The functional properties of HNP1 generated by serine protease processing of proHNP1A were tested in microbicidal assays against S. aureus. Natural HNP1 and NE, PR3 and CG processed preparations possessed nearly identical dose-dependent bacteri- cidal activities against this organism (Fig. 6) . These data demonstrate that HNP1 generated by NE and PR3 processing of proHNP1A is functionally equivalent to native HNP1. Of note, the Asn-Met-HNP1, produced by CG processing of proHNP1A, had staphylocidal activity equivalent to that of the fully processed HNP1 isoform.