Abstract: Provided are antibodies capable of binding to a particular epitope or specifically binding to LF or LTx and enhancing the activity of the LF or LTx relative to the LF or LTx absent the antibody binding.

Abstract: Provided are antibodies capable of binding to a particular epitope or specifically binding to LF or LTx and enhancing the activity of the LF or LTx relative to the LF or LTx absent the antibody binding.

Abstract: Provided are peptides capable of reducing the ability of antibodies to stimulate the activity of B. anthracis lethal factor. These peptides may be used to reduce activity of LF in a sample containing an LF activity enhancing antibody, to prevent the possibility of LF enhanced activity in a sample or subject, or as a therapeutic to reduce LF activity in a subject that may-have one or more antibodies that enhance LF activity. Also, provided are immunogens that may be used in a vaccine to confer protection to a subject. An immunogen does not include a sequence including the wild-type amino acids present in LF residues 677-680, or mutations of amino acids 677-680 that will also generate antibodies that enhance LF activity.