A micro-neutralization system for detection of s-CRN antibody to herpes simplex virus.

It was learned that the ordinary micro-neutralization system with herpes simplex virus (HSV) gave a composite result of the initial neutralization and the effect of antibody on subsequent growth of unneutralized virus. In the case of slow-reacting complement-requiring neutralizing (s-CRN) antibody, which was detected by incubating virus-serum mixtures at 4 C for 3 days before addition of complement, the titer obtained was lower than expected from the result of the plaque reduction test. This was thought ascribable to its low ability to prevent viral breakthrough caused by growth of unneutralized virus. This was overcome by adding an appropriate amount of hyperimmune antibody at 3 hr after addition of cells. The endpoint of s-CRN antibody so determined was but slightly lower than that obtained by the plaque reduction test. Early (1-week) rabbit sera, which were negative in the ordinary micro-neutralization test, titered 1:2,560 to 1:5,120 when tested by this method. When the 3-day sensitization in the cold was substituted by 5-hr incubation at 37 C, the titer obtained was 2 to 4-fold lower; in this case, however, the whole process could be finished within 3 days. Also, s-CRN antibody reactive with type 2 HSV in homologous and heterologous sera could be detected by the same method using type 1 hyperimmune serum as the additional antibody.