0095-1137/78/0007-0034$02.00/0 JOUJRNAI OF CLINICAL MICROBIOLOGY, Jan. 1978, p. 34-38 Vol. 7, No. 1 Copyright (C 1978 American Society for Microbiology Printed in U.S.A. Persistence of Immunoglobulin G and Immunoglobulin M Antibodies After Postnatal Rubella Infection Determined by Solid-Phase Radioimmunoassay OLLI H. MEURMAN Department of Virology, University of Turku, SF-20520 Turku, Finland Received for publication 19 August 1977 The appearance and persistence of immunoglobulin M (IgM) and IgG antibod- ies in postnatal rubella infections were studied by employing a solid-phase radioimmunoassay test. Altogether, 222 serial serum specimens from 51 patients with acute rubella infection were tested. Both IgG and IgM antibodies developed rapidly and appeared in all patients within 4 days after the onset of rash. In some patients, the IgM antibodies clearly preceded the IgG antibodies; however, the reverse situation was also noticed in a few cases. The IgG antibodies showed only minor changes after 8 to 10 days from the onset of rash. The IgM titers also reached a maximum level at approximately 8 to 10 days after the onset of rash, after which time a rapid decrease was normally seen. The mean half-life of IgM antibodies after 15 days from the onset of rash was 4.5 days, giving for IgM antibodies persistence times from 43 to approximately 80 days. Two patients with a prolonged IgM antibody response were detected. One of these patients had bilateral arthritis of the knee as a complication, whereas in the other patient no complication caused by rubella virus was detected. The IgM antibody response and its value in diagnosis are discussed. Demonstration of a recent viral infection by 51 patients with acute rubella infections. The patients the determination of specific immunoglobulin were male army trainees with a mean age of 19.9 M antibodies is dependent upon knowing years (range, 17 to 24 years), who contracted the (IgM) infection during rubella epidemics occurring in three the "normal" persistence of these antibodies army bases in southwest Finland. The patients were after an uncomplicated infection and the inci- followed for 29 to 200 days postinfection, and three dence of prolonged or persistent IgM antibody to six serial serum specimens were collected from each response in the normal population. In rubella patient. infections, IgM antibodies have been reported In addition, 200 sera, positive in the rubella hemag- to persist from 20 to 40 days (4, 7, 30) up to glutination inhibition (HI) test, were collected from over 1 year (1). This variation is considerable, 50 males and 50 females belonging to the age group but can for the most part be explained by differ- of 15 to 25 years and from 50 males and 50 females ences in sensitivity between the techniques used. belonging to the age group of 40 to 50 years. The This demonstrates that for clinical diagnostic mean ages of these groups were 19.5 and 44.2 years, respectively, and the geometric mean HI titers were use, the results of any IgM test can be reliable 79 and 56, respectively. only if knowledge of the general behavior of Sera with high rheumatoid factor activity were ex- IgM antibodies, as studied by the method in cluded from this study. The specimens were tested question, has been obtained by testing a large immediately or stored at -20°C until used. number of serial serum specimens from patients RIA procedure. The methods used in this study with an acute rubella infection. have been described in detail elsewhere (19, 20). The present investigation was initiated to Briefly, purified rubella virus antigen was adsorbed study the immune response of postnatal rubella onto polystyrene balls, and serum antibodies binding infections, with special aattention being paid to to the antigen were detected by "251-labeled anti-hu- man gamma and anti-human mu immunoglobulins. the persistence of IgM antibodies. The method The criteria for positive specimens, as well as the employed was the sensitive and reliable solid- estimation of end-point titers, were the same as pre- phase radioimmunoassay (RIA) method re- viously described (20). cently developed in our laboratory (19, 20). HI tests. HI tests were carried out with a modified microtechnique (28). MATERIALS AND METHODS RESULTS Serum specimens. A total of 422 serum specimens were tested. Included were 222 serial specimens from IgG antibody response. The appearance 34 VOL. 7, 1978 IgG AND IgM ANTIBODY RESPONSE IN RUBELLA 35 and persistence of IgG antibodies in 51 cases of whereas in the rest approximately equal titers acute rubella infection are shown in Fig. 1. The were found. The IgM antibodies also reached antibodies developed quite rapidly and were maximum titers about 1 week after the onset of present in all specimens taken between 4 and rash. During week 2, the titers decreased slightly 200 days after the onset of rash. The maximum or, in some cases, remained stable. After that titers were generally reached in about 1 week, time, the titers decreased constantly, with a half- although in some patients slight increases in life of 4 to 5 days. Since this half-life value was titers were still noticed up to month 2 after the rather constant in all 49 patients, the persistence onset of rash. After that time, the individual of IgM antibodies depended upon the peak ru- titers decreased, having, at the end of the follow- bella IgM titer reached in each individual. The up, values of one-half or one-quarter of the de- observed persistence of IgM antibodies, exclud- tected peak titers. ing two patients who will be described below, IgM antibody response. Figure 2 shows the varied from 43 to 59 days. However, since some IgM antibody reponse in 49 cases of acute ru- of the sera still had titers of 128 to 256 at 57 to bella infection. The IgM antibodies developed 58 days after the onset of rash, the persistence on an average somewhat sooner than did IgG of IgM antibodies in these patients appeared to antibodies; however, the difference in time was be approximately 80 days. very small. Among the first serum specimens In two patients, the behavior of IgM antibod- that were taken 0 to 3 days after the onset of ies followed a different pattern, with a slow rash and in which rubella antibodies were de- decline and prolonged persistence of these anti- monstrable, IgM antibodies without IgG anti- bodies. The IgM antibody responses of these bodies were found in 10 cases, and IgG antibod- patients are shown in Fig. 3 together with normal ies without IgM antibodies were found in three IgM antibody responses of five other patients cases. In an additional 10 cases the IgM antibody (also included in Fig. 2) for comparison. One of titer was markedly higher than the IgG titer, the patients with a prolonged IgM antibody Qrw 32000 1 16000 :j: !I.:I .: ::: ::. - . I 8000 a 4096 .. ° 2048 z 1024 4 512 0 256 $. 4 128 t 64 32 16 0.. <16 0 K0 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 DAYS AFTER ONSET OF RASH FIG. 1. Rubella RIA IgG titers obtained on 222 serial serum specimens from 51 patients with acute rubella infection. The solid line represents the geometric mean titer. 70 80 90 100 110 120 130 140 150 160 170 180 190 200 DAYS AFTER ONSET OF RASH FIG. 2. Rubella RIA IgM titers obtained on 213 serial serum specimens from 49 patients with acute rubella infection. The solid line represents the geometric mean titer. 36 MEURMAN J. CLIN. MICROBIOL. Cr64000 The results obtained in this study are in agree- I-32000 16000- ment with earlier publications. IgM antibody 8000- titers increased rapidly up to 8 to 10 days after 40196O 8 the onset of rash, during which time rubella I-2048- z 4 1024- virus can be recovered from the body (14). About 2 512- the time when free antigen disappears, the an- 256- 5128- tibody production is known to complete the 64- switchover from IgM formation to IgG forma- 32 16 tion, after which the IgM antibodies follow a <16 half-life of approximately 5 days (3). In this 0 10 20 30 40 50 60 70 80 90 100 110 study the observed mean decrease rate of the DAYS AFTER ONSET OF RASH IgM titer was linear, beginning from about day FIG. 3. Rubella RIA IgM titers of two patients 15 after the onset of rash. The calculated half- with a prolonged IgM antibody response (0) and of life for the rubella IgM antibodies was 4.5 days. five patients with a normal IgM antibody response By using sucrose density fractionation fol- (0). lowed by an HI test with overnight incubation of sera with the antigen, Al-Nakib et al. (1) response had bilateral arthritis of the knee as a reported the persistence of IgM antibodies for complication. The other patient had no apparent 1 year in four out of nine cases of uncomplicated complication caused by rubella virus, but a bac- postnatal rubella. It has been shown, however, teriologically verified streptococcal tonsillitis oc- that immunodiffusion, the method that they curred at the same time as the rubella infection. used to confirm the purity of the IgM fractions, A study of the possible persistence of rubella is not sensitive enough when overnight incuba- IgM antibodies in a normal population was also tion is used for the HI test (26). Small amounts undertaken. A total of 200 rubella HI-positive of contaminants, undetectable by immunodiffu- sera collected from persons belonging to the age sion, can give rise to IgM results that are false groups of 15 to 25 and 40 to 50 years were tested positives as verified by the resistance of those by the RIA test.