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PubMed1976

[A study of the avidity of Vi antibodies in typhoid fever patients and chronic carriers].

Avidity of Vi-antibodies was studied in the patients suffering from typhoid fever and chronic carriers in the indirect hemagglutination test (IHAT) by means of titration with erythrocytic diagnostic agents sensitized with various doses of the Vi-antigen. The minimal sensitizing dose still adequate for detection of the antibodies in the titre of 1 : 20 was accepted as the avidity index. By the avidity sign the antibody heterogeneity index was calculated as the ratio of the optimal sensitizing dose to the minimal sensitizing one. In comparison with the patients suffering from typhoid fever of at the acute period of the disease in chronic carriers Vi-antibodies were more avid, this being conditioned chiefly by the highly avid IgG-antibodies. During the acute period of the disease the avidity of Vi-antibodies elevated only against the antibodies of the IgG-class. An increase of heterogeneity by the same sign was noted with increase of the degree of the serum antibody avidity.

Antibodies, Bacterial↗
PubMed1985

Susceptibility of cytotoxic T lymphocyte (CTL) clones to inhibition by anti-T3 and anti-T4 (but not anti-LFA-1) monoclonal antibodies varies with the "avidity" of CTL-target interaction.

To explore the role of the T3, T4, and LFA-1 molecules in high and low "avidity" interactions between SB2-specific cytotoxic T lymphocyte (CTL) clones and their targets, monoclonal antibody-mediated inhibition of cytotoxicity has been studied in experiments that vary the "avidity" of interaction in three different ways. 1) Previous results have been extended with respect to different CTL clones assayed on the same SB2-positive target cells. Differences between clones in susceptibility to anti-T3 inhibition paralleled variations in anti-T4 inhibition, and both correlated inversely with the "avidity" of the effector-target interaction (inferred previously from studies of conjugate dissociation). 2) A high "avidity" clone, 8.4, was identified that lysed not only SB2-positive cells but also cross-reacted on a few SB2-negative cells. Cold target inhibition studies confirmed the cross-reaction, and together with conjugate dissociation studies, indicated that cross-reaction to be of lower "avidity" than the specific recognition of SB2. Cross-reactive lysis was much more susceptible to inhibition by anti-T3 and anti-T4 than was specific lysis. 3) Anti-T3 and anti-T4 blocking was analyzed in the presence of anti-Ia antibody to reduce the amount of Ia antigen available on the target. Anti-T3 and anti-T4 antibody blocking was more efficient after the addition of anti-Ia antibody concentrations that (by themselves) produced minimal inhibition of lysis. As a control, anti-LFA-1 antibody blocking was analyzed in each of these three experimental systems that compare interactions of different "avidity"; minimal variation was observed in the efficiency of inhibition by anti-LFA-1. Thus, anti-T3 and anti-T4 inhibition correlates inversely with the "avidity" of that CTL-target interaction, but anti-LFA-1 inhibition does not.

Adult↗
PubMed1978

Avidity of anti-native DNA antibody and glomerular immune complex localization in lupus nephritis.

Ten patients with clinically active SLE and biopsy-proven renal involvement were studied. Antigen binding capacity (ABC) and avidity of anti-nDNA antibodies were measured, using 125I-nDNA, by the ammonium sulfate test of Minden and Farr. The glomerular localization of immune complexes was determined by morphological studies. Mean avidity in 7 patients with mesangial and subendothelial deposits was 0.387 +/- 0.022 (mean +/- SE), and in those with additional subepithelial deposits was 0.247 +/- 0.036 (P less than 0.01). When measured serially, the avidity was found to alter slowly either during treatment or spontaneously. Follow-up histology in 2 cases showed morphologic transitions; in one the transition from the initial mesangial proliferative type to the membranous form was associated with a shift of the avidity from a high level to a low one. There was no significant relation between the avidity and ABC (r = 0.235, P greater than 0.1), suggesting that avidity and the quantitative ABC of antibodies in immune complexes may not necessarily behave in parallel. Thus, the avidity measurement is useful in understanding the immunological events which underlie various clinicopathological features of SLE.

Adult↗
PubMed1983

Influence of antibody avidity on glomerular immune complex localization.

Immune-complex-mediated glomerulonephritis (IC-GN) was induced with daily intraperitoneal injections of horse apoferritin (HAF) for varying intervals in Swiss albino and BALB/c mice. Anti-HAF antibody avidity in plasma pools from mice with predominantly mesangial immune deposits was compared with avidity in plasma pools from mice with predominantly capillary wall deposits. Plasma from Swiss mice having predominantly mesangial deposits after 7 or 14 days of HAF had higher avidities than plasma from Swiss mice with predominantly capillary wall deposits after 14 days or more than 28 days of HAF. Plasma from BALB/c mice with exclusively mesangial deposits after 7 days of HAF had higher avidity than plasma from BALB/c mice with predominantly capillary wall deposits after 14 or more days of HAF. Therefore, there was a correlation between glomerular site of immune deposition and avidity of circulating anti-HAF antibodies, with higher avidity antibodies associated with mesangial immune deposits and lower avidity antibodies with capillary wall deposits.

Animals↗
PubMed1982

Avidity of antibodies to dsDNA: comparison of IFT on Crithidia luciliae, Farr assay, and PEG assay.

The Farr assay is thought to detect only antibodies to DNA of relative high avidity. This is due to the high salt concentration of the employed ammonium sulfate precipitation, which dissociates DNA-anti-DNA complexes of low avidity. A recently introduced method to detect anti-DNA, the PEG assay, circumvents these dissociating reaction conditions by using polyethylene glycol instead of ammonium sulfate to precipitate the complexes; we therefore thought to measure antibodies to DNA of low avidity as well. We tested this assumption in several ways. It was found that the PEG assay detects a population of antibodies to DNA that are missed by the Farr assay. Complexes made with these antibodies were salt labile and could readily be dissociated by means of excess DNA, whereas Farr-positive antibodies formed stable complexes with DNA. Avidity studies using the method described by Celada et al. indicated that the anti-DNA detected by the PEG assay but missed by the Farr assay was of relatively low avidity. An inverse correlation between avidity and slope of the binding curves in the PEG assay was observed. These results confirm the notion that the PEG assay detects antibodies to DNA of low avidity. The fact that the Farr assay does not measure these antibodies confers possible diagnostic importance upon the PEG assay.

Antibody Affinity↗
PubMed1994

Differential avidity and cyclosporine sensitivity of committed donor-specific graft-infiltrating cytotoxic T cells and their precursors. Relevance for clinical cardiac graft rejection.

We have used limiting dilution analysis to study the qualitative and quantitative differences between graft-infiltrating cytotoxic T cell populations propagated from endomyocardial biopsies of heart transplant patients who experienced one or more acute rejection episodes and patients who never showed signs of rejection. Limiting dilution cultures were stimulated with autologous or donor cells both in the absence or in presence of cyclosporine and of CD8 in the cytotoxic phase. Almost all antigen-primed, committed cytotoxic T cells (cCTL) present in the graft of patients with rejections were CsA resistant. In contrast, in most patients of the nonrejector group, a substantial part of the cCTL could be inhibited by CsA. The CTL precursors (pCTL) in both groups were predominantly CsA sensitive. Addition of CD8 mAb during the cytotoxicity phase of the limiting dilution analysis was used to differentiate between CTL populations with high avidity for donor antigens and populations with low avidity. The predominant subpopulation in the graft of rejectors was a CsA-resistant cCTL with high avidity, while in the graft of most nonrejectors, cCTL with low avidity dominated. In most rejectors, CD8 mAb had only a minor influence on the pCTL frequency estimates, and thus on T cells with high avidity. CsA-sensitive pCTL with high avidity might represent an intermediate stage between the naive pCTL and mature, functional, CsA-insensitive cCTL with high avidity for donor antigens.

Antibodies, Monoclonal↗
PubMed1997

Avidity determination of IgG directed against tick-borne encephalitis virus improves detection of current infections.

Recently, avidity determination of IgG has been introduced successfully into virus serology as an additional and specific means for confirmation or exclusion of current infections. This simple and highly reproducible method can compensate for problems arising by classical serology, which include lack of detectable IgM responses during primary infections and persistent IgM responses after past infections. We show that avidity determination can be applied successfully for serological diagnosis of TBEV infection. Using the urea denaturation method, primary TBEV infections showed anti-TBEV IgG of low avidity (avidity index < 0.4), whereas sera from individuals with past infections exhibited high avidity IgG. The retrospective analysis of cases with clinical symptoms of TBEV infection in the absence of detectable anti-TBEV IgM showed that a significant number of these cases (5/45) had anti-TBEV IgG of low avidity, indicating current infection. We recommended the use of avidity determination as a method for routine TBEV serology.

Adult↗
PubMed1999

Isolation of high avidity melanoma-reactive CTL from heterogeneous populations using peptide-MHC tetramers.

Immunogenic peptides of human tumor Ag have been used to generate antigen-specific CTL. However, the vast majority of these peptide-specific CTL clones are of low avidity and are peptide, but not tumor, reactive. Peptide-MHC tetramers have been shown to bind specific TCRs with sufficient affinity to be useful reagents for flow cytometry. In this paper we demonstrate that peptide-MHC tetramers can also be used to selectively identify high avidity tumor-reactive CTL and enrich, from a heterogeneous population, the subpopulation of peptide-reactive T cells that can lyse tumor targets. The melanoma proteins, MART-1 and gp100, were used to induce potentially tumor-reactive T cells, and the intensity of T cell staining by TCR binding of specific peptide-MHC tetramers was assessed. A range of fluorescence intensity was detected, and the magnitude of tetramer binding was correlated with T cell avidity. The population of peptide-reactive T cells was phenotypically similar with regard to expression of TCR and adhesion molecules, suggesting that this differential avidity for tumor cells reflected differential affinity of the TCR for its peptide-MHC ligand. Sorting, cloning, and expansion of tetramerhigh CTL from a heterogeneous population of peptide-stimulated PBMCs enabled rapid selection of high avidity tumor-reactive CTL clones, which retained their functional and tetramerhigh phenotype on re-expansion. These results demonstrate that the avidity of a T cell for its tumor target is due to the specific affinity of the TCR for its peptide-MHC ligand, that this interaction can be described using peptide-MHC tetramers and used to isolate high avidity tumor-reactive CTL.

Antigen-Presenting Cells↗
PubMed1997

Enzyme-linked immunosorbent assay-IgG antibody avidity test for single sample serologic evaluation of measles vaccines.

A measles-specific enzyme-linked immunosorbent assay (ELISA)-IgG avidity test for serologic evaluation of the efficacy of measles vaccines with only one blood sample was evaluated after vaccination with three measles vaccine strains. Avidity indices were determined by the urea elution technique in samples presenting antibody titers > or = 100 mIU/ml. All 127 sera collected 2-8 weeks after primary vaccination with Biken-CAM70 measles vaccine had low avidity indices (LAI, when < or = 29%) with a time-dependent increase in avidity. In samples collected 6-10 weeks after vaccination with Edmonston-Zagreb, LAI were also observed in all 31 sera tested (mean = 15%) and in 233/242 (96.3%) filter paper samples from primary vaccination with Schwarz vaccine (mean = 14%). There was no difference in the mean avidity among the three groups of primary vaccinees, although the Schwarz group had higher antibody titers. In contrast, only 1/36 (2.8%) serum samples from children who were seropositive at the time of measles vaccination had LAI (mean = 56%), despite the fact that they were collected early (2-5 weeks after vaccination). Of 90 serum samples from children vaccinated in the past with two doses and of 42 cord blood serum samples, none had LAI. It is concluded that this test is a good tool for evaluating serologically the efficacy of a single dose schedule of measles vaccine. With only one postvaccination sample, the test can discriminate nonresponders (antibody titers below 100 mIU/ml), primary responders (antibody titers > or = 100 mIu/ml with LAI), and those previously immunized (antibody titers > or = 100 mIU/ml with high avidity indices). The seroconversion rate can be calculated after excluding the latter.

Adult↗
PubMed1996

High-avidity anti-DNA antibody removal from the serum of systemic lupus erythematosus patients by adsorption using dextran sulfate cellulose columns.

The purpose of this study is to determine whether immunoadsorption treatment using a dextran sulfate (DS) column can remove high-avidity anti-double-stranded DNA (anti-dsDNA) antibody from the blood of patients with systemic lupus erythematosus (SLE). Before and after each immunoadsorption therapy routine, titers of the high-avidity anti-dsDNA antibody of 11 SLE patients were measured by using a newly developed assay kit to exclusively detect high avidity anti-DNA antibody. Patients with active SLE showed significantly higher titers of high-avidity antibody than did those with inactive SLE, and their titers were significantly reduced by immunoadsorption procedures. Removal of high-avidity antibodies in vitro was also confirmed by mixing patients' sera and DS gel. Immunoadsorption therapy using DS columns is effective in the removal of high-avidity anti-dsDNA antibodies that are closely associated with pathogenicity in SLE.

Adult↗
PubMed2000

Tracing and characterization of the low-avidity self-specific T cell repertoire.

It is well established that expression of self antigens results in the deletion of the functional high-avidity self-specific T cell repertoire. Due to the low frequency of naturally occurring low-avidity self-specific T cells, a detailed evaluation of their ability to survive and differentiate into effector and memory populations in vivo has yet to be obtained. We here employ tetramer technology to characterize and determine the in vivo fate of a self-specific CD8(+) T cell population specific for a ubiquitously expressed T cell epitope. We find that in influenza nucleoprotein (NP)-transgenic mice (B10NP mice) an oligoclonal population of NP(366 - 374)-specific T cells can be triggered by live influenza virus exposure. The main hallmark of this self-specific T cell population is its diminished avidity for the tetrameric MHC / NP peptide complex. These low-avidity T cells are not deleted and do not down-regulate their antigen or CD8 receptors, and exhibit cytolytic activity towards tumor cells expressing NP endogenously. Strikingly, a secondary influenza infection generates a typical memory response in the low-avidity repertoire. The observation that low-avidity T cells persist in vivo and can differentiate into memory T cells underscores their potential role in anti-tumor immunity.

Animals↗
PubMed2002

Generation of adult-like antibody avidity profiles after early-life immunization with protein vaccines.

The capacity to induce high-avidity antibodies following early-life immunization has long been questioned, and the possibility of inducing such antibodies soon after birth is a recognized goal for a number of vaccination strategies. Therefore, we assessed the capacity to develop high-avidity antibodies to peptidic vaccines in 1-week-old BALB/c mice. The dynamics of the generation of antibody molecules of increasing avidity were analyzed on circulating serum antibodies and, where feasible, at the single-cell level on spleen and bone marrow antibody-secreting cells. Two alum-adsorbed protein-based human vaccines, tetanus toxoid (TT) and pertussis toxin, induced neonatal antibody responses with adult-like avidity profiles. This was confirmed at the level of spleen and bone marrow ASC. In contrast, immunization with TT-P30, a 21-mer synthetic peptide containing a TT-immunodominant epitope, trinitrophenyl hapten (TNP) conjugated to ovalbumin or TNP conjugated to Ficoll, induced a much lower avidity profile in early life than in adults. These observations indicate that in murine models the avidity maturation of T cell-dependent antibody responses induced by structurally complex protein vaccines can be fully elicited after early life immunization, as opposed to the maturation of responses induced with short peptides or hapten-based vaccines.

Aging↗
PubMed1981

Avidity indices of anti-IgG antibodies in diseases.

Anti-IgG antibodies were detected in 69% of 235 sera tested. A simple and reproducible method was developed to measure the avidity index of anti-IgG antibodies. It was found that subjects with systemic lupus erythematosus and progressive systemic sclerosis and normal controls had antibodies with lower avidity index than those with rheumatoid arthritis and Down's syndrome. The difference in avidity seems to be disease specific. Avidity does not correlate with antibody titers, but all sera with high avidity antibody are positive in the latex test. The anti-IgG as measured by this method was shown to be mainly of IgM class. The avidity indices of whole sera and purified IgM fractions were similar.

Antibodies, Anti-Idiotypic↗
PubMed1993

IgG antibodies to human herpesvirus-6 in young children: changes in avidity of antibody correlate with time after infection.

Sera from 321 children aged 0-179 weeks and 196 adult blood donors were examined for IgG antibodies to human herpesvirus-6 (HHV-6) using an indirect immunofluorescence test. After birth, antibody prevalence declined to a minimum between 20 and 29 weeks. Thereafter the percentage of individuals with antibody increased up to the age of 60-69 weeks after which the prevalence of antibody in the children remained stable at about 88%; in contrast, the seroprevalence in blood donors was 98%, indicating that some individuals remain susceptible to infection after early childhood but that virtually all are infected by the time they reach adulthood. The HHV-6 antibody titre increased steadily over the first 70 weeks of life and then remained stable up to 179 weeks old at a level significantly higher than that of the adults. Two hundred and eighteen of the 321 sera whose HHV-6 antibody titres were 40 or greater were tested for antibody avidity using a modification of the immunofluorescence test whereby low avidity antibody was eluted with urea. The results show that the age distribution of low avidity antibody closely parallels the known distribution of exanthem subitum and, moreover, that the mean antibody avidity increased with time after primary infection. The method was further validated because well-characterised convalescent sera taken from seven children within 3 weeks of exanthem subitum all contained low avidity antibodies. The data presented in this study indicate that low avidity IgG to HHV-6 may be detected after primary infection and that this should prove useful in diagnosis and for seroepidemiological surveys.

Adult↗
PubMed1994

Varicella-zoster virus antibody avidity and IgG-subclass patterns in children with recurrent chickenpox.

The normal immune response after primary varicella-zoster virus (VZV) infection includes IgG subclass evolution to predominantly IgG1-type antibodies, and maturation from low to high avidity antibodies which are maintained for life. Twenty-three healthy and apparently immunocompetent children with a history of 2-5 episodes of chickenpox were studied after repeat disease. Serial sera were tested for VZV-IgG subclass patterns and VZV IgG and G-subclass antibody avidity by urea elution enzyme linked immunoassay (ELISA). Of 11 patients studied within 8 weeks of repeat chickenpox (Early Group), mean antibody avidity was significantly lower (31.3 +/- 26.81) than control (65.1 +/- 12.38) (P < .001). Seven had low avidity antibody (< 30 percent) and an abundance of IgG3 which was a pattern like primary chickenpox, and 2/11 had high avidity antibody characteristic of anamnestic responses. Early Group patients and 12 others studied over 8 weeks after repeat disease (Late Group) showed avidity maturation and attrition of IgG subclass antibodies other than IgG1. At least nine children failed to show VZV-specific secondary (memory) immune responses early in the course of repeat disease. It is possible that failure to maintain or evoke a secondary immune response could explain their susceptibility to repeat chickenpox.

Adolescent↗
PubMed1988

Dissociation studies of DNA/anti-DNA complexes in relation to anti-DNA avidity.

Antibodies to dsDNA differ in their avidity towards the antigen. The electrostatic interaction between DNA and anti-DNA is sensitive to increases in pH and/or ionic strength and therefore, elution studies employing either of these permit discrimination between anti-dsDNA populations that differ in avidity. Another way to determine anti-dsDNA avidity is the calculation of Farr/PEG ratios. These are obtained by division of the amount of anti-DNA measured with the Farr assay (which does not detect low avidity anti-dsDNA) by the amount measured with the PEG assay (which does detect low avidity anti-dsDNA). With these separate approaches, we compared the sera of 17 SLE patients with nephritis with the sera of 17 patients with central nervous system (CNS) involvement. Farr/PEG ratios and sensitivity to high pH elution of anti-dsDNA in the sera of these patients both permitted discrimination between the two groups of patients. The anti-dsDNA of patients with nephritis was found to have a significantly higher avidity towards DNA than anti-dsDNA of patients with cerebral disease. We also observed a significant correlation between Farr/PEG ratios and the salt lability of anti-dsDNA.

Antibodies, Antinuclear↗
PubMed1994

Solid-phase antigen density and avidity of antibodies detected in anti-group B streptococcal type III IgG enzyme immunoassays.

Two enzyme immunoassays which measure anti-group B streptococcal type III capsular carbohydrate IgG antibodies were compared. One utilised poly-L-lysine conjugated coating antigen while the other used tyraminated coating antigen. Both carbohydrate antigens appeared to be antigenically identical but the poly-L-lysine based assay gave significantly lower values for some sera. Sera were identified which had low and high avidity anti-group B streptococcal type III IgG antibodies by the thiocyanate elution method. These antibodies gave results on a dilution range of coating concentrations consistent with their relative avidity. Comparison of dilution ranges of the two conjugates used for coating suggests that the poly-L-lysine conjugate coats with a ten-fold lower efficiency than the tyramine conjugate and therefore detects only higher avidity antibodies. Four fractions containing different relative avidities of affinity-purified IgG were produced from a single serum. These fractions behaved in the same manner as sera containing antibodies of different avidities. The results of this study suggest that the method of polysaccharide conjugation in enzyme immunoassays may affect the antigen concentration on the solid phase and thence the detection of antibodies of various avidities.

Antibodies, Bacterial↗
PubMed1989

Estimation of the avidity of antibodies in polyclonal antisera against Streptococcus pneumoniae type 3 by inhibition ELISA.

The reliability of the determination of antibody avidity in polyclonal sera by indirect sandwich ELISA was studied. Binding of IgM and IgG (sub)classes in unpurified serum to Streptococcus pneumoniae type 3 capsular polysaccharide, which was coated onto ELISA plates, was inhibited with different inhibitors. The inhibitor concn at which 50% inhibition of antibody binding to the ELISA coat was achieved, was used as a measure for antibody avidity. As this 50% inhibition value is dependent upon the dilution of the serum and thus upon the initial amount of free antibody, it is necessary to define (a narrow range of) final ELISA absorbance values to which the dilutions of non-inhibited sera have to be adjusted. The shapes of the serum dilution curves have a good correlation with the numerical 50% inhibition values of the antibody avidity. The inhibition ELISA is suitable to compare the avidity values of the different antibody isotypes, but two remarks should be made: (1) antibody heterogeneity should be considered to influence the results and prevent the accurate measurement of absolute numerical avidity values. Because in the ELISA system merely antibody "activity" is measured, comparison of the efficacy of vaccines by means of the 50% inhibition (avidity) value of various antibody (sub)classes can still be performed in a reliable way; (2) results of the determination of the 50% inhibition values of the different antibody (sub)classes showed them to be dependent on the molecular ratio between antibody (sub)class levels. More aspects of the determination should be taken into account, like shapes of simple dilution curves, influences of various inhibitor concns in the diluent and whole (extended) inhibition curves.

Animals↗