SHIGELLA:Surface polysaccharides of pathogenic bacteria, including capsular polysaccharides (CPS) or the O-specifc polysaccharide (O-SP) of lipopolysaccharides (LPS),serve both as essential virulence factors and as protective antigens. Covalent binding of CPS or of O-SP to medically-useful proteins to form conjugates both increases their immunogenicity and confers T-cell dependence to these saccharides making them suitable vaccines for infants and children. The O-SP of Shigella sonnei bound to recombinant non toxic diphtheria toxin (CRM9)and of S.flexneri 2a bound to the recombinant, non toxic, succinylated, exoprotein A (rEPA-succ) were safe and induced IgG antibodies to the homologous LPS in 1-4 year-olds: a 4-fold rise was induced by the S.flexneri 2a conjugate in 92% of the children, the S.sonnei conjugate in 85%. A phase 3 study of these conjugates in 1-4 year-olds has begun. In collaboration with the Lanzhou Vaccine Institute and Provincial Medical Center in Henan, China, a clinical trial of these is being planned. CROSS REACTING POLYSACCHARIDES, B.PUMILUS: To investigate if concurrent administration of a cross-reacting along with a homologous CPS has an advantage over the use of the homologous CPS alone, the cell wall polysaccharide (PS) of Bacillus pumilus, Sh18, reported to cross react with the CPS of haemophilus influenzae type b (Hib), was isolated and it's structure investigated using GC-MS,NMR, fast atom bombardment and several sugar degrading techniques. It was shown to be composed of polyribitolphosphate, polyribitolphsphate substituted at C2 with N-acetyl glucosamine and polyglycerolphosphate. Besides with the anti Hib it reacted with anti Staphylococcus epidermidis. The polysaccharide was conjugated to carrier proteins and it's immunogenicity evaluated in GP mice. Conjugate-induced antibodies reacted with the homologous and several cross-reacting polysaccharides. NEISSERIA MENINGITIDIS group A causes endemic and epidemic meningitis, notably in the meningitis belt of Africa. A CPS vaccine , effective and available, is underutilized. To further improve it's immunogenicity it was conjugated to BSA using ADH as a linker bound first to the CPS or the BSA. Contrary to the CPS alone the conjugates were immunogenic in mice, with booster responses after 2nd and 3rd injections and bactericidal activity related to IgG anti CPS levels. Conjugates of the cross reactive polysaccharides, e.coli K93 and B.pumilus SH17,did not induce anti Men. A CPS. BORRELIA BURGDORFERI, a spirochete transmitted though the bite of infected Ixodes ticks, is the etiologic agent of Lyme disease. A protein vaccine against it is available but is not effective below the age of 12 years. LPS has been described in other spirochetes but it's presence in B. burgdorferi has been debated. We have not been able to confirm it's presence. The search for LPS revealed 2 unique glycolipids:cholesteryl 6-O-palmitoyl-beta-D-galactopyranoside (BBGL1) and1-Opalmitoyl-2-O-oleyl-3-O-alpha-D galactopyranosl-sn-glycerol (BBGL2) There is evidence that they are surface exposed. Injected in various formulations into mice BBGL1 induced specific antibodies,in order of induced levels: CFA,PBS,DMSO,squalene. The biological effect of the antibodies is being ingestigated. The CPS of N.meningitidis Gr.W135, responsible for recent outbreaks in Africa, was isolated and conjugated to S.aureus recombinant super antigen 2. BACILLUS ANTHRACIS, a potential cause of lethal human infection, has 2 essential virulence factors without either of which it is not pathogenic for humans. these factors are: 1.anthrax toxin, 2.a capsule. The toxin is composed of 3 peptides: Lethal Factor, Edema Factor and Protective Antigen, each by itself non toxic. PA is the toxin part that binds to mammalian cells. It has to have a 20 KDa peptide hydrolyzed off exposing a site to which LF or EF may bind rendering toxins that enzymatically modify substrates in mammalian cell cytosol. The capsule is composed of poly-D-gamma-glutamic acid(PGA).It is non-immunogenic and it's protective effect unknown. The licensed vaccine is safe and protective but has limitations that justify development of improved vaccines. A recombinant PA was isolated from an unencapsulated strain grown in a fermenter. Several formulations with formaldehyde treated and alum adsorbed materials were found to be immunogenic in mice. Clinical lots are being prepared. The capsule has been isolated from a non toxic strain and it or corresponding syntethic peptideswere bound to BSA, rEPA or rPA. To identify the optimal construct peptides of varying lengths, 5,10 and 20-mers,of D or L configuration with active groups at the C or n termini were conjugated. the conjugates were characterizedbby physico-chemical and immunological assays and immunogenicity in 5-6 week old mice. Opposed to PGA alone all conjugates were immunogenic and the D-PGA -induced antibodies were opsonophagocytic. rPA was the more effective carrier. STREPTOCOCCUS PNEUMONIAE type 6B,one of the most common and least immunogenic types, was conjugated to tetanus toxoid and evaluated in patients with chronic obstructive pulmonary disease, compared to the 23-valent polysacharide vaccine in these patients, and to the response of healthy young adults. No statistical differences in antibody levels were found between the 3 groups. Opsonophagocytosis was related to IgG anti type 6B levels. PLASMODIUM FALCIPARUM:Techniques used in ourpreparation of our synthetic S. dysenteriae type 1 and B. anthracis experimental vaccines are being applied to proteins of the zygote of this organism, in an attempt to increase their immunogenicity.
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