Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “avidity”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources
PubMed2006

The hypervariable immunodominant NP418-426 epitope from the influenza A virus nucleoprotein is recognized by cytotoxic T lymphocytes with high functional avidity.

Recently it was shown that influenza A viruses can accumulate mutations in epitopes associated with escape from recognition by human virus-specific cytotoxic T lymphocytes (CTL). It is unclear what drives diversification of CTL epitopes and why certain epitopes are variable and others remain conserved. It has been shown that simian immunodeficiency virus-specific CTL that recognize their epitope with high functional avidity eliminate virus-infected cells efficiently and drive diversification of CTL epitopes. T-cell functional avidity is defined by the density of major histocompatibility complex class I peptide complexes required to activate specific CTL. We hypothesized that functional avidity of CTL contributes to epitope diversification and escape from CTL also for influenza viruses. To test this hypothesis, the functional avidity of polyclonal CTL populations specific for nine individual epitopes was determined. To this end, peripheral blood mononuclear cells from HLA-A- and -B-genotyped individuals were stimulated in vitro with influenza virus-infected cells to allow expansion of virus-specific CTL, which were used to determine the functional avidity of CTL specific for nine individual epitopes in enzyme-linked immunospot assays. We found that the functional avidity for the respective epitopes varied widely. Furthermore, the functional avidity of CTL specific for the hypervariable NP(418-426) epitope was significantly higher than that of CTL recognizing other epitopes (P < 0.01). It was speculated that the high functional avidity of NP(418-426)-specific CTL was responsible for the diversification of this influenza A virus CTL epitope.

Amino Acid Sequence↗
PubMed1998

Do IgA, IgE, and IgG avidity tests have any value in the diagnosis of toxoplasma infection in pregnancy?

AIM: To determine the value of tests for specific IgA, IgE, and IgG avidity in diagnosing Toxoplasma gondii infection during pregnancy. METHODS: In a retrospective study, current serological tests (dye test and three IgM assays with different sensitivities) were compared with immunosorbent agglutination assays (ISAGA) for specific IgA and IgE and an IgG avidity enzyme linked immunosorbent assay (ELISA). Patient group 1 comprised six women with definite or probable infection during pregnancy determined by congenital toxoplasmosis or laboratory results. Group 2 comprised seven women infected during or before 11 pregnancies (two consecutive pregnancies in two patients and three in a third). RESULTS: One patient in group 1 seroconverted during pregnancy. IgA ISAGA and avidity confirmed acute infection when confirmatory IgM ELISA remained negative. In five of six patients from group 1, IgA and IgE ISAGA and avidity confirmed acute infection. In group 2, the dye test titre was raised in seven of 11 pregnancies (six of seven patients). Specific IgM and IgA were positive during all 11 pregnancies. IgE ISAGA was positive in only four of 11 pregnancies (three of seven patients), but negative results in the remainder may exclude acute infection. High avidity antibodies indicative of past infection were found in four of 11 pregnancies (two of seven patients). CONCLUSIONS: Each test improved diagnosis or timing of infection but no single test was ideal. The IgA ISAGA was sensitive and detected seroconversion. Positive IgE ISAGA and low avidity both confirmed infection, whereas negative IgE may exclude acute infection. High avidity diagnosed past infection but persistence of low avidity reduced its value to differentiate acute and past infection. Further studies with larger patient groups are needed to determine the optimum diagnostic strategy. These techniques are valuable in complementing existing tests.

Animals↗
PubMed1999

Avidity of anti-P aeruginosa antibodies during chronic infection in patients with cystic fibrosis.

BACKGROUND: In order to study the impact on the lung function of patients with cystic fibrosis of the avidity of antipseudomonal antibodies, the avidity of antibodies against the chromosomal beta-lactamase of Pseudomonas aeruginosa (a beta ab) and against the 60-65 kDa heat shock protein of P aeruginosa (anti-GroEL) were measured in serum samples collected longitudinally during chronic infection with P aeruginosa from a group of patients with poor and good lung function. METHODS: The thiocyanate elution method in which the molarity of potassium thiocyanate required to elute 50% bound antibody under conditions of antigen excess in ELISA was used to measure the relative avidity. RESULTS: All patients developed increasing levels of a beta ab and anti-GroEL antibodies during the follow up period but no maturation of the avidity of these antibodies was observed. In patients with good lung function the avidity of a beta ab was higher than in patients with poor lung function (p = 0.018). No significant difference in the avidity of the anti-GroEL antibodies was observed between the two groups of patients. CONCLUSION: In patients with cystic fibrosis a high avidity of a beta ab could contribute to a more efficient inhibition of the beta-lactamase by these antibodies, resulting in the better lung function seen in this group. The immunopathological implication of the failure in avidity maturation of antibodies in chronic infection is discussed.

Antibodies, Bacterial↗
PubMed2003

Chronic myelogenous leukemia shapes host immunity by selective deletion of high-avidity leukemia-specific T cells.

We have shown that cytotoxic T lymphocytes specific for PR1, an HLA-A2-restricted nonopeptide derived from proteinase 3, kill leukemia cells and may contribute to the elimination of chronic myelogenous leukemia (CML) after treatment with IFN or allogeneic bone marrow transplant. Some patients with persistent disease also have circulating PR1-specific T cells, however, suggesting the likelihood of immune tolerance. Here we show that both high- and low-avidity PR1-specific T cells from the peripheral blood of healthy donors can be identified and selectively expanded in vitro. Although high-avidity PR1-specific T cells killed CML more effectively than low-avidity T cells, only high-avidity T cells underwent apoptosis when stimulated with high PR1 peptide concentration or when exposed to leukemia that overexpressed proteinase 3. No high-avidity PR1-specific T cells could be identified or expanded from newly diagnosed leukemia patients, whereas low-avidity T cells were readily expanded. Circulating high-avidity PR1-specific T cells were identified in IFN-sensitive patients in cytogenetic remission, however. These results provide evidence that CML shapes the host immune response and that leukemia outgrowth may result in part from leukemia-induced selective deletion of high-avidity PR1-specific T cells.

Apoptosis↗
PubMedDate not supplied

Use of thiocyanate elution to estimate relative avidity of allergen specific IgE antibodies.

Although several methods for estimating avidity of antigen-antibody reactions are available, most are impractical for the study of human IgE antibodies because of a requirement for pure allergen and antibody in relatively large amounts. To determine the relative avidity of specific IgE antibodies for Dermatophagoides pteronyssinus allergens, seven concentrations of the chaotropic thiocyanate ion were used to disrupt epitope-antibody binding in a specific IgE immunoassay system, using sera from 16 allergic patients with marked skin test reactivity to a standardized D. pteronyssinus extract. Relative avidity, the molarity of thiocyanate required to produce a 50% decrement in binding, ranged from 0.29-3.1. Within assay coefficient of variation (CV) was 9.9% and between assay CV was 13%. D. pteronyssinus specific IgE levels ranged from 0.66-141 kUa/L, not correlating with relative avidity (rho = -0.12). Thiocyanate elution appears to be a useful method for estimating relative avidity of specific IgE antibodies for the myriad epitopes of the allergenic proteins in an allergen extract. It could be used to study the immunochemistry of specific IgE assays; avidity maturation in allergen immunotherapy and in asymptomatic but sensitized patients; and preseasonal versus postseasonal changes in avidity within individuals. With a suitable solid phase, it could be modified to examine avidity at the epitope level.

Adolescent↗
PubMed1999

Avidity of islet cell autoantibodies in non-diabetic children and children with insulin-dependent diabetes.

Low-avidity immunoglobulin G antibodies, which commonly occur after microbial infections and form unstable complexes with the antigen, are within weeks replaced by high-avidity antibodies, which bind the antigen tightly and characterise mature immune response. We hypothesised that avidity of islet cell autoantibodies (ICA), found in the sera of patients with insulin-dependent diabetes mellitus (IDDM) usually months or years before disease onset, might reflect the stage of progression towards overt IDDM. ICA were quantitated before and after treatment of antigen-antibody complexes with 5 M urea in a new assay, in which the fluorescence intensity of europium chelate-labelled detecting antibody is measured from a digital time-resolved fluorescence image. The proportion of urea-resistant ICA of all ICA was defined as the avidity index. The median avidity indices (range) of 119 children with recent-onset IDDM and 64 non-diabetic ICA-positive children were 74% (23-100%) and 11% (0-100%), respectively (p = 0.0001). The avidity indices of only 3 children with IDDM (2.5%), but of 55 non-diabetic ICA-positive children (86%) were < 40%. In conclusion, our data show that ICA avidity indices of ICA-positive non-diabetic children and children with IDDM differ, suggesting that measurement of ICA avidity may improve prediction of the time of onset of clinical IDDM.

Adolescent↗
PubMed2003

High avidity CD8+ T cells are the initial population elicited following viral infection of the respiratory tract.

Following intranasal administration, the model paramyxovirus simian virus 5 (SV5) establishes an infection in the respiratory tract of mice, which is subsequently cleared by CD8+ T cells. In this study, we sought to understand the maturation of the antiviral immune response over time by assessing the functional avidity of the responding T cells and the expansion of immunodominant populations. Surprisingly, we determined that the initial response to Ag at day 3 (d3) in the mediastinal lymph node was exclusively high avidity. However, by d5 postinfection, low avidity cells were approximately 50% of the responding T cell population. Following secondary exposure to SV5, high avidity CD8+ T cells again are the exclusive cell type present at early times postinfection (d2). Similarly, high avidity cells were preferentially elicited at d3 following infection with the unrelated vaccinia virus. We also made the observation that the immunodominance profile has not been established at d3 postinfection with SV5. However, by d5 a clear immunodominance pattern arises and is permanently maintained. These data indicate that high avidity cells are the predominant population responding at early times postinfection following respiratory infection with SV5 or vaccinia virus. However, as the response progresses, low avidity cells are activated/expanded to a greater extent compared with high avidity cells.

Administration, Intranasal↗
PubMed2003

Selective induction of high avidity CTL by altering the balance of signals from APC.

High avidity CTL are most effective at clearing viruses and cancer cells. Therefore, understanding the mechanisms involved in induction of high avidity CTL is critical for effective vaccines. However, no vaccine approach to selectively induce high avidity CTL in vivo has been discovered. In a new approach, signals from MHC class I (signal 1) and costimulatory molecules (signal 2) were adjusted by varying Ag dose and by use of recombinant poxvirus expressing a triad of costimulatory molecules (B7-1, ICAM-1, and LFA-3), respectively. Independent of CTL avidity, a strong signal 1 resulted in an increased frequency of CD8(+) CTL. However, a strong signal 2 was necessary for the induction of high avidity CD8(+) CTL that killed target cells more efficiently, and signal 2 played a more crucial role in the absence of a strong signal 1. Only CTL induced with strong signal 2 killed tumor cells endogenously expressing low levels of Ag. Signal 2 contributed to the induction of high avidity CD8(+) CTL in both primary and secondary responses. Thus, although signal 2 has been known to increase the quantity of CTL response, in this study we show that it also improves the quality of CTL response. Our data also suggested that dendritic cells play an important role in induction of high avidity CD8(+) CTL in vivo. This strategy to selectively induce higher avidity CTL may lead to more effective vaccines for viruses and cancer.

3T3 Cells↗
PubMed2006

Gene transfer of tumor-reactive TCR confers both high avidity and tumor reactivity to nonreactive peripheral blood mononuclear cells and tumor-infiltrating lymphocytes.

Cell-based antitumor immunity is driven by CD8(+) cytotoxic T cells bearing TCR that recognize specific tumor-associated peptides bound to class I MHC molecules. Of several cellular proteins involved in T cell:target-cell interaction, the TCR determines specificity of binding; however, the relative amount of its contribution to cellular avidity remains unknown. To study the relationship between TCR affinity and cellular avidity, with the intent of identifying optimal TCR for gene therapy, we derived 24 MART-1:27-35 (MART-1) melanoma Ag-reactive tumor-infiltrating lymphocyte (TIL) clones from the tumors of five patients. These MART-1-reactive clones displayed a wide variety of cellular avidities. alpha and beta TCR genes were isolated from these clones, and TCR RNA was electroporated into the same non-MART-1-reactive allogeneic donor PBMC and TIL. TCR recipient cells gained the ability to recognize both MART-1 peptide and MART-1-expressing tumors in vitro, with avidities that closely corresponded to the original TCR clones (p = 0.018-0.0003). Clone DMF5, from a TIL infusion that mediated tumor regression clinically, showed the highest avidity against MART-1 expressing tumors in vitro, both endogenously in the TIL clone, and after RNA electroporation into donor T cells. Thus, we demonstrated that the TCR appeared to be the core determinant of MART-1 Ag-specific cellular avidity in these activated T cells and that nonreactive PBMC or TIL could be made tumor-reactive with a specific and predetermined avidity. We propose that inducing expression of this highly avid TCR in patient PBMC has the potential to induce tumor regression, as an "off-the-shelf" reagent for allogeneic melanoma patient gene therapy.

Animals↗
PubMedDate not supplied

[Antibody avidity: use for the diagnosis of HIV early infection].

Determination of IgG avidity is useful to distinguish primary infection from reactivation or reinfection in viral, parasitic or bacterial infections. For diagnosis of HIV type 1 primary infection, the detection of IgM antibodies is often useless since they are also found in chronic infection. The usual serology (Elisa, western-blot, p24 antigen) may present no interest if done too late (more than 2 or 3 months after infection). Therefore, we have developed a test to determine the avidity of anti-HIV1 antibodies, using 1 M guanidine as denaturing agent. We have adapted the measurement of avidity to the Axsym automatic system for a routine use. Indeed, since requests for avidity determinations are sporadic, the use of microplates is not convenient. Using this assay, we found a low avidity (less than 50%) in immunocompetent and recent infected patients (less than 6 months), compared to old infected patients (more than 12 months) who had high avidity (80 to 100%). However, early treated patients (in the 6 months after contamination) had also low avidities but with a slower development of antibody maturation (8 to 27 months versus 2 to 8 months in non treated patients). To conclude, the determination of the anti-HIV1 avidity, according to the proper procedures explained here (notion of treatment and/or serious immunodepression), may help the physician to date the infection in each new infected patient who might benefit from an early treatment.

Acquired Immunodeficiency Syndrome↗
PubMed2001

[Diagnosis of the early phase of larval toxocariasis using IgG avidity].

The term avidity used to express the strength of the bond between a serum specimen and a multivalent antigen. It is known that the avidity increases with time after antibody challenge and measurement of the avidity has been used diagnostically. Recently an assay measuring the IgG avidity of various virus infections and of toxoplasmosis was used to distinguish between acute and chronic infection. Our study was focused on the method to distinguish acute and chronic Toxocara infection, zoonosis caused by the larvae of dog and cat ascarids Toxocara canis and Toxocara cati known all over the world for the possibility of provoking the infestation of man, accompanied by visceral or ocular clinical manifestations. The infection is generally diagnosed by demonstration of specific immunoglobulins to Toxocara excretory-secretory antigens (TES) in sera of infected patients. Highly sensitive assays with specific antigens are necessary for detection of antibodies. The test that has been proved clinically useful is the ELISA reaction with TES antigens. This method detects the antibodies for months or even years after infection and this is the reason why the discrimination between chronic and recent infection is very difficult. For disrupting the hydrogen bond urea has been used. The index of avidity was calculated as the ratio of IgG values in sera treated with urea and the value of IgG in non-treated sera, multiplied by 100. An index up to 40 is considered as low avidity, that means freshly acquired infection (36 to 40 borderline) and more than 40 is high avidity. In the group of 1,376 patients only 5.09% low avidities were found. It means that predominantly patients in the chronic stage of infection attend examination.

Animals↗
PubMed2004

Performance of the immunoglobulin G avidity and enzyme immunoassay IgG/IgM screening tests for differentiation of the clinical spectrum of toxoplasmosis.

Toxoplasmosis has been well known as an important human infection to consider especially in pregnant women. Although many serologic methods are available, the diagnosis of toxoplasmosis can be extremely difficult. The presence of increased levels of Toxoplasma-specific IgG antibodies indicates an infection, but it does not differentiate between a recent and past infection. The purpose of our study was to compare the performance of the ELISA T. gondii IgG/IgM test, a widely used enzyme-linked immunosorbent assay, to the ELISA IgG avidity method. One hundred and four serum samples (from 38 males and 66 females) were tested and evaluated from symptomatic patients (chorioretinitis, lymphadenopathy), and from women in their first trimester of pregnancy who were suspected of having toxoplasmosis. The high IgG avidity and ELISA IgG antibody levels were in agreement for 51 of the specimens (49.0%). Thirty-eight discrepant (borderline) results from the IgG avidity method were positive for IgM (3 specimens) and IgG (37 specimens). Interestingly, out of the eight serum samples that were positive for both IgG and IgM antibodies, two samples were low IgG avidity, and three samples were borderline. There was no statistically significant relation observed between the results of the IgG avidity method and the ELISA IgG test, and the IgG avidity method and ELISA IgM test (chi2 = 1.987; p = 0.370 and chi2 = 2.152; p = 0.341, respectively). The IgG avidity method was considered easy to perform and an acceptable approach for the differentiation of discrepant results (recent/chronic) and for the current detection of T. gondii antibodies. We concluded that the determination of IgG avidity is a helpful tool for the diagnosis of the ocular form of toxoplasmosis and it is a safe method for screening this disease in the first trimester of pregnancy.

Animals↗
PubMed2004

Avidity IgG: diagnosis of primary Toxoplasma gondii infection by indirect immunofluorescent test.

In the present study, 18 serum samples from toxoplasmosis patients with different clinical manifestations were classified into G1: 9 patients with suspected of having recent T. gondii infection, and G2: 9 patients with suspected of having distant latent infection. Patients with low IgG avidity antibody, 80% of them were positive by IgG avidity-indirect immunofluorescent antibody test (IIFAT) and by IgM-ELISA for toxoplasmosis. However, 20% positive by low IgG avidity- IIFAT, were IgG-ELISA positive for toxoplasmosis. Patients with high IgG avidity antibody, 15.4 % of them were positive by high IgG avidity-IIFAT, and by IgM-ELISA, but 61.5% positive by high IgG avidity-IIFAT, were positive by IgG-ELISA and 23.1% positive by high IgG avidity IIFAT, were positive with both IgM and IgG ELISA. It was concluded that detection of high avidity IgG antibodies by IIFAT excluded recent T. gondii infection, as a confirmatory test and when only a single serum sample is submitted by the patient.

Adult↗
PubMed2005

[The importance and validity of anti-Toxoplasma gondii IgG, IgM, IgA antibodies and IgG avidity tests in the diagnosis of Toxoplasmosis infection during pregnancy.].

Detection of specific IgG, IgM and IgA antibodies by enzyme immunoassay (EIA) tests are not always sufficient in the diagnosis of early and late Toxoplasma gondii infection during pregnancy. For this reason, the specific IgG avidity test should be used to detect primary toxoplasmosis infection. In this study, an investigation was made of the serological status of pregnant women who were suspected of having primary or late toxoplasmosis as well as the importance and relationship of specific anti-Toxoplasma gondii IgG, IgM and IgA antibodies and specific IgG avidity in their sera. TORCH panels were also used for these patients. A total of 52 pregnant women who were admitted in the Dokuz Eylül University Gynecology and Obstetrics Clinic were included in this study. The sera were sent to the serology and immunology laboratory for investigation of the anti-Toxoplasma gondii IgG, IgM and IgA antibodies by the EIA (Cobas Core, Roche, Germany and ETI-TOXOK-A, DiaSorin, Germany) technique. The anti- Toxoplasma gondii IgG avidity test was performed on IgG as well as IgM and/or IgA in positive sera with the EIA (Toxoplasma IgG Avidity EIA Well- RADIM, Italia) technique. The anti-Toxoplasma gondii IgG avidity test was not performed on sera from 21 pregnant women negative for anti-Toxoplasma gondii IgG, IgM and IgA antibodies. Borderline and high IgM levels showed a good correlation with the IgG avidity results. The ratio for the IgM and IgA positivity was 32.3% and both the IgM positivity and IgA negativity were 29%. In conclusion, anti- Toxoplasma gondii IgG avidity and anti-Toxoplasma gondii IgM antibody tests should be used together. However, positivity or high avidity of IgA was limited in the diagnosis of active toxoplasmosis infection of pregnant women.

English Abstract↗
PubMed1991

The influence of avidity on signaling murine B lymphocytes with monoclonal anti-IgM antibodies. Effects of B cell proliferation versus growth inhibition (tolerance) of an immature B cell lymphoma.

We have investigated the effect of the avidity of a monoclonal anti-mouse IgM antibody (mAb) on its ability to activate normal B cells vs its capacity to inhibit the growth of an immature B lymphoma, BKS-2. A panel of seven mAb with specificities for four different domains of mu-heavy chain were selected and their relative avidities measured. Of the seven mAb studied, four antibodies (b7-6, Ak11, AK15, and DS1) were found to have relatively higher avidities than three others (AK17, 331.12, and Bet-2). Among them, the mAb b7-6 was highly efficient in inducing proliferation of normal B cells, whereas all others (including the remaining three high avidity mAb) were inefficient in inducing B cell proliferation. This failure cannot be simply related to the differences in their fine specificity because all the mAb became highly stimulatory after coupling to Sepharose beads. With one exception (DS1), avidity was a better predictor of the growth-stimulatory capacity when the antibodies were immobilized. Taken together, these findings suggested that although high affinity was important, there were other factors that might influence the mitogenic potential of a soluble anti-mu mAb. On the other hand, all anti-mu mAb irrespective of their avidity, fine specificity, and isotype were capable of effectively inhibiting the growth of BKS-2 cells. Furthermore, there was a direct correlation between the avidity and the dose of the mAb required to cause half-maximal inhibition of BKS-2 growth. The F(ab) fragments of high avidity mAb b7-6 failed to inhibit the growth of BKS-2 cells, which indicates that a minimal level of cross-linking of the membrane Ig receptor is necessary for causing growth inhibition in BKS-2 cells. Although there was no significant difference in the tolerogenic potential of soluble vs immobilized anti-mu mAb in directly inactivating BKS-2 cells, their growth-inhibitory capacity was remarkably different in the presence of rIL-5. Thus, rIL-5 was effective in partially overcoming the tolerogenic effect of soluble but not immobilized anti-mu mAb. Unlike IL-5, LPS rescued BKS-2 cells from the inhibitory effect of both soluble and immobilized anti-mu antibodies. Altogether, these results suggested that the ligand binding requisites for tolerance induction were less stringent than those for B cell activation. Furthermore, a high affinity interaction between membrane Ig receptor and its ligand appeared to generate a dominant negative signal that was not reversed by lymphokines.

Animals↗
PubMed1976

Role of t lymphocytes in the humoral immune response. II. T cell-mediated regulation of antibody avidity.

The effect of activated T lymphocytes (ATC) on the avidity distribution of PFC in the secondary response was studied in normal mice. The total PFC response was not significantly changed for either direct or indirect PFC by administration of ATC before secondary antigen challenge. However, marked suppression occurred of indirect PFC that secreted high avidity antibody; no suppression was seen of high avidity direct PFC. At the same time, significant stimulation was seen of relative and absolute frequencies of indirect PFC that secreted middle and low avidity antibody. These effects were dependent on Thy 1-bearing, nylon nonadherent cells which demonstrated carrier specificity. In further characterization of these effects, it was found that increasing the number of ATC transferred produced progressive loss of high avidity PFC and compensatory increase in lower avidity PFC. Moreover, in these experiments, suppression of the high avidity response was inducible with the administration of ATC 5 weeks before to 3 days after the secondary immunization. Thus, it is likely that the avidity-modifying effects are dependent on T lymphocytes which influence the late stages of B lymphocyte maturation.

Animals↗
PubMed1997

[Performance of the IgG avidity test in patients with cytomegalovirus disease].

BACKGROUND: IgG antibodies produced early in infection has a low avidity to their respective epitopes, so that an assay to detect those antibodies could be easily used to diagnose a recent primary infection. A prospective study of anti-CMV IgG avidity test in patients with microbiological evidence of active CMV infection was made. METHODS: One hundred thirty-five patients were studied. All patients sera were tested for CMV antibodies "pool" IgG/IgM, IgM and antibody IgG avidity index (AI). Furthermore, samples of blood leucocytes from immunosuppressed patients to detect CMV viremia by conventional and shell-vial cell culture isolation and to detect CMV antigenemia, were processed. The avidity index IgG-CMV (AI IgG-CMV) less than 60% was defined as a positive result. CMV infection and disease were defined. RESULTS: The avidity index was < 60% in 16.3% of all patients and in 68.7% of patients with CMV disease. AI IgG-CMV was positive in 81.8% of patients with primary CMV disease and 9.1% with secondary CMV disease. The mean avidity index reading was 35% in primary CMV disease, 88.3% in secondary CMV disease (p < 0.001) and 87.9% in infected patients without CMV disease criterion (p < 0.001). The sensitivity, specificity, VPP and VPN of avidity index IgG-CMV were 85.7%, 97.4%, 75.0% and 94.9% respectively, in primary CMV disease diagnostic respect to all patients with microbiological evidence of active CMV infection. CONCLUSIONS: Avidity index IgG-CMV seems to be a good serological test to diagnose primary CMV disease with only one serum, probably with independence of patients immune state.

Adult↗
PubMed2000

Combination of microneutralization and avidity assays: improved diagnosis of recent primary human cytomegalovirus infection in single serum sample of second trimester pregnancy.

Estimation of IgG avidity index is a classical serological method. Antibodies with low avidity are detectable at a very early stage of infection whereas high avidity antibodies indicate past infection. Recently, it was shown that the neutralization assay can be routinely used as a reliable method for differentiating between acute primary and non-primary infection in a single serum sample because the first neutralizing titers (NT) appeared after an average of 13 weeks (range, 10-17 weeks). A low positive NT titer in the presence of specific IgM antibodies, however, still represents a diagnostic problem especially if blood sampling occurred after the 12th week of gestation. To overcome this problem the combination of NT and IgG avidity tests was evaluated. Human cytomegalovirus (HCMV) IgG avidity indices of 350 serum samples from 227 pregnant women were investigated using 6M urea in the washing buffer. HCMV specific IgG antibodies reached full maturation approximately 20-22 weeks after seroconversion and low IgG avidity is therefore a marker of primary infection. The combined application of the microneutralization and avidity assays was shown to serve as a helpful tool in diagnosis of a recent primary HCMV infection of second trimester pregnancy particularly when previous serological data were not available.

Antibodies, Viral↗