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PubMed1993

Allotypic dependency of the specificity and avidity of human monoclonal IgM rheumatoid factors derived from rheumatoid synovial cells.

OBJECTIVE: To better understand the genetic derivation and pathogenicity of rheumatoid factor (RF) molecules in rheumatoid arthritis (RA), we have focused our studies on rheumatoid synovial cells (RSC). METHODS: Five monoclonal human IgM rheumatoid factor (mRF)-secreting hybridomas were produced from the RSC of an RA patient. Fine subclass specificities and avidities of these RSC mRFs were compared with several paraprotein monoclonal IgM RFs using direct binding (reactivity) and competitive inhibition (specificity and avidity) enzyme-linked immunosorbent assays. RESULTS: The following observations were made: 1) RSC mRF had greater avidity for IgG than did paraprotein mRF; 2) 4 of the 5 RSC RF were highly avid for IgG3; and, 3) the avidity of RSC RF binding for IgG3 was highest for IgG molecules expressing the G3m(5) allotype. CONCLUSION: We conclude that RSC RF have different specificities and avidities than do paraprotein RF. This may suggest an antigen-driven process in RA synovium, with the production of higher-avidity IgG3m(5)-specific RSC RF, which could have special pathogenetic importance.

Adult↗
PubMed1984

Sequential development of helper and suppressor functions, antibody titers and functional avidities to a streptococcal antigen in rhesus monkeys.

Sequential development of antibody titer, functional avidity, helper and suppressor activities were investigated in rhesus monkeys. These were immunized with a single dose of 0.1 microgram to 10 mg of a streptococcal protein antigen (SA) in aluminium hydroxide. The IgG antibody titers followed the classical pattern first established in mice, of high-dose and low-dose tolerance with intermediate doses of immunity. This was correlated with a similar pattern of functional avidity of IgG antibodies, as measured by a dissociation assay. Helper and suppressor functions were assayed in parallel by inducing the corresponding factors from monkey lymphocytes in Marbrook flasks and testing the factors which cross the species barrier in cooperative cultures with CBA mouse spleen B cells. A progressive modulation of helper and suppressor activities was elicited by the increasing doses of SA, during the initial 28 days after immunization. Thus, dominant suppressor with minimal helper activity, IgG antibody titer and functional avidity were elicited by 0.1 microgram SA. However, 1 or 10 micrograms SA induced dominant helper with minimal or transient suppressor activity and high IgG antibody titers and functional avidity. Somewhat intermediate responses were elicited by 100 micrograms SA, but 1 mg and especially 10 mg SA induced dominant suppressor and minimal helper activity, with low IgG antibody titers and functional avidities. When the immune response was established, about 28 days after immunization, the intermediate dose of SA elicited IgG antibodies with high titer and functional avidity, high T cell helper but low suppressor activities. In contrast, both high- and low-dose SA induced partial tolerance, with low IgG antibody titer, functional avidity and T cell helper activity. These studies suggest cyclical development of helper and suppressor functions during the 4 weeks after immunization. The emergence of a dominant helper or suppressor function is antigen dose dependent.

Animals↗
PubMed2002

Immunoglobulin G antibody avidity assay for serodiagnosis of hepatitis C virus infection.

It has been reported that the avidity of specific IgG antibody is lower in primary viral infection than in chronic viral infection. However, few studies have been reported on the IgG avidity in hepatitis C virus (HCV) infection. In the present study, 36 patients with antibody to HCV (anti-HCV) were examined for IgG avidity by an enzyme immunoassay with or without urea elution. The avidity index was significantly low in patients with primary HCV infection (7.7 +/- 6.8%, mean +/- SD), compared with patients with chronic HCV infection (77.0 +/- 21.8%) and individuals with past HCV infection (44.5 +/- 12.6%). Temporal changes of IgG avidity were examined in six patients with primary HCV infection. The avidity index was low in the acute phase of the infection and then increased with time. These results suggest that the avidity assay for IgG anti-HCV is a useful method for distinguishing primary HCV infection from chronic or past HCV infection.

Acute Disease↗
PubMed1992

Differential IgG avidity to rubella virus structural proteins.

Avidity maturation of IgG antibody responses directed against the structural proteins of rubella virus (E1, E2, and C) as well as whole rubella virus (RV) was assessed at sequential time intervals in 7 individuals following serologically confirmed wild rubella infection. Individual structural proteins were purified from tissue culture supernatants by differential centrifugation, followed by preparative SDS-PAGE under non-reducing conditions. Avidity of IgG anti-rubella responses was measured by using the 8 M urea elution technique and results expressed as an elution ratio [ER(%)]. A low mean ER(%) of 23% was determined for E1-specific IgG responses during the 10-20 day period following onset of clinical rubella, with subsequent maturation of avidity ER(%) values to 52%, 75%, and 84% at 3 months, 1 year, and 2 years, respectively, post-rubella. In contrast, IgG anti-E2 responses showed minimal avidity maturation with ER(%) values of 20%, 29%, 30%, and 31% over the same time intervals. Similarly, responses to the capsid protein (C) remained at low avidity ER(%) values of 21%, 29%, 36%, and 35% over the 2 year follow-up period. The avidity maturation values for IgG directed against whole RV preparations paralleled observations for E1-specific responses with ER(%) values of 23%, 52%, 85%, and 87%, respectively. These data support the need to assess individual protein-specific antibody avidities in order to more fully understand viral-specific immune responses.

Antibodies, Viral↗
PubMed1993

Avidity of IgG antibodies to human herpesvirus-6 distinguishes primary from recurrent infection in organ transplant recipients and excludes cross-reactivity with other herpesviruses.

A newly developed IgG antibody avidity test for human herpesvirus-6 (HHV-6) was used in a study of primary and recurrent HHV-6 antibody responses in immunocompromised solid organ graft recipients. In a primary HHV-6 infection low avidity antibody was detected which matured to high avidity within 5 months whereas, in contrast, high avidity antibody was found in three recurrent infections thus showing the ability of the test to discriminate between primary and recurrent infection in immunosuppressed patients. Six HHV-6 seropositive transplant patients who experienced a subsequent primary human cytomegalovirus (CMV) infection had high avidity concurrent HHV-6 antibody rises, thus excluding a cross-reaction from the low avidity antibodies generated in the primary CMV response and providing evidence of recurrent HHV-6 infection. Four further HHV-6 seropositive patients with proven primary Epstein-Barr virus (EBV) infection were also studied; in each of these cases high avidity HHV-6 antibody rises were seen likewise suggesting recurrent HHV-6 infection. The test is therefore of value in the investigation of herpesvirus infections in transplant patients.

Adolescent↗
PubMed1994

Measurement of antibody avidity for hepatitis C virus distinguishes primary antibody responses from passively acquired antibody.

A new IgG antibody avidity test for hepatitis C virus (HCV) has been developed and was validated using sera from 12 renal dialysis patients infected with HCV. In primary HCV infection low avidity antibody (mean avidity index 24%) was detected within 50 days of seroconversion whereas in long-term infection (at least 300 days after seroconversion), the mean avidity index was high (88%); in five patients, the avidity index was shown to increase rapidly as time elapsed after primary infection, whereas immunosuppressive therapy was found to delay maturation of the immune response in two further patients. The assay was then employed to confirm that a spurious outbreak of primary HCV infection in eight bone marrow transplant patients was explicable by passive acquisition of high avidity anti-HCV after intravenous immunoglobulin therapy. It is concluded that this avidity test will have an important role in the investigation of HCV infection in patients.

Antibody Affinity↗
PubMed1995

Detection of acute measles infections by indirect and mu-capture enzyme immunoassays for immunoglobulin M antibodies and measles immunoglobulin G antibody avidity enzyme immunoassay.

An avidity test for measles IgG was developed and applied to the study of IgG immunoglobulin maturation kinetics in follow-up sera from 12 patients with known acute primary and convalescent measles and sera from blood donors. The avidity of the IgG anti-measles responses was measured using the 8 M urea elution technique, the results being expressed as the percentage ratio between the test readings for eluted and noneluted samples. The IgG avidity results were compared with those of indirect and mu-capture IgM enzyme immunoassays. This test was capable of detecting low-avidity antibodies at the acute phase of measles up to 7 weeks, and increasing avidity through immunosaturation during the convalescent phase. The avidity in these samples did not reach the level found in the samples of the blood donors under the follow-up time. Although a limited number of serum samples was examined, the results suggest that the measles IgG avidity test is a powerful tool for differentiating primary measles infection from the convalescent phase.

Acute Disease↗
PubMed1997

Immunoglobulin G avidity in the serodiagnosis of congenital rubella syndrome.

The avidity of specific IgG was investigated in three infants with serologically verified congenital rubella infection. Two sera were taken from each infant: the first soon after birth and the second at the age of 23 to 31 months. Avidity of specific IgG was measured by a protein-denaturing enzyme immunoassay using urea as the elution factor, and avidity then determined by the end-point ratio (derived from antibody titration) and the avidity index methods. Rubella-specific IgM was present in the first sera of all patients, but not in the second sera. However, low avidity of specific IgG persisted in two children until age 23 to 31 months, as determined by the end-point ratio method. These data are in agreement with the findings of previous studies of avidity in congenital rubella, and show the usefulness of the protein-denaturing IgG-avidity assays employing the end-point ratio method for serological diagnosis of congenital rubella even after disappearance of specific IgM.

Antibodies, Viral↗
PubMed1995

Avidity distribution of antibodies against peripheral nerve myelin in patients with polyneuropathy associated with IgM monoclonal gammopathy and in healthy controls.

To elucidate the role and nature of antibodies against peripheral nerve myelin (PNM) we studied their avidity distribution. Twelve patients with demyelinating polyneuropathy associated with IgM monoclonal gammopathy were compared with 12 healthy blood donors previously found to have anti-PNM antibodies of IgM isotype. For comparison, the avidity distribution of IgM antibodies against the varicella zoster antigen in 10 patients with herpes zoster infection was also studied. Microtitre plates containing antibody bound to antigen were exposed to increasing concentrations of sodium thiocyanate (NaSCN) followed by an ELISA assay. NaSCN changes the ion strength and the pH, and thereby the critical conditions for antibody-antigen binding. Resistance to NaSCN was used as a measure of antibody avidity. Anti-PNM antibodies from patients with monoclonal gammopathy were of predominantly low avidity whereas antibodies from blood donors were of predominantly high avidity. Avidity index, representing the molar concentration of NaSCN required to reduce the initial absorbance values by 50%, was on average 11.7 times higher in blood donors (range 0.24-2.65, mean = 0.82) than in patients with monoclonal gammopathy (range 0.04-0.10, mean = 0.07) (p = 0.002). On the other hand, patients with monoclonal gammopathy had on average a 100-fold higher relative concentration of antibodies against PNM compared to blood donors (range 4.1-392.6 AU, mean 85.0 AU, and range 0.2-1.7 AU, mean 0.85 AU, respectively) (p = 0.002). Antibodies against the varicella zoster antigen from patients with herpes zoster showed a high avidity index (range 0.25-2.6, mean = 1.24). Using Western blot, several 14-30 kDa proteins in PNM were found to be the target antigen for IgM anti-PNM antibodies in both patients with monoclonal gammopathy and polyneuropathy, and in blood donors.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed2005

Modulation of CD8+ T cell avidity by increasing the turnover of viral antigen during infection.

The increased potency of high avidity CD8+ T cells for the clearance of viral infections has been well documented. We have previously reported the novel finding that intranasal infection with the paramyxovirus SV5 induces a CD8+ T cell response to the SV5 P protein that is almost exclusively of high avidity. Based on our results that the level of peptide presentation is a critical factor in the selective expansion of high versus low avidity cells in vitro, we hypothesized that the avidity of the anti-viral response generated in vivo could be altered by increasing the turnover of the P protein during viral infection through linkage to ubiquitin (UbP). Infection with a virus expressing UbP (VV-UbP) elicited a significant increase in low avidity cells in both BALB/c and C3H mice compared to the almost exclusively high avidity response elicited by VV-P. Our results are the first demonstration of the control of avidity during the antiviral response through an engineered change to a viral antigen. The implications of our findings for vaccine development are discussed.

Animals↗
PubMed2006

Tumor fluoro-2-deoxy-D-glucose avidity on positron emission tomographic scan predicts mortality in patients with early-stage pure and mixed bronchioloalveolar carcinoma.

OBJECTIVE: Bronchioloalveolar carcinoma is a clinically heterogeneous subtype of non-small cell lung carcinoma that frequently has low 2-[18F]fluoro-D-glucose (FDG) uptake on positron emission tomographic scanning. We investigated whether tumor FDG avidity was associated with worse survival among patients with completely resected node-negative pure and mixed bronchioloalveolar carcinoma. METHODS: We performed a cohort study of 36 patients who had completely resected pure and mixed bronchioloalveolar carcinoma between 1998 and 2004, who had no hilar or mediastinal lymph node metastases, and who had undergone a preoperative positron emission tomographic scan. Tumor FDG avidity was defined as a standardized uptake value of 2.5 or greater. Survival analysis was performed with a proportional hazards model. RESULTS: Of 36 patients studied, 26 patients (72%) were alive and 10 patients (28%) were dead after a median follow-up of 31 months (interquartile range 17-41 months). Seventeen patients (47%) had FDG-avid tumors, and 19 patients (53%) had non-avid tumors. Three-year survival was 49% in the FDG-avid group and 95% in the non-avid group (P = .005). FDG avidity had a hazard ratio of death of 8.6 (95% confidence interval 1.4-244.7, P = .02) after adjusting for tumor size, the presence of multifocal bronchioloalveolar carcinoma, and the presence of histologically mixed bronchioloalveolar carcinoma. CONCLUSIONS: Preoperative tumor FDG standardized uptake value of 2.5 or greater on positron emission tomography is a powerful predictor of long-term mortality in patients with lymph node-negative pure and mixed bronchioloalveolar carcinoma who undergo complete surgical resection. Patients with a high level of FDG uptake (standardized uptake value > or = 2.5) may benefit from adjuvant chemotherapy or more frequent clinical follow-up.

Adenocarcinoma, Bronchiolo-Alveolar↗
PubMed2005

IgG avidity pattern in cattle after ingestion of Neospora caninum oocysts.

The avidity (functional affinity) of specific antibodies are being used to estimate duration of bovine Neospora caninum infection. Here, we report for the first time the avidity pattern in cattle orally inoculated with N. caninum oocysts. In all, 16 pregnant cows and 7 calves were administered N. caninum oocysts. In the cows, the avidity increased during the early course of infection. In all but one, the avidity was < or = 35 during the first 6 weeks after infection and no cow had an avidity value >50 until week 9. The calves were sampled either week 6 (n = 3) or week 9 (n = 9) after infection, and by then had avidities between 2 and 17. The results are in agreement with results from previous investigations of naturally infected cattle, and calves that were experimentally infected with tachyzoites. They further validate the ability of the N. caninum iscom avidity ELISA to accurately assess the duration of infection.

Animals↗
PubMed2005

Evaluation of high functional avidity CTL to Gag epitope clusters in EIAV carrier horses.

Cytotoxic T lymphocytes (CTL) are critical for lentivirus control including EIAV. Since CTL from most EIAV carrier horses recognize Gag epitope clusters (EC), the hypothesis that carrier horses would have high functional avidity CTL to optimal epitopes in Gag EC was tested. Twenty-two optimal EC epitopes were identified; two in EC1, six in EC2, and seven each in EC3 and 4. However, only five of nine horses had high functional avidity CTL (<or=11 nM) recognizing six epitopes in EC; four in relatively conserved EC3; and one each in EC1 and 2. Horses with high functional avidity CTL had significantly more days since the last clinical episode than horses with low avidity CTL, and this was not explained by analyzing duration of infection. Furthermore, there was a significant inverse correlation between the CTL functional avidity of the nine horses and the days since the last clinical episode. Gag CTL epitope escape variants were found in three horses, but only one of these was recognized by high functional avidity CTL. Thus, not all carrier horses had high functional avidity CTL to Gag EC, but those that did had longer periods without disease episodes.

Amino Acid Sequence↗
PubMed2002

p38-avidity-ELISA: examination of herds experiencing epidemic or endemic Neospora caninum-associated bovine abortion.

An enzyme-linked immunosorbent assay (ELISA) was established to measure the avidity of bovine IgG directed against p38, a surface antigen (NCSRS2) of Neospora caninum tachyzoites. In the sera of dams intravenously infected with N. caninum NC-1, the p38-specific avidity increased from initially below 40% up to avidity indices between 50 and 80% after days 23 and 91 p.i. The p38-avidity-ELISA was used to examine various herds that had experienced endemic and epidemic N. caninum-associated bovine abortions. In herds with endemic abortion, generally high avidity indices of N. caninum-specific IgG were detected. This finding and the observation of an association between the seropositivity of dams and that of their offspring suggested a predominantly vertical transmission of the parasite among the animals of these herds, thus indicating chronic infection of these cattle. In contrast, for herds experiencing epidemic abortion: (i) an association regarding seropositivity of dams and their daughters could not be shown and (ii) a generally low avidity of p38-specific IgG in the sera from aborting dams was determined. This indicates recent postnatal transmission of N. caninum in these herds. A linear regression model explaining the avidity of p38-specific IgG was significantly influenced by the time span between sampling and the occurrence of the first abortion of the epidemic in herds with an N. caninum-associated abortion storm. Another factor significantly contributing to the model was the proportion of dams at risk that had aborted in the herds (i.e. the severity of the abortion epidemic). A possible explanation for this observation is that herds experiencing heavy abortion are sampled earlier after the onset of the epidemic than others that have a less severe abortion storm.

Abortion, Veterinary↗
PubMed1998

Lipiodol avidity of neuroendocrine liver metastases.

AIMS: Lipiodol has been shown to concentrate in most hepatocellular carcinomas as well as in some liver metastases, including those of neuroendocrine origin. Our aim was to determine the proportion of neuroendocrine liver metastases that take up lipiodol and to identify tumour characteristics that predict avidity. METHODS: Avidity was assessed in 12 patients with neuroendocrine liver metastases by performing an abdominal CT scan immediately after selective hepatic arterial injection of 5 ml of unlabelled lipiodol and this was correlated with number and size of lesions as well as angiographic and plain CT scan features. RESULTS: In seven patients the tumours displayed lipiodol avidity (four solitary, three multiple); five patients had non-avid lesions (all multiple). A large dominant liver tumour was the only predictor of avidity (mean diameter of largest lesion 9 cm vs. 3 cm for patients with non-avid tumours: P=0.01). Avidity was not related to vascularity or CT density of lesions. CONCLUSIONS: Although this is a small study, it would appear that approximately 50% of neuroendocrine liver metastases selectively concentrate lipiodol, which could have implications for targeted cancer therapy.

Adult↗
PubMed1997

Maturation of rubella IgG avidity over time after acute rubella infection.

BACKGROUND: As the incidence of rubella has diminished, the proportion of unspecific rubella IgM reactivity among all samples with rubella IgM reactivity has increased. It is important to distinguish IgM reactivity caused by primary infection from that caused by reinfection or persistence, especially in pregnant women, as termination of pregnancy should be considered when primary rubella is diagnosed during the first trimester. OBJECTIVES: To elucidate the changes over time of the avidity of rubella IgG antibodies after acute rubella infection. STUDY DESIGN: Serial samples, 84, were collected from 15 patients up to 4-5 months after acute rubella infection. Rubella specific IgG avidity was tested by the eluting principle adding 35 mM diethylamine to the washing buffer of a commercially available rubella IgG ELISA. As controls, 137 samples from women with remote rubella and 94 samples from patients with a rubelliform rash, were tested. RESULTS: The avidity index increased steadily in all patients during the observation time. A low avidity index (< 40%) was seen up to 6 weeks after onset of rash. A high avidity index (> 60%) was not observed until 13 weeks after infection and only in four of the 15 patients during the observation time. CONCLUSIONS: An increase of rubella IgG antibody avidity was seen during the whole observation time but was most pronounced during the first 3 months after onset of rash. Measurement of rubella IgG avidity is a good supplemental test for cases with rubella IgM reactivity to confirm or exclude a recent rubella infection.

Acute Disease↗
PubMed1998

Kinetics of circulating cytotoxic T lymphocyte precursors that have a high avidity for donor antigens: correlation with the rejection status of the human cardiac allograft.

Studies on graft infiltrating cells demonstrated that accumulation of cytotoxic T lymphocytes (CTL) with high avidity for donor antigens (Ag) coincided with acute cardiac rejection. In the present study, we analyse whether such high-avidity CTL are present within the peripheral blood of cardiac transplant recipients and whether their kinetics correspond with the rejection status of the allograft. Using limiting dilution analysis (LDA), donor-specific CTL were enumerated in serial blood samples of seven patients. From each patient, 7-11 samples were obtained during the first year after transplantation and up to three samples were obtained at a later date. Enumerated donor-specific CTL were divided into CTL with high or low avidity for donor Ag, depending on their sensitivity to CD8-blocking. In contrast to the situation in the graft, the donor-specific CTL present within the peripheral blood were CTL precursors (pCTL) and not fully mature CTL (cCTL). The number of donor-specific pCTL among peripheral blood cells fluctuated irrespective of the rejection grade of the allograft, indicating that the frequency of circulating donor-specific CTL does not reflect the immunological status of the allograft. During acute cardiac rejection, 66% (median) of the circulating donor-specific pCTL had a high avidity for donor Ag. This percentage significantly exceeded pre- and postrejection values obtained during the first year post-transplantation (median, 39% and 37%, respectively). The disparity in avidity increased even further more than 1 year after transplantation, when stable engraftment was achieved. Among donor-specific pCTL in peripheral blood, those with a high avidity were absent (median, 0%). Hence the avidity of circulating donor-specific CTL might inform us about the immune status of the cardiac allograft.

Antigens↗
PubMed2000

Circulating donor-specific cytotoxic T lymphocytes with high avidity for donor human leukocyte antigens in pediatric and adult cardiac allograft valved conduit recipients.

OBJECTIVE: Specific immunological responses may be involved in the process of cryopreserved allograft valved conduit (AVC) degeneration, which is more frequently seen in young recipients. Rejection of heart and corneal allografts is preceded by an increase in the fraction of cytotoxic T lymphocytes (CTL) with high avidity for donor human leukocyte antigens (HLA) circulating in both peripheral blood and the affected graft. These donor-specific high-avidity CTLs are regarded as the destructive cells capable of causing graft damage. To monitor the precursors of these cells (CTLp) in young and adult AVC recipients, in vitro quantitative tests were performed on sequentially taken blood samples to quantitate CTLp frequencies and their avidity for donor antigens. METHOD: Six children and nine adults who received a cryopreserved AVC in the period between 1994 and 1997 were included in the study. From these patients, two to six blood samples were obtained up to 3 years after valve implantation. The number of circulating CTLp present within the peripheral blood mononuclear cell (PBMC) population was determined by limiting dilution analysis (LDA). The fraction of CTLp with high avidity for donor HLA class I was determined by addition of CD8 monoclonal antibodies (mAb) during the cytotoxic phase of the assay. Third-party stimulator cells were used to verify the donor-specificity of the response. RESULTS: The number of donor-specific CTLp increased significantly in the period 6-12 months after AVC implantation, while third-party-specific CTLp frequencies were not affected. Additionally, we found a significant increase of the high-avidity fraction of CTLp directed against donor antigens as early as during the first 6 months after AVC implantation. The fraction of high-avidity CTLp remained significantly higher post- compared with pre-implantation, even after 12 months. We observed no significant difference in the kinetics of CTLp frequencies between pediatric and adult AVC recipients. CONCLUSION: Implantation of cryopreserved human AVC induces an increase in the total number of circulating CTLp directed against donor HLA class I in both adults and children. The shift towards more destructive high-avidity CTLp in the peripheral blood indicates their potential damaging effect towards the heart valve allograft.

Adolescent↗