Genetic control of alphavirus pathogenesis

YBX1 is required for assembly of viral replication complexes of chikungunya virus and replication of multiple alphaviruses

Chikungunya virus (CHIKV), an enveloped positive-sense RNA virus, is a member of the alphaviruses and cause fever and arthralgia in humans. We performed genome-wide CRISPR/Cas9-based screens and identified Y-box binding protein 1 (YBX1) as an essential cellular factor for CHIKV. Deficiency of YBX1 inhibited CHIKV RNA replication and impaired virus production. Upon CHIKV infection, YBX1 showed a striking re-localization to viral replication complexes (vRCs), where it co-localized with CHIKV nsP3 and dsRNA intermediates. YBX1 directly interacted with CHIKV nsP3, and mutation of the YBX1-binding motif in CHIKV nsP3 suppressed viral replication in host cells. Furthermore, YBX1 bound to viral RNA and increased the viral RNA-binding activity of CHIKV nsP3. Consistently, the RNA-binding activity of YBX1, as well as the ability of nsP3 to bind to YBX1, was required for efficient CHIKV replication. In addition to CHIKV, YBX1 was also essential for replication of all examined alphaviruses including the prototypic alphavirus. Our findings suggest that YBX1 acts as a scaffold for assembly of chikungunya vRCs and an important factor for replication of multiple alphaviruses, which may serve as a potential target for the development of anti-alphavirus therapies.IMPORTANCEAlphaviruses are a group of mosquito-transmitted, enveloped, positive-strand RNA viruses in the Togaviridae family. Most alphaviruses are important pathogens that continue to cause human disease ranging from severe and potentially fatal neurological disease to chronic arthritic disease on a global scale. Here, we found that YBX1 promotes binding of CHIKV genomic RNA to nsP3, which is a key component of the replication complex, and is therefore pivotal for CHIKV replication. Deficiency of YBX1 results in reduced replication of multiple alphaviruses, including arthritogenic and encephalitic alphaviruses. These findings suggest that YBX1 is an important cellular factor for multiple alphaviruses and a potential target for preventing alphavirus infections.

Neuropathogenesis of Old World Alphaviruses: Considerations for the Development of Medical Countermeasures

Chikungunya virus (CHIKV) and other alphaviruses that primarily induce arthritogenic disease in humans, known as "Old World" alphaviruses, present an emerging public health concern as geographic ranges of mosquito vectors expand due to climate change. While a vaccine against CHIKV has recently been approved by several countries in North America and Europe, access to effective preventative countermeasures against disease induced by Old World alphaviruses remains elusive for the most vulnerable populations. Furthermore, treatment options continue to be limited to supportive care. Atypical neurological disease manifestations caused by Old World alphaviruses, which make up as many as 25% of the cases in some CHIKV outbreaks, present special challenges when considering strategies for developing effective countermeasures. This review focuses on Old World alphaviruses, specifically CHIKV, Ross River virus, O'nyoug-nyoug virus, and Mayaro virus, concentrating on the atypical neurological disease manifestations they may cause. Our current understanding of Old World alphavirus neuropathogenesis, gained from human cases and preclinical animal models, is discussed, including viral and host factors' roles in disease development. The current state of alphavirus preventatives and treatments, both virus-targeting and host-directed therapies, is then summarized and discussed in the context of addressing neurological disease induced by Old World alphaviruses.

Unraveling the complex interplay: immunopathology and immune evasion strategies of alphaviruses with emphasis on neurological implications

Arthritogenic alphaviruses pose a significant public health concern due to their ability to cause joint inflammation, with emerging evidence of potential neurological consequences. In this review, we examine the immunopathology and immune evasion strategies employed by these viruses, highlighting their complex mechanisms of pathogenesis and neurological implications. We delve into how these viruses manipulate host immune responses, modulate inflammatory pathways, and potentially establish persistent infections. Further, we explore their ability to breach the blood-brain barrier, triggering neurological complications, and how co-infections exacerbate neurological outcomes. This review synthesizes current research to provide a comprehensive overview of the immunopathological mechanisms driving arthritogenic alphavirus infections and their impact on neurological health. By highlighting knowledge gaps, it underscores the need for research to unravel the complexities of virus-host interactions. This deeper understanding is crucial for developing targeted therapies to address both joint and neurological manifestations of these infections.

A rare case of chikungunya encephalitis and its management: A case report and literature review

Key Clinical Message

Chikungunya encephalitis, though rare, warrants clinical attention due to its severe complications. Early identification and appropriate management are crucial for improved outcomes in patients with this rare manifestation of chikungunya virus (CHIKV) infection.

Abstract

CHIKV infection is commonly associated with fever and joint pains, but neurological complications such as encephalitis are rare. Here, we present a unique case of confirmed chikungunya encephalitis in a 12-year-old male exhibiting atypical neurological symptoms. The diagnostic journey involved comprehensive neuroimaging and serological investigations, revealing intriguing findings on magnetic resonance imaging and positive CHIKV RNA in serum and cerebrospinal fluid. We discuss the clinical presentation, radiological characteristics, and management strategies, emphasizing the importance of recognizing this uncommon neurological manifestation of CHIKV infection.

Mechanistic insights into bone remodelling dysregulation by human viral pathogens

Bone-related diseases (osteopathologies) associated with human virus infections have increased around the globe. Recent findings have highlighted the intricate interplay between viral infection, the host immune system and the bone remodelling process. Viral infections can disrupt bone homeostasis, contributing to conditions such as arthritis and soft tissue calcifications. Osteopathologies can occur after arbovirus infections such as chikungunya virus, dengue virus and Zika virus, as well as respiratory viruses, such as severe acute respiratory syndrome coronavirus 2 and enteroviruses such as Coxsackievirus B. Here we explore how human viruses dysregulate bone homeostasis, detailing viral factors, molecular mechanisms, host immune response changes and bone remodelling that ultimately result in osteopathologies. We highlight model systems and technologies to advance mechanistic understanding of viral-mediated bone alterations. Finally, we propose potential prophylactic and therapeutic strategies, introduce 'osteovirology' as a research field highlighting the underestimated roles of viruses in bone-related diseases, and discuss research avenues for further investigation.

Consideration of serum IL-36α and β levels trends in two patients with chikungunya fever

Key Clinical Message

IL-36 might play a role as an initial immune mechanism against chikungunya fever, and regulating IL-36 production could be a potential treatment approach for this condition.

Abstract

Two Japanese siblings visited Cook Islands in 2015 and developed Chikungunya fever upon their return. The sister experienced high fever, joint pain, and leg swelling, while the brother had joint pain and a rash. Both siblings had a confirmed CHIKV infection and continued to experience prolonged joint pain, with the sister enduring chronic pain for about a year. In this study, the levels of IL-36 in the serum of two siblings who were infected with chikungunya fever during the acute and recovery phases were compared using ELISA. IL-36 is a cytokine that induces inflammation and is produced by cells in tissues such as the skin and mucosa. It was hypothesized that IL-36 may be involved in persistent joint pain after chikungunya fever infection. Both siblings experienced long-lasting joint pain after chikungunya fever infection. The levels of IL-36α and IL-36β decreased by 56 days after infection. In the results, IL-36 plays an important role in host immunity and may act as part of the immune response during chikungunya virus infection. Inhibiting the release of IL-36 could be a promising approach for developing new treatment methods for chikungunya fever.

Chikungunya Encephalitis: an Inconsistently Reported Headache and Cause of Death in Patients with Pre-Existing Conditions

Chikungunya virus (CHIKV) is an alphavirus of the family Togaviridae with outbreaks occurring across Africa, Asia, parts of Europe, and South and Central America. There are three main lineages of CHIKV, including the West African lineage, the East Central South African (ECSA) lineage, and the Asian lineage. While CHIKV infection usually results in a self-limited febrile illness, there have been reports of concerning neurological manifestations, including encephalitis. Herein we discuss findings of over 700 cases of CHIKV encephalitis and risk factors for death. Additionally, we examined the genotypes of CHIKV associated with encephalitis and found that both the Asian and ECSA lineages were responsible for encephalitis but not the West African lineage. Protein analysis of consensus sequences of CHIKV strains associated with encephalitis identified mutations in the nsP1, nsP2, and nsP3 proteins. Reports and manuscripts of CHIKV encephalitis were inconsistent in reporting viral, demographic, and clinical features which complicated the delineation of risk factors associated with the disease and viral evolution. As climate change contributes to the range expansion of natural vectors, it is important for researchers and clinicians to consistently report patient and viral data to facilitate research and countermeasures for the ecology and epidemiology of CHIKV due to the lack of a targeted treatment or vaccine.

Chikungunya and arthritis: An overview

Chikungunya is caused by CHIKV (chikungunya virus), an emerging and re-emerging arthropod-vectored viral infection that causes a febrile disease with primarily long term sequelae of arthralgia and myalgia and is fatal in a small fraction of infected patients. Sporadic outbreaks have been reported from different parts of the world chiefly Africa, Asia, the Indian and Pacific ocean regions, Europe and lately even in the Americas. Currently, treatment is primarily symptomatic as no vaccine, antibody-mediated immunotherapy or antivirals are available. Chikungunya belongs to a family of arthritogenic alphaviruses which have many pathophysiological similarities. Chikungunya arthritis has similarities and differences with rheumatoid arthritis. Although research into arthritis caused by these alphaviruses have been ongoing for decades and significant progress has been made, the mechanisms underlying viral infection and arthritis are not well understood. In this review, we give a background to chikungunya and the causative virus, outline the history of alphavirus arthritis research and then give an overview of findings on arthritis caused by CHIKV. We also discuss treatment options and the research done so far on various therapeutic intervention strategies.

Alphaviruses: Host pathogenesis, immune response, and vaccine & treatment updates

Human pathogens belonging to the Alphavirus genus, in the Togaviridae family, are transmitted primarily by mosquitoes. The signs and symptoms associated with these viruses include fever and polyarthralgia, defined as joint pain and inflammation, as well as encephalitis. In the last decade, our understanding of the interactions between members of the alphavirus genus and the human host has increased due to the re-appearance of the chikungunya virus (CHIKV) in Asia and Europe, as well as its emergence in the Americas. Alphaviruses affect host immunity through cytokines and the interferon response. Understanding alphavirus interactions with both the innate immune system as well as the various cells in the adaptive immune systems is critical to developing effective therapeutics. In this review, we summarize the latest research on alphavirus-host cell interactions, underlying infection mechanisms, and possible treatments.

Complex Roles of Neutrophils during Arboviral Infections

Arboviruses are known to cause large-scale epidemics in many parts of the world. These arthropod-borne viruses are a large group consisting of viruses from a wide range of families. The ability of their vector to enhance viral pathogenesis and transmission makes the development of treatments against these viruses challenging. Neutrophils are generally the first leukocytes to be recruited to a site of infection, playing a major role in regulating inflammation and, as a result, viral replication and dissemination. However, the underlying mechanisms through which neutrophils control the progression of inflammation and disease remain to be fully understood. In this review, we highlight the major findings from recent years regarding the role of neutrophils during arboviral infections. We discuss the complex nature of neutrophils in mediating not only protection, but also augmenting disease pathology. Better understanding of neutrophil pathways involved in effective protection against arboviral infections can help identify potential targets for therapeutics.

Host cell glutamine metabolism as a potential antiviral target

A virus minimally contains a nucleic acid genome packaged by a protein coat. The genome and capsid together are known as the nucleocapsid, which has an envelope containing a lipid bilayer (mainly phospholipids) originating from host cell membranes. The viral envelope has transmembrane proteins that are usually glycoproteins. The proteins in the envelope bind to host cell receptors, promoting membrane fusion and viral entry into the cell. Virus-infected host cells exhibit marked increases in glutamine utilization and metabolism. Glutamine metabolism generates ATP and precursors for the synthesis of macromolecules to assemble progeny viruses. Some compounds derived from glutamine are used in the synthesis of purines and pyrimidines. These latter compounds are precursors for the synthesis of nucleotides. Inhibitors of glutamine transport and metabolism are potential candidate antiviral drugs. Glutamine is also an essential nutrient for the functions of leukocytes (lymphocyte, macrophage, and neutrophil), including those in virus-infected patients. The increased glutamine requirement for immune cell functions occurs concomitantly with the high glutamine utilization by host cells in virus-infected patients. The development of antiviral drugs that target glutamine metabolism must then be specifically directed at virus-infected host cells to avoid negative effects on immune functions. Therefore, the aim of this review was to describe the landscape of cellular glutamine metabolism to search for potential candidates to inhibit glutamine transport or glutamine metabolism.

Association of Genetic Polymorphisms in DC-SIGN, Toll-Like Receptor 3, and Tumor Necrosis Factor α Genes and the Lewis-Negative Phenotype With Chikungunya Infection and Disease in Nicaragua

Background

Chikungunya infections range from subclinical infection to debilitating arthralgia and to chronic inflammatory rheumatism. Tumor necrosis factor (TNF) α, DC-SIGN (dendritic cell–specific intercellular adhesion molecule 3–grabbing nonintegrin), Toll-like receptor (TLR) 3, and blood groups have been directly or indirectly implicated in the susceptibility and pathogenesis of chikungunya.

Methods

To test the hypothesis that polymorphisms in genes coding for these molecules determine clinical outcomes of chikungunya infection, a retrospective case-control study was performed in León, Nicaragua. The study included 132 case patients and 132 controls, matched for age, sex and neighborhood. Case patients had clinical symptoms of chikungunya, which was diagnosed by means of polymerase chain reaction. Controls were individuals not reporting abrupt presentation of clinical chikungunya-like symptoms. Polymorphisms were identified by TaqMan single-nucleotide polymorphism genotyping assays.

Results

After adjustment for sociodemographic risk factors, chikungunya disease was associated with polymorphism in DC-SIGN and TLR3 genes (odds ratios, 5.2 and 3.3, respectively), and TNF-α with reduced persistent joint pain (0.24). Persistent joint pain was also associated with age, female sex and other comorbid conditions. Most interestingly, the Lewis-negative phenotype was strongly associated with both symptomatic chikungunya and immunoglobulin G seropositivity (odds ratios, 2.7, and 3.3, respectively).

Conclusion

This study identified polymorphisms in DC-SIGN, TLR3, and TNF-α genes as well as Lewis-negative phenotype as risk factors for chikungunya infection and disease progression.