Pre-existing Antiphage Immunity in Cystic Fibrosis Patient Highlights Need for Comprehensive Evaluation in Phage Therapy

A new case study published in Nature Medicine reveals that pre-existing antibodies in a cystic fibrosis patient may have neutralized therapeutic bacteriophages, contributing to treatment failure in a compassionate-use phage therapy attempt.

The 22-year-old male patient had a chronic, drug-resistant infection with Bordetella bronchialis and received personalized phage therapy after conventional antibiotics failed. Despite the intervention, the infection progressed, ultimately leading to a fatal outcome.

Analysis of longitudinal serum samples showed the presence of pre-existing antibodies that reacted not only with the infecting bacterial strain but also with the administered therapeutic phage. These cross-reactive antibodies are believed to have bound to and inactivated the phage particles before they could exert their antibacterial effect.

In addition to immune interference, researchers identified bacterial heteroresistance within the Bordetella bronchialis population — a subpopulation of bacteria with inherently reduced susceptibility to the phage. This dual mechanism of immune-mediated neutralization and bacterial variability likely acted in tandem to undermine the therapy’s effectiveness.