Microprecipitin Test

Abstract

The viral protein coat has multiple epitopes accessible to antibodies. Antibodies have two antigen-binding sites. When brought together in optimal proportions, antibodies can link virus particles and form large aggregates. In droplets, such aggregates are visible as a whitish precipitate. If either the numbers of antibodies or virus particles are limiting, no visible precipitate is formed. This is the basis for testing the quality of an antiserum in the microprecipitin test. Drops of a series of twofold antiserum dilutions are mixed with drops of a similar series of virus dilutions in a grid titration. The greatest dilution giving a visible precipitate can be determined for both antiserum and virus. For the antiserum, this highest dilution factor signifies the titre of the serum. The microprecipitin test cannot be recommended for detection purposes, as it is not a very sensitive test.