Crimean–Congo hemorrhagic fever virus, or CCHFV, belongs to the order Bunyavirales and is transmitted primarily by infected ticks, especially ticks of the genus Hyalomma. People can also become infected through contact with the blood or tissues of viremic animals, and human-to-human transmission can occur when bodily fluids from an infected person reach another individual. Clinical outcomes vary widely. Some infections cause mild or nonspecific illness, while severe disease can progress rapidly, with bleeding, circulatory collapse, liver dysfunction and multiorgan failure. The virus’s broad geographic distribution and ability to move between wildlife, livestock, ticks and people make it a persistent public-health concern.

The viral surface is dominated by a glycoprotein complex that helps CCHFV enter host cells and is exposed to the immune system. Like many enveloped viruses, CCHFV produces proteins that must perform several tasks at once: assemble into new viral particles, interact with host-cell membranes and evade or withstand immune attack. GP38 is produced from the virus’s glycoprotein precursor and is distinct from the better-known entry proteins that form the mature viral surface machinery. That distinction matters because immune responses directed against one part of a viral protein complex may not recognize another part, and because some viral proteins can be conserved across strains even when exposed regions change.

The paper by Wang, Monticelli, Berrigan and colleagues focuses on GP38 from the M18-China isolate and reports that this protein “confers broad immunological breadth.” In practical terms, the study’s title indicates that GP38 can generate or support immune recognition extending across a wide range of viral antigenic features or virus variants. The supplied publication information does not provide the study’s experimental sample sizes, animal models, antibody sequences, structural data or neutralization measurements, so those details cannot be used to quantify the effect. What can be concluded from the reported finding is that the investigators have identified an immune-relevant property in a protein that has received less attention than the virus’s principal entry glycoproteins.

That result is important because viral evolution can undermine highly narrow immune defenses. Antibodies often recognize three-dimensional shapes on the surface of proteins, known as epitopes. If mutations alter those shapes, an antibody may bind less effectively or fail to bind altogether. A target with broader conservation, or one that presents multiple shared epitopes, may offer a better foundation for countermeasures intended to work against genetically diverse viral lineages. Broad recognition does not automatically mean broad protection: an antibody can bind to a protein without blocking infection, and an immune response can be detectable without being strong enough to prevent disease. The crucial next question is therefore whether GP38-directed responses interfere with viral replication, reduce disease severity or improve survival in appropriate experimental systems.

The discovery also has potential significance for diagnostics. Many tests for viral disease detect either the virus’s genetic material or antibodies produced by an infected person. Molecular tests can be highly specific but may require specialized equipment and must be performed while viral RNA is still present at detectable levels. Serological tests, by contrast, can reveal prior exposure through antibodies against viral proteins, but their performance depends on the selected antigen. A protein that is recognized across diverse CCHFV isolates could help researchers develop assays less vulnerable to strain-specific differences. At the same time, broad binding can create a technical challenge: a diagnostic antigen must distinguish genuine CCHFV exposure from cross-reactive responses to related viruses. GP38’s value for testing will therefore depend on how specifically it is recognized and how consistently it performs in samples from people with confirmed infection.

For vaccine research, the appeal of GP38 lies in the possibility of adding a new component to an immune-targeting strategy. Most vaccine development against enveloped viruses emphasizes surface proteins involved directly in entry because antibodies that block those proteins can prevent infection at the earliest stage. Yet a successful vaccine may need to stimulate several layers of immunity, including antibodies against multiple viral proteins and T cells that identify infected cells. Incorporating an antigen such as GP38 could broaden the range of immune responses generated by vaccination, particularly if the protein contains conserved regions shared among viral lineages. Whether it can do so safely and effectively remains an open question. Researchers would need to establish the protein’s structure, its accessibility during natural infection, the quality of the antibodies it induces and its performance when combined with other CCHFV antigens.

The study may also encourage a closer look at how CCHFV’s accessory and structural proteins interact with the immune system. Viral proteins that are not the dominant entry factors are sometimes overlooked because they do not present an obvious target for neutralizing antibodies. However, they may still contain conserved molecular surfaces, influence how viral particles are assembled or shape the immune response in ways that affect disease. Understanding GP38 could therefore contribute to a more complete map of the virus rather than simply producing a single candidate antigen. Such basic knowledge is valuable for a pathogen whose biology remains less thoroughly characterized than that of viruses such as influenza, HIV or SARS-CoV-2.

Important hurdles remain before the reported property can translate into a medical countermeasure. CCHFV research requires high-containment facilities because the virus can cause severe human disease and can spread through contact with infectious material. That limits the number of laboratories able to perform live-virus experiments and slows the progression from molecular observation to preclinical validation. Researchers must also account for the virus’s genetic diversity, differences in immune responses among individuals and the difficulty of conducting clinical trials for a sporadic disease that appears in geographically scattered outbreaks. The M18-China isolate provides a valuable reference point, but a broadly useful intervention would need to be tested against additional isolates and evaluated in systems that reflect the complexity of human infection.

For now, the central message is one of opportunity rather than immediate clinical impact. GP38 from the M18-China isolate has been reported as a protein with broad immunological relevance, expanding the list of CCHFV components that may be useful for understanding immunity and designing countermeasures. The finding could help shift attention toward a more inclusive view of viral antigens, in which less prominent proteins complement the major entry machinery. Further work will determine whether GP38-directed immunity merely recognizes the virus or can actually control it. If subsequent studies demonstrate cross-strain protection, reliable diagnostic performance or therapeutic antibody activity, this small viral protein could become an important piece of the global effort to prepare for Crimean–Congo hemorrhagic fever.

CCHFV belongs to the family Nairoviridae and carries its genetic information as a segmented, negative-sense RNA genome. The virus is primarily associated with Hyalomma ticks, which can acquire it while feeding on infected animals and later transmit it to other hosts. Humans may become infected through tick bites or contact with the blood and tissues of infected animals, including during slaughtering, veterinary procedures, or animal handling. Although many infections are mild or clinically unapparent, severe disease can develop rapidly, producing fever, vascular injury, bleeding, organ dysfunction, and, in some cases, death. This broad clinical spectrum makes early laboratory confirmation essential, yet it also complicates recognition in the field.

The sheep model examined by Gutjahr, Michaely, Bost and their collaborators addresses a central question in viral pathogenesis: where does CCHFV go after entering the body, and how does the timing of viral presence in different tissues affect the ability to detect it? Viral dissemination is not simply a matter of measuring whether an animal is infected. It involves tracking the movement of virus or viral genetic material through blood, organs, and potentially tissues that may be relevant to transmission or diagnosis. Such mapping can reveal which biological compartments become infected first, how long the virus remains detectable, and whether different samples provide different windows for reliable testing.

For diagnostic science, these details are crucial. Molecular assays such as reverse-transcription polymerase chain reaction detect viral RNA, usually by converting the RNA into complementary DNA and amplifying selected genomic sequences. The method can be highly sensitive, but its performance depends on the quality and timing of the sample. Viral RNA may be abundant in blood during one phase of infection and more readily detected in organs or other tissues at another. A negative result from one specimen therefore does not always exclude infection, particularly when sampling occurs early, late, or after viral levels have changed. By examining infection in sheep under controlled conditions, the study can help define which specimens are most informative and when they should be collected.

The work also speaks to the difference between detecting a virus and understanding its biological activity. Viral RNA can persist after infectious virus has declined, while infectious particles may be present at levels that are difficult to measure directly. Conversely, a low concentration of RNA in blood may still indicate an active infection or a risk of transmission through contaminated material. Experimental infection studies can compare molecular detection with tissue distribution and pathological observations, helping researchers interpret test results in the context of disease progression. That distinction is particularly important for CCHFV, where laboratory safety requirements are stringent and opportunities to study naturally infected animals are limited.

Sheep are a valuable model in this area because they are relevant to the ecology of CCHFV and may encounter infected ticks in regions where the virus circulates. Livestock can become infected without displaying obvious signs, yet they may develop transient viraemia—the presence of virus in the bloodstream—that enables ticks to acquire the pathogen during feeding. Understanding this period is important not only for animal health but also for estimating the risk posed to farmers, veterinarians, slaughterhouse workers, and others who handle animals or animal products. A controlled sheep study can isolate variables that are difficult to separate during field investigations, including the timing of infection, the amount of virus administered, and the relationship between clinical signs and laboratory findings.

The diagnostic implications extend beyond animal surveillance. Human CCHFV cases are often identified using a combination of clinical history, exposure information, molecular testing, and, later in the infection, serology. Antibody-based tests detect the host immune response rather than the virus itself and may become informative only after antibodies have developed. Molecular testing is therefore particularly important during the acute phase, when rapid decisions about patient isolation, contact tracing, and clinical management are required. Insights from animal tissue distribution may support more rational sampling strategies and help laboratories understand why test sensitivity can vary over the course of infection. They may also aid the evaluation of new assays designed to detect conserved regions of the viral genome.

The study has significance for a One Health approach, which treats human, animal, and environmental health as connected rather than separate domains. CCHFV transmission is shaped by climate, tick abundance, livestock movement, land use, occupational exposure, and access to diagnostic services. As tick habitats expand or shift, surveillance systems may need to monitor both animals and people across wider geographical areas. Research that clarifies how infection unfolds in a relevant livestock host can contribute to preparedness by improving protocols for sample collection, biosafety, veterinary monitoring, and outbreak investigation. It may also provide a framework for comparing viral strains or host responses in future experiments, although such comparisons require careful attention to differences in virus, host, and experimental design.

The findings presented in npj Viruses are therefore positioned at the intersection of pathogenesis and public-health readiness. By focusing on viral dissemination in experimentally infected sheep, Gutjahr and colleagues address the biological processes that determine what can be detected, where it can be detected, and when testing is most likely to succeed. The research does not eliminate the challenges posed by CCHFV’s high-consequence nature, but it strengthens the evidence base needed to confront them. Better knowledge of tissue distribution and diagnostic timing can support earlier recognition of infection, more effective surveillance of livestock and exposed workers, and a clearer understanding of how a tick-borne virus moves between animals and humans.

Subject of Research: Viral dissemination and diagnostic insights from experimental infection of sheep with Crimean-Congo hemorrhagic fever virus

Article Title: Viral dissemination and diagnostic insights from experimental infection of sheep with Crimean-Congo hemorrhagic fever virus

Article References: Gutjahr, B., Michaely, L.M., Bost, C. et al. Viral dissemination and diagnostic insights from experimental infection of sheep with Crimean-Congo hemorrhagic fever virus. npj Viruses 4, 39 (2026). https://doi.org/10.1038/s44298-026-00228-y

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s44298-026-00228-y

Keywords: Crimean-Congo hemorrhagic fever virus, CCHFV, viral dissemination, sheep, experimental infection, diagnostic testing, zoonotic disease, tick-borne virus, One Health, veterinary virology

Historically endemic to regions including Africa, the Balkans, the Middle East, and much of Asia, CCHFV has recently demonstrated a marked capacity for geographic expansion. One of the principal contributing factors to this trend is the virus’s transmission through ticks, specifically Hyalomma species, which are carried by migratory birds. This mode of dissemination allows the virus to infiltrate new territories, notably Western Europe, thereby elevating the risk of outbreaks in previously unaffected populations. The increasing range of the virus highlights the dynamic interplay between ecological factors and pathogen propagation.

At the forefront of combating this expanding threat is Professor Scott Pegan from the University of California, Riverside School of Medicine. Awarded a substantial grant from the National Institutes of Health totaling approximately $3.4 million over five years, Pegan is spearheading an international, multi-institutional consortium dedicated to the identification and development of broadly protective antibodies against CCHFV. This initiative is poised to make critical strides towards therapeutic interventions in a pathogen realm currently devoid of effective options.

The viral agent is deemed a priority pathogen not only by American institutions but also by the World Health Organization. CCHFV functions as the prototypical virus within the nairovirus genus, a taxonomic grouping that also encompasses other emergent nairoviruses such as Benji, Songling, Wetland, Yezo, and the Pacific Coast tick nairovirus. Each of these viruses poses distinct yet interconnected challenges, making the CCHFV a pivotal focus for understanding nairoviral pathogenesis and immune evasion mechanisms.

Pegan emphasized the urgency created by the virus’s rapid dissemination and severe clinical outcomes: “This project is designed to identify broadly protective antibody candidates that can be developed into therapies to combat CCHFV infections.” This statement underscores the interdisciplinary essence of the research, aimed at unraveling the complexities of host immune responses and exploiting them therapeutically. The project’s ambitious goals extend beyond treatment to inform foundational knowledge about immune targeting of viral epitopes.

The investigative team comprises experienced virologists and immunologists across multiple esteemed institutions, including co-principal investigator Dr. Mohammad Sajadi of the University of Maryland School of Medicine. The involvement of researchers from the U.S. Army Medical Research Institute of Infectious Diseases (USAMRIID), such as Aura Garrison and Joseph Golden, brings decades of expertise in hemorrhagic fever virus research. This collaborative structure facilitates a convergence of cutting-edge technical skill sets in molecular virology, immunology, and translational therapeutics.

A key component of their work involves analyzing immune profiles of CCHFV survivors originating from endemic settings in Kazakhstan, Turkey, and Uganda. These regions represent distinct viral genetic lineages and epidemiological contexts, lending the research a broad relevance. By isolating and characterizing neutralizing antibodies from convalescent individuals, the team aims to identify monoclonal antibodies capable of cross-neutralizing diverse CCHFV strains. Such therapeutic monoclonals mimic the immune system’s natural viral defense mechanisms, offering promise as both prophylactic and post-exposure countermeasures.

Technically, the project involves advanced methodologies such as epitope mapping to pinpoint immunodominant regions of viral proteins that elicit potent antibody responses. These epitopes serve as molecular targets to engineer monoclonal antibodies with enhanced binding affinity and breadth. The approach also incorporates structural virology techniques, including cryo-electron microscopy and X-ray crystallography, to elucidate the three-dimensional conformation of viral glycoproteins involved in host cell entry and immune recognition.

Understanding how the immune system counteracts CCHFV is crucial not only for therapy but also for vaccine design, which remains elusive given the virus’s antigenic diversity and complex replication cycle. By targeting non-traditional viral proteins that have historically received less attention, the research has the potential to reveal vulnerable “Achilles’ heels” within the viral arsenal. These novel insights could revolutionize the development of broadly protective interventions against CCHFV and related nairoviruses.

Beyond basic scientific exploration, the project embodies a multidisciplinary and international effort encompassing institutions such as the Centers for Disease Control and Prevention, Rocky Mountain Laboratories, the Uganda Virus Research Institute, Hitit University in Turkey, and the South Kazakhstan Medical Academy. This global partnership reflects the recognition that CCHFV’s threat surpasses borders and requires concerted, cross-sectoral responses integrating epidemiology, clinical science, and biodefense.

Pegan’s vision articulates a strategic framework for tackling not only the current CCHFV threat but also impending nairovirus outbreaks that may emerge due to ecological change and increasing human-wildlife interface. “By utilizing a non-traditional targeting strategy,” Pegan noted, “the project could lead to novel, potentially life-saving therapeutics and establish a valuable paradigm for future viral hemorrhagic fever research.” This emphasis on innovation and preparedness resonates deeply in an age increasingly cognizant of viral pandemic risks.

The epidemiological complexities of CCHFV also bear relevance to its zoonotic and vector-borne characteristics; the virus perpetuates in nature through a tick-vertebrate-tick transmission cycle involving various wild and domestic animals. These animal reservoirs sustain viral endemicity and facilitate spillover events into human populations. The amplification of infected tick vectors, their adaptation to new environments, and anthropogenic factors such as land use change collectively drive the observed expansion of CCHFV’s geographic footprint.

From a molecular standpoint, CCHFV is an enveloped negative-sense single-stranded RNA virus with a segmented genome. The virus encodes several structural and non-structural proteins integral to its replication and pathogenicity. Particularly, the viral glycoprotein precursor undergoes cleavage to form mature glycoproteins that mediate host receptor engagement, membrane fusion, and immune evasion. These proteins are prime targets for neutralizing antibodies and represent focal points of the ongoing therapeutic antibody discovery efforts.

In light of the looming threat posed by CCHFV and the lack of effective countermeasures, the advent of this comprehensive research initiative marks a critical juncture. The integration of advanced immunological tools, structural biology, and field epidemiology promises to expedite therapeutic development. This endeavor not only addresses an urgent public health need but also contributes to the broader scientific pursuit of combating viral hemorrhagic fevers, which continue to challenge global health security.

Subject of Research: Development of broadly protective monoclonal antibodies against Crimean-Congo hemorrhagic fever virus (CCHFV) and understanding immune responses to the virus in endemic populations.

Article Title: International Effort Accelerates Development of Therapeutic Antibodies to Combat Expanding Threat of Crimean-Congo Hemorrhagic Fever Virus

News Publication Date: Not specified in the source content

Web References:
– https://www.who.int/news-room/fact-sheets/detail/crimean-congo-haemorrhagic-fever
– https://profiles.ucr.edu/app/home/profile/scottp
– https://medschool.ucr.edu/
– http://www.ucr.edu/

References: National Institutes of Health grant announcement (details within the article content); original research outlined by Prof. Scott Pegan and team; institutional information from University of California, Riverside and partnering agencies.

Keywords: Crimean-Congo hemorrhagic fever virus, CCHFV, nairovirus, monoclonal antibodies, viral hemorrhagic fever, emerging infectious diseases, antibody therapeutics, biosafety level 4 pathogen, vector-borne virus, tick-borne diseases, viral immunology, NIH research grant.