Evolutionary and immunological implications of contemporary HIV-1 variation

Evolutionary modelling studies indicate less than a century has passed sinc e the most recent common ancestor of the HIV-1 pandemic strains and, in tha t time frame, an extraordinarily diverse viral population has developed. HI V-1 employs a multitude of schemes to generate variants: accumulation of ba se substitutions, insertions and deletions, addition and loss of glycosylat ion sites in the envelope protein, and recombination. A Comparison between HIV and influenza virus illustrates the extraordinary scale of HIV variatio n, and underscores the importance of exploring innovative HIV vaccine strat egies. Deeper understanding of the implications of variation for both antib ody and T-cell responses may help in the effort to rationally design vaccin es that stimulate broad cross-reactivity. The impact of HIV-1 variation on host immune response is reviewed in this context.