Molecular mechanisms involved in the pathogenesis of alphavirus-induced arthritis

Pathogenicity and virulence of O'nyong-nyong virus: A less studied Togaviridae with pandemic potential

O'nyong-nyong virus (ONNV) is a neglected mosquito-borne alphavirus belonging to the Togaviridae family. ONNV is known to be responsible for sporadic outbreaks of acute febrile disease and polyarthralgia in Africa. As climate change increases the geographical range of known and potential new vectors, recent data indicate a possibility for ONNV to spread outside of the African continent and grow into a greater public health concern. In this review, we summarise the current knowledge on ONNV epidemiology, host-pathogen interactions, vector-virus responses, and insights into possible avenues to control risk of further epidemics. In this review, the limited ONNV literature is compared and correlated to other findings on mainly Old World alphaviruses. We highlight and discuss studies that investigate viral and host factors that determine viral-vector specificity, along with important mechanisms that determine severity and disease outcome of ONNV infection.

Development of RT-RPA-based point-of-care tests for epidemic arthritogenic alphaviruses

Chikungunya (CHIKV), o'nyong-nyong (ONNV), and Mayaro (MAYV) viruses are transmitted by mosquitoes and known to cause a debilitating arthritogenic syndrome. These alphaviruses have emerged and re-emerged, leading to outbreaks in tropical and subtropical regions of Asia, South America, and Africa. Despite their prevalence, there persists a critical gap in the availability of sensitive and virus-specific point-of-care (POC) diagnostics. Traditional immunoglobulin-based tests such as enzyme-linked immunosorbent assay (ELISAs) often yield cross-reactive results due to the close genetic relationship between these viruses. Molecular diagnostics such as quantitative polymerase chain reaction (qPCR) offer high sensitivity but are limited by the need for specialized laboratory equipment. Recombinase polymerase amplification (RPA), an isothermal amplification method, is a promising alternative to qPCR, providing rapid results with minimal equipment requirements. Here, we report the development and validation of three virus-specific RPA-based POC tests for CHIKV, ONNV, and MAYV. These tests demonstrated both speed and sensitivity, capable of detecting 10 viral copies within 20 minutes of amplification, without exhibiting cross-reactivity. Furthermore, we evaluated the clinical potential of these tests using serum and tissue samples from CHIKV, ONNV, and MAYV-infected mice, as well as CHIKV-infected human patients. We demonstrate that the RPA amplicons derived from the patient samples can be sequenced, enabling cost-effective molecular epidemiological studies. Our findings highlight the significance of these rapid and specific POC diagnostics in improving the early detection and management of these arboviral infections.

Mayaro virus infection elicits a robust pro-inflammatory and antiviral response in human macrophages

Mayaro virus (MAYV), the etiological agent of Mayaro fever (MAYF), is an emergent arbovirus pathogen belonging to Togaviridae family. MAYF is characterized by high inflammatory component that can cause long-lasting arthralgia that persists for months. Macrophages are viral targets and reservoirs, key components of innate immunity and host response. Given the importance of this pathogen, our aim was to determine the inflammatory and antiviral response of human monocyte-derived macrophages (MDMs) infected with MAYV. First, we established the replication kinetics of the virus. Thereafter, we determined the expression of pattern recognition receptors, NF-ĸB complex, interferons (IFNs), two interleukin 27 (IL27) subunits, IFN-stimulated genes (ISGs), and the production of cytokines/chemokines. We found that human MDMs are susceptible to MAYV infection in vitro, with a peak of viral particles released between 24- and 48-hours post-infection (h.p.i) at MOI 0.5, and between 12 and 24 h.p.i at MOI 1. Interestingly, we observed a significant decline in the production of infectious viral particles at 72 h.p.i that was associated with the induction of antiviral response and high cytotoxic effect of MAYV infection in MDMs. We observed modulation of several genes after MAYV infection, as well, we noted the activation of antiviral detection and response pathways (Toll-like receptors, RIG-I/MDA5, and PKR) at 48 h.p.i but not at 6 h.p.i. Furthermore, MAYV-infected macrophages express high levels of the three types of IFNs and the two IL27 subunits at 48 h.p.i. Moreover, we found higher production of IL6, IL1β, CXCL8/IL8, CCL2, and CCL5 at 48 h.p.i as compared to 6 h.p.i. A robust antiviral response (ISG15, APOBEC3A, IFITM1, and MX2) was observed at 48 but not at 6 h.p.i. The innate and antiviral responses of MAYV-infected MDMs differ at 6 and 48 h.p.i. We conclude that MAYV infection induces robust pro-inflammatory and antiviral responses in human primary macrophages.

Antiviral and Virucidal Activities of Uncaria tomentosa (Cat's Claw) against the Chikungunya Virus

Uncaria tomentosa (UT) is a medicinal plant popularly known as cat's claw belonging to the Rubiaceae family that has been reported to display antiviral and anti-inflammatory activities. The chikungunya virus (CHIKV) outbreaks constitute a Brazilian public health concern. CHIKV infection develops an abrupt onset of fever, usually accompanied by a skin rash, besides incapacitating polyarthralgia. There is no vaccine available or treatment for CHIKV infection. The present study evaluates the hydroalcoholic extract of UT bark as a potential antiviral against CHIKV. The in vitro antiviral activity of the UT extract against the Brazilian CHIKV strain was assessed using quantitative reverse transcription polymerase chain reaction, flow cytometry, and plaque assay. Results obtained demonstrated that UT inhibits CHIKV infection in a dose-dependent manner. At the non-cytotoxic concentration of 100 µg/mL, UT exhibited antiviral activity above 90% as determined by plaque reduction assay, and it reduced the viral cytopathic effect. Similarly, a significant virucidal effect of 100 µg/mL UT was observed after 24 and 48 h post-infection. This is the first report on the antiviral activity of UT against CHIKV infection, and the data presented here suggests UT as a potential antiviral to treat CHIKV infection.

Essential role of the CCL2-CCR2 axis in Mayaro virus-induced disease

Mayaro virus (MAYV) is an emerging arbovirus member of the Togaviridae family and Alphavirus genus. MAYV infection causes an acute febrile illness accompanied by persistent polyarthralgia and myalgia. Understanding the mechanisms involved in arthritis caused by alphaviruses is necessary to develop specific therapies. In this work, we investigated the role of the CCL2/CCR2 axis in the pathogenesis of MAYV-induced disease. For this, wild-type (WT) C57BL/6J and CCR2-/- mice were infected with MAYV subcutaneously and evaluated for disease development. MAYV infection induced an acute inflammatory disease in WT mice. The immune response profile was characterized by an increase in the production of inflammatory mediators, such as IL-6, TNF, and CCL2. Higher levels of CCL2 at the local and systemic levels were followed by the significant recruitment of CCR2+ macrophages and a cellular response orchestrated by these cells. CCR2-/- mice showed an increase in CXCL-1 levels, followed by a replacement of the macrophage inflammatory infiltrate by neutrophils. Additionally, the absence of the CCR2 receptor protected mice from bone loss induced by MAYV. Accordingly, the silencing of CCL2 chemokine expression in vivo and the pharmacological blockade of CCR2 promoted a partial improvement in disease. Cell culture data support the mechanism underlying the bone pathology of MAYV, in which MAYV infection promotes a pro-osteoclastogenic microenvironment mediated by CCL2, IL-6, and TNF, which induces the migration and differentiation of osteoclast precursor cells. Overall, these data contribute to the understanding of the pathophysiology of MAYV infection and the identification future of specific therapeutic targets in MAYV-induced disease.IMPORTANCEThis work demonstrates the role of the CCL2/CCR2 axis in MAYV-induced disease. The infection of wild-type (WT) C57BL/6J and CCR2-/- mice was associated with high levels of CCL2, an important chemoattractant involved in the recruitment of macrophages, the main precursor of osteoclasts. In the absence of the CCR2 receptor, there is a mitigation of macrophage migration to the target organs of infection and protection of these mice against bone loss induced by MAYV infection. Much evidence has shown that host immune response factors contribute significantly to the tissue damage associated with alphavirus infections. Thus, this work highlights molecular and cellular targets involved in the pathogenesis of arthritis triggered by MAYV and identifies novel therapeutic possibilities directed to the host inflammatory response unleashed by MAYV.

Role of macrophages in the onset, maintenance, or control of arthritis caused by alphaviruses

Arthritogenic alphaviruses are mosquito-borne viruses that cause a debilitating rheumatic disease characterized by fever, headache, rash, myalgia, and polyarthralgia with the potential to evolve into a severe and very prolonged illness. Although these viruses have been geographically restricted by vector hosts and reservoirs, recent epidemics have revealed the risks of their spread worldwide. In this review, we aim to discuss the protective and pathological roles of macrophages during the development of arthritis caused by alphaviruses. The progression to the chronic phase of the disease is related to the extension of viral replication and the maintenance of articular inflammation, in which the cellular infiltrate is predominantly composed of macrophages. We explore the possible implications of macrophage polarization to M1/M2 activation phenotypes, drawing a parallel between alphavirus arthritis and rheumatoid arthritis (RA), a chronic inflammatory disease that also affects articular tissues. In RA, it is well established that M1 macrophages contribute to tissue damage and inflammation, while M2 macrophages have a role in cartilage repair, so modulating the M1/M2 macrophage ratio is being considered as a strategy in the treatment of this disease. In the case of alphavirus-induced arthritis, the picture is more complex, as proinflammatory factors derived from M1 macrophages contribute to the antiviral response but cause tissue damage, while M2 macrophages may contribute to tissue repair but impair viral clearance.

Characterization and Involvement of Exosomes Originating from Chikungunya Virus-Infected Epithelial Cells in the Transmission of Infectious Viral Elements

The Chikungunya virus (CHIKV) is a mosquito-borne alphavirus that affects the world's popula-tion with chikungunya disease. Adaptation of the viral life cycle to their host cells' environment is a key step for establishing their infection and pathogenesis. Recently, the accumulating evidence advocates a principal role of extracellular vesicles (EVs), including exosomes, in both the infection and pathogenesis of infectious diseases. However, the participation of exosomes in CHIKV infec-tion and transmission is not well clarified. Here, we demonstrated that the CHIKV RNA and pro-teins were captured in exosomes, which were released by viral-infected epithelial cells. A viral genomic element in the isolated exosomes was infectious to naïve mammalian epithelial cells. The assay of particle size distribution and transmission electron microscopy (TEM) revealed CHIKV-derived exosomes with a size range from 50 to 250 nm. Treatments with RNase A, Triton X-100, and immunoglobulin G antibodies from CHIKV-positive patient plasma indicated that in-fectious viral elements are encompassed inside the exosomes. Interestingly, our viral plaque for-mation also exhibited that infectious viral elements might be securely transmitted to neighboring cells by a secreted exosomal pathway. Taken together, our recent findings emphasize the evidence for a complementary means of CHIKV infection and suggest the role of exosome-mediated CHIKV transmission.

A Review of Omics Studies on Arboviruses: Alphavirus, Orthobunyavirus and Phlebovirus

Since the intricate and complex steps in pathogenesis and host-viral interactions of arthropod-borne viruses or arboviruses are not completely understood, the multi-omics approaches, which encompass proteomics, transcriptomics, genomics and metabolomics network analysis, are of great importance. We have reviewed the omics studies on mosquito-borne viruses of the Togaviridae, Peribuyaviridae and Phenuiviridae families, specifically for Chikungunya, Mayaro, Oropouche and Rift Valley Fever viruses. Omics studies can potentially provide a new perspective on the pathophysiology of arboviruses, contributing to a better comprehension of these diseases and their effects and, hence, provide novel insights for the development of new antiviral drugs or therapies.

Malaria abrogates O'nyong-nyong virus pathologies by restricting virus infection in nonimmune cells

O'nyongnyong virus (ONNV) is a re-emerging alphavirus previously known to be transmitted by main malaria vectors, thus suggesting the possibility of coinfections with arboviruses in co-endemic areas. However, the pathological outcomes of such infections remain unknown. Using murine coinfection models, we demonstrated that a preexisting blood-stage Plasmodium infection suppresses ONNV-induced pathologies. We further showed that suppression of viremia and virus dissemination are dependent on Plasmodium-induced IFNγ and are associated with reduced infection of CD45- cells at the site of virus inoculation. We further proved that treatment with IFNγ or plasma samples from Plasmodium vivax-infected patients containing IFNγ are able to restrict ONNV infection in human fibroblast, synoviocyte, skeletal muscle, and endothelial cell lines. Mechanistically, the role of IFNγ in restricting ONNV infection was confirmed in in vitro infection assays through the generation of an IFNγ receptor 1 α chain (IFNγR1)-deficient cell line.

Human Genetic Host Factors and Its Role in the Pathogenesis of Chikungunya Virus Infection

Chikungunya virus (CHIKV) is an alphavirus from the Togaviridae family that causes acute arthropathy in humans. It is an arthropod-borne virus transmitted initially by the Aedes (Ae) aegypti and after 2006's epidemic in La Reunion by Ae albopictus due to an adaptive mutation of alanine for valine in the position 226 of the E1 glycoprotein genome (A226V). The first isolated cases of CHIKV were reported in Tanzania, however since its arrival to the Western Hemisphere in 2013, the infection became a pandemic. After a mosquito bite from an infected viremic patient the virus replicates eliciting viremia, fever, rash, myalgia, arthralgia, and arthritis. After the acute phase, CHIKV infection can progress to a chronic stage where rheumatic symptoms can last for several months to years. Although there is a great number of studies on the pathogenesis of CHIKV infection not only in humans but also in animal models, there still gaps in the proper understanding of the disease. To this date, it is unknown why a percentage of patients do not develop clinical symptoms despite having been exposed to the virus and developing an adaptive immune response. Also, controversy stills exist on the pathogenesis of chronic joint symptoms. It is known that host immune response to an infectious disease is reflected on patient's symptoms. At the same time, it is now well-established that host genetic variation is an important component of the varied onset, severity, and outcome of infectious disease. It is essential to understand the interaction between the aetiological agent and the host to know the chronic sequelae of the disease. The present review summarizes the current findings on human host genetics and its relationship with immune response in CHIKV infection.

Can presence of HLA type I and II alleles be associated with clinical spectrum of CHIKV infection?

Host immune response and virulence factors are key to disease susceptibility. However, there are no known association studies of human leukocyte antigen (HLA) class I and II alleles with chikungunya virus (CHIKV) infection in the Latin American population. Here, we aimed to identify HLA alleles present in patients with CHIKV infection versus healthy controls as well as the allelic association with the clinical spectrum of the disease. We conducted a cross-sectional analysis of a community cohort and included patients aged 18 years and older with serologically confirmed CHIKV infection. HLA typing of HLA-A, HLA-B, and HLA-DRB1 alleles was performed. Two-by-two tables were used to establish associations between allele presence and clinical characteristics. Data from 65 patients with confirmed CHIKV infection were analyzed for HLA typing. CHIKV infection was significantly associated with the presence of HLA-A*68 [p = .005; odds ratio (OR): 8.90; 95% confidence interval (CI): 1.88-42.13], HLA-B*35 (p = .03; OR: 2.01; 95% CI: 1.06-3.86), HLA-DRB*01 (p <.001; OR: 5.70; 95% CI: 1.95-16.59), HLA-DRB1*04 (p <.001; OR: 7.37; 95% CI: 3.33-16.30), and HLA-DRB1*13 (p = .004; OR: 3.75; 95% CI: 1.50-9.39) alleles in patients versus healthy subjects. A statistically significant relationship was found between the presence of a rash on the face or abdomen and the presence of HLA-DRB1*04 (p = .028; OR: 3.2; 95% CI: 1.11-9.15 and p = .007; OR: 4.33; 95% CI: 1.45-12.88, respectively). Our study demonstrated that, in our cohort, HLA type I and type II alleles are associated with CHIKV infection, and an HLA type II allele is associated with dermatological symptoms. Further research is needed to establish a path for future investigation of genes outside the HLA system to improve knowledge of the pathophysiology of CHIKV infection and its host-pathogen interaction.

Favipiravir Inhibits Mayaro Virus Infection in Mice

Mayaro virus (MAYV) is an emergent alphavirus that causes MAYV fever. It is often associated with debilitating symptoms, particularly arthralgia and myalgia. MAYV infection is becoming a considerable health issue that, unfortunately, lacks a specific antiviral treatment. Favipiravir, a broad-spectrum antiviral drug, has recently been shown to exert anti-MAYV activity in vitro. In the present study, the potential of Favipiravir to inhibit MAYV replication in an in vivo model was evaluated. Immunocompetent mice were orally administrated 300 mg/kg/dose of Favipiravir at pre-, concurrent-, or post-MAYV infection. The results showed a significant reduction in infectious viral particles and viral RNA transcripts in the tissues and blood of the pre- and concurrently treated infected mice. A significant reduction in the presence of both viral RNA transcript and infectious viral particles in the tissue and blood of pre- and concurrently treated infected mice was observed. By contrast, Favipiravir treatment post-MAYV infection did not result in a reduction in viral replication. Interestingly, Favipiravir strongly decreased the blood levels of the liver disease markers aspartate- and alanine aminotransferase in the pre- and concurrently treated MAYV-infected mice. Taken together, these results suggest that Favipiravir is a potent antiviral drug when administered in a timely manner.

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.

A case of SARS-CoV-2-associated arthritis with detection of viral RNA in synovial fluid

Severe acute respiratory distress syndrome-coronavirus-2 (SARS-CoV-2) provokes symptoms ranging from mild viral illness to a systemic inflammatory syndrome with multi-organ failure and has been associated with cases of arthritis. We report a clinical case of SARS-CoV-2 associated arthritis in which analysis of synovial fluid detected SARS-CoV-2 ribonucleic acid.

Mosquito-bite infection of humanized mice with chikungunya virus produces systemic disease with long-term effects

Chikungunya virus (CHIKV) is an emerging, mosquito-borne alphavirus responsible for acute to chronic arthralgias and neuropathies. Although it originated in central Africa, recent reports of disease have come from many parts of the world, including the Americas. While limiting human CHIKV cases through mosquito control has been used, it has not been entirely successful. There are currently no licensed vaccines or treatments specific for CHIKV disease, thus more work is needed to develop effective countermeasures. Current animal research on CHIKV is often not representative of human disease. Most models use CHIKV needle inoculation via unnatural routes to create immediate viremia and localized clinical signs; these methods neglect the natural route of transmission (the mosquito vector bite) and the associated human immune response. Since mosquito saliva has been shown to have a profound effect on viral pathogenesis, we evaluated a novel model of infection that included the natural vector, Aedes species mosquitoes, transmitting CHIKV to mice containing components of the human immune system. Humanized mice infected by 3-6 mosquito bites showed signs of systemic infection, with demonstrable viremia (by qRT-PCR and immunofluorescent antibody assay), mild to moderate clinical signs (by observation, histology, and immunohistochemistry), and immune responses consistent with human infection (by flow cytometry and IgM ELISA). This model should give a better understanding of human CHIKV disease and allow for more realistic evaluations of mechanisms of pathogenesis, prophylaxis, and treatments.

Irinotecan (CPT-11) Canonical Anti-Cancer Drug Can also Modulate Antiviral and Pro-Inflammatory Responses of Primary Human Synovial Fibroblasts

Alphaviruses are a group of arboviruses that generate chronic inflammatory rheumatisms in humans. Currently, no approved vaccines or antiviral therapies are available to prevent or treat alphavirus-induced diseases. The aim of this study was to evaluate the repositioning of the anti-cancer molecule irinotecan as a potential modulator of the antiviral and inflammatory responses of primary human synovial fibroblasts (HSF), the main stromal cells of the joint synovium. HSF were exposed to O’nyong-nyong virus (ONNV) and polyinosinic-polycytidylic acid (PIC) to mimic, respectively, acute and chronic infectious settings. The cytokine IL-1β was used as a major pro-inflammatory cytokine to stimulate HSF. Quantitative RT-PCR analysis revealed that irinotecan at 15 µM was able to amplify the antiviral response (i.e., interferon-stimulated gene expression) of HSF exposed to PIC and reduce the expression of pro-inflammatory genes (CXCL8, IL-6 and COX-2) upon IL-1β treatment. These results were associated with the regulation of the expression of several genes, including those encoding for STAT1, STAT2, p53 and NF-κB. Irinotecan did not modulate these responses in both untreated cells and cells stimulated with ONNV. This suggests that this drug could be therapeutically useful for the treatment of chronic and severe (rather than acute) arthritis due to viruses.

Non-replicating adenovirus based Mayaro virus vaccine elicits protective immune responses and cross protects against other alphaviruses

Mayaro virus (MAYV) is an alphavirus endemic to South and Central America associated with sporadic outbreaks in humans. MAYV infection causes severe joint and muscle pain that can persist for weeks to months. Currently, there are no approved vaccines or therapeutics to prevent MAYV infection or treat the debilitating musculoskeletal inflammatory disease. In the current study, a prophylactic MAYV vaccine expressing the complete viral structural polyprotein was developed based on a non-replicating human adenovirus V (AdV) platform. Vaccination with AdV-MAYV elicited potent neutralizing antibodies that protected WT mice against MAYV challenge by preventing viremia, reducing viral dissemination to tissues and mitigating viral disease. The vaccine also prevented viral-mediated demise in IFN⍺R1-/- mice. Passive transfer of immune serum from vaccinated animals similarly prevented infection and disease in WT mice as well as virus-induced demise of IFN⍺R1-/- mice, indicating that antiviral antibodies are protective. Immunization with AdV-MAYV also generated cross-neutralizing antibodies against two related arthritogenic alphaviruses-chikungunya and Una viruses. These cross-neutralizing antibodies were protective against lethal infection in IFN⍺R1-/- mice following challenge with these heterotypic alphaviruses. These results indicate AdV-MAYV elicits protective immune responses with substantial cross-reactivity and protective efficacy against other arthritogenic alphaviruses. Our findings also highlight the potential for development of a multi-virus targeting vaccine against alphaviruses with endemic and epidemic potential in the Americas.

Cell death pathways and viruses: Role of microRNAs

Viral infections lead to the death of more than a million people each year around the world, both directly and indirectly. Viruses interfere with many cell functions, particularly critical pathways for cell death, by affecting various intracellular mediators. MicroRNAs (miRNAs) are a major example of these mediators because they are involved in many (if not most) cellular mechanisms. Virus-regulated miRNAs have been implicated in three cell death pathways, namely, apoptosis, autophagy, and anoikis. Several molecules (e.g., BECN1 and B cell lymphoma 2 [BCL2] family members) are involved in both apoptosis and autophagy, while activation of anoikis leads to cell death similar to apoptosis. These mechanistic similarities suggest that common regulators, including some miRNAs (e.g., miR-21 and miR-192), are involved in different cell death pathways. Because the balance between cell proliferation and cell death is pivotal to the homeostasis of the human body, miRNAs that regulate cell death pathways have drawn much attention from researchers. miR-21 is regulated by several viruses and can affect both apoptosis and anoikis via modulating various targets, such as PDCD4, PTEN, interleukin (IL)-12, Maspin, and Fas-L. miR-34 can be downregulated by viral infection and has different effects on apoptosis, depending on the type of virus and/or host cell. The present review summarizes the existing knowledge on virus-regulated miRNAs involved in the modulation of cell death pathways. Understanding the mechanisms for virus-mediated regulation of cell death pathways could provide valuable information to improve the diagnosis and treatment of many viral diseases.

Quercetin can reduce viral RNA level of O'nyong-nyong virus and resulting innate immune cytokine responses in cultured human synovial fibroblasts

O’nyong-nyong virus is an alphavirus closely related to chikungunya virus, causing arthralgia, rash and fever. Alphaviruses mainly target synovial fibroblasts and persists in the joints of patients, possibly leading to chronic arthritis. To date, no specific antiviral treatment is available for ONNV infection and induced-inflammation. Primary human synovial fibroblasts cells were used to assess infection by ONNV and the resulting cytokine responses. Phenolics (gallic acid, caffeic acid and chlorogenic acid, curcumin and quercetin) and a curcuminoids-rich extract from turmeric were tested for their antiviral and anti-inflammatory capacities. We showed that infection occurred in HSF cells and increased gene expression and protein secretion of two major proinflammatory CCL-2 and IL-1β markers. In ONNV-infected HSF cells (MOI 1), we found that non-cytotoxic concentrations of phenolics (10 µM) reduced the level of viral RNA (E1, E2, nsP1, nsP2) and downregulated CCL-2 and IL-1β expression and secretion. These results highlighted the high value of the flavonol quercetin to reduce viral RNA levels and inflammatory status induced by ONNV in HSF cells.

Sleep Disturbances are a Significant Predictor of Chikungunya Arthritis Flare Severity

OBJECTIVE

The primary objective of this research was to explore the link between sleep and flare pain associated with chikungunya virus (CHIKV) infection. The secondary objective was to investigate if cytokines and T regulatory (Treg) cells have an influence on this relationship.

METHODS

A cross-sectional study was performed using data collected in Barranquilla, Colombia, which enrolled patients with and without chronic arthritis with a history of chikungunya infection. Flare severity was measured by a version of the Outcome Measures in Rheumatoid Arthritis Clinical Trials (OMERACT) flare questionnaire adapted for CHIKV arthritis, including metrics for pain, difficulty with physical activity, fatigue, stiffness and difficulty maintaining social activities due to arthritis that contribute to flare severity. In addition, four sleep disturbance items, five inflammatory cytokine levels, four anti-inflammatory cytokine levels, and six Treg levels were measured. Then, multivariable linear regression models were used to test the direct and indirect effects of flare-pain on sleep disturbance, and to determine whether this relationship was mediated by cytokines or Tregs. Finally, the SAS CALIS procedure was used to test path models showing possible causal effects with mediators and confounds.

RESULTS

The analysis showed that sleep disturbance is positively correlated with CHIKV arthritis flare pain, and that it is a significant predictor of flare severity after adjusting for demographic variables, cytokine, and T cell levels. Further, neither T cells nor cytokines mediate the pain/sleep relationship in CHIKV arthritis.

CONCLUSION

There is a strong association between sleep disturbance and arthritis flare pain and severity; however, this relationship is not mediated by cytokines or T cells. Since this study is unable to determine causation, further research is needed to determine the mechanism underlying the relationship between sleep disturbances and CHIKV arthritis flares.

Ferritin, Erythrocyte Sedimentation Rate, and C-Reactive Protein Level in Patients with Chikungunya-Induced Chronic Polyarthritis

Chikungunya virus (CHIKV) is a global emergent arthritogenic alphavirus transmitted by anthropophilic Stegomyia mosquitoes. Chikungunya fever may evolve to chronic arthralgia in 57-80% of infected patients. This study was developed to identify possibly fast, simple low-cost biomarkers to monitor chronic CHIKV-induced articular disease. Between 2017 and 2018, we analyzed clinical data of patients meeting the criteria established by standard protocols to define chronic chikungunya articular disease. Patients were classified according to the disease activity scores, inflammatory biomarkers (erythrocyte sedimentation rate [ESR], ferritin, and C-reactive protein [CRP] serum), positive rheumatoid factor, comorbidities, smoking, and previous use of corticosteroids determined before beginning therapy. Of 106 patients, 98 (92.5%) were women with mean age of 52 ± 13 years, 6.8 ± 4.4 months of illness duration at the first medical appointment, and 6.7 ± 4.5 affected joints. Mean ESR (26 ± 19), CRP (2.6 ± 3.6), and stratified ferritin (144 ± 115) levels were normal according to reference values. There was no significance in comparing the levels of inflammatory biomarkers and the additional variables analyzed in the presence of moderate chronic joint disease in the study population. However, we identified a negative correlation between disease activity measures and duration of disease at the first medical evaluation after initial infection (P < 0.001), corroborating data observed in the literature.

Chronic Joint Pain 3 Years after Chikungunya Virus Infection Largely Characterized by Relapsing-remitting Symptoms

OBJECTIVE

To determine the frequency of chronic joint pain and stiffness 3 years after infection with chikungunya virus (CHIKV) in a Latin American cohort.

METHODS

A cross-sectional followup of 120 patients from an initial cohort of 500 patients who reported joint pain 2 years after infection from the Atlántico Department, Colombia. Patients were clinically diagnosed as having CHIKV during the 2014-2015 epidemic, and baseline and followup symptoms at 40 months were evaluated in serologically confirmed cases.

RESULTS

Of the initial 500 patients enrolled in the study, 482 had serologically confirmed chikungunya infection. From this group, 123 patients reported joint pain 20 months after infection, and 54% of those patients reported continued joint pain 40 months after infection. Therefore, 1 out of every 8 people who tested serologically positive for CHIKV infection had persistent joint pain 3 years after infection. Participants who followed up in person were predominantly adult (mean ± SD age 51 ± 14 yrs) and female (86%). The most common type of pain reported in these patients at 40 months post-infection was pain with periods of relief and subsequent reoccurrence, and over 75% reported stiffness after immobility, with 39% experiencing morning stiffness.

CONCLUSION

To our knowledge, this is the first report to describe persistent joint pain and stiffness 40 months after viral infection. The high frequency of chronic disease highlights the need to develop prevention and treatment methods. Further studies should be conducted to understand the similarities between post-chikungunya joint pain and rheumatoid arthritis.

Reduced Duration of Postchikungunya Musculoskeletal Pain in Rheumatological Patients Treated with Biologicals

Chikungunya fever (CHIK) has caused important epidemic outbreaks in the Americas, with musculoskeletal involvement being the main manifestation, causing chronic symptoms in half of the affected patients. This study was performed to evaluate the clinical course of the infection in 168 patients with autoimmune inflammatory disease using biological disease-modifying antirheumatic drugs (bDMARDs), comparing this group with 56 household controls. Anti-CHIKV IgG serology was positive in 42 (25%) of the patients in the bDMARD group and in 15 (27%) of the controls (p=0.79). Of those with positive serology, 32 (76%) and 14 (93%) were symptomatic among subjects in the bDMARD and control groups, respectively (p=0.87). Persistence of musculoskeletal symptoms for more than three months occurred in 64% of the patients in the control group and only in 28% in the bDMARD group (p=0.021), maintaining a statistically significant difference only for users of anti-TNF. This study found that patients affected by chikungunya fever using bDMARDs did not present severe forms or complications in the acute phase of the disease, and patients using anti-TNF biologicals had a lower frequency of chronic joint symptoms than the household controls. This favorable outcome may be related to the cytokine blockade, with a reduction in the inflammatory response and joint damage.

A possible role for autoimmunity through molecular mimicry in alphavirus mediated arthritis

Alphaviral infections are foremost in causing debilitating clinical outcomes in humans characterized by rheumatic arthritis like conditions. Though the presence of virus in joints and associated inflammation has been implicated as one of the reasons for the acute and chronic polyarthritis post alphaviral infections, the basis for rheumatic like outcomes is not clear. Through an in silico analysis, we have investigated the possibility of an autoimmune process mediated through molecular mimicry in alphaviral infection induced pathogenicity. Interestingly, sequence alignment of the structural polyproteins belonging to arthritogenic alphaviruses revealed conserved regions which share homology with human proteins implicated in rheumatoid arthritis (RA). These conserved regions were predicted to exhibit binding to HLA class II alleles, showcasing their potential to incite T cell help. Molecular docking of the viral peptide and the corresponding homologous region in the human protein onto HLA-DRB1 revealed strong similarities in their binding patterns. Linear and conformational B cell epitope prediction analyses showed that these potential mimics have high propensity to elicit an efficient B cell response. We thus propose that the origin of polyarthritis post-arthritogenic alphaviral infections may also be mediated through a hitherto unknown autoimmune response due to the presence of cross-reactive epitopes between viral and human proteins.

Mayaro Virus Induction of Oxidative Stress is Associated With Liver Pathology in a Non-Lethal Mouse Model

Mayaro virus (MAYV) causes Mayaro fever in humans, a self-limiting acute disease, with persistent arthralgia and arthritis. Although MAYV has a remerging potential, its pathogenic mechanisms remain unclear. Here, we characterized a model of MAYV infection in 3-4-week BALB/c mice. We investigated whether the liver acts as a site of viral replication and if the infection could cause histopathological alterations and an imbalance in redox homeostasis, culminating with oxidative stress. MAYV-infected mice revealed lower weight gain; however, the disease was self-resolving. High virus titre, neutralizing antibodies, and increased levels of aspartate and alanine aminotransferases were detected in the serum. Infectious viral particles were recovered in the liver of infected animals and the histological examination of liver tissues revealed significant increase in the inflammatory infiltrate. MAYV induced significant oxidative stress in the liver of infected animals, as well as a deregulation of enzymatic antioxidant components. Collectively, this is the first study to report that oxidative stress occurs in MAYV infection in vivo, and that it may be crucial in virus pathogenesis. Future studies are warranted to address the alternative therapeutic strategies for Mayaro fever, such as those based on antioxidant compounds.

Mayaro Virus Replication Restriction and Induction of Muscular Inflammation in Mice Are Dependent on Age, Type-I Interferon Response, and Adaptive Immunity

Mayaro virus (MAYV) is an emergent arbovirus first described in forest regions of the American continent, with recent and increasing notification of urban area circulation. Similar to Chikungunya (CHIKV) and other arthritogenic Alphavirus, MAYV-induced disease shows a high prevalence of persistent arthralgia, and myalgia. Despite this, knowledge regarding pathogenesis and characteristics of host immune response of MAYV infections are still limited. Here, using different ages of wild-type (WT), adult Type I Interferon receptor deficient (IFNAR^-/-), and adult recombination activation gene-1 deficient (RAG^-/-) mice, we have investigated the dependence of age, innate and adaptive immunity for the control of MAYV replication, tissue damage, and inflammation in mice. We have found that MAYV induces clinical signal and replicates in young WT mice, which gain the ability to restrict MAYV replication with aging. In addition, we observed that mice age and type I interferon response are related to restriction of MAYV infection and muscular inflammation in mice. Moreover, MAYV continues to replicate persistently in RAG^-/- mice, being detected at blood and tissues 40 days post infection, indicating that adaptive immunity is essential to MAYV clearance. Despite chronic replication, infected adult RAG^-/- mice did not develop an apparent signal of muscle damage in early and late infection. On the other hand, MAYV infection in young WT and adult IFNAR-/- mice triggers an increase in the expression of pro-inflammatory mediators, such as TNF, IL-6, KC, IL-1β, MCP-1, and RANTES, in muscle tissue, and decreases TGF-β expression, that were not significantly modulated in adult WT and RAG^-/- mice. Taken together, our data demonstrated that age, innate and adaptive immunity are important to restrict MAYV replication and that adaptive immunity is also involved in MAYV-induced tissue damage. These results contribute to the comprehension of MAYV pathogenesis, and describe translational mice models for further studies of MAYV infection, vaccine tests, and therapeutic strategies against this virus.

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.

Identification of a novel alphavirus related to the encephalitis complexes circulating in southern Brazil

In early 2017, an outbreak caused by an unknown and supposedly viral agent in the Marilena region of southern Brazil was investigated. Since the etiological agent causing the outbreak was not identified from human samples, mosquitoes from this region were collected. Three out of 121 mosquito pools collected from the region tested positive for alphavirus in molecular tests. Next generation sequencing results revealed the presence of a novel alphavirus, tentatively named here as Caainguá virus (CAAV). DNA barcoding analyses indicated that different species of Culex are hosts for CAAV. This new virus was basal to the New World encephalitic alphaviruses in a comprehensive and robust phylogenetic approach using complete genomes. Viral particles were observed in the cytosol and inside of intracellular compartments of cells in mosquito-derived cell cultures. Despite being noninfectious in vertebrate derived cell cultures, primary culturing of CAAV in human mononuclear cells suggests monocytes and lymphocytes as CAAV targets. However, the epidemiological link of CAAV on the human outbreak should be further explored.

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.

In Vivo Evaluation of Withania somnifera-Based Indian Traditional Formulation ( Amukkara Choornam), Against Chikungunya Virus-Induced Morbidity and Arthralgia

Chikungunya viral fever results in extreme morbidity and arthralgia in affected individuals. Currently, modern medicines providing symptomatic relief for the acute febrile phase and the chronic arthritic phase are only options available. Traditional Indian medical system, however, uses specific formulations for treatment of this infection; one such polyherbal formulation used to treat the postpyretic phase of chikungunya is amukkara choornam. The current study was undertaken to study the efficacy of amukkara choornam in the treatment of chikungunya in C57BL/6J mice. The formulation when administered to chikungunya-infected mice relieved morbidity and joint swelling. Analysis of virus clearance in brain and joint tissues on formulation treatment revealed a direct correlation of viral load in brain to morbidity during infection; likewise, joint swelling receded prior to complete viral clearance explaining possible immunomodulatory effect of amukkara choornam. This study provides insight into the possible mode of action of amukkara choornam during chikungunya.

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.

Mayaro: an emerging viral threat?

Mayaro virus (MAYV), an enveloped RNA virus, belongs to the Togaviridae family and Alphavirus genus. This arthropod-borne virus (Arbovirus) is similar to Chikungunya (CHIKV), Dengue (DENV), and Zika virus (ZIKV). The term “ChikDenMaZika syndrome” has been coined for clinically suspected arboviruses, which have arisen as a consequence of the high viral burden, viral co-infection, and co-circulation in South America. In most cases, MAYV disease is nonspecific, mild, and self-limited. Fever, arthralgia, and maculopapular rash are among the most common symptoms described, being largely indistinguishable from those caused by other arboviruses. However, severe manifestations of the infection have been reported, such as chronic polyarthritis, neurological complications, hemorrhage, myocarditis, and even death. Currently, there are no specific commercial tools for the diagnosis of MAYV, and the use of serological methods can be affected by cross-reactivity and the window period. A diagnosis based on clinical and epidemiological data alone is still premature. Therefore, new entomological research is warranted, and new highly specific molecular diagnostic methods should be developed. This comprehensive review is intended to encourage public health authorities and scientific communities to actively work on diagnosing, preventing, and treating MAYV infection.

Monocytes and Macrophages as Viral Targets and Reservoirs

Viruses manipulate cell biology to utilize monocytes/macrophages as vessels for dissemination, long-term persistence within tissues and virus replication. Viruses enter cells through endocytosis, phagocytosis, macropinocytosis or membrane fusion. These processes play important roles in the mechanisms contributing to the pathogenesis of these agents and in establishing viral genome persistence and latency. Upon viral infection, monocytes respond with an elevated expression of proinflammatory signalling molecules and antiviral responses, as is shown in the case of the influenza, Chikungunya, human herpes and Zika viruses. Human immunodeficiency virus initiates acute inflammation on site during the early stages of infection but there is a shift of M1 to M2 at the later stages of infection. Cytomegalovirus creates a balance between pro- and anti-inflammatory processes by inducing a specific phenotype within the M1/M2 continuum. Despite facilitating inflammation, infected macrophages generally display abolished apoptosis and restricted cytopathic effect, which sustains the virus production. The majority of viruses discussed in this review employ monocytes/macrophages as a repository but certain viruses use these cells for productive replication. This review focuses on viral adaptations to enter monocytes/macrophages, immune escape, reprogramming of infected cells and the response of the host cells.

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.

Macrophages as target cells for Mayaro virus infection: involvement of reactive oxygen species in the inflammatory response during virus replication

Alphaviruses among the viruses that cause arthritis, consisting in a public health problem worldwide by causing localized outbreaks, as well as large epidemics in humans. Interestingly, while the Old World alphaviruses are arthritogenic, the New World alphaviruses cause encephalitis. One exception is Mayaro virus (MAYV), which circulates exclusively in South America but causes arthralgia and is phylogenetically related to the Old World alphaviruses. Although MAYV-induced arthritis in humans is well documented, the molecular and cellular factors that contribute to its pathogenesis are completely unknown. In this study, we demonstrated for the first time that macrophages, key players in arthritis development, are target cells for MAYV infection, which leads to cell death through apoptosis. We showed that MAYV replication in macrophage induced the expression of TNF, a cytokine that would contribute to pathogenesis of MAYV fever, since TNF promotes an inflammatory profile characteristic of arthritis. We also found a significant increase in the production of reactive oxygen species (ROS) at early times of infection, which coincides with the peak of virus replication and precedes TNF secretion. Treatment of the cells with antioxidant agents just after infection completely abolished TNF secretion, indicating an involvement of ROS in inflammation induced during MAYV infection.

Beyond the Matrix: The Many Non-ECM Ligands for Integrins

The traditional view of integrins portrays these highly conserved cell surface receptors as mediators of cellular attachment to the extracellular matrix (ECM), and to a lesser degree, as coordinators of leukocyte adhesion to the endothelium. These canonical activities are indispensable; however, there is also a wide variety of integrin functions mediated by non-ECM ligands that transcend the traditional roles of integrins. Some of these unorthodox roles involve cell-cell interactions and are engaged to support immune functions such as leukocyte transmigration, recognition of opsonization factors, and stimulation of neutrophil extracellular traps. Other cell-cell interactions mediated by integrins include hematopoietic stem cell and tumor cell homing to target tissues. Integrins also serve as cell-surface receptors for various growth factors, hormones, and small molecules. Interestingly, integrins have also been exploited by a wide variety of organisms including viruses and bacteria to support infectious activities such as cellular adhesion and/or cellular internalization. Additionally, the disruption of integrin function through the use of soluble integrin ligands is a common strategy adopted by several parasites in order to inhibit blood clotting during hematophagy, or by venomous snakes to kill prey. In this review, we strive to go beyond the matrix and summarize non-ECM ligands that interact with integrins in order to highlight these non-traditional functions of integrins.

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.

A young female presenting with unilateral sacroiliitis following dengue virus infection: a case report

BACKGROUND

Dengue is a common arthropod-borne viral infection in Sri Lanka which is spread by the mosquitos of the genus Aedes. The clinical features of dengue include high-grade fever associated with arthralgia and myalgia. However, dengue virus is not considered an arthritogenic virus. We report a case of a previously healthy young female who presented with imaging-confirmed right-sided sacroiliitis 10 days after developing dengue fever. This is the first reported case that shows a possible link between dengue infection and development of arthritis.

CASE PRESENTATION

A 14-year-old Sri Lankan female presented to our medical unit with right buttock and hip pain of 3 weeks' duration. She had serologically confirmed dengue infection 10 days prior to the onset of buttock pain. A clinical examination revealed features of right sacroiliitis. An X-ray of her sacroiliac joint showed joint space widening and reactive bone changes. Magnetic resonance imaging of her pelvis and sacroiliac joint confirmed the diagnosis of acute sacroiliitis. She had an erythrocyte sedimentation rate of 110 mm first hour with a normal C-reactive protein. Her human leukocyte antigen-B27, rheumatoid factor, antinuclear antibody, chikungunya antibody, hepatitis serology, Brucella serology, and tuberculin skin test were negative. She was treated with nonsteroidal anti-inflammatory drugs and showed gradual improvement.

CONCLUSIONS

After excluding possible causes for sacroiliitis, we postulated that sacroiliitis in the index case could have been caused or triggered by dengue virus infection. However there is a possibility that the sacroiliitis merely coincided with the dengue virus infection. This case illustrates the possibility that dengue virus could have a link with the development of arthritis in the same manner as other arthritogenic viruses; possible mechanisms for this include direct invasion of the synovium and the joint tissue by the virus, immune complex formation and deposition in the joint tissue, and immune dysregulation. Further studies are needed in this field to gain more knowledge, as dengue infection is highly prevalent in Sri Lanka.

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.

Zika, Chikungunya, and Other Emerging Vector-Borne Viral Diseases

Arthropod-borne viruses (arboviruses) have a long history of emerging to infect humans, but during recent decades, they have been spreading more widely and affecting larger populations. This is due to several factors, including increased air travel and uncontrolled mosquito vector populations. Emergence can involve simple spillover from enzootic (wildlife) cycles, as in the case of West Nile virus accompanying geographic expansion into the Americas; secondary amplification in domesticated animals, as seen with Japanese encephalitis, Venezuelan equine encephalitis, and Rift Valley fever viruses; and urbanization, in which humans become the amplification hosts and peridomestic mosquitoes, mainly Aedes aegypti, mediate human-to-human transmission. Dengue, yellow fever, chikungunya, and Zika viruses have undergone such urban emergence. We focus mainly on the latter two, which are recent arrivals in the Western Hemisphere. We also discuss a few other viruses with the potential to emerge through all of these mechanisms.

Recommendations of the Brazilian Society of Rheumatology for diagnosis and treatment of Chikungunya fever. Part 1 - Diagnosis and special situations

Chikungunya fever has become a relevant public health problem in countries where epidemics occur. Until 2013, only imported cases occurred in the Americas, but in October of that year, the first cases were reported in Saint Marin island in the Caribbean. The first autochthonous cases were confirmed in Brazil in September 2014; until epidemiological week 37 of 2016, 236,287 probable cases of infection with Chikungunya virus had been registered, 116,523 of which had serological confirmation. Environmental changes caused by humans, disorderly urban growth and an ever-increasing number of international travelers were described as the factors responsible for the emergence of large-scale epidemics. Clinically characterized by fever and joint pain in the acute stage, approximately half of patients progress to the chronic stage (beyond 3 months), which is accompanied by persistent and disabling pain. The aim of the present study was to formulate recommendations for the diagnosis and treatment of Chikungunya fever in Brazil. A literature review was performed in the MEDLINE, SciELO and PubMed databases to ground the decisions for recommendations. The degree of concordance among experts was established through the Delphi method, involving 2 in-person meetings and several online voting rounds. In total, 25 recommendations were formulated and divided into 3 thematic groups: (1) clinical, laboratory and imaging diagnosis; (2) special situations; and (3) treatment. The first 2 themes are presented in part 1, and treatment is presented in part 2.

Clinical manifestations of chikungunya among university professors and staff in Santo Domingo, the Dominican Republic

Objective.

To further characterize chikungunya virus infection and its associated clinical manifestations, using a sample of university professors and staff in Santo Domingo, the Dominican Republic.

Methods.

A cross-sectional study with quota sampling by department was performed to obtain a convenience sample of professors (n = 736) and staff (n = 499) at the Universidad Autónoma de Santo Domingo. Surveys were used to collect demographic and infection data during the fall term of 2014. Univariate and bivariate analyses were carried out to quantify infection and clinical manifestation prevalence and to assess relationships of these outcomes with age, sex, and acute phase duration.

Results.

Of 1 236 participants, 49% reported infection (professors = 41%; staff = 61%). Of these, 53% also reported the presence of chronic effects, largely arthralgia (48%). Significant relationships were observed between reported infection and sex (P = 0.023), age (P < 0.001), and occupation (P < 0.001). More headache (P = 0.008) and edema (P < 0.001) in females, more headache (P = 0.005) in younger subjects, and more myalgia (P = 0.006) in those with longer acute symptoms were found. Additionally, more chronic arthralgia (P < 0.001; P = 0.003) and chronic edema (P < 0.001; P = 0.001) in females and older subjects, and more chronic myalgia (P = 0.041) and chronic edema (P = 0.037) in those with longer acute symptoms were observed.

Conclusions.

To the authors knowledge, this is the first population-based chikungunya prevalence study in the Dominican Republic, and the first to explore clinical manifestations in a university setting. The findings reflect results from studies following the 2005 – 2006 Reunion Island outbreak: prevalence of infection and chronic arthralgia, as well as associations with sex, age, and acute intensity. Longitudinal research can provide further insight into these effects.

Pharmacologic management of pain in patients with Chikungunya: a guideline

From the arrival of Chikungunya virus in the Americas in 2013 until March 2016, approximately two million cases of the disease have been reported. In Brazil, the virus was identified in 2014 and thousands of people have been affected. The disease has high attack rates, infecting 50% of a population within a few months. Approximately 50% of infected people develop chronic symptoms lasting for months or years. Joint involvement is the main clinical manifestation of Chikungunya. It is characterized by swelling and intense pain that is poorly responsive to analgesics, both in the acute and chronic phase of the disease. This significantly compromises quality of life and may have immeasurable psychosocial and economic repercussions, constituting therefore, a serious public health problem requiring a targeted approach. Physicians are often not familiar with how to approach the management of pain, frequently prescribing limited analgesics, such as dipyrone, in sub-therapeutic doses. In addition, there are few published studies or guidelines on the approach to the treatment of pain in patients with Chikungunya. Some groups of specialists from different fields have thus developed a protocol for the pharmacologic treatment of Chikungunya-associated acute and chronic joint pain; this will be presented in this review.

Tropical arthritogenic alphaviruses

Tropical alphaviruses have special tropism for bone and joint tissue. Patients can develop chronic rheumatic disorders similar to rheumatoid arthritis and ankylosing spondylitis. The prototype is Chikungunya virus, although other lesser known viruses in our environment such as Sindbis, Ross River, Mayaro, O'nyong nyong and Barmah Forest viruses have the potential to be sped through vectors and cause chronic rheumatic disease. International population movements have increased the numbers of patients diagnosed with these tropical viruses in areas in which they are not endemic. Since they can leave persistent symptoms and affect the quality of life of the patients, it is important that we be aware of them. Changes in ecosystems have favored the expansion of competent mosquitoes, making fears of local transmission in southern Europe a reality. The objective of this review is to provide a clinical approach to the different arthritogenic tropical alphaviruses, especially those in which chronic rheumatic disease is more frequent.