Researchers have advanced our knowledge of how rotavirus, which is the leading cause of acute gastroenteritis in children, causes illness. This study is among the first to demonstrate that the rotavirus protein NSP4 is essential for various aspects of infection by interfering with calcium signaling both in infected cells and in nearby healthy cells. These disruptions have an impact on the severity of rotavirus disease, shedding light on how NSP4’s role affects the virus’s ability to cause illness. The results imply that targeting NSP4 could open up new avenues for preventing or treating rotavirus infections.
Investigators from Baylor College of Medicine and their partners have enhanced our comprehension of how rotavirus, the foremost cause of acute gastroenteritis in children, triggers illness. The findings published in Science Advances are among the pioneering studies to elucidate that the rotavirus protein NSP4 is critical for several elements of rotavirus infection by altering calcium signaling in both infected and nearby uninfected cells. Such alterations in calcium signaling influence the seriousness of rotavirus disease, offering fresh perspectives on how the function of NSP4 impacts the severity of the virus. These discoveries suggest that modifying NSP4 may lead to innovative methods for preventing or managing rotavirus infections.
“Rotavirus is responsible for roughly 25% of severe cases of pediatric acute gastroenteritis, which usually manifests as watery diarrhea, vomiting, fever, and abdominal cramps. Alarmingly, nearly 500,000 children globally succumb to this condition every year,” explained Dr. Joseph Hyser, the lead author, who is an associate professor in molecular virology and microbiology and a member of the Alkek Center for Metagenomic and Microbiome Research at Baylor. “Although oral rehydration therapy and live-attenuated rotavirus vaccines have made a significant impact in lowering the incidence of rotavirus acute gastroenteritis in children around the world, we still see potential for advancement.”
In this latest study, Hyser and his team delved deeper into how NSP4’s functions during rotavirus infection relate to disease severity, aiming to discover a new strategy for treatment or prevention. In their previous research, they found that rotavirus induces abnormal calcium signals called ‘intercellular calcium waves’ that spread from infected cells to nearby uninfected cells and that blocking these signals reduced the severity of the disease.
“The outcomes suggested that these calcium waves probably play a role in enhancing rotavirus replication and virulence; however, the exact mechanism behind how the virus instigates this signal was unclear,” Hyser admitted. “We already had indications that positioned NSP4 at the forefront of the viral proteins likely responsible for inducing calcium waves.”
Using both human and porcine virulent and attenuated rotavirus strains, along with new genetic recombinant strains created through reverse genetics, the team studied the role of NSP4 in inducing calcium waves and its association with disease severity across various experimental models, including lab-grown cells, intestinal organoid cultures, and animal testing.
The researchers concluded that the capacity of rotavirus to create calcium waves is fully linked to NSP4, such that merely expressing NSP4 in cells, even without rotavirus infection, resulted in calcium waves that closely resembled a natural infection.
Notably, NSP4 from attenuated strains of rotavirus, which typically produce milder symptoms or none at all, was responsible for fewer calcium waves compared to that from virulent strains. Additionally, incorporating the attenuated NSP4 into a virulent strain reduced both the number of calcium waves produced and its capacity to induce diarrhea in an animal model.
“Our findings indicated that the rotavirus’s ability to produce calcium waves is closely associated with NSP4; simply expressing NSP4 is enough to trigger calcium waves, and various facets of rotavirus disease severity are linked to the capacity to generate these waves,” stated Hyser.
Moreover, these calcium waves also initiated an immune response, suggesting that calcium dysregulation could play a role in how the virus is recognized by the host.
“All the evidence indicates that NSP4 appears to be involved in creating calcium waves that are related to both the severity of rotavirus disease and host cell responses to this abnormal calcium signaling,” Hyser added.
These findings might also be relevant to other viruses that possess proteins similar to NSP4, which could disrupt calcium signaling as well.
Additional contributors to this research 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, all affiliated with Baylor College of Medicine, Indiana University, or Stanford University School of Medicine.
The research received funding from several National Institutes of Health grants (NICH R01AI158683, R01DK115507, NIH S10OD028480, NIH F30DK131828, NIH F31DK132942, NIH F32DK130288 and NIH T32DK007664) and the McNair Foundation M.D./Ph.D. Scholars Program.
