated a significantly reduced amount of recombinant DNA (9.7-fold less, p<0.001) compared to the parental virus. Following dexamethasone (Dx) treatment, infectious virus was not detected in nasal secretions of the animals inoculated with the recombinant virus, contrasting with virus shedding by lambs inoculated with the parental virus. Nevertheless, some nasal swabs from animals inoculated with BoHV-5tkΔ were positive for viral DNA, indicating low levels of reactivation. Thus, BoHV-5 TK activity is not required for the establishment of latency, but seems critical for efficient virus reactivation. Chapter 3, reports the ability of BoHV-5 and BoHV-5tkΔ to establish and reactivate latent infection in lymphoid tissues. During latent infection, viral DNA was detected in TGs, pharyngeal and palatine tonsils and in retropharyngeal lymph node of all sheep inoculated with both viruses (parental and recombinant). At day 40 pi, Dx was administered to the animals to induce viral reactivation. Viral mRNA of BoHV-5 glycoprotein B was detected in TGs, retropharyngeal lymph node and tonsils of lambs inoculated with the parental virus. In animals inoculated with BoHV-5tkΔ, gB mRNA was detected only in tonsils. Therefore, it is suggested that lymphoid tissues are also sites of latency by BoHV-5 and the recombinant BoHV-5tkΔ, and that viruses can be reactivated from these sites. However, reactivation of recombinant virus appears to occur only in lymphoid tissues and not in neural tissues. In summary, the presented results contribute for the understanding of the pathogenesis and characterization of infection by BoHV-5 and BoHV-5tkΔ.