Abstract: Novel and improved methods for diagnosis, prognosis, prophylaxis and therapy of viral infections are described. The novel methods employ a virus, viral antigen or fragment thereof in which "perturbation" of an oligosaccharide moiety renders the virus, viral antigen or fragment thereof more specifically recognizable or reactive with neutralizing antibody. As described, "perturbation" of an oligosaccharide moiety encompasses any modification that (1) alters the chemical or physical structure of a carbohydrate residue that is naturally present; (2) that removes, wholly or in part, a carbohydrate residue; and/or (3) that prevents or alters addition of a carbohydrate residue. A variety of methods for oligosaccharide "perpetuation" are also described.