Substrate specificity of avian influenza H5N1 neuraminidase.

Aim: To characterise neuraminidase (NA) substrate specificity of avian influenza H5N1 strains from humans and birds comparing to seasonal influenza virus.

Methods: Avian influenza H5N1 strains from humans and birds were recruited for characterising their NA substrate specificity by using a modified commercial fluorescence Amplex Red assay. This method can identify the preference of α2,6-linked sialic acid or α2,3-linked sialic acid.

Induction of TNF-alpha in human macrophages by avian and human influenza viruses.

The highly pathogenic avian influenza virus H5N1 is known to induce high level of tumor necrosis factor alpha (TNF-alpha) from primary macrophages. However, it is still unclear whether current H5N1 strains also induce high TNF-alpha production, as most of the data were derived from extinct clade 0 H5N1 strain. Here, we show that current clade 1 and 2 H5N1 strains induce variable levels of TNF-alpha that are not necessarily higher than those induced by seasonal influenza viruses.

A simple screening assay for receptor switching of avian influenza viruses.

Background: Adaptation of the receptor-binding preference from alpha2,3- to alpha2,6-linked sialic acid is an essential step for an avian influenza virus to transmit efficiently in human population and become a pandemic virus. The currently available assays for receptor-binding preference are complex and not widely available.

Objectives: A simple high-throughput screening assay will facilitate early detection of a potential pandemic virus, which is crucial for the prevention and control of the possible pandemic.