HIV, the causative agent of AIDS, affects over 40 million people globally, and its rapid mutation demands continuous advancement in treatment strategies. At the heart of HIV’s formidable infectious power lies a tiny protective shell known as the capsid, roughly the diameter of 120 nanometers—an almost unfathomable scale that dwarfs even the slenderest human hair. The capsid safeguards the viral RNA genome and critical proteins, orchestrating the virus’s maturation and eventual infiltration into host cells.

Historically, integrase has been recognized for its pivotal role in the late stages of HIV infection, facilitating the insertion of viral DNA into the host genome. However, the new research spearheaded by Perilla’s team radically shifts this understanding. Utilizing state-of-the-art cryo-electron microscopy (cryo-EM), the scientists demonstrated that integrase also acts much earlier during the virus life cycle by performing an architectural role within the capsid itself.

Cryo-EM, a cutting-edge imaging technique that involves flash-freezing samples at temperatures colder than outer space and probing them with electron beams, was instrumental in visualizing the intricate internal structure of HIV particles. The researchers performed these highly delicate studies at the Francis Crick Institute in London, where specialized facilities minimize environmental disturbances, allowing atomic-level resolution of HIV components.

The team discovered that integrase assembles into filamentous structures, effectively “glueing” the inner surface of the capsid. These filaments align with the hexagonal tiles forming the capsid shell, securing the viral RNA genome in a meticulously organized “zipper-like” array. This spatial configuration is essential for the virus’s structural stability and infectious capacity.

Professor Perilla emphasized that this architectural role of integrase is critical: without these filamentous anchors, the virus becomes non-infective. This paradigm shift in understanding integrase’s function opens new avenues for antiviral intervention by targeting the protein’s structural role, not just its well-known enzymatic activities.

To validate the structural and functional integrity of integrase filaments, the research team employed molecular modeling and experimented with ALLINIs (allosteric integrase inhibitors). These inhibitors disrupted the oligomerization process of integrase, thereby interrupting its interaction with the capsid and RNA genome. While some ALLINI compounds already show promise in preclinical studies, none of the existing FDA-approved drugs exploit this newfound structural vulnerability, highlighting a clear therapeutic gap and opportunity.

This multidisciplinary approach — combining high-resolution imaging, computational chemistry, and biochemical experimentation — was only possible through extensive collaboration across renowned institutions. Partners range from the Francis Crick Institute and Dana-Farber Cancer Institute to the University of Oxford and several UK-based research centers, underscoring the global scale of this endeavor.

University of Delaware’s investment in training emerging scientists is important to mention as well. Graduate students like Juan Sebastian Rey play substantial roles in ongoing research, often transitioning into pharmaceutical and biomedical careers, thereby continuing to push forward the frontier of HIV research and treatment development.

The investigators also stress the indispensable role of public funding from agencies like the U.S. National Science Foundation, National Institutes of Health, and Department of Energy in facilitating such high-impact research. According to Professor Perilla, without such support, these scientific breakthroughs would be unattainable.

The implications of this study extend beyond fundamental virology; understanding how integrase structurally organizes the viral genome within the capsid adds a crucial piece to the HIV replication puzzle. This, in turn, enhances the rational design of novel drugs capable of disarming the virus at an earlier stage, potentially preventing establishment of infection and viral spread.

In a field continuously challenged by viral mutation and drug resistance, these findings provide fresh hope for patients and clinicians alike. As HIV persists as a global health threat, advancing from knowledge of integrase’s previously undiscovered capability could herald a new epoch in antiretroviral therapy.

This discovery exemplifies how perseverance, technological innovation, and cooperative research efforts converge to unlock hidden viral mechanisms, pushing the boundaries of science and medicine towards a future where HIV infection may be effectively halted in its tracks.

Subject of Research: HIV structural biology; integrase protein function in viral maturation

Article Title: Previously Unknown Structural Role of HIV Integrase Revealed by High-Resolution Cryo-EM

News Publication Date: February 18, 2026

Web References: https://www.nature.com/articles/s41586-026-10154-x

References: 10.1038/s41586-026-10154-x

Image Credits: Evan Krape and Jeffrey Chase / University of Delaware

Keywords

Human immunodeficiency virus, Acquired immune deficiency syndrome, Sexually transmitted diseases, Public health, Health and medicine, Structural biology, Chemical modeling, Immune disorders

HIV-1 remains a global health crisis, with approximately 40 million people living with the virus worldwide. Despite progress in managing the disease through antiretroviral therapy, challenges such as drug resistance, side effects, and social stigma persist, underscoring the urgent need for new therapeutic strategies. Integrase, long recognized for its function in inserting viral DNA into the infected host’s genome, has now been found to also engage viral RNA at later stages—highlighting previously uncharacterized roles in the HIV lifecycle.

The Salk research team employed cryo-electron microscopy (cryo-EM) to capture integrase in two distinct structural conformations. Initially, integrase operates as part of a massive “intasome” complex, consisting of four identical subunits arranged into a 16-part assembly. This architecture tightly encircles viral DNA, orchestrating its integration into the host genome, a critical step that establishes permanent infection within the host cell.

Later in the replication process, integrase adopts a drastically different form. It transitions from the large intasome to a minimalist four-part complex, a configuration associated with binding to viral RNA inside the HIV capsid. This structural transition from DNA-focused activity to RNA interaction reveals the protein’s adaptability and suggests additional layers of complexity in HIV’s replication machinery.

This discovery marks the first time researchers have visualized integrase’s RNA-bound state, providing a high-resolution blueprint for this elusive form. Such structural insights are invaluable, as the design of targeted inhibitors typically relies on detailed knowledge of a protein’s 3D configuration to effectively disrupt its function without off-target effects.

The implication of integrase functioning beyond DNA integration is profound. While current integrase inhibitors such as Dolutegravir effectively block the protein’s DNA integration role, HIV’s rapid mutation rate often leads to resistance. By targeting integrase’s secondary role in RNA interaction, drug developers may circumvent existing resistance mechanisms, opening the door to new classes of antiretroviral therapies.

Senior author Dmitry Lyumkis, PhD, emphasizes the significance of these findings: “We are only beginning to understand the multifunctionality of integrase proteins. Mapping its interaction with RNA not only enriches our knowledge of viral biology but also informs the rational design of next-generation HIV therapeutics.”

At the molecular level, HIV’s retroviral replication strategy involves reverse-transcribing its RNA genome into DNA, which is then inserted into the host’s genome via integrase. This insertion transforms the host cell into a viral factory, producing progeny RNA that is packaged for new infections. Understanding the full scope of integrase’s roles in this cycle is essential for developing comprehensive antiviral strategies.

The integrase’s structural plasticity uncovered by the Salk team illustrates the dynamic nature of viral proteins. Their data show how subtle shifts in quaternary structure—disassembling from a 16-subunit “lock” to a compact 4-subunit complex—enable integrase to pivot between its DNA and RNA binding functions. Such dynamic assembly-disassembly processes could be exploited pharmacologically to trap the protein in inactive states.

This research represents a collaboration among numerous experts across molecular biology, structural biology, and virology, including significant contributions from partnering institutions such as the University of Colorado School of Medicine, Dana-Farber Cancer Institute, and the National Institute of Diabetes and Digestive and Kidney Diseases. Their collective expertise underscores the complexity and interdisciplinary nature of combatting HIV.

The study also showcases the power of cryo-electron microscopy, which has revolutionized structural biology by enabling the visualization of large and flexible protein complexes in near-native states. The high-resolution cryo-EM maps generated by the researchers provide unparalleled detail into integrase’s architecture, setting a new standard for future investigations of viral proteins.

Beyond its scientific merit, this discovery carries translational potential for public health. Novel integrase inhibitors targeting both DNA and RNA-related functions may reduce drug resistance, improve treatment durability, and mitigate adverse effects. Such advances are critical in the ongoing global effort to curb HIV transmission and improve the quality of life for millions affected by the virus.

As the scientific community digests these findings, follow-up studies are anticipated to confirm integrase’s RNA interaction mechanisms, assess their roles in viral encapsidation and infectivity, and explore the potential for targeting these interactions therapeutically. This evolving picture of integrase’s biology promises to reshape HIV drug development paradigms in the coming years.

The Salk Institute’s pioneering research not only deepens our fundamental understanding of HIV biology but also exemplifies the fusion of structural insights and therapeutic innovation. With new blueprints in hand, drug designers are now better equipped than ever to develop integrase-targeting agents that could transform the clinical management of HIV-1 infection and ultimately help turn the tide against this enduring pandemic.

Subject of Research: Structural and functional analysis of HIV-1 integrase in its dual roles interacting with viral DNA and RNA.

Article Title: Structural Elucidation of HIV-1 Integrase Reveals Dual Functionality in Viral DNA Integration and RNA Interaction

News Publication Date: October 24, 2025

Web References:
https://www.nature.com/articles/s41467-025-64479-8

References:
Lyumkis, D., Jing, T., Shan, Z., et al. (2025). Structural insights into HIV-1 integrase functions during DNA integration and RNA interaction. Nature Communications. DOI: 10.1038/s41467-025-64479-8

Image Credits:
Salk Institute