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.

Intrinsic and tunable ferromagnetism in Bi0.5Na0.5TiO3 through CaFeO3-δ modification

New (1-x)Bi_0.5Na_0.5TiO₃ + xCaFeO_3-δ solid solution compounds were fabricated using a sol–gel method. The CaFeO_3-δ materials were mixed into host Bi_0.5Na_0.5TiO₃ materials to form a solid solution that exhibited similar crystal symmetry to those of Bi_0.5Na_0.5TiO₃ phases. The random distribution of Ca and Fe cations in the Bi_0.5Na_0.5TiO₃ crystals resulted in a distorted structure. The optical band gaps decreased from 3.11 eV for the pure Bi_0.5Na_0.5TiO₃ samples to 2.34 eV for the 9 mol% CaFeO_3-δ-modified Bi_0.5Na_0.5TiO₃ samples. Moreover, the Bi_0.5Na_0.5TiO₃ samples exhibited weak photoluminescence because of the intrinsic defects and suppressed photoluminescence with increasing CaFeO_3-δ concentration. Experimental and theoretical studies via density functional theory calculations showed that pure Bi_0.5Na_0.5TiO₃ exhibited intrinsic ferromagnetism, which is associated with the possible presence of Bi, Na, and Ti vacancies and Ti³⁺-defect states. Further studies showed that such an induced magnetism by intrinsic defects can also be enhanced effectively with CaFeO_3-δ addition. This study provides a basis for understanding the role of secondary phase as a solid solution in Bi_0.5Na_0.5TiO₃ to facilitate the development of lead-free ferroelectric materials.

Electronic and Optical Properties of Single Wall Carbon Nanotubes

In this article, we overview our recent theoretical works on electronic and optical properties of carbon nanotubes by going from the background to the perspectives. Electronic Raman spectra of metallic carbon nanotubes give a new picture of Raman processes. Thermoelectricity of semiconducting nanotubes gives a general concept of the confinement effect on the thermoelectric power factor. Selective excitation of only a single phonon mode is proposed by the pulsed train technique of coherent phonon spectroscopy. Occurrence of both two and four fold degeneracy in the carbon nanotube quantum dot is explained by difference group velocities and the intra/inter valley scattering near the hexagonal corner of the Brillouin zone.

Nutritional status of middle-aged Vietnamese in Ho Chi Minh City

OBJECTIVE

To investigate the nutritional status of middle-aged Vietnamese in Ho Chi Minh City.

METHODS

A cross-sectional survey in 300 Vietnamese aged 40 to 59 years (113 men, 187 women) was conducted in an urban, suburban and rural area of Ho Chi Minh City based on interviews that included a 24-hour dietary recall, food frequency questionnaire, and a short socioeconomic questionnaire. Anthropometry and blood pressure were measured, and blood was collected for serum protein and lipid analysis.

RESULTS

A high prevalence of underweight (BMI < 18.5) was observed in the rural and suburban populations (35% and 23%, respectively), and overweight (BMI > or = 25) was observed in the urban population (18%). A high percentage of serum total cholesterol (TC) below 150 mg/dL was observed in the rural and suburban areas (43% and 37%, respectively). By contrast, the prevalence of TC above 220 mg/dL was twofold higher in the urban and suburban residents (13% and 12%, respectively) than in rural residents (6%). More than 80% of urban residents were of medium or high-income status, whereas 61% of suburban residents were of medium-income status and 66% of rural residents were of low-income status.

CONCLUSIONS

The nutritional status of middle-aged Vietnamese in Ho Chi Minh City was characterized by undernutrition in 35% of the low-income population and by overnutrition in 18% the high-income population. Undenutrition was still a public health problem in the rural area whereas overnutrition started to become a noteworthy problem in the urban area. The suburban area suffered from both under- and overnutrition problems. Low lipid intake was the most important problem related to undernutrition in middle-aged residents of Ho Chi Minh City.

Liver histopathology and biological correlates in five cases of fatal dengue fever in Vietnamese children

We studied five fatal cases of dengue haemorrhagic fever (DHF), confirmed using the reverse transcriptase-polymerase chain reaction (RT-PCR) method, in Vietnamese children. The liver seems to be a target for dengue virus, so postmortem examinations were performed to investigate elementary lesions, local recruitment of inflammatory cells and whether the virus was present in target cells of the liver. We detected severe, diffuse hepatitis with midzonal necrosis and steatosis in two patients, focal areas of necrosis in two patients, and normal histology in one patient. Dengue virus antigen was detected using immunohistochemistry in hepatocytes from necrotic areas in four cases. There was no recruitment of polymorphonuclear cells, and no lymphocytes were detected in the liver lesions of patients who died from DHF. Lymphocytic infiltration occurred in only one hepatitis B virus-positive patient, with no signs of chronic hepatitis. Kupffer cells had mostly been destroyed in cases with focal or severe necrosis. TUNEL tests were positive in necrotic areas, with positive cells forming clusters, suggesting that an apoptotic mechanism was involved. Thus, we suggest that the hepatocyte and Kupffer cells may be target cells supporting virus replication and that the councilman body is an apoptotic cell, as in the pathogenesis of yellow fever.

Clinical and neurophysiological study of the effects of multiple doses of artemisinin on brain-stem function in Vietnamese patients

The qinghaosu (artemisinin) group of drugs is the most important new class of antimalarials developed in the last fifty years. Although there has been no clinical evidence of neurotoxicity, an unusual pattern of damage to specific brain-stem nuclei has been reported in experimental animals receiving high doses of arteether or artemether. Detailed clinical examinations, audiometry, and brain stem auditory evoked potentials (BSAEPs) were assessed in 242 Vietnamese subjects who had previously received up to 21 antimalarial treatment courses of artemisinin or artesunate alone and 108 controls from the same location who had not received these drugs. There was no evidence of a drug effect on the clinical or neurophysiological parameters assessed. In this population there was no clinical or neurophysiological evidence of brain-stem toxicity that could be attributed to exposure to artemisinin or artesunate.

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.

Management of multiple drug-resistant malaria in Viet Nam

Malaria is still the most common infectious cause of mortality and morbidity in Viet Nam as it is in many developing countries in the tropics. The presence of resistance to available antimalarials and compliance in the target population are factors that influence the choice of drugs and regimens. In order to develop an ideal treatment for malaria, we conducted several clinical trials in patients with the disease in different settings. The results of these trials suggest that a combination of single dose artemisinin (or its derivatives) and mefloquine is the most effective, safe and practical treatment for acute non-complicated malaria due to multidrug-resistant Plasmodium falciparum. Concerning severe and complicated malaria, parenteral or rectal multi-doses of artemisinin or analogues are recommended due to their rapid parasite clearance time and other possible anti-cytoadherence effects. With its rapid parasite clearance, very early treatment of uncomplicated cases with artemisinin (and derivatives), especially at a health post level may help to prevent the development of complications, consequently reducing the number of severe cases and the malaria mortality rate.