Age-associated differences in immunoglobulin G1 (IgG1) and IgG2 subclass antibodies to pneumococcal polysaccharides following vaccination.

Immunoglobulin G (IgG) subclass antibody responses to pneumococcal vaccines were determined for human subjects in four age groups. The ratios of IgG1/IgG2 antibody concentrations declined with advancing age for all five of the serotypes tested. Protein-conjugate vaccines elicited enhanced IgG antibody responses over plain polysaccharide vaccines in infants but not in adult groups.     

Human immunoglobulin G2 (IgG2) and IgG4, but not IgG1 or IgG3, protect mice against Cryptococcus neoformans infection

The encapsulated yeast Cryptococcus neoformans is a significant cause of meningitis and death in patients with AIDS. Some murine monoclonal antibodies (MAbs) against the glucuronoxylomannan (GXM) component of the C. neoformans capsular polysaccharide can prolong the lives of infected mice, while others have no effect or can even shorten survival. To date, no one has systematically compared the efficacies of antibodies with the same variable regions and different human constant regions with their unique combination of effector functions in providing protection against murine C. neoformans infection. In the present study, we examined the efficacies of anti-GXM MAbs of the four human immunoglobulin G (IgG) subclasses, which have identical variable regions but differ in their capacities to bind the three types of Fc receptors for IgG (FcgammaR), their abilities to activate complement, and their half-lives. IgG2 and IgG4 anti-GXM prolonged the lives of infected BALB/c mice, IgG3 anti-GXM did not affect animal survival, while mice treated with IgG1 anti-GXM died earlier than mice treated with phosphate-buffered saline or irrelevant isotype-matched MAbs. All MAbs decreased serum GXM in infected animals. Effector pathways traditionally believed to be important in defense against microbes, such as opsonophagocytosis and complement binding, negatively correlated with antibody efficacy. It is generally accepted that human IgG1 has the most favorable combination of effector functions for therapeutic use against infections. Therefore, our findings have significant implications for humanization of the mouse IgG1 currently in clinical trials for cryptococcal meningitis and for the design of antibody therapeutics to treat other infectious diseases as well.     

CpG oligodeoxynucleotides act as adjuvants for pneumococcal polysaccharide-protein conjugate vaccines and enhance antipolysaccharide immunoglobulin G2a (IgG2a) and IgG3 antibodies

Pneumococcal polysaccharide-protein conjugate vaccines elicit antipolysaccharide antibodies, but multiple doses are required to achieve protective antibody levels in children. In addition, the immunogenicity of experimental multivalent pneumococcal conjugate vaccines varies with different polysaccharide serotypes. One strategy to improve these vaccines is to incorporate an adjuvant to enhance their immunogenicity. Synthetic oligodeoxynucleotides containing unmethylated CpG motifs (CpG ODN) are adjuvants that promote T-cell and T-dependent antibody responses to protein antigens, but it has been unclear whether CpG ODN can enhance polysaccharide-specific antibody responses. The present studies demonstrate significant adjuvant activity of CpG ODN for antibody responses against Streptococcus pneumoniae polysaccharide types 19F and 6B induced by conjugates of 19F and 6B with the protein carrier CRM(197). BALB/c ByJ mice were injected with 19F-CRM(197) or 6B-CRM(197) with or without CpG ODN, and sera were tested for anti-19F or anti-6B antibodies by enzyme-linked immunosorbent assay. The polysaccharide-specific antibody response to 19F-CRM(197) alone was predominantly of the immunoglobulin G1 (IgG1) and IgM isotypes, but addition of CpG ODN markedly increased geometric mean titers of total anti-19F antibody (23-fold), anti-19F IgG2a (26-fold), and anti-19F IgG3 (>246-fold). The polysaccharide-specific antibody response to 6B-CRM(197) alone consisted only of IgM, but addition of CpG ODN induced high titers of anti-6B IgG1 (>78-fold increase), anti-6B IgG2a (>54-fold increase), and anti-6B IgG3 (>3,162-fold increase). CpG ODN also increased anti-CRM(197) IgG2a and IgG3. Adjuvant effects were not observed with control non-CpG ODN. Thus, CpG ODN significantly enhance antipolysaccharide IgG responses (especially IgG2a and IgG3) induced by these glycoconjugate vaccines.     

Placental malaria induces variant-specific antibodies of the cytophilic subtypes immunoglobulin G1 (IgG1) and IgG3 that correlate with adhesion inhibitory activity

Antibodies targeting variant antigens on the surfaces of chondroitin sulfate A (CSA)-binding malaria-infected erythrocytes have been linked to protection against the complications of malaria in pregnancy. We examined the isotype/subtype profiles of antibodies that bound to variant surface antigens expressed by CSA-adherent Plasmodium falciparum in pregnant Malawian women with and without histologically defined placental malaria. Women in their first pregnancy with placental malaria produced significantly greater amounts of immunoglobulin G1 (IgG1) and IgG3 reactive with surface antigens of malaria-infected erythrocytes than uninfected women of the same gravidity. IgG1 and IgG3 levels in infected and control women in later pregnancies were similar to those in infected women in their first pregnancy. Levels of IgG2 and IgG4 were similarly low in infected and uninfected women of all gravidities. IgM that bound to the surface of CSA-adherent P. falciparum occurred in all groups of women and malaria-na?ve controls. There was a significant correlation between IgG1 and IgG3 levels, indicating that women usually produced both subtypes. Levels of IgG1 and IgG3 correlated with the ability of serum or plasma to inhibit parasite adhesion to CSA. Taken together, these data suggest that IgG1 and IgG3 dominate the IgG response to placental-type variant surface antigens. They may function by blocking parasite adhesion to placental CSA, but given their cytophilic nature, they might also opsonize malaria-infected erythrocytes for interaction with Fc receptors on phagocytic cells.     

Enzyme-like immunosorbent assay (ELISA) for immunoglobulin G antibodies against insect venoms

IgG "blocking" antibodies were measured in patients receiving insect venom immunotherapy. The enzyme-linked immunosorbent assay (ELISA) described herein was found to be sensitive and reproducible. Results with ELISA correlated well with values obtained with a radioimmunoassay and with inhibition of the release of histamine from sensitive basophils. Also, specific antibody titers against phospholipase A and whole bee venom were correlated. Serial determinations of venom-specific IgG antibodies were made in 17 patients receiving Polistes wasp or bee venom immunotherapy. The majority of patients showed a rise in IgG antibodies, which peaked after administration of approximately 500 micrograms of venom. Only one out of 13 of these venom-treated patients had allergic symptoms after an insect sting while on maintenance therapy.     

High immunoglobulin G2 (IgG2) and low IgG4 levels are associated with human resistance to Plasmodium falciparum malaria

There is accumulating evidence for a role of immunoglobulin G (IgG) in protection against malarial infection and disease. Only IgG1 and IgG3 are considered cytophilic and protective against P. falciparum, whereas IgG2 and IgG4 were thought to be neither and even to block protective mechanisms. However, no clear pattern of association between isotypes and protection has so far emerged. We analyzed the isotypic distribution of the IgG response to conserved epitopes and P. falciparum blood-stage extract in 283 malaria-exposed individuals whose occurrence of infection and malaria attack had been monitored for about 1 year. Logistic regression analyses showed that, at the end of the season of transmission, high levels of IgG2 to RESA and to MSP2 epitopes were associated with low risk of infection. Indeed, IgG2 is able to bind FcgammaRIIA in individuals possessing the H131 allele, and we showed that 70% of the study subjects had this allele. Also, high specific IgG4 levels were associated with an enhanced risk of infection and with a high risk of malaria attack. Moreover, specific IgG2 and IgG3 levels, as well as the IgG2/IgG4 and IgG3/IgG4 ratios, increased with the age of subjects, in parallel with the protection against infection and disease. IgG4 likely competes with cytophilic antibodies for antigen recognition and may therefore block cytotoxicity mediated by antibody-activated effector cells. In conclusion, these results favor a protective role of IgG3 and IgG2, which may activate effector cells through FcgammaRIIA, and provide evidence for a blocking role of IgG4 in malarial infection and disease.     

Fast dipstick dye immunoassay for detection of immunoglobulin G (IgG) and IgM antibodies of human toxoplasmosis

A dipstick dye immunoassay (DDIA) was developed to detect immunoglobulin G (IgG) or IgM antibodies of toxoplasmosis infection in humans. The assays employ a blue colloidal dye particles (D-1) conjugated to sheep anti-human IgG and rabbit anti-human IgM as the visualizing agents and a soluble antigen of tachyzoites of Toxoplasma gondii strain RH (TSA) as the detective antigen. The mixture of dye-labeled anti-human antibody-special human antibody was captured by TSA onto a nitrocellulose membrane dipstick by means of immunochromatography. The assays are rapid (the whole test can be completed within 15 min), simple, and cheap, and they don't require any equipment. They are sensitive and specific for the detection of anti-Toxoplasma IgG or IgM antibodies and generally agree closely with the results from the enzyme-linked immunosorbent assay. The assays are especially suitable for field applications.     

Detection of immunoglobulin G (IgG) and IgM antibodies to Toxoplasma gondii: evaluation of four commercial immunoassay systems.

A comparative evaluation of the following commercial immunoassays for the determination of antibodies to Toxoplasma gondii was performed: Behring Diagnostics OPUS Toxo G and Toxo M, Abbott Diagnostics IMX Toxo-IgG 2.0 and Toxo-IgM, Sanofi Diagnostics Pasteur Platelia Toxo IgG and Toxo IgM, and bioMérieux Vitek VIDAS Toxo IgG and IgM. Of 676 specimens that were tested for Toxoplasma-specific immunoglobulin G (IgG) antibodies, 26% were reactive by all methods while 8% displayed some discrepancy. Of 718 specimens that were tested for Toxoplasma-specific IgM antibodies, 3% were reactive by all methods while 10% displayed some discrepancy. Analysis of discrepant specimens revealed performance shortcomings with all IgM-specific assays. The impact of such shortcomings is magnified in a population with a low prevalence of toxoplasmosis.     

Individual contributions of the human metapneumovirus F, G, and SH surface glycoproteins to the induction of neutralizing antibodies and protective immunity

We evaluated the individual contributions of the three surface glycoproteins of human metapneumovirus (HMPV), namely the fusion F, attachment G, and small hydrophobic SH proteins, to the induction of serum HMPV-binding antibodies, serum HMPV-neutralizing antibodies, and protective immunity. Using reverse genetics, each HMPV protein was expressed individually from an added gene in recombinant human parainfluenza virus type 1 (rHPIV1) and used to infect hamsters once or twice by the intranasal route. The F protein was highly immunogenic and protective, whereas G and SH were only weakly or negligibly immunogenic and protective, respectively. Thus, in contrast to other paramyxoviruses, the HMPV attachment G protein is not a major neutralization or protective antigen. Also, although the SH protein of HMPV is a virion protein that is much larger than its counterparts in previously studied paramyxoviruses, it does not appear to be a significant neutralization or protective antigen.     

Comparative role of immunoglobulin A in protective immunity against the Bordetellae

The genus Bordetella includes a group of closely related mammalian pathogens that cause a variety of respiratory diseases in a long list of animals (B. bronchiseptica) and whooping cough in humans (B. pertussis and B. parapertussis). While past research has examined how these pathogens are eliminated from the lower respiratory tract, the host factors that control and/or clear the bordetellae from the upper respiratory tract remain unclear. We hypothesized that immunoglobulin A (IgA), the predominant mucosal antibody isotype, would have a protective role against these mucosal pathogens. IgA(-/-) mice were indistinguishable from wild-type mice in their control and clearance of B. pertussis or B. parapertussis, suggesting that IgA is not crucial to immunity to these organisms. However, na?ve and convalescent IgA(-/-) mice were defective in reducing the numbers of B. bronchiseptica in the upper respiratory tract compared to wild-type controls. Passively transferred serum from convalescent IgA(-/-) mice was not as effective as serum from convalescent wild-type mice in clearing this pathogen from the tracheae of naive recipient mice. IgA induced by B. bronchiseptica infection predominantly recognized lipopolysaccharide-containing O-antigen, and antibodies against O-antigen were important to bacterial clearance from the trachea. Since an IgA response contributes to the control of B. bronchiseptica infection of the upper respiratory tract, immunization strategies aimed at inducing B. bronchiseptica-specific IgA may be beneficial to preventing the spread of this bacterium among domestic animal populations.     

Protection against candidiasis by an immunoglobulin G3 (IgG3) monoclonal antibody specific for the same mannotriose as an IgM protective antibody

We previously reported that a liposome-mannan vaccine (L-mann) of Candida albicans induces production of mouse antibodies that protect against disseminated candidiasis and vaginal infection. Immunoglobulin M (IgM) monoclonal antibody (MAb) B6.1, specific for a C. albicans cell surface beta-1,2-mannotriose, protects mice against both infections. Another IgM MAb, termed B6, which is specific for a different cell surface mannan epitope, does not protect against disseminated candidiasis. The B6.1 epitope is displayed homogeneously over the entire cell surface, compared to a patchy distribution of the B6 epitope. To determine if protection is restricted to an IgM class of antibody, we tested an IgG antibody. MAb C3.1 was obtained from L-mann-immunized mice. By results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis, capture enzyme-linked immunosorbent assay, and immunodiffusion tests, MAb C3.1 is an IgG3 isotype. By epitope inhibition assays, we determined that MAb C3.1 is specific for same mannotriose as MAb B6. 1. As expected by the results of the inhibition assays, immunofluorescence microscopy showed that the C3.1 epitope is distributed on the yeast cell surface in a pattern identical to that of the B6.1 epitope. Kidney CFU and mean survival times of infected mice pretreated with MAb C3.1 indicated that the antibody enhanced resistance of mice against disseminated candidiasis. Mice in pseudoestrus that were given MAb C3.1 prior to vaginal infection developed fewer vaginal Candida CFU than control animals that received buffered saline instead of the antibody. The finding that an IgG3 antibody is protective is consistent with our hypothesis that epitope specificity and complement activation are related to the ability of an antibody to protect against candidiasis.     

Deficiency in immunoglobulin G2 antibodies against staphylococcal enterotoxin C1 defines a subgroup of patients with atopic dermatitis

Background and aim Atopic dermatitis (AD) is a common chronic inflammatory skin disease often accompanied by cutaneous Staphylococcus aureus colonization and, in this regard, especially complicated by the presence of superantigen‐producing strains. Because IgG antibodies comprise an important defence mechanism of the adaptive immune system against bacteria, it was investigated whether AD patients have an abnormal pattern or distribution of superantigen‐specific IgG subclass antibodies in association with disease severity and activity. Methods Staphylococcal enterotoxin B (SEB) and staphylococcal enterotoxin C1 (SEC1) specific IgG antibody subclasses were assessed in n=89 adult AD patients with mild to severe disease activity as determined by the SCORAD score and in n=28 healthy age‐matched controls. Results were correlated with the current status of bacterial skin colonization and severity score. Results Thirty‐eight per cent of the AD patients showed a selective deficiency in IgG2 antibodies against SEC1 compared with only 14% in the control group. The absence of these antibodies was found in both currently colonized and non‐colonized AD patients and was associated with a severe phenotype (SCORAD more than 40 points in two‐thirds of the deficient patients). However, these patients had normal production levels of IgG2 antibodies against pneumococcal capsular polysaccharide (PCP) and SEB, but higher IgG1 and IgG4 titres against SEC1. Except for elevated total IgG1, total IgG subclass levels were normal in this AD subgroup. Yet, peripheral blood mononuclear cells (PBMCs) derived from these patients clearly produced IL‐4 and IL‐5 upon SEC1 re‐stimulation whereas PBMCs from those providing SEC1‐specific IgG2 antibodies failed in the production of these cytokines. Conclusion A subgroup of AD patients suffers from a selective deficiency to produce anti‐SEC1 IgG2 antibodies. This patient group is characterized by a severe AD phenotype.     

Monoclonal antibodies against IgG allotypes G1m(z), G1m(a), G1m(f), G3m(b1/u) and G3m(g1): their usefulness in HAI and capture ELISA

Monoclonal antibodies (McAbs) were produced against the IgG allotypes G1m(z), G1m(a), G1m(f), G3m(b1/u) and G3m(g1). Four out of the six McAbs described in this paper showed in the haemagglutination assay cross-reactivity with some or all IgG-coated cell samples. In the haemagglutination inhibition assay, all six McAbs are useful as typing reagent for the above allotypes. In this assay, two of the McAbs show two different specificities, which depend on the Ig-coated cell sample used. Five McAbs are useful for allotyping in a capture ELISA. The results with four of these are promising for the development of a quantitative determination of Gm allotypes.     

Biased immunoglobulin G (IgG) subclass production in a case of hyper-IgM syndrome

Hyper-immunoglobulin M (IgM) syndrome (HIGM) is a rare heterogeneous primary immune deficiency. We describe a patient with HIGM characterized by skewed production of serum IgG subclasses and normal somatic hypermutation. This case may represent a subgroup of HIGM type 4 that is characterized by a biased switching to the V-region proximal constant regions.     

流感病毒RNA聚合酶蛋白PB1在小鼠中可诱导亚型间交叉免疫保护

目的探索流感病毒RNA聚合酶PB2和PB1亚基作为实验性流感疫苗候选抗原的可能性.方法以复制型质粒（pSCA）为载体分别构建表达甲1型和甲3型流感PB2和PB1的复制型DNA疫苗,免疫小鼠后分别用甲1型流感病毒（A/PR/8/34）进行鼻腔攻击,观察针对不同亚型流感病毒的复制型DNA疫苗的免疫保护效果.结果本实验所构建的复制型DNA疫苗在真核细胞中均可表达外源基因;本实验采用的复制型质粒载体（pSCA）与传统质粒载体（pcDNA3）在诱导小鼠产生抗体方面无差异,并且都诱导了偏向TH1类的免疫反应;表达甲1型和甲3型流感PB1基因的复制型DNA疫苗均可保护小鼠抵御甲1型流感病毒（A/PR/8/34）的攻击.结论表达甲型流感病毒PB1的复制型DNA疫苗能保护小鼠抵御同型和异型流感病毒的攻击,本实验为流感疫苗研究提供新的候选抗原.     

Activation of natural killer T cells by alpha-galactosylceramide impairs DNA vaccine-induced protective immunity against Trypanosoma cruzi

Innate immunity as a first defense is indispensable for host survival against infectious agents. We examined the roles of natural killer (NK) T cells in defense against Trypanosoma cruzi infection. The T. cruzi parasitemia and survival of CD1d-deficient mice exhibited no differences compared to wild-type littermates. NK T-cell activation induced by administering alpha-galactosylceramide (alpha-GalCer) to T. cruzi-infected mice significantly changed the parasitemia only in the late phase of infection and slightly improved survival when mice were infected intraperitoneally. The combined usage of alpha-GalCer and benznidazole, a commercially available drug for Chagas' disease, did not enhance the therapeutic efficacy of benznidazole. These results suggest that NK T cells do not play a pivotal role in resistance to T. cruzi infection. In addition, we found that the coadministration of alpha-GalCer with DNA vaccine impaired the induction of epitope-specific CD8(+) T cells and undermined the DNA vaccine-induced protective immunity against T. cruzi. Our results, in contrast to previous reports demonstrating the protective roles of NK T cells against other infectious agents, suggest that these cells might even exhibit adverse effects on vaccine-mediated protective immunity.     

IdeS, a highly specific immunoglobulin G (IgG)-cleaving enzyme from Streptococcus pyogenes, is inhibited by specific IgG antibodies generated during infection

IdeS, a recently discovered cysteine proteinase secreted by the important human pathogen Streptococcus pyogenes, interferes with phagocytic killing by specifically cleaving the heavy chain of immunoglobulin G. The fact that the enzyme targets one of the key molecules of the adapted immune response raised the question of whether an antibody response against IdeS could inhibit, i.e., neutralize, enzyme activity. Paired acute- and convalescent-phase serum samples from patients with pharyngotonsillitis (n = 10), bacteremia (n = 7), and erysipelas (n = 4) were analyzed. Antibodies with the ability to neutralize IdeS enzymatic activity were already found in two-thirds of acute-phase sera. However, patients who seroconverted to IdeS, in particular patients with pharyngotonsillitis and erysipelas, developed specific antibodies during convalescence with an increased capability to efficiently neutralize the enzymatic activity of IdeS. Also, the presence of neutralizing antibodies decreased the ability of IdeS to mediate bacterial survival in human immune blood. In patients with bacteremia, several acute-phase sera contained neutralizing antibodies, but no correlation was found to severity or outcome of invasive infections. Still, the fact that the human immune response targets the enzymatic activity of IdeS supports the view that the enzyme plays an important role during streptococcal infection.     

Interference of immunoglobulin G (IgG) antibodies in IgA antibody determinations of Chlamydia pneumoniae by microimmunofluorescence test.

In the microimmunofluorescence test for measuring immunoglobulin A (IgA) antibodies against Chlamydia pneumoniae, removal of interfering IgG antibodies made IgA antibody reactivity patterns in 952 serum samples easier to interpret, prozone effects disappeared, and titers increased, especially in the sera with high IgG titers. IgA rheumatoid factors did not interfere in the assay.     

Comparison of three commercially available peptide-based immunoglobulin G (IgG) and IgA assays to microimmunofluorescence assay for detection of Chlamydia trachomatis antibodies

Three commercially available, peptide-based enzyme-linked immunosorbent assay (ELISA) systems (Chlamydia trachomatis IgG and IgA EIA [CT-EIA; Labsystems OY, Helsinki, Finland], SeroCT IgG and IgA [SeroCT; Savyon Diagnostics Ltd., Ashdod, Israel], and Chlamydia trachomatis IgG and IgA pELISA [CT pELISA; Medac, Wedel, Germany]) were evaluated for the detection of serum immunoglobulin G (IgG) and IgA antibodies specific for Chlamydia trachomatis and compared to the "gold standard" assay, the microimmunofluorescence (MIF) assay. Serological responses were analyzed in 149 women aged 20 to 30 years. Cervical swabs obtained from these women were examined for C. trachomatis by PCR, and 43 were found to be positive. The overall seroprevalence rates detected by CT-EIA, SeroCT, CT pELISA, and the MIF assay were 42, 42, 35, and 39%, respectively, for IgG and 7, 7, 3, and 7%, respectively, for IgA. The IgG seroprevalence rates for the PCR-positive women were two to three times higher than those for the PCR-negative women, i.e., 72 versus 29%, 72 versus 29%, 47 versus 26%, and 74 versus 25% for CT-EIA, SeroCT, CT pELISA, and the MIF assay, respectively. After discrepancy analysis, the sensitivity, specificity, positive predictive value, and negative predictive value were calculated for the IgG assays; for CT-EIA they were 84.7, 98.6, 98.4, and 86.7%, respectively; for CT pELISA they were 71.4, 97.3, 96.2, and 78.3%, respectively; for SeroCT they were 84.7, 98.6, 98.4, and 86.3%, respectively; and for the MIF assay they were 79.2, 83.1, 98.3, and 83.1%, respectively. In conclusion, these peptide-based ELISA systems for the serological detection of C. trachomatis infection performed as well as the MIF assay. Since these tests are less time-consuming, less expensive, and easier to perform than the MIF assay, they might be useful in the serodiagnosis of chlamydial infection.     

Lack of the G2m(n) Allotype in IgG Subclass Deficiency, in IgG2 Deficiency Together with Lack of G1m(a) and G3m(g), and in IgG3 Deficiency Together with Lack of G1m(f) and G3m(b)

Lack of G2m(n) was demonstrated in both IgG2-deficient and IgG3-deficient Caucasian patients. Lack of G2m(n) or G2m(",") was found together with homozygosity for both G1m and G3m allotypes as the dominant finding, i.e. for IgG2-deficient patients together with G1m (f,f) and G3m(b,b), constituting the Gm(f,",b) phenotype, and for IgG3-deficient patients together with G1m(a,a) and G3m(g,g), constituting the Gm(a,",g) phenotype. The group with IgG2 deficiency and the selected patients with the Gm(f,",b) phenotype expressed characteristically very low or undetectable IgG4, significantly increased IgG3, and normal IgG1. The group with IgG3 deficiency and the selected patients with the phenotype Gm(a,",g) expressed instead normal IgG4 and nearly normal IgG2 and IgG1 levels. The lack of G2m(n) together with lack of one or the other of the alternative G1m genes and corresponding G3m genes give different IgG2 levels and different IgG subclass patterns. The frequency of G1m allotypes and corresponding G3m allotypes also deviated significantly when the IgG2 deficiency and IgG3 deficiency groups were compared with each other. Most IgG subclass-deficient patients are homozygous in the Gm system and lack genetic variants in the three IgG subclasses, IgG1, IgG2, and IgG3.