Infection and Tumor Formation in Chickens By Avian Leukosis Virus

Lymphoid leukosis in chickens is a disease which arises from the result of complicated interaction between avian leukosis virus (ALV) as a pathogenic organism and chicken as a host. This report is intended to outline our present knowledge about genetic resistance of chickens in lymphoid leukosis. The defense of host in infectious disease could be considered dividing it into two: one as a working defense when a virus infects and the other as a working defense when a disease arises. Also in the case of lymphoid leukosis it could be considered in dividing into two by recent progress of study on avian tumor virology. ALV is closely related to Rous sarcoma virus (RSV) in chemical as well as biological properties, and they are the members of avian leukovirus as classified by Fenner.4) The recent studies have· revealed that all the avian leukovirus share common antigen of core proteins and they could be divided into four subgroups (A, B, C, D,) by the difference in characteristics of the enve~ lope : these four subgroups are classified by the neutralizing test which reflects the function of surface· of virion, and by the specificity in host range and in interference pattern. It is also an important feature of avian leukovirus that they readily produce phenotypic mixers between the viruses belonging to different subgroups by their coinf ection. For example, if subgroups A and B virus infect together a single cell, a virus which has genome of subgroup A and envelope of subgroup B, and a virus which has genome of subgroup B and envelope of subgroup A etc. are formed, not to mention that each virus is formed independently, of which a special example is a virus called pseudotype of RSV which has genome of RSV and envelope of ALV of each subgroup. As the characteristics of the virus control led by envelope are all the same· with those of ALV which offers envelope, they are used as indicator viruses to examine the antigenicity and the host range of each ALV.