Immunoglobulin G Subclass Deficiency is the Major Phenotype of Primary Immunodeficiency in a Korean Adult Cohort

Primary immunodeficiency disease (PID) is a rare disorder in adults. Most often, serious forms are detected during infancy or childhood. However, mild forms of PID may not be diagnosed until later in life, and some types of humoral immunodeficiency may occur in adulthood. The purpose of this study was to identify clinical features of PID in Korean adults. A retrospective study was performed on 55 adult patients who were diagnosed as PID between January 1998 and January 2009 at a single tertiary medical center in Korea. IgG subclass deficiency was the most common phenotype (67%, 37/55), followed by total IgG deficiency (20%, 11/55), IgM deficiency (7%, 4/55), common variable immunodeficiency (2%, 1/55), and X-linked agammaglobulinemia (2%, 1/55). IgG3 and IgG4 were the most affected subclasses. Upper and lower respiratory tract infections (76%) were the most frequently observed symptoms, followed by multiple site infection (11%), urinary tract infection, and colitis. Bronchial asthma, rhinitis, and several autoimmune diseases were common associated diseases. IgG and IgG subclass deficiency should be considered in adult patients presenting with recurrent upper and lower respiratory infections, particularly in those with respiratory allergies or autoimmune diseases.     

Adjuvants Influence the Immunoglobin Subclass Distribution of Immune Responses in Vivo

Mice were immunized against fluorescein isothiocyanate (FITC)-labelled human gamma globulin (HGG) in the absence or presence of different adjuvants. The immune response was assayed every other day with regard to both total Ig-secreting cells and FITC-specific plaque-forming cells (PFC). The adjuvants influenced the type of immune response induced to the same antigenic determinant. Thus, addition of Freund's complete (FCA) or incomplete (FIA) adjuvant preferentially led to the secretion of IgG1 PFC of an average high affinity. Most newly appearing IgG-secreting cells were also detected as FITC-specific PFC. The use of lipopolysaccharide (LPS) as an adjuvant resulted in the induction of both IgM and IgG, particularly of the IgG3 and IgG2b subclasses. However, these antibodies had relatively low affinity, and a large number of total IgG-secreting cells induced by LPS had no detectable FITC specificity. The FCA/FIA- and LPS-induced responses to FITC-HGG were additive when injected together, indicating that they act on distinct subpopulations of B lymphoid cells. The adjuvant response to LPS, but not the response to FCA/FIA, was totally absent in mice of the C3H/Hej strain, which are non-responders to the polyclonal activating properties of LPS. Finally, the response induced by FCA or FIA was T-cell-dependent and the LPS response T-cell-independent as assayed in nude mice.     

Subclass Distribution of IgA and IgG Antibodies Against Clq in Patients with Rheumatic Diseases

To obtain insight into the immunoregulatory mechanisms in patients with different rheumatic diseases, the occurrence and the subclass distribution of IgA and IgG antibodies against Clq (anti-ClqAb) was determined. In patients with systemic lupus erythaematosus (SLE) the highest frequency of increased serum levels of IgG anti-ClqAb were found, whereas IgA anti-ClqAb were predominantly present in patients with ankylosing spondylitis (AS) and patients with rheumatoid arthritis complicated by vasculitis (RV). In all the IgA anti-ClqAb positive AS and RV patients the antibody reactivity involved the IgAl subclass while the IgA2 subclass was found in 47% of the patients. Further characterization of the IgA anti-Clq binding activity in sera of AS patients revealed that both subclasses of IgA anti-ClqAb were predominantly polymeric; the binding of both IgA subclasses with solid phase CI q was inhibitable by aggregated fluid phase Clq; we found no delectable interference of rheumatoid factor in the test system for the measurement of IgA anti-ClqAb. In patients with SLE the IgG anti-ClqAb reactivity was mainly of the IgG2 and IgG3 subclass, whereas in the same patients the IgG anti-tetanus toxoid response was not restricted to these subclasses.
The predominance of IgG2 and IgG3 subclass of anti-ClqAb in sera of SLE patients, suggests a skewing of the anti-ClqAb response. The observation that the IgA anti-ClqAb of both subclasses is predominantly polymeric in nature and the notion that polymeric IgA is associated with activation of inflammation cascades, suggests that IgA anti-ClqAb may contribute to tissue damage.     

Immunoglobulin Class and Subclass Distribution of Dextran-Reactive Antibodies in Human Reactors and Non Reactors to Clinical Dextran

The red cell-linked antigen-antiglobulin reaction (RCLAAR) with stearoyldextran-coated erythrocytes was used to characterize the immunoglobulin (Ig) classes and IgG subclasses of dextran reactive antibodies (DRA) in 27 dextran reactors (DR) and 96 on reactors (DNR). High titres of dextran reactive IgG were regularly found in sera of patients with severe dextran-induced anaphylactoid/anaphylactic reactions (DIAR) prior to the infusion. In four lethal cases IgG antibodies were found to be in the highest titre range of 16,384 to 32,768. In addition, high IgA and IgM titres were also in severe DIAR. DNR had much lower titres of dextran reactive antibodies of IgG, IgM and IgA classes and IgD antibody was absent in both groups. Dextran reactive IgE antibodies were not demonstrable in DR. Dextran reactive IgG2, IgG3, IgG4 and IgG1 (indirect measurement) were demonstrated in both DR and FNR. Dextran infusion caused variable neutralization in all Ig classes and IgG subclasses, but the contribution of IgG2 was considered most important because of its high titres and most pronounced neutralization in severe DIAR. It is concluded that DRA mainly of the IgG class, play a critical pathogenic role in the induction of severe DIAR, which accordingly is classified as immune complex (Type III) anaphylaxis. The method of RCLAAR allows to delineate a risk group of about 2% of potential reactors.     

Immunity in Experimental Salmonellosis II. Basis for the Avirulence and Protective Capacity of gal E Mutants of Salmonella typhimurium

Salmonella typhimurium strains which are deficient in uridine diphosphate (UDP)-galactose-4-epimerase (gal E mutants) owe their outstanding protective capacity when used as live vaccine to the fact that when galactose is supplied exogenously, such as occurs in vivo, smooth cell wall lipopolysaccharides are synthesized. The mutants lose most of their protective capacity when this phenotypic curing is prevented by a second mutation of the kind found in strains LT₂M₁A (deficient in galactokinase) or E₃₂ (deficient in UDP-galactose-lipopolysaccharide transferase). Despite such phenotypic reversion, the gal E mutants are rendered avirulent as a result of galactose-induced bacteriolysis. Secondary mutants have been isolated which differ from each other with respect to the extent of galactose-induced lysis. The differences in galactose sensitivity are attributable to different activities of the other Leoloir pathway enzymes, namely, galactokinase and galactose-1-phosphate-uridyl transferase. The influence of these enzymes on lipopolysaccharide composition and galactose sensitivity and thus on virulence and immunogenicity of gal E mutants has been studied.     

Immunoglobulin G Subclass Responses to Recombinant Em18 in the Follow-Up of Patients with Alveolar Echinococcosis in Different Clinical Stages

In this study, we compared the sequential responses of immunoglobulin G (IgG) subclasses to the diagnostic antigen Em18 in sera from patients with alveolar echinococcosis. A total of 225 sera from 36 patients at different clinical stages according to the WHO-PNM staging system were tested. The antibody responses were measured for cohorts with resected and unresected parasitic lesions by enzyme-linked immunosorbent assays (ELISA). Total IgG and, to a lesser extent, IgG4 antibody levels against Em18 correlated with all PNM stages before treatment, whereas levels of IgG2 were low and IgG3 was undetectable. Antibody kinetics, however, depended on the treatment rather than on the PNM stage. For some patients, after curative surgery, IgG1 antibodies dropped below the cutoff earlier than other antibodies, followed by total IgG and IgG4 within 18 months. For some patients with recurrences after surgery, IgG1 and IgG4 reappeared, whereas patients with unresectable lesions but stable disease showed steady declines in the levels of all antibodies, and IgG1 became undetectable in some patients. Additional testing of IgE responses to Em18 showed constantly low levels at all stages and in all cohorts.Alveolar echinococcosis (AE) is caused by the vesicular larval stage of the fox tapeworm Echinococcus multilocularis. The helminth causes dangerous infections characterized by infiltrative growth of the larvae in the livers of natural intermediate hosts such as rodents, and rarely in humans. Metastasis formation may also occur. AE is staged according to the World Health Organization (WHO)-PNM (P, parasitic mass in the liver; N, involvement of neighboring organs; M, metastasis) system (10). Radical resection of parasitic lesions is the preferred treatment (1), but most patients are inoperable at the time of diagnosis (5, 13). In a recent serological study, immunoglobulin G (IgG) antibodies directed against Em18, Em10, and Em2plus antigen compositions showed a close relationship between the clinical status and the treatment of patients with AE (16). In direct comparison, antibodies against Em18 demonstrated the greatest dynamic changeability in all patients, cohorts, and PNM stages, irrespective of the individual treatment. Moreover, Em18 indices had shown the best correlation with the PNM stages prior to treatment. These results prompted us to further investigate the IgG subclass and additionally the IgE response against this diagnostic antigen in patients with either resected or unresectable parasitic lesions.     

Immunoglobulin G (IgG) Subclass Distribution and IgG1 Avidity of Antibodies in Human Immunodeficiency Virus-Infected Individuals after Revaccination with Tetanus Toxoid

In human immunodeficiency virus (HIV)-infected individuals the amount of antibodies formed after vaccination with T-cell-dependent recall antigens such as tetanus toxoid is proportional to the peripheral blood CD4⁺ T-lymphocyte counts. To investigate whether the immunoglobulin G (IgG) subclass distribution and avidity of the antibodies produced after vaccination are affected as well, we gave 13 HIV-infected adults with low CD4⁺ T-lymphocyte counts (<200 × 10⁶/liter; group I), 11 HIV-infected adults with intermediate CD4⁺ T-lymphocyte counts (≥200 × 10⁶/liter; group II), and 5 healthy controls booster immunizations with tetanus toxoid. The prevaccination antibody concentrations against tetanus toxoid were similar in the HIV-infected and healthy adults. After vaccination the total IgG and the IgG1 anti-tetanus toxoid antibody concentrations were significantly lower in group I than in group II and the controls. The avidity of the IgG1 anti-tetanus toxoid antibodies formed by HIV-infected adults was within the range for healthy controls, irrespective of their CD4⁺ T-lymphocyte counts.In human immunodeficiency virus (HIV)-infected individuals the amount of antibodies formed after vaccination with T-cell-dependent recall antigens, such as tetanus toxoid, is impaired in proportion to the number of CD4⁺ T cells and to the in vitro proliferative response of T lymphocytes to anti-CD3 monoclonal antibodies (7, 8). Protection against tetanus will depend on the total amount of antibodies, the subclass distribution, and the avidities of the antibodies that are formed. Avidity reflects the combined functional affinities of antibodies formed during a polyclonal humoral immune response and is considered to be a parameter for the efficacy of the antibodies at eliminating or neutralizing the antigen (12). The aim of the present study was to investigate whether, in addition to the concentration of antibodies, the subclass distribution and the avidity of the antibodies formed by HIV-infected individuals after booster vaccination are affected.(This study was presented in part at the 35th Annual Meeting of the Infectious Diseases Society of America, San Francisco, Calif., 13 to 16 September 1997.)     

The Influence of Intravenous Immunoglobulin Treatment on Maternal Immunity in Women With Unexplained Recurrent Miscarriage

PROBLEM: Recently the protective value of high-dose intravenous immunoglobulin (IVIG) in the treatment of unexplained recurrent miscarriage has been reported to be similar to that of conventional immunotherapy with paternal leukocytes. We examined the effect of IVIG treatment on the cellular and humoral level of maternal immunity to demonstrate the possible mechanism by which IVIG might act to prevent recurrence of pregnancy loss. METHOD: Eight patients were treated with a 20- to 25-g dose of IVIG every 2 to 3 wk during their first-trimester pregnancies. The development of anti-idiotypic autoantibodies against maternal T-cell receptors, maternal anti-paternal lymphocyte antibodies detected by flow cytometric crossmatch, and changes of maternal lymphocyte subpopulations were monitored before pregnancy and then weekly during IVIG treatment. RESULTS: Five of eight patients gave birth successfully after IVIG treatment given during the first trimester of pregnancy (success rate: 62.5%). Although we could not demonstrate a general immunological effect of IVIG on maternal immunity in vivo, a few significant changes of immunological parameters were found in some patients. CONCLUSION: Our results suggest that the effect of IVIG on maternal immunity is not a passive increase of blocking antibody including anti-HLA antibody or modification of maternal T-cell subsets but, more likely, a passive increase of anti-idiotypic antibody against anti-HLA antibody or soluble HLA antigens. However, whether the immunomodulating effect of IVIG is related to its possible mechanism to prevent abortion remains unestablished.     

Influence of Host Factors on Immunoglobulin G Concentration in Oral Fluid Specimens

The influence of host factors (tobacco use, dentition, bleeding gums, oral rinsing, nasal medications, and time since the last meal) on immunoglobulin G (IgG) concentration in oral fluids (OF) was determined by univariate and multivariate analysis. Significant differences in IgG concentration were found to be associated with human immunodeficiency virus (HIV) status (HIV antibody positive, +16.60 μg/ml, P = 0.0001), sex (female, +1.23 μg/ml, P = 0.004), dentition (+2.83 μg/ml, edentulous versus dentulous, P = 0.0001), bleeding gums (+6.35 μg/ml, P = 0.0001), and time since the last meal (+3.55 μg/ml, >6 h, P = 0.0001). These factors could impact diagnostic methods that rely on the immunoglobulin concentration in OF specimens.     

Protective Cellular Immunity Against Influenza Virus Induced by Plasmid Inoculation of Newborn Mice

Neonate organisms display an intrinsic disability to mount effective immune responses to infectious agents or conventional vaccines. Whereas low. doses of antigens trigger a suboptimal response, higher doses are frequently associated with tolerance induction. We investigated the ability of a plasmid-expressing nucleoprotein of influenza virus to prime a specific cellular immune response when administered to newborn mice. We found that persistent exposure to antigen following plasmid inoculation of neonates leads to a vigorous priming of specific CTLs rather than tolerance induction. The CTLs were cross-reactive against multiple strains of type A influenza viruses and produced IFNγ but no IL-4. The immunity triggered by plasmid inoculation of neonates was protective in terms of pulmonary virus clearance as well as survival rate following lethal challenge with influenza virus. Whereas the persistence of the plasmid at the site of injection was readily demonstrable in adult mice at 3 months after inoculation, mice immunized as newborns displayed no plasmid at 3 months and very little at 1 month after injection. Thus, DNA-based immunization of neonates may prove an effective and safe vaccination strategy for induction of cellular immunity against microbes that cause serious infectious diseases in the early period of life.     

Contribution of Serum Immunoglobulin Transudate to the Antibody Immune Status of Murine Intestinal Secretions: Influence of Different Sampling Procedures

Serum immunoglobulin transudation into the murine gut after intragastric immunization with the model antigen ovalbumin and cholera toxin adjuvant was investigated with regard to the mucosal sampling technique applied. The levels of serum-derived immunoglobulin A (IgA) turned out to be lowest in feces, intermediate in gut lavage fluid specimens, and highest in filter wick-collected samples. However, these levels did not exceed 2% of total and specific IgA in any mucosal sample type, except after the administration of very high antigen doses (≥1 mg of antigen per g of body weight), when transudation rates of up to 31% could be measured in filter wick-collected samples from individual animals. Luminal IgG was plasma transudate and/or bile borne and appeared to be reabsorbed at the mucosa to some extent.     

Comparison of Immunoglobulin G Subclass Concentrations in Severe Community-Acquired Pneumonia and Severe Pandemic 2009 Influenza A (H1N1) Infection

We compared immunoglobulin G (IgG) subclasses in patients with severe noninfluenza community-acquired pneumonia (CAP) to those in patients with severe pandemic 2009 influenza (H1N1) virus infection. Low IgG1 and IgG2 levels occurred often in the CAP group; however, H1N1 patients had lower IgG1 and IgG2 levels (5.4 versus 3.3 g/liter [P = 0.008] and 2.5 versus 1.2 g/liter [P < 0.001], respectively). Low IgG2 levels may be specifically linked to severe H1N1; however, it is not clear whether this association is related to H1N1 or to other features of severity.     

A Monoclonal Immunoglobulin G Antibody Directed against an Immunodominant Linear Epitope on the Ricin A Chain Confers Systemic and Mucosal Immunity to Ricin

Due to the potential use of ricin and other fast-acting toxins as agents of bioterrorism, there is an urgent need for the development of safe and effective antitoxin vaccines. A candidate ricin subunit vaccine (RiVax) consisting of a recombinant attenuated enzymatic A chain (RTA) has been shown to elicit protective antitoxin antibodies in mice and rabbits and is currently being tested in phase I human clinical trials. However, evaluation of the efficacy of this vaccine for humans is difficult for a number of reasons, including the fact that the key neutralizing B-cell epitopes on RTA have not been fully defined. Castelletti and colleagues (Clin. Exp. Immunol. 136:365-372, 2004) recently identified a linear epitope on RTA, spanning residues L161 to I175, as a primary target of serum antibodies derived from humans who had been treated with ricin immunotoxin. While affinity-purified polyclonal IgG antibodies against this region of RTA were capable of neutralizing ricin in vitro, their capacity to confer protection against ricin challenge in vivo was not determined. In this report, we describe the production and characterization of GD12, a murine monoclonal IgG1 antibody specifically directed against residues 163 to 174 (TLARSFIICIQM) of RTA. GD12 bound ricin holotoxin with high affinity (K_D [dissociation constant], 2.9 × 10⁻⁹ M) and neutralized it with a 50% inhibitory concentration of ∼0.25 μg/ml, as determined by a Vero cell-based cytotoxicity assay. Passive administration of GD12 was sufficient to protect BALB/c mice against intraperitoneal and intragastric ricin challenges. These data are important in terms of vaccine development, since they firmly establish that preexisting serum antibodies directed against residues 161 to 175 on RTA are sufficient to confer both systemic and mucosal immunity to ricin. The potential of GD12 to serve as a therapeutic following ricin challenge was not explored in this study.Recent bioterrorism incidents in the United States and abroad have alerted public health officials to the need for vaccines against pathogens and toxins previously deemed to be of little concern (2, 25). The development and implementation of vaccines for biodefense and emerging infectious diseases are inherently challenging, because phase III clinical efficacy trials of candidate vaccines are generally not feasible or ethical. To address this issue, the Food and Drug Administration (FDA) has implemented the “two-animal rule,” which enables candidate vaccines to advance toward licensure based on efficacy studies performed with two or more relevant animal models (8, 49). For compliance with this FDA policy, the animal models must mimic the pathophysiology of human disease, and the defined end point(s) of the efficacy studies must correlate with the desired effects for humans. However, even well-established animal models cannot completely substitute for human studies. Therefore, whenever possible, specific correlates of protection against select agents and emerging infectious diseases should be established in humans, and surrogate assays should be developed that can be used to estimate immunity in vaccinated human populations (35).Ricin is a category B toxin, as classified by the Centers for Disease Control and Prevention (CDC). The toxin is naturally produced by the castor bean plant, Ricinus communis, which is cultivated on industrial levels around the world for the production of castor oil. Ricin constitutes up to 5% of the total dry weight of the castor bean and can be extracted from the mash through several simple enrichment steps. The toxin is a member of the so-called type II ribosome-inactivating proteins (RIPs); it consists of two subunits, RTA and RTB, each with a molecular mass of approximately 30,000 Da (31, 47). RTA is an RNA N-glycosidase whose substrate is a conserved adenine residue within the so-called sarcin/ricin loop of eukaryotic 28S rRNA. Ribosome progression is arrested upon cleavage of this residue by RTA (9). RTB is a bivalent lectin with specificity for glycoproteins and glycolipids containing β(1-3)-linked galactose and N-acetylgalactosamine residues (4). RTB mediates the attachment and internalization of ricin into host cells and facilitates retrograde transport of the toxin to the Golgi apparatus and endoplasmic reticulum (ER) (21, 38). Ricin in semipurified or purified form is extremely toxic to humans following injection, inhalation, or ingestion (3) and has been used as an agent of bioterrorism. Ricin was weaponized by the United States and other countries during World War II (24, 48); it has been used in assassinations; and it was recently uncovered in a number of government facilities, including a South Carolina postal facility, and packed in envelopes delivered to offices of the U.S. Senate (12, 40).Because of the toxicity of ricin and the ease of its preparation, public health officials and defense agencies have made a concerted effort to develop a vaccine against it that could be administered to emergency first responders and military personnel (25). Although formaldehyde-treated ricin toxoid (RT) preparations are effective at eliciting protective immunity in rodents, they are not being considered for use in humans, because of concerns about residual toxicity (11). Therefore, the current emphasis is on the development of attenuated subunit vaccines (6, 16, 32, 45, 52). One of the most promising candidates is a recombinant derivative of RTA containing two point mutations: one in the enzymatic active site (Y80A) and the other in a residue (V76M) involved in eliciting vascular leak syndrome (42-45, 52). This vaccine, known by the trade name RiVax, is safe and immunogenic in mice and rabbits and, when administered intramuscularly, elicits serum antitoxin IgG antibodies capable of protecting animals against a systemic ricin challenge of 10 50% lethal doses (LD₅₀s) (42, 44). RiVax has also been shown to elicit an antibody response capable of protecting mice against both intragastric (i.g.) and aerosol challenges (45). Based on these animal studies, a pilot phase I clinical trial of RiVax was undertaken in 2006 (52). The trial consisted of three groups of five healthy volunteers injected at monthly intervals with 10, 33, or 100 μg of the vaccine. The results of this study revealed that RiVax was well tolerated and resulted in dose-dependent seroconversion (52).While RiVax was deemed safe and immunogenic, evaluation of the efficacy of this vaccine in humans remains challenging. For example, in the pilot phase I clinical trial noted above, there was no observed correlation between serum anti-RTA IgG titers and in vitro ricin-neutralizing activity (52). Specifically, two individuals with virtually identical serum anti-RTA IgG levels (4.73 ± 0.019 μg/ml versus 4.36 ± 0.16 μg/ml) had toxin-neutralizing titers that differed by >10-fold (1.4 ± 0 versus 0.13 ± 0.02). These data suggest that the polyclonal response to RTA consists of a mixture of neutralizing and nonneutralizing antibodies and that the ratio of the two types of antibodies can differ from individual to individual. This interpretation is supported by work from Maddaloni and colleagues, who identified both potent neutralizing monoclonal antibodies (MAbs) (e.g., RAC18) and a number of MAbs that bound to RTA with high avidity but failed to neutralize ricin in vitro or in vivo (23, 37). In fact, one MAb, designated RAC23, actually enhanced ricin toxicity in vivo. These data indicate that distinct neutralizing and nonneutralizing B-cell epitopes exist on RTA.Castelletti and colleagues recently identified a linear B-cell epitope (L161 to I175) on RTA recognized by serum antibodies from 15 Hodgkin''s lymphoma patients who had received ricin immunotoxin therapy (7). In two of the serum samples tested, the majority of the antiricin specific antibodies were directed against this epitope. Affinity-purified serum antipeptide IgG was capable of neutralizing ricin in vitro, suggesting that this epitope is an important target of anti-RTA neutralizing antibodies in vivo. However, the possibility that the observed activity was due to a minor contaminating population of antibodies directed against a similar or closely situated epitope cannot be excluded. Moreover, Castelletti and colleagues did not examine whether antibodies directed against L161 to I175 were actually capable of neutralizing ricin in an animal model of ricin intoxication.In an effort to identify the epitopes on ricin that are the key targets of neutralizing antibodies in vivo with the goal of better understanding vaccine-induced immunity to ricin, we have produced and characterized a murine IgG1 MAb, referred to as GD12, that is specifically directed against the linear B-cell epitope on RTA described by Castelletti and colleagues as being immunodominant in humans. GD12 neutralized ricin with a 50% inhibitory concentration (IC₅₀) of ∼0.25 μg/ml, as determined by a Vero cell-based cytotoxicity assay. More importantly, passive administration of GD12 to mice was sufficient to protect the animals against both systemic (i.e., intraperitoneal [i.p.]) and mucosal (i.e., intragastric) ricin challenge, underscoring the importance of the epitope spanning residues 161 to 175 on RTA as a key target of neutralizing antibodies in vivo. However, because these studies focused on vaccine development, rather than on therapeutic applications of GD12, this MAb was not examined for the ability to rescue animals following toxin exposure.     

Immunity in Experimental Murine Filariasis: Roles of T and B Cells Revisited

We have reevaluated the contributions of T and B cells in Brugia malayi infection by utilizing knockout mice on a uniform background (C57BL/6J). We find that B-cell-deficient mice are more permissive to infection than T-cell-deficient mice.     

Biological Activities of Rabbit Immunoglobulin M and Immunoglobulin G Antibodies to Pseudomonas aeruginosa

Immunoglobulin (Ig)M and IgG antibodies, prepared in the rabbit against the protective antigen of Pseudomonas aeruginosa P4, were compared as to their biological activities in vitro and in vivo. In vitro biological activities of these antibodies were determined by passive hemagglutination, bactericidal, and opsonophagocytic tests. Increased effectiveness of IgM over IgG on a molar basis was demonstrated in all of these tests. However, in mouse protection tests, in which the purified globulins were injected intraperitoneally 4 hr prior to challenge with P. aeruginosa suspended in hog gastric mucin, IgM anticapsular antibody was found to be less effective than IgG antibody. The exact mechanism whereby IgG antibody exerts more protective ability than IgM antibody is still unknown. We present evidence to suggest that the difference in activity between the two classes of antibody is due to the ability of the IgG antibody to enter the bloodstream more rapidly than the IgM antibody and also to the ability of IgG to diffuse rapidly through the tissues of the organs.     

Similar Ability of FbaA with M Protein to Elicit Protective Immunity Against Group A Streptococcus Challenge in Mice

Group A streptococcus （GAS）, an important human pathogen, can cause various kinds of infections including superficial infections and potentially lethal infections, and the search for an effective vaccine to prevent GAS infections has been ongoing for many years. This paper compares the immunogenicity and immunoprotection of FbaA （an Fn-binding protein expressed on the surface of GAS） with that of M protein, the best immunogen of GAS. Assay for immune response showed that FbaA, similar to M protein, could induce protein-specific high IgG titer in BALB/c mice. Furthermore, following GAS challenge, the mice immunized with FbaA showed the same protective rate as those with M protein. These results indicate that FbaA is similar in ability to M protein in inducing protective immunity against GAS challenge in mice. Cellular ＆ Molecular Immunology.     

Characterization of Human Immunoglobulin (Ig) Isotype and IgG Subclass Response to Bartonella henselae Infection

Serologic parameters of cat scratch disease (CSD) were evaluated by Western blot analysis. Sera from patients with serologically confirmed CSD antigen were screened for immunoglobulin (Ig) isotype-specific as well as IgG subclass-specific reactivity against Bartonella henselae whole-cell antigen. Bartonella-negative control sera were used to determine baseline antibody activity. Heterogeneous B. henselae-specific IgG reactivity with numerous protein bands, ranging from >150 to <17 kDa, was observed. Though individual banding patterns were variable, one approximately 83-kDa B. henselae protein (Bh83) was immunoreactive with all CSD sera tested, suggesting it is a conserved antigen during infection. Bh83 was not recognized by reference human antisera against Rickettsia rickettsii, Chlamydia group positive, Treponema pallidum, Orientia tsutsugamushi, Fransciscella tularensis, Ehrlichia chaffeensis, Mycoplasma pneumoniae, and Escherichia coli, although other cross-reactive proteins were evident. Significantly, CSD sera failed to recognize the 83-kDa protein when tested against Bartonella quintana antigen, though sera from B. quintana-infected patients did react to Bh83. This cross-reactivity suggests epitope conservation during infection with B. henselae or B. quintana. Western blot analysis further revealed similar banding patterns when B. henselae was reacted against the Ig isotypes IgG and IgG₁ and both secretory and alpha chains of IgA. Neither IgM nor IgE reacted significantly to Bartonella antigen by our Western blot analysis. Dissection of the antibody response at the IgG subclass level indicated that prominent antigen recognition was limited to IgG₁. These observations provide insight into induced immunity during CSD and provide evidence for conserved epitope expression during infection with B. henselae or B. quintana.

The spectrum of human disease and pathologic syndromes observed to be associated with Bartonella henselae, an alpha-2 proteobacterium, has been progressively expanding since its identification in 1992 (18, 27). Granulomatous and vasculoproliferative diseases stemming from this emerging pathogen have since been described in both immunosuppressed and immunocompetent patients. Implicated in the etiology of cutaneous bacillary angiomatosis, bacillary hepatic peliosis and its parenchymal variant, endocarditis, and fever with persistent bacteremia (2, 9, 10, 12, 23, 24, 28), B. henselae is most notably recognized for its role as the primary etiologic agent of cat scratch disease (CSD) (5, 14). Afflicting an estimated 24,000 persons in the United States annually (8), CSD is characterized by a broad range of clinical symptoms manifested in varying degrees of severity depending largely on the immune status of the host. Infected patients present with subacute regional lymphadenopathy after inoculation, low-grade fever, anorexia, and malaise. Such manifestations are typically self-limiting and resolve untreated within several weeks in the immunocompetent host. It has become clear, though, that individuals with a depressed cellular immune response succumb to more-severe, atypical manifestations of CSD, including systemic complications of multiorgan involvement, particularly of the spleen and liver, and involvement of the central nervous system (2, 21, 28). Although B. henselae is a cause of human disease with a wide spectrum of severity, little is known regarding pathogenicity and immunity induced during infection.B. henselae is a fastidious, gram-negative bacillus that may require an incubation period as long as 5 weeks to culture axenically. Consequently, serologic methods, such as indirect fluorescent-antibody assay (IFA) and enzyme immunoassay (EIA), have been the most-practical and least-invasive means of clinical diagnosis (3, 19). Widely accepted as a diagnostic assay, IFA is routinely used to confirm B. henselae infection (4). However, when the whole bacterial cell antigen is used, IFA is unable to differentiate species-specific serologic reactivity from cross-reactivity with other antigens of phylogenetic proximity, namely, Bartonella quintana (4, 11). Modifications to improve the efficacy of serologic detection methods are pending a more-comprehensive understanding of the factors influencing both the pathogenesis of infection due to B. henselae and the evoked human immune response.The purpose of this study was to dissect the humoral immune response to B. henselae antigen in patients with clinically and laboratory-diagnosed CSD (positive by IFA) by Western blot analysis. In evaluation of the B. henselae proteins recognized following infection, an 83-kDa immunodominant protein was identified that was recognized by all seropositive patient samples tested. Furthermore, we have provided an in-depth characterization of the immunoglobulin (Ig) isotype and IgG subclass response in CSD patients. The findings, which elucidate serologic responses to B. henselae infection, provide insight into the immunity induced by this pathogen.(This work was presented in part at the 13th Sesqui-Annual Meeting of the American Society for Rickettsiology [abstract 14], September 1997, Champion, Pa.)