Currently, the best options for treating pneumonia are taking antiobiotics either orally or intravenously – but as a lung infection, the most direct route would be inhalable drugs. Now researchers at Georgia Tech have made a step towards that goal, with breathable viruses that hunt down and kill disease-causing bacteria in the lungs.

Bacteriophages are viruses that target specific strains of bacteria. They were explored in the early 20th century as potential treatments for infection, but fell by the wayside once antibiotics were discovered. However, with superbugs increasingly developing antibiotic resistance, scientists have once again started investigating how they might be used in medical contexts.

The Georgia Tech team decided to try to put phages to work on lung infections like pneumonia, or those that recur in patients with cystic fibrosis. To do so, they grew the viruses on particles of a biocompatible polymer, then dried them out into a powder that could be inhaled.

"When we immobilized the phage on the particles, we could retain good activity for days – as long as two weeks at room temperature," says Andrés García, an author of the study. "We could store these particles, and when we delivered them to mice, get good distribution through the lungs. We believe the particles help stabilize the phage and improve the distribution in the lungs."

In tests on mice with pneumonia, the team found that the treatment cleared up the infection, while those that didn't receive it died. Other mice were engineered to have cystic fibrosis-like lungs, and the phage treatment significantly reduced the population of bacteria in their lungs.

The polymer particle base also seems to be important for helping deliver the phage, since the viruses alone weren't as effective as those piggybacking on particles. The polymer material was found to disappear from the animals' bodies after a few days, and the phage don't linger either; once the target bacteria are all dead, the viruses are soon to follow. In another test, the team sprayed the powder onto bacteria biofilms, and found that the treatment was able to kill different strains with no signs of resistance developing.

"Treatment with antibiotics often makes space for other opportunistic bacteria to take hold," says Nael McCarty, co-author of the study. "Phage therapy could complement existing therapies without worsening antibiotic resistance. The technique developed and tested through this important collaboration could address one of the major challenges we have with phage therapy, which is delivery."

The treatment isn't without its hurdles, though. The team says that phages produce harmful toxins and can trigger immune responses, so future work will go into finding ways around these issues. Further study will also test the technique in larger animals, against mixtures of bacteria, and against chronic infections.

The research was published in the journal Nature Biomedical Engineering.

Source: Georgia Tech

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