Viruses that infect bacteria in digestive tract may play role in PAH: Study

People with pulmonary arterial hypertension (PAH) have less diversity among the viruses that infect bacteria in their digestive tracts, according to a new study.

These findings add to a growing body of research suggesting that the gut microbiome — the community of bacteria, viruses, and other microscopic organisms that make their home in human intestines — may play a role in PAH.

“These data extend microbiome research in pulmonary hypertension beyond bacteria, identifying viruses as key modulators of [the microbiome] … and highlighting the potential of [gut virus]-targeted strategies as novel therapeutic avenues,” researchers wrote.

The study, “Alterations in the fecal virome and bacteriome–virome interplay in IPAH,” was published in Respiratory Research.

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PAH is marked by abnormally high resistance in the vessels that carry blood from the heart through the lungs, which puts strain on the heart. In the most common form, known as idiopathic PAH or IPAH, the underlying causes of the disease are not clear.

Several previous studies have suggested that abnormalities in gut bacteria may be involved in PAH. But bacteria are not the only tiny organisms that live in the human digestive system — alongside the bacteria are whole communities of viruses, which routinely infect gut bacteria. These viruses may kill some species of gut bacteria; they also can participate in sharing genes between different bacterial cells.

Although many previous studies have looked at gut bacteria in PAH, these gut viruses have not been studied in-depth. To address this gap in knowledge, a team of scientists in China conducted in-depth profiling of both gut bacteria and gut viruses using fecal samples from 28 people with IPAH. Samples from 30 people without IPAH who were matched according to age and sex were also analyzed for comparison.

Collectively, these findings suggested that viruses may participate in gut ecological regulation by targeting specific bacterial hosts. Virus-bacterium interactions may jointly influence the development and progression of IPAH.

Results showed that the IPAH patients had marked abnormalities in the types of viruses that were living in their guts. In particular, the researchers noted that IPAH patients generally had less diversity of gut viruses. The changes in gut viruses were also accompanied by differences in gut bacteria — including bacteria that are known to make signaling molecules that regulate IPAH-associated biological processes such as inflammation.

“Collectively, these findings suggested that viruses may participate in gut ecological regulation by targeting specific bacterial hosts,” the researchers wrote. “Virus-bacterium interactions may jointly influence the development and progression of IPAH.”

In further analyses, the researchers found dozens of gut viruses that showed significant associations with markers of IPAH severity. For example, IPAH patients with higher levels of a type of gut virus called Uroviricota tended to have lower mean pulmonary arterial pressure, a measurement of blood pressure in the lungs’ vessels. This association indicated that Uroviricota viruses in the gut may have a protective effect, reducing the severity of IPAH, the researchers said.

The scientists stressed that this study was limited to a small number of patients. Also, it is not possible to say whether the identified changes are causes or consequences of disease development. As such, more studies are warranted to further explore the role of the imbalance in the gut viral population in PAH disease processes, the researchers wrote