Feline leukaemia virus-specific proteins

This study was concerned with the polypeptides of feline leukaemia virus (FeLV), both the structural polypeptides of the virus particle and putative non-structural proteins which appear in FeLV-infected and transformed cells. In the first part of the work (Chapter Two) it was established that virus purification and storage methods did not cause serious losses which might invalidate further characterisation. At the same time, the extent to which purified virus preparations are contaminated with host cell proteins was investigated. The next chapter concerned the structural location of virus polypeptides within the virus particle, which was examined by protease digestion, enzymic radio-iodination and generation of sub-viral fractions. The results were similar to published findings for murine leukaemia viruses, at least with respect to the major surface glycoprotein and the major core protein. Comparison of the polypeptides of different FeLV strains, documented in Chapter Four, revealed essentially no detectable differences in the molecular size of the low molecular weight virion proteins. However, the major glycoprotein showed considerable strain to strain variation. Although this did not correspond to the virus subgroup (A, B or C) it did seem to be a stable property for a given virus strain, which may relate to the serotypic specificities of the glycoprotein. Purification of FeLV polypeptides and immunisation of heterologous species was the subject of study in Chapter Five. Highly reactive antisera to two virus polypeptides, p27 and p15, were raised and were utilised in immune precipitation studies to detect immunologically related molecules in purified virus and in infected cells. Attempts to raise antisera to FeLV glycoproteins, which would be expected to neutralise viral infectivity were largely unsuccessful. A more promising approach to this problem is suggested. Finally, in Chapters Six and Seven, the cell-membrane glycoproteins of cultured cells, both uninfected and infected with FeLV, were examined, and an attempt was made to elucidate the biochemical nature of the feline oncorna-virus associated cell membrane antigen (FOCMA). In the course of these studies, a number of interesting observations were made regarding the intracellular processing and shedding into culture medium of molecules related to virion structural proteins. However, the cat sera which were expected to react with FOCMA did not precipitate any additional molecule when compared to control sera. Possible reasons for this observation are discussed