Development Of Antibody Responses Research Articles

Assessing the impact of autologous neutralizing antibodies on rebound dynamics in postnatally SHIV-infected ART-treated infant rhesus macaques.

The presence of antibodies against HIV in infected children is associated with a greater capacity to control viremia in the absence of therapy. While the benefits of early antiretroviral treatment (ART) in infants are well documented, early ART may interfere with the development of antibody responses. In contrast to adults, early treated children lack detectable HIV-specific antibodies, suggesting a fundamental difference in HIV pathogenesis. Despite this potential adverse effect, early ART may decrease the size of the latent reservoir established early in infection in infants, which can be beneficial in viral control. Understanding the virologic and immunologic aspects of pediatric HIV is crucial to inform innovative targeted strategies for treating children living with HIV. In this study, we investigate how ART initiation time sets the stage for trade-offs in the latent reservoir establishment and the development of humoral immunity and how these, in turn, affect posttreatment dynamics. We also elucidate the biological function of antibodies in pediatric HIV. We employ mathematical modeling coupled with experimental data from an infant nonhuman primate Simian/Human Immunodeficiency Virus (SHIV) infection model. Infant Rhesus macaques (RMs) were orally challenged with SHIV.C.CH505 375H dCT four weeks after birth and started treatment at different times after infection. In addition to viral load measurements, antibody responses and latent reservoir sizes were measured. We estimate model parameters by fitting viral load measurements to the standard HIV viral dynamics model within a nonlinear fixed effects framework. This approach allows us to capture differences between rhesus macaques (RMs) that develop antibody responses or exhibit high latent reservoir sizes compared to those that do not. We find that neutralizing antibody responses are associated with increased viral clearance and decreased viral infectivity but decreased death rate of infected cells. In addition, the presence of detectable latent reservoir is associated with less robust immune responses. These results demonstrate that both immune response and latent reservoir dynamics are needed to understand post-rebound dynamics and point to the necessity of a comprehensive approach in tailoring personalized medical interventions.

#2765 EVALUATION OF ANTIBODY RESPONSES TO SARS-COV-2 VACCINES IN PATIENTS WITH CKD

Abstract Background and Aims Patients with CKD are highly vulnerable to the serious complications of severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) infections and thus stand to benefit from vaccination. Therefore, our aim is to evaluate the effectiveness of available COVID-19 vaccines in patients with CKD. Method A total of 198 consecutive adult CKD patients in a single center in Uzbekistan were evaluated. Patients were divided into four cohorts: haemodialysis (HD) (n=116), peritoneal dialysis (PD) (n=11), kidney transplant (KT) recipients (n=22) and non-dialysis CKD (stages 4 and 5, eGFR <30 mL/min/1.73 m2) (n=49) patients (Fig. 1). All the screened participants received the complete vaccination with any of the available vaccines: Pfizer-BioNTech®, Moderna®, AstraZeneca®, Sputnik V®, ZF-UZ-VAC2001®. At baseline and on day 28 after the last vaccine dose, antibodies were measured and compared between cohorts. Factors associated with development of antibodies were analyzed. Results Among the 198 participants in screened group, 109 (55%) were male and the mean age was 54.3 ± 11.2 years. Vaccine distribution was as follows: 25 patients (12.6%) received Pfizer-BioNTech, 42 (21.2%) Moderna, 28 (14.1%) AstraZeneca, 36 (18.2%) Sputnik V and 67 (33.9%) ZF-UZ-VAC2001 vaccines. The distribution of the different types of vaccines differed between groups (Table 1). Development of antibody responses at 28 days after completing vaccination has been tested in 155 patients (97 HD, 8 PD, 16 KT recipients, 34 non-dialysis CKD patients). After the 28 days of completing vaccination, 137 patients (88%) presented antibody responses, 3 (2%) were doubtful and 15 (10%) had a negative result. Patients that did not develop antibody responses after vaccination included: 3 (2%) HD patients, 2 (1%) PD patients, 2 (1%) non-dialysis CKD patients and 8 (6%) KT recipients (P < 0.01). Patients receiving Pfizer-BioNTech, Moderna and AstraZeneca developed higher antibody titres than those receiving Sputnik V and ZF-UZ-VAC2001 vaccines (P < 0.01). These differences were significant in all cohort of patients. Factors associated with negative antibody response were also increasing age (p<0.01), history of CVD (p = 0.02), lower eGFR (P < 0.05). Previous COVID-19 infection was associated with higher antibody titres at 28 days (P < 0.05). We did not find significant association between antibody response and gender, ethnicity, BMI, diabetes and donor type. Conclusion Our study has shown a much lower seropositivity rate among the KT recipients after of SARS-COV-2 vaccine than other cohort of CKD patients, suggesting that KT patients require persistent isolation measures and booster doses of a COVID-19 vaccine. Increasing age, history of CVD and lower eGFR were factors associated with a non-response. Potential differences between COVID-19 vaccines should be explored in prospective long-term follow-up studies. These findings complement those of earlier studies and highlight the need for a tailored approach to the vaccination.

Factors Associated With Reduced Anti-SARS-CoV-2 Antibody Responses After mRNA Vaccination in Kidney Transplant Recipients on Belatacept

Belatacept is a costimulation blocker used for maintenance immunosuppression in kidney transplant recipients (KTRs) as an alternative to calcineurin inhibitors.1 Studies evaluating SARS-CoV-2 vaccine responses in KTRs have shown reduced antibody responses in KTRs on belatacept.2-4 Nevertheless, many of these studies included only a small number of patients on belatacept,5 and had low rates of seroconversion, limiting the ability to evaluate factors associated with the development of antibody responses.

Assessment of exposure to influenza A viruses in pigs between weaning and market age

Influenza A viruses (IAVs) are common causes of respiratory infection in pigs. The objective of this study was to characterize the circulation of IAVs between weaning and market age on the basis of development of antibody response and molecular epidemiology of detected viruses. Two batches of weaned pigs were followed in the nursery and finisher barns with a sample of 81 and 75 pigs. Nasal swabs and blood samples were collected from individual pigs for virological and serological analyses. A H3N2 subtype virus, of cluster IV, was detected in Study 1, with a maximum of 97.9% identity to HA gene of viruses previously isolated in Ontario. In Study 2, a H1N1 subtype virus, of 2009 H1N1 pandemic lineage, was detected, with a maximum of 97.8% identity to HA gene of viruses previously isolated in Ontario. On the basis of HA gene, it was observed that pigs were being detected with the same virus over time. The existence of antibody titers for IAV other than the isolated one confirmed that more than one subtype can circulate in the same population. In Study 1, pigs with higher numbers of IAV detection had lower serological titers for the same virus that was confirmed to circulate in the nursery (P < 0.01). Thorough knowledge of all endemic viral strains is fundamental for development of infection and disease control, particularly in complex production systems. This may include consideration of sampling and testing strategies which could detect circulation of all IAV variants, even if they have low prevalence.

Immunogenicity of Protein Therapeutics: A Lymph Node Perspective.

The continuous development of molecular biology and protein engineering technologies enables the expansion of the breadth and complexity of protein therapeutics for in vivo administration. However, the immunogenicity and associated in vivo development of antibodies against therapeutics are a major restriction factor for their usage. The B cell follicular and particularly germinal center areas in secondary lymphoid organs are the anatomical sites where the development of antibody responses against pathogens and immunogens takes place. A growing body of data has revealed the importance of the orchestrated function of highly differentiated adaptive immunity cells, including follicular helper CD4 T cells and germinal center B cells, for the optimal generation of these antibody responses. Understanding the cellular and molecular mechanisms mediating the antibody responses against therapeutics could lead to novel strategies to reduce their immunogenicity and increase their efficacy.

HIV-1 Antibody Neutralization Breadth Is Associated with Enhanced HIV-Specific CD4+ T Cell Responses.

Antigen-specific CD4(+) T helper cell responses have long been recognized to be a critical component of effective vaccine immunity. CD4(+) T cells are necessary to generate and maintain humoral immune responses by providing help to antigen-specific B cells for the production of antibodies. In HIV infection, CD4(+) T cells are thought to be necessary for the induction of Env-specific broadly neutralizing antibodies. However, few studies have investigated the role of HIV-specific CD4(+) T cells in association with HIV neutralizing antibody activity in vaccination or natural infection settings. Here, we conducted a comprehensive analysis of HIV-specific CD4(+) T cell responses in a cohort of 34 untreated HIV-infected controllers matched for viral load, with and without neutralizing antibody breadth to a panel of viral strains. Our results show that the breadth and magnitude of Gag-specific CD4(+) T cell responses were significantly higher in individuals with neutralizing antibodies than in those without neutralizing antibodies. The breadth of Gag-specific CD4(+) T cell responses was positively correlated with the breadth of neutralizing antibody activity. Furthermore, the breadth and magnitude of gp41-specific, but not gp120-specific, CD4(+) T cell responses were significantly elevated in individuals with neutralizing antibodies. Together, these data suggest that robust Gag-specific CD4(+) T cells and, to a lesser extent, gp41-specific CD4(+) T cells may provide important intermolecular help to Env-specific B cells that promote the generation or maintenance of Env-specific neutralizing antibodies. One of the earliest discoveries related to CD4(+) T cell function was their provision of help to B cells in the development of antibody responses. Yet little is known about the role of CD4(+) T helper responses in the setting of HIV infection, and no studies to date have evaluated the impact of HIV-specific CD4(+) T cells on the generation of antibodies that can neutralize multiple different strains of HIV. Here, we addressed this question by analyzing HIV-specific CD4(+) T cell responses in untreated HIV-infected persons with and without neutralizing antibodies. Our results indicate that HIV-infected persons with neutralizing antibodies have significantly more robust CD4(+) T cell responses targeting Gag and gp41 proteins than individuals who lack neutralizing antibodies. These associations suggest that Gag- and gp41-specific CD4(+) T cell responses may provide robust help to B cells for the generation or maintenance of neutralizing antibodies in natural HIV-infection.

H2N2 live attenuated influenza vaccine is safe and immunogenic for healthy adult volunteers

H2N2 influenza viruses have not circulated in the human population since 1968, but they are still being regularly detected in the animal reservoir, suggesting their high pandemic potential. To prepare for a possible H2N2 pandemic, a number of H2N2 vaccine candidates have been generated and tested in preclinical and clinical studies. Here we describe the results of a randomized, double-blind placebo-controlled phase 1 clinical trial of an H2N2 live attenuated influenza vaccine (LAIV) candidate prepared from a human influenza virus isolated in 1966. The vaccine candidate was safe and well-tolerated by healthy adults, and did not cause serious adverse events or an increased rate of moderate or severe reactogenicities. The H2N2 vaccine virus was infectious for Humans. It was shed by 78.6% and 74.1% volunteers after the first and second dose, respectively, most probably due to the human origin of the virus. Importantly, no vaccine virus transmission to unvaccinated subjects was detected during the study. We employed multiple immunological tests to ensure the adequate assessment of the H2N2 pandemic LAIV candidate and demonstrated that the majority (92.6%) of the vaccinated subjects responded to the H2N2 LAIV in one or more immunological tests, including 85.2% of subjects with antibody responses and 55.6% volunteers with cell-mediated immune responses. In addition, we observed strong correlation between the H2N2 LAIV virus replication in the upper respiratory tract and the development of antibody responses.

Carrier induced epitopic suppression of antibody responses induced by virus-like particles is a dynamic phenomenon caused by carrier-specific antibodies

Pre-existing immunity against vaccine carrier proteins has been reported to inhibit the immune response against antigens conjugated to the same carrier by a process termed carrier induced epitopic suppression (CIES). Hence understanding the phenomenon of CIES is of major importance for the development of conjugate vaccines. Virus-like particles (VLPs) are a novel class of potent immunological carriers which have been successfully used to enhance the antibody response to virtually any conjugated antigen. In the present study we investigated the impact of a pre-existing VLP-specific immune response on the development of antibody responses against a conjugated model peptide after primary, secondary and tertiary immunization. Although VLP-specific immune responses led to reduced peptide-specific antibody titers, we showed that CIES against peptide–VLP conjugates could be overcome by high coupling densities, repeated injections and/or higher doses of conjugate vaccine.Furthermore we dissected VLP-specific immunity by adoptively transferring VLP-specific antibodies, B-cells or Thelper cells separately into naïve mice and found that the observed CIES against peptide–VLP conjugates was mainly mediated by carrier-specific antibodies.

Human Dendritic Cells Induce the Differentiation of Interleukin-21-Producing T Follicular Helper-like Cells through Interleukin-12

T follicular helper (Tfh) cells help development of antibody responses via interleukin-21 (IL-21). Here we show that activated human dendritic cells (DCs) induced naive CD4(+) T cells to become IL-21-producing Tfh-like cells through IL-12. CD4(+) T cells primed with IL-12 induced B cells to produce immunoglobulins in a fashion dependent on IL-21 and inducible costimulator (ICOS), thus sharing fundamental characteristics with Tfh cells. The induction of Tfh-like cells by activated DCs was inhibited by neutralizing IL-12. IL-12 induced two different IL-21-producers: IL-21(+)IFN-gamma(+)T-bet(+) Th1 cells and IL-21(+)IFN-gamma(-)T-bet(-) non-Th1 cells, in a manner dependent on signal transducer and activator of transcription 4 (STAT4). IL-12 also regulated IL-21 secretion by memory CD4(+) T cells. Thus, IL-12 produced by activated DCs regulates antibody responses via developing IL-21-producing Tfh-like cells and inducing IL-21 secretion from memory CD4(+) T cells. These data suggest that the developmental pathway of Tfh cells differs between mice and humans, which have considerable implications for vaccine development.

Influence of In-Feed Virginiamycin on the Systemic and Mucosal Antibody Response of Chickens

Subtherapeutic and prophylactic doses of virginiamycin are capable of altering the intestinal microbiota as well as increasing several growth parameters in chickens. In spite of the fact that the microbiota plays a role in shaping the host's immune system, little information is available on the effects of in-feed antibiotics on the chicken immune system. The objective of this study was to examine the effects of an antibiotic, virginiamycin, on the development of antibody responses. Chickens were fed diets containing no antibiotics, along with either subtherapeutic (11 ppm) or prophylactic (22 ppm) doses of virginiamycin. Chickens were then immunized with keyhole limpet hemocyanin (KLH) and sheep red blood cells systemically, and with BSA and KLH orally. Although antibodies were detected against BSA in the intestinal contents of birds that were orally immunized, there was no difference among different treatment groups. Systemic IgG, and to a lesser extent IgM, antibody responses to KLH were greater (P < 0.05) in birds fed a diet containing 11 or 22 ppm of virginiamycin compared with control birds fed no antibiotic. No treatment effect was found in the sheep red blood cell-immunized birds. Results of the present study implicate virginiamycin in enhancing antibody responses to some antigens in chickens. Further studies are required to determine to what extent these effects on antibody response are mediated through changes in the composition of the microbiota.

B Cells Discriminate the Rules of Engagement

How B cells discriminate antigen-receptor-mediated signals in development and navigate critical checkpoints in adaptive immune responses remains poorly resolved. In this issue of Immunity, conditionally ablate the main regulatory subunit of the calcineurin phosphatase complex in B cells to reveal both positive and negative influences on the development of antibody responses and B cell memory.

Effect of HLA DQ2, dietary exposure and coeliac disease on the development of antibody response to gliadin in children

Objective. To study the effect of HLA DQ2, dietary history and development of coeliac disease (CD) on the induction of antibody response to wheat gliadin and cow's milk, beta-lactoglobulin between 1 and 2.5 years of age in children who developed CD and in healthy children. Material and methods. Infants participating in a birth cohort study (the ABIS study) in Sweden were studied. Thirty-nine children developed CD (=cases), confirmed through biopsy, during follow-up until 2.5–5 years of age. A total of 181 healthy control children were matched for duration of exclusive breast-feeding, birth-weight, gender, maternal smoking and season of birth. IgG and IgA antigliadin and anti-beta-lactoglobulin antibodies were measured using enzyme immunoassay (EIA). The effects of HLA-risk genotypes, DQ2 and DQ8, on CD were also considered. Results. Children who developed CD had higher IgG and IgA antigliadin and anti-beta-lactoglobulin antibody levels at 1 year of age than controls (all comparisons: p<0.001). Similar differences were seen between cases with as yet undiagnosed CD by 1 year of age and controls, and also when cases were compared with HLA-matched controls. Higher levels of IgG and IgA antibodies to beta-lactoglobulin (p=0.003; p=0.001), but not to gliadin, were found in treated cases versus controls at 2.5 years of age. HLA-DQ2-positive healthy children had lower levels of IgG and IgA antigliadin antibodies than HLA-DQ2 negative controls at 1 year of age (p=0.004; p=0.012). Conclusions. Enhanced humoral response emerging not only to gliadin, but also to other food antigens seems to be primarily associated with CD. Poor induction of antibody response to wheat gliadin in healthy children with the HLA-DQ2 risk molecule could at least partly explain the genetic predisposition to gluten intolerance and CD.

The development of antibody responses in the infant.

The human infant is a major subject of immunization to prevent infectious disease. A better understanding of immune responses in human infants could lead to more effective immunization. Analysis of individual mechanisms is a prerequisite to understanding the whole response. We have examined the mutation and selection of immunoglobulin genes, mechanisms required for the maturation of antibody affinity. Mutations were rare in cord blood and were not detected in peripheral blood of infants under 10 days of age. Mutations were detected in most blood samples from infants aged 10 days to 2 months but the number of mutations was generally low compared with adults and there was limited evidence of selection. The ability to make and select mutated Ig increased over the 2-8 months period, but did not reach adult levels. Neonates differ from adults in the expression of several components of the immune system that may take part in affinity maturation, including cytokine receptors, antigen receptor and co-stimulator molecules. Thus, the mechanisms required to make high-affinity antibody develop gradually during the first year of life. Possible evolutionary reasons for this are discussed.

Molecular basis of hereditary C1q deficiency associated with SLE and IgA nephropathy in a Turkish family

Two siblings (case 1 and case 2) with homozygous C1q deficiency are described. Both presented with a photosensitive rash, and during follow-up case one developed SLE with nephrotic range proteinuria. Case 2 had microscopic hematuria with a past history of macroscopic hematuria. Renal biopsies revealed mesangioproliferative glomerulonephritis in case 1 and IgA nephropathy in case 2, a new finding in association with C1q deficiency. Since the classical pathway of complement plays a role in the development of antibody responses, the family was also evaluated for the immune response to hepatitis B vaccine. Antibody response to hepatitis B vaccine was normal in both affected members and the rest of the family. The A-, B- and C- chain genes of C1q were amplified by PCR and directly sequenced. A homozygous C to T point mutation was identified in genomic DNA isolated from the patients at codon 186 in the A chain that resulted in a premature stop codon. This mutation was present in both parents and both unaffected sibs in the heterozygous state. This mutation was identical to that previously described in a Slovakian family with C1q deficiency. Because of this finding, a series of 92 genomic DNA samples was screened from ethnically distinct patient groups with SLE to test the hypothesis that this mutation of C1q may be a widespread disease susceptibility gene. No further examples of this mutation were found.

Humoral response following russell's viper ( Daboia russelli siamensis) bites in myanmar

A prospective study of the development, intensity and protective ability of the antibody response to Russell's viper bite and its relation to the severity of envenoming was carried out in 15 patients 3 to 116 weeks after the bites using enzyme immunoassay. Retrospective screening in 123 cases revealed antibody in 112 123 (91%) which could be detected from 1 week to 15 years after the bite. A slow peaking (30 weeks) and waning of antibody response was observed in the majority of cases. Development of antibody response was related to the initial venom level, rather than to the delay between bite and antivenom therapy, or the dose of antivenom. Uraemia depressed the IgM response to venom.

In vivo CD40-gp39 interactions are essential for thymus-dependent humoral immunity. I. In vivo expression of CD40 ligand, cytokines, and antibody production delineates sites of cognate T-B cell interactions.

T-B cell interactions have a central role in the development of antibody responses. Upon activation, T helper (Th) cells express the ligand for CD40, gp39, which is essential for Th cell-dependent B cell activation. The cytokines produced by activated Th cells have a regulatory role in B cell differentiation. In this study, we investigated, using immunohistochemical techniques, the in vivo time course and localization of gp39 expression and cytokine production in relation to the specific antibody production. Both the immunization with keyhole limpet hemocyanin (KLH), a thymus-dependent (TD) antigen, and trinitrophenyl (TNP)-Ficoll, a thymus-independent type 2 (TI-2) antigen, induced Th cells to express gp39. The expression of gp39 was restricted to Th cells in the outer periarteriolar lymphocyte sheaths (outer-PALS) and around the terminal arterioles (TA). Incidentally, gp39+ Th cells were found in the corona of follicles, whereas gp39+ cells were never found in the germinal centers or marginal zones of the spleen. Maximum frequencies of gp39+ cells were observed 3 and 4 d after primary and secondary immunization with KLH. After injection of TNP-Ficoll, a marked increase in gp39+ cells was observed, confirming previous observations that activated T cells are involved in TI-2 antibody responses. Analysis of the in vivo cytokine production revealed that interleukin 2 (IL-2)-, IL-4- and interferon gamma (IFN-gamma)-producing cells (IFN-gamma-PC) developed according to similar kinetics as observed for gp39+ cells. IL-2-PC and IL-4-PC were present in higher frequencies as were IFN-gamma-PC in the immune response against TNP-KLH. Double staining experiments revealed gp39+ Th cells producing IL-2, IL-4, or IFN-gamma, suggesting that these cells were involved in both the initial activation as well as the differentiation process of B cells into antibody-forming cells. Dual immunohistochemical analysis revealed gp39+ T cells and cytokine-PC in close proximity to antigen-specific, antibody-forming B cells. In conclusion, this study shows that in vivo gp39 is expressed on activated Th cells after immunization with TD and TI-2 antigens. Furthermore, the time course and compartmentalization of gp39+ expression, cytokine production and antibody formation after immunization suggest that cognate T-B cell interactions and T cell-regulated B cell differentiation occur in the outer-PALS and around the TA of the spleen.

Epidemiologic and serologic definition of primary and secondary trichinosis in the Arctic.

A large outbreak of trichinosis acquired from walrus in Salluit in 1987 provided the immunologic and epidemiologic data from which two distinct clinical syndromes were identified. The first syndrome is the classic myopathic form with edema, fever, myalgia, and rash. The second is a persistent diarrheal illness with little edema or myalgia. The clinical presentations are paralleled by distinct differences in type and development of antibody response. The clinical and serologic profiles of the two syndromes support the hypothesis that the myopathic form represents a primary infection of Trichinella nativa, while the second represents a secondary infection in previously sensitized individuals.

Inhalation Exposure of Mice to Trimellitic Anhydride Induces Both IgG and IgE Anti-Hapten Antibody

The development of antibody responses resulting from inhalation exposure to chemical allergens has been studied in mice. Inhalation exposure of BALB/c mice to atmospheres containing approximately 5 mg/m3 of the respiratory allergen trimellitic anhydride (TMA) resulted in the appearance of both serum IgG and IgE anti-hapten antibody. IgE anti-TMA was first detectable 2-3 weeks following the initiation of exposure and was still present at 6 weeks. Under the same conditions of exposure, 2,4-dinitrochlorobenzene (DNCB), a contact allergen which apparently lacks the capacity for respiratory sensitization, failed to elicit detectable amounts of anti-dinitrophenol (DNP) antibody. Exposure to increased concentrations of atmospheric DNCB (15 mg/m3) did, however, result in an IgG anti-DNP response but not in IgE antibody. These data demonstrate firstly, that atmospheres containing low molecular weight respiratory allergens can initiate specific IgE responses in mice, and secondly, that inhaled chemicals may differ in their ability to induce IgE antibody.

The development of the anti-phospholipase A2 antibody response in horses inoculated with venom for the production of polyvalent antisnake serum in Costa Rica

The development of antibody response against phospholipase A2 activity of Bothrops asper venom was studied in a group of adult and healthy horses used in the production of the polyvalent antivenom at the Instituto Clodomiro Picado. Simultaneously, the general condition of the animals during the immunization schedule was also studied. There was a great individual variability in the immune response, although most of the horses studied reached the highest neutralizing titer after injection of doses of venom of 30 mg and 50 mg. On the other hand, in horses that had been previously immunized and were infected for a second immunization, the highest antibody titer was observed 16-22 days after inoculation. There were only mild alterations in the general condition of the horses as a consequence of venom inoculation. However, local abscesses, fistulae and fibrosis were observed at the site of venom injection. On the basis of the conspicuous individual variability observed, it is proposed that the immune response in horses used in the production of antivenom must be evaluated on individual basis, instead of working with pools of serum samples.

A subclass IgG4-specific antigen-binding radioimmunoassay (RIA): Comparison between IgG and IgG4 antibodies to food and inhaled antigens in adult atopic dermatitis after desensitization treatment and during development of antibody responses in children

A liquid-phase, antigen-binding radioimmunoassay measuring subclass IgG4 antibody (ab) to allergens has been developed. This assay, which uses monoclonal anti-IgG4 to bind IgG4, allows direct comparison of class (IgG)- and subclass (IgG4)-specific ab levels. These assays used radiolabeled purified allergens, Der p I (Ag P 1) from the dust mite Dermatophagoides pteronyssinus, Lol p I (Rye 1), from ryegrass pollen, hen's egg ovalbumin, and β-lactoglobulin from cow's milk. We have investigated IgG4 abs in several clinical situations. The results confirm that IgG ab responses to both inhalants and food proteins unequivocally include IgG4 ab. On average, the proportion of IgG4 ab to these antigens is far higher than the contribution of IgG4 to total IgG. In patients with adult atopic dermatitis, levels of both class and subclass ab were higher than in control subjects; however, the ratio of IgG4:IgG varied widely in patients and control subjects. During desensitization treatment of patients with perennial rhinitis, levels of IgG4 ab to Der p I increased sharply, but there were also increases in the total IgG ab responses so that the precentage contribution of IgG4 was only moderately increased (mean values: before, 29%; after, 36%). In a prospective study of children from atopic families, IgG4 abs to food proteins were detectable as early as 3 months. IgG abs to hen's egg ovalbumin and β-lactoglobulin from cow's milk increased to a maximum at 3 years and declined by 5 years. However, specific IgG4 as a percentage of specific IgG increased progressively from a mean value of ∼15% at 6 months to ∼50% at 5 years of age. Overall, the results do not support a role for IgG4 in immediate skin reactivity as the sole blocking ab or in the production of allergic symptoms. However, given the known properties of the IgG4 subclass, changes in IgG4 abs to food allergens could well alter the impact of these proteins on young children.