Background
The ability to elicit broadly cross-reactive neutralizing antibodies is a major challenge in the development of an HIV-1 vaccine capable of neutralizing broad array of viruses in circulation. Nevertheless, a number of HIV-1 infected donors have broadly neutralizing sera and a handful of broadly neutralizing monoclonal antibodies have been isolated from clade B infected donors arguing that a vaccine strategy based upon eliciting broadly protective antibodies is feasible. These antibodies tend to display less breadth and potency against non-clade B viruses and they recognize epitopes on the virus that have so far proven refractory to incorporation into immunogens for elicitation of virus neutralizing responses.