[Colloidal gold immunochromatographic strip for rapid detection of Haemophilus influenzae]

To establish a novel colloidal gold immunochromatography assay (GICA) for rapid, sensitive and accurate detection of Haemophilus influenzae infection by using the outer membrane protein P6 as detection target. First, the linear antigen epitope located in the extracellular domain of the P6 protein (GenBank accession number: AGH02799) was predicted by bioinformatics analysis. The region (62-75 aa of the protein) with strong antigen specificity was chosen and synthesized. Two rabbits were then immunized by the polypeptides (14 aa) for production of polyclonal antibodies. Then, the recombinant P6 proteins were also obtained to produce polyclonal antibodies. Finally, based on the two antibodies, a novel colloidal GICA for detection of Haemophilus influenzae infection was established and the specificity, sensitivity, repeatability and stability of this method were evaluated. At the same time, the method was tested in clinical simulation, and the plate culture method was used to verify its accuracy. The test strip for Haemophilus influenzae infection was successfully prepared. The detection limit of the test strip was as low as 1×105 CFU/mL and the whole process can be completed within 15 minutes. The strip specifically recognized Haemophilus influenzae and did not react with nine of other common respiratory pathogens such as Streptococcus pneumoniae, Moraxella catarrhalis, Mycoplasma pneumonia, and Legionella pneumophila. And the strips could be stored at 25 °C for at least 6 months without losing sensitivity or specificity. The coincidence rate between the results of 200 clinical samples and the plate culture method was 90.5%. Haemophilus influenzae protein P6, which possessed a high degree of surface antigen accessibility and antigencity, could be used as a marker for Haemophilus influenzae detection. The immunochromatographic colloidal gold test strip which bears the features of rapidity, convenience and sensitivity provides a unique tool for the on-site surveillance and diagnosis of Haemophilus influenzae infection in clinical test.