The present invention relates to a cell strain capable of separating and multiplying an EB virus and derived from human lymphocyte cancer cells and a method of separating and multiplying the EB virus by means of said cell strain. The present cell strain can be applied to the separation and multiplication of the wild type virus present in various places, as well as to the separation and multiplication of the virus produced by homologous recombination etc. The virus newly separated and multiplied can be applied to vaccine etc. For the more efficient separation and multiplication of the virus, several markers can be inserted into the present cell strain.

This invention provides: a heteromyeloma, other than B6B11, capable of producing a trioma when fused with a human lymphoid cell, wherein the trioma is capable of producing a monoclonal antibody-secreting tetroma when fused with a second, antibody-secreting human lymphoid cell; a trioma fusion partner which does not produce antibody, obtained by fusing a heteromyeloma which does not produce antibody with a human lymphoid cell; a monoclonal antibody-secreting tetroma, obtained by fusing a trioma which does not produce antibody with an antibody-secreting human lymphoid cell; a method of producing a monoclonal antibody that specifically recognizes an antigen associated with a condition; a method of identifying an antigen associated with a condition using the trioma fusion partner; a method of diagnosing a condition using the trioma fusion partner; a method for preventing a condition; and compositions and therapeutic compositions comprising monoclonal antibodies produced using the trioma fusion partner.