S. Huiss et al., CHARACTERISTICS OF ASYMPTOMATIC SECONDARY IMMUNE-RESPONSES TO MEASLES-VIRUS IN LATE CONVALESCENT DONORS, Clinical and experimental immunology, 109(3), 1997, pp. 416-420
Among 44 fully protected, late convalescent adults re-exposed to measl
es, four developed an asymptomatic secondary immune response (SLR) wit
h a significant increase in measles virus (MV)-specific IgG and low Ig
M. The boosted antibodies were mainly of the IgG1 subclass and reacted
with the nucleoprotein and the haemagglutinin protein. About 30 weeks
after re-exposure, antibody levels had decreased by 35-50%, suggestin
g that the booster effect may only be transient. SLR was only found in
individuals with a pre-exposure IgG level below a well defined thresh
old. Antibody levels above this threshold fully protected against SIR.
SIR seems to be an 'all or none response' where the magnitude of incr
ease in specific IgG is independent of pre-exposure antibody levels as
long as these are below the above threshold. In combination with pre-
exposure neutralizing and haemagglutination inhibiting titres, a thres
hold was defined below which SIR is Likely to occur. This may be usefu
l to predict susceptibility to SIR in a given population, since indivi
duals undergoing clinically inapparent SIR are among seropositive subj
ects, the most likely candidates to support transmission of virus.