Longitudinal sampling is required to maximize detection of intrahost A/H3N2 virus variants.

Seasonal human influenza viruses continually change antigenically to escape from neutralizing antibodies. It remains unclear how genetic variation in the intrahost virus population and selection at the level of individual hosts translates to the fast-paced evolution observed at the global level because emerging intrahost antigenic variants are rarely detected. We tracked intrahost variants in the hemagglutinin and neuraminidase surface proteins using longitudinally collected samples from 52 patients infected by A/H3N2 influenza virus, mostly young children, who received oseltamivir treatment. We identified emerging putative antigenic variants and oseltamivir-resistant variants, most of which remained detectable in samples collected at subsequent days, and identified variants that emerged intrahost immediately prior to increases in global rates. In contrast to most putative antigenic variants, oseltamivir-resistant variants rapidly increased to high frequencies in the virus population. Importantly, the majority of putative antigenic variants and oseltamivir-resistant variants were first detectable four or more days after onset of symptoms or start of treatment, respectively. Our observations demonstrate that de novo variants emerge, and may be positively selected, during the course of infection. Additionally, based on the 4-7 days post-treatment delay in emergence of oseltamivir-resistant variants in six out of the eight individuals with such variants, we find that limiting sample collection for routine surveillance and diagnostic testing to early timepoints after onset of symptoms can potentially preclude detection of emerging, positively selected variants.

Randomized comparison of oxygen mask treatment vs. nasal continuous positive airway pressure in dengue shock syndrome with acute respiratory failure.

Dengue hemorrhagic fever (DHF) is caused by dengue virus. Patients with DHF grade 3-4, termed Dengue Shock Syndrome (DSS), may develop acute respiratory failure after initial fluid resuscitation. Previously, these patients were treated with oxygen on a nasal cannula, or if necessary with tracheal intubation and mechanical ventilation. In the present prospective randomized study, we compared the effectiveness of oxygen treatment administered by a face mask vs. nasal continuous positive airway pressure (NCPAP). Morbidity, mortality, and supportive treatment was evaluated. Thirty-seven patients with DSS complicated by respiratory failure were enrolled. On admission and after 30 min of treatment, clinical and paraclinical data were obtained. Chest X-ray revealed pleural effusion in 92 per cent and showed interstitial oedema in 33 per cent. After 30 min of treatment the respiratory rate decreased significantly in the NCPAP group (p < 0.05), while SaO2 and PaO2 increased in both groups (p < 0.01). However, subsequently a significant difference of unresponsiveness to treatment between the oxygen mask group and the NCPAP group (13/19 vs. 4/18,p < 0.01) was noted. Complications of NCPAP or oxygen mask treatment were not documented. We conclude that NCPAP is useful in improving the management of acute respiratory failure in children with DHF/DSS in dengue-endemic areas.

Selenium-containing tRNAs from Clostridium sticklandii. Cochromatography of seleno-tRNA I with L-VALYL-tRNA.

It has been previously shown that Clostridium sticklandii specifically synthesized three readily separable 75Se-labeled tRNAs, designated seleno-tRNAs I, II and III, and the partially purified seleno-tRNA II cochromatographed with L-prolyl-tRNA on DEAE-Sephadex A-50 (Chen, C.S. and Stadtman, T.C. (1980) Proc. Natl. Acad. Sci. U.S.A. 77, 1403-1407). In the present study a highly purified 75Se-labeled tRNA I was obtained by chromatography on benzoylated DEAE-cellulose, DEAE-Sephadex A-50 and Sepharose 4B. The 75Se-labeled tRNA I cochromatographed with an L-valine-accepting species on DEAE-Sephadex A-50 and Sepharose 4B. Addition of a 285-fold molar excess of unlabeled L-valine to the L-valine acceptor activity assay mixture markedly decreased the amount of L-[14C]valine bound to seleno-tRNA I.