Development of an enzyme-linked immunosorbent assay for Getah virus infection in horses using recombinant E2 protein as an antigen.

Getah virus causes fever, skin eruptions, and limb edema in horses. For a high-throughput and time-saving method for serodiagnosis, we explored immunogenic antigens of Getah virus, and established an enzyme-linked immunosorbent assay (ELISA) using a recombinant protein. Western blot analysis using sera from infected horses showed strong reaction with viral antigens around 46 kDa corresponding to E1 or E2 glycoproteins. Recombinant E2 (rE2) protein reacted more strongly with infected horse sera than did rE1 protein in both Western blotting and ELISA. In ELISA using rE2 protein (rE2-ELISA), for all horses experimentally infected with Getah virus (n = 7), optical density (OD) exceeded the cutoff value at 14 days post-infection. ODs in five of nine vaccinated horses also slightly exceeded the cutoff value after vaccination. Among naturally infected horses (n = 28), 24 were seronegative in the acute sera, which turned seropositive in the convalescent sera. For the four horses seropositive in the acute sera, an endpoint method with serial dilutions of paired sera detected a ≥4-fold increase in titer. In conclusion, we established rE2-ELISA that could detect horse antibodies against Getah virus after experimental and natural infections; this should be useful in the diagnosis and surveillance of Getah virus infection.

Arthritogenic alphaviral infection perturbs osteoblast function and triggers pathologic bone loss.

Arthritogenic alphaviruses including Ross River virus (RRV), Sindbis virus, and chikungunya virus cause worldwide outbreaks of musculoskeletal disease. The ability of alphaviruses to induce bone pathologies remains poorly defined. Here we show that primary human osteoblasts (hOBs) can be productively infected by RRV. RRV-infected hOBs produced high levels of inflammatory cytokine including IL-6. The RANKL/OPG ratio was disrupted in the synovial fluid of RRV patients, and this was accompanied by an increase in serum Tartrate-resistant acid phosphatase 5b (TRAP5b) levels. Infection of bone cells with RRV was validated using an established RRV murine model. In wild-type mice, infectious virus was detected in the femur, tibia, patella, and foot, together with reduced bone volume in the tibial epiphysis and vertebrae detected by microcomputed tomographic (µCT) analysis. The RANKL/OPG ratio was also disrupted in mice infected with RRV; both this effect and the bone loss were blocked by treatment with an IL-6 neutralizing antibody. Collectively, these findings provide previously unidentified evidence that alphavirus infection induces bone loss and that OBs are capable of producing proinflammatory mediators during alphavirus-induced arthralgia. The perturbed RANKL/OPG ratio in RRV-infected OBs may therefore contribute to bone loss in alphavirus infection.

Effectiveness of chloroquine and inflammatory cytokine response in patients with early persistent musculoskeletal pain and arthritis following chikungunya virus infection.

OBJECTIVE: To evaluate whether chloroquine (CQ) is more effective than meloxicam for treating early musculoskeletal pain and arthritis following acute chikungunya (CHIK) virus infection. METHODS: During the 2006 CHIK epidemic, 509 rural community cases of acute CHIK virus infection were identified in the district of Sholapur in India. Seventy consenting adult patients (seropositive for IgM/IgG anti-CHIK antibody) with early persistent musculoskeletal pain and arthritis were randomized into a 24-week, 2-arm, parallel efficacy trial of CQ (250 mg/day) and meloxicam (7.5 mg/day). Assessors completed a rheumatology evaluation in a blinded manner and collected blood samples in the patients' homes, as per protocol. Laboratory parameters included serum cytokine assay (interleukin-6 [IL-6], interferon-γ [IFNγ], tumor necrosis factor α, CXCL10/IFNγ-inducible protein 10, and IL-13). Twenty-two patients who failed to meet the eligibility criteria (low pain cohort) were also followed up with similar evaluations. An intent-to-treat analysis was completed. At baseline, the 2 groups (38 patients randomized to receive CQ and 32 patients randomized to receive meloxicam) were well matched. RESULTS: There were no significant efficacy differences between the meloxicam group and the CQ group (mean changes in the visual analog scale score for pain -3.9 and -4.2, respectively). Patients improved significantly. Cytokine levels remained several-fold increased, were disproportionate to the clinical response, and were not different from those in the low pain cohort. Seven patients withdrew. Adverse events were mild and infrequent. CONCLUSION: This exploratory community intervention trial failed to identify an advantage of CQ over meloxicam to treat early musculoskeletal pain and arthritis following acute CHIK virus infection, but therapeutic efficacy of CQ was not ruled out. The inflammatory cytokine response was intense and was not consistent with clinical status.

Chikungunya fever outbreak, Bhutan, 2012.

In 2012, chikungunya virus (CHIKV) was reported for the first time in Bhutan. IgM ELISA results were positive for 36/210 patient samples; PCR was positive for 32/81. Phylogenetic analyses confirmed that Bhutan CHIKV belongs to the East/Central/South African genotype. Appropriate responses to future outbreaks require a system of surveillance and improved laboratory capacity.

Molecular epidemiology of Chikungunya virus: mutation in E1 gene region.

Chikungunya virus is a mosquito-transmitted RNA virus and emerging as a pathogen that has a major public health impact because of the high morbidity including high fever, headache, rash, nausea, vomiting, myalgia, arthralgia with or without neurological manifestation or fulminant hepatitis. One hundred fifty-one patient samples were analyzed during the years 2006-2008, and compared conventional tests and CCRT-PCR (cell culture RT PCR). The conventional tests included ELISA, inoculation into C6/36 cell line and CPE were examined by PCR after RNA extraction. A total of 20/151 (13.2%), 8/151 (5.29%) and 7/151 (4.6%) samples were found to be positive by ELISA, cell culture and PCR, respectively. While 7/20 (35%) of the samples were positive by CCRT_PCR when ELISA 20 positive samples were detected. A total of 5/7 positive strains were sequenced in the E1 gene region. Remarkable changes (M269V, D284E, P294L, S295F, A316V, V322A, and C328W) were observed in the membrane fusion glycoprotein E1. These unique molecular features of the isolates with the continuing epidemic demonstrated high evolutionary potential and thereby indicating higher virulence.

Early neutralizing IgG response to Chikungunya virus in infected patients targets a dominant linear epitope on the E2 glycoprotein.

Chikungunya virus (CHIKV) and related arboviruses have been responsible for large epidemic outbreaks with serious economic and social impact. The immune mechanisms, which control viral multiplication and dissemination, are not yet known. Here, we studied the antibody response against the CHIKV surface antigens in infected patients. With plasma samples obtained during the early convalescent phase, we showed that the naturally-acquired IgG response is dominated by IgG3 antibodies specific mostly for a single linear epitope 'E2EP3'. E2EP3 is located at the N-terminus of the E2 glycoprotein and prominently exposed on the viral envelope. E2EP3-specific antibodies are neutralizing and their removal from the plasma reduced the CHIKV-specific antibody titer by up to 80%. Screening of E2EP3 across different patient cohorts and in non-human primates demonstrated the value of this epitope as a good serology detection marker for CHIKV infection already at an early stage. Mice vaccinated by E2EP3 peptides were protected against CHIKV with reduced viremia and joint inflammation, providing a pre-clinical basis for the design of effective vaccine against arthralgia-inducing CHIKV and other alphaviruses.

High concentrations of circulating interleukin-6 and monocyte chemotactic protein-1 with low concentrations of interleukin-8 were associated with severe chikungunya fever during the 2009-2010 outbreak in Thailand.

The recent outbreak of Chikungunya virus in Thailand caused a rheumatic fever associated with considerable morbidity and fatalities. Thus, it is important to identify biomarker(s) of severe disease induced by this threatening arbovirus. Putative biomarkers in cases of chikungunya fever during an outbreak in the southern part of Thailand in 2009-2010 were identified. Sixty-two patients who had developed fever and myalgia, with or without arthralgia/arthritis, were enrolled and grouped into severe chikungunya fever (CHIKF) (n= 15), mild CHIKF (n= 20) and non-CHIKF (n= 27) to investigate circulating immunological mediators that might serve as markers of severity. Blood samples were taken at presentation (day 1) and 30 days later (day 30) and plasma concentrations of interleukin (IL)-1ß, IL-6, IL-8, IL-17, tumor necrosis factor-alpha, monocyte chemotactic protein-1 (MCP-1), matrix metalloproteinase-1, tissue inhibitor of matrix metalloproteinase-1 and viral load were measured by ELISA. On day 1, severe CHIKF and mild CHIKF groups had viral loads of 10(8.5) and 10(8.3) of RNA copies/mL, respectively. At presentation, all CHIKF patients had circulating concentrations of IL-6 and MCP-1 higher than did non-CHIKF patients, whereas amongst the CHKF patients, the severe CHIKF patients had higher IL-6 concentrations than did mild CHIKF patients. Interestingly, severe CHIKF patients had significantly lower concentrations of circulating IL-8 than the other groups of patients, suggesting that high concentrations of IL-6 and MCP-1 with low concentrations of IL-8 may be a determinant of severe chikungunya virus infection.

Protection from arthritis and myositis in a mouse model of acute chikungunya virus disease by bindarit, an inhibitor of monocyte chemotactic protein-1 synthesis.

Chikungunya virus (CHIKV) is associated with outbreaks of infectious rheumatic disease in humans. Using a mouse model of CHIKV arthritis and myositis, we show that tumor necrosis factor-α, interferon-γ, and monocyte chemotactic protein 1 (MCP-1) were dramatically induced in tissues from infected mice. The same factors were detected in the serum of patients with CHIKV-induced polyarthralgia and polyarthritis, with MCP-1 levels being particularly elevated. Bindarit (MCP inhibitor) treatment ameliorated CHIKV disease in mice. Histological analysis of muscle and joint tissues showed a reduction in inflammatory infiltrate in infected mice treated with bindarit. These results suggest that bindarit may be useful in treating CHIKV-induced arthritides in humans.

Active infection of human blood monocytes by Chikungunya virus triggers an innate immune response.

Chikungunya virus (CHIKV) is an alphavirus that causes chronic and incapacitating arthralgia in humans. To date, interactions between the immune system and the different stages of the virus life cycle remain poorly defined. We demonstrated for the first time that CHIKV Ags could be detected in vivo in the monocytes of acutely infected patients. Using in vitro experimental systems, whole blood and purified monocytes, we confirmed that monocytes could be infected and virus growth could be sustained. CHIKV interactions with monocytes, and with other blood leukocytes, induced a robust and rapid innate immune response with the production of specific chemokines and cytokines. In particular, high levels of IFN-alpha were produced rapidly after CHIKV incubation with monocytes. The identification of monocytes during the early phase of CHIKV infection in vivo is significant as infected monocyte/macrophage cells have been detected in the synovial tissues of chronically CHIKV-infected patients, and these cells may behave as the vehicles for virus dissemination. This may explain the persistence of joint symptoms despite the short duration of viremia. Our results provide a better understanding on the basic mechanisms of infection and early antiviral immune responses and will help in the development of future effective control strategies.