The production of monoclonal antibodies to rubella haemagglutinin and their use in antibody-capture assays for rubella-specific IgM

Monoclonal antibodies to the haemagglutinin HA1 subunit of the pandemic influenza A/H1N1 2009 virus and potential application to serodiagnosis

In order to provide specific serological reagents for pandemic influenza A/H1N1 2009 virus, monoclonal antibodies (Mabs) to recombinant haemagglutinin component HA1 (rHA1) were generated after fusing spleen cells from a mouse immunized with rHA1 protein derived from influenza strain A/California/06/09 H1N1 with a mouse myeloma cell line. Five hybridoma clones secreting Mabs specific for the rHA1 protein derived from pandemic influenza A/H1N1 2009 and not for rHA1 from seasonal H1N1 influenza strains A/Brisbane/59/07 and A/Solomon Islands/03/06 were identified by EIA. Mabs 7H4, 9A4, and 9E12 were reactive in Western blots with full length rHA and/or rHA1 subunit derived from A/California/06/09 strain. Only Mab 1F5 inhibited haemagglutination of turkey red blood cells with recombinant NIBRG-121 virus derived from A/California/07/09, but did not react in Western blots. Immunostaining of MDCK cells infected with NIBRG-121 was localized to the membrane/cytoplasm for four of the reactive Mabs. The differing reactivity of the Mabs in Western blots, immunostaining, EIA, and haemagglutination inhibition assay suggest that at least four of the five Mabs recognize different epitopes on HA1 of the pandemic influenza A/H1N1 2009 virus. Ferret antisera to pandemic influenza A/H1N1 2009 (A/England/195/09 and A/California/07/09 strains) and sera from human subjects vaccinated with Influenza A (H1N1) 2009 Monovalent Vaccine (CELTURA®, Novartis Vaccines, Germany), inhibit binding of 1F5-HRP to biotinylated rHA1 derived from A/California/06/09 in a competitive EIA, suggesting that the epitope recognized by this Mab also evokes an antibody response in infected ferrets and vaccinated humans.

A 'first loop' linear epitope accessible on native hepatitis B surface antigen that persists in the face of 'second loop' immune escape

Murine monoclonal antibodies (mAbs) were raised following immunization with native mutant hepatitis B surface antigen (HBsAg) purified from human sera. A set of antibodies binding to a linear epitope carried between residues 121 and 129 of the s region was demonstrated. These antibodies were shown by cross-competition assays to bind to a single epitope whose antigenicity was influenced by the TTP motif lying between residues 125 and 127. This first loop epitope remained accessible on the surface of HBsAg in spite of major second loop mutations abrogating the normal a conformational epitopes. The mAb and its binding region in the first loop are important diagnostically and may represent an importance immunological target, one that is stable in the face of immunologically driven escape.

Detection of rubella virus-specific immunoglobulin G in saliva by an amplification-based enzyme-linked immunosorbent assay using monoclonal antibody to fluorescein isothiocyanate

An immunoglobulin G (IgG)-capture enzyme-linked immunosorbent assay (ELISA) for rubella virus is described. The assay uses a fluorescein isothiocyanate (FITC)-anti-FITC amplification system. The detection limit of the ELISA was approximately 7 IU of rubella virus-specific IgG per ml of serum sample. For saliva samples the performances of the capture ELISA and previously described radioimmunoassay were assessed, and the results of those two assays were compared to the rubella virus-specific IgG result obtained by a commercial ELISA (Behring Enzygnost) with a panel of paired serum and saliva samples. This comparison showed that the capture ELISA with saliva was more sensitive than the radioimmunoassay and that the results correlated better with the serum IgG result than the results of the radioimmunoassay did, with an overall sensitivity of 82% and a rank correlation of 0.68, whereas the sensitivity and rank correlation for the radioimmunoassay were 74% and 0.45, respectively. For subjects of 10 years of age or younger, the ELISA with saliva had a sensitivity of 94% and a specificity of 100% compared to the results of the ELISA (Behring Enzygnost) for rubella virus-specific IgG with corresponding serum samples. The sensitivity was much lower for subjects ages 17 years or older. The assay may have wider epidemiological use with saliva specimens, particularly those from children.

Characterisation of a panel of monoclonal antibodies raised against recombinant HCV core protein

Hepatitis C virus (HCV) has as yet no practical culture system so any antigen or antibody studies must be carried out using recombinant antigens. In this study, HCV core sequence was amplified by PCR, inserted into pRSET, and expressed in E. coli. The resultant core protein was purified using nickel affinity chromatography which bound the six histidine tag attached to the N-terminus of the protein. After elution in imidazole buffer, the core protein was used to immunise Balb/c mice and monoclonal antibodies against HCV core were raised. Six monoclonals were examined in a variety of assays. All of them recognised the p27 kDa protein which they were raised against and 2D2 and 3D7 recognised the core component of an HCV Recombinant Immunoblot Assay (RIBA). None of the antibodies recognised the linear peptides in an Innolia HCV assay. 2D2 showed cytoplasmic granular staining in 1-5% of cells in frozen section of HCV infected livers. Cross-competition assays between themselves and human anti-HCV core positive sera divided the antibodies into two main groups (I and II), with a sub-division of group I into a and b. Group I antibodies were unable to be inhibited by human anti-HCV sera whereas group II antibodies were inhibited by these sera (up to 62%). Epitopes recognised by all the monoclonals were probably conformational with the group I epitope being located within the first 105 amino acids of the core sequence and the group II epitope between amino acids 105 and 160.

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.

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.

Salivary antibody detection in epidemiological surveys: a pilot study after a mass vaccination campaign against rubella in São Paulo, Brazil

The sensitivity and specificity of salivary rubella antibody detection was investigated using samples collected from 301 children after a mass vaccination campaign in the state of São Paulo, Brazil. Saliva samples were collected by 2 different methods: directly dribbling into a container or using a commercial collecting device. Corresponding finger-prick blood samples were collected on filter paper. Rubella specific immunoglobulin G (IgG) was measured in saliva by antibody capture radioimmunoassay and in blood samples by indirect enzyme-linked immunosorbent assay. The detection of salivary rubella specific IgG showed good correlation with the detection of rubella antibody in the blood samples. For both collecting techniques the predictive value for a positive saliva test was > 99% compared with the results from the blood tests. However, the predictive value for a negative saliva test was only 58.3% for a dribbled sample, compared to 100% for saliva collected using the commercial device. Moreover, collecting saliva by dribbling from children less than 4 years old was difficult. The detection of rubella specific IgG in saliva collected using a commercial device proved to be sensitive and specific in this epidemiological study, encouraging its more widespread application as a means of surveillance after mass vaccination.

Molecular biology of rubella virus

This chapter summarizes the present medical significance of rubella virus. Rubella virus infection is systemic in nature and the accompanying symptoms are generally benign, the most pronounced being a mild rash of short duration. The most common complication of rubella virus infection is transient joint involvement such as polyarthralgia and arthritis. The primary health impact of rubella virus is that it is a teratogenic agent. The vaccination strategy is aimed at elimination of rubella and includes both universal vaccination of infants at 15 months of age with the trivalent measles, mumps, rubella (MMR) vaccine and specific targeting with the rubella vaccine of seronegative women planning pregnancy and seronegative adults who could come in contact with women of childbearing age, although it is recommended that any individual over the age of 12 months without evidence of natural infection or vaccination be vaccinated. Medically, the current challenge posed by rubella virus is to achieve complete vaccination coverage to prevent resurgences.

A comparison of the binding of biotin and biotinylated macromolecular ligands to an anti-biotin monoclonal antibody and to streptavidin

A competitive enzyme immunoassay was used to study the binding of biotinylated macromolecular ligands and d-biotin to an anti-biotin monoclonal antibody and to streptavidin. Solid phase BSA-c-biotin competed with biotin or biotinylated macromolecular ligands in solution for receptor binding. The concentration of d-biotin required to inhibit streptavidin binding to solid phase BSA-c-biotin by 50% was 11.5 pM. This streptavidin-biotin interaction was taken as having an affinity/avidity index of 100 and all other receptor-ligand interactions were calculated relative to this. The avidity indices calculated for streptavidin interactions with BSA-c-biotin and IgG-biotin were 17.6 and 6.6 respectively, whereas for anti-biotin the values for these ligands were 20.5 and 19.9 respectively. The interaction of anti-biotin with d-biotin had an affinity index of 0.001. Although streptavidin has the greatest binding affinity for d-biotin, its avidity for biotinylated ligands was considerably lower and comparable to that observed for anti-biotin-biotinylated macromolecule interactions.

Characterization of a nested polymerase chain reaction assay for detection of parvovirus B19

The characterization and application of a nested polymerase chain reaction (PCR) assay for the detection of human parvovirus B19 DNA is described. The assay was evaluated with 149 diagnostic serum samples (collected up to 150 days after the onset of symptoms) previously tested by dot blot hybridization for B19 DNA and by class-specific capture radioimmunoassays for the detection of B19 immunoglobulin M (IgM) and IgG. B19 DNA was detectable by the PCR in 70% of the sera. There was a statistically significant association between the detection of B19 DNA by PCR and high B19 IgM values (P < 0.005), low B19 IgG values (P < 0.05), and a short interval between onset of symptoms and serum collection (P < 0.005). Serial serum samples, throat swabs, and peripheral blood mononuclear cells collected from 10 individuals during an outbreak of parvovirus B19 were also tested by the nested PCR. B19 DNA was detectable in the throat swabs at the time of the clinical illness and in the peripheral blood mononuclear cell fraction up to the end point of the study 6 months after infection. The location of the B19 DNA could not be determined in cytocentrifuge preparations of peripheral blood mononuclear cells with nonisotopic in situ hybridization and immunolabelling.

Monoclonal antibodies for the identification of herpesvirus simiae (B virus)

To differentiate between B virus and HSV isolates from monkeys and man monoclonal antibodies (mabs) were produced to herpesvirus simiae (B virus) and herpes simplex type 1 and 2 (HSV-1 and HSV-2). Mabs were tested by indirect immunofluorescence (IFAT) for reactivity against herpesviruses from Asiatic monkeys (B virus), African monkeys (SA 8 virus), and man (HSV-1, HSV-2, varicella-zoster virus, cytomegalovirus, and Epstein-Barr virus). Mabs could be divided into groups A-E displaying specific reactivity for B virus (A); reactivity with both B virus and SA 8 but not HSV (B); reactivity with B virus, SA 8 virus and HSV strains (C); specific reactivity with HSV-1 (D); and specific reactivity with HSV-2 (E). Two of the B virus specific mabs were able to differentiate between cynomolgus and rhesus strains of B virus. None of the mabs reacted with human varicella-zoster virus, cytomegalovirus, or Epstein-Barr virus. A panel of mabs for the unequivocal identification of B virus isolates from monkey or man is proposed.

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.

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.

Monoclonal antibodies define linear and conformational epitopes of HIV-1 pol gene products

Purified recombinant reverse transcriptase (RT) from human immunodeficiency virus type 1 (HIV-1) was used to raise 21 monoclonal antibodies with anti-RT specificities. The antibodies were characterized using Western blotting against native virus and recognized either the p66 or p66, p51 components of RT. Further immunoblotting using either cyanogen bromide fragmented RT or truncated mutants of RT along with cross-competition studies enabled the location of various immunogenic regions of RT to be identified. Three antibodies recognized a linear epitope in the N-terminal region (amino acids 128-176). Also, a neutralizing RT antibody recognized a conformational epitope in this region. Three monoclonals had epitopes mapped to linear sequences in the RNase H region at the C-terminus of the RT. Another neutralizing antibody, also requiring folding of the RT protein had its epitope more centrally located (231-353). Of the remaining 13 monoclonals, 7 were roughly located in the C-terminal region and required folding of the protein for epitope recognition and only three of the remaining six could be mapped to conformational epitopes in N-terminal and central regions of the RT. None of the antibodies tested recognized HIV-2 RT products p68 and p55 in Western blot.

Detection of rubella virus in amniotic fluid by electron microscopy

We report in this paper the observation of rubella virus by electron microscopy in an amniotic fluid sample, collected from a pregnant woman with rubella infection. Virological investigations by inoculation of cell cultures with amniotic fluid and fetal blood remained negative, due probably to the presence of neutralizing antibodies in the samples. Electron microscopy is a rapid but weakly sensitive method to detect viruses in clinical specimens. However, this unusual observation would indicate that in some cases electron microscopy could be a useful technique to evidence a fetal rubella infection.

Evaluation of urinary antigen ELISA for diagnosing Legionella pneumophila serogroup 1 infection

The enzyme linked immunosorbent assay (ELISA) described was developed to detect a soluble antigen in the urine of patients with Legionnaires' disease caused by Legionella pneumophila serogroup 1 (L.pn 1). The assay was evaluated and showed good specificity (100%) and intra-assay reproducibility. Antigen was detected in the urine of 93 (77%) of 120 patients, overall, and in 86% of patients from whom a specimen obtained within seven days of onset of illness was available. On all but one occasion the first urine sample taken from a patient for whom a positive ELISA result was obtained, was itself positive. In one case antigen was not detected at four days but was present on the fifth day after onset of symptoms. In two patients urinary antigen was detectable as early as two days after onset of symptoms. In another the antigen persisted for at least 60 days. More than half the patients, however, had stopped producing detectable antigen within 14 days of onset of symptoms. It is therefore important that where Legionnaires' disease is suspected urine is collected as early as possible in the course of the disease.

A prospective study of viral and mycoplasma infections in chronic inflammatory bowel disease

Seventy-two children with chronic inflammatory bowel disease were investigated for infections with various viruses and Mycoplasma pneumoniae, Chlamydia psittaci, and Coxiella burnetii to determine whether these pathogens are associated with acute onset exacerbations. Altogether 54 infections were identified serologically, of which 23 (42.6%) were associated with exacerbations. This corresponded to 24.2% of the recorded exacerbations during the study period. The respiratory pathogens accounted for 59.3% of the infections and 43.8% of these were associated with gastrointestinal symptoms. This is consistent with the observation that up to 40% of the exacerbations were associated with symptoms of antecedent or concurrent infection, most commonly involving the respiratory tract. Rubella virus, Epstein-Barr virus, and adenovirus were associated with acute exacerbations in 5 children. Thus, common pathogens were frequently associated with exacerbations and account for a large proportion of the commonly reported symptoms of a concurrent infection. The possible causal relationship between these pathogens and exacerbation of inflammatory bowel disease is discussed. Reactivation of latent herpesviruses was identified in 4 children with active disease and indicates that the converse relationship may also occur.

Erythema infectiosum in a primary school: investigation of an outbreak in Bury

Between January and April 1987, 97 of 302 (32%) children attending a primary school in Bury, Lancashire, were affected by an exanthematous illness. The duration and extent of the episode caused considerable local interest and anxiety. Examination of 6 serum specimens obtained during the subsequent investigation demonstrated evidence of recent Human Parvovirus B19 infection in 3 children and 1 teacher. No evidence of recent rubella virus infection was found. The investigation of the episode is discussed in the context of problems which may occur in the management of similar outbreaks.

The FITC-anti-FITC system is a sensitive alternative to biotin-streptavidin in ELISA

In a model ELISA system alkaline phosphatase (AP) absorbed onto microtitre wells was employed as the target antigen. The antigen was then reacted with a monoclonal antibody to AP either unlabelled or labelled with (a) FITC and (b) biotin. The bound anti-AP was then detected with horseradish peroxidase (HRP) conjugates of polyvalent anti-mouse IgG, and the FITC and biotin anti-AP conjugates with HRP conjugates of a monoclonal anti-FITC or streptavidin respectively. The FITC-anti-FITC system proved to be of similar sensitivity to the biotin-streptavidin system detecting 140 amol compared to 350 amol of antigen. Both these methods of antigen detection were superior to the anti-mouse IgG reagent (2100 amol). In contrast to biotinylated antibodies, FITC-labelled antibodies are highly coloured and fluorescent. These features aid the preparation, purification and characterisation of conjugates. In addition, very low non-specific binding is encountered with enzyme conjugates of anti-FITC and this may confer an advantage over enzyme conjugates of avidin/streptavidin reagents.

Detection of rubella virus in fetal and placental tissues and in the throats of neonates after serologically confirmed rubella in pregnancy

From 35 therapeutic abortions performed because rubella had occurred at 2-19 weeks of pregnancy, 120 fetal organs, 12 specimens of mixed products of conception, and 15 placentae were tested for rubella virus. Virus was isolated from 10 out of 11 fetuses (91 per cent) from women infected at 2-8 weeks, from 5 out of 8 (63 per cent) infected at 9-10 weeks, and from 2 out of 16 (13 per cent) infected at 11-19 weeks. Hybridization tests for viral RNA on 39 fetal organs from eight cases revealed infection in four additional fetuses. Virus was isolated from only 3 out of 15 aborted placentae, but hybridization tests on six placentae revealed infection in three additional specimens. Hybridization was superior to virus isolation for detecting rubella infection in products of conception and is therefore potentially the better method for examining chorionic villus biopsies. Rubella virus was isolated from the throats of 4 out of 9 infants (44 per cent) infected during the first 12 weeks of gestation, but from none of 13 infected after 17 weeks. Infants in the latter group are unlikely to infect susceptible contacts.

In vivo expression of rubella antigens on human leucocytes: detection by flow cytometry

Flow cytometry has been used to detect in vivo expression of rubella antigens on human leucocytes. Sequential samples of peripheral blood were obtained from four volunteers with naturally acquired rubella and five persons immunised with RA27/3 rubella vaccine. Leucocytes were stained for rubella antigens using a pool of rubella monoclonal antibodies. Rubella antigens were detected on the leucocytes of all four volunteers with naturally acquired rubella between 1 and 13 days after onset of illness. Viral antigens were expressed more frequently on the monocyte (9-51%) than the lymphocyte (less than 1-4%) and granulocyte (less than 1-3%) populations. Among the vaccines, rubella antigens were detected on the leucocytes of four of the five volunteers between 5 and 12 days after immunisation. The expression of viral antigens was more transient and the proportion of cells exhibiting rubella-specific fluorescence considerably lower following vaccination (1-12%) than natural infection (9-51%). Our results demonstrate that flow cytometry provides a rapid and sensitive analytical technique for detecting viral antigens on leucocytes from infected persons. Leucocytes may play an important role in the pathogenesis of rubella infection.

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.

A sensitive method of detecting proteins on dot and Western blots using a monoclonal antibody to FITC

Monoclonal antibodies to FITC were produced and shown to be specific for the fluorochrome. Molecular weight marker proteins labelled with FITC could be detected after SDS-PAGE and transfer onto nitrocellulose using anti-FITC followed by an anti-mouse IgG-alkaline phosphatase conjugate. The molecular weight of an antigen common to Legionella pneumophila and recognised by a monoclonal antibody could be determined accurately on a Western blot when FITC labelled markers were used as internal standards. The FITC-anti-FITC system was shown to be extremely sensitive, detecting 23.7 amol of BSA-FITC conjugate (equivalent to 1.42 x 10(7) molecules of FITC) in a dot blot assay.

Maternal rubella at St Thomas' Hospital in 1978 and 1986: support for augmenting the rubella vaccination programme

The effects of the rubella epidemics in 1978 and 1986 among patients attending antenatal clinics at St Thomas' Hospital were compared. Although many pregnant women who had been exposed to rubella-like illnesses were investigated in both 1978 (269) and 1986 (160), the number of cases of maternal rubella was substantially lower in 1986 (1) than in 1978 (17). Rubella vaccination of 11-14-year-old girls was introduced in the United Kingdom in 1970, but 10% of our patients were susceptible and only 36% gave a definite history of vaccination. Despite the smaller number of maternal rubella cases, substantial resources were expended on assessing patients who had been exposed to or who presented with rubella-like illnesses. In 1978 an intensification of the selective rubella vaccination campaign was recommended, but experience in the 1986 epidemic supports the view that the programme should be augmented by vaccination of preschool children with a combined measles, mumps, and rubella vaccine, with a view to rubella eradication.

Serological study of rubella-like illnesses

We investigated 627 patients who within a period of 2 1/2 years had had a rubelliform rash and/or symptoms of arthritis and arthralgia. Sera from these patients were investigated for evidence of rubella, human parvovirus B19 (HPV), and measles infection with methods to detect specific IgM and IgG antibodies. Complement fixation tests were used to screen for a wide range of other infectious agents. We detected 229 cases of rubella, 43 cases of HPV infection, 7 cases of measles, and 9 cases of infection by various other aetiological agents. This left a large proportion of rubelliform rashes, 54% (339 cases), whose aetiology was unknown. This study confirmed that the diagnosis of rubella on clinical grounds alone is unreliable. Many (6.8%) of the rashes in the study were due to HPV infection, and the seasonal incidence was the same as for rubella. There was considerable overlap between the features of rubella and HPV infections, although in adults arthralgia occurred more frequently in HPV infections than in rubella. In all cases HPV infection was self-limiting, although, as in rubella, symptoms can be prolonged and one adult's disease lasted almost 9 months. Purpura was noted in only one patient with HPV infection. In this study three patients had HPV infection during pregnancy. Two patients spontaneously aborted one month later. The third patient progressed to full term and delivered a healthy baby.

The development of an M antibody capture ELISA for rubella IgM

An M antibody capture enzyme-linked immunosorbent assay for rubella IgM was developed. The enzyme label was prepared from a monoclonal antibody raised against rubella haemagglutinin (Tedder et al., 1982). Paired sera from acute rubella infections and vaccines as well as sera from blood donors, antenatal patients and patients whose sera contained rheumatoid factor and patients with acute non-rubella infections were tested by this method.

The impact of a rubella prevention policy on the outcome of rubella in pregnancy

Surveillance of rubella vaccination in schoolgirls has continued intensively in Edinburgh since 1970. Screening for rubella antibody of all women attending antenatal clinics has been available since 1974. The analysis of cases of rubella occurring in pregnancy during an outbreak in 1979 confirmed the efficacy of schoolgirl vaccination in the city but indicated poor implementation of postnatal vaccination. Eighteen (67%) of 27 proven cases occurred in women who were screened in previous pregnancies and not immunized. Of the total of 13 liveborn infants the only two with congenital rubella defects were born to mothers in this group. Rubella immunization of schoolgirls and women of childbearing age must receive continued intensive effort if the problems of rubella in pregnancy are to be eradicated.

Human and monoclonal antibodies to hepatitis B core antigen recognise a single immunodominant epitope

Monoclonal antibodies were raised against hepatitis B core antigen (HBcAg) synthesized in Escherichia coli. They identified a single immunodominant determinant on both liver-derived and E. coli-derived HBcAg. Cross-inhibition studies demonstrated that HBsAg-containing human sera which contained antibodies to HBcAg (anti-HBc) together with either hepatitis B e antigen (HBeAg) or its antibody (anti-HBe) essentially only recognised the same single determinant as the murine antibodies. The identification of a single dominant HBcAg determinant may be important if future hepatitis B virus vaccines contain HBcAg.

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.

Public Health Laboratory Service IgM antibody capture enzyme linked immunosorbent assay for detecting rubella specific IgM

A total of 468 sera were selected for the evaluation of the Public Health Laboratory Service's IgM antibody capture enzyme linked immunosorbent assay kit (MACELISA) for detecting rubella specific IgM. The results obtained were compared with those obtained by IgM antibody capture radioimmunoassay (MACRIA). Sera from patients with primary postnatal rubella, congenital rubella, remote rubella, infectious mononucleosis, and recent infection with other agents were included, in addition to sera taken after rubella immunisation and sera containing rheumatoid factor and rubella specific IgG antibody. The assay exhibited a similar ability and comparable specificity to MACRIA for detecting rubella specific IgM antibody. The Public Health Laboratory Service MACELISA can be recommended if, as for all assays that detect rubella specific IgM, all the available clinical and serological data are taken into account when the results are interpreted.

Detection of both hepatitis B e antigen and antibody in a single assay using monoclonal reagents

Monoclonal antibodies raised against HBeAg were used to develop a HBeAg and anti-HBe detection assay. Monoclones containing anti-HBe were used both for the coating of the solid phase and for the fluid phase label in a sandwich type assay. The percentage binding of 125I-labelled anti-HBe to serum HBeAg was much greater than that seen in a similar assay using only polyclonal reagents. Therefore it was possible to add a small quantity of HBeAg for neutralising any anti-HBe present in a test serum without affecting HBeAg detection. This small amount of serum HBeAg was incorporated into each test sample thus allowing the determination of the e status of a patient using only one aliquot of test serum. This single test assay could be performed either as a radioimmunoassay or as an ELISA. The sensitivity of these assays was found to be greater than the conventional polyclonal assay particularly with regard to sera containing anti-HBe.

Detailed immunologic analysis of the structural polypeptides of rubella virus using monoclonal antibodies

A panel of murine monoclonal antibodies prepared against rubella virus is described. Fourteen of these monoclonal antibodies react with the E1 glycoprotein of rubella virus and define a total of six spacially separate epitopes in competitive inhibition assays. Antibodies binding to epitopes E1(a), E1(b), E1(c), or E1(e) inhibit the hemagglutinin function of the virus, while antibodies binding to epitopes E1(d) or E1(f) do not. Monoclonal antibodies binding to epitopes E1(c) or E1(d) prevent virus infectivity and identify antigen in distinct intracytoplasmic vacuoles of rubella virus-infected Vero cells by indirect immunofluorescence. Monoclonal antibody to epitope E1(f) localizes antigen primarily to the plasma membrane of infected cells, while antibodies binding to epitopes E1(a), E1(b), or E1(e) localize antigen throughout the infected cell's cytoplasm. A single monoclonal antibody is described which only reacts with the mature form of the virion E2 glycoprotein after rubella virus is treated with a disulfide-bond reducing agent. This antibody immunoprecipitates a 43,000 MW precursor to the E2 glycoprotein from lysates of infected cells and localizes its antigen throughout the cytoplasm of infected cells. The five remaining monoclonal antibodies react with the rubella virus C polypeptide. They define four topographically separate epitopes on the C polypeptide, C(a), C(b), C(c), and C(d), each of which is diffusely distributed throughout the cytoplasm of rubella virus-infected cells.

Clinical validation of an antibody-capture anti-rubella IgM-ELISA

An antibody-capture IgM-ELISA using monoclonal antibodies for conjugate was subjected to clinical validation with respect to sensitivity and specificity. In 103 serum specimens, known to contain anti-rubella IgM by a sucrose density gradient method, IgM was found by the ELISA in 99 sera. In a second study, 16 out of 17 acute rubella infections were detected by the IgM-ELISA. In 17 out of 17 vaccinees, a specific IgM response could be demonstrated. Specificity of the antibody-capture ELISA was found to be high; no interference was seen in 60 rheumatoid-factor positive sera, in 100 highly positive IgG sera or 10 sera with anti-CMV IgM. Only one out of 100 sera with heterophile antibodies showed a positive response. In acute rubella infections, IgM was shown to be detectable from 1 to 4 days after onset of illness up to about 12 wk, with peak values at about 1 wk after onset.

Monoclonal antibodies directed to E1 glycoprotein of rubella virus

We have prepared four monoclonal antibodies to rubella virus E1 glycoprotein. Three nonoverlapping antigenic sites were delineated on E1 protein by competitive binding assays. Antibodies binding to one site were characterized by high hemagglutination inhibition (HI) titer but poor neutralizing activity. The addition of antiglobulin conferred neutralizing activity. Antibodies directed to two other antigenic sites had modest hemolysis inhibition but little or no HI and neutralizing activities. The addition of antiglobulin markedly augmented HI activity but had little effect on neutralizing activity. Epitopes defined by three antibodies were conserved among four rubella virus strains examined.

Comparison of five different methods of rubella IgM antibody testing

Five tests for the detection of rubella specific IgM antibody were compared. They were the conventional method of sucrose density gradient fractionation, followed by haemagglutination inhibition; an anti-mu capture radioimmunoassay; and three commercially available enzyme linked assays: Rubazyme M, Rubenz M I, and its successor, Rubenz M II. The five methods detected similar numbers of rubella positive samples between seven and 35 days after the onset of symptoms; in the earlier stages, however, the radioimmunoassay and Rubenz M II were more sensitive. All three commercial kits were straightforward to use but produced misleading positive results with sera containing heterophil antibody. In considering sensitivity, specificity, and cost effectiveness together the Rubenz M tests were the most appropriate for routine use. With the recent withdrawal of Rubenz M I from the market only Rubenz M II is now available. If Epstein-Barr virus infection is excluded, Rubenz M II provides a reliable test for the diagnostic laboratory.

Prenatal detection of rubella-specific IgM in fetal sera

Serum specimens were obtained by fetoscopy at 19-25 weeks' gestation from four fetuses whose mothers had had confirmed rubella earlier in pregnancy. They were tested for rubella-specific IgM by antibody capture radioimmunoassay. No specific IgM was detected in one fetus and a healthy infant was delivered at term. Specific IgM was detected in the other three fetuses. In one case the level was low (1 unit) and this pregnancy went to term resulting in a neonate with clinical and laboratory evidence of congenital rubella infection. The remaining two fetuses had 2.8 and 2.4 units of specific IgM and the pregnancies were terminated. Blood obtained from these two fetuses after abortion showed levels of 5.4 and 2.9 units respectively. No specific IgM was detected in sera from eleven other fetuses aborted because of maternal rubella but five of these cases were terminated before 19 weeks and in five the interval between rash and abortion was three weeks or less. The results show that the human fetus can produce detectable specific IgM antibody by 19-20 weeks' gestation after exposure to rubella several weeks earlier. However, a larger study is required to define the reliability of fetoscopic blood sampling for the diagnosis of intrauterine infection.

Monoclonal antibodies against microorganisms

The recent spread of hybridoma technology among laboratories has promoted the development of monoclonal antibodies against a wide variety of infectious disease agents. While monoclonal antibodies theoretically represent an excellent (perhaps superior) alternative to conventional antisera as diagnostic, therapeutic or laboratory reagents, traditional antisera may be preferable to monoclonal antibody in some circumstances because of the fixed affinity and specificity as well as the limited functional capacities of some antibodies. The acceptance of monoclonal antibodies by the clinical microbiologist and physician must await proof of their reliability, safety and efficacy.

An outbreak of erythema infectiosum associated with human parvovirus infection

Erythema infectiosum (EI) or fifth disease is a mild, acute exanthematous disease, occurring mainly among children, for which a causative virus has long been sought. In May 1983 an outbreak of exanthematous illness was reported in a primary school in North London. Children attending the school were investigated by questionnaire and 162 (43.9%) reported an illness with the features of EI. In each of 36 cases investigated virologically the illness was associated with parvovirus infection. Moreover, pre-existing antibody to parvovirus was correlated with protection from EI in 16 of 17 close family contacts of cases. We propose therefore that EI is the common manifestation of infection with the human parvovirus.

The immunoglobulin M response to rubella vaccine in young adult women

Rubella vaccination histories were taken from 333 young women working in the head office of a retail organization: 29% said they had had vaccine and 47% said they had not. The remainder did not know. Forty-six per cent of those less than or equal to 25 years old (who should have been offered vaccine at school), and 6% of those greater than 25 years old, said they had been vaccinated. When screened for immunity to rubella by radial haemolysis (RH) 3% had a low level of antibody (less than 15 i.u./ml) and 11% had no antibody. After immunization with Cendevax the specific rubella IgM response was measured by an IgM antibody capture radioimmunassay (MACRIA). It was only detectable in the group without RH antibody, and was present in 26/31 of them. The IgM response to Cendevax was strongest in specimens taken 20-39 days after immunization, but in 10 out of 11 cases tested was still present at around 71 days. The specific IgM responses to Cendevax were very similar to those in women given Almevax in an earlier study, when measured in parallel tests. Taking both vaccines together, specific IgM was present in 35 out of 36 vaccinees without pre-existing antibody tested between 40 and 77 days post-immunization. Detection of specific IgM by MACRIA would therefore be an effective means of determining susceptibility retrospectively in rubella vaccinees found to be pregnant.

Evaluation of a commercial antibody capture enzyme immunoassay for the detection of rubella specific IgM

A commercial M antibody capture ELISA kit ( Rubenz M) for the detection of rubella specific IgM was evaluated in comparison with M antibody capture radioimmunoassay. A total of 248 sera were evaluated, including sera from cases of primary postnatal rubella, congenital rubella, infectious mononucleosis, and sera which contained rheumatoid factor. No false positive results were obtained but two high positive sera gave Rubenz M values which were below the value recommended as indicative of a positive result. We therefore propose changes in the criteria used for assessing the significance of the results obtained. These changes improve the accuracy of the assay without loss of specificity.

A comparison of Rubazyme-M and MACRIA for the detection of rubella-specific IgM

One-hundred and eighty-six carefully selected sera were tested for rubella-specific IgM by Rubazyme-M (Abbott Diagnostics) and an M-antibody capture radioimmunoassay (MACRIA). Eleven of these sera were from cases of infectious mononucleosis, six of which gave positive results in MACRIA, while one gave a positive result in Rubazyme-M. Of the remaining 175 sera, 158 gave concordant results whilst 17 sera gave discordant results; these 17 were also tested by serum fractionation. Problems were encountered with all assay systems used. It is therefore recommended that the results of all tests for rubella-specific IgM should be interpreted with caution.

Diagnostic assays with monoclonal antibodies for the human serum parvovirus-like virus (SPLV)

Monoclonal antibodies to the serum parvovirus-like virus (SPLV) were prepared by the hybridoma technique. They provided an antibody reagent which was used to develop solid phase antibody-capture assays for anti-SPLV IgM and IgG and for SPLV antigen. These assays were more sensitive than those based on human convalescent antibody as a reagent, and were more economical in the use of SPLV antigen. Their use enabled the serological responses to SPLV to be studied more fully and their sensitivity revealed the extent of SPLV infection. SPLV antigen was detected in four patients by both counter-immuno electrophoresis (CIE) and radioimmunoassay (RIA) and in two others by RIA alone. Parvovirus particles were seen in all six by electron microscopy. The anti-SPLV IgM response was measured in patients infected by SPLV. It was strong 5-18 days after the onset of illness, then declined and was only detectable in trace amounts after 6 months. Anti-SPLV IgG was also formed early, and persisted for at least 6 months. In a survey of 310 blood donors anti-SPLV was detected in 134 (43%) by CIE, but in 190 (61%) by IgG antibody capture RIA.

Rubella-specific IgM reactivity in sera from cases of infectious mononucleosis

Eight sera from 125 cases of infectious mononucleosis (IM) were reactive for rubella-specific IgM in an M-antibody capture radioimmunoassay. The reactivity of individual sera varied depending upon the source of the rubella antigen used in the assay. One serum gave strongly positive results with some rubella haemagglutinating antigens but negative results with others and may have contained an IgM antibody which was capable of distinguishing between strains of rubella virus. If the diagnosis of rubella is based solely on detection in solid-phase immunoassay of rubella-specific IgM, IM should be excluded.

Antibody capture radioimmunoassay (MACRIA) for coxsackievirus B4 and B5-specific IgM

An antibody capture radioimmunoassay was established for the detection of coxsackievirus B4 and B5-specific IgM. A significant feature of the assay was the use of an unrefined coxsackievirus B (CBV) antigen. The antigen was prepared by freeze thawing, ultrasonication and low speed centrifugation of infected Vero cells with no purification or concentration of the antigen being performed. Results of sera tested were expressed as a serum ratio (SR) by comparison with a low positive control serum. To establish an SR indicating positivity in the assays, 100 antenatal sera collected in late February were tested. The mean SR was calculated and the mean plus three standard deviations was taken as the minimum SR indicating positivity. Although resulting in a relatively insensitive assay, such a value was required to exclude sera giving a low level of reactivity which may be due to residual enterovirus-specific IgM resulting from a remote infection.The homologous CBV-IgM assay was positive in four cases of CBV4 infection and six cases of CBV5 infection. For the CBV4 IgM assay, ten of 20 (50%) sera from infections with CBV other than CBV4 were positive and nine of the 13 (69%) sera from infections with echoviruses or coxsackieviruses A were positive. Five of 18 (27%) sera with an elevated CBV neutralization titre were positive in the CBV4-IgM assay. For the CB5-IgM assay seven of 18 (39%) sera from infections with CBV other than CBV5 were positive and nine of 13 (69%) sera from infections with echoviruses or coxsackieviruses A were positive. The nine sera that were positive from this group in the CBV5-IgM assay were the same nine as were positive in the CBV4-IgM assay. Two of the 18 (11%) sera with an elevated CBV neutralization titre were positive in the CBV5-IgM assay. These two sera were also positive in the CBV4-IgM assay and had an elevated monotypic CBV4 neutralization titre. None of the sera giving positive results gave significant reactivity when tested with control antigen. Twelve rheumatoid factor containing sera and 46 sera from other infections were negative in both assays. Of 24 sera from confirmed CBV infection, seven gave a positive monotypic CBV4 or 5-IgM response, ten were positive in both assays and seven were negative in both assays. The positive results seen with sera from cases of heterologous enterovirus infection may result from an anamnestic IgM response or, more likely, IgM directed against enterovirus cross-reacting antigens. The absence of homologous neutralizing antibody at a dilution of 1:20 in nine of 20 sera that gave a positive CBV-IgM result and the presence of positive results for CBV4 and 5-IgM in a 14 month old infant who had echovirus 7 infection indicates that the IgM need not be directed against neutralizing antigens.Thus the CBV4 and 5-IgM assays developed appeared to be specific for an enterovirus infection but because of the cross-reactivity were not type-specific or group-specific.

Production of monoclonal antibodies to hepatitis B surface and core antigens, and use in the detection of viral antigens in liver biopsies

Hybridomas secreting monoclonal antibodies to HBsAg and HBcAg were prepared from immunized mice. An antibody capture radioimmunoassay was used to detect and select appropriate hybrids for propagation and cloning. The advantages of this assay were discussed. The resulting monoclonal antibodies were compared with conventional polyclonal antisera for the detection of virus antigens in liver tissue and found to give excellent results.

Screening for anti-rubella IgM ad libitum

There are few applications of virology to clinical medicine that have received more attention than the laboratory diagnosis of rubella. Many laboratories attempt it and most readers of this journal will be familiar with the techniques that have been used. It would therefore be superfluous to review the ‘state of the artm’ had there not recently been an innovation that is likely to alter laboratory practice in this field.

The use of monoclonal antibodies in virology

Antibodies have been used for the last five decades in the laboratory diagnosis of a wide range of diseases caused by viruses and in detailed investigations of virus structure. However, immunological and serological assays have always had problems of interpretation, reproducibility and standardization, resulting partly from the unavoidable heterogeneity of the antibodies in the test. When a mouse, for example, is immunized with a virus, the animal may easily recognise 10–20 different antigenic determinants. As many as five distinct antibodies can be produced by the mouse against each determinant and these will often differ from antibodies made by another mouse against the same antigenic determinant. The method of lymphocyte fusion and the subsequent generation of monoclonal antibodies (Kohler & Milstein, 1975; Kohler, 1980) overcomes these limitations.