A group of researchers from the Gladstone Institutes (GladInst), UC San Francisco (UniCalSF), and UC Berkeley (UC Berkeley) used a systematic approach to get an entirely new look at the way tuberculosis (lat. Phthisis) infects people. Their study uncovered interactions between tuberculosis and human proteins that could provide new approaches to combat infection. Tuberculosis is one of the top 10 causes of death worldwide. Nearly 2 million people die every year from this infectious disease, and an estimated 2 billion people are chronically infected. The only vaccine, developed almost 100 years ago, offers limited protection and patients are becoming increasingly resistant to available drugs. Despite this significant impact on humankind, very little is known about how tuberculosis develops and spreads in the body.

According to Nevan J. Krogan, Ph.D., a senior investigator at the Gladstone Institutes and director of the Quantitative Biosciences Institute at UCSF, with a better understanding of the mechanisms used by tuberculosis to disrupt immune response, scientists could eventually optimize vaccine strategies, as well as explore therapies to supplement antibiotics. Nevan J. Krogan, along with his colleague Jeffery S. Cox, Ph.D., from UC Berkeley, employed a mass spectrometry-based approach to identify interactions between tuberculosis proteins and human proteins. It’s the first time this approach has been applied to tuberculosis. Essentially, this technology works by placing a hook on the tuberculosis proteins. When scientists fish them out of the human cells, the human proteins to which they’re attached come with them, so they can see what they interact with.

Using this method, the team of scientists targeted 34 tuberculosis proteins, very few of which had been studied before. They found 187 interactions between these tuberculosis proteins and human proteins. Each one of those connections could ultimately represent a drug target - a new way to fight tuberculosis. One Connection Responds to Both Bacterial and Viral Infections. After their initial discovery, scientists focused their attention on one specific connection. They studied the physical interaction between the human protein CBL and a tuberculosis protein called LpqN.

They showed that when they remove the LpqN protein, tuberculosis can’t infect human cells as well. However, when the CBL protein is also deleted, the tuberculosis infection can resume its regular growth. This suggests that CBL is involved in limiting bacterial infections. Scientists discovered that when CBL is removed, cells also become more resistant to infections by viruses, such as herpes. They believe that CBL acts as a switch to toggle between anti-bacterial and anti-viral responses in the cell. That’s why it’s important to study the interactions between proteins in an unbiased way.

By studying how proteins interact and work together, scientists can begin to map proteins onto pathways and find unexpected connections. They can then compare the protein interactions across many pathogens and identify similarities. To this end, scientists recently founded the Host–Pathogen Map Initiative with investigators from Gladstone, UCSF, UC Berkeley, and UC San Diego. Through this initiative, they will comprehensively map the gene and protein networks underlying infectious disease and develop technologies to lead to novel and targeted therapies.

The scientists also helped launch the BioFulcrum Viral and Infectious Disease Research Program at Gladstone in 2017. The goal of this program is to develop host-directed therapies. The scientists have already identified commonly hijacked pathways in human cells. The human genes hijacked by tuberculosis, for instance, are the same genes mutated in many other disease states, including cancer and autism. The research was supported by the National Institutes of Health.