Mitsuru Konn

A subline of the P3 (Jijoye) Burkitt lymphoma cell line, designated P3HR-1, initially contained 1 to 5% of cells which were positive by indirect immunofluorescence with selected human sera. After 4 months of propagation, this cell line regularly showed 15 to 40% reactive cells. Antigen(s) in the cell line which was reactive by immunofluorescence was similar or identical to that found in several other Burkitt tumor cell lines in previous studies. When the cells were incubated at 35 or 32 C for 9 to 15 days without refeeding, more than 50% of the cells became immunofluorescence-positive. Thirteen different cultures of P3HR-1 cells, which contained up to 75% immunofluorescence-positive cells, were thin-sectioned and examined by electron microscopy. The percentage of cells containing herpes-type virus particles in the cultures varied from <3 to 78%. There was generally a good correlation between the number of immunofluorescent cells and the number of cells containing virus particles. The number of virus particles per cell section ranged from 1 to more than 100. These results strongly support the hypothesis that the immunofluorescent antigen is related to the presence of the herpes-type virus particle in the cells.

Replication of the herpes-type virus in the P3HR-1 Burkitt lymphoma cell line was studied. The cell cultures with 10(6) viable cells/ml were incubated at 33 C for 15 days. The amount of virus in both the cell and fluid portions of the cultures was determined by the loop-drop particle-counting procedure with electron microscopy. An apparent growth curve of the virus was constructed. The maximal cell-associated virus, 10(10) virus particles in an 80-ml culture, was observed after 9 days of incubation. The maximal extracellular virus, 2.5 x 10(9) particles per culture, was observed at the 12th day. About 10% of the released virus particles were enveloped. Under these conditions, there was little or no cell multiplication, but the percentage of immunofluorescent cells reactive to a selected human serum (probably indicating the presence of virus in the cells) increased to a maximum of 50% at the 9th day.

was similar or identical tothatfoundinseveral other Burkitt tumorcell lines inprevious studies. Whenthecells wereincubated at 35or 32C for9to15dayswithout refeeding, more than50%ofthecells became immunofluorescence-positive. Thirteen different cultures ofP3HR-1cells, which contained up to75%immunofluorescence-positive cells, were thin-sectioned and examined byelectron microscopy. Thepercentage ofcells containing herpes-type virus particles inthecultures varied from<3to78%.There was generally a good correlation between thenumberofimmunofluorescent cells andthenumberofcells containing virus particles. Thenumberofvirus particles percell section ranged from 1 tomore than100. Theseresults strongly support thehypothesis thattheimmunofluorescent antigen isrelated tothepresenceoftheherpes-type virus particle inthe cells.