The present invention provides nucleic acids, proteins and vectors for a method of nucleic acid, including DNA, immunization of a host, including humans, against disease caused by infection by a strain of Chlamydia, specifically C. trachomatis. The method employs a vector containing a nucleotide sequence encoding a Mgp002 polypeptide of a strain of Chlamydia operably linked to a promoter to effect expression of the gene product in the host. Truncated forms of the full-length Mgp002 gene are useful immunogens for protecting against disease caused by infection with Chlamydia. The invention further provides recombinant Mgp002 protein useful for protecting against disease caused by infection with Chlamydia.