Specific immunoglobulins in infants with the congenital rubella syndrome

Relationship between pregnancy and coronavirus: what we know

The identification in China in December 2019 of a new coronavirus (SARS-CoV-2) immediately rekindled the spotlight on a problem also addressed in the past during the epidemics of SARS in 2002-2003 and MERS in 2012: the implications of a possible infection during pregnancy, both for pregnant women and for fetuses and infants. Pregnancy is characterized by some changes involving both the immune system and the pulmonary physiology, exposing the pregnant woman to a greater susceptibility to viral infections and more serious complications. The objective of this review is therefore to analyze the relationship between pregnancy and known coronaviruses, with particular reference to SARS-CoV-2.

Hospital based surveillance of congenital rubella syndrome cases in the pre-vaccine era in Amhara Regional State, Ethiopia: A base line information for the country

Background

Rubella virus infection in early pregnancy lead to serious multi-organ birth defects known as congenital rubella syndrome (CRS). The incidence of CRS varies in different populations and the highest burden is found in developing countries in which rubella vaccination is not included in their national immunization programs. In Ethiopia, there is scarcity of data about congenital rubella syndrome. Therefore, the aim of this study was to determine the burden of CRS-related birth defects and its incidence in the pre-vaccine era in Amhara Regional State, Ethiopia.

Materials and methods

A cross sectional study was conducted in Dessie, Felege-Hiwot and University of Gondar Referral Hospitals, from December 2015 to August 2017. After getting informed assent from each parent/guardian, blood was collected from infants < 1 year of age for laboratory determination of anti-rubella virus antibodies. Their socio-demographic data and clinical information compatible with congenital rubella syndrome were collected using WHO guideline.

Results

During the study period, a total of 50 infants suspected for congenital rubella syndrome were included in the study. All infants suspected for CRS were tested against rubella specific IgM and IgG [for infants ≥ 6 months of age] antibodies using ELISA method. Of these, 9/50 (18%) and 4/14 (28.6%) of them were laboratory confirmed and potential CRS cases, respectively. In the present study, the most common laboratory confirmed defect was ocular manifestations 6 (66.7%) followed by heart related problems 5 (55.6%). In the present study, most of the laboratory confirmed cases (66.7%) were reported among 1–5 months of age infants. In addition, 5 (55.6%) of the infants with laboratory confirmed CRS cases were male and 6 (66.7%) of them were from urban settings. In this study, the incidence of CRS was 0.4 per 1000 live births.

Conclusion

In this study, nearly one fifth of the infants had laboratory confirmed congenital rubella syndrome and most of them had multiple rubella associated congenital defects at a time. Most of these congenital anomalies were reported among infants ≥ 1 month of age. Based on our result, the incidence of the CRS was line with the global incidence of the CRS in the pre-vaccine era. Therefore, establishing strong rubella/CRS surveillance system as well as introducing the rubella containing vaccine in the national immunization program might be important to reduce the burden of rubella and CRS in the country.

Congenital Rubella Syndrome: A Case Report on Changes in Viral Load and Rubella Antibody Titers

To our knowledge, this is the first report of the use of real-time reverse transcription-polymerase chain reaction to assess changes in viral load in a patient with congenital rubella syndrome (CRS). Rubella-specific antibody titers were also determined. The patient was a male neonate born to a primipara with rubella infection at 10 weeks of gestation. He had no symptoms at birth, but rubella virus was detected in his pharynx, blood, and urine. His mental and physical development was normal for 1 year; however, he was diagnosed with deafness at 13 months of age. Thus, the patient was diagnosed with CRS. Rubella infection in the pharynx was almost constant until 5 months of age; however, it increased dramatically at 6 months of age. No infection was detected at 13 months. Rubella-specific immunoglobulin M titer was consistently low until 9 months of age and then decreased gradually until it became negative at 20 months of age. Rubella-specific immunoglobulin G titer was high at birth. However, it decreased at 3 months and increased again at 4 months. This titer peaked at ∼9 months and then decreased again at 13 months. This case shows that the period after the decline in maternal antibody titers, not the neonatal period, may be the most contagious period in patients with CRS.

Post-exposure passive immunisation for preventing rubella and congenital rubella syndrome

BACKGROUND

Control of rubella is desired because infection in early pregnancy can result in miscarriage, foetal death or congenital abnormality. Primary studies examining the effectiveness of immunoglobulins for post-exposure prophylaxis of rubella have small sample sizes and varying results. National public health recommendations suggest a degree of effectiveness.

OBJECTIVES

To assess the effectiveness of intramuscular injection or intravenous infusion of polyclonal immunoglobulins of human sera or plasma origin for preventing rubella and congenital rubella syndrome when administered to exposed susceptible people before the onset of disease.

SEARCH METHODS

We searched CENTRAL (2014, Issue 7), MEDLINE (1946 to August week 2, 2014), EMBASE (1974 to August 2014), CINAHL (1981 to August 2014), LILACS (1982 to August 2014) and Web of Science (1955 to August 2014). We searched ClinicalTrials.gov and the World Health Organization International Clinical Trials Registry on 16 October 2014. We searched the reference lists of relevant retrieved reviews and studies and identified national public health guidelines.

SELECTION CRITERIA

For the outcome 'preventing cases of rubella', we included randomised controlled trials (RCTs) and quasi-RCTs. We found several studies addressing this outcome where the design was a controlled clinical trial (CCT) (with exposure to rubella virus controlled by the investigators) but the method of allocation of participants to groups was not reported. We found an alternative report of one of these studies that indicated participants were assigned to groups randomly. We therefore included such studies as meeting criteria for RCTs or quasi-RCTs and undertook sensitivity analyses. For the outcomes, 'congenital rubella infection' and 'congenital rubella syndrome', we included RCTs, quasi-RCTs and prospective controlled (cohort) studies. Participants were necessarily susceptible and exposed to rubella. Polyclonal immunoglobulins derived from human sera or plasma must have been administered intramuscularly or intravenously as the only intervention in at least one group.

DATA COLLECTION AND ANALYSIS

We used the standard methodological procedures expected by The Cochrane Collaboration.

MAIN RESULTS

We included 12 studies (430 participants) in the review: seven RCTs and five CCTs where it was not clear whether participants were randomly allocated to groups. We did not include any unpublished studies. Participants included children and adults of both sexes. Only one study included pregnant women. All studies were conducted in high-income countries.The quality of the 11 studies in the initial meta-analysis was moderate, although we classified no study as having a low risk of bias on all criteria.We included 11 studies in the initial meta-analysis of gamma-globulin (concentrated polyclonal immunoglobulins) versus control (saline or no treatment) for rubella cases. The result favoured the intervention group (risk ratio (RR) 0.61, 95% confidence interval (CI) 0.45 to 0.83) but was heterogenous (Chi² test = 36.59, df = 10 (P value < 0.0001); I² statistic = 73%). Heterogeneity was explained by subgrouping studies according to the estimated volume of gamma-globulin administered per pound of bodyweight and then removing those studies where the intervention was administered more than five days after participant exposure to rubella (post hoc analysis). The test of subgroup differences demonstrated heterogeneity between subgroups according to our protocol definition (P value < 0.1; I² statistic > 60%) and there appeared to be greater effectiveness of the intervention when a greater volume of gamma-globulin was administered ('0.027 to 0.037 ml/lb' RR 1.60 (95% CI 0.57 to 4.52); '0.1 to 0.15 ml/lb' RR 0.53 (95% CI 0.29 to 0.99); '0.2 to 0.5 ml/lb' RR 0.20 (95% CI 0.04 to 1.00)).None of the studies reported the outcome 'congenital rubella infection'. One included study reported on congenital rubella syndrome, with no cases among participants who were fewer than nine weeks pregnant at enrolment and who were randomised to one of two gamma-globulin groups ('high' or 'low' rubella titre). However, the study did not report how congenital rubella syndrome was measured and did not report the length of follow-up according to intervention group. This study did not include a non-treatment group.No included study measured adverse events.

AUTHORS' CONCLUSIONS

Compared to no treatment, polyclonal immunoglobulins seem to be of benefit for preventing rubella. The available evidence suggests that this intervention may be of benefit up to five days after exposure, and that effectiveness is dependent on dose. Considering the attack rate for rubella cases in the control group of the highest volume gamma-globulin subgroup (333 per 1000), the absolute risk reduction (calculated from the RR) for this volume of gamma-globulin was 266 (95% CI 0 to 320) and the number needed to treat to benefit is four (95% CI 3 to incalculable).The included studies did not measure rubella-specific antibodies in the immunoglobulin products used in a standard way and thus estimation of the dose of rubella-specific antibodies in international units administered was not possible. As the concentration of rubella-specific antibodies in today's polyclonal immunoglobulin products may vary from those products used in the studies in the review, the volume required per pound of bodyweight to produce similar results may also vary.There is insufficient evidence to make direct conclusions about the effectiveness of polyclonal immunoglobulins for preventing congenital rubella syndrome. This is an area requiring further research.

Congenital rubella syndrome in a child born to Liberian refugees: clinical and public health perspectives

We describe a case of congenital rubella syndrome with typical stigmata in an infant born in New Hampshire to Liberian refugees. The infant's clinical specimens were tested for rubella. Rubella immunity status was sought for contacts. The infant's specimen cultures grew wild-type rubella virus; serum immunoglobulin M and G were positive. Eighteen of 20 contacts were rubella-immune. Family's transit history, mother's vaccination history, and infant's estimated gestational age supported congenital infection acquired overseas. Clinicians should maintain vigilance for congenital rubella syndrome in infants with relevant stigmata, particularly those whose mothers are from countries with nonexistent or recently implemented rubella vaccination programs.

Slow maturation of IgG1 avidity and persistence of specific IgM in congenital rubella: implications for diagnosis and immunopathology

Without appropriately timed specimens, serological confirmation of congenital rubella infection may be a problem. We have compared the persistence of specific IgM and low avidity specific IgG1 in 141 sera from 120 cases of serologically confirmed congenital rubella infection with the known time scales for postnatal primary rubella. The results demonstrate that the maturation of the immune response to the rubella virus is abnormally slow in congenital rubella cases both in terms of the isotype switch and especially the development of high avidity specific IgG1. Thus avidity studies may permit serological confirmation of congenital rubella for longer than is possible with tests currently in use. The pathological implications of prolonged low avidity antibody production are discussed.

Laboratory diagnosis of rubella: past, present and future

Fifty years ago in New South Wales the late Sir Norman Gregg [1] described congenital cataracts in 78 babies, 67 of whose mothers had had clinical rubella in early pregnancy; he concluded that the disease in the mother caused the abnormality in the baby. Gregg [1–3] and Swan [4, 5] and their colleagues reported that deafness, heart disease and microcephaly were also major components of the congenital rubella syndrome. The need to prevent this tragic outcome stimulated intensive work on laboratory diagnosis and vaccine development, leading to the isolation of rubella virus in 1962 and then to methods for antibody detection. These complementary advances established the two traditional pillars of virological diagnosis and opened the way to immunization, with the result that some countries are now on the verge of eliminating a disease which for over 100 years was regarded as no more than a mild and harmless exanthem of childhood.

Onset and severity of hearing loss due to congenital rubella infection

Of 111 children born in 1978-82 with congenital rubella infection, confirmed by the detection of rubella specific IgM shortly after birth, 68 were reported to be hearing impaired when notified to the National Congenital Rubella Surveillance Programme (NCRSP). The average age at which the diagnosis of hearing impairment was confirmed was 11.6 months. Recent audiograms showed a hearing loss that was usually uniform across all frequencies, equal in both ears and severe, averaging 93 dB across the range 250-4000 Hz. Despite the early diagnosis of congenital rubella and the known risk of deafness, only eight of 57 infants had been tested for auditory evoked responses in the first 6 months of life; all eight had severe hearing loss. Evidence of progressive hearing loss was found in only one of the 57 children. Definitive hearing tests (as distinct from screening tests) were frequently delayed until after the first birthday. Newborn babies identified as being at high risk of congenital deafness should have a full audiological assessment in early infancy.

[Pathologico-anatomic findings in sudden, unexpected death in children and adults with influenza A infection]

Thé following observations resulted from studies on forensic autopsy cases: In 76% of the adults and 55% of the infants the cases of unexpected sudden death without morphologically verifiable causes of death showed virologic evidence of recent influenza-A (H3N2)-infection. The pathologic findings corresponded with the findings in lethal infections with influenza-A viruses. Investigation of cases of sudden and unexpected death should always include virologic serum tests. The demonstration of IgM antibodies against influenza-A virus confirms that there was a recent infection. Death from influenza-A infections occurs also in the interepidemic periods.

Separation of hemagglutination-inhibiting immunoglobulin M antibody to rubella virus in human serum by high-performance liquid chromatography

High-performance liquid chromatography was successfully used to separate hemagglutination-inhibiting immunoglobulin M (IgM) rubella virus antibody from IgG rubella virus antibody in human serum. The fractionation by high-performance liquid chromatography was as effective as sucrose density gradient centrifugation in separating IgM antibody from IgG antibody.

Selection and performance of monoclonal and polyclonal antibodies in an IgM antibody capture enzyme immunoassay for rubella

Monoclonal anti-human IgM and anti-rubella antibodies were prepared and tested in an IgM capture enzyme immunoassay (MACEIA) for rubella-specific IgM and compared with polyclonal reagents. Assay sensitivity was increased with monoclonal antibodies resulting in the improved discrimination of adult sera with low levels of specific IgM. Despite high IgM binding, interference by IgM anti-Ig was not a major problem. The use of monoclonal antibodies allowed assay simplification by the simultaneous rather than sequential addition of antigen and conjugate. Although comparable results were obtained with 33 test samples in the sequential and simultaneous MACEIA, the specificity and sensitivity of this modification requires further evaluation.

Enzyme immunoassays and related procedures in diagnostic medical virology

This review article describes several applications of the widely used enzyme immunoassay (EIA) procedure. EIA methods have been adapted to solve problems in diagnostic virology where sensitivity, specificity, or practicability is required. Concurrent developments in hybridoma and conjugation methods have increased significantly the use of these assays. A general overview of EIA methods is given together with typical examples of their use in diagnostic medical virology; attention is drawn to possible pitfalls. Recent advances in recombinant DNA technology have made it possible to produce highly specific nucleic acid probes that have a sensitivity approximately 100 times greater than that of EIA. Some applications of these probes are described. Although the non-labelled nucleic acid probes for use in the field are not as refined as non-labelled immunoassays, their range of applications is expected to expand rapidly in the near future.

Inadequacy of immunoglobulin M hepatitis B core antibody in detecting acute hepatitis B virus infection in infants of HBsAg carrier mothers

To study the usefulness of IgM hepatitis B core antibody (anti-HBc IgM) for detecting hepatitis B virus infections in infants of hepatitis B surface antigen (HBsAg) carrier mothers, serial serum samples from 86 infants of carrier mothers were tested for anti-HBc IgM with a highly specific enzyme immunoassay. Asymptomatic hepatitis B infection occurred frequently in infants under 12 mo of age. Anti-HBc IgM never became positive in 25 infants infected under 9 mo old. It was positive in only 1 of 6 infected at 9 mo and 4 of 13 infected at 12 mo of age. The IgM antibody lasted for less than 6 mo. Although the infection was delayed in 28 infants receiving hepatitis B immune globulin, the poor anti-HBc IgM response did not seem to be due to the immune prophylaxis. Our study clearly indicates the limitation of anti-HBc IgM for detecting acute hepatitis B infection in infants born to HBsAg carrier mothers.

Evaluation of commercial methods of enzyme immunoassay (EIA) for the measurement of rubella-specific IgM

Four commercial EIA methods for measuring rubella-specific IgM (three indirect tests and one anti-mu capture test) were evaluated, using sucrose gradient centrifugation and hemagglutination inhibition as the reference method. Evaluation was conducted with the aid of four serum panels, including 53 primary rubella cases, 30 healthy pregnant women, 21 sera positive for rheumatoid factor(s) (RF) and 35 sera from 29 cases of heterophil-positive infectious mononucleosis with EBV-specific IgM detected by immunofluorescence. All EIA methods were more sensitive than the reference method when applied to very early samples (1-5 days post-exanthema) and no differences in sensitivity were found between them. On the other hand, we observed a significant incidence of false-positive results if an indirect EIA method is applied to RF-positive samples. False positivity is significantly reduced, but not totally eliminated, when samples are preabsorbed with anti-human IgG serum and, in all cases, the absorbance values obtained were low. In contrast, there were no false-positive results using an anti-mu capture method, even in sera from cases of infectious mononucleosis. The basis for choosing between an indirect method and an anti-mu capture method for the diagnosis of congenital and post-natal rubella virus infection is discussed.

Measurement of BK papovavirus IgG and IgM by radioimmunoassay (RIA)

Current techniques for the measurement of BK papovavirus (BKV) specific IgM include sucrose density gradient centrifugation followed by hemagglutination inhibition (HAI) or indirect immunofluorescent (IF) staining of BKV infected cells using a fluorescein conjugated anti-human IgM antibody. These techniques are cumbersome and labor intensive and do not lend themselves to testing large numbers of sera. A solid phase radioimmunoassay (RIA) was developed to facilitate the measurement of BKV IgG and IgM in large numbers of sera. Solid phase antigen was prepared by adsorbing CsCl purified BKV antigen to polyvinyl chloride microtiter plates. Following reaction with serum, bound immunoglobulin was detected with iodinated goat anti-human IgG or IgM. RIA for the measurement of BKV IgG was sensitive with titers approaching 10(-6). Determination of IgG titers by RIA and HAI showed good agreement (P less than 0.01, correlation coefficient = 0.74). Measurement of BKV IgM was not affected by the presence of BKV IgG as evidenced by sucrose density gradient fractionation of IgM positive sera, removal of IgG by treatment with S. aureus protein A, and addition of BKV IgG to BKV IgM. Rheumatoid factor (RF) gave false positive IgM titers in the presence of BKV IgG when RF titers were greater than or equal to 1:640 by latex agglutination testing and BKV IgG levels exceed 1:256 by HAI. False positives due to RF could be eliminated by treatment of sera with sheep anti-human IgG antisera. RIA for BKV IgM was specific as sera containing JCV-, cytomegalovirus (CMV)-, rubella-, or hepatitis B core antibody (anti HBc)-IgM were negative by RIA. RIA detected BKV IgM in several sera from renal dialysis or allograft patients with titers ranging from 1:400 to 1:128,000 and demonstrated that BKV IgM persisted in sera of renal allograft patients for as long as 343 days post transplantation.

Congenital infections with nonarbo togaviruses

The present review deals with the similarities and differences of selected aspects of prenatal pestivirus infections of domestic animals and congenital rubella of man. Hog cholera virus, bovine virus diarrhoea virus and border disease virus are antigenically closely related, but unrelated to rubella virus. The nonarbo togaviruses are capable of producing congenital infections resulting in a wide spectrum of abnormalities. The infected foetus can die in utero, in the neonatal period, or it may be born with teratogenic defects. In addition, apparently healthy progeny can be delivered that develop a late onset disease, months, or years after birth, or remain clinically normal for life. The ultimate outcome of a congenital infection is mainly determined by the stage of foetal development, at which infection occurs. Foetuses exposed to rubella virus raise an antibody response to the virus, whereas domestic animals frequently fail to respond immunologically to a congenital pestivirus infection. In congenital rubella the virus usually disappears from the host's body 1-2 years after birth. However, congenital pestivirus infections may be characterized by a lifelong and widespread persistence of virus in clinically healthy animals. Such animals are of significance in the epizootiology of bovine virus diarrhoea, border disease or hog cholera.

Consequences of confirmed maternal rubella at successive stages of pregnancy

Over a thousand women with confirmed rubella infection at different stages of pregnancy were followed up prospectively. Two-thirds of the women were multiparous. Pregnancy continued in 40%, and the infants were followed up after birth both clinically and serologically. The frequency of congenital infection after maternal rubella with a rash was more than 80% during the first 12 weeks of pregnancy, 54% at 13-14 weeks, and 25% at the end of the second trimester. The infection rate then rose again to reach a high figure in the last month. Follow-up was to 2 years of age--the findings in infected children being compared with those in children who had escaped infection. Rubella defects occurred in all infants infected before the 11th week (principally congenital heart disease and deafness) and in 35% of those infected at 13-16 weeks (deafness alone). No defects attributable to rubella were found in 63 children infected after 16 weeks. Continued surveillance of cases of confirmed rubella during pregnancy is recommended as an additional way of monitoring the effect of rubella vaccination.

A comparison of antibody capture radio- and enzyme immunoassays with immunofluorescence for detecting IgM antibody in infants with congenital rubella

IgM antibody capture radioimmunoassay (MACRIA) and enzyme immunoassay (MACEIA) were compared with immunofluorescence (IF) for detecting specific IgM antibody in 99 sera from 76 infants with confirmed congenital rubella, and 61 sera from a comparative group of 59 infants who had miscellaneous abnormalities but in whom congenital rubella was not confirmed. All of 35 specimens collected from confirmed cases within 12 weeks of birth were positive by all three methods and all but one of 17 specimens collected after the age of 18 months were uniformly negative. At intermediate ages discrepancies occurred in 18 specimens, of which eight were positive and 10 negative by IF. Three of these 18 specimens were negative by both antibody capture procedures but showed weak fluorescence; the other 15 were negative by MACEIA, but positive by MACRIA which appears to be the more sensitive of the antibody capture methods. Sera from five infants in the comparative group were clearly positive by all three methods. These five infants were probably congenitally infected with rubella. Sera from the other 54 infants were negative, except for one that gave a weakly positive result by MACRIA alone. Antibody capture procedures offer several advantages over previous methods for detecting IgM antibody. Although MACRIA was found to be slightly more sensitive than MACEIA, the greater stability of the enzyme label, together with the possibility of both visual and quantitative assessment, could make MACEIA the method of choice for detecting rubella-specific IgM.

A simple and rapid method for detection of serum IgM antibodies to the rubella virus hemagglutinin

Serum IgM antibodies directed against the rubella virus hemagglutinin can be detected without prior serum fractionation. In the first step of a newly developed method, chick erythrocytes were sensitized with a subhemagglutinating dose of rubella hemagglutinin. Next, the sensitized erythrocytes were mixed with patient serum, allowing specific antibodies to react with the fixed antigens. Finally, rabbit antibodies to human IgM were used to create bridges between IgM molecules on different blood cells. The visible result was an easily read hemagglutination with sera which contain specific rubella IgM antibodies. The procedure is very simple and rapid to perform. At least 20 sera can be examined in approximately 2 h. No sophisticated instruments are needed. We have tentatively called the new method rubella anti-IgM hemagglutination (HA). Rubella anti-IgM HA was more sensitive than the standard density gradient centrifugation/hemagglutination inhibition technique, but the correlation between the methods was good. Non-specific inhibitors of hemagglutination or rheumatoid factors did not seem to interfere with the specificity of the new method, and competition for antigenic sites between antibodies from the IgG/IgA and IgM classes did not seem to represent a serious, practical problem.

Complement fixation by IgM and IgG autoantibodies on cultured human glial cells

The humoral immune response to autologous gliomas has been investigated in 16 patients using immune adherence and anti-C3 immunofluorescence assays of serum samples. Significant antiglioma antibody activity was detected in 56% of these sera. Fractionation experiments demonstrated that IgM class antibodies were more effective that IgG in their ability to fix complement on cultured glioma cell membranes. In addition, autologous IgG was shown to inhibit IgM complement-fixing activity in some experiments. "Capping" of immune complexes on the glioma cell surface is also described.

Trypsinised human O erythrocytes in the detection of rubella-specific IgM by sera fractionation on sucrose density gradient and absorption with staphylococcal protein A

Detection of rubella virus-specific IgM employing trypsin-treated human group O erythrocytes was evaluated using the method of sera fractionation on sucrose density gradients (SDG) and that of sera absorption with staphylococcal protein A. The former method proved to be highly specific and sensitive in confirming or excluding rubella by demonstration of specific IgM. In contrast, the latter method provided comparable results in only 71.43% of specimens tested by both methods while false-positive or -negative IgM results were obtained in the remaining 28.57% of specimens. In view of these results, therefore, it is recommended that all those specimens found positive for specific IgM by the protein A method must be confirmed by another procedure, possibly that of specific IgM reduction with 2-mercaptoethanol.

Multiple-antigen slide test for detection of immunoglobulin M antibodies in newborn and infant sera by immunofluorescence

A microimmunofluorescence test was evaluated for use in measuring immunoglobulin M (IgM) antibodies in infant sera to five of the agents implicated in congenital and neonatal disease. Pen point dots of Toxoplasma gondii, cytomegalovirus, rubella virus, herpes simplex virus, and chlamydial cell culture antigens were applied to each circle of eight-circle printed slides. These multiple-antigen slides greatly facilitated the screening of 607 sera from infants and 117 sera from mothers for the presence of IgM antibody to these agents. Forty sera could be examined microscopically in approximately 30 min. All sera reacting with one or more antigens were tested for rheumatoid factor by the latex method, absorbed with glutaraldehyde-cross-linked human IgG, and retested for the presence of IgM antibody. IgM antibody to cytomegalovirus was demonstrated in sera from four newborns, but IgM antibody to rubella virus could not be detected until 21 days after birth, although rubella virus was isolated from sera from five younger infants. This may indicate that rubella IgM levels in many congenitally infected newborns are too low to be measured by the immunofluorescence method. Five percent of the sera from infants in this study possessed demonstrable IgM antibody to one of the antigens.

Solid phase anti-IgM ELISA for detection of rubella specific IgM antibodies

IgM in the test sample was bound to anti-IgM on a solid phase consisting of a polystyrene microtest plate and rubella specific IgM antibody subsequently detected by incubation with crude rubella virus antigen and anti-rubella conjugate. High levels of rubella specific IgG, which decreased the sensitivity of an indirect ELISA for rubella IgM, did not interfere in the anti-IgM ELISA, whereas non-rubella IgM interfered by a competition for the anti-IgM on the solid phase. False-positive results owing to IgM rheumatoid factor could be prevented by the addition of aggregated IgG 0.1 mg/ml to the serum diluent. The median duration of the antibody response detected by the solid phase anti-IgM assay was 60 days (range 24-140) in test of serial serum samples from 17 patients with rubella. The assay appears suitable for routine diagnosis of postnatal rubella and will probably be particularly valuable for diagnosis of prenatal rubella.

Comparison of different methods for the detection of rubella-specific IgM antibodies

The rubella specific IgM titer in the serum specimens originating from healthy persons and from patients with clinical signs of rubella infection was determined by hemagglutination inhibition or hemagglutination reduction after IgM separation with the following methods: (a) density gradient centrifugation; (b) polyacrylamide agarose gel chromatography; (c) ion exchange chromatography with diethylaminoethyl cellulose columns; (d) solid-phase immunosorbent technique using microplates; (e) solid-phase immunosorbent technique using polyacrylamide microimmunobeads. Alternatively, we removed IgG and IgA by the use of protein A, anti-IgG, and anti-IgA, covalently coupled to controlled-pore glass (f). The titers obtained by the different methods showed qualitatively good correlations when combined with mercaptoethanol reduction. The quantitative measurement of specific IgM titers, however, revealed a lower sensitivity of column chromatography and methods of removal of IgG/IgA.

Fetal infection resulting from maternal rubella after the first trimester of pregnancy

We have tried to measure the incidence of prenatal infection in 304 infants whose mothers had had rubella at various times after the first 12 weeks of pregnancy. Two methods of assessment were used: first, serum obtained soon after birth was tested for specific IgM antibody; secondly, serum obtained after the age of eight months was tested for specific IgG. When maternal rubella occurred 12-16 weeks after the last menstrual period specific IgM antibody was detected in 28 out of 50 infants (56%). The proportion fell progressively to 12% after maternal rubella at 24-28 weeks, rose to 19% after rubella at 28-36 weeks and then to 58% when the illness occurred during the last month of pregnancy. In all, IgM antibody was detected in 77 out of 260 infants (29%). The fetus can thus be infected at any time during the second and third trimesters of pregnancy, but the risk varies at different stages.The figures for the prevalence of IgG antibody were greater throughout, because some infants had IgG who had previously lacked specific IgM. After maternal rubella at 12-16 weeks IgG antibody persisted in 22 out of 31 infants (71%). The proportion fell to 28% after rubella at 24-28 weeks and then increased progressively to 94% after rubella during the last month. In all, IgG antibody persisted in 94 out of 190 infants (49%). The true rate of fetal infection probably lies between the rates estimated from the presence of IgM antibody and the subsequent prevalence of IgG.Infants whose mothers had rubella at any time during pregnancy should be examined regularly for possible evidence of damage.

Rubella IgM antibodies in sera from infants born after maternal rubella later than the 12th week of pregnancy

The outcome of 338 pregnancies complicated by serologically confirmed rubella after the 12th week of gestation is reported. Therapeutic abortions were performed on 93 women, 1 pregnancy resulted in a spontaneous abortion and 5 in stillbirths. Cord blood or a sample collected at an age of 0--2 months from 209 liveborn infants were tested for rubella IgM antibodies after sucrose density gradient ultracentrifugation. Such antibodies were detected in samples from approximately 33% of infants born after maternal rubella in the 4th and 5th month of gestation, but only in 11% of infants born after maternal rubella later in pregnancy. The classical symptoms of congenital rubella were not observed with the possible exception of a suspected unilateral hearing loss in 1 infant born after maternal rubella in the 5th month of pregnancy.

Diagnosis of pre- and postnatal rubella by demonstration of specific IgM-class antibodies by a microplate immunofluorescence test

An indirect immunofluorescence technique employing rubella virus infected SIRC-cells grown in flat-bottomed plastic plates is described for the detection of specific IgM-class rubella antibodies in serum fractions obtained by sucrose density ultracentrifugation. The results were read by means of a fluorescence microscope with an incident light illuminator. A total of 176 serum specimens from five groups of patients were used for determination of the specificity and sensitivity of the test. The technique proved to be less time consuming and in addition to be more sensitive than the hemagglutination-inhibition method for the detection of rubella IgM-class antibodies.

Comparison of immunofluorescence and radioimmunoassay for detecting IgM antibody in infants with the congenital rubella syndrome

Immunofluorescence (IF) and radioimmunoassay (RIA) have been compared as methods for detecting IgM antibody in 124 infants with confirmed or suspected congenital rubella. IF was used to test sucrose density gradient fractions and RIA to test fractions and whole serum. When fractions were tested IF and RIA were equally specific and distinguished clearly between IgM and IgG, but RIA was the more sensitive method. The RIA titre in whole serum was always greater than in the peak IgM fraction and there was no evidence that testing the serum, rather than the fraction, could result in failure to detect IgM. With some sera RIA gave low titres which became negative after absorption with IgG-coated latex beads. The mechanism of this 'false positive' effect, which may have been due to IgM with anti-IgG activity, was not investigated, but if it can be removed by absorption it need not reduce the specificity of the test. During the first 6 months of life IgM antibody was detected by RIA in 30 out of 32 unfractionated sera and by IF in fractions from 28 of these. After the age of 6 months IgM was found progressively less frequently and the greater sensitivity of RIA became a more obvious advantage: 17 out of 60 specimens were positive by RIA and 11 of these were negative by IF. RIA testing of whole serum appears to be an economical, specific and sensitive method for detecting IgM antibody in congenital rubella, of particular value when the titre of antibody is low.

IgM fluorescence antibodies in sera of pregnant women exposed to rubella

A high per cent of false positive results for rubella virus IgM antibodies determined by immune fluorescence were detected in sera of pregnant women. After absorption with Staphylococcus suspension, Cowan 1 strain, and aggregates of human immunoglobulins, the false positive reactions due to IgM antiimmunoglobulin were eliminated.

Specific immunoglobulin responses after varicella and herpes zoster

The indirect immunofluorescence technique has been used to titrate the specific immunoglobulins in 200 sera from 64 patients with varicella, and 195 sera from 67 patients with herpes zoster. IgG and IgM antibodies were detected in all patients with varicella, and IgA in 59 (92%). All three classes of antibody appeared 2--5 days after the onset of the rash, increased virtually simultaneously and reached maximum titres during the second and third weeks. IgG then declined slowly, but never became undetectable and was still present in five subjects who were retested after 2--4 years; it was present in 88 out of 100 healthy young adults and probably persists indefinitely after varicella. IgA and IgM antibodies declined more rapidly and were not detected in specimens taken more than a year after the illness. IgA, however, may possibly persist in some cases since low titres were found in 8 out of 88 young adults who possessed IgG antibody and had presumably had varicella in the past. IgA responses were significantly weaker in children under the age of 6 years than in older children and adults. Six out of 67 patients with zoster were tested at various times before the onset of the rash: IgG antibody was detected in all. IgG was present in all sera taken after the onset of the rash, increased rapidly after 2--5 days, reached maximum titres during the second and third weeks and then declined slowly. IgA antibody was detected in 66 patients (99%) and IgM in 52 (78%); both types of antibody followed transient courses, as in varicella. Maximum titres of IgG and complement-fixing antibodies were greater after zoster than after varicella, but the differences were not significant. IgA and IgM titres in young adults with zoster were significantly lower than in older patients, and also lower than in young adults with varicella. Increases in varicella-zoster antibody in patients with herpes simplex virus infections consisted mainly of IgG, sometimes IgA, but never IgM.

Simplified chromatographic separation of immunoglobulin M from G and its application to toxoplasma indirect immunofluorescence

The indirect immunofluorescent (IIF) antibody technique for the detection of Toxoplasma gondii immunoglobulin M (IgM) often gives false negative results, probably due to the competition between IgG and IgM. We therefore adapted a gel filtration procedure for the separation of IgG and IgM to a routine diagnostic test capable handling at least 10 sera per day and requiring only 50 microliters of serum. The results from 108 sera having positive complement fixation titers for Toxoplasma showed that 17 were IgM positive when the whole serum was tested by IIF compared with 55 positive when the IgM fraction was used. Sera with antideoxyribonucleic acid titers do not give false positive results after fractionation, and the removal of IgG eliminates false positive results due to rheumatoid factor. A prospective study showed that Toxoplasma IgM may persist up to 9 months.

Problems affecting performance of the fluorescent treponemal antibody-absorption test for syphilis

Immunofluorescent staining of Treponema pallidum was studied to clarify the effect of three factors on the results of the fluorescent treponemal antibody-absorption test: (i) heat inactivation of sera at 56 degrees C for 30 min before testing, (ii) use of multicircle slides, and (iii) tungsten illumination to visualize and assess unstained treponemes on reactive as well as nonreactive smears. It was found that serum inactivation before testing was not necessary for detection of immunoglobin G antibody, but an immunoglobulin M prozone was detected in unheated serum. On multicircle slides, it was demonstrated that a false-positive reaction could be obtained in 30 s at 37 and 25 degrees C if a smear where a nonreactive serum had been placed was crossed by a strongly reactive serum from another circle. Tungsten illumination proved necessary for correct assessment of unstained treponemes on all fluorescent treponemal antibody-aborption test smears, reactive or nonreactive. The possible role of these factors in incorrect fluorescent treponemal antibody-absorption test results is discussed.

The detection of rubella-specific IgM antibodies by radioimmunoassay

An indirect solid-phase radioimmunoassay (RIA) has been developed for the detection of immunoglobulin (Ig) class-specific rubella antibodies. A commercial rubella haemagglutinin is dried and fixed on to the wells of flexible microtitre plates and allowed to react with serial dilutions of whole or fractionated human sera. Class-specific rubella antibodies are then detected by determining the specific binding of 125I-labelled anti-human IgG or IgM. The RIA was first evaluated by comparison with the haemagglutination-inhibition (HI) test for the detection of rubella-specific IgM in gel-filtration fractions. RIA was found to be as specific as HI but 10-150 times more sensitive. Rubella-specific IgG antibodies did not interfere in specific IgM determinations by RIA and therefore the latter technique was applied to unfractionated sera. The results obtained indicate that RIA on unfractionated sera is a practical, sensitive and specific technique which could provide a reliable method for the diagnosis of rubella. The rubella-specific IgM titres obtained by RIA were not increased by the removal of IgG by pretreatment of sera with Staphylococcal Protein A.

An indirect immunofluorescent antibody test for determination of Rubella virus specific IgM antibodies. Elimination of secondary IgM rheumatoid factor staining after absorption of serum IgG with Staphylococcal protein A

Absorption of sera with protein A rich staphylococci eliminated unwanted secondary IgM staining caused by rheumatoid factors in the indirect immunofluorescence test for rubella virus antibodies. The absorption did not lower the sensitivity for IgM rubella antibodies as compared with the haemagglutination inhibition test on the IgM serum fractions obtained by ultracentrifugation.

Evaluation of a simplified sucrose gradient method for the detection of rubella-specific IgM in routine diagnostic practice

Rubella-specific IgM was measured in a single fraction of serum from a sucrose density gradient. Haemagglutination inhibition (HAI) tests were performed on paired aliquots of the fraction untreated and after treatment with 2- mercaptoethanol, dilutions of the aliquots being incubated over night with rubella antigen before the addition of red cells. Of 822 sera tested, specific IgM was found in 249, but not in 492. When first tested, the remaining 81 sera gave unsatisfactory results because of contamination of the IgM fraction with IgG (6.0%), probable aggregation of IgG (3.5%), or the persistence of chick red cell agglutinins (0.4%). Tests were performed on 134 patients with rubella confirmed by a rise of HAI antibodies. Rubella-specific IgM was found at a titre of more than eight in the sera taken from 62 of 64 patients between 10 and 29 days after the onset of the rash but in only one of the sera taken between 80 and 119 days, and in none taken later. However, specific IgM was still to be found at lower titre in the sera of 13 patients collected between 80 and 162 days after the onset of the illness. In routine diagnostic tests over three years on the serum from 479 patients with suspected acquired rubella, specific IgM was found at a titre of more than eight in 51 patients and in only 10 instances (2.1%) did a lower level pose a problem in interpretation.

A rapid immunofluorescent procedure for the detection of specific IgG and IgM antibody in sera using Staphylococcus aureus and latex-IgG as absorbents

Sera from adults with toxoplasmosis and individuals with anti nuclear antibodies were examined for the presenceof specific IgM and IgG antibodies and for the occurrence of anti-immunoglobulin ("RF") activity both before and after absorption with freeze-dried preparations of protein A-containing Staphylococcus aureus. Such absorption removed most of the IgG present in sera without interfering with the detection of IgM antibody by immunofluorescence, but was relatively ineffective in the removal of "RF". "RF" activity, demonstrable by slide agglutination, was removed by absorption with latex coated with IgG. In order to prevent the possibility of false positive IgM staining in immunofluorescence tests, it is concluded that sequential absorption with latex-IgG particles and protein A-positive staphylococci is essential. Such absorption is technically simple and can be performed on small volumes of serum.

Detection of antibody to respiratory syncytial virus by membrane fluorescence

An indirect membrane fluorescent antibody technique was established to study HEp 2 cells infected with respiratory syncytial (RS) virus. It was possible to detect IgG and IgM antibody to RS virus in the sera of patients with respiratory infections using this technique. The technique was further applied to the detection of IgA antibody to the same virus in colostrum.