RESUMO
Microbial genomes from ancient chickens uncover the drivers of pathogenicity.
Assuntos
Galinhas , Genoma Viral , Mardivirus , Doença de Marek , Animais , Galinhas/microbiologia , Virulência/genética , Doença de Marek/história , Doença de Marek/virologia , Mardivirus/genética , Mardivirus/patogenicidadeRESUMO
The pronounced growth in livestock populations since the 1950s has altered the epidemiological and evolutionary trajectory of their associated pathogens. For example, Marek's disease virus (MDV), which causes lymphoid tumors in chickens, has experienced a marked increase in virulence over the past century. Today, MDV infections kill >90% of unvaccinated birds, and controlling it costs more than US$1 billion annually. By sequencing MDV genomes derived from archeological chickens, we demonstrate that it has been circulating for at least 1000 years. We functionally tested the Meq oncogene, one of 49 viral genes positively selected in modern strains, demonstrating that ancient MDV was likely incapable of driving tumor formation. Our results demonstrate the power of ancient DNA approaches to trace the molecular basis of virulence in economically relevant pathogens.
Assuntos
Galinhas , Herpesvirus Galináceo 2 , Doença de Marek , Animais , Galinhas/virologia , Herpesvirus Galináceo 2/classificação , Herpesvirus Galináceo 2/genética , Herpesvirus Galináceo 2/patogenicidade , Linfoma/virologia , Doença de Marek/história , Doença de Marek/virologia , Virulência/genética , FilogeniaRESUMO
Shortly after the isolation of Marek's disease (MD) herpesvirus (MDV) in the late 1960s vaccines were developed in England, the United States, and The Netherlands. Biggs and associates at the Houghton Poultry Research Station (HPRS) in England attenuated HPRS-16, the first cell-culture-isolated MDV strain, by passaging HPRS-16 in chick kidney cells. Although HPRS-16/Att was the first commercially available vaccine, it never became widely used and was soon replaced by the FC126 strain of herpesvirus of turkeys (HVT) vaccine developed by Witter and associates at the Regional Poultry Research Laboratory (now Avian Disease and Oncology Laboratory [ADOL]) in East Lansing, MI. Ironically, Kawamura et al. isolated a herpesvirus from kidney cell cultures from turkeys in 1969 but never realized its potential as a vaccine against MD. Rispens of the Central Veterinary Institute (CVI) developed the third vaccine. His associate, Maas, had found commercial flocks of chickens with MDV antibodies but without MD. Subsequently, Rispens isolated a very low pathogenic strain from hen number 988 from his MD antibody-positive flock, which was free of avian leukosis virus and clinical MD. This isolate became the CVI-988 vaccine used mostly in The Netherlands. During the late 1970s, HVT was no longer fully protective against some new emerging field strains. The addition of SB-1, isolated by Schat and Calnek, to HVT improved protection against the emerging very virulent strains. In the 1990s CVI-988 became the worldwide vaccine gold standard. This review will present data from published papers and personal communications providing additional information about the exciting 15-yr period after the isolation of MDV to the development of the different vaccines.
