Broadly protective vaccine for Staphylococcus aureus based on an in vivo-expressed antigen. (1/79)

Vaccines based on preferential expression of bacterial antigens during human infection have not been described. Staphylococcus aureus synthesized poly-N-succinyl beta-1-6 glucosamine (PNSG) as a surface polysaccharide during human and animal infection, but few strains expressed PNSG in vitro. All S. aureus strains examined carried genes for PNSG synthesis. Immunization protected mice against kidney infections and death from strains that produced little PNSG in vitro. Nonimmune infected animals made antibody to PNSG, but serial in vitro cultures of kidney isolates yielded mostly cells that did not produce PNSG. PNSG is a candidate for use in a vaccine to protect against S. aureus infection.  (+info)

Use of a Staphylococcus aureus conjugate vaccine in patients receiving hemodialysis. (2/79)

BACKGROUND: In patients with decreased resistance to infection, Staphylococcus aureus is a major cause of bacteremia and its complications. The capsular polysaccharides are essential for the pathogenesis of and immunity to S. aureus infection and are targets for vaccines. METHODS: In a double-blind trial involving patients with end-stage renal disease who were receiving hemodialysis, we evaluated the safety, immunogenicity, and efficacy of a vaccine with S. aureus type 5 and 8 capsular polysaccharides conjugated to nontoxic recombinant Pseudomonas aeruginosa exotoxin A. Between April 1998 and August 1999, 1804 adult patients at 73 hemodialysis centers were randomly assigned to receive a single intramuscular injection of either vaccine or saline. IgG antibodies to S. aureus type 5 and 8 capsular polysaccharides were measured for up to two years, and episodes of S. aureus bacteremia were recorded. Efficacy was estimated by comparing the incidence of S. aureus bacteremia in the patients who received the vaccine with the incidence in the control patients. RESULTS: Reactions to the vaccine were generally mild to moderate, and most resolved within two days. The capsular polysaccharides elicited an antibody response of at least 80 microg per milliliter (the estimated minimal level conferring protection) in 80 percent of patients for type 5 and in 75 percent of patients for type 8. The efficacy during weeks 3 to 54 was only 26 percent (P=0.23). However, between weeks 3 and 40 after vaccination, S. aureus bacteremia developed in 11 of 892 patients in the vaccine group who could be evaluated for bacteremia, as compared with 26 of 906 patients in the control group (estimate of efficacy, 57 percent; 95 percent confidence interval, 10 to 81 percent; nominal P=0.02). CONCLUSIONS: In patients receiving hemodialysis, a conjugate vaccine can confer partial immunity against S. aureus bacteremia for approximately 40 weeks, after which protection wanes as antibody levels decrease.  (+info)

Structural basis for abrogated binding between staphylococcal enterotoxin A superantigen vaccine and MHC-IIalpha. (3/79)

Staphylococcal enterotoxins (SEs) are superantigenic protein toxins responsible for a number of life-threatening diseases. The X-ray structure of a staphylococcal enterotoxin A (SEA) triple-mutant (L48R, D70R, and Y92A) vaccine reveals a cascade of structural rearrangements located in three loop regions essential for binding the alpha subunit of major histocompatibility complex class II (MHC-II) molecules. A comparison of hypothetical model complexes between SEA and the SEA triple mutant with MHC-II HLA-DR1 clearly shows disruption of key ionic and hydrophobic interactions necessary for forming the complex. Extensive dislocation of the disulfide loop in particular interferes with MHC-IIalpha binding. The triple-mutant structure provides new insights into the loss of superantigenicity and toxicity of an engineered superantigen and provides a basis for further design of enterotoxin vaccines.  (+info)

Immune protection against staphylococcal enterotoxin-induced toxic shock by vaccination with a Venezuelan equine encephalitis virus replicon. (4/79)

A candidate vaccine against staphylococcal enterotoxin B (SEB) was developed using a Venezuelan equine encephalitis (VEE) virus vector. This vaccine is composed of a self-replicating RNA, termed "replicon," containing the VEE nonstructural genes and cis-acting elements and a gene encoding mutagenized SEB (mSEB). Cotransfection of baby hamster kidney cells with the mSEB replicon and 2 helper RNA molecules resulted in the release of propagation-deficient mSEB-VEE replicon particles (mSEB-VRPs). Mice inoculated subcutaneously with mSEB-VRPs were protected (15 of 20 mice) from a challenge with 5 median lethal dose units of wild-type (wt) SEB. T cells from mice vaccinated with mSEB-VRP responded normally both in vitro to wt SEB and in recall response to the inactivated mSEB polypeptide. The profile of cytokines measured after challenge with wt SEB suggested that the mode of protection was predominantly Th1 dependent. Our results suggest that the VEE replicon is a practical and convenient model system for evaluating efficacy of vaccines for the control of bacterial diseases.  (+info)

Identification of in vivo expressed vaccine candidate antigens from Staphylococcus aureus. (5/79)

For the design of potent subunit vaccines, it is of paramount importance to identify all antigens immunologically recognized by a patient population infected with a pathogen. We have developed a rapid and efficient procedure to identify such commonly recognized antigens, and here we provide a comprehensive in vivo antigenic profile of Staphylococcus aureus, an important human pathogen. S. aureus peptides were displayed on the surface of Escherichia coli via fusion to one of two outer membrane proteins (LamB and FhuA) and probed with sera selected for high Ab titer and opsonic activity. A total of 60 antigenic proteins were identified, most of which are located or predicted to be located on the surface of the bacterium or secreted. The identification of these antigens and their reactivity with individual sera from patients and healthy individuals greatly facilitate the selection of promising vaccine candidates for further evaluation. This approach, which makes use of whole genome sequence information, has the potential to greatly accelerate and facilitate the formulation of novel vaccines and is applicable to any pathogen that induces Abs in humans and/or experimental animals.  (+info)

Functional selection of vaccine candidate peptides from Staphylococcus aureus whole-genome expression libraries in vitro. (6/79)

An in vitro protein selection method, ribosome display, has been applied to comprehensively identify and map the immunologically relevant proteins of the human pathogen Staphylococcus aureus. A library built up from genomic fragments of the virulent S. aureus COL strain (methicillin-resistant S. aureus) allowed us to screen all possible encoded peptides for immunoreactivity. As selective agents, human sera exhibiting a high antibody titer and opsonic activity against S. aureus were used, since these antibodies indicate the in vivo expression and immunoreactivity of the corresponding proteins. Identified clones cluster in distinct regions of 75 genes, most of them classifiable as secreted or surface-localized proteins, including previously identified virulence factors. In addition, 14 putative novel short open reading frames were identified and their immunoreactivity and in vivo mRNA expression were confirmed, underscoring the annotation-independent, true genomic nature of our approach. Evidence is provided that a large fraction of the identified peptides cannot be expressed in an in vivo-based surface display system. Thus, in vitro protein selection, not biased by the context of living entities, allows screening of genomic expression libraries with a large number of different ligands simultaneously. It is a powerful approach for fingerprinting the repertoire of immune reactive proteins serving as target candidates for active and passive vaccination against pathogens.  (+info)

RUNT DISEASE INDUCED IN NEONATAL MICE BY STERILE BACTERIAL VACCINES. (7/79)

A form of runt disease has been produced in neonatal CF-1 and ICR mice by the repeated injection of 10(9) washed, autoclaved, saline-suspended staphylococci or streptococci. The most severely affected animals showed a marked decrease in lymphoid tissues and resembled grossly and microscopically animals suffering from the classical runt or wasting disease described by others. The timing of the initial antigenic stimulation was of importance, and animals started on their course of injections at an age of 48 hours or older showed no effect. There was a considerable variation in the severity of the disease within litters and from one litter to another. This variation could not be ascribed to a difference in susceptibility between sexes, since both male and female mice were observed to runt under appropriate conditions. Germ-free ICR mice were much more resistant to the runting phenomenon than conventional animals of the same strain, but could be induced to runt by injection of the staphylococcal vaccine suspended in homologous antiserum. The relationship of the runting phenomenon described here and classical runt disease or runting by adrenal hormones is discussed.  (+info)

Comparative opsonic and protective activities of Staphylococcus aureus conjugate vaccines containing native or deacetylated Staphylococcal Poly-N-acetyl-beta-(1-6)-glucosamine. (8/79)

Staphylococcus aureus and Staphylococcus epidermidis both synthesize the surface polysaccharide poly-N-acetyl-beta-(1-6)-glucosamine (PNAG), which is produced in vitro with a high level (>90%) of the amino groups substituted by acetate. Here, we examined the role of the acetate substituents of PNAG in generating opsonic and protective antibodies. PNAG and a deacetylated form of the antigen (dPNAG; 15% acetylation) were conjugated to the carrier protein diphtheria toxoid (DT) and used to immunize animals. Mice responded in a dose-dependent fashion to both conjugate vaccines, with maximum antibody titers observed at the highest dose and 4 weeks after the last of three weekly immunizations. PNAG-DT and dPNAG-DT vaccines were also very immunogenic in rabbits. Antibodies raised to the conjugate vaccines in rabbits mediated the opsonic killing of various staphylococcal strains, but the specificity of the opsonic killing was primarily to dPNAG, as this antigen inhibited the killing of S. aureus strains by both PNAG- and dPNAG-specific antibodies. Passive immunization of mice with anti-dPNAG-DT rabbit sera showed significant levels of clearance of S. aureus from the blood (54 to 91%) compared to control mice immunized with normal rabbit sera, whereas PNAG-specific antibodies were ineffective at clearing S. aureus. Passive immunization of mice with a goat antiserum raised to the dPNAG-DT vaccine protected against a lethal dose of three different S. aureus strains. Overall, these data show that immunization of animals with a conjugate vaccine of dPNAG elicit antibodies that mediated opsonic killing and protected against S. aureus infection, including capsular polysaccharide types 5 and 8 and an untypable strain.  (+info)