High levels of interferon alpha in the sera of children with dengue virus infection

We measured the levels of interferon alpha (IFN alpha) in the sera of Thai children hospitalized with dengue hemorrhagic fever (DHF) or dengue fever (DF) to examine the role of IFN alpha in dengue virus infections of humans. The percentage of patients who had detectable levels of IFN alpha (> or = 3 U/ml) was higher in patients with DHF (80%, P < 0.001) and in patients with DF (60%, P < 0.001) than in healthy Thai children (7%). The levels of IFN alpha were higher in patients with DHF and in patients with DF on the first few days after the onset of fever than in healthy Thai children. The average levels of IFN alpha in patients with DHF were high two days before defervescence, decreasing gradually until the day of defervescence. There was a subset of patients with DHF who had increasing levels of IFN alpha after defervescence. However, the levels of IFN alpha in patients with DF were not high after fever subsided. The levels of IFN alpha were not different among children with DHF grades 1, 2 and 3. Among patients with DHF, T lymphocytes were activated to a higher degree in high IFN alpha producers than in low IFN alpha producers. These results indicate that similarly high levels of IFN alpha are produced in vivo during the acute stages of DHF and DF, and that high levels of IFN alpha remain after fever subsides in some patients with DHF, but not in patients with DF.     

Evaluation of a rapid immunochromatographic test for diagnosis of dengue virus infection

A rapid (<7-min) immunochromatographic test for immunoglobulin M (IgM) and IgG antibodies to dengue viruses was evaluated by using hospital admission and discharge sera from 124 patients. The reference laboratory diagnosis was based on the results of virus isolation, hemagglutination-inhibition assay (HAI), and enzyme immunoassay (EIA). By the standard assays, patients experienced primary dengue virus infection (n = 30), secondary dengue virus infection (n = 48), Japanese encephalitis (JE) virus infection (n = 20), or no flavivirus infection (n = 26). The rapid test demonstrated 100% sensitivity in the diagnosis of dengue virus infection and was able to distinguish between primary and secondary dengue virus infections through the separate determinations of IgM and IgG. For all patients with primary dengue virus infection a positive test for IgM to dengue virus and a negative test for IgG to dengue virus were obtained, whereas for 46 of 48 patients (96%) with secondary dengue virus infection, a positive test for IgG to dengue virus with or without a positive test for IgM to dengue virus was obtained. The remaining two patients with secondary dengue virus infection had positive IgM test results and negative IgG test results. Furthermore, the rapid test was positive for patients confirmed to be infected with different dengue virus serotypes (12 infected with dengue virus serotype 1, 4 infected with dengue virus serotype 2, 3 infected with dengue virus serotype 3, and 2 infected with dengue virus serotype 4). The specificity of the test for nonflavivirus infections was 88% (3 of 26 positive), while for JE virus infections the specificity of the test was only 50% (10 of 20). However, most patients with secondary dengue virus infection were positive for both IgM and IgG antibodies to dengue virus, while no patients with JE virus infection had this profile, so cross-reactivity was only a concern for a small proportion of patients with secondary dengue infections. The rapid test demonstrated a good correlation with the reference EIA and HAI and should be useful for the rapid diagnosis of dengue virus infections.     

Poliomyelitis-like illness due to Japanese encephalitis virus

BACKGROUND: Acute flaccid paralysis remains common among Vietnamese children despite a pronounced fall in the incidence of poliomyelitis. METHODS: During 1995, all 22 children presenting with acute flaccid paralysis to a referral centre in Ho Chi Minh City, Vietnam, had virological cultures and antibody measurements done on serum, cerebrospinal fluid, and faeces. A year later the children were reassessed and electrophysiological studies were done. FINDINGS: Wild poliovirus type 1 was isolated from the faeces of only one patient, and non-polio enteroviruses from three patients. 12 (55%) of the 22 children with acute flaccid paralysis had evidence of acute Japanese encephalitis virus (JEV) infection, compared with only one (1%) of 88 age-matched hospital controls (children with diphtheria; p<0.0001). Compared with JEV-negative patients, weakness in JEV-infected children was more rapid in onset, tended to be asymmetrical, but was less likely to involve the arms. All 12 children with JEV infection were febrile at the onset of weakness, seven had acute retention of urine, and ten had CSF pleiocytosis. Seven of eight JEV-negative patients met the case-definition of Guillain-Barré syndrome, compared with only one of 12 JEV-positive children. At follow-up, patients with JEV infection had greater disability and were more likely to have muscle wasting than were JEV-negative children. Nerve conduction and electromyographic studies indicated damage to the anterior horn cells. INTERPRETATION: JEV causes an acute flaccid paralysis in children that has similar clinical and pathological features to poliomyelitis. In endemic areas, children with acute flaccid paralysis should be investigated for evidence of JEV infection.     

Trimethylsilyl‐substituted triazole‐based ligand for copper‐mediated single‐electron transfer living radical polymerization of methyl methacrylate

The tripodal ‘click’ compound tris(4‐trimethylsilylmethyl‐1,2,3‐triazolylmethyl)amine (TTTA) was prepared and investigated as a ligand for copper‐catalysed single‐electron transfer living radical polymerization of methyl methacrylate (MMA). Bulk polymerizations catalysed by Cu⁰/CuBr₂/TTTA with a molar ratio of [MMA]₀/[ethyl‐2‐bromoisobutyrate]₀/[CuBr₂]₀/[TTTA]₀ = 200:2:1:1 and a 1.0 × 1.0 cm² Cu⁰ sheet were fast and well controlled (76% conversion with M_w/M_n = 1.19 after 3.5 h). Greater amounts of added air generally gave slower polymerizations although M_w/M_n remained low (<1.3) even when the polymerization was carried out under aerobic conditions. Decreasing initial concentrations of the Cu⁰/CuBr₂/TTTA catalyst system or polymerization temperatures also resulted in slower polymerizations and yielded polymers with broader dispersity. Kinetic studies in the temperature range 40–90 °C revealed an apparent activation energy of 22.6 kJ mol^?1. © 2014 Society of Chemical Industry     

Detection of specific antibodies in saliva during dengue infection

Saliva was collected prospectively from patients presenting with suspected dengue infection 4 to 8 days after the onset of symptoms and assayed by a commercial dengue immunoglobulin M (IgM) and IgG capture enzyme-linked immunosorbent assay (ELISA) (PanBio Dengue Duo ELISA). Laboratory diagnosis was based on virus isolation and on hemagglutination inhibition (HAI) assay and an in-house IgM and IgG capture ELISA. With a positive result defined as either salivary IgM or IgG levels above the cutoff value, an overall sensitivity of 92% was obtained for both primary- and secondary-dengue patients (22 of 24), while no patients with non-flavivirus infections (n = 11) and no healthy laboratory donors (n = 17) showed elevation of salivary antidengue antibody (100% specificity). Salivary IgG levels correlated well with serum HAI titer (r = 0.78), and salivary IgG levels could be used to distinguish between primary- and secondary-dengue virus infections.     

Rapid diagnosis of Japanese encephalitis by using an immunoglobulin M dot enzyme immunoassay

Japanese encephalitis (JE) occurs in rural settings in southern and eastern Asia, where diagnostic facilities are limited. For the diagnosis of JE virus (JEV) infection, we developed a nitrocellulose membrane-based immunoglobulin M (IgM) capture dot enzyme immunoassay (MAC DOT) that is rapid, simple to use, requires no specialized equipment, and can distinguish JEV from dengue infection. In a prospective field study in southern Vietnam, 155 cerebrospinal fluid (CSF) and 341 serum samples were collected from 111 children and 83 adults with suspected encephalitis. The JEV MAC DOT, performed on site, was scored visually from negative to strongly positive by two observers, and the results were compared subsequently with those of the standard IgM capture enzyme-linked immunosorbent assay. For the 179 patients with adequate specimens, the MAC DOT correctly identified 59 of 60 JEV-positive patients and 118 of 119 JEV-negative patients (sensitivity [95% confidence intervals], 98.3% [92.1 to 99.91%]; specificity, 99.2% [95.9 to 100.0%]; positive predictive value, 0.98; negative predictive value, 0.99). The MAC DOT also correctly identified three patients with dengue encephalopathy. Admission specimens were positive for 73% of JE patients. Interobserver agreement for MAC DOT diagnosis was excellent (kappa = 0.94). The JEV MAC DOT is a simple and reliable rapid diagnostic test for JE in rural hospitals.