Francis A. Ennis

Persistence of maternal antibody in infants beyond 12 months: mechanism of measles vaccine failure.

A serologic study was made in 34 children immunized against measles at the age of 12 months. Using a sensitive virus neutralization test, it was found that many of the children had pre-existing maternal antibody to measles virus. Children with high pre-existing antibody titers failed to seroconvert. Children with lower pre-existing antibody titers seroconverted, but the resulting antibody titer was significantly lower than in children without pre-existing antibody titer. The results of this study demonstrate a probably mechanism for measles vaccine failure in 12-month-old children and support the recommendation of the Public Health Service Advisory Committee on Immunization Practices to postpone measles vaccination to 15 months of age.

Sensitive Neutralization Test for Virus Antibody

SummaryA sensitive mumps virus plaque neutralization test has been developed based on the potentiation of virus-antibody complexes by heterologous anti-immunoglobulins (AIG). The enhanced neutralization test was approximately 100 times more sensitive than the conventional neutralization test or the hemagglutination-inhibition test. Using AIG against human immunoglobulin G (IgG) or human IgM permitted determination of the relative titers of the two classes of mumps antibody. The test does not require special equipment or expertise and can be readily introduced in virological laboratories.

An assay for virus-specific help for B cells

Spleen cells from mice immunized with vaccinia or influenza viruses were mixed with spleen cells from mice immunized by dinitrophenyl-keyhole limpet hemocyanin (DNP-KLH) and transferred into irradiated syngeneic recipient mice which were subsequently restimulated with trinitrophyenylates (TNP) or unmodified viruses. One week later, spleens were removed and assayed for indirect anti-DNP plaque-forming cells (PFC). When spleen cells from both influenza and vaccinia primed mice were restimulated with the haptenated form of the virus used for the initial immunization there was an enhanced PFC response compared to that seen with spleen cells from unprimed mice.

A novel plaque method for attenuated rubella virus in Vero cell cultures.

SummaryUnder defined plaquing conditions, three attenuated strains of rubella virus showed different plaque morphology and plaque size when tested in Vero cell cultures. The Cendehill strain of rubella virus formed distinct, ring-shaped plaques, while strains HPV 77 and RA 27/3 produced clear plaques that could be distinguished by their different size. These distinguishing characteristics remained preserved even after the vaccine strains were passaged five consecutive times in Vero cell cultures.