A new study reveals a previously unknown mechanism that governs whether viruses that infect bacteria will quickly kill their hosts or remain latent inside the cell. The discovery, reported in the journal eLife, also may apply to viruses that infect humans and other animals, the researcher said.
"I found for the first time that the mechanics of how DNA is packaged inside a virus determine the course of infection," said University of Illinois pathobiology professor Alex Evilevitch, who conducted the study.
After injecting their DNA into a cell, viruses tend to follow one of two major pathways, called "lytic" or "latent" infections. In the lytic pathway, viral DNA quickly commandeers the host cell's own resources to make hundreds of copies of itself. The new viruses then kill the cell and go on to repeat the cycle in other cells.
Latent viral infections follow a different course, however: Once inside the cell, the viral DNA incorporates itself into the host genome. When the cell divides, the viral DNA also gets duplicated. As long as the infection remains latent, there is little evidence of it in the host.
The problem with latent viral infections is that, in times of stress for the host, the virus can suddenly turn lytic, taking over the cell and killing it after a mad bout of reproduction, Evilevitch said.
"The many viral infections that we carry can remain latent for a very long time. Sometimes they go lytic, and that's when we develop symptoms," he said.
Latent viral infections in humans include herpes simplex, varicella zoster, Epstein-Barr, human cytomegalovirus, adenovirus, Kaposi's sarcoma and several others.
"It's very important to know what regulates the switch from the latent state to the lytic state, so that we can perhaps stop these infections from spreading," Evilevitch said.
Many studies of the dynamics of viral infection have focused on the structural characteristics of the protein capsids that protect the viral genetic material and shuttle it to the site of infection. Evilevitch looked instead at the stresses and strains on the viral DNA molecules just before they are injected into a host.
He used isothermal titration calorimetry, which can measure discrete changes in thermal energy in a system, to track the course of infection. In a previous study, his laboratory group discovered that the process of viral infection gives off heat. In the new study, Evilevitch exposed the host bacterium, Escherichia coli, to thousands of viral particles, then monitored the thermal ups and downs that occurred as infection progressed.
He found that the infections occurred either synchronously - with hundreds of viruses injecting their DNA into the bacterium at once - or randomly, with infections occurring more slowly in an uncoordinated fashion. A closer look at the viral genetic material prior to infection revealed that the DNA packaged inside the virus tended to be more "liquid-like" in the synchronous infections but stiffer during the random infections.
The synchronous infections corresponded closely with latent infections that preserved the host, while the slower, more random process of infection led to lytic events that killed the host.
As temperature increased, the viral DNA became more like liquid and infections were more likely to be synchronous. Increases in extracellular magnesium ion concentrations related to cellular metabolism and growth conditions also promoted synchronous infections, Evilevitch found.
Heat made the DNA molecules inside the capsid more flexible, reducing the sliding friction between them, he said. Adding positively charged ions reduced the repulsion between the negatively charged DNA molecules, also making the DNA more fluid.
"The DNA becomes more flexible; it has more of a fluid character," he said. "As a result, it's more likely to be ejected - like toothpaste out of a tube. But if it's solid, it's going to get stuck inside the tube."
The new findings are "good for virology," Evilevitch said.
"We now understand that the mechanics of DNA packaged inside the virus directly influences the direction of infection toward a lytic or latent pathway," he said. "We think this will help us learn how to control infections and prevent them from becoming lytic. It can potentially lead to new therapies to prevent the spread of infection."
The National Science Foundation and the Swedish Research Council supported this work.
Source: University of Illinois at Champaign-Urbana
Stay prepared and protected with Infection Control Today's newsletter, delivering essential updates, best practices, and expert insights for infection preventionists.
Reducing Hidden Risks: Why Sharps Injuries Still Go Unreported
July 18th 2025Despite being a well-known occupational hazard, sharps injuries continue to occur in health care facilities and are often underreported, underestimated, and inadequately addressed. A recent interview with sharps safety advocate Amanda Heitman, BSN, RN, CNOR, a perioperative educational consultant, reveals why change is overdue and what new tools and guidance can help.
New Study Explores Oral Vancomycin to Prevent C difficile Recurrence, But Questions Remain
July 17th 2025A new clinical trial explores the use of low-dose oral vancomycin to prevent Clostridioides difficile recurrence in high-risk patients taking antibiotics. While the data suggest a possible benefit, the findings stop short of statistical significance and raise red flags about vancomycin-resistant Enterococcus (VRE), underscoring the delicate balance between prevention and antimicrobial stewardship.
What Lies Beneath: Why Borescopes Are Essential for Verifying Surgical Instrument Cleanliness
July 16th 2025Despite their smooth, polished exteriors, surgical instruments often harbor dangerous contaminants deep inside their lumens. At the HSPA25 and APIC25 conferences, Cori L. Ofstead, MSPH, and her colleagues revealed why borescopes are an indispensable tool for sterile processing teams, offering the only reliable way to verify internal cleanliness and improve sterile processing effectiveness to prevent patient harm.
The Next Frontier in Infection Control: AI-Driven Operating Rooms
Published: July 15th 2025 | Updated: July 15th 2025Discover how AI-powered sensors, smart surveillance, and advanced analytics are revolutionizing infection prevention in the OR. Herman DeBoard, PhD, discusses how these technologies safeguard sterile fields, reduce SSIs, and help hospitals balance operational efficiency with patient safety.
Targeting Uncertainty: Why Pregnancy May Be the Best Time to Build Vaccine Confidence
July 15th 2025New national survey data reveal high uncertainty among pregnant individuals—especially first-time parents—about vaccinating their future children, underscoring the value of proactive engagement to strengthen infection prevention.
Reducing Hidden Risks: Why Sharps Injuries Still Go Unreported
July 18th 2025Despite being a well-known occupational hazard, sharps injuries continue to occur in health care facilities and are often underreported, underestimated, and inadequately addressed. A recent interview with sharps safety advocate Amanda Heitman, BSN, RN, CNOR, a perioperative educational consultant, reveals why change is overdue and what new tools and guidance can help.
New Study Explores Oral Vancomycin to Prevent C difficile Recurrence, But Questions Remain
July 17th 2025A new clinical trial explores the use of low-dose oral vancomycin to prevent Clostridioides difficile recurrence in high-risk patients taking antibiotics. While the data suggest a possible benefit, the findings stop short of statistical significance and raise red flags about vancomycin-resistant Enterococcus (VRE), underscoring the delicate balance between prevention and antimicrobial stewardship.
What Lies Beneath: Why Borescopes Are Essential for Verifying Surgical Instrument Cleanliness
July 16th 2025Despite their smooth, polished exteriors, surgical instruments often harbor dangerous contaminants deep inside their lumens. At the HSPA25 and APIC25 conferences, Cori L. Ofstead, MSPH, and her colleagues revealed why borescopes are an indispensable tool for sterile processing teams, offering the only reliable way to verify internal cleanliness and improve sterile processing effectiveness to prevent patient harm.
The Next Frontier in Infection Control: AI-Driven Operating Rooms
Published: July 15th 2025 | Updated: July 15th 2025Discover how AI-powered sensors, smart surveillance, and advanced analytics are revolutionizing infection prevention in the OR. Herman DeBoard, PhD, discusses how these technologies safeguard sterile fields, reduce SSIs, and help hospitals balance operational efficiency with patient safety.
Targeting Uncertainty: Why Pregnancy May Be the Best Time to Build Vaccine Confidence
July 15th 2025New national survey data reveal high uncertainty among pregnant individuals—especially first-time parents—about vaccinating their future children, underscoring the value of proactive engagement to strengthen infection prevention.
2 Commerce Drive
Cranbury, NJ 08512