Immunologically active agents are described, including isolated Pneumocystis A 12 protein or polypeptides immunogenic conjugates containing Pneumocystis A 12 protein or polypeptide of the present invention antibodies recognizing the Pneumocystis A 12 protein or polypeptide or the immunogenic conjugates of the present invention and nucleic acid molecules that encode the Pneumocystis A 12 protein or polypeptide of the present invention, as well as DNA constructs, expression vectors, and host cells that contain the nucleic acid molecules. Disclosed uses of the antibodies, immunogenic conjugates, and DNA constructs include inducing passive or active immunity to treat or prevent pathogen infections, particularly by a Pneumocystis organism, in a subject.
