Morphological and antigenic variations of human T cell leukemia virus type I particles in human lymphocytes

HTLV-I particles grown in 4 human lymphocyte cultures were observed by electron microscopy. Particles in all cell lines showed marked size and structural variations that were characteristic of each cell line. Profiles of size-distributions were found to be similar among virus particles of the same origin in different cell lines. Immunogold electron microscopy using monoclonal antibody to HTLV-I-p15, -p19, or -p24 revealed varying reactivities of individual particles. By double-labeling technique using antibody to HTLV-I-p19 or -p24, particles were found to be classifiable into 4 groups: p19+p24+, p19+p24-, p19-p24%, and p19-p24-. Each cell line showed the characteristic profile of distributions of virus particles of each group as observed at different in vitro passage levels. These antibodies reacted with certain structures in the extracellular space and in the cytoplasm. Results of this study demonstrate variations in morphology and antigenicity, as well as the morphogenesis of HTLV-I particles in different host cells.