Tetrazolium-based colorimetric assay for the detection of HIV replication inhibitors: revisited 20 years later.

Since its first description 20 years ago, the tetrazolium-based colorimetric (MTT) assay using MT-4 cells for the detection of anti-HIV compounds has been widely used. This method, which remains popular, provides more information than more recently developed methods and, therefore, represents a useful methodology on its own or in combination with other screening systems. The replication of HIV in MT-4 cells is usually monitored 5 d after infection; therefore, this protocol can be divided into three steps: the infection (at day 0), an incubation period (5 d) and the evaluation (at day 5). The long-standing and intensive use of the MTT method has taught users of the limitations and, equally importantly, the unexpected advantages of the MT-4/MTT assay. The use of this method can be extended to antiviral testing of compounds against other cyto-destructive viruses.