Methods: 913 Pa clinical isolates were collected from diverse patients and geographical locations in 2004-2014. Whole genome sequencing of the full collection was performed via MiSeq 2 x 250 runs (Illumina®). PcrV and Psl expression was detected by immunoblotting and ELISA, respectively. The crystal structure of anti-PcrV fab and PcrV fragment complex-crystals was solved at 2.8 Å resolution. MEDI3902 activity against representative isolates were tested in cytotoxicity and opsonophagocytosis assays and in a murine pneumonia model.
Results: Whole genome sequencing revealed intact pcrV and psl genetic elements in 99% and 94% of isolates, respectively. We identified 46 variants of PcrV that were all bound by the anti-PcrV moiety of MEDI3902 and confirmed through crystal structure analysis that antibody-antigen contact residues were preserved in all variants. Similarly, anti-Psl binding was confirmed for selected isolates containing the complete Psl operon and strains lacking non-essential psl genes. Importantly, 99.9% of isolates contained the full complement of either genetic element. Consistent with these results, we observed potent MEDI3902 activity against diverse strain types, including strains that expressed only a single target.
Conclusion: Our results indicate PcrV and Psl are highly prevalent in recent clinical isolates from around the world, suggesting MEDI3902 can mediate broad coverage against Pa.
D. E. Tabor, Astra Zeneca: employee , Salary .