The History of HIV-1 Biological Phenotypes Past, Present and Future

HIV-1 primary isolates have been classified according to their behavior in tissue culture into two distinct groups based on their growth kinetics, cytopathology and cellular tropism. Classification by growth kinetics and cytopathology is indicative of replication rate and syncytium induction in activated peripheral blood mononuclear cells (PBMC). Accordingly, the terms slow/low and rapid/high for replication pattern and non-syncytium inducing (NSI) and syncytium inducing (SI) for cytopathology were introduced [1–3]. In general, the terms SI and NSI correspond broadly to the rapid/high an