Development of a monoclonal antibody-based lateral flow immunoassay for the detection of benzoic acid in liquid food.

To monitor benzoic acid (BA) residues in liquid food samples, a monoclonal antibody (mAb)-based lateral flow immunoassay (LFA) was developed in this study. First, 2-aminobenzoic acid (2-AA), 3-aminobenzoic acid (3-AA), and 4-aminobenzoic acid (4-AA) were conjugated to BSA and used as immunogens. After cell fusion, mAb 6D8 from 4-AA-BSA performed best with an IC50 value of 0.21 mg L-1 using 3-AA-OVA as a heterogeneous antigen, which represented a 3.4-fold improvement compared with the homogeneous antigen 4-AA-BSA. Subsequently, eight kinds of CGNPs with sizes varying from 20.94 nm to 90.00 nm were synthesized for screening the suitable size to develop a sensitive LFA. Finally, a sensitive LFA based on colloidal gold (23.27 nm) nanoparticles was developed for screening BA with a cut-off value of 4 mg L-1, which could meet the requirement of BA detection in milk, Fanta, Sprite, Coca-Cola, and Smart samples.

[Genetic diversification of avian influenza H5N1 virus in boundary areas of Yunnan province].

OBJECTIVE: To elucidate the genetic diversifications of avian influenza subtype H5N1 viruses in the boundary regions of Yunnan province during 2009 to July, 2011. METHODS: Swab samples were collected from foreign poultry and wild birds in boundary regions of Yunnan province during 2009 to July, 2011 and tested by H5/N1 subtype-specific multiplex RT-PCR. The HA genes of H5N1 virus from the positive samples were amplified by RT-PCR and cloned into pMD18-T vectors for sequencing. Both alignment and phylogenetic analysis were performed with sequences of the known reference strains. RESULTS: Fifteen different HA sequences were obtained from 36 representative positive samples and could be divided into 2 distinct Clades (2.3.2 and 2.3.4). Through phylogenetic analysis, Clade 2.3.2 and 2.3.4 could then be further divided into 3 (II-1 to II-3) and 2 smaller clades (I-1 and I-2), respectively. The viruses of Clade 2.3.2 II-1 and II-2 were new variant strains of H5N1 virus. The cleavage sites of HA from positive samples all possessed molecular characterization of highly pathogenic avian influenza virus. Mutation of key amino acids had been found among receptor binding sites, potential glycosylation sites, neutralizing epitopes and others. CONCLUSION: It seemed evident that the H5N1 subtype viruses showed genetic diversifications and had undergone the evolution progress of multi-clade (2.3.2, 2.3.4) to single calde (2.3.2) in the boundary regions of Yunnan province, during 2009 to July, 2011.