Abstract: The present invention relates to novel polypeptides comprising a unique "chlamydial-specific" primary structural conformation and one or more of the biological properties of eukaryotic or prokaryotic stress-response proteins which are characterized by being the expressed products of an endogenous or exogenous DNA sequence in a eukaryotic or prokaryotic host cell. Sequences coding for part or all of the amino acid residues of the chlamydial HypA or HypB protein or for analogs thereof may be incorporated into autonomously replicating vectors employed to transform or transfect suitable procaryotic or eukaryotic host cells such as bacteria or vertebrate cells in culture. The HypB protein is a member of the family of stress response proteins referred to as HSP60. Products of expression of the DNA sequences display the identical physical, immunological, and histological properties as the chlamydial proteins isolated from natural, non-recombinant, organisms.