Vesicular Stomatitis Virus Chimeras Expressing the Oropouche Virus Glycoproteins Elicit Protective Immune Responses in Mice

A Comprehensive Review of the Neglected and Emerging Oropouche Virus

Oropouche virus (OROV) is a neglected and emerging arbovirus that infects humans and animals in South and Central America. OROV is primarily transmitted to humans through the bites of infected midges and possibly some mosquitoes. It is the causative agent of Oropouche fever, which has high morbidity but low mortality rates in humans. The disease manifests in humans as high fever, headache, myalgia, arthralgia, photophobia, and, in some cases, meningitis and encephalitis. Additionally, a recent report suggests that OROV may cause fetal death, miscarriage, and microcephaly in newborns when women are infected during pregnancy, similar to the issues caused by the Zika virus (ZIKV), another mosquito-borne disease in the same regions. OROV was first reported in the mid-20th century in the Amazon basin. Since then, over 30 epidemics and more than 500,000 infection cases have been reported. The actual case numbers may be much higher due to frequent misdiagnosis, as OROV infection presents similar clinical symptoms to other co-circulating viruses, such as dengue virus (DENV), chikungunya virus (CHIKV), ZIKV, and West Nile virus (WNV). Due to climate change, increased travel, and urbanization, OROV infections have occurred at an increasing pace and have spread to new regions, with the potential to reach North America. According to the World Health Organization (WHO), over 10,000 cases were reported in 2024, including in areas where it was not previously detected. There is an urgent need to develop vaccines, antivirals, and specific diagnostic tools for OROV diseases. However, little is known about this surging virus, and no specific treatments or vaccines are available. In this article, we review the most recent progress in understanding virology, transmission, pathogenesis, diagnosis, host-vector dynamics, and antiviral vaccine development for OROV, and provide implications for future research directions.

Potential therapeutics and vaccines: Current progress and challenges in developing antiviral treatments or vaccines for Oropouche virus

Oropouche virus (OROV), an emerging arbovirus, poses a significant public health challenge in tropical and subtropical regions, with no licensed vaccines or antiviral therapies currently available. This review explores recent advancements in therapeutic strategies and vaccine development for OROV, focusing on molecular mechanisms of viral replication, identification of potential antiviral targets, and the role of immunotherapy in managing infections. Promising antiviral candidates, including ribavirin, mycophenolic acid, and interferon, have demonstrated efficacy in in vitro studies, offering a foundation for further investigation. The challenges of preclinical and clinical development, such as high mutation rates, immune response variability, and vaccine delivery hurdles, are critically analyzed. By addressing the progress and remaining gaps, this article aims to provide a comprehensive overview to inform future research and facilitate the development of effective antiviral strategies and vaccines for OROV.

A computational approach for MHC-restricted multi-epitope vaccine design targeting Oropouche virus structural proteins

In recent years, Brazil has recorded approximately 500,000 Oropouche virus (OROV) cases in the Amazon region, underscoring the growing global threat posed by emerging and reemerging viruses. Symptoms of OROV closely resemble those of Dengue virus and Zika virus, contributing to underreporting and underestimation of its true impact. In the absence of specific treatments, the development of vaccines becomes essential. This study aimed to identify immunogenic epitopes in three structural proteins of OROV and develop a multi-epitope vaccine candidate. RefSeq sequences of the nucleocapsid protein and the Gn and Gc glycoproteins were obtained from the National Center for Biotechnology Information Virus and submitted to epitope search in Immune Epitope Database. Antigenicity, allergenicity, stability, and toxicity analyses were conducted, and the approved epitopes were aligned to the global protein to remove transmembrane regions and N-glycosylation sites. Thirteen epitopes were selected and used to construct a multi-epitope vaccine candidate, with β-defensin and PADRE adjuvants. The protein demonstrated optimal antigenicity, low allergenicity, and satisfactory stability and solubility. Predictions of humoral and cellular immune responses were performed, indicating satisfactory results for three doses of the vaccine candidate. 3D modeling of the protein was performed, evaluating the molecular docking of the multi-epitope protein with TLR-2, TLR-3, TLR-6, and TLR-8 receptors. Our findings present a promising vaccine candidate against OROV, potentially protecting immunocompromised individuals and high-risk populations, and establishing a foundation for both in vitro and in vivo testing. The identified epitopes could also aid in immunodiagnostic test development, advancing surveillance and control strategies.

The Role of Orthobunyavirus Glycoprotein Gc in the Viral Life Cycle: From Viral Entry to Egress

Orthobunyavirus refers to the virus members within the Genus Orthobunyavirus, which is the largest virus genus in the Family Peribunyaviridae and even Class Bunyaviricetes. To date, over 130 species of Orthobunyaviruses have been identified worldwide. Orthobunyaviruses mainly infect arthropods, while some species are capable of being transmitted to mammals, including humans, via intermediate vectors. As emerging and re-emerging pathogens, orthobunyavirus poses a significant threat to both human and veterinary public health worldwide. Currently, there are no commercial vaccines against orthobunyavirus. The structure of orthobunyavirus is relatively simple, consisting of a typical tri-segmented negative-sense RNA genome that encodes four structural proteins (L, Gn, Gc, and N) and two non-structural proteins (NSm and NSs). The highly glycosylated Gc protein, which has a complex conformation and forms polymers embedded in the viral envelope, plays a critical role in inducing neutralizing antibodies throughout the orthobunyavirus infection cycle from entry to egress. This review provides a comprehensive summary of the virus-encoded Gc protein and its role in the virus life cycle from viral entry to egress, offering researchers with valuable integrated information for further investigations.

Introduction of Vector-Borne Infections in Europe: Emerging and Re-Emerging Viral Pathogens with Potential Impact on One Health

The rise and resurgence of vector-borne diseases (VBDs) in Europe pose an expanding public health challenge, exacerbated by climate change, globalization, and ecological disruptions. Both arthropod-borne viruses (arboviruses) transmitted by ticks such as Crimean-Congo hemorrhagic fever and arboviruses transmitted by mosquitoes like dengue, Chikungunya, Zika, and Japanese encephalitis have broadened their distribution due to rising temperatures, changes in rainfall, and increased human mobility. By emphasizing the importance of interconnected human, animal, and environmental health, integrated One Health strategies are crucial in addressing this complex issue. Europe faces increased risk due to the expanding habitats of disease-carrying organisms, the spread of new species like Aedes albopictus since 2013, and increased movement of infected individuals between countries, leading European countries to implement strategies such as enhanced surveillance systems, public awareness campaigns, and prompt outbreak response strategies. However, the lack of both targeted antiviral therapies and vaccines for many arboviruses, together with undetected or asymptomatic cases, hamper containment efforts. Therefore, it is important to have integrated strategies that combine climate modeling, disease surveillance, and public health interventions to address expected changes in disease patterns due to global changes. This review explores the spread of arboviruses in Europe, highlighting their historical context, current transmission dynamics, and their impact on public health.

Addressing the emerging threat of Oropouche virus: implications and public health responses for healthcare systems

Oropouche fever is an increasingly significant health concern in tropical and subtropical areas of South and Central America, and is primarily spread by midge vectors. The Oropouche virus (OROV) was first identified in 1955 and has been responsible for numerous outbreaks, particularly in urban environments. Despite its prevalence, the disease is often under-reported, making it difficult to fully understand its impact. OROV typically causes febrile illness characterized by symptoms such as headaches, muscle pain, and, occasionally, neurological issues such as meningitis. The ability of the virus to thrive in both forested and urban areas has raised concerns regarding its potential spread to new regions, particularly in the context of climate change. This paper delves into the epidemiology, clinical features, and transmission patterns of OROV, shedding light on the difficulties in diagnosing and managing the disease. The absence of specific treatments and vaccines highlights the urgent need for continued research and development of targeted public health strategies. Advancements in molecular diagnostics and vector control strategies can mitigate Oropouche fever's impact. However, a comprehensive public health approach involving increased surveillance, public education, and cross-border collaboration is needed, especially as the global climate crisis may expand vector habitats, posing risks to previously unaffected regions.

Oropouche virus: Understanding "sloth fever" disease dynamics and novel intervention strategies against this emerging neglected tropical disease

Oropouche virus (OROV), an arbovirus belonging to the Orthobunyavirus genus and Peribunyaviridae family, is the causative agent of the so-called "sloth fever." The virus primarily relies on the midge vector Culicoides paraensis for transmission, maintaining both sylvatic and urban cycles. Human infections are characterized by acute febrile symptoms, and severe cases can lead to neurological complications. Since its first isolation in 1955, OROV has caused numerous outbreaks throughout South America, infecting over half a million people. Recent outbreaks in the Amazon and the Caribbean, along with cases reported in U.S. travellers, underscore the growing threat of OROV amid climate change and increased global travel. With no FDA-approved vaccines or specific antiviral treatments available, current management of the disease caused by OROV infection is limited to supportive care. The urgent need for effective vaccines is amplified by the potential for geographic expansion of the virus and its transmitting vector(s). The ongoing development of OROV vaccine candidates represents a crucial step towards controlling future OROV outbreaks and enhancing global public-health preparedness against this emerging infectious disease.

Emergence of Oropouche fever in Latin America: a narrative review

Since its discovery in 1955, the incidence and geographical spread of reported Oropouche virus (OROV) infections have increased. Oropouche fever has been suggested to be one of the most important vector-borne diseases in Latin America. However, both literature on OROV and genomic sequence availability are scarce, with few contributing laboratories worldwide. Three reassortant OROV glycoprotein gene variants termed Iquitos, Madre de Dios, and Perdões virus have been described from humans and non-human primates. OROV predominantly causes acute febrile illness, but severe neurological disease such as meningoencephalitis can occur. Due to unspecific symptoms, laboratory diagnostics are crucial. Several laboratory tests have been developed but robust commercial tests are hardly available. Although OROV is mainly transmitted by biting midges, it has also been detected in several mosquito species and a wide range of vertebrate hosts, which likely facilitates its widespread emergence. However, potential non-human vertebrate reservoirs have not been systematically studied. Robust animal models to investigate pathogenesis and immune responses are not available. Epidemiology, pathogenesis, transmission cycle, cross-protection from infections with OROV reassortants, and the natural history of infection remain unclear. This Review identifies Oropouche fever as a neglected disease and offers recommendations to address existing knowledge gaps, enable risk assessments, and ensure effective public health responses.

The Adaptive Immune Response against Bunyavirales

The Bunyavirales order includes at least fourteen families with diverse but related viruses, which are transmitted to vertebrate hosts by arthropod or rodent vectors. These viruses are responsible for an increasing number of outbreaks worldwide and represent a threat to public health. Infection in humans can be asymptomatic, or it may present with a range of conditions from a mild, febrile illness to severe hemorrhagic syndromes and/or neurological complications. There is a need to develop safe and effective vaccines, a process requiring better understanding of the adaptive immune responses involved during infection. This review highlights the most recent findings regarding T cell and antibody responses to the five Bunyavirales families with known human pathogens (Peribunyaviridae, Phenuiviridae, Hantaviridae, Nairoviridae, and Arenaviridae). Future studies that define and characterize mechanistic correlates of protection against Bunyavirales infections or disease will help inform the development of effective vaccines.

Oropouche virus: A neglected global arboviral threat

The Oropouche virus is an important arthropod-borne virus in the Peribunyaviridae family that can cause febrile illnesses, and it is widely distributed in tropical regions such as Central and South America. Since the virus was first identified, a large number of related cases are reported every year. No deaths have been reported to date, however, the virus can cause systemic infections, including the nervous and blood systems, leading to serious complications. The transmission of Oropouche virus occurs through both urban and sylvatic cycles, with the anthropophilic biting midge Culicoides paraensis serving as the primary vector in urban areas. Direct human-to-human transmission of Oropouche virus has not been observed. Oropouche virus consists of three segments, and the proteins encoded by the different segments enables the virus to replicate efficiently in the host and to resist the host's immune response. Phylogenetic analyses showed that Oropouche virus sequences are geographically distinct and have closer homologies with Iquitos virus and Perdoes virus, which belong to the family Peribunyaviridae. Despite the enormous threat it poses to public health, there are currently no licensed vaccines or specific antiviral treatments for the disease it causes. Recent studies have utilised imJatobal virusmunoinformatics approaches to develop epitope-based peptide vaccines, which have laid the groundwork for the clinical use of vaccines. The present review focuses on the structure, epidemiology, immunity and phylogeny of Oropouche virus, as well as the progress of vaccine development, thereby attracting wider attention and research, particularly with regard to potential vaccine programs.

Bunyavirales: Scientific Gaps and Prototype Pathogens for a Large and Diverse Group of Zoonotic Viruses

Research directed at select prototype pathogens is part of the approach put forth by the National Institute of Allergy and Infectious Disease (NIAID) to prepare for future pandemics caused by emerging viruses. We were tasked with identifying suitable prototypes for four virus families of the Bunyavirales order (Phenuiviridae, Peribunyaviridae, Nairoviridae, and Hantaviridae). This is a challenge due to the breadth and diversity of these viral groups. While there are many differences among the Bunyavirales, they generally have complex ecological life cycles, segmented genomes, and cause a range of human clinical outcomes from mild to severe and even death. Here, we delineate potential prototype species that encompass the breadth of clinical outcomes of a given family, have existing reverse genetics tools or animal disease models, and can be amenable to a platform approach to vaccine testing. Suggested prototype pathogens outlined here can serve as a starting point for further discussions.

Establishment of Replication Deficient Vesicular Stomatitis Virus for Studies of PEDV Spike-Mediated Cell Entry and Its Inhibition

The porcine epidemic diarrhea virus (PEDV) is a highly contagious and virulent enteric coronavirus that causes severe enteric disease in pigs worldwide. PEDV infection causes profound diarrhea, vomiting, and dehydration in pigs of all ages, resulting in high mortality rates, particularly among neonatal piglets. The spike glycoprotein (S) of PEDV plays a crucial role in binding to the host cell receptor and facilitating fusion between the viral and host membranes. Pseudotyped viral particles featuring the PEDV S protein are valuable tools for investigating virus entry, identifying neutralizing antibodies, and developing small molecules to impede virus replication. In this study, we used a codon-optimized PEDV S protein to generate recombinant pseudotyped vesicular stomatitis virus (VSV) particles (rVSV-ΔG-EGFP-S). The full-length S protein was efficiently incorporated into VSV particles. The S protein pseudotyped VSV exhibited infectivity towards permissive cell lines of PEDV. Moreover, we identified a new permissive cell line, JHH7, which showed robust support for PEDV replication. In contrast to the SARS-CoV-2 spike protein, the removal of amino acids from the cytoplasmic tail resulted in reduced efficiency of viral pseudotyping. Furthermore, we demonstrated that 25-hydroxycholesterol inhibited rVSV-ΔG-EGFP-S entry, while human APN facilitated rVSV-ΔG-EGFP-S entry through the use of ANPEP knockout Huh7 cells. Finally, by transducing swine intestinal organoids with the rVSV-ΔG-EGFP-S virus, we observed efficient infection of the swine intestinal organoids by the PEDV spike-pseudotyped VSV. Our work offers valuable tools for studying the cellular entry of PEDV and developing interventions to curb its transmission.

Structure, function, and evolution of the Orthobunyavirus membrane fusion glycoprotein

La Crosse virus, responsible for pediatric encephalitis in the United States, and Schmallenberg virus, a highly teratogenic veterinary virus in Europe, belong to the large Orthobunyavirus genus of zoonotic arthropod-borne pathogens distributed worldwide. Viruses in this under-studied genus cause CNS infections or fever with debilitating arthralgia/myalgia syndromes, with no effective treatment. The main surface antigen, glycoprotein Gc (∼1,000 residues), has a variable N-terminal half (Gc^S) targeted by the patients' antibody response and a conserved C-terminal moiety (Gc^F) responsible for membrane fusion during cell entry. Here, we report the X-ray structure of post-fusion La Crosse and Schmallenberg virus Gc^F, revealing the molecular determinants for hairpin formation and trimerization required to drive membrane fusion. We further experimentally confirm the role of residues in the fusion loops and in a vestigial endoplasmic reticulum (ER) translocation sequence at the Gc^S-Gc^F junction. The resulting knowledge provides essential molecular underpinnings for future development of potential therapeutic treatments and vaccines.

Oropouche orthobunyavirus infection is mediated by the cellular host factor Lrp1

Oropouche orthobunyavirus (OROV; Peribunyaviridae) is a mosquito-transmitted virus that causes widespread human febrile illness in South America, with occasional progression to neurologic effects. Host factors mediating the cellular entry of OROV are undefined. Here, we show that OROV uses the host protein low-density lipoprotein-related protein 1 (Lrp1) for efficient cellular infection. Cells from evolutionarily distinct species lacking Lrp1 were less permissive to OROV infection than cells with Lrp1. Treatment of cells with either the high-affinity Lrp1 ligand receptor-associated protein (RAP) or recombinant ectodomain truncations of Lrp1 significantly reduced OROV infection. In addition, chimeric vesicular stomatitis virus (VSV) expressing OROV glycoproteins (VSV-OROV) bound to the Lrp1 ectodomain in vitro. Furthermore, we demonstrate the biological relevance of the OROV-Lrp1 interaction in a proof-of-concept mouse study in which treatment of mice with RAP at the time of infection reduced tissue viral load and promoted survival from an otherwise lethal infection. These results with OROV, along with the recent finding of Lrp1 as an entry factor for Rift Valley fever virus, highlight the broader significance of Lrp1 in cellular infection by diverse bunyaviruses. Shared strategies for entry, such as the critical function of Lrp1 defined here, provide a foundation for the development of pan-bunyaviral therapeutics.

Baseline mapping of Oropouche virology, epidemiology, therapeutics, and vaccine research and development

Oropouche virus (OROV) is an arthropod-borne orthobunyavirus found in South America and causes Oropouche fever, a febrile infection similar to dengue. It is the second most prevalent arthropod-borne viral disease in South America after dengue. Over 500,000 cases have been diagnosed since the virus was first discovered in 1955; however, this is likely a significant underestimate given the limited availability of diagnostics. No fatalities have been reported to date, however, up to 60% of cases have a recurrent phase of disease within one month of recovery from the primary disease course. The main arthropod vector is the biting midge Culicoides paraensis, which has a geographic range as far north as the United States and demonstrates the potential for OROV to geographically expand. The transmission cycle is incompletely understood and vertebrate hosts include both non-human primates and birds further supporting the potential ability of the virus to spread. A number of candidate antivirals have been evaluated against OROV in vitro but none showed antiviral activity. Surprisingly, there is only one report in the literature on candidate vaccines. We suggest that OROV is an undervalued pathogen much like chikungunya, Schmallenberg, and Zika viruses were before they emerged. Overall, OROV is an important emerging disease that has been under-investigated and has the potential to cause large epidemics in the future. Further research, in particular candidate vaccines, is needed for this important pathogen.