Rubella vaccines: past, present and future

Changes in the Epidemiology of Rubella: The Influence of Vaccine-Introducing Methods and COVID-19

Rubella is an infectious disease caused by the rubella virus. Congenital rubella syndrome is a risk for all newborns if pregnant women are infected with rubella, raising an important public health issue. Rubella is a vaccine-preventable disease, and routine immunization has been conducted in Japan. The timing of the vaccine approval did not differ from that in the United States. In 2004, endemic rubella was eliminated in the United States. However, recent rubella outbreaks have occurred in Japan. This may be related to differences in the introduction of routine rubella immunization. In Japan, routine rubella immunization was initially introduced only for junior high school girls, and the rate of susceptibility is high among males who have not received rubella vaccination, causing an outbreak. Therefore, in Japan, measures have been taken to decrease the number of susceptible males in the vaccination-free generation. The coronavirus pandemic has also affected the epidemiology of rubella as well as other infectious diseases.

Past as Prologue-Use of Rubella Vaccination Program Lessons to Inform COVID-19 Vaccination

The rapid rollout of vaccines against COVID-19 as a key mitigation strategy to end the global pandemic might be informed by lessons learned from rubella vaccine implementation in response to the global rubella epidemic of 1963-1965. That rubella epidemic led to the development of a rubella vaccine that has been introduced in all but 21 countries worldwide and has led to elimination of rubella in 93 countries. Although widespread introduction and use of rubella vaccines was slower than that for COVID-19 vaccines, the process can provide valuable insights for the continued battle against COVID-19. Experiences from the rubella disease control program highlight the critical and evolving elements of a vaccination program, including clearly delineated goals and strategies, regular data-driven revisions to the program based on disease and vaccine safety surveillance, and evaluations to identify the vaccine most capable of achieving disease control targets.

No. 203-Rubella in Pregnancy

OBJECTIVE

To provide an update on rubella and pregnancy so that health professionals remain aware of the potentially devastating effects on the developing fetus.

OUTCOMES

Rubella vaccination has been effective in virtually eliminating congenital rubella syndrome in Canada.

EVIDENCE

Medline, PubMed, and Cochrane Database were searched for articles published between 1985 and 2007.

VALUES

The quality of evidence was rated using the criteria described in the report of the Canadian Task Force on Preventive Health Care.

SPONSOR

The Society of Obstetricians and Gynaecologists of Canada.

RECOMMENDATIONS

No. 368-RUBELLA IN PREGNANCY

OBJECTIVE

To review the epidemiology, natural history, evaluation, and prevention of rubella infection during pregnancy. This will aid obstetric care providers in counseling their patients regarding potentially devastating effects on the developing fetus and the importance of vaccinating susceptible women as appropriate.

OUTCOMES

Outcomes evaluated include fetal rubella infection, maternal seroconversion and response to rubella-containing vaccines.

EVIDENCE

Medline, PubMed, EMBASE, and Cochrane databases were searched for articles in English on subjects related to rubella infection during pregnancy betweenn 1985 and 2017. Results were restricted to systematic reviews, randomized controlled trials/controlled clinical trials, and observational studies. Other (unpublished) literature was identified through searching the websites of health technology assessment and health technology assessment-related agencies, clinical practice guideline collections, clinical trial registries, and national and international medical specialty societies.

VALUATION METHODS

The quality of the evidence is rated using the criteria described in the Report of the Canadian Task Force on Preventive Health Care (Table 1). Recommendations for practice are ranked according to the method described in this Report.

GUIDELINE UPDATE

The guideline will be reviewed 5 years after publication to decide if an update is required. However, if important new evidence is published prior to the 5-year cycle, the review process may be accelerated for a more rapid update of some recommendations SPONSOR: Society of Obstetricians and Gynaecologists of Canada.

RECOMMENDATIONS

Application of Oral Fluid Assays in Support of Mumps, Rubella and Varicella Control Programs

Detection of specific viral antibody or nucleic acid produced by infection or immunization, using oral fluid samples, offers increased potential for wider population uptake compared to blood sampling. This methodology is well established for the control of HIV and measles infections, but can also be applied to the control of other vaccine preventable infections, and this review describes the application of oral fluid assays in support of mumps, rubella and varicella national immunization programs. In England and Wales individuals with suspected mumps or rubella, based on clinical presentation, can have an oral fluid swab sample taken for case confirmation. Universal varicella immunization of children has led to a drastic reduction of chickenpox in those countries where it is used; however, in England and Wales such a policy has not been instigated. Consequently, in England and Wales most children have had chickenpox by age 10 years; however, small, but significant, numbers of adults remain susceptible. Targeted varicella zoster virus (VZV) immunization of susceptible adolescents offers the potential to reduce the pool of susceptible adults and oral fluid determination of VZV immunity in adolescents is a potential means of identifying susceptible individuals in need of VZV vaccination. The main application of oral fluid testing is in those circumstances where blood sampling is deemed not necessary, or is undesirable, and when the documented sensitivity and specificity of the oral fluid assay methodology to be used is considered sufficient for the purpose intended.

Vaccination in elite athletes

Public health vaccination guidelines cannot be easily transferred to elite athletes. An enhanced benefit from preventing even mild diseases is obvious but stronger interference from otherwise minor side effects has to be considered as well. Thus, special vaccination guidelines for adult elite athletes are required. In most of them, protection should be strived for against tetanus, diphtheria, pertussis, influenza, hepatitis A, hepatitis B, measles, mumps and varicella. When living or traveling to endemic areas, the athletes should be immune against tick-borne encephalitis, yellow fever, Japanese encephalitis, poliomyelitis, typhoid fever, and meningococcal disease. Vaccination against pneumococci and Haemophilus influenzae type b is only relevant in athletes with certain underlying disorders. Rubella and papillomavirus vaccination might be considered after an individual risk–benefit analysis. Other vaccinations such as cholera, rabies, herpes zoster, and Bacille Calmette–Guérin (BCG) cannot be universally recommended for athletes at present. Only for a very few diseases, a determination of antibody titers is reasonable to avoid unnecessary vaccinations or to control efficacy of an individual’s vaccination (especially for measles, mumps, rubella, varicella, hepatitis B and, partly, hepatitis A). Vaccinations should be scheduled in a way that possible side effects are least likely to occur in periods of competition. Typically, vaccinations are well tolerated by elite athletes, and resulting antibody titers are not different from the general population. Side effects might be reduced by an optimal selection of vaccines and an appropriate technique of administration. Very few discipline-specific considerations apply to an athlete’s vaccination schedule mainly from the competition and training pattern as well as from the typical geographical distribution of competitive sites.

Determination of rubella virus-specific cell-mediated immunity using IFN gamma-ELISpot

Immunity to rubella virus (RV) is conventionally determined by measuring specific immunoglobulin G (IgG). However, several individuals may be considered immune despite undetectable antibody levels. In the present study RV-specific interferon-gamma (IFN gamma)-ELISpot and rubella-IgG-ELISA were compared in 75 young adults aged between 20 and 30 years. In a subgroup, not only rubella-like particles (RLP), but also HPV77 rubella vaccine derived antigen was used in IFN gamma-ELISpot. The results from both, ELISA and ELISpot were independent of previous encounter to RV (vaccination, exanthematous disease, or childhood infection). There was no difference between RLP and RV vaccine antigen in IFN gamma-ELISpot response, and there was no correlation between IFN gamma-ELISpot and RV-specific IgG levels. IFN gamma-producing cells were found in 78.7% of all tested persons, and 83.8% of them were positive in ELISA. In almost all individuals seronegative for RV antibody, IFN gamma-producing cells were detected. Considering both humoral and cell-mediated immune responses, a positive RV immune reaction was seen in 98.6%. The results indicate that the IFN gamma-ELISpot can provide valuable additional information in seronegative individuals.

Congenital rubella syndrome: pattern and presentation in a southern Nigerian tertiary hospital

BACKGROUND

Congenital rubella syndrome (CRS) resulting from maternal rubella infection can result in miscarriages, still birth and rubella infection of the infant. The aim of this study was to evaluate the pattern and presentation of CRS over an 8-year period as seen in the University of Port-Harcourt Teaching Hospital (UPTH), Nigeria.

METHODS

The medical records of all cases of CRS presenting to the Pediatric Department of UPTH from January 2000 to December 2007 were reviewed.

RESULTS

There were 16 394 babies delivered in UPTH from January 2000 to December 2007. Of these babies, 19 were clinically diagnosed as having CRS, but none had laboratory confirmation. They had a mean age of 5.1 +/-3.2 months (range: 1-11 months). Seventy-five percent of their mothers had presumed rubella infection during the first trimester of pregnancy. Cataract was noticed to be the most prominent systemic manifestation in 18 of the 19 babies. Other common manifestations included hearing impairment (n=14), microcephaly (n=13), patent ductus arteriosus (n=11), and low birth weight (n=10). A surge was observed in the number of babies with CRS from 2004 to 2007; however, this was not statistically significant (chi (2)=8.68, P=0.28). Unfortunately, long-term outcome of the 19 babies was not available.

CONCLUSION

CRS is commonly diagnosed at our center. Thus, mounting effective surveillance for CRS and considering the inclusion of rubella vaccine in Nigeria are of extreme importance.

Levels of rubella antibody among vaccinated and unvaccinated Portuguese mothers and their newborns

Maternal and cord sera (231 pairs) were tested to measure rubella IgG levels, using a commercial immunoassay method with final fluorescent detection (ELFA). One hundred and twenty-two women had been vaccinated against rubella. Geometric mean concentrations (GMC) were not associated with time since vaccination. GMC of rubella IgG among vaccinated and unvaccinated mothers were respectively 66.6 and 80.9IU/ml (p=0.29). The corresponding values for cord sera GMC were 140.6 and 140.2IU/ml (p=0.99). These GMC values seem to have been influenced by increased transplacental transport efficiency (TTE) among vaccinated mothers. This was observed if TTE was measured as difference or ratio of cord-maternal concentration of rubella IgG, but was only statistically significantly (p=0.02) for ratio. TTE also seemed to be higher when antibody levels in mothers were below <15IU/ml. There seemed to be some interaction between susceptibility and vaccination status, but these results should be seen with caution. We do not know of a proven biological reason to support differential TTE in vaccinated and unvaccinated mothers. The sensitivity of the lab assay might have influenced the results, such that very low antibody levels in some vaccinated mothers were underestimates of true concentrations. Our finding that 38 mothers had antibody levels considered to be below the threshold for protection highlights the importance of implementing policies to vaccinate susceptible women of childbearing age.

Significance of avidity and immunoblot analysis for rubella IgM-positive serum samples in pregnant women

A total of 512 IgM-positive serum samples from 449 pregnant women referred by microbiologists and medical laboratories for additional testing and final interpretation were collected over a 3-year period. Employment of an IgM capture enzyme immunoassay (EIA) confirmed only 31% of the initial EIA-IgM-positive samples. In order to discriminate acute rubella virus infections, which are associated with increased risk of fetal infection and embryopathy, from persistent or non-specific IgM, IgG avidity index and the presence of IgG with specificity to rubella virus E2 glycoprotein was determined by Western immunoblot. In only six patients (1.3%), a primary infection with rubella virus was diagnosed on the basis of IgM positivity, low avidity IgG, absence of E2-specific IgG in immunoblot concordant with clinical findings as well as consistent changes in follow-up samples. The serological results were not compatible with rubella re-infection. The infection status in 14 patients (3.1%) remained inconclusive even when both avidity assay and immunoblot were used, while restriction to either test did not allow a conclusive interpretation in 11.6% of patients. The use of both assays is clearly better, and therefore, recommended in IgM-positive samples.

Cytokine profile after rubella vaccine inoculation: evidence of the immunosuppressive effect of vaccination

BACKGROUND AND AIM: Immunization with live virus vaccines may cause an immunosuppression with lymphopaenia, impaired cytokine production and defective lymphocyte response to mitogenes. These abnormalities were described in subjects vaccinated against measles. This study was performed to analyse the host immune response related to immunosuppression in subjects vaccinated with live attenuated rubella vaccine. METHODS: Eighteen schoolgirls, aged 11-13 years, were vaccinated with live attenuated rubella vaccine Rudivax. Before immunization, and 7 and 30 days after, peripheral blood was collected. Cellular fractions were subjected to flow cytometric analysis, and the lymphocyte response to phytohaemagglutinin was investigated. Plasma samples were analysed for cytokines (interleukin (IL)-4, IL-10, tumour necrosis factor-alpha, and interferon-gamma) by enzyme-linked immunosorbent assay techniques. RESULTS: On day 7 after vaccination, the number of each lymphocyte subset was decreased; however, only for CD3 and CD4 lymphocytes has a significant reduction been shown. On the contrary, tumour necrosis factor-alpha and IL-10 levels markedly increased and amounted to its maximum on day 30. Simultaneously, a significant reduction in plasma interferon-gamma and a profound decrease of the lymphocyte response to phytohaemagglutinin were shown. The changes were accompanied with marked elevation of plasma IL-4. CONCLUSIONS: Our data indicate that the vaccination with live attenuated rubella vaccine results in moderate but sustained immune disturbance. The signs of immunosuppression, including defective lymphocyte response to mitogene and impaired cytokine production, may persist for at least 1 month after vaccination.

Evaluation of antibodies against a rubella virus neutralizing domain for determination of immune status

The protective immune responses against rubella virus (RV) are related to its neutralizing epitopes, an issue that is important to consider when assessing the immune status of patients with remote infection. In the present paper, we compare the antibodies detected by a synthetic-peptide-based enzyme immunoassay (EIA) with antibodies detected by the traditional technique of hemagglutination inhibition (HIA) in patients with remote RV infection. The synthetic peptide used as an antigen (SP15) represents a neutralizing epitope that corresponds to amino acids 208 to 239 of the E1 glycoprotein. The SP15-EIA was developed, all variables that affected the assay were standardized, and the test was validated using reference sera. Serum samples (n = 129) from patients with remote RV infection were tested by HIA and SP15-EIA. Discrepant sera were assayed by MEIA (IMX/Abbot). The comparison between HIA and SP15-EIA, taking HIA as the standard methodology for determining immune status, showed that SP15-EIA is very specific and sensitive for detecting protecting antibodies (specificity, 100%; sensitivity, 98.20%). This study demonstrates that antibodies against the neutralizing domain represented by SP15 would be important in the memory response after natural infection and may be a good tool in the determination of the true immune status of patients with remote infection with regard to RV.

Unseen blindness, unheard deafness, and unrecorded death and disability: congenital rubella in Kumasi, Ghana

OBJECTIVES

Although rubella serosusceptibility among women of reproductive age in West Africa ranges from 10% to 30%, congenital rubella syndrome has not been reported. In Ghana, rubella immunization and serologic testing are unavailable. Our objectives were to identify congenital rubella syndrome cases, ascertain rubella antibody seroprevalence during pregnancy, and recommend strategies for congenital rubella syndrome surveillance.

METHODS

Congenital rubella syndrome cases were identified through prospective surveillance and retrospective surveys of hospital records. A rubella serosurvey of pregnant urban and rural women was performed.

RESULTS

Eighteen infants born within a 5-month period met the congenital rubella syndrome case definitions, coinciding with a 9-fold increase in presentation of infantile congenital cataract. The congenital rubella syndrome rate for this otherwise unrecorded rubella epidemic was conservatively estimated to be 0.8 per 1000 live births. A postepidemic rubella immunity rate of 92.6% was documented among 405 pregnant women; susceptibility was significantly associated with younger age (P = .000) and ethnicity (northern tribes, P = .024).

CONCLUSIONS

Congenital rubella syndrome occurs in Ghana but is not reported. Information about congenital rubella syndrome and rubella in sub-Saharan Africa is needed to evaluate inclusion of rubella vaccine in proposed measles control campaigns.

Duration of rubella immunity induced by two-dose measles, mumps and rubella (MMR) vaccination. A 15-year follow-up in Finland

A national two-dose vaccination program with a combined measles, mumps and rubella (MMR-II) vaccine was introduced in Finland, in 1982, immunizing children at the ages of 14-18 months and 6 years. Antibody levels were determined from serial samples from a group of originally 350 children during 15 years. The latest samples were taken 15.5 years after the first vaccination and 70% of the children could still be reached. The aim of this study was to determine the kinetics of rubella antibodies induced by the MMR-II vaccine in these individuals. Rubella antibodies were analyzed from three different cohorts: Group I seronegative children (n=166) vaccinated at 14-18 months and 6 years, Group II seronegative children (n=139) and Group III seropositive children (n=16) vaccinated at 6 and 11-13 years. Samples collected 0-9 years after vaccination were analyzed by hemolysis-in-gel (HIG) and later samples by enzyme immunoassay (EIA) techniques. The primary vaccination induced 100% seropositivity in vaccinees with a mean zone diameter of 10 (+/-1.3), 10.2 (+/-1.1) and 11.5 (+/-0.9) mm, in Groups I, II and III, respectively. The seropositivity rate was still high at 15 years, 99%, 100% and 100% with the geometric mean titer 23, 46 and 105 IU/ml, respectively. At 15 years, antibody levels <15 IU/ml which is the suggested protective level, were found in 31, 9 and 0% of children in Groups I, II and III, respectively. Because almost a third of the individuals in Group I now, at the age of 17 years, had low levels of rubella antibodies, it is possible that rubella infections may re-emerge during pregnancy. A careful surveillance including serological follow-up is therefore very important.

Prevention of transplacental transmission of moderate-virulent classical swine fever virus after single or double vaccination with an E2 subunit vaccine

The use of a vaccine against classical swine fever virus (CSFV) during an outbreak of CSF should lead to a reduction in the horizontal or vertical transmission of CSFV. The reduction of vertical, i.e. transplacental, transmission of a moderate-virulent strain of CSFV from the sow to its offspring was studied in sows vaccinated once or twice with a CSFV E2 subunit vaccine. Two groups of nine sows were vaccinated with one PD95 dose of the E2 subunit vaccine, approximately four weeks before insemination. A third group of nine inseminated sows served as controls. One group of nine sows were vaccinated again at two weeks after insemination. At ten weeks after the primary vaccination, approximately six weeks after insemination, all 27 sows were challenged intranasally with 10(5) TCID50 of a moderate-virulent strain of CSFV, the Van Zoelen strain. The sows were euthanized at five weeks after challenge, and samples from the sows and fetuses were collected for detection of CSFV. All 27 sows were in gestation at the time of slaughter, CSFV was detected in the fetuses of all unvaccinated sows but it was not detected in any of the samples collected from fetuses of the double-vaccinated sows. Virus was however recovered from the fetuses of one out of nine sows vaccinated once. All the sows, except four double-vaccinated sows, developed CSFV Erns antibodies. Transplacental transmission of CSFV was reduced significantly (p <0.001) in all vaccinated sows. When the results from the experiment were extrapolated to a herd level, it could be concluded that, with 95% certainty, approximately 11% (single vaccination) or 0% (double vaccination), confidence intervals of 0.01-0.44 and 0.0-0.30 respectively, of the pregnant sows would still not be protected against vertical transmission of moderate-virulent CSFV. We conclude that vaccination with the CSFV E2 subunit vaccine can reduce the transmission of moderate-virulent strain of CSFV from the sow to its offspring significantly.

Increase in congenital rubella occurrence after immunisation in Greece: retrospective survey and systematic review

OBJECTIVE

To describe the events leading to the epidemic of congenital rubella syndrome in Greece in 1993 after a major rubella epidemic.

DESIGN

Retrospective survey and systematic review.

SETTING

Greece (population 10 million), 1950-95.

SUBJECTS

Children, adolescents, and women of childbearing age.

RESULTS

Around 1975 in Greece the measles, mumps, and rubella vaccine started being given to boys and girls aged 1 year without policies to attain high vaccination coverage and to protect adolescents and young women. During the 1980s, vaccination coverage for rubella remained consistently below 50%, and the proportion of pregnant women susceptible to rubella gradually increased. In 1993 the incidence of rubella in young adults was higher than in any previous epidemic year. The epidemic of congenital rubella that followed, with 25 serologically confirmed cases (24.6 per 100 000 live births), was probably the largest such epidemic in Greece after 1950.

CONCLUSIONS

With low vaccination coverage, the immunisation of boys and girls aged 1 year against rubella carries the theoretical risk of increasing the occurrence of congenital rubella. This phenomenon, which has not been previously reported, occurred in Greece.

Sequence variation in 5' termini of rubella virus genomes: changes affecting structure of the 5' proximal stem-loop

Variation within a 523 nucleotide region proximal to the 5' terminus of seven rubella virus strains has been analysed. Compared to the Therien strain twenty sites of nucleotide variation have been identified, three of which are in the 5' untranslated region. Individual strains have between three and nine nucleotide differences, only three of which result in amino acid substitutions. TO-336 has a serine for threonine at amino acid (aa) 42 and CM arginine for histidine at aa 159. RA27/3 has arginine for lysine at aa 3 and serine for threonine at aa 42. Nucleotide differences which affect a stem-loop structure reported to be important for binding of host cell proteins have been identified.

Twenty years' experience of rubella vaccination in Sweden: 10 years of selective vaccination (of 12-year-old girls and of women postpartum) and 13 years of a general two-dose vaccination

Two different strategies for the prevention of rubella-induced malformations have now been practised in Sweden, both reaching 90% or more of the target populations. The first was initiated in 1973-1974 and targeted schoolgirls, susceptible women after pregnancy and women at special risk. The second programme-a two-dose measles, mumps, rubella vaccination (MMR) of both boys and girls at the ages of 18 months and 12 years-was introduced in 1982. The percentage of susceptible pregnant women was gradually reduced from 12% in 1975 to 2.8% in 1987 and to just below 2% in 1994. The majority of the non immune are unvaccinated, these being either Swedes born before 1963 or immigrants. Before 1974 on average 14 severely rubella damaged children were reported yearly. Between 1975 and 1985 only a mean of two cases per year were recorded. Since 1985 no child with the rubella syndrome has been registered.

Control of rubella and congenital rubella syndrome (CRS) in developing countries, Part 2: Vaccination against rubella

In 1995-96 we conducted a review of rubella immunization strategies. Worldwide, 78 countries (more than one-third) reported a national policy of using rubella vaccine. This was closely related to country economic status. Based on the United Nations country classification, rubella vaccine is used in 92% of industrialized countries, 36% of those with economies-in-transition, and 28% of developing countries. Cases of congenital rubella syndrome (CRS) may be prevented as follows: by providing direct protection to women and/or schoolgirls (a selective vaccination strategy); by vaccinating boys and girls to provide indirect protection by reducing the transmission of rubella virus (a childhood vaccination strategy); or by a combination of these approaches (a combined strategy). A combined strategy was most commonly reported (60% of countries); seven countries (9%) reported a selective strategy; and 24 countries (31%) reported only childhood immunization. Experience has shown that it is essential to include vaccination of women of childbearing age in any rubella control strategy. Childhood vaccination alone may pose a risk of an increase in CRS cases. Although many countries have introduced rubella vaccine, few report any data on the impact of vaccination. Countries using rubella vaccine need to establish surveillance for rubella and CRS and monitor coverage in each of the target groups.

Rubella reimmunization: comparative analysis of the immunoglobulin G response to rubella virus vaccine in previously seronegative and seropositive individuals

Rubella virus (RV)-specific immunoglobulin G (IgG) antibodies were studied in military recruits undergoing unselected immunization with live attenuated measles, mumps, and rubella virus (MMR) vaccine. Three different whole-RV enzyme immunoassays (EIAs) and an epitope-specific EIA with a synthetic peptide (BCH-178c) representing a heutralization domain on the RV E1 envelope protein were used. Before vaccination, 84.2, 87.7, and 84.5% of the subjects tested (n = 399) were found to be seropositive (> 10 IU/ml or assay equivalent) by the three whole-RV EIAs, respectively, while only 82.5% were seropositive by the BCH-178c EIA. Although prevaccination seropositivity rates were similar for the whole-RV EIAs (sensitivity, 94 to 100%), many sera considered seropositive by the whole-RV EIAs had E1 peptide EIA antibody levels of < 10 IU/ml (sensitivity, 77.4 to 80.7%). One month after vaccination, 97.8, 97.2, and 93.5% of the subjects who were followed (n = 356) were seropositive by the three whole-RV EIAs, respectively, while 89% had BCH-178c peptide-specific IgG titers of > 10 IU/ml. After vaccination, depending on the assay used, up to 20.6% of initially seropositive individuals exhibited a greater than fourfold increase in RV-specific IgG, while up to 47.3% showed a greater than twofold increase. Increased antibody titers after vaccination (seroboosting) were most frequently associated with low levels of BCH-178c peptide-specific IgG before vaccination. RV protein-specific IgG was also studied by immunoblot assays in a subset (n = 56) of individuals receiving the MMR vaccine. Of these, 89.4 and 91.1% exhibited RV protein (E1, E2, and C protein)-specific IgG before and after vaccination, respectively. Seroboosting (two- to fourfold increase in EIA titers of individuals seropositive by the whole-RV EIA before vaccination) was usually accompanied by a shift in the IgG immunoblot pattern from a single (E1) to multiple (E1-E1, E1-C, or E1-E2-C) specificities, suggesting exposure of new epitopes as a result of viral replication.

PCR for detection of rubella virus RNA in clinical samples

A reverse transcription nested PCR (RT-PCR) assay for the detection of rubella virus RNA using primers from the E1 open reading frame was established. This assay was found to be sensitive (detecting approximately two synthetic RNA copies and RNA extracted from 0.1 50% tissue culture infective dose of rubella virus) and specific; five wild-type rubella strains and four vaccine strains were detected, and no nonspecific amplification of 16 other RNA viruses or RNAs from seven cell types occurred. Rubella virus RNA was detected in 12 pharyngeal swabs from patients with serologically confirmed rubella; these RT-PCR results were in complete agreement with virus isolation. Analysis of products of conception obtained after confirmed primary maternal rubella infection by RT-PCR gave 92% agreement (12 of 13 samples) with virus isolation. No false-positive results were obtained. The potential use of this assay for prenatal diagnosis of congenital rubella infection and for investigating aspects of the pathogenesis of chronic disease is discussed.

A lymphocyte transformation assay for the diagnosis of congenital rubella

A rubella-specific lymphocyte transformation assay, using cryopreserved mononuclear cells, has been developed and used to evaluate specific responses among 21 children with congenitally acquired rubella (CAR), 25 healthy control children and 10 children with sensorineural deafness of unknown aetiology. Although all 21 children with CAR were seropositive, 12 (57.1%) failed to respond to rubella antigen in the transformation assay. Negative in vitro lymphocyte transformation responses were detected significantly more frequently among congenitally infected children below 3 years of age. Thirteen of the 25 (52%) control children were seropositive; only one of these seropositive children (7.6%) gave a negative transformation response. A negative rubella-specific lymphocyte transformation response in a seropositive child, particularly when aged 3 years or younger, is therefore suggestive of CAR. Four of the 10 children with deafness of unknown aetiology were rubella seropositive but gave negative responses in the transformation assay, suggesting that these children had CAR. Our assay may provide a very useful test for retrospective diagnosis of CAR, particularly in children under the age of 3.