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.

Rubella

Maternal rubella is now rare in many developed countries that have rubella vaccination programmes. However, in many developing countries congenital rubella syndrome (CRS) remains a major cause of developmental anomalies, particularly blindness and deafness. WHO have provided recommendations for prevention of CRS, and, encouragingly, the number of countries introducing rubella vaccination programmes has risen. However, declining uptake rates due to concerns about the measles-mumps-rubella vaccine in the UK, and increasing numbers of cases in some European countries coupled with poor uptake rates might jeopardise this progress. Surveillance of postnatally and congenitally acquired infection is an essential component of CRS prevention since rubella is difficult to diagnose on clinical grounds alone. Laboratory differentiation of rubella from other rash-causing infections, such as measles, parvovirus B19, human herpesvirus 6, and enteroviruses in developed countries, and various endemic arboviruses is essential. Reverse transcriptase PCR and sequencing for diagnosis and molecular epidemiological investigation and detection of rubella-specific IgG and IgM salivary antibody responses in oral fluid are now available.

Prenatal diagnosis of congenital rubella

In an attempt at prenatal diagnosis of fetal infection after primary rubella infection before 18 weeks of pregnancy fetal blood was taken by direct puncture under ultrasound guidance at 20-26 weeks of pregnancy from eighteen patients. Total IgM was assayed by radial immunodiffusion and rubella-specific IgM by IgM capture immunoassay. Rubella-specific IgM was detected in twelve of the eighteen fetuses. The parents decided whether to continue or terminate the pregnancy on the basis of the time of onset of maternal rubella. All six pregnancies in which rubella occurred before 12 weeks of gestation were terminated. Of the six with rubella after 12 weeks two were terminated. Among the six fetuses negative for rubella-specific IgM, five had no rubella-specific IgM at birth and no persistent IgG but one was found to be infected at birth; this false-negative diagnosis was due to sampling too early during pregnancy.

Illuminating uveitis: metagenomic deep sequencing identifies common and rare pathogens

BACKGROUND

Ocular infections remain a major cause of blindness and morbidity worldwide. While prognosis is dependent on the timing and accuracy of diagnosis, the etiology remains elusive in ~50 % of presumed infectious uveitis cases. The objective of this study is to determine if unbiased metagenomic deep sequencing (MDS) can accurately detect pathogens in intraocular fluid samples of patients with uveitis.

METHODS

This is a proof-of-concept study, in which intraocular fluid samples were obtained from five subjects with known diagnoses, and one subject with bilateral chronic uveitis without a known etiology. Samples were subjected to MDS, and results were compared with those from conventional diagnostic tests. Pathogens were identified using a rapid computational pipeline to analyze the non-host sequences obtained from MDS.

RESULTS

Unbiased MDS of intraocular fluid produced results concordant with known diagnoses in subjects with (n = 4) and without (n = 1) uveitis. Samples positive for Cryptococcus neoformans, Toxoplasma gondii, and herpes simplex virus 1 as tested by a Clinical Laboratory Improvement Amendments-certified laboratory were correctly identified with MDS. Rubella virus was identified in one case of chronic bilateral idiopathic uveitis. The subject's strain was most closely related to a German rubella virus strain isolated in 1992, one year before he developed a fever and rash while living in Germany. The pattern and the number of viral identified mutations present in the patient's strain were consistent with long-term viral replication in the eye.

CONCLUSIONS

MDS can identify fungi, parasites, and DNA and RNA viruses in minute volumes of intraocular fluid samples. The identification of chronic intraocular rubella virus infection highlights the eye's role as a long-term pathogen reservoir, which has implications for virus eradication and emerging global epidemics.

Measurement of avidity of specific IgG for verification of recent primary rubella

Sixty-four subjects' serum samples, positive or equivocal by rubella IgM assays and containing rubella IgG, were examined for the avidity of rubella IgG. Four of the sera originated from rubella reinfections; others had false-positive IgM results due to interference by parvovirus infection or by other mechanisms; and the remaining were sera from the acute phase or convalescence of primary rubella. A novel IgG avidity test, avidity-ELISA, and a semiquantitative haemolysis typing assay were used. According to the avidity-ELISA, 29 subjects had recent primary rubella (low IgG avidity), and another 29 had previous rubella immunity (high IgG avidity), whereas 6 serum samples gave borderline avidity values. Comparison of these results with pre-existing clinical records and laboratory data showed that all samples with low IgG avidity were obtained during or shortly after acute primary rubella. All sera with high IgG avidity originated from the previously immune subjects; the rubella reinfections were confined within this group. Five of the six sera with borderline avidity values were obtained within 2 months from primary rubella. In conclusion, the measurement of IgG avidity is a powerful tool for the distinction of acute or recent primary rubella from pre-existing rubella immunity, including rubella reinfections.

Rubella infection in pregnancy

Rubella is the first virus demonstrated as a teratogen. There is a high risk to develop congenital rubella syndrome (CRS) if the infection occurs in the first part of pregnancy, particularly in women without specific immunological protection. Specific therapies to prevent CRS are not available. Many developed countries have specific vaccination programs and maternal rubella is rare. However, in developing countries or where campaigns of rubella surveillance and preconceptional vaccination are inadequate, there are still cases of CRS registered despite primary possibilities of prevention. Maternal infection is not indicative of vertical transmission in 100% of cases, and damage does not necessarily occur in all cases of fetal infection. This is the reason why an adequate prenatal counselling is mandatory, particularly in cases of proven maternal infection. Advanced prenatal diagnostic techniques, invasive or not, should be offered to the women especially in order to distinguish the cases without fetal damage. Prevention of voluntary interruption of pregnancy for the latter or in case of maternal false IgM rubella antibody positivity or IgM "chronic carrier" patients is mandatory. World wide, the aim is to perform an adequate primary prevention through vaccination of childbearing age women without specific immunological protection.

Detection of measles, mumps, and rubella antibodies in saliva using antibody capture radioimmunoassay

Antibody capture radioimmunoassays were developed for detecting virus specific IgM (MACRIA) and IgG (GACRIA) to measles, mumps, and rubella and used to investigate saliva as an alternative specimen to serum for diagnosis. Saliva was collected from 63 patients with measles, 19 with mumps, and 150 with rubella, which were all clinically diagnosed and serologically confirmed. Virus specific IgM was detected in 92% of measles, 75% of mumps, and 100% of rubella saliva samples collected during the first week of illness. Between 1 and 5 weeks after onset virus specific IgM was detected in 100% of saliva specimens. After the 5th week the proportion of reactive specimens declined. The specificity of the MACRIA tests was established by testing saliva samples collected from blood donors for measles (88), mumps (88), and rubella IgM (91). All of the saliva specimens tested for measles and rubella specific IgM were unreactive, 1/88 specimens tested for mumps specific IgM contained significant reactivity. Saliva specimens collected from acute cases of MMR were tested in all 3 MACRIAs. A small proportion of saliva samples contained detectable IgM of more than one virus infection. Rubella and measles specific IgG was detected in the saliva of all cases from the 4th or 5th day of illness, respectively. Detection of mumps specific IgG was less successful. We have demonstrated that virus specific IgM can be reliably detected in saliva samples collected from acute cases of measles, mumps, and rubella and identified 1-5 weeks after onset of illness as the optimum time for collection of samples.

Differentiation of primary cytomegalovirus infection from reactivation using the urea denaturation test for measuring antibody avidity

Cytomegalovirus (CMV) is probably the most common agent of prenatal infection of the newborn, and one of 20 congenitally infected newborns shows serious symptoms. It was therefore considered important to be able to differentiate primary CMV from reactivation in pregnant females. A urea denaturation test was used to distinguish primary from secondary rubella infection in which the urea is included in the wash step of the standard IgG ELISA. This resulted in the removal of low-avidity antibodies, which are the antibodies produced early in infection. A group of CMV IgM-negative and -positive sera were tested, and all but one showed moderate to high avidity, with an avidity index reading of more than 30%. Among a group of babies 3-12 months of age, who were CMV IgM positive, 55% (16 of 29) showed low-avidity CMV antibodies. A small group of renal transplant patients and patients with clinically and laboratory-confirmed CMV gave more or less predicted avidity index results. It appears that, with the method used at this laboratory, the urea denaturation test can be applied to CMV to determine primary infection or reactivation in the majority of cases.

Outcome of confirmed periconceptional maternal rubella

61 pregnant women in whom confirmed rubella occurred from 5 weeks before to 6 weeks after the last menstrual period (LMP) were followed up prospectively. In 39, the pregnancy was terminated and the fetal tissues or mixed products of conception were examined for rubella virus. In 22, the pregnancy continued to term and cord serum was tested for specific IgM antibody. No evidence of intrauterine infection was found in 38 pregnancies in which the mother's rash appeared before, or within 11 days after, the last menstrual period. The shortest interval at which fetal infection occurred was when the rash appeared 12 days after the last menstrual period. All 10 pregnancies in which the rash appeared 3-6 weeks after the last menstrual period resulted in fetal infection: 4 of these pregnancies went to term, and all 4 infants were damaged. The risk to the fetus when rubella occurs before the mother's last menstrual period is probably negligible.

Antibody capture radioimmunoassay for anti-rubella IgM

An M-antibody capture radioimmunoassay (MACRIA) for anti-rubella IgM was developed. Under optimum conditions positive serum specimens bound up to 20 times as much radioactivity as negative specimens. Positive reactions were expressed in arbitrary units/ml by comparison with a calibration curve derived from results obtained with dilutions of a standard serum. The specificity of the assay was confirmed by testing IgM and IgG rich fractions of positive sera. One hundred and forty specimens from blood donors, patients whose sera contained rheumatoid factor and patients with acute, non-rubella, virus infections were tested by MACRIA. No significant non-specific reactions were detected. Paired sera from acute rubella (25 patients) and individual sera from suspected rubella (69 patients) were tested for anti-rubella IgM by MACRIA and by haemagglutination inhibition following sucrose-density-gradient fractionation. There was close agreement between the two methods. The capture assay was more sensitive and could be used to detect the weak IgM response in women given RA 27/3 vaccine. After the natural infection, the MACRIA was strongly positive for two months and remained weakly so for a further two months. Repeat testing of sera demonstrated good reproducibility of the assay. MACRIA proved a simple, sensitive and specific test for anti-rubella IgM and compared favourably with currently used techniques.

Use of PCR for prenatal and postnatal diagnosis of congenital rubella

A reverse transcription-nested PCR assay (RT-PCR) was evaluated for diagnosis of congenitally acquired rubella in utero and during infancy. RT-PCR was compared with virus isolation for retrospective detection of rubella virus in placental and fetal tissues obtained after termination of pregnancy following primary rubella or rubella virus reinfection. Concordant results were obtained for 85% of samples; rubella virus RNA was detected by RT-PCR alone in four samples, and rubella virus was detected by isolation alone in two samples. Samples were also obtained for prenatal diagnosis of congenital infection; rubella virus RNA was detected in three of seven chorionic villus samples and one of three amniotic fluid samples by RT-PCR, while rubella virus was isolated in only one chorionic villus sample. To demonstrate that the RNA extracted from chorionic villus samples contained amplifiable RNA, a nested RT-PCR was used to detect keratin mRNA. Rubella virus was detected in placenta in two cases in which the fetus was uninfected, and there was no evidence of rubella virus in the placenta from one case in which the fetus was infected. Thus, detection of rubella virus in chorionic villus samples by RT-PCR may not always correctly predict fetal rubella virus infection. RT-PCR was successfully used for the diagnosis of congenitally acquired rubella in infancy. Rubella virus RNA was detected in cyropreserved or formalin-fixed lens aspirates obtained from infants in India with serologically confirmed congenital rubella but not in samples from controls with inherited cataract.

Fetal infection after maternal reinfection with rubella: criteria for defining reinfection

Five cases of asymptomatic maternal reinfection with rubella are described that occurred in England and Wales during 1985-8 and resulted in intrauterine infection. The criteria for diagnosing reinfection are described. In four cases the rubella contact was with the woman's own children. Two women had therapeutic abortions, rubella virus being recovered from the products of conception, and three were delivered of infants with congenitally acquired disease. Though the risks associated with maternal reinfection with rubella are very small and being measured in a prospective study, it is hoped that the recently introduced augmented programme of rubella vaccination will reduce rubella in the community and therefore this small risk still further.

Autistic children exhibit undetectable hemagglutination-inhibition antibody titers despite previous rubella vaccination

The etiology of autism is unknown, but autism has been associated with a number of diseases, including prenatal rubella. Rubella vaccine challenge was used in an attempt to retrospectively diagnose prenatal rubella in autistic children. This test was selected because unresponsiveness of antibody titer has been reported as helpful in retrospective diagnosing of prenatal rubella. Fifteen autistic children and 8 controls matched for age were challenged with rubella vaccine. Rubella vaccine challenge did not differentiate autistic children from the control subjects. However, 5 of 13 autistic children had undetectable titers despite previous vaccine; all control subjects had detectable titers. This finding of undetectable titers in autistic children suggests these children may have an altered immune response.

Rubella-specific IgG subclass avidity ELISA and its role in the differentiation between primary rubella and rubella reinfection

An antiglobulin enzyme-linked immunosorbent assay for rubella-specific IgG1 and IgG3 was adapted to measure antibody avidity by incorporating a mild protein denaturant, diethylamine (DEA), into the serum diluent. Sera were tested at varying dilutions, both with and without DEA, if they contained sufficient specific IgG1 or IgG3. The optical density (OD) was measured and curves were plotted. The highest OD (V) was noted and halved (V/2). The distance between the OD curves at V/2 was measured as the DEA shift value. Sera were examined from people whose sera contained rubella-specific antibodies as a consequence of infection or vaccination in the distant past (24 sera), recent primary rubella (66 sera), symptomatic reinfection (11 sera) or asymptomatic reinfection (64 sera). For specific IgG1 the DEA shift value was less than 0.6 for cases of rubella in the distant past, compared with greater than 0.8 for the first month after primary infection. The maximum DEA shift value for the sera from cases of reinfection was 0.65. No serum from cases of rubella in the distant past contained sufficient specific IgG3 to estimate avidity. The sera collected within 1 month of onset of primary rubella gave DEA shift values greater than 0.7 compared with sera from reinfections, which gave DEA shift values less than 0.6, except for two sera from a case of symptomatic reinfection. Thus the assessment of specific IgG subclass avidity is of value in differentiating serologically primary rubella from reinfection.

Simultaneous IgM reactivity by EIA against more than one virus in measles, parvovirus B19 and rubella infection

BACKGROUND

A clinical diagnosis of rash-causing infections is not always possible and reliance has to be placed on serological evidence of infection, especially on the presence of specific immunoglobulin (Ig)M. However, despite the use of modern serological methods and validated commercial kits, reports appear in the literature of simultaneous IgM reactivity against more than one virus in cases of Epstein Barr virus, rubella, cytomegalovirus, human parvovirus B19 (HPV B19) and measles infections, all with implications for the pregnant woman.

OBJECTIVES

We decided to evaluate the extent of the problem in rubella, measles and HPV B19 infections in a routine diagnostic laboratory.

STUDY DESIGN

We tested sera from cases with initial clinical and serological evidence of infection with measles, HPV B19 or rubella for evidence of simultaneous IgM reactivity against more than one virus. We confirmed primary infections with specific-IgG antibody avidity tests, and subjected sera with IgM reactivity against more than one virus to avidity tests to identify which, if any, of the three viruses was the cause of the primary infection. Groups of monoreactive IgM sera were randomly selected from the presented sera to demonstrate that the avidity of the IgG specific for the other two viruses would be of high avidity compared with the low avidity of the IgG specific for the virus against which specific IgM had been detected.

RESULTS

Our results confirm that simultaneous IgM reactivity against more than one virus does occur in these three infections, and that this is unlikely to be caused by the presence of rheumatoid factor.

CONCLUSIONS

In the absence of seroconversion, reliance on specific IgM results alone for diagnosis of these infections should be avoided and tests such as specific IgG antibody avidity should also be employed. The simultaneous occurrence of IgM reactivity against more than one virus is also important for epidemiological and surveillance reasons as the widespread use of the mumps, measles and rubella vaccine makes its impact on the population. Falsely diagnosed cases of apparent measles or rubella could throw into question the efficacy of the vaccine.

Rubella antibody measured by radial haemolysis. Characteristics and performance of a simple screening method for use in diagnostic laboratories

A simple method for preparing radial haemolysis gels for rubella antibody screening is described. In use it gave clear zones of haemolysis when a standard serum was tested at dilutions down to 5.6 i.u./ml rubella antibody. In five laboratories 8404 sera were screened by the method and the results were read by comparing zones of haemolysis with that of a standard serum diluted to contain 15 i.u/ml antibody. A zone greater than or equal to 15 i.u./ml, indicating immunity, was given by 7433 (88.4%) of the sera. No zone indicating susceptibility was seen with 748 (8.9%) sera. Small zones, less than 15 i.u./ml standard, were given by 189 (2.2%) sera, and in only 34 cases (0.4%) did non-specific haemolysis interfere with the test readings. Further testing of the radial haemolysis interfere with the test readings. Further testing of the radial haemolysis negative and low positive sera by the haemagglutination inhibition test gave rise to some discrepant results which are discussed.

Rubella

Rubella is an acute illness caused by rubella virus and characterised by fever and rash. Although rubella is a clinically mild illness, primary rubella virus infection in early pregnancy can result in congenital rubella syndrome, which has serious medical and public health consequences. WHO estimates that approximately 100 000 congenital rubella syndrome cases occur per year. Rubella virus is transmitted through respiratory droplets and direct contact. 25-50% of people infected with rubella virus are asymptomatic. Clinical disease often results in mild, self-limited illness characterised by fever, a generalised erythematous maculopapular rash, and lymphadenopathy. Complications include arthralgia, arthritis, thrombocytopenic purpura, and encephalitis. Common presenting signs and symptoms of congenital rubella syndrome include cataracts, sensorineural hearing impairment, congenital heart disease, jaundice, purpura, hepatosplenomegaly, and microcephaly. Rubella and congenital rubella syndrome can be prevented by rubella-containing vaccines, which are commonly administered in combination with measles vaccine. Although global rubella vaccine coverage reached only 70% in 2020 global rubella eradiation remains an ambitious but achievable goal.

Identification of new pathogens in the intraocular fluid of patients with uveitis

Purpose

To determine infectious causes in patients with uveitis of unknown origin by intraocular fluids analysis.

Design

Case-control study.

Methods

Ocular fluids from 139 patients suspected of infectious uveitis, but negative for herpes simplex virus, varicella-zoster virus, cytomegalovirus, and Toxoplasma gondii by polymerase chain reaction and/or antibody analysis in intraocular fluids, were assessed for the presence of 18 viruses and 3 bacteria by real-time polymerase chain reaction (PCR). The ocular fluids from 48 patients with uveitis of known etiology or with cataract were included as controls.

Results

Positive PCR results were found for Epstein-Barr virus, for rubella virus, and for human herpesvirus 6 each in 1 patient and for human parechovirus in 4 patients. Of the human parechovirus–positive patients, 1 was immunocompromised and had panuveitis. The other 3 patients were immunocompetent and had anterior uveitis, all with corneal involvement.

Conclusions

Human parechovirus might be associated with infectious (kerato)uveitis.

Maturation of immunoglobulin G avidity after rubella vaccination studied by an enzyme linked immunosorbent assay (avidity-ELISA) and by haemolysis typing

Two tests were introduced recently for assessment of the avidity of rubella immunoglobulin antibodies. In the quantitative test--avidity-enzyme linked immunosorbent assay (ELISA)--IgG antibodies obtained from individuals shortly after primary infection with rubella virus are distinguished from those with past immunity by their antigen-elution characteristics. This method uses agents that disrupt hydrophobic bonds in proteins [Kamoun PP (1988): Denaturation of globular proteins by urea: Breakdown of hydrophobic bonds? Trends in Biological Sciences 13:424-425.]. In the semiquantitative, presumptive test--haemolysis typing--the low-avidity rubella-IgG antibodies are distinguished from the high-avidity antibodies by the quality of their haemolytic zones in a radial haemolysis test. In the present study, both tests were applied to sera taken before and after vaccination with two different strains (Cendehill or RA 27/3) of live attenuated rubella virus. It was found that after vaccination of previously nonimmune subjects, IgG synthesized during the first 2 months had a very low avidity; IgG avidity increased dramatically during the subsequent 4 months and less markedly between 6 and 12 months after vaccination. On the contrary, the initially high IgG avidity of previous immune vaccinees remained at an elevated level postvaccination. These results provide a basis for identification of recent primary rubella virus infections, or vaccination reactions, by the avidity of specific IgG and also for their separation from rubella reinfections.

Single-sample diagnosis of recent rubella by fractionation of antibody on Sephadex G-200 column

To facilitate the diagnosis of recent rubella infection, rubella haemagglutination inhibiting antibody has been determined in four fractions obtained by Sephadex G-200 gel filtration of samples of serum. All the 21 samples collected at the convalescent stage of the disease had varying proportions of haemagglutination inhibiting antibody in fraction 1, representing the major portion of IgM antibody whereas all but three out of 22 sera from persons with no history of recent rubella had negative titres in this fraction. The haemagglutination inhibiting titres in the three positive sera in the second group was very low as compared to the other fractions. Fractionation of sera on a Sephadex G-200 column coupled with the rubella haemagglutination inhibition test can, therefore, be used to diagnose recent rubella infection.