Avian Acute Leukemia Viruses

Abstract

On the basis of their oncogenic properties, avian retroviruses can be divided into three groups: (a) sarcoma viruses (ASV), which cause solid tumors of the connective tissue after a short latency period; (b) lymphatic leukemia viruses (LLV), which cause a B-cell lymphoma only after a long latency period of approximately 6 months or more; and (c) acute leukemia viruses (ALV), which upon infection of young chickens rapidly bring about the death of the birds from a variety of different neoplasms, usually, but not exclusively, of the hematopoietic system (Purchase and Burmester 1973; Hanafusa 1977; Graf and Beug 1978). This classification is not absolute, in that there are overlaps in the oncogenic spectra of these viruses. For example, certain LLV have been shown to cause erythroblastosis and occasionally sarcomas (Purchase and Burmester 1973); similarly, certain ALV can also cause sarcomas (Rothe-Meyer and Engelbreth Holm 1933; Graf et al. 1977). However, by using this classification the seven field isolates of avian retroviruses listed in Table 1 have been grouped together as acute leukemia viruses. There is another isolate, reticuloendothelosis virus (REV-T), which is, by this definition, an ALV; however, since it is not related to the classical avian leukosis/sarcoma complex as judged by nucleic acid homology, it will not be included here. Interested readers are referred to Witter (1978) and Graf and Stehelin (1982). There are numerous reports in the literature regarding the isolation of other ALV; unfortunately, these strains are no longer available (see Graf and Beug 1978). Consequently, it is only the viruses listed in Table 1 which will be considered in this review.