Development of a slide latex agglutination test for rotavirus antigen detection

The aim of this study was to optimize the conditions for the passive adsorption of polyclonal antibody onto plain surface polystyrene latex particles and its performance in a slide latex agglutination test for rotavirus antigen detection. Cleaning of latex particles by washing through repetitive centrifuging, decanting and resuspending in distilled water was adequate in removing surfactants from the particles' surfaces to enable coating. A study of antibody concentration, incubation temperature and buffer pH revealed that optimum coating was achieved with a 3-fold excess of antibody to the calculated total particle surface capacity for the antibody in a glycine-saline buffer of pH 9.2 at 40 degrees C for 4 hours. The ionic strength and pH of the latex suspending buffer and the sample buffer were critical factors determining the sensitivity of the test and the appearance of non-specific agglutination. Ultrasonication, addition of glycerol and Tween 20, either individually or in combination, were able to suppress non-specific agglutination in some batches of latex reagents. Polyethylene glycol 6000 enhanced the quality of agglutination as well as reduced the time of its appearance, especially in reagents that produced poor agglutination.