The impact of arthritogenic viruses in oral tissues

Arthritis and periodontitis are inflammatory diseases that share several immunopathogenic features. The expansion in the study of virus-induced arthritis has shed light on how this condition could impact other parts of the human body, including the mouth. Viral arthritis is an inflammatory joint disease caused by several viruses, most notably the alphaviruses Chikungunya virus (CHIKV), Sindbis virus (SINV), Ross River virus (RRV), Mayaro virus (MAYV), and O'nyong'nyong virus (ONNV). These viruses can induce an upsurge of matrix metalloproteinases and immune-inflammatory mediators such as Interleukin-6 (IL6), IL-1β, tumor necrosis factor, chemokine ligand 2, and receptor activator of nuclear factor kappa-B ligand in the joint and serum of infected individuals. This can lead to the influx of inflammatory cells to the joints and associated muscles as well as osteoclast activation and differentiation, culminating in clinical signs of swelling, pain, and bone resorption. Moreover, several data indicate that these viral infections can affect other sites of the body, including the mouth. The human oral cavity is a rich and diverse microbial ecosystem, and viral infection can disrupt the balance of microbial species, causing local dysbiosis. Such events can result in oral mucosal damage and gingival bleeding, which are indicative of periodontitis. Additionally, infection by RRV, CHIKV, SINV, MAYV, or ONNV can trigger the formation of osteoclasts and upregulate pro-osteoclastogenic inflammatory mediators, interfering with osteoclast activation. As a result, these viruses may be linked to systemic conditions, including oral manifestations. Therefore, this review focuses on the involvement of alphavirus infections in joint and oral health, acting as potential agents associated with oral mucosal inflammation and alveolar bone loss. The findings of this review demonstrate how alphavirus infections could be linked to the comorbidity between arthritis and periodontitis and may provide a better understanding of potential therapeutic management for both conditions.

Characterization of Systemic Disease Development and Paw Inflammation in a Susceptible Mouse Model of Mayaro Virus Infection and Validation Using X-ray Synchrotron Microtomography

Mayaro virus (MAYV) is an emerging arthropod-borne virus endemic in Latin America and the causative agent of arthritogenic febrile disease. Mayaro fever is poorly understood; thus, we established an in vivo model of infection in susceptible type-I interferon receptor-deficient mice (IFNAR-/-) to characterize the disease. MAYV inoculations in the hind paws of IFNAR-/- mice result in visible paw inflammation, evolve into a disseminated infection and involve the activation of immune responses and inflammation. The histological analysis of inflamed paws indicated edema at the dermis and between muscle fibers and ligaments. Paw edema affected multiple tissues and was associated with MAYV replication, the local production of CXCL1 and the recruitment of granulocytes and mononuclear leukocytes to muscle. We developed a semi-automated X-ray microtomography method to visualize both soft tissue and bone, allowing for the quantification of MAYV-induced paw edema in 3D with a voxel size of 69 µm3. The results confirmed early edema onset and spreading through multiple tissues in inoculated paws. In conclusion, we detailed features of MAYV-induced systemic disease and the manifestation of paw edema in a mouse model extensively used to study infection with alphaviruses. The participation of lymphocytes and neutrophils and expression of CXCL1 are key features in both systemic and local manifestations of MAYV disease.

Anti-Alphaviral Alkaloids: Focus on Some Isoquinolines, Indoles and Quinolizidines

The discovery and the development of safe and efficient therapeutics against arthritogenic alphaviruses (e.g., chikungunya virus) remain a continuous challenge. Alkaloids are structurally diverse and naturally occurring compounds in plants, with a wide range of biological activities including beneficial effects against prominent pathogenic viruses and inflammation. In this short review, we discuss the effects of some alkaloids of three biologically relevant structural classes (isoquinolines, indoles and quinolizidines). Based on various experimental models (viral infections and chronic diseases), we highlight the immunomodulatory effects of these alkaloids. The data established the capacity of these alkaloids to interfere in host antiviral and inflammatory responses through key components (antiviral interferon response, ROS production, inflammatory signaling pathways and pro- and anti-inflammatory cytokines production) also involved in alphavirus infection and resulting inflammation. Thus, these data may provide a convincing perspective of research for the use of alkaloids as immunomodulators against arthritogenic alphavirus infection and induced inflammation.

Mayaro Virus Infects Human Brain Cells and Induces a Potent Antiviral Response in Human Astrocytes

Mayaro virus (MAYV) and chikungunya virus (CHIKV) are known for their arthrotropism, but accumulating evidence shows that CHIKV infections are occasionally associated with serious neurological complications. However, little is known about the capacity of MAYV to invade the central nervous system (CNS). We show that human neural progenitors (hNPCs), pericytes and astrocytes are susceptible to MAYV infection, resulting in the production of infectious viral particles. In primary astrocytes, MAYV, and to a lesser extent CHIKV, elicited a strong antiviral response, as demonstrated by an increased expression of several interferon-stimulated genes, including ISG15, MX1 and OAS2. Infection with either virus led to an enhanced expression of inflammatory chemokines, such as CCL5, CXCL10 and CXCL11, whereas MAYV induced higher levels of IL-6, IL-12 and IL-15 in these cells. Moreover, MAYV was more susceptible than CHIKV to the antiviral effects of both type I and type II interferons. Taken together, this study shows that although MAYV and CHIKV are phylogenetically related, they induce different types of antiviral responses in astrocytes. This work is the first to evaluate the potential neurotropism of MAYV and shows that brain cells and particularly astrocytes and hNPCs are permissive to MAYV, which, consequently, could lead to MAYV-induced neuropathology.

Applications of minimally invasive multimodal telemetry for continuous monitoring of brain function and intracranial pressure in macaques with acute viral encephalitis

Alphaviruses such as Venezuelan equine encephalitis virus (VEEV) and Eastern equine encephalitis virus (EEEV) are arboviruses that can cause severe zoonotic disease in humans. Both VEEV and EEEV are highly infectious when aerosolized and can be used as biological weapons. Vaccines and therapeutics are urgently needed, but efficacy determination requires animal models. The cynomolgus macaque (Macaca fascicularis) provides a relevant model of human disease, but questions remain whether vaccines or therapeutics can mitigate CNS infection or disease in this model. The documentation of alphavirus encephalitis in animals relies on traditional physiological biomarkers and behavioral/neurological observations by veterinary staff; quantitative measurements such as electroencephalography (EEG) and intracranial pressure (ICP) can recapitulate underlying encephalitic processes. We detail a telemetry implantation method suitable for continuous monitoring of both EEG and ICP in awake macaques, as well as methods for collection and analysis of such data. We sought to evaluate whether changes in EEG/ICP suggestive of CNS penetration by virus would be seen after aerosol exposure of naïve macaques to VEEV IC INH9813 or EEEV V105 strains compared to mock-infection in a cohort of twelve adult cynomolgus macaques. Data collection ran continuously from at least four days preceding aerosol exposure and up to 50 days thereafter. EEG signals were processed into frequency spectrum bands (delta: [0.4 - 4Hz); theta: [4 - 8Hz); alpha: [8-12Hz); beta: [12-30] Hz) and assessed for viral encephalitis-associated changes against robust background circadian variation while ICP data was assessed for signal fidelity, circadian variability, and for meaningful differences during encephalitis. Results indicated differences in delta, alpha, and beta band magnitude in infected macaques, disrupted circadian rhythm, and proportional increases in ICP in response to alphavirus infection. This novel enhancement of the cynomolgus macaque model offers utility for timely determination of onset, severity, and resolution of encephalitic disease and for the evaluation of vaccine and therapeutic candidates.

Human monoclonal antibodies against Ross River virus target epitopes within the E2 protein and protect against disease

Ross River fever is a mosquito-transmitted viral disease that is endemic to Australia and the surrounding Pacific Islands. Ross River virus (RRV) belongs to the arthritogenic group of alphaviruses, which largely cause disease characterized by debilitating polyarthritis, rash, and fever. There is no specific treatment or licensed vaccine available, and the mechanisms of protective humoral immunity in humans are poorly understood. Here, we describe naturally occurring human mAbs specific to RRV, isolated from subjects with a prior natural infection. These mAbs potently neutralize RRV infectivity in cell culture and block infection through multiple mechanisms, including prevention of viral attachment, entry, and fusion. Some of the most potently neutralizing mAbs inhibited binding of RRV to Mxra8, a recently discovered alpahvirus receptor. Epitope mapping studies identified the A and B domains of the RRV E2 protein as the major antigenic sites for the human neutralizing antibody response. In experiments in mice, these mAbs were protective against cinical disease and reduced viral burden in multiple tissues, suggesting a potential therapeutic use for humans.

High costs of infection: Alphavirus infection reduces digestive function and bone and feather growth in nestling house sparrows (Passer domesticus)

Increasingly, ecoimmunology studies aim to use relevant pathogen exposure to examine the impacts of infection on physiological processes in wild animals. Alphaviruses are arthropod-borne, single-stranded RNA (ssRNA) viruses ("arboviruses") responsible for millions of cases of human illnesses each year. Buggy Creek virus (BCRV) is a unique alphavirus that is transmitted by a cimicid insect, the swallow bug, and is amplified in two avian species: the house sparrow (Passer domesticus) and the cliff swallow (Petrochelidon pyrrhonota). BCRV, like many alphaviruses, exhibits age-dependent susceptibility where the young are most susceptible to developing disease and exhibit a high mortality rate. However, alphavirus disease etiology in nestling birds is unknown. In this study, we infected nestling house sparrows with Buggy Creek virus and measured virological, pathological, growth, and digestive parameters following infection. Buggy Creek virus caused severe encephalitis in all infected nestlings, and the peak viral concentration in brain tissue was over 34 times greater than any other tissue. Growth, tissue development, and digestive function were all significantly impaired during BCRV infection. However, based on histopathological analysis performed, this impairment does not appear to be the result of direct tissue damage by the virus, but likely caused by encephalitis and neuronal invasion and impairment of the central nervous system. This is the first study to examine the course of alphavirus diseases in nestling birds and these results will improve our understanding of age-dependent infections of alphaviruses in vertebrate hosts.

Interleukin-10 Modulation of Virus Clearance and Disease in Mice with Alphaviral Encephalomyelitis

Alphaviruses are an important cause of mosquito-borne outbreaks of arthritis, rash, and encephalomyelitis. Previous studies in mice with a virulent strain (neuroadapted SINV [NSV]) of the alphavirus Sindbis virus (SINV) identified a role for Th17 cells and regulation by interleukin-10 (IL-10) in the pathogenesis of fatal encephalomyelitis (K. A. Kulcsar, V. K. Baxter, I. P. Greene, and D. E. Griffin, Proc Natl Acad Sci U S A 111:16053-16058, 2014, https://doi.org/10.1073/pnas.1418966111). To determine the role of virus virulence in generation of immune responses, we analyzed the modulatory effects of IL-10 on disease severity, virus clearance, and the CD4+ T cell response to infection with a recombinant strain of SINV of intermediate virulence (TE12). The absence of IL-10 during TE12 infection led to longer morbidity, more weight loss, higher mortality, and slower viral clearance than in wild-type mice. More severe disease and impaired virus clearance in IL-10-/- mice were associated with more Th1 cells, fewer Th2 cells, innate lymphoid type 2 cells, regulatory cells, and B cells, and delayed production of antiviral antibody in the central nervous system (CNS) without an effect on Th17 cells. Therefore, IL-10 deficiency led to more severe disease in TE12-infected mice by increasing Th1 cells and by hampering development of the local B cell responses necessary for rapid production of antiviral antibody and virus clearance from the CNS. In addition, the shift from Th17 to Th1 responses with decreased virus virulence indicates that the effects of IL-10 deficiency on immunopathologic responses in the CNS during alphavirus infection are influenced by virus strain.IMPORTANCE Alphaviruses cause mosquito-borne outbreaks of encephalomyelitis, but determinants of outcome are incompletely understood. We analyzed the effects of the anti-inflammatory cytokine IL-10 on disease severity and virus clearance after infection with an alphavirus strain of intermediate virulence. The absence of IL-10 led to longer illness, more weight loss, more death, and slower viral clearance than in mice that produced IL-10. IL-10 influenced development of disease-causing T cells and entry into the brain of B cells producing antiviral antibody. The Th1 pathogenic cell subtype that developed in IL-10-deficient mice infected with a less virulent virus was distinct from the Th17 subtype that developed in response to a more virulent virus, indicating a role for virus strain in determining the immune response. Slow production of antibody in the nervous system led to delayed virus clearance. Therefore, both the virus strain and the host response to infection are important determinants of outcome.

Use of Salmon Cardiac Primary Cultures (SCPCs) of different genotypes for comparative kinetics of mx expression, viral load and ultrastructure pathology, after infection with Salmon Pancreas Disease Virus (SPDV)

In vitro fish based models have been extensively applied in human biomedical research but, paradoxically, less frequently in the research of fish health issues. Farmed Atlantic salmon can suffer from several viral conditions affecting the heart. Therefore, species-specific, cardiac in vitro models may represent a useful tool to help further understanding and management of these diseases. The mechanisms underlying genotype based resistance are complex and usually rely on a combined effect of elements from both the innate and adaptive immune response, which are further complicated by external environmental factors. Here we propose that Salmon Cardiac Primary Cultures (SCPCs) are a useful tool to investigate these mechanisms as the basis for genotypic differences between Atlantic salmon families in susceptibility to cardiotropic viral disease. Using SCPCs produced from two different commercially available Atlantic salmon embryonated ova (Atlantic Ova IPN sensitive" (S) and "Atlantic QTL-innOva^® IPN/PD" (R)), the influence of host genotype on the viral load and mx expression following Salmon Pancreas Disease Virus infection was assessed over a 15 day period. Both R and S SCPCs groups were successfully infected. A measurable difference between groups of viral nsP1 and host antiviral mx gene expression was observed (i.e. a later, but larger onset of mx expression in the R group). Mx expression peaks were followed by a decrease in viral nsP1 in both groups. Additionally, ultrastructural examination of infected SCPCs allowed the description of degenerative changes at the individual cell level. The SCPC model presents some advantages, over current fish cell culture monolayers and in vivo material, such as the presence of different cell components normally present in the target organ, as well as the removal of a layer of functional complexity (acquired immunity), making it possible to focus on tissue specific, early innate immune mechanisms. These preliminary results highlight the importance of considering genetic origin when selecting the fish source for the production of SCPCs, as well as their usefulness as screening tools for assessment of genotypic differences in disease resistance.

Lower temperatures reduce type I interferon activity and promote alphaviral arthritis

Chikungunya virus (CHIKV) belongs to a group of mosquito-borne alphaviruses associated with acute and chronic arthropathy, with peripheral and limb joints most commonly affected. Using a mouse model of CHIKV infection and arthritic disease, we show that CHIKV replication and the ensuing foot arthropathy were dramatically reduced when mice were housed at 30°C, rather than the conventional 22°C. The effect was not associated with a detectable fever, but was dependent on type I interferon responses. Bioinformatics analyses of RNA-Seq data after injection of poly(I:C)/jetPEI suggested the unfolded protein response and certain type I interferon responses are promoted when feet are slightly warmer. The ambient temperature thus appears able profoundly to effect anti-viral activity in the periphery, with clear consequences for alphaviral replication and the ensuing arthropathy. These observations may provide an explanation for why alphaviral arthropathies are largely restricted to joints of the limbs and the extremities.

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.

Selective precipitation reaction: a novel diagnostic test for tissue pathology in Atlantic salmon, Salmo salar, infected with salmonid alphavirus (SAV3)

While investigating biomarkers for infection with salmonid alphavirus (SAV), the cause of pancreas disease (PD), a selective precipitation reaction (SPR) has been discovered in serum which could be an on-farm qualitative test and an in-laboratory quantitative assay for health assessments in aquaculture. Mixing serum from Atlantic salmon, Salmo salar, with SAV infection with a sodium acetate buffer caused a visible precipitation which does not occur with serum from healthy salmon. Proteomic examination of the precipitate has revealed that the components are a mix of muscle proteins, for example enolase and aldolase, along with serum protein such as serotransferrin and complement C9. The assay has been optimized for molarity, pH, temperature and wavelength so that the precipitation can be measured as the change in optical density at 340 nm (Δ₃₄₀ ). Application of the SPR assay to serum samples from a cohabitation trial of SAV infection in salmon showed that the Δ₃₄₀ in infected fish rose from undetectable to a maximum at 6 weeks post-infection correlating with histopathological score of pancreas, heart and muscle damage. This test may have a valuable role to play in the diagnostic evaluation of stock health in salmon.

Glutamine antagonist-mediated immune suppression decreases pathology but delays virus clearance in mice during nonfatal alphavirus encephalomyelitis

Infection of weanling C57BL/6 mice with the TE strain of Sindbis virus (SINV) causes nonfatal encephalomyelitis associated with hippocampal-based memory impairment that is partially prevented by treatment with 6-diazo-5-oxo-l-norleucine (DON), a glutamine antagonist (Potter et al., J Neurovirol 21:159, 2015). To determine the mechanism(s) of protection, lymph node and central nervous system (CNS) tissues from SINV-infected mice treated daily for 1 week with low (0.3mg/kg) or high (0.6mg/kg) dose DON were examined. DON treatment suppressed lymphocyte proliferation in cervical lymph nodes resulting in reduced CNS immune cell infiltration, inflammation, and cell death compared to untreated SINV-infected mice. Production of SINV-specific antibody and interferon-gamma were also impaired by DON treatment with a delay in virus clearance. Cessation of treatment allowed activation of the antiviral immune response and viral clearance, but revived CNS pathology, demonstrating the ability of the immune response to mediate both CNS damage and virus clearance.

Virus entry and replication in the brain precedes blood-brain barrier disruption during intranasal alphavirus infection

Viral infections of the central nervous system (CNS) are often associated with blood-brain barrier (BBB) disruption, yet the impact of virus replication and immune cell recruitment on BBB integrity are incompletely understood. Using two-photon microscopy, we demonstrate that Venezuelan equine encephalitis virus (VEEV) strain TC83-GFP, a GFP expressing, attenuated strain with a G3A mutation within the 5' UTR that is associated with increased sensitivity to type I interferons (IFNs), does not directly impact BBB permeability. Following intranasal infection of both wild-type and IFN-induced protein with tetratricopeptide repeats 1 (IFIT1)-deficient mice, which fail to block TC83-specific RNA translation, virus spreads to the olfactory bulb and cortex via migration along axonal tracts of neurons originating from the olfactory neuroepithelium. Global dissemination of virus in the CNS by 2days post-infection (dpi) was associated with increased BBB permeability in the olfactory bulb, but not in the cortex or hindbrain, where permeability only increased after the recruitment of CX3CR1⁺ and CCR2⁺ mononuclear cells on 6 dpi, which corresponded with tight junction loss and claudin 5 redistribution. Importantly, despite higher levels of viral replication, similar results were obtained in IFIT1-deficient mice. These findings indicate that TC83 gains CNS access via anterograde axonal migration without directly altering BBB function and that mononuclear and endothelial cell interactions may underlie BBB disruption during alphavirus encephalitis.

Mortality and weight loss of Atlantic salmon, Salmon salar L., experimentally infected with salmonid alphavirus subtype 2 and subtype 3 isolates from Norway

Pancreas disease (PD) caused by salmonid alphavirus (SAV) has a significant negative economic impact in the salmonid fish farming industry in northern Europe. Until recently, only SAV subtype 3 was present in Norwegian fish farms. However, in 2011, a marine SAV 2 subtype was detected in a fish farm outside the PD-endemic zone. This subtype has spread rapidly among fish farms in mid-Norway. The PD mortality in several farms has been lower than expected, although high mortality has also been reported. In this situation, the industry and the authorities needed scientific-based information about the virulence of the marine SAV 2 strain in Norway to decide how to handle this new situation. Atlantic salmon post-smolts were experimentally infected with SAV 2 and SAV 3 strains from six different PD cases in Norway. SAV 3-infected fish showed higher mortality than SAV 2-infected fish. Among the SAV 3 isolates, two isolates gave higher mortality than the third one. At the end of the experiment, fish in all SAV-infected groups had significantly lower weight than the uninfected control fish. This is the first published paper on PD to document that waterborne infection produced significantly higher mortality than intraperitoneal injection.

Long-Term Arthralgia after Mayaro Virus Infection Correlates with Sustained Pro-inflammatory Cytokine Response

Mayaro virus (MAYV), an alphavirus similar to chikungunya virus (CHIKV), causes an acute debilitating disease which results in the development of long-term arthralgia in more than 50% of infected individuals. Currently, the immune response and its role in the development of MAYV-induced persistent arthralgia remain unknown. In this study, we evaluated the immune response of individuals with confirmed MAYV infection in a one-year longitudinal study carried out in Loreto, Peru. We report that MAYV infection elicits robust immune responses that result in the development of a strong neutralizing antibody response and the secretion of pro-inflammatory immune mediators. The composition of these inflammatory mediators, in some cases, differed to those previously observed for CHIKV. Key mediators such as IL-13, IL-7 and VEGF were strongly induced following MAYV infection and were significantly increased in subjects that eventually developed persistent arthralgia. Although a strong neutralizing antibody response was observed in all subjects, it was not sufficient to prevent the long-term outcomes of MAYV infection. This study provides initial immunologic insight that may eventually contribute to prognostic tools and therapeutic treatments against this emerging pathogen.

Mayaro virus (MAYV) causes an acute debilitating disease which results in the development of long-term arthralgia in more than 50% of infected individuals, similarly to what has been described with CHIKV. In this study, we evaluated the immune response of individuals with confirmed MAYV infection in a one-year longitudinal study carried out in Loreto, Peru. Here, we report that MAYV infection elicits robust immune responses that result in the development of a strong neutralizing antibody response and the secretion of pro-inflammatory immune mediators. These inflammatory mediators, in some cases, differed to those observed by others for CHIKV. We also observed a strong neutralizing antibody response in all the study subjects; however, this response was not sufficient to prevent the long-term outcomes of MAYV infection. Taken together, this study provides initial immunologic insight that may eventually contribute to the development of prognostic tools and potential therapeutic treatments against this emerging pathogen.

Clinical manifestations of pancreas disease outbreaks in Norwegian marine salmon farming - variations due to salmonid alphavirus subtype

Pancreas disease (PD) in Norwegian salmonid aquaculture has traditionally been caused by salmonid alphavirus (SAV) subtype 3. Following the isolation of a novel SAV subtype in 2010, marine SAV2, two separate endemic areas have developed. It has been debated whether disease outbreaks due to marine SAV2 result in milder clinical manifestations compared to outbreaks caused by SAV3. The aim of this study was to descriptively investigate site-level differences in the clinical manifestations of marine SAV2 and SAV3 at Norwegian seawater sites diagnosed with PD in 2012. The findings suggest that Norwegian PD outbreaks caused by marine SAV2 result in lower mortality and milder clinical signs compared to outbreaks caused by SAV3. For sites without reported PD-related mortality, there was no difference in the mortality levels between sites infected by marine SAV2 and SAV3. The results also indicate that there are no differences in grading quality at slaughter between the SAV subtypes.

An experimental means of transmitting pancreas disease in Atlantic salmon Salmo salar L. fry in freshwater

A challenge model for pancreas disease in Atlantic salmon, Salmo salar L. fry, was developed comparing two salmonid alphavirus (SAV) subtypes: SAV1 and SAV5. Viral doses of 3 × 10(5) TCID50  mL(-1) for SAV1 and 3 × 10(4) for SAV5 were tested in triplicate tanks, each containing 450 salmon fry. Cumulative mortalities of 1.2% were recorded. Titres of virus recovered from the mortalities ranged from 10(2) to 10(7) TCID50  mL(-1) . Fry were sampled at 3, 5 and 7.5 weeks post-challenge. Sampling after 3 weeks revealed a high prevalence of infection in the absence of clinical signs, and infectious virus was recovered from 80% and 43% of sampled fry infected with SAV1 and SAV5, respectively. After 5 weeks pancreas, heart and red skeletal muscle lesions were generally observed, whilst degeneration in white skeletal muscle was observed only in fish infected with SAV1. In situ hybridisation confirmed the presence of viral genome in infected pancreas, heart and muscle. After 7.5 weeks, infectious virus (both isolates) was recovered from 13.3% of the fish sampled, with a viral titre of 10(2) TCID50  mL(-1) . Clearly, salmon fry are susceptible to SAV infection and pancreas disease.

Interleukin 10 modulation of pathogenic Th17 cells during fatal alphavirus encephalomyelitis

Mosquito-borne alphaviruses are important causes of epidemic encephalomyelitis. Neuronal cell death during fatal alphavirus encephalomyelitis is immune-mediated; however, the types of cells involved and their regulation have not been determined. We show that the virus-induced inflammatory response was accompanied by production of the regulatory cytokine IL-10, and in the absence of IL-10, paralytic disease occurred earlier and mice died faster. To determine the reason for accelerated disease in the absence of IL-10, immune responses in the CNS of IL-10(-/-) and wild-type (WT) mice were compared. There were no differences in the amounts of brain inflammation or peak virus replication; however, IL-10(-/-) animals had accelerated and increased infiltration of CD4(+)IL-17A(+) and CD4(+)IL-17A(+)IFNγ(+) cells compared with WT animals. Th17 cells infiltrating the brain demonstrated a pathogenic phenotype with the expression of the transcription factor, Tbet, and the production of granzyme B, IL-22, and GM-CSF, with greater production of GM-CSF in IL-10(-/-) mice. Therefore, in fatal alphavirus encephalomyelitis, pathogenic Th17 cells enter the CNS at the onset of neurologic disease and, in the absence of IL-10, appear earlier, develop into Th1/Th17 cells more often, and have greater production of GM-CSF. This study demonstrates a role for pathogenic Th17 cells in fatal viral encephalitis.

Manipulation of host factors optimizes the pathogenesis of western equine encephalitis virus infections in mice for antiviral drug development

While alphaviruses spread naturally via mosquito vectors, some can also be transmitted as aerosols making them potential bioterrorism agents. One such pathogen, western equine encephalitis virus (WEEV), causes fatal human encephalitis via multiple routes of infection and thus presumably via multiple mechanisms. Although WEEV also produces acute encephalitis in non-human primates, a small animal model that recapitulates features of human disease would be useful for both pathogenesis studies and to evaluate candidate antiviral therapies. We have optimized conditions to infect mice with a low passage isolate of WEEV, thereby allowing detailed investigation of virus tropism, replication, neuroinvasion, and neurovirulence. We find that host factors strongly influence disease outcome, and in particular, that age, gender, and genetic background all have significant effects on disease susceptibility independent of virus tropism or replication within the central nervous system. Our data show that experimental variables can be adjusted in mice to recapitulate disease features known to occur in both non-human primates and humans, thus aiding further study of WEEV pathogenesis and providing a realistic therapeutic window for antiviral drug delivery.

First outbreak of sleeping disease in Switzerland: disease signs and virus characterization

Sleeping disease is a contagious disease mainly of freshwater farmed rainbow trout, caused by salmonid alphavirus (SAV) Subtype 2. Here we describe the first case in Switzerland. Pathological changes ranged from acute pancreas necrosis to more chronic lesions with complete loss of exocrine pancreas and simultaneous degenerative, inflammatory and regenerative heart and muscle lesions. The partial sequencing of SAV E2 and nsp3 genes placed the Swiss SAV variant within the Subtype 2 clustering together with freshwater isolates from UK and continental Europe. Although mortality stayed low, growth rates were significantly reduced, making the disease economically relevant.

[Isolation of the Chikungunya virus in Moscow from the Indonesian visitor (September, 2013)]

The results of the virological identification of the Chikungunya fever case in Moscow (September, 2013) in an Indonesian visitor are presented. The clinic, electron microscopy, and molecular genetic data are discussed. The Ghikungunya virus (CHIKV) strain CHIKVILEIV-Moscow/1/2013 belonging to the Asian genotype (ID GenBank KF872195) was deposited into the Russian State Collection of viruses (GKV 1239; 18.11.2013).

Real-time whole-body visualization of Chikungunya Virus infection and host interferon response in zebrafish

Chikungunya Virus (CHIKV), a re-emerging arbovirus that may cause severe disease, constitutes an important public health problem. Herein we describe a novel CHIKV infection model in zebrafish, where viral spread was live-imaged in the whole body up to cellular resolution. Infected cells emerged in various organs in one principal wave with a median appearance time of ∼14 hours post infection. Timing of infected cell death was organ dependent, leading to a shift of CHIKV localization towards the brain. As in mammals, CHIKV infection triggered a strong type-I interferon (IFN) response, critical for survival. IFN was mainly expressed by neutrophils and hepatocytes. Cell type specific ablation experiments further demonstrated that neutrophils play a crucial, unexpected role in CHIKV containment. Altogether, our results show that the zebrafish represents a novel valuable model to dynamically visualize replication, pathogenesis and host responses to a human virus.

Chikungunya, a re-emerging disease caused by a mosquito-transmitted virus, is an important public health problem. We developed a zebrafish model for chikungunya virus infection. For the first time, rise and death of virus-infected cells could be live imaged in the entire body of a vertebrate. We observed a widespread wave of apparition of newly infected cells during the first day after inoculation of the virus. We then found that infected cells died at a strongly organ-dependent rate, accounting for the progressive shift of virus localization. Notably, the virus persisted in the brain despite apparent recovery of infected zebrafish. We found this recovery to be critically dependent on the host type I interferon response. Surprisingly, we identified neutrophils as a major cell population expressing interferon and controlling chikungunya virus.

Chikungunya fever: a clinical and virological investigation of outpatients on Reunion Island, South-West Indian Ocean

Background

Chikungunya virus (CHIKV) is responsible for acute febrile polyarthralgia and, in a proportion of cases, severe complications including chronic arthritis. CHIKV has spread recently in East Africa, South-West Indian Ocean, South-Asia and autochthonous cases have been reported in Europe. Although almost all patients are outpatients, medical investigations mainly focused on hospitalised patients.

Methodology/Principal Findings

Here, we detail clinico-biological characteristics of Chikungunya (CHIK) outpatients in Reunion Island (2006). 76 outpatients with febrile arthralgia diagnosed within less than 48 hours were included by general practitioners during the CuraChik clinical trial. CHIK was confirmed in 54 patients and excluded in 22. A detailed clinical and biological follow-up was organised, that included analysis of viral intrahost diversity and telephone survey until day 300. The evolution of acute CHIK included 2 stages: the ‘viral stage’ (day 1–day 4) was associated with rapid decrease of viraemia and improvement of clinical presentation; the ‘convalescent stage’ (day 5–day 14) was associated with no detectable viraemia but a slower clinical improvement. Women and elderly had a significantly higher number of arthralgia at inclusion and at day 300. Based on the study clinico-biological dataset, scores for CHIK diagnosis in patients with recent febrile acute polyarthralgia were elaborated using arthralgia on hands and wrists, a minor or absent myalgia and the presence of lymphopenia (<1G/L) as major orientation criteria. Finally, we observed that CHIKV intra-host genetic diversity increased over time and that a higher viral amino-acid complexity at the acute stage was associated with increased number of arthralgia and intensity of sequelae at day 300.

Conclusions/Significance

This study provided a detailed picture of clinico-biological CHIK evolution at the acute phase of the disease, allowed the elaboration of scores to assist CHIK diagnosis and investigated for the first time the impact of viral intra-host genetic diversity on the disease course.

The mosquito-transmitted chikungunya virus is responsible for acute febrile polyarthralgia and, in a proportion of cases, complications including chronic arthritis. Since 2005, it has massively re-emerged in the Old World. Although the large majority of patients are outpatients, the most detailed studies have focused previously on hospitalised patients (i.e., severe cases). Here, we report the detailed clinico-biological characteristics of ‘standard’ clinical presentations in patients followed-up by general practitioners in Reunion Island (2006) during the CuraChik clinical trial. At the onset of the disease, two stages were observed: (i) a ‘viral stage’ during the first 4 days, associated with an acute febrile polyarthralgic syndrome and a subsequent rapid clinical improvement; the main clinico-biological characteristics during that period were used to elaborate supportive chikungunya diagnostic scores, (ii) a ‘convalescent stage’ (days 5–14) with no detectable viraemia but a slower clinical improvement. Woman and elderly patients were found at risk for more symptomatic forms of the disease at both the acute and late stages (day 300) and we observed that the viral intra-host genetic diversity increased over time and that a higher viral amino-acid complexity at the acute stage was associated with more symptomatic illness at the late stage of the disease.

A mouse model of chikungunya virus with utility in antiviral studies

Chikungunya virus (CHIKV) infection generally causes a debilitating arthritis in infected patients. Infection with CHIKV is generally not life-threatening and is associated with a mortality rate <0.1%. However, close to 100% of those infected will develop symptoms of disease, primarily involving swelling and pain of the joints, which can last for months or even years. A model that mimics these symptoms is needed for thedevelopment of therapies to ameliorate disease and control viral infection. In this chapter, we describe the establishment of a model of CHIKV infection in mice that is nonlethal and utilizes footpad swelling and virus titer of various tissues as key disease parameters. This model was developed primarily for use in evaluating the in vivo efficacy of candidate antiviral agents, although important questions regarding basic biology and pathogenesis of the disease may also be elucidated using this system.

The dendritic cell receptor DNGR-1 controls endocytic handling of necrotic cell antigens to favor cross-priming of CTLs in virus-infected mice

DNGR-1 (CLEC9A) is a receptor for necrotic cells required by DCs to cross-prime CTLs against dead cell antigens in mice. It is currently unknown how DNGR-1 couples dead cell recognition to cross-priming. Here we found that DNGR-1 did not mediate DC activation by dead cells but rather diverted necrotic cell cargo into a recycling endosomal compartment, favoring cross-presentation to CD8(+) T cells. DNGR-1 regulated cross-priming in non-infectious settings such as immunization with antigen-bearing dead cells, as well as in highly immunogenic situations such as infection with herpes simplex virus type 1. Together, these results suggest that DNGR-1 is a dedicated receptor for cross-presentation of cell-associated antigens. Our work thus underscores the importance of cross-priming in immunity and indicates that antigenicity and adjuvanticity can be decoded by distinct innate immune receptors. The identification of specialized receptors that regulate antigenicity of virus-infected cells reveals determinants of antiviral immunity that might underlie the human response to infection and vaccination.

Long-term chikungunya infection clinical manifestations after an outbreak in Italy: a prognostic cohort study

OBJECTIVES

Following a Chikungunya (CHIKV) outbreak in Italy, a cohort study was conducted to describe the infection long-term clinical course and outcome.

METHODS

Persons identified through active and passive surveillance as confirmed or possible CHIKV cases during the outbreak were enrolled and interviewed by trained public health nurses, between 4-5 and 12-13 months following the acute stage. Patients reporting persistent clinical symptoms were evaluated by rheumatologists. Serum samples were obtained and anti-CHIKV specific IgG and IgM immune responses detected. Only confirmed cases who completed the follow-up were analysed.

RESULTS

Out of 250 patients, 66.5% still reported myalgia, asthenia or arthralgia (most frequent sign) after 12 months. Functional ability, measured by the ROAD index, was more impaired for lower extremities (3.75; Inter Quartile Range - IQR 4.4), and the activities of daily living (average 4.2; IQR 5). Variables independently associated with the presence of joint pain at 12-13 months were increasing age, and history of rheumatologic diseases). Elderly, females, and persons with history of rheumatologic diseases had higher anti-CHIKV IgG titres at 12-13 months.

CONCLUSIONS

This study confirms, in an unselected population, that the long-lasting burden of CHIKV infection is significant.

Chikungunya disease: infection-associated markers from the acute to the chronic phase of arbovirus-induced arthralgia

At the end of 2005, an outbreak of fever associated with joint pain occurred in La Réunion. The causal agent, chikungunya virus (CHIKV), has been known for 50 years and could thus be readily identified. This arbovirus is present worldwide, particularly in India, but also in Europe, with new variants returning to Africa. In humans, it causes a disease characterized by a typical acute infection, sometimes followed by persistent arthralgia and myalgia lasting months or years. Investigations in the La Réunion cohort and studies in a macaque model of chikungunya implicated monocytes-macrophages in viral persistence. In this Review, we consider the relationship between CHIKV and the immune response and discuss predictive factors for chronic arthralgia and myalgia by providing an overview of current knowledge on chikungunya pathogenesis. Comparisons of data from animal models of the acute and chronic phases of infection, and data from clinical series, provide information about the mechanisms of CHIKV infection-associated inflammation, viral persistence in monocytes-macrophages, and their link to chronic signs.

Mannose binding lectin is required for alphavirus-induced arthritis/myositis

Mosquito-borne alphaviruses such as chikungunya virus and Ross River virus (RRV) are emerging pathogens capable of causing large-scale epidemics of virus-induced arthritis and myositis. The pathology of RRV-induced disease in both humans and mice is associated with induction of the host inflammatory response within the muscle and joints, and prior studies have demonstrated that the host complement system contributes to development of disease. In this study, we have used a mouse model of RRV-induced disease to identify and characterize which complement activation pathways mediate disease progression after infection, and we have identified the mannose binding lectin (MBL) pathway, but not the classical or alternative complement activation pathways, as essential for development of RRV-induced disease. MBL deposition was enhanced in RRV infected muscle tissue from wild type mice and RRV infected MBL deficient mice exhibited reduced disease, tissue damage, and complement deposition compared to wild-type mice. In contrast, mice deficient for key components of the classical or alternative complement activation pathways still developed severe RRV-induced disease. Further characterization of MBL deficient mice demonstrated that similar to C3^−/− mice, viral replication and inflammatory cell recruitment were equivalent to wild type animals, suggesting that RRV-mediated induction of complement dependent immune pathology is largely MBL dependent. Consistent with these findings, human patients diagnosed with RRV disease had elevated serum MBL levels compared to healthy controls, and MBL levels in the serum and synovial fluid correlated with severity of disease. These findings demonstrate a role for MBL in promoting RRV-induced disease in both mice and humans and suggest that the MBL pathway of complement activation may be an effective target for therapeutic intervention for humans suffering from RRV-induced arthritis and myositis.

Arthritogenic alphaviruses such as Ross River virus (RRV) and chikungunya virus are transmitted to humans by mosquitoes and cause epidemics of debilitating infectious arthritis and myositis in various areas around the world. Studies in humans and mice indicate that the host inflammatory response is critical for development of RRV-induced arthritis and myositis, and the host complement system, a component of the host inflammatory response, plays an essential role in the development of RRV-induced disease through activation of complement receptor 3 (CR3)-bearing inflammatory cells. Of the three main complement activation pathways, only the lectin pathway activated by mannose binding lectin (MBL) was essential for RRV-induced complement activation, tissue destruction, and disease. Furthermore, we found that levels of MBL were elevated in human patients suffering from RRV-induced polyarthritis and MBL levels correlated with disease severity. Taken together, our data implicates a role for MBL in mediating RRV-induced disease in both humans and mice, and suggests that therapeutic targeting of MBL may be an effective strategy for disease treatment in humans.

Neurodevelopmental outcome of neonates with vertically transmitted Chikungunya fever with encephalopathy

Neurodevelopmental follow-up of neonates with vertically transmitted Chikungunya fever has been infrequently reported. We herein report neurodevelopment follow up of two such babies at 3 year of age.

Chikungunya virus infection of cell lines: analysis of the East, Central and South African lineage

Chikungunya virus (CHIKV) is a re-emerging mosquito borne alphavirus that has caused large scale epidemics in the countries around the Indian Ocean, as well as leading to autochthonous transmission in some European countries. The transmission of the disease has been driven by the emergence of an African lineage of CHIKV with enhanced transmission and dissemination in Aedes mosquito hosts. Two main genotypes of this lineage have been circulating, characterized by the presence of a substitution of a valine for an alanine at position 226 of the E1 protein. The outbreak, numbering in millions of cases in the infected areas, has been associated with increasing numbers of cases with non-classical presentation including encephalitis and meningitis. This study sought to compare the original Ross strain with two isolates from the recent outbreak of chikungunya fever in respect of infectivity and the induction of apoptosis in eight mammalian cell lines and two insect cell lines, in addition to generating a comprehensive virus production profile for one of the newer isolates. Results showed that in mammalian cells there were few differences in either tropism or pathogenicity as assessed by induction of apoptosis with the exception of Hela cells were the recent valine isolate showed less infectivity. The Aedes albopictus C6/36 cell line was however significantly more permissive for both of the more recent isolates than the Ross strain. The results suggest that the increased infectivity seen in insect cells derives from an evolution of the CHIKV genome not solely associated with the E1:226 substitution.

Inflammatory cytokine expression is associated with chikungunya virus resolution and symptom severity

The Chikungunya virus infection zones have now quickly spread from Africa to parts of Asia, North America and Europe. Originally thought to trigger a disease of only mild symptoms, recently Chikungunya virus caused large-scale fatalities and widespread economic loss that was linked to recent virus genetic mutation and evolution. Due to the paucity of information on Chikungunya immunological progression, we investigated the serum levels of 13 cytokines/chemokines during the acute phase of Chikungunya disease and 6- and 12-month post-infection follow-up from patients of the Italian outbreak. We found that CXCL9/MIG, CCL2/MCP-1, IL-6 and CXCL10/IP-10 were significantly raised in the acute phase compared to follow-up samples. Furthermore, IL-1β, TNF-α, Il-12, IL-10, IFN-γ and IL-5 had low initial acute phase levels that significantly increased at later time points. Analysis of symptom severity showed association with CXCL9/MIG, CXCL10/IP-10 and IgG levels. These data give insight into Chikungunya disease establishment and subsequent convalescence, which is imperative to the treatment and containment of this quickly evolving and frequently re-emerging disease.

Chikungunya virus (CHIKV) is transmitted by mosquitoes and causes a human disease clinically characterized by sudden appearance of high fever, rash, headache, nausea, and severe joint pain (the defining symptom). Chikungunya was identified in Africa and the word Chikungunya means that which bends up, describing the bent posture of CHIKV patients while in severe pain. CHIKV, a current problem in Africa, Indian Ocean region, and Southeast Asia, is now spreading to temperate regions of North America, France and Italy. Presently, the immune response for CHIKV infection remains largely uninvestigated and no treatment is available. We investigated cytokine profiles at diagnosis and follow-up of CHIKV infected patients during the Italian 2007 outbreak and associated cytokine levels with antibody level and symptom severity. Cytokines, important immune mediators, are often drug targets. Since CHIKV symptoms can persist for months or years following infection it is important to investigate possible drug targets to alleviate discomfort. We found cytokine profiles that describe the initial infection and recovery phase. We determined the cytokines CXCL9/MIG and CXCL10/IP-10 as well as antibody levels were associated with symptom severity. These results reflect previously unreported cytokine profiles which may be important for the development of future therapeutics for CHIKV outbreaks.

Evaluation of an inactivated Ross River virus vaccine in active and passive mouse immunization models and establishment of a correlate of protection

Ross River Virus has caused reported outbreaks of epidemic polyarthritis, a chronic debilitating disease associated with significant long-term morbidity in Australia and the Pacific region since the 1920s. To address this public health concern, a formalin- and UV-inactivated whole virus vaccine grown in animal protein-free cell culture was developed and tested in preclinical studies to evaluate immunogenicity and efficacy in animal models. After active immunizations, the vaccine dose-dependently induced antibodies and protected adult mice from viremia and interferon α/β receptor knock-out (IFN-α/βR(-/-)) mice from death and disease. In passive transfer studies, administration of human vaccinee sera followed by RRV challenge protected adult mice from viremia and young mice from development of arthritic signs similar to human RRV-induced disease. Based on the good correlation between antibody titers in human sera and protection of animals, a correlate of protection was defined. This is of particular importance for the evaluation of the vaccine because of the comparatively low annual incidence of RRV disease, which renders a classical efficacy trial impractical. Antibody-dependent enhancement of infection, did not occur in mice even at low to undetectable concentrations of vaccine-induced antibodies. Also, RRV vaccine-induced antibodies were partially cross-protective against infection with a related alphavirus, Chikungunya virus, and did not enhance infection. Based on these findings, the inactivated RRV vaccine is expected to be efficacious and protect humans from RRV disease.

A comparative study of marine salmonid alphavirus subtypes 1-6 using an experimental cohabitation challenge model

A comparative challenge study of six marine isolates representing subtypes 1-6 of salmonid alphavirus (salmon pancreas disease virus, Genus Alphavirus, Family Togaviridae) was conducted in Atlantic salmon in a fresh water cohabitation trial. Histopathological lesions typical of pancreas disease were observed with all subtypes, and virus was re-isolated from serum of cohabitant fish in each case. Using a virus neutralization (VN) test neutralizing salmonid alphavirus (SAV) subtype 1 strain F93-125, VN antibodies were detected in all challenge groups, consistent with serological cross-reactivity between these subtypes. Using real-time RT-PCR, SAV RNA was detected in heart tissue from 2 to 3 weeks post-challenge (wpc) in all cohabitant groups excluding controls. The results obtained suggested differences in the dynamics of infection between strains of SAV and potentially between subtypes. Results for SAV subtypes 1 and 3 suggested essentially synchronous infection of cohabitant fish. These two study groups also had the highest virus load in heart tissue as measured by quantitative RT-PCR and also had the most extensive histopathological changes. In contrast, results for SAV subtypes 2 and 6 strains were consistent with asynchronous infection in the cohabitant fish and were characterized by slow spread, low virus loads and mild histopathological changes. The SAV subtype 4 and 5 strains occupied an intermediate position in this regard. Despite the use of concentration procedures, it was not possible to detect SAV RNA in water samples from selected study tanks. However, testing of faeces from the SAV subtypes 1, 3 and 6 challenge groups found positive signals in each beginning at 1-3 wpc and remaining detectable for a further 2-3 weeks. Parallel testing of mucus samples found these became positive at 2-3 wpc and remained positive for a further 1-3 weeks. These results demonstrate for the first time that shedding and transmission of virus may occur by both these routes and suggest that dispersal in these matrices should be included in any disease transmission models.

Salmonid alphavirus (SAV) and pancreas disease (PD) in Atlantic salmon, Salmo salar L., in freshwater and seawater sites in Norway from 2006 to 2008

A cohort study was initiated in the spring of 2006 to investigate epidemiological aspects and pathogenesis of salmonid alphavirus (SAV) subtype 3 infections and pancreas disease (PD). The aims were to assess involvement of the freshwater production phase, the extent and frequency of subclinical infections and to follow PD-affected populations throughout the entire seawater production cycle, as well as investigate possible risk factors for PD outbreaks. Fish groups from 46 different Atlantic salmon freshwater sites in six counties were sampled once prior to seawater transfer and followed onto their seawater sites. A total of 51 Atlantic salmon seawater sites were included, and fish groups were sampled three times during the seawater production phase. SAV subtype 3 was not identified by real-time RT-PCR from samples collected in the freshwater phase, nor were any SAV-neutralizing antibodies or histopathological changes consistent with PD. In the seawater phase, SAV was detected in samples from 23 of 36 (63.9%) studied sites located within the endemic region. No SAV subtype 3 was detected in samples from seawater sites located outside the endemic region. The cumulative incidence of PD during the production cycle amongst sites with SAV detected was 87% (20 of 23 sites). Average fish weight at time of PD diagnosis ranged from 461 to 5978 g, because of a wide variation in the timing of disease occurrence throughout the production cycle. Mortality levels following a PD diagnosis varied greatly between populations. The mean percentage mortality was 6.9% (+/-7.06) (range 0.7-26.9), while the mean duration of increased mortality following PD diagnosis was 2.8 months (+/-1.11) (range 1-6).

Prospective longitudinal studies of salmonid alphavirus infections on two Atlantic salmon farms in Ireland; evidence for viral persistence

Prospective longitudinal studies of two outbreaks of pancreas disease in Atlantic salmon (AS), Salmo salar L., in Ireland were conducted. Both outbreaks occurred during the marine phase of production, with one caused by salmonid alphavirus subtype 1 (SAV1) and the other by SAV4. In addition to screening a range of tissues by real-time reverse transcriptase polymerase chain reaction (RRT-PCR), virological, serological and histopathological examinations were performed along with partial genome sequencing and results were related to environmental and production data and farm history. On Farm 1 (marine sampling only), infection was detected within 3 weeks of smolts being placed on the farm, while on Farm 2 (freshwater and marine sampling), infection was first detected 315 days after transfer to sea. In both outbreaks, RRT-PCR signals were detected in a range of tissues including gill, heart, kidney, pancreas/pyloric caeca, brain and serum. Persistence of signal was longest in gill and heart (> or =265 days on both farms) and shortest in serum. Mortalities on the two farms varied from 10.9% to 30%. In both cases, partial genome sequence of the causative viruses were identical to SAV strains detected in previous populations of AS on each of the study farms, including populations with which the study populations overlapped in time and space.

A case of chikungunya fever imported from India to Japan, follow-up of specific IgM and IgG antibodies over a 6-month period

Chikungunya fever is an arboviral disease caused by chikungunya virus. A 37-year-old Japanese male visited India and developed fever, myalgia, rash, and persisting systemic arthralgia, the latter of which persisted for more than 2 months. The patient was diagnosed with chikungunya fever by virological and serological examinations. In the present study, we followed specific antibody responses over a 6-month period after the onset of the disease. IgM antibody was detected on days 58 and 108, but not on day 137, by enzyme-linked immunosorbent assay. Specific IgG and neutralizing antibodies were detected as late as day 192. The results indicate that specific IgM lasts for 3 to 4 months from the onset of the disease, and that IgG lasts more than 6 months.

Clinical profile of chikungunya fever in patients in a tertiary care centre in Maharashtra, India

BACKGROUND & OBJECTIVE

In India a chikungunya fever outbreak started in December 2005 when the country experienced more than 13 lakhs of chikungunya infected cases. We undertook this study to study detailed clinical profile of chikungunya fever in both indoor and outdoor patients in a tertiary care hospital in Nagpur, Maharashtra in 2006.

METHODS

Suspected cases of chikungunya fever (n=405) during the period of July to September 2006, having clinical triad of fever, arthralgia and/or rashes were included in the study. Clinical profile was studied in all the cases. Of the 405 samples collected, 166 were tested for serum CHIK IgM antibodies.

RESULTS

Of the 166 samples tested for CHIKV IgM antibodies, 87 (52.4%) were positive (confirmed cases). Male: female ratio was 2.3:1. Fever and arthralgia were present in all cases. Rash was present in 27 (31%) confirmed and 38 (12%) suspected cases. Lymphadenopathy was present in 12 (13.8 %) confirmed and 4 of suspected cases. Chronic polyarthritis was seen in 22 (25.3%) confirmed and 75 (23.6%) suspected cases. Neurological manifestations were observed in 08 (9%) confirmed and 10 (3.14%) suspected cases. Mortality was 7 (2.2%) in 318 suspected cases and 3 (3.4%) in 87 confirmed cases.

INTERPRETATION & CONCLUSION

Our findings showed that about half of the serum samples for CHIKV IgM antibody tested positive from cases suspected to have chikungunya fever. Fever, joint pain and headache were major symptoms. Certain rare manifestations like lymphodenopathy, oral ulcers and encephalitis were also seen. Mortality in confirmed cases was about 3.4 per cent.

Entomo-epidemiological investigations on chikungunya outbreak in the Lakshadweep islands, Indian Ocean

BACKGROUND & OBJECTIVE

An outbreak of chikungunya fever characterized by prolonged incapacitation in the Lakshadweep islands in Indian Ocean occurred in November 2006. We undertook the entomological and epidemiological investigations on the Chikungunya outbreak in the Lakshadweep islands, Indian Ocean.

METHODS

Epidemic information in the affected places was obtained from the local hospital records. Entomological observations like larval survey and the adult resting/landing collections by the hand collection methods were individually conducted in the two affected islands Andrott and Kalpeni in November and December 2006.

RESULTS

The main breeding sources of the mosquitoes were the rodent-devoured coconuts, coconut shells, areca nut soaking mud and plastic pots, discarded containers, grinding stones, metal containers and plastic containers. Aedes albopictus was pre-dominantly present in the Lakshadweep islands.

INTERPRETATION & CONCLUSION

It is concluded that the routine campaigns need to be organized regularly within the community highlighting the potential breeding grounds of mosquitoes and the possible control methods. Source reduction strategies like destruction of coconut shells and rodent-devoured coconuts by burning or by burying them inside the ground. Ae. albopictus played major role as the vector mosquitoes responsible for the chikungunya transmission.

Susceptibility of colorectal cancer cells to Sindbis virus infection

Sindbis virus (SIN), a member of the Togaviridae family, infects a broad range of cells and has been shown to be an effective anti-tumor agent. The infection efficiency of the virus, however, varies greatly among target cells. In this report, we compared the ability of SIN to infect colorectal cancer cells and cells of other cancer origin. While tumor cells from breast, leukemia, and prostate cancers were largely resistant to SIN infection, nine of the ten colorectal cancer cell lines tested were sensitive to SIN infection. Moreover, SIN susceptibility correlated with the metastatic potential of the colorectal cancer cells. Two highly aggressive and invasive cell lines, SW620 and COLO-320DM were the most sensitive to SIN infection. Similarly, SIN preferentially targeted metastatic tumor cells in a mouse xenograft model for colon cancer progression. The higher infection rate was not due to increased expression of the 67kD laminin receptor, a specific receptor for SIN infection, although viral attachment and entry were markedly enhanced in SW620 cells. These results suggest that SIN may employ a novel cell attachment/entry mechanism during infection, allowing selective targeting of colorectal cancer cells.

Chikungunya encephalomyeloradiculitis: report of 2 cases with neuroimaging and 1 case with autopsy findings

Chikungunya, an alphavirus presenting with fever, rash, and polyarthritis, is derived from the Makonde word that means "that which bends up," in reference to the crippling manifestations of the disease. Most often it is a self-limiting febrile illness. Neurologic complications of Chikungunya infection have been reported. We are reporting the clinical and neuroimaging data in 2 patients with Chikungunya encephalomyeloradiculitis and brain autopsy findings in 1 patient.

Chimeric alphavirus vaccine candidates for chikungunya

Chikungunya virus (CHIKV) is an emerging alphavirus that has caused major epidemics in India and islands off the east coast of Africa since 2005. Importations into Europe and the Americas, including one that led to epidemic transmission in Italy during 2007, underscore the risk of endemic establishment elsewhere. Because there is no licensed human vaccine, and an attenuated Investigational New Drug product developed by the U.S. Army causes mild arthritis in some vaccinees, we developed chimeric alphavirus vaccine candidates using either Venezuelan equine encephalitis attenuated vaccine strain TC-83, a naturally attenuated strain of eastern equine encephalitis virus (EEEV), or Sindbis virus as a backbone and the structural protein genes of CHIKV. All vaccine candidates replicated efficiently in cell cultures, and were highly attenuated in mice. All of the chimeras also produced robust neutralizing antibody responses, although the TC-83 and EEEV backbones appeared to offer greater immunogenicity. Vaccinated mice were fully protected against disease and viremia after CHIKV challenge.

An animal model for studying the pathogenesis of chikungunya virus infection

Newborn and 14-day-old mice inoculated subcutaneously with chikungunya virus (CHIKV) developed lethargy, difficulty walking, dragging of hind limbs, and reduced weight gain within 7-10 days after infection (PI). During the initial 6-7 days PI, the animals had viremia; high levels (10(6)-10(8) PFU) of CHIKV were also present in leg muscle. The virus persisted in muscle for several days after viremia disappeared. The major histopathologic changes were in skeletal muscle, which were focal necrosis and inflammation, followed by fibrosis and dystrophic calcification. Some mice also showed dystrophic calcification in the joint cartilage, but there were few deaths, and most of the animals eventually recovered. CHIKV antigen was shown by immunohistochemistry in the muscle for several weeks after infection. Based on the clinical and pathologic similarities with CHIKV infection in humans, young ICR and CD-1 mice offer a useful and realistic model for further study of the pathogenesis and treatment of CHIKV infection.

The biology of chikungunya: a brief review of what we still do not know

Responsible for a massive outbreak in the Indian Ocean in 2005-2006, the chikungunya virus is also reemerging in India where it has already infected over a million persons. Imported cases of the disease are reported in Asia, USA, and Europe, where a small epidemic occurred, due to transmission by local mosquitoes. Chikungunya virus is an alphavirus (Togaviridae family) that usually induces an acute illness characterized by fever, rash, and painful, incapacitating arthralgia a few days after being bitten by an infected mosquito, but recurrent joint pains are frequent. Unusual severe forms of the disease are also being reported that emphasize the importance of close monitoring of arboviruses in more fragile populations, such as the elderly and the newborns. Alphaviruses have generally been studied out of their epidemic context, leading to a large knowledge of their molecular features, and a much narrower understanding of their epidemiology and induced pathogenesis. Deciphering chikungunya virus specific molecular features as well as how the virus interacts with its vector and with its host are key to foresee, prevent and manage future epidemics, as well as prevent, treat or cure chikungunya disease.

A mouse model for Chikungunya: young age and inefficient type-I interferon signaling are risk factors for severe disease

Chikungunya virus (CHIKV) is a re-emerging arbovirus responsible for a massive outbreak currently afflicting the Indian Ocean region and India. Infection from CHIKV typically induces a mild disease in humans, characterized by fever, myalgia, arthralgia, and rash. Cases of severe CHIKV infection involving the central nervous system (CNS) have recently been described in neonates as well as in adults with underlying conditions. The pathophysiology of CHIKV infection and the basis for disease severity are unknown. To address these critical issues, we have developed an animal model of CHIKV infection. We show here that whereas wild type (WT) adult mice are resistant to CHIKV infection, WT mouse neonates are susceptible and neonatal disease severity is age-dependent. Adult mice with a partially (IFN-alpha/betaR(+/-)) or totally (IFN-alpha/betaR(-/-)) abrogated type-I IFN pathway develop a mild or severe infection, respectively. In mice with a mild infection, after a burst of viral replication in the liver, CHIKV primarily targets muscle, joint, and skin fibroblasts, a cell and tissue tropism similar to that observed in biopsy samples of CHIKV-infected humans. In case of severe infections, CHIKV also disseminates to other tissues including the CNS, where it specifically targets the choroid plexuses and the leptomeninges. Together, these data indicate that CHIKV-associated symptoms match viral tissue and cell tropisms, and demonstrate that the fibroblast is a predominant target cell of CHIKV. These data also identify the neonatal phase and inefficient type-I IFN signaling as risk factors for severe CHIKV-associated disease. The development of a permissive small animal model will expedite the testing of future vaccines and therapeutic candidates.