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PubMedDate not supplied

Rubella-specific IgG1 avidity: a comparison of methods.

Two methods of determining the avidity of specific IgG1 were compared with sera from different categories of rubella infection. Both methods were based on an antiglobulin enzyme-linked immunosorbent assay. In one method the absorbances were compared with and without diethylamine (DEA) in the serum diluent over a range of serum dilutions and the difference between the dilution curves measured (DEA-shift). In the other, the absorbances at a single serum dilution were compared with and without urea in the wash fluid used after the antigen/serum incubation (avidity index). Various concentrations of DEA were also assessed in the avidity-index method, as this method is simpler to perform. The DEA-shift method was shown to be more sensitive for diagnosing recent primary rubella or immunization by demonstrating specific IgG1 of low avidity. The avidity-index method, however, was more specific when sera from cases of reinfection or non-specific rubella IgM reactivity were tested. 35 mM DEA was found to be the optimal concentration of DEA when DEA was substituted for urea in the avidity index method.

Antibodies, Bacterial↗
PubMed1995

Application of fluoroimmunoassay to the identification of low avidity specific IgG against pathogenic human viruses and Toxoplasma gondii.

BACKGROUND: Serological diagnosis of primary viral infections is usually made by detection of specific IgM. In some cases, false positive results (mainly due to crossreactions between closely related viruses) can be obtained. Moreover, some primary infections occur without specific IgM response. Thus, alternative serological approaches are required for diagnosis. Detection of low avidity, specific IgG has been applied as a useful serological marker for diagnosing infections caused by several viruses and Toxoplasma gondii. OBJECTIVE: The standardization and application of specific IgG avidity assays using a semiautomated solid phase immunoassay (fluoroimmunoassay (FIA)) on the basis of the urea elution principle, for the characterization of low avidity specific IgG against rubella virus, herpes simplex virus (HSV), varicella-zoster virus (VZV), cytomegalovirus (CMV) and T. gondii. STUDY DESIGN: The method consists of two simultaneous determinations, one as recommended by the manufacturer and the other including a washing step with 8 M urea after the antigen-antibody reaction. A reduction in titer higher than, or equal to, 50% was considered indicative for presence of low avidity specific IgG. RESULTS: When applied to the diagnosis of infections, this method showed sensitivity ranging from 81% to 100%, and absolute specificity. The detection of low avidity specific IgG allowed the differentiation between primary and recurrent infections caused by VZV. Furthermore, it helped in the identification of CMV as the etiological agent of congenital infection in the absence of specific IgM response, as well as in the elucidation of crossreactivity between antigenically related viruses, i.e., VZV and HSV, and Epstein-Barr virus and CMV. CONCLUSION: FIA can be used for the characterization of the avidity of specific IgG antibody as a diagnostic test in clinical laboratories.

Journal Article↗
PubMed2005

A comparison of the AVID and DAVID trials of implantable defibrillators.

We compared 2 studies of implantable cardiac defibrillators (ICDs) to determine the effects of device mode on outcomes. The Antiarrhythmics Versus Implantable Defibrillators (AVID) trial (1993 to 1997) demonstrated improved survival with the ICD compared with antiarrhythmic drug therapy. The Dual-chamber And VVI Implantable Defibrillator (DAVID) trial (2000 to 2002) showed that VVI pacing at 40 beats/min in patients with ICDs reduced the combined end point of death and hospitalization for congestive heart failure compared with DDDR pacing at 70 beats/min. Patients in the AVID trial (631 of 1,016) and the DAVID trial (221 of 506) meeting common inclusion and all exclusion criteria were studied. The major end points were the time to death, and the composite end point of time to death or hospitalization for congestive heart failure. Patients in the AVID and DAVID trials were similar, but more AVID patients had coronary artery disease (p = 0.04), history of myocardial infarction (p = 0.005), and previous ventricular arrhythmias (p = 0.03). DAVID patients underwent more previous revascularization procedures (coronary artery bypass surgery, p = 0.03; percutaneous coronary intervention, p = 0.001), and were more often taking beta-blocking drugs at hospital discharge (p <0.001). The backup VVI ICD groups in both studies had similar outcomes (p = 0.4), even when corrected for the previous demographic differences. The time-to- composite end point was similar in AVID patients treated with antiarrhythmic drugs and DAVID patients treated with DDDR ICDs (p = 0.6). Despite improved pharmacologic therapy and revascularization, outcomes have not improved with backup VVI pacing ICDs. If DDDR ICDs had been used in the AVID trial, benefit from ICDs for patients with serious ventricular arrhythmias could have been missed.

Adrenergic beta-Antagonists↗
PubMed2005

Anti-myeloperoxidase IgG subclass distribution and avidity in sera from patients with propylthiouracil-induced antineutrophil cytoplasmic antibodies associated vasculitis.

OBJECTIVE: Propylthiouracil (PTU) could induce MPO-ANCA-positive vasculitis. The aim of this study was to compare the IgG subclass distribution and avidity of MPO-ANCA in sera from patients with primary ANCA-associated vasculitis (AASV) and PTU-induced vasculitis. METHODS: Nineteen patients with primary AASV with MPO-ANCA and thirteen patients with PTU-induced vasculitis were enrolled in the current study. Sera in both active phase and remission were collected. Anti-MPO IgG subclasses were detected by antigen specific ELISAs using specific monoclonal antibodies as second antibodies, and MPO-ANCA avidity was assessed by antigen-inhibition ELISAs. RESULTS: In primary AASV, all four anti-MPO IgG subclasses could be detected in active phase with IgG1 (100%), IgG2 (73.7%), IgG3 (63.2%) and IgG4 (94.7%), and in remission, IgG1 and IgG4 subclasses in most patients remained positive. However, in PTU-induced vasculitis, anti-MPO IgG3 subclass could not be detected, the anti-MPO IgG subclasses in active phase were IgG1 (100%), IgG2 (61.5%) and IgG4 (46.2%). Furthermore, five out of the six patients (88.8%) with PTU-induced vasculitis with positive IgG4 subclass in active phase turned to negative in remission, however, only eight out of the fourteen patients (57.1%) with primary AASV turned to negative. The median avidity constant of MPO-ANCA was 56 (8.96 to >140) x 10(7) mol/l for patients with primary AASV and 0.7 (<0.28 to >140) x 10(7) mol/l for patients with PTU-induced vasculitis respectively. Furthermore, the relative levels of MPO-ANCA avidity were associated with elevation of ESR in primary AASV and were associated with BVAS scores in patients with PTU-induced vasculitis, respectively. CONCLUSION: MPO-ANCA IgG subclass distribution and avidity were different between patients with primary AASV and PTU-induced vasculitis. It was suggested that the mechanism of ANCA production in PTU-induced vasculitis was different from that in primary AASV, and the avidity of MPO-ANCA might be associated with disease activity.

Adult↗
PubMed2006

New Vidas assay for Toxoplasma-specific IgG avidity: evaluation on 603 sera.

After the development of the new version of the test Vidas Toxo IgG with antigens obtained from tachyzoites cultured on cells, a Vidas avidity test has been recently developed. The aim of this study was to assess the value of the determination of avidity on the new Vidas test. This avidity test was performed on 553 sera obtained from pregnant women whose dates of infection had been determined and on 50 sera obtained from immunosuppressed patients. In the group of infection occurring less than 4 months before sampling, the avidity index was <0.3 on 266 among 267 sera. In the group of infection occurring more than 15 months before sampling, the avidity index was >0.3 for 44/46 sera of pregnant women and for 47/47 sera of immunosuppressed patients. Thus, the new version of avidity test was helpful primarily to rule out that an infection had occurred within the prior 4 months.

Animals↗
PubMed2006

High avidity binding of engineered papaya mosaic virus virus-like particles to resting spores of Plasmodiophora brassicae.

Papaya mosaic virus (PapMV) like particles (VLPs) were used as a platform for fusion of affinity peptides binding to resting spores of Plasmodiophora brassicae-a major pathogen of crucifers. Three peptides with specific affinity to the target were isolated and cloned at the C-terminus of the PapMV coat protein (CP), generating three different high avidity VLPs. The peptides were exposed at the surface of the VLPs and their avidity to resting spores of P. brassicae was measured by flow cytometry. NLP-A, with the peptide DPAPRPR, showed the highest avidity. The binding avidity of NLP-A to P. brassicae spores was comparable to that of a polyclonal antibody. NLP-A was also shown to be more specific than the antibody. Fusion of the affinity peptide to a monomeric form (mCP) of the CP [Lecours, K., Tremblay, M.-H., Laliberté Gagné, M.-E., Gagné, S.M., Leclerc, D., 2006. Purification and biochemical characterization of a monomeric form of papaya mosaic potexvirus coat protein. Protein Express. Purific. 47, 273-280] generated a fusion protein that was unable to assemble into VLPs, and mCP-A fusions failed to bind resting spores. The avidity of VLP-A was increased by adding a glycine spacer between the C-terminus of the PapMV CP and the peptide, and improved even further by using a duplicated A peptide in the fusion protein. The use of high avidity VLPs has advantages over polyclonal antibodies because of target specificity. VLPs offers the specificity of monoclonal antibodies but can be more easily generated using the powerful selection of phage display.

Animals↗
PubMed2004

PorA-specific differences in antibody avidity after vaccination with a hexavalent Men B outer membrane vesicle vaccine in toddlers and school children.

A clinical phase II trial with an experimental hexavalent outer membrane vesicle (OMV) vaccine (HexaMen) containing six different porin A (PorAs) was carried out in toddlers (2-3 years) and schoolchildren (7-8 years) in The Netherlands. HexaMen exists of two OMVs each containing three different PorA types. The serum bactericidal activity (SBA) after vaccination against the six PorAs was significantly different and was higher in toddlers than in schoolchildren. After vaccination the SBA against P1.5-2,10 was 4-6 times higher than against P1.7-2,4. The aim of this study was to test whether the differences in SBA could be explained by a difference in subtype-specific antibody avidity maturation. The avidity index (AI) of antibodies against three subtypes (PorA types P1.5-2,10; P1.12-1,13 and P1.7-2,4) was measured by ELISA and evaluated in relation to SBA. A significant avidity maturation for the 3 PorA subtypes was found. This maturation was most pronounced for P1.5-2,10 (mean AI = 72%), correlating with the highest SBA titres. Generally, the avidity titre correlated best with SBA. No differences in avidity indices against the three tested PorAs were found between toddlers and school children indicating that avidity maturation induced by this vaccine is not age-dependent.

Antibodies, Bacterial↗
PubMed2006

Neospora caninum IgG avidity tests: an interlaboratory comparison.

Avidity tests can be used to discriminate between cattle that are acutely and chronically infected with the intracellular parasite Neospora caninum. The aim of this study was to compare the IgG avidity ELISA tests being used in four European laboratories. A coded panel of 200 bovine sera from well documented naturally and experimentally N. caninum infected animals were analysed at the participating laboratories by their respective assay systems and laboratory protocols. Comparing the numeric test results, the concordance correlation coefficients were between 0.479 and 0.776. The laboratories categorize the avidity results into the classes "low" and "high" which are considered indicative of recent and chronic infection, respectively. Three laboratories also use an "intermediate" class. When the categorized data were analysed by Kappa statistics there was moderate to substantial agreements between the laboratories. There was an overall better agreement for dichotomized results than when an intermediate class was also used. Taken together, this first ring test for N. caninum IgG avidity assays showed a moderate agreement between the assays used by the different laboratories to estimate the IgG avidity. Our experience suggests that avidity tests are sometimes less robust than conventional ELISAs. Therefore, it is essential that they are carefully standardised and their performance continuously evaluated.

Acute Disease↗
PubMedDate not supplied

Antibody subclass profile and avidity during acute and chronic human Schistosoma mansoni infection.

The avidity of IgA, IgM, IgG and IgG subclass antibodies against Schistosoma mansoni soluble egg antigen (SEA) was determined by ELISA in serum samples collected in 1995 from individuals in Brazil with acute (n = 36) and chronic (n = 40) schistosomiasis. Fifteen individuals at the acute phase were also evaluated 6 months after clinical diagnosis. Predominance of low-avidity IgG, IgG1, IgG2, IgG3 and IgA characterized the acute phase. IgG4 was detected in only 2 individuals with acute disease (5.6%). Levels of anti-SEA IgM were similar between the study groups. IgG1 avidity showed the strongest association with the chronological evolution of the infection, presenting 100% of low avidity during the acute infection and reaching 100% of high avidity 6 months after. It is suggested that distinct anti-Schistosoma egg antigens subclass profile and antibody avidity characterize the clinical phases of S. mansoni infection. In particular, determination of anti-SEA IgG1 offers a new tool for the laboratory analysis of the disease.

Acute Disease↗
PubMed1998

A simple, rapid enzyme-linked immunosorbent assay for evaluating immunoglobin G antibody avidity in toxoplasmosis.

This article describes an enzyme-linked immunosorbent assay (ELISA) for evaluating the avidity of Toxoplasma-specific immunoglobin (Ig) G. The test was standardized with the Falcon assay screening test (F.A.S.T) ELISA system using 6 M urea in phosphate-buffered saline for dissociating low-avidity antibodies after the antigen-antibody interaction. The avidity indices for 25 serum samples from patients with a recent Toxoplasma infection ranged from 10 to 40% (mean index = 25.3%), whereas for sera from 25 subjects with preexisting Toxoplasma immunity, the indices ranged from 58 to 94% (mean index = 73.1%). In sequential serum samples obtained over a period of up to 15 months from three patients exhibiting a persistent IgM antibody response to T. gondii, the avidity indices gradually increased during the course of infection. Avidity indices compatible with a recent infection were found in serum samples taken during the first 3 months after the onset of toxoplasmic lymphadenopathy, whereas indices compatible with the presence of a long-term infection were found in serum samples taken 7 or more months after the onset of toxoplasmic lymphadenopathy. The simplicity and short assay time (less than 1 h) make the test a potentially useful tool in assessing the avidity of Toxoplasma-specific IgG.

Animals↗
PubMed1999

Contribution of serotype-specific IgG concentration, IgG subclasses and relative antibody avidity to opsonophagocytic activity against Streptococcus pneumoniae.

The contribution of serotype-specific IgG concentration, subclasses, and avidity to opsonophagocytic activity (OPA) against Streptococcus pneumoniae (Pnc) was evaluated in sera of adults and infants immunized with different pneumococcal vaccines. Antibody concentrations and avidities were measured by enzyme immunoassay (EIA) and OPAs by killing assay of Pnc. The most important factor contributing positively to OPA was the specific IgG level. In infants, a tendency to negative correlation was found between the concentration needed for killing of bacteria and avidity, suggesting that less antibodies of high rather than low avidity were required for killing. No such correlation was seen in adults. However, in adults the avidity was high already before vaccination and the variation was narrow. Thus, avidity was probably not a limiting factor influencing OPA. The effect of IgG2/IgG1 ratio on OPA was mostly negative but insignificant.

Adult↗
PubMed1997

Antibody response of Echinococcus granulosus infected mice: protoscolex specific response during infection is associated with decreasing specific IgG1/IgG3 ratio as well as decreasing avidity.

The antibody response was followed during 68 weeks in 17 Balb/c mice intraperitoneally (i.p.) infected with Echinococcus granulosus protoscoleces (PSC) and in three mice i.p. immunized with dead PSC. Titres of antibodies recognizing peptidic and glucidic PSC epitopes, as well as their isotypic and avidity profiles were followed by ELISA. In addition, antigen recognition patterns were analysed by immunoblot. The response against carbohydrate epitopes was dominant in infected and immunized mice but stronger in the first group. Infected mice showed similar profiles of specific IgG and IgM with maximum titres from week 38 to 53. Although IgG1 and IgG3 were the predominant antibody subclasses, the ratio of IgG1/IgG3 antibody titres as well as antibody avidity decreased during the experiment, encompassing a decrease in recognition of peptidic epitopes. Immunized mice did not show significant levels of specific IgM and, after week 15, showed IgG titres lower than the infected mice. IgG1 was the predominant IgG subclass during all the experiment with background levels of IgG3. The mean Ab avidity was high and showed no significant changes during immunization. Different patterns of response were thus produced by dead and developing live parasites. Although high avidity IgG1 antibodies were early found in both cases, lower avidity IgG3 antibodies were increasingly produced afterwards only in infected animals. The isotype switch and avidity decrease observed only during infection are consistent with a possible parasitic mechanism to evade host immunity.

Animals↗
PubMed1988

Old mice recover the ability to produce IgG and high-avidity antibody following irradiation with partial bone marrow shielding.

The splenic plaque-forming-cell (PFC) response to trinitrophenylated bovine gamma globulin of 18- to 20-month-old mice is markedly depressed, with a preferential loss of indirect (IgG) PFC and high-avidity-antibody-secreting cells compared to 6- to 8-week-old animals. The anti-trinitrophenyl response of old mice, whose peripheral lymphoid system has been reconstituted from their own bone marrow after irradiation while their bone marrow was partially shielded, includes high-avidity and IgG PFCs relatively comparable to those of normal young mice. If young mice are irradiated while their bone marrow is partially shielded and given purified splenic T cells from either old or young donors during recovery from irradiation, then the avidity distribution and the ratio of IgG/IgM PFCs they produce in response to trinitrophenylated bovine gamma globulin reflects the characteristic immune response of the T-cell donor. These results are consistent with the hypothesis that the bone marrows of old and young mice are similar with regard to the spectrum of B-cell clones that they can generate and that it is peripheral regulatory effectors that are responsible for much of the age-related change in the immune response. In addition, if one calculates the PFC avidity distribution taking into account those cells whose secretion of antibody was inhibited by anti-idiotype autoantibodies, then it is clear that there are more high-avidity B cells present in old mice than are detected by the conventional plaque-inhibition assay. Thus, the reduced avidity of the PFC response of old mice appears to be, at least in part, due to down regulation by anti-idiotype autoantibodies.

Aging↗
PubMed2006

Avidity of tetanus and Hib antibodies after childhood acute lymphoblastic leukaemia - implications for vaccination strategies.

AIM: To investigate the possible relationship between serum levels and avidities of antibodies against tetanus toxoid (TT) and Haemophilus influenzae type b (Hib) in children that were vaccinated after treatment for childhood acute lymphoblastic leukaemia (ALL). METHODS: The study groups were 31 paediatric patients with ALL and 18 healthy controls. All subjects were vaccinated with TT and a protein conjugated Hib vaccine. Antibody levels were analysed at three time points: At diagnosis of ALL, after cessation of treatment before vaccination and three weeks after vaccination. Avidity was measured twice, with a thiocyanate elution assay, at diagnosis of ALL and three weeks after vaccination. RESULTS: There was a correlation between level and avidity of tetanus antibodies after vaccination (r(s) = 0.59, P < 0.001). In the standard-risk and intermediate-risk ALL groups, all patients responded with protective levels of tetanus antibodies with normal avidity. In the high-risk ALL group 7/9 patients had subprotective levels of tetanus antibodies after vaccination and concomitantly the lowest avidity, implying poor protection against tetanus. No patients were found with low levels and low avidity of anti-Hib IgG, and 29/31 patients had full protection after a single dose of conjugated Hib-vaccine. CONCLUSION: The vaccination strategy after childhood ALL must be different for low-risk and high-risk ALL groups, since the high-risk group fail to elicit a recall response to tetanus.

Adolescent↗
PubMed2001

Effect of testing for IgG avidity in the diagnosis of Toxoplasma gondii infection in pregnant women: experience in a US reference laboratory.

The usefulness of testing for IgG avidity in association with Toxoplasma gondii was evaluated in a US reference laboratory. European investigators have reported that high-avidity IgG toxoplasma antibodies exclude acute infection in the preceding 3 months. In this US study, 125 serum samples taken from 125 pregnant women in the first trimester were chosen retrospectively, because either the IgM or differential agglutination (AC/HS) test in the Toxoplasma serologic profile suggested or was equivocal for a recently acquired infection. Of 93 (74.4%) serum samples with either positive or equivocal results in the IgM ELISA, 52 (55.9%) had high-avidity antibodies, which suggests that the infection probably was acquired before gestation. Of 87 (69.6%) serum samples with an acute or equivocal result in the AC/HS test, 35 (40.2%) had high-avidity antibodies. Forty women were given spiramycin, to prevent congenital transmission, and 7 (17.5%) had high-avidity antibodies. These findings highlight the value of testing a single serum sample obtained in the first trimester of pregnancy for IgG avidity.

Animals↗
PubMed1998

Antibody avidity as a surrogate marker of successful priming by Haemophilus influenzae type b conjugate vaccines following infant immunization.

Evaluation of the new generation of conjugate vaccines is hampered by the absence of reliable surrogate markers of immunologic memory. Memory responses are characterized by rapid production of relatively high-avidity antibody; thus, a solid-phase ELISA was adapted for the measurement of anti-Haemophilus influenzae type b (Hib) IgG avidity. In a cohort of infants vaccinated at 2, 3, and 4 months of age with Hib conjugate vaccines, avidity increased in the period following vaccination, while antibody titer fell. After a booster dose at 1 year of age, both antibody titer and avidity increased. In a cohort with anti-Hib IgG <1.0 microg/mL following primary immunization, antibody avidity after booster was low, indicating an absence of priming. Antibody avidity may help distinguish, in persons with low antibody titers, between those who are primed for memory and those who are not.

Antibodies, Bacterial↗
PubMed1998

C1.7 monoclonal antibody designates high-avidity CD4+ cytotoxic T lymphocytes involved in clinical heart rejection.

BACKGROUND: It is assumed that not all donor-specific cytotoxic T lymphocytes (CTLs), but only those with a high avidity for donor antigens, can function as terminal effector cells in transplant rejection. METHODS: In the present study, we searched for markers that would exclusively designate these high-avidity CTL. RESULTS: FACS analysis of donor-specific CTL clones obtained from heart transplant patients revealed that high- and low-avidity CTL varied in their expression of p38, a surface molecule involved in signal transduction, which is stained by the antibody C1.7. High- and low-avidity CD8+ CTL and high-avidity CD4+ CTL expressed p38, whereas low-avidity CD4+ CTL did not. Noncytotoxic and naive CD4+ lymphocytes also lacked p38 surface expression. CONCLUSION: Therefore, we conclude that p38 is a marker for CD4+ lymphocytes with the potency to damage the transplanted heart. Accordingly, p38 might be used to analyze the contribution of CD4+ CTL in immune responses, such as transplant rejection.

Antibodies, Monoclonal↗
PubMed1992

Avidity and titer of immunoglobulin G subclasses to Porphyromonas gingivalis in adult periodontitis patients.

The relative avidity and titer of antibodies representing the 4 immunoglobulin G (IgG) subclasses (IgG1-4) reactive with Porphyromonas gingivalis, P. gingivalis-lipopolysaccharide (-LPS), streptokinase (SK) and tetanus toxoid (TT) in the sera of patients having adult periodontitis and of healthy controls were measured. Patient antibody titers to P. gingivalis and P. gingivalis-LPS were found to be significantly elevated for IgG, IgG1 (no P. gingivalis-LPS antibodies) and IgG2. The predominant antibody response to P. gingivalis and P. gingivalis-LPS occurred in the IgG2 subclass. When the relative avidity of the antibodies to P. gingivalis and P. gingivalis-LPS were examined, no significant differences between control and patient sera could be identified. However, anti-P. gingivalis and P. gingivalis-LPS antibodies were found to possess significantly lower relative avidity than either SK or TT antibodies. The IgG1 subclass antibodies to P. gingivalis, SK and TT all appeared to be of high relative avidity. In contrast, anti-P. gingivalis and P. gingivalis-LPS of the IgG2 subclass were of significantly lower relative avidity. Since the predominant humoral response to P. gingivalis occurs in the IgG2 subclass, the low relative avidity of these antibodies predominates in measurements of whole serum activity.

Adult↗