Bacterial infections can lead to the formation of abscesses — pockets of dead cells and debris surrounded by inflammatory immune cells. Bacteria multiply within abscesses, causing more inflammation and further damage to surrounding tissues.


Source: James Heilman, MD

Liver abscess

In severe cases, these immune reactions spread across the body, resulting in life-threatening organ failure, or sepsis. But how these abscesses form and what can be done to prevent them were previously not well understood.

Using preclinical models, investigators from Brigham and Women’s Hospital, a founding member of the Mass General Brigham healthcare system, identified a key mechanism that may be driving liver abscess formation: a process known as reverse transcription, in which DNA is synthesized from RNA.

Using RNA-sequencing, the researchers examined liver gene transcripts from mice infected with Escherichia coli. They found that abscess formation was associated with increased expression from endogenous retroviruses (ERVs), remnants of viruses that integrated into the mouse genome following past infections.

Inflammatory immune response

The authors hypothesized that DNA produced by ERVs can stimulate inflammatory immune responses, which damage surrounding cells and thus drive abscess development. If so, preventing the activity of the ERVs might prevent abscesses from forming.

To test this, the team treated mice with a cocktail of reverse transcriptase inhibitors — antiretroviral drugs also used to manage HIV infections — to block ERV DNA expression. They found that a single dose of the inhibitor cocktail was enough to prevent abscess formation, if delivered quickly after bacterial infection.

“Our findings suggest that drugs used to treat HIV can be used to prevent inflammatory complications of bacterial sepsis,” said corresponding author Matthew Waldor, MD, PhD, of the Division of Infectious Diseases.

“In mice, abscess susceptibility varies by sex and between tissues, so further work is needed to understand how antiretroviral drugs can prevent complications like bacterial sepsis in different individuals. But our study shows promise and points to a new way of thinking about treatment and prevention of deleterious consequences following bloodstream infection,” said first author Karthik Hullahalli, a Harvard graduate student in the Waldor lab at the Brigham.

Read more in PNAS.