Table 2.

Factors encouraging us to continue searching for human retroviruses

1. The discovery of bovine leukemia virus (minimally replicates, difficult to find)

2. Technological advances – A. A sensitive specific assay for a footprint of a retrovirus, namely, reverse transcriptase. B. Capacity to grow significant numbers of primary human T cells in liquid suspension culture giving us access to virus detection and isolation, namely by using IL-2.

3. Discovery of a retrovirus causing leukemias in a species close to man, namely GaLV.

4. A documented example of a retrovirus transmission from one species of primates to another, namely GaLV from a gibbon ape to a wooly monkey [26].

5. Purification and characterization of reverse transcriptase from a patient with an adult lymphocytic leukemia (type unknown) 1972 [15].