Susceptibility of human immunodeficiency virus to antiviral agents measured by infectious virus yield reduction.

Under single growth cycle conditions in C8166 lymphoblastoid cells human immunodeficiency virus shows a replication curve which is completed at 24 h post-infection. At lower multiplicity of infection virus yield peaks at approximately 72 h post-infection but in both cases the titer of the virus released in the medium is negligible with respect to that which remains cell-associated. A method based on back-titration of virus in cryolysates of C8166 cells infected with HIV and treated with antiviral compounds has been used to evaluate HIV sensitivity to such agents. Under single growth cycle conditions dose response curves appear linear and permit rapid and accurate determination of the endpoint activity. Under multiple growth cycle conditions the inhibitory activity may be measured during the exponential growth phase, at 48 h post-infection. This method, which directly measures production of infectious virus rather than indirect probes of viral replication such as reverse transcriptase or antigen production, offers the advantage of a precise determination of the degree of activity of antivirals also acting on viral assembly or release.