Role of Toll like receptors in the antibody response to encapsulated bacteria.

Encapsulated bacteria are major pathogens in humans. The capsular polysaccharides (PS) of these bacteria are T-independent type 2 antigens, are not processed by antigen presenting cells and do not induce T cell help. PS antigens are poor immunogens in children less than two years, the peak age incidence of encapsulated bacterial infection.

Carbohydrate moieties as vaccine candidates: targeting the sweet spot in the immune response.

Advances in the use of carbohydrates as vaccine candidates for the prevention of infectious and malignant diseases was the topic for a meeting in Rockville, MD, sponsored by the National Institute of Allergy and Infectious Diseases involving a diverse group of scientists. Participants included research scientists and clinicians from academia and industry, and representatives from the National Institutes of Health and US Food and Drug Administration. This workshop was the third in a series of meetings designed to address issues relating to the immune response to carbohydrate antigens and how this information is used in the development of vaccines.

IgG3 deficiency extends lifespan and attenuates progression of glomerulonephritis in MRL/lpr mice.

Background: Antibodies of the IgG3 subclass have been implicated in the pathogenesis of the spontaneous glomerulonephritis observed in mice of the MRL/MpJ-Tnfrsf6lpr (MRL/lpr) inbred strain which have been widely studied as a model of systemic lupus erythematosus We have produced IgG3-deficient (-/-) mice with the MRL/lpr genetic background to determine whether IgG3 antibodies are necessary for or at least contributory to MRL/lpr-associated nephritis.

Results: The gamma3 genotype (+/+ vs. +/- vs.

Outer membrane protein complex of Meningococcus enhances the antipolysaccharide antibody response to pneumococcal polysaccharide-CRM₁₉₇ conjugate vaccine.

Bacterial polysaccharides (PS) are T cell-independent antigens that do not induce immunologic memory and are poor immunogens in infants. Conjugate vaccines in which the PS is covalently linked to a carrier protein have enhanced immunogenicity that resembles that of T cell-dependent antigens. The Haemophilus influenzae type b (Hib) conjugate vaccine, which uses the outer membrane protein complex (OMPC) from meningococcus as a carrier protein, elicits protective levels of anti-capsular PS antibody (Ab) after a single dose, in contrast to other conjugate vaccines, which require multiple doses.

Antigen processing of glycoconjugate vaccines; the polysaccharide portion of the pneumococcal CRM(197) conjugate vaccine co-localizes with MHC II on the antigen processing cell surface.

Pneumococcal (Pn) polysaccharides (PS) are T-independent (TI) antigens and do not induce immunological memory or antibodies in infants. Conjugation of PnPS to the carrier protein CRM(197) induces PS-specific antibody in infants, and memory similar to T-dependent (Td) antigens. Conjugates have improved immunogenicity via antigen processing and presentation of carrier protein with MHC II and recruitment of T cell help, but the fate of the PS attached to the carrier is unknown.

Decreased expression of tumor necrosis factor family receptors involved in humoral immune responses in preterm neonates.

Neonates have an increased rate of infection with encapsulated bacteria compared with older children and adults because of diminished antibody responses to T-independent (TI) antigens such as bacterial polysaccharides. Because the interactions of tumor necrosis factor (TNF) family ligands BAFF and APRIL with the TNF family receptors (TNFRs) TACI, BCMA, and BAFF-R are crucial to TI antibody responses, we measured the expression of these receptors on adult and cord blood-derived term and preterm neonatal B cells. Preterm neonatal B cells expressed less TACI, BCMA, and BAFF-R compared with adult B cells and had significantly less proliferation compared with adult B cells after stimulation with human recombinant BAFF and anti-IgM in an assay in which TACI-Fc fusion protein inhibits B-cell proliferation.

A human anti-Pseudomonas aeruginosa serotype O6ad immunoglobulin G1 expressed in transgenic tobacco is capable of recruiting immune system effector function in vitro.

The production of a recombinant human IgG1 in transgenic tobacco was examined to determine whether a plant-derived antibody could recruit immune system effector function against a bacterial pathogen. A plant transformation vector was engineered to contain genes for a human kappa light chain and a human gamma-1 heavy chain with V(H) and V(L) sequences from a previously identified human IgG2 monoclonal antibody (MAb) that specifically binds to and opsonizes Pseudomonas aeruginosa serotype O6ad. Unique NcoI and NotI restriction sites were incorporated to flank these variable sequences, resulting in a plant transformation vector that could be engineered for expression of any other human IgG1 antibody, requiring only the substitution of other V(H) and V(L) antigen-binding coding sequences.

Therapies and vaccines for emerging bacterial infections: learning from methicillin-resistant Staphylococcus aureus.

Methicillin-resistant Staphylococcus aureus (MRSA) is an emerging bacterial infection worldwide, and community-acquired MRSA (CA-MRSA) infection, which has increased dramatically in frequency in many areas, is of particular clinical and public health concern. CA-MRSA outbreaks and severe infections have been reported more frequently in children, often manifesting in one of two distinct clinical syndromes, furunculosis or necrotizing pneumonia. This article outlines the molecular biology of MRSA, how molecular biology has contributed to the understanding of MRSA infections, current therapy and prevention of MRSA, and the prospects for a vaccine against S aureus.

Multi-valent human monoclonal antibody preparation against Pseudomonas aeruginosa derived from transgenic mice containing human immunoglobulin loci is protective against fatal pseudomonas sepsis caused by multiple serotypes.

Pseudomonas aeruginosa is a serious human pathogen in a variety of patient groups including those with burns, hospitalized in intensive care, cystic fibrosis and neutropenia. Since there is no vaccine available, passive antibody prophylaxis against protective epitopes is an alternative strategy to prevent P. aeruginosa infection.

Clearance of Citrobacter rodentium requires B cells but not secretory immunoglobulin A (IgA) or IgM antibodies.

Citrobacter rodentium, a murine model pathogen for human enteropathogenic Escherichia coli, predominantly colonizes the lumen and mucosal surface of the colon and cecum and causes crypt hyperplasia and mucosal inflammation. Mice infected with C. rodentium develop a secretory immunoglobulin A (IgA) response, but the role of B cells or secretory antibodies in host defense is unknown.

Haemophilus influenzae type b-outer membrane protein complex glycoconjugate vaccine induces cytokine production by engaging human toll-like receptor 2 (TLR2) and requires the presence of TLR2 for optimal immunogenicity.

Conjugate vaccines consisting of the capsular polysaccharide (PS) of Haemophilus influenzae type b (Hib) covalently linked to carrier proteins, unlike pure PS, are immunogenic in infants and have significantly reduced Hib infections in the United States, but require multiple doses to induce protective anti-PS Ab titers. Hib-meningococcal outer membrane protein complex (OMPC) conjugate vaccine, however, elicits protective anti-PS Ab titers after one dose. We found that OMPC and Hib-OMPC engaged human Toll-like receptor 2 (TLR2) expressed in human embryonic kidney (HEK) cells, inducing IL-8 production, and engaged mouse TLR2 on bone marrow-derived dendritic cells, inducing TNF release.

T-cell hybridomas from HLA-transgenic mice as tools for analysis of human antigen processing.

The study of antigen processing and presentation by human antigen presenting cells (APC) has been limited by difficulties of producing and maintaining human T-cell clones. Murine T-cell hybridomas have advantages for detecting specific peptide-MHC complexes on APC. Human antigen-specific immortalized T-cell lines have not been successfully produced.

A family cluster of five cases of group A streptococcal pneumonia.

A cluster of 5 family members, a mother and 4 children, were hospitalized for severe group A Streptococcus (GAS) pneumonia. Three family members had complications: sepsis (1), empyema (2), and a sterile parapneumonic effusion (1). Two additional family members had symptoms of upper respiratory tract infection, and 1 was hospitalized for these symptoms.

Antigen processing of the heptavalent pneumococcal conjugate vaccine carrier protein CRM(197) differs depending on the serotype of the attached polysaccharide.

The pneumococcal (Pn) conjugate vaccine includes seven different polysaccharides (PS) conjugated to CRM(197). Utilizing antigen-processing cells and a CRM(197)-specific mouse T-cell hybridoma, we found that the serotype of conjugated PnPS dramatically affected antigen processing of CRM(197). Unconjugated CRM(197) and serotype conjugates 14 and 18C were processed more efficiently.

Significant variation in serotype-specific immunogenicity of the seven-valent Streptococcus pneumoniae capsular polysaccharide-CRM197 conjugate vaccine occurs despite vigorous T cell help induced by the carrier protein.

Streptococcus pneumoniae capsular polysaccharides (PnPSs) induce protective antibodies but are T cell-independent type 2 antigens and are poorly immunogenic in infants. Conjugate vaccines of PnPSs linked to proteins like cross-reactive material (CRM(197)) increase PS antibody titer and elicit immunologic memory in infants. Despite being linked to an identical carrier protein, each PS component of the 7-valent PnPS-CRM(197) vaccine has different immunogenicity.

Enhanced immunogenicity of pneumococcal surface adhesin A by genetic fusion to cytokines and evaluation of protective immunity in mice.

Immunization of mice with pneumococcal surface adhesin A (PsaA) emulsified in complete Freund's adjuvant (CFA) provides protection against systemic infection with Streptococcus pneumoniae. Because the use of CFA is not acceptable in humans, we sought to develop alternative means of enhancing the immunogenicity of protein antigens of potential use in pneumococcal vaccines. We designed a series of genetic constructs in which coding sequences for PsaA were linked to sequences encoding either murine interleukin-2 (mIL-2), mIL-4, or two copies of an immunostimulatory nonapeptide derived from mIL-1beta.

Gamma 3 gene-disrupted mice selectively deficient in the dominant IgG subclass made to bacterial polysaccharides. II. Increased susceptibility to fatal pneumococcal sepsis due to absence of anti-polysaccharide IgG3 is corrected by induction of anti-polysaccharide IgG1.

Bacterial polysaccharides (PS) are type 2 T-independent Ags that elicit Abs restricted in isotype to IgM and predominantly IgG2 in humans and IgM, and IgG3 in mice. Humans with IgG2 subclass deficiency are susceptible to sinus and pulmonary infections with PS-encapsulated bacteria. We previously developed an IgG3-deficient mouse by disrupting the gamma3 H chain constant region gene via targeted mutagenesis.