Figure 2.

Vaccines that deal with HIV-1 variability. Construction of vaccines based on viral sequences in four viral isolates (top; simplified representation): horizontal lines indicate viral sequences; circles indicate sites of greatest variability between isolates (and potential escape mutations from CTL pressure; there may be more than two alternative sequences at each spot); and blue lines indicate regions of relative conservation (although in reality no region of HIV-1 is invariant). The mosaic vaccine (middle) is constructed to include the most common variants from the isolates in as few strands as possible while conserving naturally occurring sequence stretches. In the conserved region-containing vaccine (bottom), the relatively conserved regions (blue) are excised and then are “stitched” together (which creates an unnatural junctional region). The regions typically vary from 30 to 120 amino acids in length. Reproduced with permission from Ref. (63).