While there has been considerable interest in conserved epitopes, less attention has been paid to more variable epitopes that might be useful if administered in the form of a polyvalent vaccine. Of particular interest are the epitopes that drive the autologous neutralizing antibody response in infected individuals. These epitopes may be quite variable, but recent evidence suggests that there are constraints on the extent of variation the virus can tolerate in these regions [27, 28] . Detailed molecular and immunologic studies of the autologous neutralization response would enhance our understanding of viral determinants that are vulnerable to antibody attack. Similarly, it is possible that combinations of antibodies will have desirable additive or synergistic effects on virus neutralization [29-32]. An example is seen in how soluble CD4 binding rearranges the structure of gp120 to expose the highly conserved coreceptor binding domain, which allows antibody binding and virus neutralization to occur [33, 34] . Such effects of antibodies might be discovered by applying high throughput screening methods to the plethora of existing MAbs as well as new MAbs that become available in the future.