The specification shows a method for obtaining a broadly neutralizing antibody (bNab), including screening memory B cell cultures from a donor PBMC sample for neutralization activity against a plurality of HIV-1 species, cloning a memory B cell that exhibits broad neutralization activity; and rescuing a monoclonal antibody from that memory B cell culture. The resultant monoclonal antibodies may be characterized by their ability to selectively bind epitopes from the Env proteins in native or monomeric form, as well as to inhibit infection of HIV-1 species from a plurality of clades. Compositions containing human monoclonal anti-HIV antibodies used for prophylaxis, diagnosis and treatment of HIV infection are provided. Methods for generating such antibodies by immunization using epitopes from conserved regions within the variable loops of gp120 are provided. Immunogens for generating anti-HIV1 bNAbs are also shown. Furthermore, methods for vaccination using suitable epitopes are shown. More specifically, the invention relates to a broadly neutralizing antibody (bNAb) comprising the polypeptide 4869-K15 (PGT-133), i.e to a monoclonal anti-HIV antibody comprising a heavy chain sequence comprising the amino acid sequence of SEQ ID NO: 420 and a light chain sequence comprising the amino acid sequence SEQ ID NO: 429.