Modified staphylococcal absorption method used for detecting rubella-specific immunoglobin M antibodies during a rubella epidemic

Removal of nonspecific hemagglutination inhibitors, immunoglobulin G, and immunoglobulin A with streptococcal cells and its application to the rubella hemagglutination inhibition test

A streptococcus, AW 43 strain, was found to bind nonspecific serum inhibitors of rubella virus hemagglutination (HA). This was demonstrated by titration of nonspecific HA inhibitors and by immunoelectrophoresis. Absorption of sera with the mixture of AW 43 cells, which bind IgA in addition to nonspecific HA inhibitors, and AR 1 cells, another strain of streptococci which bind IgG, removed nonspecific HA inhibitors, IgG, and IgA simultaneously, leaving behind IgM and a trace of IgA. Pretreatment of sera with those streptococcal cells prior to the rubella hemagglutination inhibition (HI) test enabled to circumvent kaolin treatment of sera, which partially removes IgM antibodies, and to determine exclusively the early-appearing antibodies. The rise and fall of the HI antibodies thus determined correlated well with that of the IgM antibodies determined by enzyme-linked immunosorbent assay (ELISA). Thus, this modified rubella HI test may be useful for serodiagnosis of recent rubella virus infection.

Detection of early hemagglutination inhibitory antibodies to rubella virus by pretreatment of sera with streptococcal cells

A technique that is based on absorption of sera with streptococcal cells and hemagglutination inhibition (HI) was evaluated for its feasibility for serologic diagnosis of recent rubella. The mixture of AR1 and AW43 cells removes IgG and IgA from the kaolin-treated sera, leaving IgM and a trace of IgA, probably oligomeric IgA. Consequently, after the absorption with streptococci, the HI antibodies are detectable exclusively in the early sera of patients with rubella. The streptococci (AR1 and AW43) have several advantages as the absorbent over the staphylococcus (Cowan I) that has been used routinely.

Therapeutic abortions following rubella infection in pregnancy: the potential impact on the incidence of congenital rubella syndrome

In 1977, a large rubella outbreak occurred in Hawaii. Because attack rates were high among women of childbearing age, we conducted extensive surveillance efforts to detect both pregnancies complicated by rubella and cases of congenital rubella syndrome (CRS). Initial surveillance included a survey of physicians and hospitals, review of fetal death and birth certificates, and cord blood screening for rubella-specific IgM of infants born following the epidemic. Two years after the outbreak, the medical community was again surveyed to identify affected children who were missed initially. No case of CRS was identified either shortly after the outbreak or in the ensuing two years. In addition, none of the 5,605 cord serum samples obtained was found to contain rubella-specific IgM antibody. Through active surveillance, we received 12 reports of rubella in pregnant women, of whom 11 elected to terminate their pregnancies. The extensive use of therapeutic abortion by exposed women may have prevented the birth of infants with CRS. Surveillance for rubella-related abortions is an important component in assessing the health impact of rubella in a community.

Enzyme immunoassays for measurement of cytomegalovirus immunoglobulin M antibody

The diagnosis of congenital cytomegalovirus (CMV) infection is often accomplished by the detection of circulating antibody directed against CMV. We devised a method for measuring CMV-specific immunoglobulin M (IgM) based on the isolation of IgM antibody by reaction with a solid phase coated with antihuman IgM. The determination of IgM antibody specific for CMV was accomplished by the subsequent addition of CMV or control antigen and enzyme-labeled CMV antibody (solid phase-IgM method). We compared the sensitivity and specificity of this method with those of a conventional form of solid-phase enzyme immunoassay in which CMV antigen is bound to the solid phase (solid phase-antigen method). Both assay systems were capable of detecting CMV-specific IgM antibody in the sera of 10 babies with documented CMV infection and in those of the mothers of 4 of these babies. The solid phase-IgM method yielded negative results in all 66 sera available from babies who did not have congenital CMV infection. On the other hand, the solid phase-antigen system yielded false-positive results in 12 (18%) of these sera. In addition, the solid phase-antigen system yielded false-positive results in 8 of 12 sera obtained from patients with demonstrable rheumatoid factor. However, the solid phase-IgM system yielded negative results for the rheumatoid sera, provided that appropriate control reactions were performed. The solid phase-IgM system is thus a specific and sensitive method for the determination of CMV IgM antibody.

A modified absorption-reduction method to detect virus-specific hemagglutination inhibiting and neutralizing IgM antibodies

IgG antibodies are preferentially absorbed by protein A-coupled sepharose beads while most of the IgM and IgA antibodies remain in solution. Even relatively low amounts of virus-specific IgM antibodies can then be detected unequivocally by a decrease of the antibody titer following the treatment with reducing agents. Ethandithiol proved superior to 2-mercaptoethanol in combination with neutralization assays.

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

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

Reverse enzyme immunoassay for detection of specific anti-Toxoplasma immunoglobulin M antibodies

A reverse enzyme immunoassay (R-EIA) is described, in which polystyrene muplates are sensitized with anti-immunoglobulin M (IgM) (mu chain) antibodies and then sequentially allowed to react with patient's serum, peroxidase-labeled Toxoplasma gondii soluble antigen, and substrate. Measurement of activity of the solid-phase bound enzyme conjugate was done by colorimetric reading of the final developed color and kinetically by the initial rate of color development. This R-EIA allowed full resolution between absorbance values of a group of 36 sera which presented positive results in the Toxoplasma IgM immunofluorescence test and the remaining groups, which consisted of 39 normal individuals, 22 rheumatoid factor-positive sera, 8 Waldenstrom's macroglobulinemic sera, 3 infectious mononucleosis samples, and 6 high-titered IgG anti-T. gondii sera. No interference of rheumatoid factor IgM or inhibition by high-titered specific IgG was detected, even in the false IgM immunofluorescence-positive rheumatoid factor samples. Likewise, false-negative IgM immunofluorescence samples gave positive R-EIA even without adsorption with Staphylococcus aureus protein A. The possibility of direct tagging of the antigen with the enzyme eliminates the need for using antigen and anti-antigen conjugates as separate layers, therefore eliminating one step in the assay.

Staphylococcal protein A adsorption of neonatal serum to facilitate early diagnosis of congenital infection

The early diagnosis of congenital infection frequently depends on the ability to distinguish between infant IgM and maternal IgG antibodies. Staphylococcal protein A, which specifically binds IgG, removed maternal IgG from the serum of newborn infants. Residual IgM antibodies to CMV, rubella, toxoplasmosis, and syphilis were then identified by routine serologic techniques. Persistence of greater than or equal to 25% of the original antibody titer following SPA adsorption distinguished the sera of infants with congenital infection from those of healthy infants. No false negative results were encountered. Specificity of the serologic results of SPA-treated infant sera correlated with IgM-specific identification of the causative agent. Potentially false positive titers were identified by concurrent elevation of IgA or rheumatoid factor. Adsorption of cord or neonatal serum with SPA facilitates accurate serologic diagnosis of congenital infection.

Further evaluation of a rubella passive hemagglutination test

Clinical experience with the Rubacell passive hemagglutination (PHA) test over a one-year period has shown the test to be a rapid, reliable, and economical method for determining antibody to rubella. The data from two separately administered rubella proficiency surveys showed 100% correlation between the PHA and the hemagglutination inhibition (HI) qualitative results with 24 reference specimens. Also, the PHA titers appeared to be generally higher than the HI in these specimens and in the sera of immune individuals. The efficacy of detecting HI antibody in the absence of PHA antibody as an indication of recent infection was compared to the HI paired sera method and to a rubella-specific immunoglobulin M (IgM) test based on protein A absorption. From the results obtained with the sera of 76 rubella patients, the efficacy of the three diagnostic methods was of the following order: protein A IgM test greater than positive HI/negative PHA greater than HI paired sera method.

A modified passive-haemagglutination technique for the detection of cytomegalovirus and herpes simplex virus antibodies: application in virus-specific IgM diagnosis

Cytomegalovirus (CMV) and herpes simplex virus (HSV) antibodies were detected by a modified passive haemagglutination (PHA) technique. The main features of this modification are the use of a simpler method for the removal of nonspecific sheep agglutinins in the sera, the deployment of commercially available CMV and HSV antigens, and a different sucrose density gradient (SDG) system for the separation of IgM from IgG. The modified procedure proved to be a reliable, specific, and sensitive technique in detecting antibodies to CMV and HSV in both whole serum and in the separated IgM and IgG fractions. It was as reliable as the complement-fixation (CF) test when applied in seroepidemiological studies and in the detection of antibodies in cord serum. Preliminary data are provided which suggest that the combination of SDG and PHA may prove to be a more reliable system for the detection of exclusion of CMV-specific IgM than an enzyme-linked immunosorbent assay (ELISA).

Specific absorption of human serum albumin, immunoglobulin A, and immunoglobulin G with selected strains of group A and G streptococci

Five gram-positive bacterial strains were selected for absorption studies of human serum samples. Strain AR1 (group A, M-type 1) and G148 (group G), with strong immunoglobulin G (IgG) binding capacities, and strain AW43 (group A, M-type 60), binding both IgA1 and IgA2, were compared with Staphylococcus aureus Cowan I and with Staphylococcus epidermidis L603. Both AR1 and G148 were capable of completely absorbing out serum IgG. In contrast, S. aureus Cowan I left a fraction unabsorbed, as expected from its known lack of IgG3 binding. Strain AW43 absorbed out all serum IgA, using a 10-microliter bacterial pellet for 20 microliter of serum. Serum IgM levels were slightly reduced by S. aureus Cowan I absorption. On the basis of the experiments, a bacterial mixture was designed consisting of S. aureus Cowan I and group A streptococcus strains AR1 and AW43, with absorption characteristics suitable for use in discriminating between early IgM and late IgG and IgA immune responses in routine serological work. A new type of bacteria-mammalian protein binding was discovered. Human serum albumin was completely absorbed out by strain G148 and to a lesser extent by strain AR1 and AW43. S. aureus Cowan I and S. epidermidis were negative. The binding capacity of G148 for albumin equalled that of Cowan I for IgG. The binding pattern of albumin to the strains was different from those of IgG, IgA, IgM, fibrinogen, haptoglobin, or aggregated beta 2-microglobulin and therefore seems to represent another type of bacterial-mammalian interaction with a specific albumin receptor on the surface of streptococci.

IgM fluorescence antibodies in sera of pregnant women exposed to rubella

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

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

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

A new principle for the detection of specific IgM antibodies applied in an ELISA for hepatitis A

A new test principle for the detection of specific IgM-class antibodies was developed and applied in an Enzyme-Linked Immuno Sorbent Assay (ELISA) for the detection of hepatitis A IgM antibodies. A solid phase coated with anti-IgM was incubated successively with serum sample, specific antigen, and enzyme-labeled F (ab')2 fragments from IgG antibodies against the antigen and enzyme substrate. F(ab')2 fragments were used to avoid interference with rheumatoid factor. Specificity and sensitivity are very high. This test principle appears generally applicable in the diagnosis of infectious and parasitic diseases by testing only one serum sample.

Oligomeric immunoglobulin A antibody response to rubella virus infection

Pooled sera from rubella patients in the early convalescent stage, containing a high titer of hemagglutination-inhibiting (HI) antibody, were treated with protein A-conjugated gel to reduce immunoglobulin G (IgG) antibody and then centrifuged in sucrose gradients. This treatment resulted in the detection of an HI activity peak sedimenting at a rate intermediate between 7S and 19S. In contrast to the 19S antibody, the HI activity of this peak was not abolished by 2-mercaptoethanol, but sedimented at 7S after this treatment. The activity was considered to consist of IgA oligomers, since it was removed by anti-IgA immunosorbent. The appearance of the oligomeric IgA antibody after the infection was then studied using serum samples collected sequentially from five rubella patients. Shortly after the onset of the disease, the HI activity appeared at high titer and thereafter gradually decreased in titer until it could no longer be detected in the sera. The time of its disappearance varied with each patient.