The present invention relates to methods for the recombinant expression of Chlamydia major outer membrane protein (MOMP) comprising transforming a population of E. coli host cells with an expression vector comprising a nucleic acid molecule that encodes Chlamydia MOMP and encodes a leader sequence for targeting the MOMP to the outer membrane of the cell, wherein the nucleic acid molecule is operatively linked to a promoter. The method of the invention allows expression of MOMP in the outer membrane of the cell, which leads to protein folding that is more like native MOMP relative to a MOMP protein that is expressed intracellularly. Also provided by the invention are uses of the recombinant MOMP in pharmaceutical compositions and methods for the treatment and/or prophylaxis of Chlamydia infection and/or the effects thereof.