Persistent arthralgia induced by Chikungunya virus infection is associated with interleukin-6 and granulocyte macrophage colony-stimulating factor

Mayaro Virus Infects Human Chondrocytes and Induces the Expression of Arthritis-Related Genes Associated with Joint Degradation

Mayaro virus (MAYV) is an emerging arthritogenic alphavirus belonging to the Togaviridae family. Infection leads to a dengue-like illness accompanied by severe polyarthralgia. However, the molecular and cellular mechanisms of arthritis as a result of MAYV infection remain poorly understood. In the present study, we assess the susceptibility of human chondrocytes (HC), fibroblast-like synoviocytes and osteoblasts that are the major cell types involved in osteoarthritis, to infection with MAYV. We show that these cells are highly permissive to MAYV infection and that viral RNA copy number and viral titers increase over time in infected cells. Knowing that HC are the primary cells in articular cartilage and are essential for maintaining the cartilaginous matrix, gene expression studies were conducted in MAYV-infected primary HC using polymerase chain reaction (PCR) arrays. The infection of the latter cells resulted in an induction in the expression of several matrix metalloproteinases (MMP) including MMP1, MMP7, MMP8, MMP10, MMP13, MMP14 and MMP15 which could be involved in the destruction of articular cartilage. Infected HC were also found to express significantly increased levels of various IFN-stimulated genes and arthritogenic mediators such as TNF-α and IL-6. In conclusion, MAYV-infected primary HC overexpress arthritis-related genes, which may contribute to joint degradation and pathogenesis.

Dermal and muscle fibroblasts and skeletal myofibers survive chikungunya virus infection and harbor persistent RNA

Chikungunya virus (CHIKV) is an arthritogenic alphavirus that acutely causes fever as well as severe joint and muscle pain. Chronic musculoskeletal pain persists in a substantial fraction of patients for months to years after the initial infection, yet we still have a poor understanding of what promotes chronic disease. While replicating virus has not been detected in joint-associated tissues of patients with persistent arthritis nor in various animal models at convalescent time points, viral RNA is detected months after acute infection. To identify the cells that might contribute to pathogenesis during this chronic phase, we developed a recombinant CHIKV that expresses Cre recombinase (CHIKV-3'-Cre). CHIKV-3'-Cre replicated in myoblasts and fibroblasts, and it induced arthritis during the acute phase in mice. Importantly, it also induced chronic disease, including persistent viral RNA and chronic myositis and synovitis similar to wild-type virus. CHIKV-3'-Cre infection of tdTomato reporter mice resulted in a population of tdTomato+ cells that persisted for at least 112 days. Immunofluorescence and flow cytometric profiling revealed that these tdTomato+ cells predominantly were myofibers and dermal and muscle fibroblasts. Treatment with an antibody against Mxra8, a recently defined host receptor for CHIKV, reduced the number of tdTomato+ cells in the chronic phase and diminished the levels of chronic viral RNA, implicating these tdTomato+ cells as the reservoir of chronic viral RNA. Finally, isolation and flow cytometry-based sorting of the tdTomato+ fibroblasts from the skin and ankle and analysis for viral RNA revealed that the tdTomato+ cells harbor most of the persistent CHIKV RNA at chronic time points. Therefore, this CHIKV-3'-Cre and tdTomato reporter mouse system identifies the cells that survive CHIKV infection in vivo and are enriched for persistent CHIKV RNA. This model represents a useful tool for studying CHIKV pathogenesis in the acute and chronic stages of disease.

IL-27 in patients with Chikungunya fever: A possible chronicity biomarker?

BACKGROUND/PURPOSE

Although many patients with chikungunya virus disease (CHIKVD), an arboviral disease characterized by sudden fever and incapacitating poliartralgia, develop chronic articular symptoms, the mechanisms involved in CHIKVD's chronification and its possible biomarkers remain poorly understood. Interleukin (IL)-17A, IL-21, IL-22, IL-29, and transforming growth factor (TGF)-β have been implicated in the pathogenesis of other inflammatory joint diseases, including rheumatoid arthritis, psoriatic arthritis, and ankylosing spondylitis. Since chronic manifestations of CHIKVD share many clinical and immunological characteristics with those diseases, we assessed the serum levels of those cytokines and analyzed their associations with clinical manifestations in patients with CHIKVD.

METHODS

We evaluated 45 patients (36 female, mean age: 55.2 ± 13.8 years) with CHIKVD serologically confirmed by enzyme-linked immunosorbent assay (ELISA), articular manifestations upon evaluation, and no previous history of inflammatory rheumatologic diseases, along with 49 healthy age- and sex-matched controls. We tested anti-Chikungunya IgM and IgG antibodies and measured IL-17A, IL-21, IL-22, IL-27, IL-29, and TGF-β serum levels with specific ELISA kits.

RESULTS

IL-27, IL-17A, and IL-29 appeared in most patients but not in controls. IL-27 serum levels were higher in patients with chronic symptoms (median: 523.0 pg/mL [62.5-1,048]) than in ones in the acute or subacute stage (median: 62.5 pg/mL [62.5-483.8], p = .008). In patients with CHIKVD, we found significant correlations between IL-27 levels and tender joint counts (r = .32, p = .006), along with associations between IL-17A levels and swollen joint counts (r = .315, p = .0352). Furthermore, patients with arthritis had higher IL-17A levels (median: 23.14 pg/mL [20.6-25.86]) than ones without (median: 20.29 pg/mL [3.91-22.43], p = .0352). We did not detect IL-22 in either group or IL-21 in patients with CHIKVD.

CONCLUSION

Serum levels of IL-17A, IL-27, and IL-29 were high in patients with CHIKVD and had important associations with articular manifestations, which might indicate the inflammatory nature of Chikungunya infection in patients with joint symptoms and the roles of those cytokines in the disease's pathophysiology.

Association of IL1RN VNTR polymorphism with chikungunya infection: A study from Western India

Chikungunya, caused by the chikungunya virus (CHIKV) mostly presents as acute and chronic articular inflammatory manifestations. Interleukin 1 receptor antagonist (IL-1RN) is a potent endogenous competitive inhibitor of IL-1α and 1β and has an anti-inflammatory role. The present study evaluated the possible association of IL1RN variable number tandem-repeat (VNTR) alleles and genotypes, and CHIKV stimulated IL-1RN cytokine production with resistance and/or susceptibility to chikungunya infection and disease state in 224 patients with chikungunya (61 patients with acute chikungunya and 163 patients with chronic chikungunya) and 355 healthy controls. Polymerase chain reaction, CHIKV stimulated cytokine assay and luminex platform were used for assessing polymorphism and protein levels respectively. The study revealed a significant association of IL1RN*1/*1 genotype under recessive genetic model with the risk of developing chikungunya infection. Our findings also indicated that IL1RN *2 allele under dominant mode was associated with protection to chronic chikungunya. The results also revealed a higher production of IL-1 RN protein in patients with chronic chikungunya. To conclude, the results suggest the association of ILRN VNTR polymorphism and IL-RN protein levels with chronic chikungunya.

Treatment of Chronic Chikungunya Arthritis With Methotrexate: A Systematic Review

OBJECTIVE

Chikungunya virus infection is a rapidly emerging global viral infection that can cause chronic, debilitating arthritis that in some ways mimics rheumatoid arthritis. The aim of this study was to evaluate the available evidence regarding the efficacy and safety of methotrexate (MTX), a therapy that is widely used in rheumatoid arthritis, for the treatment of chronic chikungunya arthritis.

METHODS

A systematic literature search was performed to identify all published trials that evaluated MTX as monotherapy or combination therapy in patients with chronic chikungunya arthritis. PubMed, SciELO, Scopus, and Cochrane Library databases were searched from study inception to August 2017. We also searched Google Scholar, the International Clinical Trials Registry Platform Search Portal, and clinicaltrials.gov.

RESULTS

Among 131 possibly relevant studies, 6 met our criteria for evaluation: 4 were retrospective studies, 1 was a non-controlled prospective study, and 1 was an unblinded randomized clinical trial of combination MTX therapy. In the randomized clinical trial, triple therapy with MTX, hydroxychloroquine, and sulfasalazine was superior to hydroxychloroquine monotherapy, as assessed by the mean ± SD Disease Activity Score in 28 joints using the erythrocyte sedimentation rate (3.39 ± 0.87 versus 4.74 ± 0.65; P < 0.0001) and the Health Assessment Questionnaire score (1.14 ± 0.31 versus 1.88 ± 0.47; P < 0.0001).

CONCLUSION

The number of available studies is limited, but taken together, these studies demonstrate that MTX is sufficiently efficacious to justify further study of MTX for the treatment of chronic chikungunya arthritis. The trials lacked rigorous study designs and used different treatment strategies and outcome measures. This systematic review underscores the need for randomized, prospective, placebo-controlled studies of MTX monotherapy for the treatment of chronic chikungunya arthritis.

Inhibition of Interleukin-1β Signaling by Anakinra Demonstrates a Critical Role of Bone Loss in Experimental Arthritogenic Alphavirus Infections

OBJECTIVE

Arthritogenic alphaviruses, such as Ross River virus (RRV) and chikungunya virus (CHIKV), particularly affect joints of the extremities and can lead to debilitating and potentially chronic polyarthritis/polyarthralgia. The innate immune response of the host plays a crucial role in inducing proinflammatory host factors, leading to tissue destruction and bone loss in the joints. This study was performed to assess how the inhibition of interleukin-1β (IL-1β) signaling using the clinical rheumatoid arthritis drug anakinra influences bone loss in mice with arthritogenic alphavirus infections.

METHODS

Mice (n = 5 per group) were infected with RRV or CHIKV and then treated with anakinra. Weight gain and disease severity were measured, tissue viral titers were determined, and histologic changes in joint tissues were assessed.

RESULTS

Anakinra therapy reduced RRV- and CHIKV-induced bone loss in this murine model (P < 0.001 and P < 0.05, respectively). Histologic analysis of the knee joint showed that treatment with anakinra decreased epiphyseal growth plate thinning, loss of epiphyseal bone volume, and osteoclastogenesis in the tibia. Importantly, pharmacologic IL-1 receptor (IL-1R) blockade did not improve other clinical features, including disease score, weight loss, or viremia.

CONCLUSION

The present findings suggest that anakinra therapy may reduce bone loss in experimental murine models of RRV and CHIKV. Further investigations are needed to assess the potential therapeutic benefits of anakinra in patients with arthritogenic alphavirus disease.

An overview of the immune response and Arginase I on CHIKV immunopathogenesis

Chikungunya virus (CHIKV) is mosquito-borne alphavirus that has caused epidemics around the world. Many individuals affected by the disease may experience joint pain that persists for months after the acute phase. The pathophysiology of viral arthritis is not completely elucidated. And it is important to emphasize that the effects of the viral infection in each host may depend on host factors that include immune response, as well as factors specific to the virus as tissue tropism. The main pathway for the response against viral infection is through induction of type I interferon (IFN-I), whose function is important to control viral replication. Beside this, T cell and macrophage mediated immunopathology in CHIKV infections has been reported. It has been demonstrated that some association with the Arginase I and macrophages type II are involved in the infection profile along with myeloid-derived suppressor cells (MDSC) that are responsible for T cell suppression. Therefore, in this review, will be discuss an overview on CHIKV immunopathogenesis and the importance of Arginase I.

Emergence and treatment of chikungunya arthritis

PURPOSE OF REVIEW

To review the emergence, clinical features, pathogenesis, and treatment of acute chikungunya (CHIK) fever and chronic CHIK arthritis.

RECENT FINDINGS

Since 2004, CHIK, an arboviral infection, has spread throughout the world, infecting millions of people. The illness occurs in two phases: an acute viremic infection followed by chronic arthritis. In less developed countries, there are limited resources and effective treatment. For acutely ill CHIK fever patients, management is symptomatic. The treatment of chronic CHIK arthritis should be determined by an understanding of pathogenesis. Is chronic CHIK arthritis a persistent viral infection or a postinfectious inflammatory process? Multiple proinflammatory cytokines, chemokines, and growth factors have been identified in chronic CHIK arthritis. Attempts to isolate CHIK virus from synovial fluid have been unsuccessful. Given pathogenetic similarities (as well as differences) compared with rheumatoid arthritis and the painful, disabling nature of the arthritis, it is not surprising that disease-modifying antirheumatic drugs such as methotrexate have begun to be used.

SUMMARY

CHIK infection has emerged with major arthritic epidemics for which evidence-based therapy is limited. But there is an opportunity to improve the treatment of chronic CHIK arthritis and, from this disease, to gain understanding of the pathogenesis and treatment of inflammatory arthritis more generally.

P38 and JNK Mitogen-Activated Protein Kinases Interact With Chikungunya Virus Non-structural Protein-2 and Regulate TNF Induction During Viral Infection in Macrophages

Chikungunya virus (CHIKV), a mosquito-borne Alphavirus, is endemic in different parts of the globe. The host macrophages are identified as the major cellular reservoirs of CHIKV during infection and this virus triggers robust TNF production in the host macrophages, which might be a key mediator of virus induced inflammation. However, the molecular mechanism underneath TNF induction is not understood yet. Accordingly, the Raw264.7 cells, a mouse macrophage cell line, were infected with CHIKV to address the above-mentioned question. It was observed that CHIKV induces both p38 and JNK phosphorylation in macrophages in a time-dependent manner and p-p38 inhibitor, SB203580 is effective in reducing infection even at lower concentration as compared to the p-JNK inhibitor, SP600125. However, inhibition of p-p38 and p-JNK decreased CHIKV induced TNF production in the host macrophages. Moreover, CHIKV induced macrophage derived TNF was found to facilitate TCR driven T cell activation. Additionally, it was noticed that the expressions of key transcription factors involved mainly in antiviral responses (p-IRF3) and TNF production (p-c-jun) were induced significantly in the CHIKV infected macrophages as compared to the corresponding mock cells. Further, it was demonstrated that CHIKV mediated TNF production in the macrophages is dependent on p38 and JNK MAPK pathways linking p-c-jun transcription factor. Interestingly, it was found that CHIKV nsP2 interacts with both p-p38 and p-JNK MAPKs in the macrophages. This observation was supported by the in silico protein-protein docking analysis which illustrates the specific amino acids responsible for the nsP2-MAPKs interactions. A strong polar interaction was predicted between Thr-180 (within the phosphorylation lip) of p38 and Gln-273 of nsP2, whereas, no such polar interaction was predicted for the phosphorylation lip of JNK which indicates the differential roles of p-p38 and p-JNK during CHIKV infection in the host macrophages. In summary, for the first time it has been shown that CHIKV triggers robust TNF production in the host macrophages via both p-p38 and p-JNK/p-c-jun pathways and the interaction of viral protein, nsP2 with these MAPKs during infection. Hence, this information might shed light in rationale-based drug designing strategies toward a possible control measure of CHIKV infection in future.

A bioinformatics investigation into the pharmacological mechanisms of the effect of Fufang Danshen on pain based on methodologies of network pharmacology

Fufang Danshen (FFDS), a Chinese medicine formula widely used in the clinic, has proven therapeutic effects on pain relief. However, the mechanisms of these effects have not been elucidated. Here, we performed a systematic analysis to discover the mechanisms of FFDS in attenuating pain to gain a better understanding of FFDS in the treatment of other diseases accompanied by pain. Relevance analysis showed that Salvia miltiorrhizae was the best studied herb in FFDS. Most compounds in FFDS have good bioavailability, and we collected 223 targets for 35 compounds in FFDS. These targets were significantly enriched in many pathways related to pain and can be classified as signal transduction, endocrine system, nervous system and lipid metabolism. We compared Salvia miltiorrhizae and Panax notoginseng and found that they can significantly affect different pathways. Moreover, ten pain disease proteins and 45 therapeutic targets can be directly targeted by FFDS. All 45 therapeutic targets have direct or indirect connections with pain disease proteins. Forty-six pain disease proteins can be indirectly affected by FFDS, especially through heat shock cognate 71 kDa protein (HSPA8) and transcription factor AP-1 (JUN). A total of 109 targets of FFDS were identified as significant targets.

The Clinical Features, Pathogenesis and Methotrexate Therapy of Chronic Chikungunya Arthritis

Chikungunya fever (CHIKF) is an emerging viral infection that has spread widely, along with its Aedes vectors, throughout the tropics and beyond, causing explosive epidemics of acute illness and persistent disabling arthritis. The rheumatic symptoms associated with chikungunya virus (CHIKV) infection include polyarthralgia, polyarthritis, morning stiffness, joint edema, and erythema. Chronic CHIK arthritis (CCA) often causes severe pain and associated disability. The pathogenesis of CCA is not well understood. Proposed hypotheses include the persistence of a low level of replicating virus in the joints, the persistence of viral RNA in the synovium, and the induction of autoimmunity. In this review, we describe the main hypotheses of CCA pathogenesis, some of which support methotrexate (MTX) treatment which has been shown to be effective in preliminary studies in CCA.

Arthritogenic Alphavirus-Induced Immunopathology and Targeting Host Inflammation as A Therapeutic Strategy for Alphaviral Disease

Arthritogenic alphaviruses are a group of medically important arboviruses that cause inflammatory musculoskeletal disease in humans with debilitating symptoms, such as arthralgia, arthritis, and myalgia. The arthritogenic, or Old World, alphaviruses are capable of causing explosive outbreaks, with some viruses of major global concern. At present, there are no specific therapeutics or commercially available vaccines available to prevent alphaviral disease. Infected patients are typically treated with analgesics and non-steroidal anti-inflammatory drugs to provide often inadequate symptomatic relief. Studies to determine the mechanisms of arthritogenic alphaviral disease have highlighted the role of the host immune system in disease pathogenesis. This review discusses the current knowledge of the innate immune response to acute alphavirus infection and alphavirus-induced immunopathology. Therapeutic strategies to treat arthritogenic alphavirus disease by targeting the host immune response are also examined.

GloPID-R report on Chikungunya, O'nyong-nyong and Mayaro virus, part I: Biological diagnostics

The GloPID-R (Global Research Collaboration for Infectious Disease Preparedness) Chikungunya (CHIKV), O'nyong-nyong (ONNV) and Mayaro virus (MAYV) Working Group is investigating the natural history, epidemiology and medical management of infection by these viruses, to identify knowledge gaps and to propose recommendations for direct future investigations and rectification measures. Here, we present the first report dedicated to diagnostic aspects of CHIKV, ONNV and MAYV. Regarding diagnosis of the disease at the acute phase, molecular assays previously described for the three viruses require further evaluation, standardized protocols and the availability of international standards representing the genetic diversity of the viruses. Detection of specific IgM would benefit from further investigations to clarify the extent of cross-reactivity among the three viruses, the sensitivity of the assays, and the possible interfering role of cryoglobulinaemia. Implementation of reference panels and external quality assessments for both molecular and serological assays is necessary. Regarding sero-epidemiological studies, there is no reported high-throughput assay that can distinguish among these different viruses in areas of potential co-circulation. New specific tools and/or improved standardized protocols are needed to enable large-scale epidemiological studies of public health relevance to be performed. Considering the high risk of future CHIKV, MAYV and ONNV outbreaks, the Working Group recommends that a major investigation should be initiated to fill the existing diagnostic gaps.

Tropism of the Chikungunya Virus

Chikungunya virus (CHIKV) is a re-emerging mosquito-borne virus that displays a large cell and organ tropism, and causes a broad range of clinical symptoms in humans. It is maintained in nature through both urban and sylvatic cycles, involving mosquito vectors and human or vertebrate animal hosts. Although CHIKV was first isolated in 1953, its pathogenesis was only more extensively studied after its re-emergence in 2004. The unexpected spread of CHIKV to novel tropical and non-tropical areas, in some instances driven by newly competent vectors, evidenced the vulnerability of new territories to this infectious agent and its associated diseases. The comprehension of the exact CHIKV target cells and organs, mechanisms of pathogenesis, and spectrum of both competitive vectors and animal hosts is pivotal for the design of effective therapeutic strategies, vector control measures, and eradication actions.

Virus load and clinical features during the acute phase of Chikungunya infection in children

BACKGROUND

Chikungunya virus (CHIKV) infection is a long known mosquito-borne disease that is associated with severe morbidity, characterized by fever, headache, rashes, joint pain, and myalgia. It is believed that virus load has relation with severity of clinical features.

OBJECTIVES

We performed this study to assess the relationship between virus load and clinical features in children during the acute phase of CHIKV infection, in order to draw insights for better-informed treatment.

STUDY DESIGN

Between June 1, 2009, and May 31, 2010, 338 patients with fever and susceptive to CHIKV during first 4 days of illness were prospectively enrolled from Karnataka Institute of Medical Sciences, Hubli in our hospital based cross sectional observational study. Sybr green quantitative reverse transcription polymerase chain reaction was performed to estimate the virus load.

RESULTS

Quantitative RT-PCR was positive for CHIKV in 54 patients. The median copy number of CHIKV was 1.3x 108 copies/ml (1.7x105-9.9x109 copies/ml). Among the observed clinical features, a statistically significant difference in log mean virus load was found between patients with and without myalgia (log mean 7.50 vs 8.34, P = 0.01).

CONCLUSION

Patients with myalgia had lower virus load and those without myalgia had a higher virus load.

Host target-based approaches against arboviral diseases

In the 20th century, socioeconomic and environmental changes facilitated the reintroduction of mosquitoes in developing cities, resulting in the reinsertion of mosquito-borne viral diseases and the dispersal of their causative agents on a worldwide scale. Recurrent outbreaks of arboviral diseases are being reported, even in regions without a previous history of arboviral disease transmission. Of note, arboviral infections represented approximately 30% of all emerging vector-borne diseases in the last decade. Therapeutic strategies against infectious viral diseases include the use of different classes of molecules that act directly on the pathogen and/or act by optimizing the host immune response. Drugs targeting the virus usually provide amelioration of symptoms by suppressing and controlling the infection. However, it is limited by the short-window of effectiveness, ineffectiveness against latent viruses, development of drug-resistant mutants and toxic side effects. Disease may also be a consequence of an excessive, uncontrolled or misplaced inflammatory response, treatments that interfere in host immune response are interesting options and can be used isolated or in combination with virus-targeted therapies. The use of host-targeted therapies requires specific knowledge regarding host immune patterns that may trigger dengue virus (DENV), chikungunya virus (CHIKV) or Zika virus (ZIKV) disease.

A scoping review of Chikungunya virus infection: epidemiology, clinical characteristics, viral co-circulation complications, and control

Chikungunya fever is a mosquito-borne viral illness characterized by a sudden onset of fever associated with joint pains. It was first described in the 1950s during a Chikungunya virus (CHIKV) outbreak in southern Tanzania and has since (re-) emerged and spread to several other geographical areas, reaching large populations and causing massive epidemics. In recent years, CHIKV has gained considerable attention due to its quick spread to the Caribbean and then in the Americas, with many cases reported between 2014 and 2017. CHIKV has further garnered attention due to the clinical diagnostic difficulties when Zika (ZIKV) and dengue (DENV) viruses are simultaneously present. In this review, topical CHIKV-related issues, such as epidemiology and transmission, are examined. The different manifestations of infection (acute, chronic and atypical) are described and a particular focus is placed upon the diagnostic handling in the case of ZIKV and DENV co-circulating. Natural and synthetic compounds under evaluation for treatment of chikungunya disease, including drugs already licensed for other purposes, are also discussed. Finally, previous and current vaccine strategies, as well as the control of the CHIKV transmission through an integrated vector management, are reviewed in some detail.

Defining a correlate of protection for chikungunya virus vaccines

Chikungunya virus infection causes a debilitating febrile illness that in many affected individuals is associated with long-term sequelae that can persist for months or years. Over the past decade a large number of candidate vaccines have been developed, several of which have now entered clinical trials. The rapid and sporadic nature of chikungunya outbreaks poses challenges for planning of large clinical efficacy trials suggesting that licensure of chikungunya vaccines may utilize non-traditional approval pathways based on identification of immunological endpoint(s) predictive of clinical benefit. This report reviews the current status of nonclinical and clinical testing and potential challenges for defining a suitable surrogate or correlate of protection.

Following in the Footsteps of the Chikungunya Virus in Brazil: The First Autochthonous Cases in Amapá in 2014 and Its Emergence in Rio de Janeiro during 2016

Currently, Brazil lives a triple arboviruses epidemic (DENV, ZIKV and CHIKV) making the differential diagnosis difficult for health professionals. Here, we aimed to investigate chikungunya cases and the possible occurrence of co-infections during the epidemic in Amapá (AP) that started in 2014 when the first autochthonous cases were reported and in Rio de Janeiro (RJ) in 2016. We further performed molecular characterization and genotyping of representative strains. In AP, 51.4% of the suspected cases were confirmed for CHIKV, 71.0% (76/107). Of those, 24 co-infections by CHIKV/DENV, two by CHIKV/DENV-1, and two by CHIKV/DENV-4 were observed. In RJ, 76.9% of the suspected cases were confirmed for CHIKV and co-infections by CHIKV/DENV (n = 8) and by CHIKV/ZIKV (n = 17) were observed. Overall, fever, arthralgia, myalgia, prostration, edema, exanthema, conjunctival hyperemia, lower back pain, dizziness, nausea, retroorbital pain, and anorexia were the predominating chikungunya clinical symptoms described. All strains analyzed from AP belonged to the Asian genotype and no amino acid changes were observed. In RJ, the East-Central-South-African genotype (ECSA) circulation was demonstrated and no E1-A226V mutation was observed. Despite this, an E1-V156A substitution was characterized in two samples and for the first time, the E1-K211T mutation was reported in all samples analyzed.

The Cytokine Profile in Acute Chikungunya Infection is Predictive of Chronic Arthritis 20 Months Post Infection

The cytokine profile during acute chikungunya infection that predicts future chronic arthritis has not yet been investigated. We conducted a nested case-control study comparing serum cytokine concentrations during acute chikungunya infection in cases (n = 121) that reported the presence of chronic joint pain versus age- and gender-matched controls (n = 121) who reported recovery at 20 months post infection. We observed that a robust cytokine response during acute infection was correlated with a decreased incidence of chronic joint pain and that low TNFα, IL-13, IL-2, and IL-4 during acute infection was predictive of chronic joint pain. These data suggest that a robust cytokine response is necessary for viral clearance and cytokines that are related to immune tolerance during acute infection may be protective for chronic arthritis pathogenesis.

Cellular and Molecular Immune Response to Chikungunya Virus Infection

Chikungunya virus (CHIKV) is a re-emergent arthropod-borne virus (arbovirus) that causes a disease characterized primarily by fever, rash and severe persistent polyarthralgia. In the last decade, CHIKV has become a serious public health problem causing several outbreaks around the world. Despite the fact that CHIKV has been around since 1952, our knowledge about immunopathology, innate and adaptive immune response involved in this infectious disease is incomplete. In this review, we provide an updated summary of the current knowledge about immune response to CHIKV and about soluble immunological markers associated with the morbidity, prognosis and chronicity of this arbovirus disease. In addition, we discuss the progress in the research of new vaccines for preventing CHIKV infection and the use of monoclonal antibodies as a promising therapeutic strategy.

Genetic control of alphavirus pathogenesis

Alphaviruses, members of the positive-sense, single-stranded RNA virus family Togaviridae, represent a re-emerging public health concern worldwide as mosquito vectors expand into new geographic ranges. Members of the alphavirus genus tend to induce clinical disease characterized by rash, arthralgia, and arthritis (chikungunya virus, Ross River virus, and Semliki Forest virus) or encephalomyelitis (eastern equine encephalitis virus, western equine encephalitis virus, and Venezuelan equine encephalitis virus), though some patients who recover from the initial acute illness may develop long-term sequelae, regardless of the specific infecting virus. Studies examining the natural disease course in humans and experimental infection in cell culture and animal models reveal that host genetics play a major role in influencing susceptibility to infection and severity of clinical disease. Genome-wide genetic screens, including loss of function screens, microarrays, RNA-sequencing, and candidate gene studies, have further elucidated the role host genetics play in the response to virus infection, with the immune response being found in particular to majorly influence the outcome. This review describes the current knowledge of the mechanisms by which host genetic factors influence alphavirus pathogenesis and discusses emerging technologies that are poised to increase our understanding of the complex interplay between viral and host genetics on disease susceptibility and clinical outcome.

Comprehensive innate immune profiling of chikungunya virus infection in pediatric cases

Chikungunya virus (CHIKV) is a mosquito-borne alphavirus that causes global epidemics of debilitating disease worldwide. To gain functional insight into the host cellular genes required for virus infection, we performed whole-blood RNA-seq, 37-plex mass cytometry of peripheral blood mononuclear cells (PBMCs), and serum cytokine measurements of acute- and convalescent-phase samples obtained from 42 children naturally infected with CHIKV Semi-supervised classification and clustering of single-cell events into 57 sub-communities of canonical leukocyte phenotypes revealed a monocyte-driven response to acute infection, with the greatest expansions in "intermediate" CD14++CD16+ monocytes and an activated subpopulation of CD14+ monocytes. Increases in acute-phase CHIKV envelope protein E2 expression were highest for monocytes and dendritic cells. Serum cytokine measurements confirmed significant acute-phase upregulation of monocyte chemoattractants. Distinct transcriptomic signatures were associated with infection timepoint, as well as convalescent-phase anti-CHIKV antibody titer, acute-phase viremia, and symptom severity. We present a multiscale network that summarizes all observed modulations across cellular and transcriptomic levels and their interactions with clinical outcomes, providing a uniquely global view of the biomolecular landscape of human CHIKV infection.

Characterization of the immune response following in vitro mayaro and chikungunya viruses (Alphavirus, Togaviridae) infection of mononuclear cells

Two Alphaviruses stand out for their clinical importance in Brazil: chikungunya (CHIKV) and mayaro (MAYV) viruses. Few studies exist on the mechanisms of the immune response after infection by these viruses and neither a treatment nor a vaccine for these pathogens are available. Although their infection does not have a high mortality rate, they can lead to a joint involvement that can persist for months. The aims of this work were the study of the mechanisms of antiviral immune response following in vitro (U937 cells) infection with these viruses; to investigate the characteristics of the infection by these viruses; and to determine possible molecular targets that could serve as antiviral therapies against these pathogens. Several genes were modulated after infection by these viruses, and the three antiviral detection and response pathways were activated (Toll-like, RIG-I and NOD-like). Eotaxin and IL-6 were induced in all experiments. The cellular immune response profile found for each virus was different, with CHIKV activating primarily an inflammatory response (Th1 and Th17) and MAYV inducing a regulatory/suppressive response, an important feature to contain the inflammation resulting from infection. The data acquired by this study could provide an explanation why CHIKV infections, due to activation of the inflammatory response, are more clinically relevant than MAYV infections, which generates mostly an anti-inflammatory response after infection.

Immunomodulatory drug methotrexate used to treat patients with chronic inflammatory rheumatisms post-chikungunya does not impair the synovial antiviral and bone repair responses

Chikungunya virus (CHIKV) is a mosquito-transmitted RNA alphavirus causing major outbreaks of infectious chronic inflammatory rheumatisms (CIR). Recently, methotrexate (MTX), a disease modifying anti-rheumatic drug has been used successfully to treat patients suffering from rheumatoid-like arthritis post-CHIK but its immunomodulatory activity in the context of viral persistence has been a matter of concerns. We herein used a model of primary human synovial fibroblasts (HSF) and the synthetic molecule polyriboinosinic:polyribocytidylic acid (PIC) to mimic chronic infectious settings in the joints of CHIKV infected patients. The innate antiviral immune and inflammatory responses were investigated in response to MTX used at the therapeutic concentration of 1 μM. We found that MTX did not affect cellular viability as indicated by the LDH release assay. By quantitative RT-PCR, we observed that HSF responded robustly to PIC by increasing ISG15 and IFNβ mRNA levels. Furthermore, PIC upregulated the mRNA expression of two of the major pattern recognition receptors, RIG-I and MDA5 involved in the innate immune detection of viral RNA. MTX did not impact the antiviral response of PIC on ISG15, IFNβ, RIG-I and MDA5 mRNA expressions. MTX alone or combined with PIC did not affect the expression of proinflammatory CCL2 and CXCL8 chemokines. PIC strongly upregulated the mRNA and protein expression of osteoclastogenic factors (IL-6, GM-CSF but not RANKL). Critically, MTX treatment alone or combined with PIC did not affect the expression of all three tested osteoclastogenic cytokines. We found that MTX alone did not increase the capacity of CHIKV to infect and replicate in HSF. In conclusion, our study argues for a beneficial effect of MTX to treat CIR post-CHIKV given that it does not critically impact the antiviral, the proinflammatory and the bone tissue remodeling responses of synovial cells.

Chikungunya is a mosquito-borne virus (CHIKV) and has been incriminated in the development of arthralgia (pain of the joint) and arthritis particularly in elderly patients. Methotrexate (MTX) has been used widely to effectively treat these chronic rheumatic symptoms. Using a model of primary human joint fibroblasts (HSF), we investigated the capacity of the MTX immunosuppressive drug to affect the immune antiviral and inflammatory responses essential to clear the virus while allowing bone tissue repair. This study is important given that CHIKV and its RNA were shown to persist in the joint for months to years post infection and leading to injuries through ill-characterized mechanisms. The molecule PIC was used to mimic the effect of viral RNA. Interestingly, we found that MTX did not affect the expression of several proinflammatory and bone repair factors by HSF. Remarkably, MTX did not also impair the antiviral response of synovial fibroblasts. Our study revealed for the first time that MTX treatment should be considered as safe even in the context of viral persistence associated with chronic inflammation. MTX will not affect the capacity of the synovial tissue to maintain antiviral mechanism, to control inflammation and to promote bone tissue repair.

Chikungunya fever: a threat to global public health

Chikungunya fever is an emerging arbovirus infection, representing a serious public health problem. Its etiological agent is the Chikungunya virus (CHIKV). Transmission of this virus is mainly vector by mosquitoes of the genus Aedes, although transmission by blood transfusions and vertical transmission has also been reported. The disease presents high morbidity caused mainly by the arthralgia and arthritis generated. Cardiovascular and neurological manifestations have also been reported. The severity of the infection seems to be directly associated with the action of the virus, but also with the decompensation of preexisting comorbidities. Currently, there are no therapeutic products neither vaccines licensed to the infection CHIKV control, although several vaccine candidates are being evaluated and human polyvalent immunoglobulins anti-CHIKV had been tested. Antibodies can protect against the infection, but in sub-neutralizing concentrations can augment virus infection and exacerbate disease severity. So, the prevention still depends on the use of personal protection measures and vector control, which are only minimally effective.

Occurrence of Chronic Stage Chikungunya in the General Population of Martinique during the First 2014 Epidemic: A Prospective Epidemiological Study

Chronic stage chikungunya (CHIK), defined by persisting symptoms more than 3 months after initial diagnosis of acute infection, is frequent. However, its burden and impact have rarely been described prospectively in a general population during an ongoing epidemic in the Caribbean. From January 2014 to January 2015, a severe CHIK outbreak occurred in Martinique. Our objective was to describe epidemiological characteristics and outcomes of chronic stage CHIK in its local population. Participants, clinically diagnosed with probable CHIK infection, were included prospectively by general practitioners during the epidemic's peak from April to October 2014. All identified cases benefited from a follow-up phone call 3 months or more after initial diagnosis during which they were interrogated about persisting clinical signs, past and ongoing treatment, and quality of life. Five hundred and nine subjects participated in the study. Mean age at initial diagnosis was 43.2 ± 23.6 years with a female-male ratio of 1.98. Two hundred participants (39.3%) had probable chronic stage CHIK: 98.5% still experienced pain at least 3 months after acute infection, with 84.3% of reported joint pains; 21.2% were woken up by the pain; 47.2% felt depressed/anxious; and 31.3% experienced memory/concentration disorders. Resumption of daily activity and work was complicated for 55.8% and 36.2% of cases. Persistent impact on morbidity, health outcomes, psychological, and economic aspects further underline the crucial role of community-based medicine and the necessity of an evidence-based multidisciplinary approach toward chronic stage CHIK identification, management, and follow-up in this particular world region.

Chikungunya Arthritis: Implications of Acute and Chronic Inflammation Mechanisms on Disease Management

In the past decade, arboviruses-arthropod-borne viruses-have been the focus of public health institutions worldwide following a spate of devastating outbreaks. Chikungunya virus, an arbovirus that belongs to the alphavirus genus, is a reemerging arthritogenic virus that has caused explosive outbreaks since 2006, notably on Réunion Island, and more recently in the Caribbean, South America, India, and Southeast Asia. The severity of arthritic disease caused by chikungunya virus has prompted public health authorities in affected countries to develop specific guidelines to tackle this pathogen. Chikungunya virus disease manifests first as an acute stage of severe joint inflammation and febrile illness, which later progresses to a chronic stage, during which patients may experience debilitating and persisting articular pain for extended periods. This review aims to provide a broad perspective on current knowledge of chikungunya virus pathogenesis by identifying key clinical and experimental studies that have contributed to our understanding of chikungunya virus to date. In addition, the review explores the practical aspects of treatment and management of both acute and chronic chikungunya virus based on clinical experience during chikungunya virus outbreaks. Finally, recent findings on potential therapeutic solutions-from antiviral agents to immunomodulators-are reviewed to provide both viral immunologists and clinical rheumatologists with a balanced perspective on the nature of a reemerging arboviral disease of significant public health concern, and insight into future therapeutic approaches to better address the treatment and management of chikungunya virus.

Heterogeneity of clinical isolates of chikungunya virus and its impact on the responses of primary human fibroblast-like synoviocytes

Low-passage clinical isolates of chikungunya virus (CHIKV) were found to be a mixture of large- and small-plaque viruses, with small-plaque viruses being the predominant species. To investigate the contribution of plaque variants to the pathology of the joint, primary human fibroblast-like synoviocytes (HFLS) were used. Large- and small-plaque viruses were purified from two clinical isolates, CHIKV-031C and CHIKV-033C, and were designated CHIKV-031L and CHIKV-031S and CHIKV-033L and CHIKV-033S, respectively. The replication efficiencies of these viruses in HFLSs were compared and it was found that CHIKV-031S and CHIKV-033S replicated with the highest efficiency, while the parental clinical isolates had the lowest efficiency. Interestingly, the cytopathic effects (CPE) induced by these viruses correlated with neither the efficiency of replication nor the plaque size. The small-plaque viruses and the clinical isolates induced cell death rapidly, while large-plaque viruses induced slow CPE in which only 50 % of the cells in infected cultures were rounded up and detached on day 5 of infection. The production of proinflammatory cytokines and chemokines from infected HFLSs was evaluated. The results showed that the large-plaque viruses and the clinical isolates, but not small-plaque variants, were potent inducers of IL-6, IL-8 and MCP-1, and were able to migrate monocytes/macrophages efficiently. Sequencing data revealed a number of differences in amino acid sequences between the small- and large-plaque viruses. The results suggest that it is common for clinical isolates of CHIKV to be heterogeneous, while the variants may have distinct roles in the pathology of the joint.

Chikungunya Arthritis Mechanisms in the Americas: A Cross-Sectional Analysis of Chikungunya Arthritis Patients Twenty-Two Months After Infection Demonstrating No Detectable Viral Persistence in Synovial Fluid

OBJECTIVE

To determine if chikungunya virus persists in synovial fluid after infection, potentially acting as a causative mechanism of persistent arthritis.

METHODS

We conducted a cross-sectional study of 38 Colombian participants with clinical chikungunya virus infection during the 2014-2015 epidemic who reported chronic arthritis and 10 location-matched controls without chikungunya virus or arthritis. Prior chikungunya virus infection status was serologically confirmed, and the presence of synovial fluid chikungunya virus, viral RNA, and viral proteins was determined by viral culture, quantitative reverse transcription-polymerase chain reaction (qRT-PCR), and mass spectrometry, respectively. Biomarkers were assessed by multiplex analysis.

RESULTS

Patients with serologically confirmed chikungunya arthritis (33 of 38 [87%]) were predominantly female (82%) and African Colombian (55%) or white Colombian (33%), with moderate disease activity (mean ± SD Disease Activity Score in 28 joints 4.52 ± 0.77) a median of 22 months after infection (interquartile range 21-23 months). Initial symptoms of chikungunya virus infection included joint pain (97%), swelling (97%), stiffness (91%), and fever (91%). The most commonly affected joints were the knees (87%), elbows (76%), wrists (75%), ankles (56%), fingers (56%), and toes (56%). Synovial fluid samples from all patients with chikungunya arthritis were negative for chikungunya virus on qRT-PCR, showed no viral proteins on mass spectrometry, and cultures were negative. Case and control plasma cytokine and chemokine concentrations did not differ significantly.

CONCLUSION

This is one of the largest observational studies involving analysis of the synovial fluid of chikungunya arthritis patients. Synovial fluid analysis revealed no detectable chikungunya virus. This finding suggests that chikungunya virus may cause arthritis through induction of potential host autoimmunity, suggesting a role for immunomodulating agents in the treatment of chikungunya arthritis, or that low-level viral persistence exists in synovial tissue only and is undetectable in synovial fluid.

Increased Proinflammatory Cytokine Levels in Prolonged Arthralgia in Ross River Virus Infection

Ross River virus, a mosquitoborne alphavirus, causes epidemic polyarthritis in Australia and the Pacific region. We analyzed serum cytokine, chemokine, and growth factor levels in travelers returning to Germany from Australia. Serum samples showed elevated concentrations in the acute phase of the illness and, more pronounced, in the long-lasting convalescent phase.

Smoking and female sex as key risk factors associated with severe arthralgia in acute and chronic phases of Chikungunya virus infection

Arthralgia is a potentially incapacitating condition and a persistent symptom in chronic or acute episodes of Chikungunya fever caused by infection with the Chikungunya virus (CHIKV). To the best of our knowledge, there are no reports on risk factors associated with the intensity of arthralgias in typical acute episodes of the disease. Although a number of studies have reported on risk factors associated with the development of the chronic stage of the disease, smoking habits have not been analyzed. Smoking is an interesting factor to consider since it is the main environmental risk factor for the development of rheumatoid arthritis (RA), a similar disease to CHIKV in many aspects. In the present study, 140 patients infected with CHIKV were assessed for risk factors associated with severe arthralgia intensity in the acute phase (pain of 9/10 on the visual analog scale of 0-10) and moderate to severe intensity (according to the Routine Assessment of Patient Index Data 3) 3.5 months after infection in patients that experienced the chronic phase of the disease. Women and smokers were 2- to 3-times more likely to experience severe pain in the acute and chronic stages. Likewise, the presence of severe arthralgia during the acute disease phase resulted in a 4-fold increased risk for entering the chronic phase. Smoking was a more important risk factor in males compared with females. Smoking resulted in a 20-fold increased risk for severe arthralgia during the acute phase in men, as well as a 10-fold increased risk for developing chronic disease with moderate-to-severe pain 3.5 months after the acute stage. The presence of rash, headache, muscular weakness or conjunctivitis in the acute phase, the presence of diabetes and age >40 years were considered significant risk factors due to their influence on illness progression. In conclusion, smoking and female sex were the main risk factors associated with development of severe joint pain in the acute and chronic phases of Chikungunya fever. These risk factors are similar to those associated with the development and severity of RA, possibly because the two diseases share pathophysiological mechanisms, including elevated interleukin-6 levels.

Age has a role in driving host immunopathological response to alphavirus infection

Alphaviruses are a group of arthropod-borne pathogens capable of causing a wide spectrum of clinical symptoms, ranging from milder symptoms like rashes, fever and polyarthralgia, to life-threatening encephalitis. This genus of viruses is prevalent globally, and can infect patients across a wide age range. Interestingly, disease severity of virus-infected patients is wide-ranging. Definitions of the pathogenesis of alphaviruses, as well as the host factors influencing disease severity, remain limited. The innate and adaptive immune systems are important host defences against alphavirus infections. Several reports have highlighted the roles of specific immune subsets in contributing to the immune pathogenesis of these viruses. However, immunosenescence, a gradual deterioration of the immune system brought about by the natural advancement of age, affects the functional roles of these immune subsets. This phenomenon compromises the host's ability to defend against alphavirus infection and pathogenesis. In addition, the lack of maturity in the immune system in newborns and infants also results in more severe disease outcomes. In this review, we will summarize the subtle yet diverse physiological changes in the immune system during aging, and how these changes underlie the differences in disease severity for common alphaviruses.

Differential inhibitory and activating NK cell receptor levels and NK/NKT-like cell functionality in chronic and recovered stages of chikungunya

The role of natural killer (NK; CD3^-CD56⁺)/NKT (CD3⁺CD56⁺)-like cells in chikungunya virus (CHIKV) disease progression/recovery remains unclear. Here, we investigated the expression profiles and function of NK and NKT-like cells from 35 chronic chikungunya patients, 30 recovered individuals, and 69 controls. Percentage of NKT-like cells was low in chronic chikungunya patients. NKp30⁺, CD244⁺, DNAM-1⁺, and NKG2D⁺ NK cell percentages were also lower (MFI and/or percentage), while those of CD94⁺ and NKG2A⁺ NKT-like cells were higher (MFI and/or percentage) in chronic patients than in recovered subjects. IFN-γ and TNF-α expression on NKT-like cells was high in the chronic patients, while only IFN-γ expression on NK cells was high in the recovered individuals. Furthermore, percentage of perforin⁺NK cells was low in the chronic patients. Lower cytotoxic activity was observed in the chronic patients than in the controls. CD107a expression on NK and NKT-like cells post anti-CD94/anti-NKG2A blocking was comparable among the patients and controls. Upregulated inhibitory and downregulated activating NK receptor expressions on NK/NKT-like cells, lower perforin⁺ and CD107a⁺NK cells are likely responsible for inhibiting the NK and NKT-like cell function in the chronic stage of chikungunya. Therefore, deregulation of NKR expression might underlie CHIKV-induced chronicity.

Disruption of the Opal Stop Codon Attenuates Chikungunya Virus-Induced Arthritis and Pathology

Chikungunya virus (CHIKV) is a mosquito-borne alphavirus responsible for several significant outbreaks of debilitating acute and chronic arthritis and arthralgia over the past decade. These include a recent outbreak in the Caribbean islands and the Americas that caused more than 1 million cases of viral arthralgia. Despite the major impact of CHIKV on global health, viral determinants that promote CHIKV-induced disease are incompletely understood. Most CHIKV strains contain a conserved opal stop codon at the end of the viral nsP3 gene. However, CHIKV strains that encode an arginine codon in place of the opal stop codon have been described, and deep-sequencing analysis of a CHIKV isolate from the Caribbean identified both arginine and opal variants within this strain. Therefore, we hypothesized that the introduction of the arginine mutation in place of the opal termination codon may influence CHIKV virulence. We tested this by introducing the arginine mutation into a well-characterized infectious clone of a CHIKV strain from Sri Lanka and designated this virus Opal524R. This mutation did not impair viral replication kinetics in vitro or in vivo. Despite this, the Opal524R virus induced significantly less swelling, inflammation, and damage within the feet and ankles of infected mice. Further, we observed delayed induction of proinflammatory cytokines and chemokines, as well as reduced CD4⁺ T cell and NK cell recruitment compared to those in the parental strain. Therefore, the opal termination codon plays an important role in CHIKV pathogenesis, independently of effects on viral replication.

Chikungunya virus (CHIKV) is a mosquito-borne alphavirus that causes significant outbreaks of viral arthralgia. Studies with CHIKV and other alphaviruses demonstrated that the opal termination codon within nsP3 is highly conserved. However, some strains of CHIKV and other alphaviruses contain mutations in the opal termination codon. These mutations alter the virulence of related alphaviruses in mammalian and mosquito hosts. Here, we report that a clinical isolate of a CHIKV strain from the recent outbreak in the Caribbean islands contains a mixture of viruses encoding either the opal termination codon or an arginine mutation. Mutating the opal stop codon to an arginine residue attenuates CHIKV-induced disease in a mouse model. Compared to infection with the opal-containing parental virus, infection with the arginine mutant causes limited swelling and inflammation, as well as dampened recruitment of immune mediators of pathology, including CD4⁺ T cells and NK cells. We propose that the opal termination codon plays an essential role in the induction of severe CHIKV disease.

Regulation of the chikungunya-virus-induced innate inflammatory response by protein tyrosine phosphatase non-receptor 6 in muscle cells

Chikungunya virus (CHIKV)-induced myositis is an emerging affliction with high incidence globally. Given the essential regulatory role of protein tyrosine phosphatase non-receptor 6 (PTPN6) in virus-induced myositis, the expression of the PTPN6 and TNF-α genes in a CHIKV-infected muscle cell line was examined by quantitative PCR, and the expression of PTPN6 and STAT 3 was examined by immunoblotting. In addition, the effect of PTPN6 siRNA treatment on TNF-α gene expression was assessed. Increased higher expression of PTPN6 and TNF-α, and significant upregulation of TNF-α upon PTPN6 siRNA treatment were observed, suggesting that CHIKV has the ability to induce host PTPN6 gene expression, which may lead to a decreased pro-inflammatory immune response in the host.

Chikungunya vaccines in development

Chikungunya virus has become a global health threat, spreading to the industrial world of Europe and the Americas; no treatment or prophylactic vaccine is available. Since the late 1960s much effort has been put into the development of a vaccine, and several heterogeneous strategies have already been explored. Only two candidates have recently qualified to enter clinical phase II trials, a chikungunya virus-like particle-based vaccine and a recombinant live attenuated measles virus-vectored vaccine.

This review focuses on the current status of vaccine development against chikungunya virus in humans and discusses the diversity of immunization strategies, results of recent human trials and promising vaccine candidates.

Mutations in the E2 Glycoprotein and the 3' Untranslated Region Enhance Chikungunya Virus Virulence in Mice

Chikungunya virus (CHIKV) is a mosquito-transmitted alphavirus that causes debilitating musculoskeletal pain and inflammation and can persist for months to years after acute infection. Although studies of humans and experimentally infected animals suggest that CHIKV infection persists in musculoskeletal tissues, the mechanisms for this remain poorly understood. To evaluate this further, we isolated CHIKV from the serum of persistently infected Rag1 ^-/- mice at day 28. When inoculated into naive wild-type (WT) mice, this persistently circulating CHIKV strain displayed a capacity for earlier dissemination and greater pathogenicity than the parental virus. Sequence analysis revealed a nonsynonymous mutation in the E2 glycoprotein (E2 K200R) and a deletion within the 3' untranslated region (3'-UTR). The introduction of these changes into the parental virus conferred enhanced virulence in mice, although primary tropism for musculoskeletal tissues was maintained. The E2 K200R mutation was largely responsible for enhanced viral dissemination and pathogenicity, although these effects were augmented by the 3'-UTR deletion. Finally, studies with Irf3/Irf7 ^-/- and Ifnar1 ^-/- mice suggest that the E2 K200R mutation enhances viral dissemination from the site of inoculation independently of interferon regulatory factor 3 (IRF3)-, IRF7-, and IFNAR1-mediated responses. As our findings reveal viral determinants of CHIKV dissemination and pathogenicity, their further study should help to elucidate host-virus interactions that determine acute and chronic CHIKV infection.IMPORTANCE CHIKV is a globally spreading, mosquito-transmitted virus that causes debilitating acute and chronic musculoskeletal disease in humans. The viral genetic determinants that dictate the severity of acute and chronic diseases are not understood. To improve our understanding of CHIKV pathogenesis, we evaluated a CHIKV strain isolated from the serum of chronically infected immunocompromised mice. Sequence analysis of this persistent CHIKV strain identified two mutations, an amino acid change in the E2 viral attachment protein and a deletion within the 3'-UTR of the viral genome. We identified roles for these mutations in the enhancement of viral dissemination from the inoculation site and in disease severity. These data improve our understanding of the viral determinants of CHIKV pathogenesis and adaptive changes that occur during viral persistence.

Chikungunya Virus-Induced Arthritis: Role of Host and Viral Factors in the Pathogenesis

Chikungunya virus (CHIKV), a member of Alphavirus genus, is responsible for chikungunya fever (CHIKF), which is characterized by the presence of fever, rash, myalgia, and arthralgia. Reemergence of CHIKV has become a significant public health concern in Asian and African countries and is newly emerging in the Middle East, Pacific, American, and European countries. Cytokines, innate (monocytes, natural killer cells) and adaptive immune response (role of B cells and T cells i.e. CD4⁺ and CD8⁺), and/or viral factors contribute to CHIKV-induced arthritis. Vector factors such as vector competence (that includes extrinsic and intrinsic factors) and effect of genome mutations on viral replication and fitness in mosquitoes are responsible for the spread of virus, although they are not directly responsible for CHIKV-induced arthritis. CHIKV-induced arthritis mimics arthritis by involving joints and a common pattern of leukocyte infiltrate, cytokine production, and complement activation. Successful establishment of CHIKV infection and induction of arthritis depends on its ability to manipulate host cellular processes or host factors. CHIKV-induced joint damage is due to host inflammatory response mediated by macrophages, T cells, and antibodies, as well as the possible persistence of the virus in hidden sites. This review provides insight into mechanisms of CHIKV-induced arthritis. Understanding the pathogenesis of CHIKV-induced arthritis will help in developing novel strategies to predict and prevent the disease in virus-infected subjects and combat the disease, thereby decreasing the worldwide burden of the disease.

Regulatory T cells and IL-10 as modulators of chikungunya disease outcome: a preliminary study

Regulatory T (Treg) cells hold centre stage in regulating the immune responses in most viral infections. However, their involvement in chikungunya infection is unexplored. In the current study, the frequencies and functionality of peripheral Treg and T effector (Teff) cells were assessed during different phases of chikungunya by flow cytometry and in-vitro cytokine assays. Treg cells were also studied in rheumatoid arthritis (RA) patients, whose symptoms closely mimic chronic chikungunya arthritis patients. Frequency of Treg cells was lower in acute and chronic chikungunya arthritis patients than in recovered individuals and controls, and comparable among recovered individuals and controls. Treg/Teff ratio was lower in acute than in chronic chikungunya arthritis patients, recovered individuals and controls. Higher secretion of CHIKV specific IL-10 was observed in recovered individuals than in acute, chronic chikungunya arthritis patients and controls. Frequencies of Treg and Teff cells were higher and Treg/Teff ratio was lower in RA patients than in chronic chikungunya arthritis patients. The results indicate that reduction of Treg cells was associated with ongoing CHIKV infection and normalization of Treg cells with resolution of disease. Contrasting phenotypic data in RA and chronic chikungunya arthritis suggest an altogether different mechanism of Treg-mediated pathology in both arthritis conditions. Overall, our preliminary study, suggesting an association of peripheral Treg cells and IL-10 with recovery from chikungunya, may provide insight into chikungunya disease prognosis and warrants further study.

Management of chikungunya arthritis

Chikungunya fever (CHIKF) is an emerging viral infection that has spread widely, along with its Aedes vectors, throughout the tropics and beyond, causing explosive epidemics of both acute illness and persistent disabling arthritis. There is an urgent need to mitigate the devastating impact of this illness, through vector control, personal protection, and possibly vaccine development. There is also a need to improve treatment for both acute illness and chronic arthritis. In this review, we will review the emergence of CHIK, what is known about pathogenesis and clinical manifestations, and then focus on current understanding of how to treat individual patients, in particular, those who develop chronic arthritis.