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Ross River (RR) virus is an alphavirus endemic to Australia and New Guinea and is the aetiological agent of epidemic polyarthritis or RR virus disease. Here we provide evidence that RR virus uses the collagen-binding alpha1beta1 integrin as a cellular receptor. Infection could be inhibited by collagen IV and antibodies specific for the beta1 and alpha1 integrin proteins, and fibroblasts from alpha1-integrin-/- mice were less efficiently infected than wild-type fibroblasts. Soluble alpha1beta1 integrin bound immobilized RR virus, and peptides representing the alpha1beta1 integrin binding-site on collagen IV inhibited virus binding to cells. We speculate that two highly conserved regions within the cell-receptor binding domain of E2 mimic collagen and provide access to cellular collagen-binding receptors.

Antibody-dependent enhancement (ADE) of macrophage and monocyte infection has been demonstrated in vitro for some of the most deadly RNA viruses known. Recent evidence suggests that ADE-mediated ligation of Fc receptors might suppress host-cell antiviral gene expression by promoting early interleukin-10 (IL-10) secretion, resulting in the expression of suppressor-of-cytokine-signalling (SOCS) proteins and a Th2 bias. These findings provide potential new insights into how ADE might enhance viral infections and exacerbate disease.

A novel alphavirus was isolated from the louse Lepidophthirus macrorhini , collected from southern elephant seals, Mirounga leonina , on Macquarie Island, Australia. The virus displayed classic alphavirus ultrastructure and appeared to be serologically different from known Australasian alphaviruses. Nearly all Macquarie Island elephant seals tested had neutralizing antibodies against the virus, but no virus-associated pathology has been identified. Antarctic Division personnel who have worked extensively with elephant seals showed no serological evidence of exposure to the virus. Sequence analysis illustrated that the southern elephant seal (SES) virus segregates with the Semliki Forest group of Australasian alphaviruses. Phylogenetic analysis of known alphaviruses suggests that alphaviruses might be grouped according to their enzootic vertebrate host class. The SES virus represents the first arbovirus of marine mammals and illustrates that alphaviruses can inhabit Antarctica and that alphaviruses can be transmitted by lice.

Cytokines and chemokines play important roles in both autoimmune and infectious arthritides. Here we describe the cytokines and chemokines induced by Ross River (RR) virus infection of synovial fibroblasts and macrophages in vitro. RR virus is the aetiological agent of epidemic polyarthritis (EPA), a principally acute and chronic rheumatic disease affecting up to 7,000 Australians annually. Infected fibroblasts increased expression of mRNA coding for monocyte chemoattractant protein-1 (MCP-1), interleukin-8 (IL-8), and granulocyte-macrophage colony-stimulating factor. MCP-1, IL-8, macrophage inflammatory protein-2, and to a lesser extent interferon γ-induced protein-10 mRNA were upregulated in infected macrophages. Expression of MCP-1 is consistent with the predominantly monocytic effusion found in EPA synovia.

The serine proteinase inhibitor (serpin) plasminogen activator inhibitor type 2 (PAI-2) is well characterized as an inhibitor of extracellular urokinase-type plasminogen activator. Here we show that intracellular, but not extracellular, PAI-2 protected cells from the rapid cytopathic effects of alphavirus infection. This protection did not appear to be related to an effect on apoptosis but was associated with a PAI-2–mediated induction of constitutive low-level interferon (IFN)-α/β production and IFN-stimulated gene factor 3 (ISGF3) activation, which primed the cells for rapid induction of antiviral genes. This primed phenotype was associated with a rapid development of resistance to infection by the PAI-2 transfected cells and the establishment of a persistent productive infection. PAI-2 was also induced in macrophages in response to viral RNA suggesting that PAI-2 is a virus response gene. These observations, together with the recently demonstrated PAI-2–mediated inhibition of tumor necrosis factor-α induced apoptosis, (a) illustrate that PAI-2 has an additional and distinct function as an intracellular regulator of signal transduction pathway(s) and (b) demonstrate a novel activity for a eukaryotic serpin.

Mycoplasma contamination of two alphavirus isolates and adenovirus 5 was completely removed using a very simple, rapid protocol based on solvent extraction. Treated virus preparations remained free of mycoplasma after 6 months in culture.

Arthritogenic alphaviruses are globally distributed mosquito-borne RNA viruses causing epidemics of polyarthritis/arthralgia, with disease emerging or reemerging and increasingly being reported in travelers. This article summarizes the current knowledge of these diseases, focusing on recent developments in the understanding of Ross River virus disease. RECENT FINDINGS: Alphaviral arthritides have often been blamed for protracted chronic illnesses. However, validated quality-of-life questionnaires and exhaustive searches for differential diagnoses showed that Ross River virus disease, although severe at onset, progressively resolved over 3 to 6 months. Many patients did experience long-term disease lasting more than 12 months, but in nearly all cases this was due to other conditions, primarily unrelated rheumatic conditions or depression. There is no indication that alphaviral arthritides predispose to other conditions; thus, patients whose Ross River virus disease has actually resolved may be underdiagnosed for other conditions. Ross River virus polyarthritis probably arises from inflammation associated with productive viral infections in synovial macrophages, which persist despite neutralizing antibodies and antiviral cytokine responses. Persistence may be facilitated by downregulation of cytokine responses by virus-antibody complexes binding to Fc receptors and induction of interleukin-10. How virus escapes neutralizing antibodies remains unclear but may involve phagocytosis of apoptotic virus-infected cells and infection of the phagocyte via the phagosome. SUMMARY: Diagnosis of alphaviral arthritides is complicated by nonspecific symptoms and the lack of commercial serodiagnostic kits, except for Ross River and Barmah Forest virus infections in Australia. Differential diagnoses should be actively pursued, especially if symptoms persist. Treatment with nonsteroidal anti-inflammatory drugs appears largely effective, with no evidence of long-term sequelae or relapse.

Persistent alphavirus infections in synovial and neural tissues are believed to be associated with chronic arthritis and encephalitis, respectively, and represent likely targets for CD8 + αβ cytotoxic T lymphocytes (CTL). Here we show that the capsid protein is a dominant target for alphavirus-specific CTL in BALB/c mice and that capsid-specific CTL from these mice recognize an H-2K d restricted epitope, QYSGGRFTI. This epitope lies in the highly conserved region of the capsid protein, and QYSGGRFTI-specific CTL were cross reactive across a range of Old World alphaviruses. In vivo the acute primary viraemia of these highly cytopathic viruses was unaffected by QYSGGRFTI-specific CTL. However, in vitro these CTL were able to completely clear virus from macrophages persistently and productively infected with the arthrogenic alphavirus Ross River virus.

Ross River virus (RRV) is the aetiological agent of epidemic polyarthritis (EPA) a predominantly rheumatic disease afflicting up to 5000 Australians annually. We show here for the first time that macrophages can be productively infected by RRV. Subneutralizing titres of anti-RRV IgG (but not IgM) also showed classical antibody-dependent enhancement (ADE) of RRV infection in macrophage and monocyte cell lines. No correlation between development of EPA and the pre-existence of ADE titres was apparent, nor could sera raised against a related arbovirus, Barmah Forest, enhance RRV infection. Tumour necrosis factor-alpha, implicated in the immunopathogenesis of rheumatoid arthritis, was not secreted by RRV-infected monocytes or macrophages. Macrophage cell lines infected with RRV were, however, capable of producing virus for over 50 days. RRV-induced arthritis may therefore be due to the persistent productive infection of macrophages, perhaps established by a brief period of ADE early in infection.

During 1984, 1548 children were admitted to the Yangon [Rangoon] Children's Hospital in Myanmar [Burma] with haemorrhagic fever. No evidence of recent dengue infection was found in 577 of the 803 children from whom paired sera were obtained, raising the possibility of reappearance of Chikungunya virus infection in Myanmar. An enzyme-linked immunosorbent assay ( elisa ) for the detection of anti-Chikungunya virus immunoglobulin M (IgM) antibody was prepared and standardized using only reagents which are commercially available or which could be prepared without the use of sophisticated equipment. While there was 90% agreement between haemagglutination inhibition (HI) tests and the IgM elisa in the diagnosis of acute Chikungunya virus infections, 12 additional patients with stationary anti-Chikungunya virus HI antibody titres could be identified as having acute Chikungunya infections using the elisa . Furthermore, the elisa could identify twice as many patients ( 31 103 ) at the time of admission to hospital as the HI test ( 15 103 ). There was no false positive IgM reaction with the elisa which could be attributed to the presence of rheumatoid factor. Using the test, 103 of a sample of 163 children who presented to the Yangon Children's Hospital with fever/haemorrhagic fever were diagnosed as Chikungunya patients, 4 had possible dual Chikungunya and dengue infections, 16 had dengue, 30 had neither Chikungunya nor dengue infections, and a definitive diagnosis could not be made for 10 patients. Routine use of the elisa would alert authorities to future outbreaks of Chikungunya virus infection and avoid admission to hospital of patients with a non-life-threatening viral disease.