A method for screening a pathogenic microorganism for a secreted or cell-surface protein potentially useful as a vaccine antigen involves the step of identifying proline-rich proteins, either as the amino acid level, or preferably at the DNA level by employing PCR. Suitable consensus sequences are described as (PXm)nP or (PPXq)nPP wherein: P is proline; X is any amino acid, m is from 1 to 5; q is 1 or 2; and n is 2 or more.
