ウイルス検査の現状と問題点(2)

妊婦の風疹感染診断における抗体測定の現況と限界

加　藤　茂　孝*1　海　野　幸　子*2
　　　　　　　　　　　　　　　　　　　　　　
The Present Situation and Limitation of Antibody Assays for Diagnosis of
Rubella Virus Infection in Pregnant Women

Shigetaka KATOW, PhD*1 and Yukiko UMINO, PhD*2

Rubella virus infection during early stages of pregnancy often results in a number of developmental disorders referred to as congenital rubella syndrome(CRS). Both clinical and laboratory diagnosis of suspect cases of CRS can be made with relative ease, particularly when expectant mothers show the typical rubella-specific rash. Serological diagnosis of CRS is accomplished using hemagglutination inhibition (HI) and enzyme-linked immunosorbent(IgM-EIA) assays. Antibody titers as determined by these assays are generally very high following acute apparent rubella infections, thus making serological diagnosis relatively easy in most cases. However, the detection of possible CRS cases can be hampered by clinically inapparent rubella infections during early pregnancy. As much as 30 percent of all acute rubella cases are inapparent infections, and there is the very real potential for such inapparent infections to occur during pregnancy, to result in fetal infections, and consequently to cause CRS. Detection of CRS becomes extremely difficult in such settings. Complicating CRS detection even more are rare rubella re-infections that might occur in early pregnancy, and unknown risk of fetal infection and CRS. In re-infection cases, HI antibody titer becomes elevated due to a secondary immune response, and IgM antibody is produced in a significant number of cases.
To determine directly the fetal infection, virus genome detection was developed and applied clinically for the past decade. Using a combination of serological and genomic detection methods, the results of the investigation suggest that when rubella infection during early pregnancy occurs 1)there is a significant risk of fetal infection that results from acute apparent rubella infection, 2)there is a measurable risk of fetal infection resulting from inapparent infections as defined by HI antibody titers 3 256 and with an IgM-EIA index 3 7, and 3)high HI antibody titers with low IgM-EIA indices or no detectable IgM antibody in cases of inapparent rubella infections may represent rubella re-infections and result in a low risk of fetal infections.
[Rinsho Byori 51 : 263〜267, 2003]

*2National Institute of Infectious Diseases, 162-8640

【Key Words】rubella(風疹)，CRS(先天性風疹症候群)，HI antibody(HI抗体)，IgM-EIA，genome detection(遺伝子検出)

*1National Center for Infectious Diseases, Centers for Disease Control and Prevention, USA
*2国立感染症研究所ウイルス第三部第二室(〒162-8640 武蔵村山市学園4-7-1)

E-mail :umino@nih.go.jp