Optimization of in situ cellular ELISA performed on influenza A virus-infected monolayers for screening of antiviral agents

Viral susceptibility testing has been traditionally performed by the plaque reduction assay (PRA) which is laborious, time consuming, relatively expen sive, and requires subjective input by the reader. An in situ cellular enzy me-linked immunosorbent assay (ELISA) has been developed with the potential to overcome many of the limitations of PRA and has been applied to a varie ty of viruses. This study establishes the specific conditions necessary for susceptibility testing of influenza A virus to antiviral agents such as am ount of inoculum size, duration of incubation, fixative type, and cell numb er; factors which are critical to the performance of the in situ cellular E LISA. In situ cellular ELISA was found to correlate strongly with the plaqu e assay (PA) (R-2 = 0.997, P < 0.002). Both assays were applied to test the susceptibility of influenza A virus to a new antiviral emulsion agent and yielded comparable data. The optimized in situ cellular ELISA can serve as a reliable assay for the rapid screening of large numbers of antiviral agen ts. (C) 1999 Elsevier Science B.V. All rights reserved.