The present invention provides, among other things, a polypeptide that binds with the gp120 envelope protein of HIV, in particular HIV-1, under physiological conditions, a nucleic acid that encodes such a polypeptide and can be expressed in a cell, a composition comprising such a polypeptide or nucleic acid or an antibody and a carrier therefor, a composition comprising a solid support matrix to which is attached an above-described polypeptide or an anti-antibody to a specified polypeptide sequence, a method of making an antibody to gp120, and a method of removing HIV from a bodily fluid.