Enhanced susceptibility of nasal polyp tissues to avian and human influenza viruses

Background

Influenza viruses bind and infect respiratory epithelial cells through sialic acid on cell surface. Differential preference to sialic acid types contributes to host- and tissue-tropism of avian and seasonal influenza viruses. Although the highly pathogenic avian influenza virus H5N1 can infect and cause severe diseases in humans, it is not efficient in infecting human upper respiratory tract. This is because of the scarcity of its receptor, α2,3-linked sialic acid, in human upper airway. Expression of sialic acid can be influenced by various factors including inflammatory process. Allergic rhinitis and nasal polyp are common inflammatory conditions of nasal mucosa and may affect expression of the sialic acid and susceptibility to influenza infection.

Methodology/Principal Finding

To test this hypothesis, we detected α2,3- and α2,6-linked sialic acid in human nasal polyp and normal nasal mucosal tissues by lectin staining and infected explants of those tissues with avian influenza viruses H5N1 and seasonal influenza viruses. We show here that mucosal surface of nasal polyp expressed higher level of α2,3- and α2,6-linked sialic acid than normal nasal mucosa. Accordingly, both H5N1 avian influenza viruses and seasonal influenza viruses replicated more efficiently in nasal polyp tissues explants.

Conclusions/Significance

Our data suggest a role of nasal inflammatory conditions in susceptibility to influenza infection, especially by avian influenza viruses, which is generally inefficient in infecting human upper airway. The increased receptor expression may contribute to increased susceptibility in some individuals. This may contribute to the gradual adaptation of the virus to human population.     

Solventogenic-cellulolytic clostridia from 4-step-screening process in agricultural waste and cow intestinal tract

A clostridial bacterium is accepted to be one of the important and efficient microorganisms for the application in fuel fermentation process. However, the lack of cellulolytic activity of cellulosome in this organism appears to be one of the main important problems for efficient production of the fuel. It is therefore interesting to search for the genetic resource of natural clostridial bacteria for the application in bioengineering. Presently, Clostridium species selection and identification are based on various physiological properties tests. This article developed the way for a 4-step screening process via mainly three criteria and 16S rDNA identification. In this study, solvent-producing clostridial bacteria were successfully isolated from decomposed sources, cow feaces, and dry grass in Thailand. Anaerobes were screened by cellulolytic activity and butanol tolerance in selective media that composed of basal media supplemented with 2% cellulose and 5% butanol. Thirty isolates of cellulolytic and butanol-tolerant anaerobic bacteria were obtained from screening in this medium. Fifteen isolates were rapidly classified as in the class Clostridia by three selected criteria (endospore formation, sulfite-reducing ability, and metabolic products). Secondary metabolites of the bacteria such as acetone, butanol and ethanol were varied depending on the process. Clostridial differential medium was used as a genus identification tool. Finally, PCR-amplified gene fragments coding for 16S rDNA were analyzed as a key to identify bacteria species. This process can be used to screen and identify Clostridium species in short period. Cellulosome and non-cellulosome cellulases productivity were analyzed. The results revealed that the selected cellulolytic strains (such as Fea-PA) exhibited EngD non-cellulosome cellulase activity especially endoglucanase activity on carboxymethyl cellulose. The selective system in this research was appropriate for the screening of Clostridiaceae in a similarity range between 83% and 100%.     

NirK and nirS Nitrite reductase genes from non-agricultural forest soil bacteria in Thailand

The genetic heterogeneity of the nitrite reductase gene (nirK and nirS) fragments from denitrifying prokaryotes in a non-agricultural forest soil in Thailand was investigated using soil samples from the Plant Germplasm-Royal Initiation Project area in Kanchanaburi Province, Thailand. Soil bacteria were screened for denitrification activity and 13 (from 211) positive isolates were obtained and further evaluated for their ability to reduce nitrate and to accumulate or reduce nitrite. Three species with potentially previously unreported denitrifying activities were recorded. Analysis of the partial nirK and nirS sequences of these 13 strains revealed a diverse sequence heterogeneity in these two genes within the same environment and even potentially within the same host species, the potential existence of lateral gene transfer and the first record of both nirK and nirS homologues in one bacterial species. Finally, isolates of two species of bacteria (Corynebacterium propinquum and Micrococcus lylae) are recorded as denitrifiers for the first time.