Immunity and Control Analysis of H. Influenzae Type b Polysaccharide-protein Conjugate Vaccine

Abstract

Haemophilus influenzae type b (HIb) is the widest known cause of bacterial meningitis and a leading cause of bacterial diseases in the United States and many areas of the world. It causes epiglotitis, pneumonia, septic arthritis, osteomylitis and penricarditis. Many sunvivors of meningitis experience in permanent mild hearing loss and mental retardation. The capsular polysaccharide of polyribosylribitol phosphate (PRP) is a major virulence facor of the organism. Antibody to PRP is the primary contributor to induce serum bactericidal activity. Three types of HIb-protein conjugate vaccines were prepared by different methods, using a different protein carrier, PS size, nature of linkage, and ratio of protein and PS: (1) The Connaught Laboratories combined diphtheria toxoid (DT)to HIb PS by cyanogen bromide activation of PS and conjugation of PS and DT by carbodiimide; (2)In the praxis Biologics, HIb oligosaccharides were conjugated to a mutant diphtheria toxin, CRM197, by the reductive amination; (3)The Merck, Sharp & Dohme conjugate vaccine utilized a 40 KD meningococcal outer membrane protein(OMP)and a mutiple synthetic procedure. HIb PS-protein oonjugate vaccine produced high antibody levels in infants 2-6 months of age and young children with no major adverse reactions. Control tests of HIb conjugate vaccine were carried out in two stages : (A) Each lot of PS shall be examined for(l) the chemical content, such as ribose and phosphorus;(2) contamination of cell components, such as protein, LPS and nucleic acids. The carrier protein was then examined for its purity. The conjugate bulk concentrate was next examined for free ribose content, ratio of PS and protein, molecular size, contamination of LPS and pyrogenicity. (B) The final conjugate vaccine contains 10-25 ug PRP per dose. The vaccine was tested for identity and amount of HIb PS, contents of free ribose, free protein, LPS, as well as sterility, general safety and pyrogenicity. Immunization of HIb PS-protein conjugate vaccine holds great promise for the prevention of HIb diseases in young children. An approach using similar technology can be applied to the prevention in the future of diseases caused by other encapsulated bacteria.