Study of subgroup J avian leukosis virus persistence in meat-type chickens

Subgroup J Avian Leukosis Virus (ALV J) is economically important to the poultry industry since it causes a variety of neoplastic and non-neoplastic syndromes primarily in meat-type chickens. A series of experiments were conducted to better understand ALV J-induced viral persistence, neutralizing antibody (NAb) response, and oncogenicity in meat-type chickens.; The aim of the first objective was to study the effect of viral strain (ADOL Hc1, ADOL 4817, and ADOL 6803) and dose (100 and 10000 TCID50 ), and age at infection (5th day of embryonation and day of hatch) on ALV J persistence and oncogenicity in meat-type chickens.; The aim of the second objective was to confirm the high incidence of V+A+ infection status in meat-type chickens infected at hatch with an ALV J molecular clone ADOL pR5-4 as demonstrated in the first objective with ALV J field isolates. In addition, autologous and heterologous virus neutralization (VN) was done to test for the emergence of NAb escape variants in persistently V+A+ meat-type chickens.; The goal of the third objective was to study the effect of porcine Adrenocorticotrophin (ACTH)-induced stress on chickens that had cleared viremia with an efficient NAb response. The results demonstrated that only meat-type chickens that were exposed to ALV J at hatch but not at 32 weeks of age had reverted to viremia and cloacal shedding (33%) 10 days post ACTH-induced stress.; The aim of the fourth objective was to detect ALV J gp85 antigen by immunohistochemistry (IHC) as well as provirus by polymerase chain reaction in tissues from meat-type and ADOL line 0 chickens with various infection status. The results demonstrated that ALV J proviral DNA could be demonstrated in both viremic as well as seroconverted non-viremic chickens whereas gp85 expression was restricted to chickens exhibiting overt viremia in the presence or absence of antibody response.; The aim of the fifth objective was to characterize ALV J-induced histiocytic proliferative lesions by histochemistry and IHC. The results demonstrated that these lesions only appear in persistently viremic chickens infected at hatch and are comprised of myeloid cells with histiocytic differentiation. (Abstract shortened by UMI.)...