Serum antibodies to rubella virus in healthy individuals with indirect immunofluorescent method

: To investigate sensitivity to rubella virus (RV) in healthy individuals, we examined levels of antibodies to RV in sera by an indirect immunofluorescence assay (IFA) and compared levels of antibodies by IFA with those by a hemagglutination inhibition (HI) assay. Of 114 healthy individuals, we detected antibodies to RV in serum specimens from 103 (90.3%) by IFA and in those from 109 (95.6%) by HI assay. The peak value of levels of antibodies by HI assay was 4 fold higher than that by IFA. When levels of antibodies by IFA were less than 32, levels of antibodies by HI assay ranged from < 8 to 1024. We did not detect anti-rubella antibodies of IgM class in all serum specimens and detected anti-rubella antibodies of IgA class in serum from only 1 individual by IFA. We detected antibodies to rubella in sera from 51 (94.4%) by IFA and in sera from 52 (96.3%) by HI assay of 54 individuals who reported having had rubella, and in sera from 23 (88.5%), by IFA and in sera from 26 (100%) by HI assay of 26 individuals reported having been vaccinated. Also, we detected anti-rubella antibodies in sera from 13 (76.5%) by IFA and in sera from 15 (88.2%) by HI of 17 individuals who reported having had neither rubella nor vaccination. In serum from 1 individual who reported having had rubella, we detected antibodies to rubella by IFA but not by HI assay. In serum specimens from 2 individuals who reported having had rubella vaccination, from 3 having had vaccination, from 2 having had neither rubella nor vaccination, we detected anti-rubella antibodies by HI assay but not by IFA. On the other hand, by both assays, we detected antibodies to RV in all sera of individuals who reported having had rubella and been vaccinated. The serodiagnosis, at least, by two methods is necessary to prevent individuals from rubella virus infection, because of following results: 1) influence of an inhibitor in serum specimens was thought to be variable. 2) The results measured by IFA were differed from those by HI assay in some individuals. 3) It is difficult in diagnosis of rubella from clinical symptoms alone. Also, it might be required to use vaccine to the individual who lacks detectable antibodies to rubella in serum by any method to prevent rubella infection.