RESUMEN
Background: Dengue Hemorrhagic Fever is a disease caused by dengue viruses which are transmitted by Aedes aegypti mosquitoes. The disease causes mortality and morbidity in school children, and more recently in adults. Technology assisting clinical diagnosis has been on the rise and recent development of rapid immuno-chromatographic tests (ICT) that allow on-the-site identification of dengue specific antibodies are available. We evaluate a rapid ICT by PANBIO° that displays dengue specific IgM and IgG on paper strips and compare the results with a standard antibody-captured ELISA. Method: A set of plasma specimens from 66 patients admitted into Khon Kaen Hospital were tested blind using the ICT method. The specimens were from a group of dengue infection patients and a group of patients with other febrile illnesses recruited into a study as funded by the Thailand Tropical Diseases Research Program. The project documented the time of collection in relation to the day of fevers and also the immune status (as assessed by dengue IgM/IgG ELISA). Validity of the rapid test was analysed in relation to sensitivity, specificity, predictive value and likelihood ratio.Results: In the sera from patients classified as primary infection, dengue IgM (by ICT) was detected on day 5 (67%) and the detection rate increase on day 6 (75%) to day 7 (100%); but all the specimens on day 2 to day 4 were negative. In secondary dengue infection, dengue IgG (by ICT) was detected on day 3 (33%) and increased from day 4 (68%) to day 7 (88%); all specimens from day 2 were negative. Irrespective of immune classification, specimens collected during day 3 to day 8 of illness, the rapid test deliver moderate sensitivity (76.0%) and low specificity (53.8%) with 94.2% and 18.4% of PPV and NPV respectively; but if the data were analysed covering day 5 to day 8, the sensitivity and specificity were 86.8% and 33.3% respectively. The likelihood ratio was also summarised for the rapid test accuracy. The positive likelihood ratio of rapid test was 1.65 (when specimens from day 3-8 were used) and 1.30 (day 5-8).Conclusion: The rapid test gave positive results in dengue infected patients only after 3 days of fever with moderate sensitivity and low specificity. The test improved its performance in later days of fever. It is therefore recommended that the test should be used and interpreted together with the data of the length of pyrexia.
RESUMEN
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.