Resistance of line 63 chickens to reticuloendotheliosis‐virus‐induced bursa‐associated lymphomas

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Abstract
Chickens of lines 63 and 1515 × 71 were inoculated with the chick syncytial strain of reticuloendotheliosis virus (REV) or with the Rous‐associated virus‐1 of avian leukosis virus (ALV) at hatching. At 4, 10, 16, and 36 weeks post inoculation (PI), chickens were tested for REV‐and ALV‐induced viremia and antibody. The incidence of REV‐or ALV‐induced bursa‐associated lymphomas in line 63 chickens was compared with that in line 1515 × 71 chickens. Inoculation of REV at hatching resulted in immunological tolerance to the virus in line 63 but not in line 1515 × 71 chickens. Between 70% and 100% of line 63 chickens remained viremic and lacked REV antibody throughout the experimental period of 36 weeks. In contrast, ALV‐inoculated chickens of both lines had antibody by 16 weeks PI. The frequencies of REV‐and ALV‐induced bursa‐associated lymphomas in line 63 chickens were significantly lower than in line 1515 × 71 chickens. Further, the incidence of bursa‐associated lymphomas induced by REV in line 1515 × 71 chickens was significantly lower than that induced by ALV. These results suggest that: (1) the genetic constitution of the host may influence the immunological response to REV infection; (2) chickens resistant to ALV‐induced bursa‐associated lymphomas are equally resistant to such lymphomas induced by another unrelated avian retrovirus, REV; and (3) ALV is a more potent inducer of bursa‐associated lymphomas than REV.