Researchers at Baylor College of Medicine and collaborating institutions have improved our understanding of how rotavirus, the most common cause of acute gastroenteritis in children, makes people sick. The study published in Scientific advances is among the first to demonstrate that the rotavirus protein NSP4 is necessary and sufficient for multiple aspects of rotavirus infection by altering calcium signaling not only within infected cells but also in nearby uninfected cells. These alterations in calcium signaling affect the severity of rotavirus disease, providing new insights into how NSP4 function influences rotavirus virulence. The findings suggest that manipulation of NSP4 could lead to new strategies to prevent or treat rotavirus infections.
“Rotavirus alone accounts for a quarter of all cases of severe pediatric acute gastroenteritis, which typically presents with watery diarrhea, vomiting, fever and abdominal pain. Currently, nearly 500,000 children worldwide die from this condition every year,” said corresponding author Dr. Joseph Hyser, associate professor of molecular virology and microbiology, as well as part of the Alkek Center for Metagenomics and Microbiome Research and a member of the Cancer Center Comprehensive Dan L Duncan at Baylor. “Although oral rehydration therapy and live attenuated rotavirus vaccines have helped reduce the burden of acute rotavirus gastroenteritis in children worldwide, there is still room for improvement.”
In the current study, Hyser and colleagues delved into how NSP4 functions during rotavirus infection contribute to disease severity in hopes of finding a novel approach to treating or preventing the disease. In a previous study, researchers found that rotavirus triggers aberrant calcium signals known as “intercellular calcium waves” that radiate from infected cells to neighboring uninfected cells and that inhibition of these signals reduced the severity of the disease. .
“The results indicated that calcium waves were likely to contribute to rotavirus replication and virulence; however, it was unclear how the virus triggered this signal,” Hyser said. “We already had evidence that placed NSP4 at the top of the list of viral proteins that could be involved in triggering calcium waves.”
Working with existing attenuated and virulent human and porcine rotavirus strains, as well as new recombinant genetic strains generated by a reverse genetics system, the team examined the role of NSP4 in the induction of calcium waves and its connection to the severity of the disease. disease using a variety of experimental methods. models, including laboratory-grown cells, intestinal organoid cultures, and animal models.
The researchers found that the ability of rotavirus to generate calcium waves was entirely attributable to NSP4, such that expression of NSP4 in cells, even in the absence of rotavirus infection, generated calcium waves indistinguishable from a native infection.
Importantly, NSP4 from attenuated rotaviruses, which cause milder disease or no disease, induced fewer calcium waves than NSP4 from virulent strains, and insertion of attenuated NSP4 into a virulent rotavirus strain decreased the number of calcium waves that produced and decreased its ability to cause diarrhea in an animal model.
“We found that the ability of rotavirus to generate calcium waves goes hand in hand with NSP4, NSP4 expression alone is sufficient to generate calcium waves, and multiple aspects of rotavirus disease severity correlate with the ability to generate calcium waves. to generate calcium waves,” Hyser said.
Furthermore, the calcium waves also triggered an immune response, which involved the deregulation of calcium as a means of viral recognition.
“Taken together, the evidence suggested that NSP4 appeared to be involved in the induction of calcium waves related to both rotavirus disease severity and host cell responses to this aberrant level of calcium signaling,” Hyser said.
The findings may apply beyond rotavirus to other viruses that carry NSP4-like proteins that could be involved in altering calcium signaling.
Other contributors to this work include J. Thomas Gebert, Francesca J. Scribano, Kristen A. Engevik, Ethan M. Huleatt, Michael R. Eledge, Lauren E. Dorn, Asha A. Philip, Takahiro Kawagishi, Harry B. Greenberg, and John T. Patton. The authors are affiliated with one or more of the following institutions: Baylor College of Medicine, Indiana University, and Stanford University School of Medicine.
The study was supported by grants from the National Institutes of Health (NICH R01AI158683, R01DK115507, NIH S10OD028480, NIH F30DK131828, NIH F31DK132942, NIH F32DK130288, and NIH T32DK007664) and the McNair Foundation Ph.D. Medicine/Ph.D. Scholarship program.