Given the predicted low-titer inoculum driving HIV-1 sexual transmission, a vaccine capable of eliciting antibodies that neutralize a broad spectrum of viral strains could potentially reduce or prevent infection. It has been anticipated that the identification of broadly neutralizing mAbs from HIV-1 infected individuals, and the characterization of their cognate epitopes will be instrumental in the design of immunogens capable of eliciting such a broad neutralizing response [12] . This idea has led to a major international cooperative effort within consortia of laboratories with complementary expertise in human immunology, structural biology and vaccine design [13, 14] .