Molecular and idiotypic analyses of the antibody response to Cryptococcus neoformans glucuronoxylomannan-protein conjugate vaccine in autoimmune and nonautoimmune mice (original) (raw)
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Journal of Experimental Medicine, 1993
The molecular characteristics of the humoral immune response to a serotype A Cr~tococcus neoformans infection were compared with the response elicited by a cryptococcal ghicuronoxylomannan-tetanus toxoid (GXM-TT) conjugate. Anticryptococcal monoclonal antibodies (mAbs) isolated from both responses have previously been shown to recognize the same antigenic determinant of cryptococcal GXM. Southern blot and sequence analyses indicate that the hybridomas isolated from each response arose from only a few precursor B cells. All the mAbs generated from the infected and GXM-TT conjugate-immunized mice utilize the same VH7183 family member: J.2/J.4, v~5.1, and J~l; mAbs generated by different B cells had complementarity-determining region Ys (CDR3s) composed of seven amino acids with a common sequence motif. Thus, the molecular analysis of these anticryptococcal mAb-producing hybridomas indicated that the response to both cryptococcal infection and conjugate immunization was oligoclonal and highly restricted with regard to immunoglobulin gene utilization. The GXM-TT conjugate primarily stimulated isotype switching and clonal proliferation, and did not result in hybridomas expressing additional immunoglobulin repertoires. The mAbs from both responses had a number of replacement mutations at the 5' end of CDR2 that appear to be the result of antigen-driven selection. Somatic mutation also resulted in altered epitope specificity for one mAb, 13F1. Passive administration of representative mAbs from different clones generated in response to the GXM-TT conjugate prolonged survival of lethally infected mice.
2004
Peptide mimotopes of capsular polysaccharides have been proposed as antigens for vaccines against encapsulated pathogens. In this study, we determined the antibody response to and efficacy of P13, a peptide mimetic of the Cryptococcus neoformans capsular polysaccharide glucuronoxylomannan (GXM), in mice that produce human antibodies. P13 was conjugated to tetanus toxoid (TT) or diphtheria toxoid (DT) and administered subcutaneously in Alhydrogel with or without CpG to mice transgenic for human immunoglobulin loci (XenoMouse mice) and expressing either immunoglobulin G2 (IgG2) (G2 mice) or IgG4 (G4 mice). Mice were vaccinated and revaccinated two or three times. The serum antibody responses of the mice to GXM and P13 and antibody idiotype expression were analyzed by an enzyme-linked immunosorbent assay. The results showed that both P13-TT and P13-DT were antigenic, inducing a mimetic response to P13 in both G2 and G4 mice, and immunogenic, inducing a mimotope response including VH3 (idiotype)-positive antibodies to GXM in G2 but not G4 mice. CpG led to higher titers of IgG to P13 and GXM in P13-TT-vaccinated G2 mice. C. neoformans challenge of P13-protein conjugate-vaccinated and control G2 mice induced anamnestic IgG- and VH3-positive responses to GXM and was associated with a significantly decreased risk of death and a prolongation of survival in P13-DT-vaccinated mice compared to phosphate-buffered saline-treated or protein carrier-vaccinated mice. These findings reveal that P13 elicited a human antibody response with VH3 expression in human immunoglobulin transgenic mice that has been observed for human antibodies to GXM and support the concept that peptide mimotope-based vaccines may hold promise for the treatment of C. neoformans infections.
Infection and Immunity, 2007
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 (Fc␥R), 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.
The Journal of Immunology, 2005
The protective efficacy of mAbs to Cryptococcus neoformans glucuronoxylomannan depends on Ab isotype. Previous studies in A/JCr and C57BL/6J mice showed relative protective efficacy of IgG1, IgG2a Ͼ Ͼ IgG3. However, we now report that in C57BL/ 6J ؋ 129/Sv mice, IgG3 is protective while IgG1 is not protective, with neither isotype being protective in 129/Sv mice. IgG1, IgG2a, and IgG3 had different effects on IFN-␥ expression in infected C57BL/6J ؋ 129/Sv mice. IgG1-treated C57BL/6J ؋ 129/Sv mice had significantly more pulmonary eosinophilia than IgG2a-and IgG3-treated C57BL/6J ؋ 129/Sv mice. C. neoformans infection and Ab administration had different effects on Fc␥RI, Fc␥RII, and Fc␥RIII expression in C57BL/6J, 129/Sv, and C57BL/6J ؋ 129/Sv mice. Our results indicate that the relative efficacy of Ab isotype function against C. neoformans is a function of the genetic background of the host and that IgG3-mediated protection in C57BL/6J ؋ 129/Sv mice was associated with lower levels of IFN-␥ and fewer pulmonary eosinophils. The dependence of isotype efficacy on host genetics underscores a previously unsuspected complex relationship between the cellular and humoral arms of the adaptive immune response.
Biomédica : revista del Instituto Nacional de Salud, 2005
Cryptococcus neoformans is a widely disseminated fungus shown to be responsible for infections in individuals with impaired cell mediated immunity, such as patients with human immunodeficiency virus (HIV). Cryptococcus neoformans has a polysaccharide capsule composed of glucuronoxylomannan (GXM), which acts as a major virulence factor and is considered to be a thymus independent type-2 antigen (TI-2). In the current study, the production kinetics were evaluated for IgG subclasses specific for GXM, and assessed with the cross reactive antibodies to Streptococcus pneumoniae polysaccharide. In addition, spleen B cell subpopulations were quantified in murine models of cryptococcosis with different susceptibilities to the infection. Antibodies were detected by ELISA at different time intervals after C. neoformans infection in moderately resistant (Balb/c), highly resistant (CBA/j) and susceptible (C57BL/6) mouse strains. B cells subpopulations were determined by flow cytometry analysis. ...
Infection and Immunity, 2004
Peptide mimotopes of capsular polysaccharides have been proposed as antigens for vaccines against encapsulated pathogens. In this study, we determined the antibody response to and efficacy of P13, a peptide mimetic of the Cryptococcus neoformans capsular polysaccharide glucuronoxylomannan (GXM), in mice that produce human antibodies. P13 was conjugated to tetanus toxoid (TT) or diphtheria toxoid (DT) and administered subcutaneously in Alhydrogel with or without CpG to mice transgenic for human immunoglobulin loci (XenoMouse mice) and expressing either immunoglobulin G2 (IgG2) (G2 mice) or IgG4 (G4 mice). Mice were vaccinated and revaccinated two or three times. The serum antibody responses of the mice to GXM and P13 and antibody idiotype expression were analyzed by an enzyme-linked immunosorbent assay. The results showed that both P13-TT and P13-DT were antigenic, inducing a mimetic response to P13 in both G2 and G4 mice, and immunogenic, inducing a mimotope response including V H 3 (idiotype)-positive antibodies to GXM in G2 but not G4 mice. CpG led to higher titers of IgG to P13 and GXM in P13-TT-vaccinated G2 mice. C. neoformans challenge of P13-protein conjugate-vaccinated and control G2 mice induced anamnestic IgG-and V H 3-positive responses to GXM and was associated with a significantly decreased risk of death and a prolongation of survival in P13-DT-vaccinated mice compared to phosphate-buffered saline-treated or protein carrier-vaccinated mice. These findings reveal that P13 elicited a human antibody response with V H 3 expression in human immunoglobulin transgenic mice that has been observed for human antibodies to GXM and support the concept that peptide mimotope-based vaccines may hold promise for the treatment of C. neoformans infections.
Infection and Immunity, 2001
Variable-region-identical mouse immunoglobulin G1 (IgG1), IgG2b, and IgG2a monoclonal antibodies to the capsular polysaccharide of Cryptococcus neoformans prolong the lives of mice infected with this fungus, while IgG3 is either not protective or enhances infection. CD4 ؉ T cells are required for IgG1-mediated protection, and CD8 ؉ T cells are required for IgG3-mediated enhancement. Gamma interferon is required for both effects. These findings revealed that T cells and cytokines play a role in the modulation of cryptococcal infection by antibodies and suggested that it was important to more fully define the cytokine requirements of each of the antibody isotypes. We therefore investigated the efficacy of passively administered variable-region-identical IgG1, IgG2a, IgG2b, and IgG3 monoclonal antibodies against intravenous infection with C. neoformans in mice genetically deficient in interleukin-12 (IL-12), IL-6, IL-4, or IL-10, as well as in the parental C57BL/6J strain. The relative inherent susceptibilities of these mouse strains to C. neoformans were as follows: IL-12 ؊/؊ > IL-6 ؊/؊ > C57BL/6J Ϸ IL-4 ؊/؊ Ͼ Ͼ IL-10 ؊/؊ . This is consistent with the notion that a Th1 response is necessary for natural immunity against cryptococcal infection. However, none of the IgG isotypes prolonged survival in IL-12 ؊/؊ , IL-6 ؊/؊ , or IL-4 ؊/؊ mice, and all isotypes significantly enhanced infection in IL-10 ؊/؊ mice. These results indicate that passive antibody-mediated protection against C. neoformans requires both Th1-and Th2-associated cytokines and reveal the complexity of the mechanisms through which antibodies modulate infection with this organism.