Hib Capsular Polysaccharide Research Articles

Haemophilus influenzae type b lipooligosaccharide induces meningeal inflammation.

We evaluated the ability of two Haemophilus influenzae type b (Hib) components, lipooligosaccharide (LOS) and capsular polysaccharide, to provoke meningeal inflammation in rabbits. Intracisternal inoculation of 2 fg-200 ng of LOS produced a dose-dependent increase in concentrations of white blood cells and protein in cerebrospinal fluid, whereas 4 micrograms of Hib capsular polysaccharide did not provoke meningeal inflammation. Preincubation of LOS with a murine monoclonal antibody to Hib LOS did not reduce the potency of the LOS. Incubation of LOS with polymyxin B (which neutralizes LOS by binding to its lipid A region) and deacylation of the LOS with acyloxyacyl hydrolase (a neutrophil enzyme that removes nonhydroxylated fatty acyl chains from lipid A) reduced meningeal inflammation. We demonstrated that purified Hib LOS induced meningeal inflammation in this model and suggest that the lipid A moiety of Hib LOS is principally responsible for this host response.

Effect of complement depletion on anticapsular-antibody-mediated immunity to experimental infection with Haemophilus influenzae type b.

Antibody to the capsular polysaccharide of Haemophilus influenzae type b (Hib) was not protective in infant rats depleted of complement by cobra venom factor (CoVF) even when serum antibody levels were many times the minimum protective level. Partial protection from Hib infection was achieved in CoVF-treated rats only if they were passively hyperimmunized with large doses of immunoglobulin G Hib capsular polysaccharide antibody. In addition, nonimmune CoVF-treated rats had higher mortality and blood bacterial density than nonimmune rats with intact complement systems.

1gG2 SUBCLASS DEFICIENCY PRESENTING AS H. INFLUENZAE B (HIB) DISEASE AFTER IMMUNIZATION WITH HIB VACCINE

Twenty-six healthy children previously immunized (imm) with the Hib capsular polysaccharide (Hib CP) vaccine at age 19 to 38 mos (GM=28 mos; 1 of 26 <24 mos) developed Hib systemic disease at age 22 to 45 mos (GM=32 mos), which was 2 to 44 wks (GH=12.6 wks) after imm. Disease consisted of 16, 6, and 4 cases of meningitis, epiglottitis, and other infections, respectively. Antibody (Ab) to the Hib CP in serial convalescent serum samples collected 24 days-8 mos after infection failed to increase to 1μg/ml in 17 Of the 26 and had a GMT of 0.56μg/ml, which contrasted with Ab of an age-matched control group of Hib infected, nonimm children (GMT=2.7μg/ml, p<.05). IgG2 subclass deficiency was detected in 9 of the 26 and was associated with low or borderline-low levels of IgG and IgA in 5 and 6 of the 9 respectively. Postinfection Ab to the Hib CP was <1 μg/ml in 7 of the 9 with IgG2 deficiency (GMT=0.29μg/ml), but all had normal Ab titers to tetanus and diphtheria toxoids. At present, reimm with the Hib CP and imm with pneumococcal CPs induced poor Ab responses in 1 of 1 and 3 of 3 with IgG2 deficiency, respectively. These findings suggest that a considerable proportion of cases of this new entity - Hib disease after Hib CP imm - is associated with IgG2 subclass deficiency and poor Ab responses to Hib infection.

Recurrent sinopulmonary infection and impaired antibody response to bacterial capsular polysaccharide antigen in children with selective IgG-subclass deficiency

Abstract We studied 20 children with recurrent sinopulmonary infections and serum IgG levels within the normal range, who had selective IgG-subclass deficiency. Twelve of the children were IgG2 deficient, five were IgG3 deficient, and three were deficient in both IgG2 and IgG3. IgA deficiency was present in 3 of the 20 patients. In the children with IgG2 deficiency, serum antibody concentrations to the capsular polysaccharide of Hemophilus influenzae type B (Hib) were significantly lower than those in age-matched controls, both before and after immunization with the Hib capsular polysaccharide antigen, which elicits antibody predominantly of the IgG2 subclass. In contrast, their serum antibody titers to the tetanus and diphtheria toxoid protein antigens, which elicit antibody predominantly of the IgG1 subclass, were normal in comparison with those of age-matched controls. These results suggest that impairment of the antibody response to specific microbial antigens predisposes patients with selective IgG-s...

Functional characterization of human IgG, IgM, and IgA antibody directed to the capsule of Haemophilus influenzae type b.

Antibody to the capsular polysaccharide (CP) of Haemophilus influenzae b (Hib) is bactericidal, opsonic, and protective. Minimum protective levels of primarily IgG antibody to Hib CP, calculated from passive immunization studies, have been found to be approximately .06-.15 microgram/ml of serum. The human response to antigenic challenge with the Hib capsule, however, includes production of antibody to Hib CP of different isotypes whose function against Hib is unclear. In order to characterize the function of antibody to Hib CP of different isotypes, we purified human IgG, IgM, and IgA from the serum of an adult donor who had been previously immunized with purified Hib CP vaccine. The globulin preparations were greater than 99% isotypically pure, contained large quantities of anticapsular antibody, and differed in function against Hib. IgG antibody to Hib CP was bactericidal and opsonic for human polymorphonuclear leukocytes (PMNLs) in the presence of complement and protective in infant rats. IgM, although more bactericidal than IgG (P less than .01) and equally protective in rats, opsonized Hib poorly for PMNLs. IgA was not bactericidal or opsonic and did not prevent bacteremia and meningitis in rats challenged with Hib. We conclude that antibody directed against the capsule of Hib differs in antibacterial function depending on class. These data may be important to acurately estimate minimum protective levels of anticapsular antibody after vaccination or natural infection and may have implications for the manner in which the host clears Hib from the circulation.

Immunogenic proteins in cell-free culture supernatants of Haemophilus influenzae type b.

Cell-free culture supernatant (CFCS) prepared from Haemophilus influenzae type b (Hib) was examined for the presence of soluble Hib proteins. Two proteins with apparent molecular weights of 100,000 (100K) and 116K were predominant in the CFCS, and antibodies directed against these proteins could be detected by radioimmunoprecipitation or Western blot analyses of serum from adult rats immunized with Hib. Radioimmunoprecipitation analyses and sodium dodecyl sulfate-polyacrylamide gel electrophoresis of these two proteins demonstrated that the 100K CFCS protein was also present on the cell surface of Hib, whereas the 116K CFCS protein was only detectable in culture supernatants. Both the 100K and 116K CFCS proteins were immunogenic in human infants with Hib meningitis and in infant rats systemically infected with Hib. In addition, the first detectable antibodies produced in these Hib-infected rats against Hib proteins were specific for the 100K protein in both its CFCS and cell-associated forms. These two CFCS proteins were also immunogenic in rats immunized with CFCS in the absence of Hib infection. Monoclonal antibody directed against the 100K protein reacted with 34 of 55 Hib strains examined by using a colony blot radioimmunoassay. The immunogenicity of the 100K and 116K CFCS proteins suggests that one or both of these proteins may have potential for vaccine development, either by themselves or covalently coupled to Hib capsular polysaccharide.

Mucosal antibody response to parenteral vaccination with Haemophilus influenzae type b capsule

The simultaneous serum and mucosal antibody response to parenteral vaccination with the Haemophilus influenzae type b (Hib) polysaccharide capsule (PRP) was evaluated in a group of 10 children and nine adults. All subjects responded to parenteral vaccination with an increase in serum anticapsular antibody. The children's preimmunization anti-PRP antibody level ( x = 0.04 μg/ml) and 3 wk postimmunization level ( x = 19.3 μg/ml) were lower than the adults' (preimmunization x = 1.5 μg/ml; postimmunization x = 81.2 μg/ml). Eight of 10 children and seven of nine adults also developed a rise in antibody in nasal secretions. The children's mean nasal preimmunization level was 0.74 μg/mg IgA and mean postimmunization level was 5.0 μg/mg IgA. The adults' mean nasal preimmunization level was 0.98 μg/mg IgA and mean postimmunization level was 3.0 μg/mg IgA. Salivary antibody responses generally followed the pattern of nasal antibody responses. These data suggest that parenteral administration with the Hib capsular polysaccharide can produce a mucosal antibody response. Furthermore, although serum antibody responses to PRP vaccination are greater in adults than in children, mucosal antibody responses are comparable.

Cross-reactivity with Escherichia coli K100 in the human serum anticapsular antibody response to Haemophilus influenzae type B.

Escherichia coli K100 is known to induce antibodies cross-reactive with the capsular polysaccharide (CP) of Haemophilus influenzae b (Hib); the cross-immunogenicity is found consistently in a number of mammalian species including man. We have studied the reciprocal cross-immunogenicity of Hib or its purified CP in man. Of 25 adults and 13 children responding to systemic immunization with Hib CP, only four and four, respectively, made K100 CP cross-reactive antibody, determined by radioantigen-binding inhibition. The detection of preimmunization cross-reactive antibody was not statistically predictive of induction of postimmunization cross-reactive antibody. Cross-reactive antibody was detected in only one of 11 children making an anticapsular response to Hib systemic infection and two of four children responding to asymptomatic nasopharyngeal colonization. In contrast, cross-reactivity was detected in the naturally occurring anti-Hib-CP antibody of 27 of 42 children. Thus, humans responding to Hib or its CP often do not make antibody to the K100-cross-reactive determinant(s), implying that the cross-reactive natural antibodies frequently seen in children must have a stimulus other than Hib.

1030 PASSIVE IMMUNIZATION OF INFANTS AGAINST HAEMOPHILUS INFLUENZAE TYPE B (HIB) BY MATERNAL VACCINATION

Prior to a planned conception, 24 women were immunized with purified HIB capsular polysaccharide to attempt to extend their offspring's period of passive antibody protection against systemic HIB disease. All women had an antibody rise. Geometric mean titer prior to immunization was 1.2 μg/ml and at 1, 7-10, and 19-27 months after immunization was 35 μg/ml, 23 μg/ml, and 16 μg/ml respectively as measured by radioantigen binding. Most post-immunization antibody was of the IgG class as determined by an enzyme-linked immunosorbent assay. However, there was a wide range of post-immunization titers (2.7-310 μg/ml at 7-10 months post-immunization). The low magnitude antibody responders also had low IgG antibody levels that were not boostable. The offspring of 6 women, born 11½ to 17½ months after immunization, had antibody titers markedly higher than those of age-matched infants of unvaccinated women. Their titers persisted above the estimated protective level through 6-12 months of age. Four infants, all born to low-responder women, had titers similar to natural antibody titers. These results suggest that the interval of passive antibody protection can be extended. This approach may be especially useful in populations highly susceptible to HIB and may be applicable to the prevention of other childhood and neonatal infections.