Serum antibody responses of juvenile and infant rhesus monkeys injected with Haemophilus influenzae type b and pneumococcus type 6A capsular polysaccharide-protein conjugates

Abstract

Juvenile and infant rhesus monkeys were injected subcutaneously with saline solutions of Haemophilus influenzae type b (Hib) and pneumococcus type 6A (Pn6A) capsular polysaccharides conjugated to either tetanus toxoid (TT), horseshoe crab hemocyanin, or cholera toxin (CT), and the antibody responses of the monkeys to both bacterial components were measured. All three Hib conjugates were immunogenic and elicited booster responses; their comparative immunogenicity was Hib-CT > Hib-TT > Hib-horseshoe crab hemocyanin. Hib alone did not elicit antibodies in the juveniles. Juveniles responded earlier and with higher levels of antibodies than did infants. TT, as well as diphtheria-tetanus toxoids-pertussis vaccine adsorbed injected concurrently at a separate site, increased both Hib and TT antibody responses in juveniles (P < 0.05). Concurrent injection of 5 Lf of fluid TT with a nonimmunogenic 5-jig dose in infants elicited levels of Hib antibodies comparable to those elicited by 50 jig of Hib-TT. Hib antibodies elicited by the conjugates remained at protective levels in both juveniles and infants 2 months after the last injection, were bactericidal, and conferred passive immunity against bacteremia in infant rats. Passive immunization of juveniles with tetanus immune globulin before each injection of Hib-TT did not suppress Hib antibodies. Hib-TT and Hib-CT elicited increases of Hib antibodies of the immunoglobulin M and G isotypes in the infants. The Pn6A-TT conjugate was considerably less immunogenic than the Hib-TT conjugate; only a few of the juveniles or infants responded with protective levels of Pn6A antibodies. Pn6A antibodies from responders conferred protection in mice against intraperitoneal challenge with Pn6A organisms. TT antibodies were elicited in both juvenile and infant animals after one injection of 50 jig of Hib-TT and in the infants injected with 5 jig of Hib-TT plus 5 Lf of TT; 5 jig of Hib-TT and Pn6A-TT in combination alone did not elicit TT antibodies. Hib-CT elicited CT antibodies in both juveniles and infants.

Vi capsular polysaccharide-protein conjugates for prevention of typhoid fever. Preparation, characterization, and immunogenicity in laboratory animals.

“…Indirect evidence was provided that the Vi elicited IgG antibodies in humans (50). H. influenzae type b-protein conjugates elicit IgG CPS antibodies (19)(20)(21)(22). It is likely therefore, that Vi conjugates will also elicit IgG antibodies .…”

“…Pneumococcus Type 6B-TT Conjugate (Pn6B-TT). Pneumococcus type 6B CPS, (Institut Merieux), was derivatized with adipic acid dihydrazide and bound to TT as described (17,20,22) . The protein/polysaccharide ratio of this preparation was 2.8 .…”

“…Juvenile Rhesus monkeys, housed at the Division of Product Quality Control, Office of Biologics Research and Review, FDA, were injected subcutaneously twice, 1-mo apart with 0.5 ml of Vi or Vi-CTx,i containing 25 kg of Vi. Controls were injected with Pn6B-TT containing 15 ttg of CPS (20). The monkeys were bled before and 3 wk after each injection .…”

“…Originally, Goebel and Avery (13,14) showed that the immunogenicity of pneumococcus type 3 polysaccharide could be increased by binding it chemically to a carrier protein . This principle has been applied successfully to increase the immunogenicity of CPS of other pathogens (15)(16)(17)(18)(19)(20)(21)(22)(23) . We developed methods for synthesizing covalent bonds between the Vi and proteins to both increase the immunogenicity of and to confer the property of T-dependence to this antigen .…”

Qualitative and quantitative analyses of the antibody response elicited by Haemophilus influenzae type b capsular polysaccharide–tetanus toxoid conjugates in adults with IgG subclass deficiencies and frequent infections

“…We did not find any correlation between the HibCP and TTspecific antibody responses in these patients. A similar dissociation between the antibody response to the CP and the protein component was elicited by conjugates in laboratory animals and humans [9,18].…”