1990 by standard techniques to form this fusion protein a bamhi site may be engineered into the sequence at the appropriate location again by standard techniques the gene fusions are introduced into a vaccinia virus expression plasmid as described herein and inserted into the genome of the vaccinia wr strain by homologous recombination and selection for growth in mycophenolic acid falkner at al j virol 62 1849 1854 1988 boyle et al gene 65 123 128 1988 flow cytometric analysis is used to examine expression by the vaccinia recombinants of the cd4 tyrosine kinase fusion proteins at the cell surface immunoprecipitation of cells infected with the vaccinia recombinants is used to confirm the results as described above the efficacy of cd4 chimeras may be tested by any of the calcium mobilization or cytolysis assays described herein in one particular example a model target effector system based on cd4 recognition of the hiv envelope gp120 gp41 complex is created hela cells are infected with recombinant vaccinia viruses expressing gp120 gp41 chakrabarti et al nature 320 535 537 1986 earl et al j virol 64 2448 2451 1990 and labeled with 51 cr the labeled cells are incubated with cells from a human allospecific cd8 cd4 cytotoxic t.