Molecular cloning of DNA coding for outer membrane proteins of Haemophilus influenzae type b

DNA from Haemophilus influenzae type b was cloned in Escherichia coli with a vector lambda gt11 Amp1. Clones producing antigens reactive with hyperimmune rabbit antisera were identified by colony radioimmune assay. A second screening with hyperimmune serum adsorbed with intact H. influenzae type b bacteria was used to identify those clones producing surface-exposed outer membrane proteins. The proteins expressed in E. coli were coupled to Sepharose and used to affinity purify antibodies which were tested for reactivity with outer membrane vesicles. It was found by Western blotting that the clones were producing antigens corresponding to Mr 49,000, 39,500, and 35,000 major outer membrane protein or antigens of H. influenzae type b. Additional clones could be detected by human serum, but their reactivity was not removed when serum was adsorbed with intact bacteria. One of these studied in more detail was found to produce an antigen present in H. influenzae type b lysate but not in outer membrane vesicle preparations.