ABSTRACT
OBJECTIVE: To conduct an external quality assessment (EQA) of dengue and chikungunya diagnostics among national-level public health laboratories in the Asia Pacific region following the first round of EQA for dengue diagnostics in 2013. METHODS: Twenty-four national-level public health laboratories performed routine diagnostic assays on a proficiency testing panel consisting of two modules. Module A contained serum samples spiked with cultured dengue virus (DENV) or chikungunya virus (CHIKV) for the detection of nucleic acid and DENV non-structural protein 1 (NS1) antigen. Module B contained human serum samples for the detection of anti-DENV antibodies. RESULTS: Among 20 laboratories testing Module A, 17 (85%) correctly detected DENV RNA by reverse transcription polymerase chain reaction (RT-PCR), 18 (90%) correctly determined serotype and 19 (95%) correctly identified CHIKV by RT-PCR. Ten of 15 (66.7%) laboratories performing NS1 antigen assays obtained the correct results. In Module B, 18/23 (78.3%) and 20/20 (100%) of laboratories correctly detected anti-DENV IgM and IgG, respectively. Detection of acute/recent DENV infection by both molecular (RT-PCR) and serological methods (IgM) was available in 19/24 (79.2%) participating laboratories. DISCUSSION: Accurate laboratory testing is a critical component of dengue and chikungunya surveillance and control. This second round of EQA reveals good proficiency in molecular and serological diagnostics of these diseases in the Asia Pacific region. Further comprehensive diagnostic testing, including testing for Zika virus, should comprise future iterations of the EQA.
ABSTRACT
The Oceania region, which includes Australia, New Zealand, Papua New Guinea and the islands of the tropical Pacific Ocean, has historically been free from chikungunya. However, the 2011 outbreak in New Caledonia and the ongoing outbreak in Papua New Guinea have highlighted the risk to other communities in Oceania where there are competent mosquito vectors and permissive social factors and environmental conditions. In this article we discuss the threat to this region that is posed by the recent evolution of the E1:A226V mutant strains of chikungunya virus (CHIKV).
ABSTRACT
Rationale: The capsid (C) protein of dengue virus functions primarily as a building block of the nucleocapsid. During virus replication, C localizes in the cytoplasm as well as nuclei of infected cells. The function of C nuclear localization remains unknown. This study aimed to investigate the localization of C in infected cells undergoing mitosis. Methods: Indirect immunofluorescence analysis was employed. Vero and PS clone D cell lines were infected with dengue viruses for 24-48 hours, fixed, permeabilized and reacted successively with antibodies specific for C and NS1, and fluorochrome-conjugated secondary antibodies. Stained cells were visualized under a fluorescence microscope. Results: During the infection with dengue serotype 2 viruses, C was detected in the cytoplasm and/or nuclei of interphase cells. In the majority of infected mitotic cells, C localized to the cytoplasm with no staining of chromosomes. In the remainder, C was found to associate with the periphery of mitotic chromosomes with less intense staining in the cytoplasm. Association of C with chromosomes, which was observed with recent clinical isolates and laboratory adapted strains, was not restricted to any specific phase of mitosis. Conclusions: Differential localization to the cytoplasm or chromosome in mitotic cells suggests the highly dynamic nature of the C protein.