• Step-by-step accumulation
• Breast milk benefits
What is already known on this topic
The gut of newborns is usually not colonized by viruses, but populations of viruses start to develop during the first months of life. In some cases, these viruses can lead to gastrointestinal diseases. However, how the virus population in the gut—known as the virome—is assembled remains unclear.What this research adds
Researchers analyzed the viruses in the stool of newborns in the United States and Botswana. At birth, the infant gut was devoid of viruses, but by one month of life the number of viruses reached one billion per gram of stool. The first viruses to colonize the gastrointestinal tract are those who infect the gut-resident bacteria. At four months of life, human viruses, including potentially harmful ones, became more prominent. Human viruses were more abundant in the stool from babies who were fed only on formula milk compared with those fed on breast milk and formula milk.Conclusion
The findings suggest that breast milk can be protective against viral infections, and could help to develop strategies for the prevention of early gastrointestinal diseases.
The gut of newborns is usually not colonized by viruses, but populations of viruses quickly start to develop after birth and, in some cases, they can lead to gastrointestinal diseases. Now, a new study shows that breast milk can be protective against viral infections by reducing the accumulation of potentially harmful human viruses.
The results, published in Nature, could lead to better strategies for the prevention of early gastrointestinal diseases. What’s more, the findings “can help us better understand why some babies get sick and develop life-threatening infections in their first months of life,” says study senior author Frederic Bushman at the University of Pennsylvania.
To investigate how the virus population in the gut—known as the virome—is assembled in early life, Bushman and his team analyzed the viruses in the stool of hundreds of newborns in the United States and Botswana.
Step-by-step accumulation
The researchers collected stool samples from babies within a few days of birth, and again when the infants were one month old and four months old. At birth, the infant gut was devoid of viruses, but by one month of life the number of viruses reached one billion per gram of stool. At four months, the number of viruses were similar to the one-month samples.
Most of the first viruses to colonize the gastrointestinal tract were those who infect the gut-resident bacteria. By four months of life, however, human viruses, including Adenoviridae, Anelloviridae, Caliciviridae, and Picornaviridae, became more prominent. Some of these viruses may be able to make people sick.
Breast milk benefits
The researchers found that human viruses were more abundant in the stool from babies who were fed on formula milk compared with those fed partially or exclusively on breast milk.
But the infants’ home country also played a role in the accumulation of potentially harmful viruses. At four months, babies from Botswana were more likely to have these viruses in their stools compared to babies from the US.
“Location of the mom and baby seems to play a role, probably due to the kind and number of microorganisms babies are exposed to environmentally,” says study lead author Guanxiang Liang. “Nevertheless, Botswana-born babies still seemed to benefit from breastfeeding, whether exclusively or in addition to formula consumption” he says.
Next, the team plans to study how the development of the virome shapes a child’s growth and how the virus population in the gut influences outcomes in preterm birth.
