Scientists are embarking on an ambitious initiative known as the Human Virome Project, aiming to identify the myriad viruses residing within the human body, using advanced artificial intelligence technology. While most people are familiar with harmful viruses, such as those causing influenza and smallpox, it’s said there are trillions of viruses cohabiting within healthy humans, many of which are non-threatening and may even offer benefits.
Researchers from five universities have come together to analyze the human virome, the collection of viruses inhabiting our bodies. This unprecedented five-year project is backed by $171 million from the federal government. Collecting samples from thousands of volunteers, scientists are set to examine saliva, stool, blood, milk, and numerous other specimen types, as part of their goal to understand how these viruses impact human health, according to Frederic Bushman, the microbiologist from the University of Pennsylvania leading the project.
The notion of the human virome dates back over a century. Early studies unveiled bacteriophages, viruses capable of infecting bacteria, within human fecal samples, later discovered to exist not just in the gut, but also the mouth, lungs, and skin. Notably, many viruses infect our cells without inducing any severe symptoms. For example, cytomegalovirus (CMV) is present in approximately half the global population and can reside across all organs.
Today’s genomic sequencing techniques reveal more hidden viruses within saliva, blood, and stool, enabling scientists to approximate the viral load present within the human body by determining viral gene copies. A single gram of stool can contain billions of bacteriophages, and the average gut may harbors hundreds, if not thousands, of unique viruses.
Interestingly, when biologists compare samples from different individuals, they frequently observe considerable differences. This diversity points toward the ability of viruses to evade detection. For example, past research performed by Japanese scientists led to the discovery of a brand-new virus, named anellovirus, from blood samples taken from patients as far back as 1997. Last year, it was uncovered there are over 800 species of this virus, bringing the total number of known viruses to more than 6,800.
Recent explorations of the human virome have also sparked debate on how to define a virus. Classically, viruses are characterized by their protein coat and genetic material, typically composed of double-stranded DNA or single-stranded RNA. But scientists are now noting the existence of minuscule free-floating RNA circles within the human body as well.
The AI-powered detection system being developed by Dr. Pardis Sabeti, computational biologist at the Harvard T.H. Chan School of Public Health, is set to play a significant role in the Human Virome Project. Its primary aim is identifying viral genetic traits, which researchers will then analyze to discern their roles within the human body.
Research has traditionally framed bacteriophages as aggressors, eliminating bacterial hosts to replicate. More recent experiments reveal this relationship is far more nuanced. Colin Hill, microbiologist at the APC Microbiome Ireland research center, commented, "They do not fight to the death, they have a collaborative relationship." Bacteriophages usually do not decimate their bacterial hosts. Rather, the relationship can be mutually beneficial; it could aid the survival of bacteria by helping them discard disadvantageous genes.
Such collaborative interactions between viruses and bacteria may promote human health. Recent studies indicate bacteriophages may play pivotal roles through the defense mechanisms enabling the human body to fend off pathogens on the skin. With the Human Virome Project, scientists hope to shed light on the complexity and often overlooked roles of viruses within human health.