Rubella reinfection; role of neutralising antibodies and cell-mediated immunity.
BACKGROUND
Rubella virus may be transmitted to the fetus following rubella reinfection in early pregnancy. The mechanisms responsible for maternal-fetal transmission in women with pre-existing rubella antibodies are, however, unclear.


OBJECTIVE
To evaluate the protective role of rubella specific neutralising antibodies and cell-mediated immunity in rubella reinfection.


METHODS
Rubella Nt antibodies were measured in sera obtained from: women who experienced rubella reinfection during pregnancy, volunteers experimentally challenged with rubella vaccine and women attending for routine rubella antibody screening. Cell-mediated immunity was assessed by measuring rubella specific LT responses among women who had experienced rubella reinfection during pregnancy.


RESULTS
Some women experienced rubella reinfection during pregnancy despite the presence of Nt antibodies in sera obtained before contact. Only 2 of 13 (15.3%) volunteers with low levels (< 15 IU/ml) of rubella antibody had detectable Nt antibodies prior to experimental challenge. Despite this, they did not develop rubella viraemia following challenge and virus excretion was detected in only one case, although the majority (11/13, 84.6%) demonstrated a significant rise in antibody titre. Among pregnant women screened as having a low level of rubella antibody antenally, only 37% had detectable Nt antibodies. Among 23 women who experienced rubella reinfection during pregnancy 4 months to 6 years (mean 32 months) previously, 20 (86.9%) had a positive rubella-specific LT response. Only one of 4 cases where rubella virus was transmitted to the fetus failed to produce a a specific LT response.


CONCLUSIONS
This study indicates that rubella reinfection is not associated with a lack of Nt antibodies or persistent impairment of rubella-specific LT responses.
O'Shea
S
S
Department of Virology, United Medical and Dental Schools of Guy's and St Thomas's Hospitals, St Thomas's Campus, London, UK.
Corbett
K M
KM
Barrow
S M
SM
Banatvala
J E
JE
Best
J M
JM