Epidemiological serosurvey of chikungunya fever post outbreak at Tanjung Sepat, Malaysia.

INTRODUCTION: Chikungunya fever is a mosquito-borne viral disease that usually presents with prominent arthralgia. An outbreak of chikungunya fever was reported in Tanjung Sepat, Malaysia in 2019. The outbreak was limited in size with a low number of cases being reported. The present study sought to determine the possible variables that could have affected the transmission of the infection. METHODOLOGY: A cross-sectional study involving 149 healthy adult volunteers from Tanjung Sepat was performed soon after the outbreak had subsided. All the participants donated blood samples and completed the questionnaires. Laboratory detection of anti-CHIKV IgM and IgG antibodies was performed using enzyme-linked immunoassays (ELISA). Risk factors associated with chikungunya seropositivity were determined using logistic regression. RESULTS: The majority (72.5%, n = 108) of the study participants tested positive for CHIKV antibodies. Only 8.3% (n = 9) of the participants out of all the seropositive volunteers had an asymptomatic infection. Participants who resided with a febrile (p < 0.05, Exp(B) = 2.2, confidence interval [CI] 1.3-3.6) or a CHIKV-diagnosed person (p < 0.05, Exp(B) = 2.1, CI 1.2-3.6) in the same household were found likely to be tested positive for CHIKV antibodies. CONCLUSIONS: Findings from the study support that asymptomatic CHIKV infections and indoor transmission occurred during the outbreak. Hence, widespread community testing and indoor use of mosquito repellent are among the possible measures that can be implemented to reduce CHIKV transmission during an outbreak.

Intracellular translocation of HMGB1 is important for Zika virus replication in Huh7 cells.

Neonatal microcephaly and adult Guillain-Barré syndrome are severe complications of Zika virus (ZIKV) infection. The robustly induced inflammatory cytokine expressions in ZIKV-infected patients may constitute a hallmark for severe disease. In the present study, the potential role of high mobility group box 1 protein (HMGB1) in ZIKV infection was investigated. HMGB1 protein expression was determined by the enzyme-linked immunosorbent assay (ELISA) and immunoblot assay. HMGB1's role in ZIKV infection was also explored using treatment with dexamethasone, an immunomodulatory drug, and HMGB1-knockdown (shHMGB1) Huh7 cells. Results showed that the Huh7 cells were highly susceptible to ZIKV infection. The infection was found to induce HMGB1 nuclear-to-cytoplasmic translocation, resulting in a > 99% increase in the cytosolic HMGB1 expression at 72-h post-infection (h.p.i). The extracellular HMGB1 level was elevated in a time- and multiplicity of infection (MOI)-dependent manner. Treatment of the ZIKV-infected cells with dexamethasone (150 µM) reduced HMGB1 extracellular release in a dose-dependent manner, with a maximum reduction of 71 ± 5.84% (P < 0.01). The treatment also reduced virus titers by over 83 ± 0.50% (P < 0.01). The antiviral effects, however, were not observed in the dexamethasone-treated shHMGB1 cells. These results suggest that translocation of HMGB1 occurred during ZIKV infection and inhibition of the translocation by dexamethasone coincided with a reduction in ZIKV replication. These findings highlight the potential of targeting the localization of HMGB1 in affecting ZIKV infection.

A reverse transcription loop-mediated isothermal amplification for broad coverage detection of Asian and African Zika virus lineages.

BACKGROUND: Early detection of Zika virus (ZIKV) infection during the viremia and viruria facilitates proper patient management and mosquito control measurement to prevent disease spread. Therefore, a cost-effective nucleic acid detection method for the diagnosis of ZIKV infection, especially in resource-deficient settings, is highly required. METHODS: In the present study, a single-tube reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay was developed for the detection of both the Asian and African-lineage ZIKV. The detection limit, strain coverage and cross-reactivity of the ZIKV RT-LAMP assay was evaluated. The sensitivity and specificity of the RT-LAMP were also evaluated using a total of 24 simulated clinical samples. The ZIKV quantitative reverse transcription-polymerase chain reaction (qRT-PCR) assay was used as the reference assay. RESULTS: The detection limit of the RT-LAMP assay was 3.73 ZIKV RNA copies (probit analysis, P ≤ 0.05). The RT-LAMP assay detected the ZIKV genomes of both the Asian and African lineages without cross-reacting with other arthropod-borne viruses. The sensitivity and specificity of the RT-LAMP assay were 90% (95% CI = 59.6-98.2) and 100% (95% CI = 78.5-100.0), respectively. The RT-LAMP assay detected ZIKV genome in 9 of 24 (37.5%) of the simulated clinical samples compared to 10 of 24 (41.7%) by qRT-PCR assay with a high level of concordance (κ = 0.913, P < 0.001). CONCLUSION: The RT-LAMP assay is applicable for the broad coverage detection of both the Asian and African ZIKV strains in resource-deficient settings.