Safety and immunogenicity of two Haemophilus influenzae type b polysaccharide-tetanus toxoid conjugate vaccines (PRP-T) given with diphtheria-tetanus-pertussis vaccine to young Papua New Guinean children.

BACKGROUND: In view of high mortality and morbidity from Haemophilus influenzae type b (Hib) in young Papua New Guinean children, the incorporation of a Hib conjugate vaccine into a nationwide immunization program would be of major public health benefit. METHODS: We evaluated the safety and immunogenicity of a lyophilized and a liquid form of Hib polysaccharide-tetanus toxoid conjugate vaccines (PRP-T) given in the same syringe as diphtheria-tetanus-pertussis (DTP) vaccine to children in Goroka, Eastern Highlands Province. In Part 1 of the study 209 children were randomized to receive at ages 1, 2 and 3 months either DTP alone or a liquid formulation of DTP/PRP-T or lyophilized PRP-T dissolved in DTP suspension. A further 75 children were given the liquid DTP/PRP-T formulation at ages 2, 3 and 4 months (Part 2). 54 children aged 15-18 months were given a booster of the same preparation of PRP-T/DTP as they had received during Part 1. Blood for antibody assays was collected at enrolment, before (Part 1 only) and one month after the third dose, then just before and 3 weeks after the booster dose. RESULTS: Follow-up to age of 12 months showed that PRP-T was safe with no evidence of impaired response to individual vaccine components when combined with DTP. Geometric mean titres (GMTs) of anti-PRP antibody before vaccination (n = 64, mean age 41 days), after 2 doses (mean age 99 days) and after 3 doses (mean age 132 days) of the lyophilized formulation were 0.21, 1.48 and 5.04 microg/ml, respectively, with 58% and 89% having anti-PRP antibody titres > or = 1.0 microg/ml after 2 and 3 doses, respectively. Anti-PRP antibody responses to the liquid Hib vaccine formulation were lower (GMT post-dose 3 = 0.48 microg/ml) than to the lyophilized formulation, but better responses were elicited from older children (Part 2; GMT post-dose 3 = 0.78 microg/ml, with 79% > or = 0.15 microg/ml). Both PRP-T preparations elicited excellent booster responses suggesting that children are likely to be protected if exposed to Hib infection. CONCLUSIONS: Lyophilized PRP-T given together with DTP is safe and immunogenic when given to young infants. The liquid DTP/PRP-T formulation showed a lower immunogenicity than in earlier studies with this vaccine, which might have been due to exposure to low temperature during shipment or the younger age at immunization.

Elevated levels of maternal anti-tetanus toxin antibodies do not suppress the immune response to a Haemophilus influenzae type b polyribosylphosphate-tetanus toxoid conjugate vaccine.

Reported are the effects of elevated levels of anti-tetanus antibodies on the safety and immune response to a Haemophilus influenzae type b polyribosylphosphate (PRP)-tetanus toxoid conjugate (PRP-T) vaccine. A group of Thai infants (n = 177) born to women immunized against tetanus during pregnancy were vaccinated with either a combined diphtheria-tetanus-pertussis (DTP) PRP-T vaccine or DTP and a PRP-conjugate vaccine using Neisseria meningitidis group B outer-membrane proteins as a carrier (PedVax HIB). Although most infants possessed high titres (> 1 IU/ml) of anti-tetanus antibodies, the DTP-PRP-T combined vaccine engendered an excellent antibody response to all vaccine components. In both vaccine groups > 98% of infants attained anti-PRP antibody titres > or = 0.15 microgram/ml. The geometric mean anti-PRP antibody titres were 5.41 micrograms/ml and 2.1 micrograms/ml for infants immunized with three doses of PRP-T versus two doses of PedVax HIB vaccines, respectively (P < 0.005). Similarly, the proportion of infants who achieved titres > or = 1 microgram/ml was higher in the PRP-T group (87.8%) than in the group immunized with PedVax HIB (74.2%) (P = 0.036). A subgroup analysis showed that there was no significant difference in the anti-PRP antibody response for infants exhibiting either < 1 IU of anti-tetanus antibody per millilitre or > or = 1 IU/ml at baseline. These finding indicate that pre-existing anti-carrier antibody does not diminish the immune response to the PRP moiety. All infants possessed protective levels of anti-D and anti-T antibody levels after immunization.

PIP: Reported are the effects of elevated levels of anti-tetanus antibodies on the safety and immune response to Haemophilus influenzae type b polyribosylphosphate (PRP)-tetanus toxoid conjugate (PRP-T) vaccine. A group of Thai infants (n = 177) born to women immunized against tetanus during pregnancy were vaccinated with either a combined diptheria-tetanus-pertussis (DTP) PRP-T vaccine or DTP and a PRP-conjugate vaccine using Neisseria meningitidis group B outer-membrane proteins as a carrier (PedVax HIB). Although most infants possessed high titers (1 IU/ml) of anti-tetanus antibodies, the DTP-PRP-T combined vaccine engendered an excellent antibody response to all vaccine components. In both vaccine groups, 98% of infants attained anti-PRP antibody titers of 0.15 mcg/ml or higher. The geometric mean anti-PRP antibody titers were 5.41 mcg/ml and 2.1 mcg/ml for infants immunized with 3 doses of PRP-T vs. 2 doses of PedVax HIB vaccines, respectively (P 0.005). Similarly, the proportion of infants who achieved titers of 1 mcg/ml or higher was greater in the PRP-T group (87.8%) than in the group immunized with PedVax HIB (74.2%) (P = 0.036). A group analysis showed that there was no significant difference in the anti-PRP antibody response for infants exhibiting either less than 1 IU/ml of anti-tetanus antibody or 1 or more IU/ml at baseline. These findings indicate that pre-existing anti-carrier antibody does not diminish the immune response to the PRP moiety. All infants possessed protective levels of anti-D and anti-T levels after immunization.

Safety and immunogenicity of intranasally administered inactivated trivalent virosome-formulated influenza vaccine containing Escherichia coli heat-labile toxin as a mucosal adjuvant.

A trivalent influenza virosome vaccine containing hemagglutinin and Escherichia coli heat-labile toxin (HLT) was administered intranasally to young adults and elderly subjects. Symptoms that followed immunization were mild and transient. A significant increase in serum hemagglutination inhibition (HI) antibody was noted for the 3 vaccine strains. There was no significant difference in postimmunization geometric mean titers or seroconversion rates between age groups. The percentage of subjects attaining protective HI titers (>/=40%) was comparable in both groups for the A/Bayern (P=.5) and B/Beijing (P=.3) strains but was higher among young adults (92.2%) versus elderly subjects (76.5%; P=.057) for the A/Wuhan strain. The proportion of subjects with nonprotective baseline titers who attained protective levels after immunization was similar in both age groups for the A/Bayern and B/Beijing components. For the A/Wuhan component, significantly (P=.017) more young adults achieved protective titers versus elderly subjects (85. 7% and 53.8%, respectively). Vaccination evoked a significant (P<. 005) increase in anti-HLT antibody titers.

Immunotherapy of sepsis: flawed concept or faulty implementation?

Gram-negative bacillary sepsis is a leading cause of death among patients hospitalized in intensive care units. While initial clinical studies with the passive administration of anti-endotoxin core-glycolipid (CGL) antibodies for the treatment and prophylaxis of sepsis showed promising results, subsequent studies failed to show a consistent benefit. There appears to be a good correlation between anti-CGL antibody levels at the onset of sepsis and maintenance of antibody levels during sepsis with outcome. Previous clinical studies may have failed because insufficient amounts of antibody were administered early in the course of sepsis. Unlike the case with anti-CGL antibodies, polyvalent, hyperimmune type-specific antibody preparations may prevent the development of infections; however, these antibodies also must be provided in adequate amounts and in close proximity to infection in order to provide a beneficial effect. These pharmacokinetic requirements may limit the utility of passive immunotherapy for the prophylaxis of sepsis. Active immunization of acutely traumatized patients or of rats subsequently rendered neutropenic with cyclophosphamide induced high antibody levels for extended periods of time. Since trauma and other conditions are associated with a Th(2) response, these conditions may favor antibody formation following active immunization. Active immunization with both anti-CGL and/or polyvalent-specific vaccines for the prophylaxis of sepsis with passive supplementation at the onset of sepsis is an approach that merits further investigation.

Safety and immunogenicity of a Haemophilus influenzae type B polysaccharide-tetanus toxoid conjugate vaccine combined with diphtheria, tetanus and pertussis vaccines in Thai infants.

A randomized, open, multicenter trial was conducted to determine the safety and immunogenicity of a Haemophilus influenzae type b polysaccharide-tetanus toxoid (PRP-T) conjugate vaccine combined with tetanus, diphtheria and pertussis (DTP) vaccine in 271 Thai infants born to mothers immunized against tetanus during pregnancy. Infants were immunized at approximately 2, 4 and 6 months of age with these vaccines. To determine if elevated levels of anti-tetanus toxin antibodies suppressed the anti-PRP antibody response, a second group of infants were immunized with PRP complexed with outer membrane proteins of Neisseria meningitidis (Pedvax HIB) in one limb at 2 and 4 months of age and DTP vaccine in the other limb at 2, 4 and 6 months of age. A third group of infants received only DTP vaccine at 2, 4 and 6 months of age. The occurrence of both local and systemic adverse reactions were comparable in all 3 groups. The geometric mean anti-tetanus antibody titer was > 1 IU/ml at baseline. Approximately 1 month after the administration of the third dose of vaccine, 98.5%, 99.3% and 9.7% of the children immunized with DTP+Pedvax HIB, DTP-PRP-T or DTP possessed > or = 0.15 microgram of anti-PRP antibody per ml. No child in the DTP group achieved > or = 1 microgram/ml while 74.2% and 89.3% did so after immunization with DTP+Pedvax HIB, or DTP-PRP-T, respectively (p < 0.05). Immune responses to diphtheria, tetanus and pertussis antigens were similar in all vaccine groups. These results demonstrate that elevated tetanus antibody titers do not diminish the anti-PRP antibody response following immunization with a PRP-T conjugate combined with DTP vaccine.

Immunization of cystic fibrosis patients with a Pseudomonas aeruginosa O-polysaccharide-toxin A conjugate vaccine.

Healthy, non-colonized cystic fibrosis (CF) patients (N = 26) were immunized with an octavalent Pseudomonas aeruginosa O-polysaccharide-toxin A conjugate vaccine. Vaccination was well tolerated and induced anti-lipopolysaccharide (LPS) antibodies of a high affinity capable of promoting the opsonophagocytic killing of P. aeruginosa by human peripheral lymphocytes. In contrast, anti-LPS antibodies acquired after natural infection possessed a very low affinity and were non-opsonic. To determine if immunization could prevent or delay infections due to P. aeruginosa, the infection rate among immunized patients was compared retrospectively to age and gender-matched controls. After 6 years of clinical follow-up, 15/20 (75%) of control and 8/23 (35%) of immunized subjects were classified as infected (p = 0.022). The persistence of high-affinity antibodies among immunized patients correlated with a significantly lower rate of infection after 4-6 years of observation. Infection of immunized patients was correlated with a dramatic decline in total antibody titer between year 2 and 3 of follow-up. Smooth, typeable strains of P. aeruginosa predominated among immunized patients. In contrast, rough, nontypeable strains were most frequently isolated from nonimmunized patients. Mucoid P. aeruginosa strains were isolated from 6 nonimmunized patients versus only I immunized subject.

Randomized, double-blind placebo-controlled trial to evaluate the safety and immunogenicity of combined Salmonella typhi Ty21a and Vibrio cholerae CVD 103-HgR live oral vaccines.

Healthy adults (n=330) were randomized to receive either a bivalent vaccine composed of Vibrio cholerae CVD 103-HgR and Salmonella typhi Ty21a or a placebo. The combined vaccine was well tolerated. Approximately 80% of vaccines manifested a significant rise in anti-S. typhi immunoglobulin G or immunoglobulin A lipopolysaccharide antibody levels. Significant (fourfold or greater) rises in anti-Inaba or anti-Ogawa vibriocidal antibody titer were achieved by 94 and 80% of vaccine recipients, respectively. Elevated baseline vibriocidal antibody titers showed a modest suppressive effect on the rate of seroconversion.

Factors influencing the stability of live oral attenuated bacterial vaccines.

Live oral attenuated vaccines against typhoid fever (Salmonella typhi Ty21a) and cholera (Vibrio cholerae CVD 103-HgR) have been licensed for human use. Vaccine potency is dependent upon each dose containing a minimum number of viable organisms and galenic parameters. To ensure long-term stability, such vaccines must be stored at 5 degrees C +/- 3 degrees C. However, exposure to ambient temperatures (25 degrees C) for short periods of time (< 7 days) does not compromise vaccine potency. Brief exposures (< or = 24 hours) to temperatures as high as 37 degrees C will also not render the vaccine unsuitable for use. The Ty21a vaccine is available either as enteric-coated capsules or as a "liquid formulation", while CVD 103-HgR is presented only in the latter form. Each galenic formulation presents unique challenges with regard to the production of stable vaccines. Residual moisture, excipients, and processing temperatures during manufacturing were all found to markedly affect vaccine stability.

Effect of high-affinity anti-Pseudomonas aeruginosa lipopolysaccharide antibodies induced by immunization on the rate of Pseudomonas aeruginosa infection in patients with cystic fibrosis.

Patients with cystic fibrosis (CF; N = 26) and with no prior history of infection with Pseudomonas aeruginosa were immunized with an octavalent O-polysaccharide-toxin A conjugate vaccine. During the next 4 years, 16 patients (61.5%) remained free of infection and 10 (38.5%) became infected. Total serum antilipopolysaccharide (LPS) antibody levels induced by immunization were comparable in infected and noninfected patients. In contrast, 12 of 16 noninfected versus 3 of 10 infected patients (p = 0.024) mounted and maintained a high-affinity anti-LPS antibody response. When compared retrospectively with the rate in a group of age- and gender-matched, nonimmunized, noncolonized patients with CF, the rate at which P. aeruginosa infections were acquired was significantly lower (p < or = 0.02) among all immunized versus nonimmunized patients during the first 2 years of observation. Subsequently, only those immunized patients who maintained a high-affinity anti-LPS antibody response had a significant reduction (p < or = 0.014) in the rate of infection during years 3 and 4. Smooth, typeable strains of P. aeruginosa predominated among immunized patients; rough, nontypeable strains were most frequently isolated from nonimmunized patients. Mucoid variants were isolated from one immunized patient versus six nonimmunized patients. These results indicate that the induction of a high-affinity P. aeruginosa anti-LPS antibody response can influence the rate of infection in patients with CF.

Synthesis and characterization of a polyvalent Escherichia coli O-polysaccharide-toxin A conjugate vaccine.

A 12-valent Escherichia coli O-polysaccharide (O-PS)-toxin A conjugate vaccine was formulated. Nonpyrogenic, low-molecular-weight O-PS was derived from lipopolysaccharides (LPS) of the following serotypes: O1,O2,O4,O6,O7,O8,O12, O15,O16,O18,O25, and O75. Individual O-PS were covalently coupled to Pseudomonas aeruginosa toxin A using adipic acid dihydrazide as a spacer molecule and carbodiimide as a coupling agent. On a weight basis, the final multivalent vaccine was composed of 43% O-PS and 57% toxin A. The vaccine was nontoxic nad nonpyrogenic in anti-LPS immunoglobulin G (IgG) antibody titers. When passively transferred to mice, immune rabbit IgG conferred statistically significant (p < 0.05) protection against a challenge with 9 of the 12 vaccine serotypes. For two serotypes, although the mortality rate declined by > or 50% in the passively immunized versus the control group, the difference did not reach statistical significance. The degree of protection provided by passively transferred IgG was influenced by both the anti-LPS antibody levels in the IgG preparation and the virulence of the challenge strain. Active immunization of mice with either conjugate vaccine or killed E. coli whole cells did not confer protection. This was most probably due to the fact that these antigens induced a meagre anti-LPS IgG antibody response.

Safety and immunogenicity of a V3 loop synthetic peptide conjugated to purified protein derivative in HIV-seronegative volunteers.

OBJECTIVES: To develop a peptide-based model for a preventive vaccine for HIV-1 infection. DESIGN: Phase I trial in HIV-1-seronegative volunteers. PARTICIPANTS: Adult healthy subjects HIV-1-antibody-seronegative in an enzyme-linked immunosorbent assay, screened for tuberculin [purified protein derivative (PPD)] reactivity with 2 tuberculin units PPD-administered intradermally. INTERVENTIONS: Submicrogram doses of a PPD conjugate with a peptide of the primary neutralizing domain (PND) of HIV-1MN (PPD-MN-PND) were administered intradermally to tuberculin skin-test-positive and -negative volunteers. RESULTS: Antibodies to the MN-PND were measured after two immunizations in 10 out of 11 PPD skin-test-positive volunteers. After the fourth immunization high-affinity antibodies were detected, which persisted for over 1 year. High titers of MN-PND-specific immunoglobulin (Ig) G and IgA were detected in the serum and saliva of all volunteers tested. Serum antibodies were cross-reactive with PND peptide from some other HIV-1 strains but neutralized only the HIV-1MN prototype. Human leukocyte antigen (HLA)-B7-restricted MN-PND-specific cytotoxic T lymphocytes (CTL) were also detected. CONCLUSIONS: The PPD-MN-PND vaccine at submicrogram doses is safe and immunogenic in PPD skin-test-positive healthy adult volunteers. Long lasting humoral immune responses in the serum and saliva were possibly accompanied by HLA-B7-restricted CTL responses. This is a vaccine prototype that can be rapidly and inexpensively modified to include other peptide epitopes. It is especially suitable for use in a worldwide multibillion Bacillus Calmette-Guérin (BCG)-primed or tuberculosis-exposed population at risk for HIV-1 infection.

Human immunodeficiency virus-1 principal neutralizing domain peptide-toxin A conjugate vaccine.

To enhance the potential efficacy of peptide-based vaccines for human immunodeficiency virus-1 (HIV-1), a principal neutralizing domain (PND) peptide (KRIHIGPGRAFYT) (HIV-1MN) was covalently coupled to Pseudomonas aeruginosa toxin A (TA). Immunization of guinea-pigs with this conjugate vaccine, in the absence of an adjuvant, engendered a high-affinity antibody response to the homologous HIV-1MN PND peptide and to analogous peptides from variant strains of HIV-1. A substantial proportion of such antibodies was directed to the conserved GPGRAF motif. Anti-PND peptide antibodies were capable of neutralizing the homologous strain, HIV-1MN, in addition to two heterologous (RF, IIIB) variants, as determined either by inhibition of syncytia formation or by suppression of p24 antigen production in cultured cells. Therefore, the method of conjugation used preserved critical neutralizing epitopes expressed by the PND peptide. Monovalent or polyvalent PND-TA conjugates, which meet all safety criteria for human use, are a promising approach towards the development of an acquired immunodeficiency syndrome (AIDS) vaccine.

Safety and immunogenicity of a polyvalent Escherichia coli vaccine in human volunteers.

Since a limited number of O serogroups account for nearly 70% of bacteremic and meningitic Escherichia coli isolates, a polyvalent vaccine was made by conjugating a Pseudomonas aeruginosa exotoxin A carrier protein to the O polysaccharide of 12 serogroups of E. coli (O1, O2, O4, O6-O8, O12, O15, O16, O18, O25, O75). No serious reactions occurred in 88 vaccinees. Four-fold or greater increases in ELISA antibody levels over baseline were greatest (> 60% of vaccinees) for O1, O2, O6-O8 and O15; intermediate (approximately 50%) for O18 and O75, and poorest (> or = 45%) for O4, O12, O16, and O25. Responses with functionally active opsonophagocytic antibody generally paralleled ELISA antibody responses. With the availability of a safe, immunogenic E. coli vaccine, active and passive immunization strategies merit further development as adjunctive treatment for E. coli bacteremia and neonatal meningitis.

Immunization of noncolonized cystic fibrosis patients against Pseudomonas aeruginosa.

The long-term safety and immunogenicity of a polyvalent Pseudomonas aeruginosa conjugate vaccine was evaluated in 30 noncolonized cystic fibrosis patients. Four doses were administered over 3 years, and patients were followed for a mean of 38 months. No acute or long-term adverse effects were noted. Immunization engendered a significant antibody response to all vaccine components. A decline in titers during year 3 of observation was associated with a marked rise in the isolation of P. aeruginosa. This organism was isolated repeatedly from the respiratory tract of 4 patients and only once from 7 patients. The remaining patients were repeatedly culture-negative. Only 1 patient showed clinical deterioration associated with multiple isolations of P. aeruginosa.

Feasibility of prophylaxis and therapy against gram-negative infections by human monoclonal antibodies.

In a murine model of Gram-negative sepsis, we have shown that the prophylactic application of human monoclonal antibodies (HmAbs) with specificity for lipopolysaccharides (LPS) of Pseudomonas aeruginosa protected against bacterial infection. In this paper we show that the therapeutical application of 5 micrograms of these HmAbs up to 6 h after challenge with a lethal dose of live P. aeruginosa results in a protection rate of 70-90%. Administration 18 h after bacterial challenge, diminished the protection to 43% survival rate. Furthermore, using a mixture of HmAbs recognizing a total of six different P. aeruginosa serotypes, no interference in their protective capacities was found. Finally, these HmAbs also protected galactosamine-sensitized mice against lethal challenge with LPS. Our data show that the described HmAbs confer bactericidal activity as well as anti-endotoxic activity in vivo.

Properties determining the potential of naturally occurring and vaccine-induced human antibodies to protect against lethal infection of Pseudomonas aeruginosa.

In order to characterize antibodies responsible for the protection against fatal infection with Pseudomonas aeruginosa we analysed the fine specificity, avidity and protective capacities of naturally occurring anti-lipopolysaccharide (LPS) antibodies in two standard human Ig preparations and of vaccine-induced anti-LPS antibodies in a hyperimmune Ig preparation. Applying competitive binding assays, immunoblotting and an in vivo protection assay, we provide evidence that only preparations from immunized volunteers contain significant amounts of antibodies which confer detectable protection in a murine burn-wound model. Supported by the parallel analysis of monoclonal antibodies, our data suggest that protection by passive immunization with anti-LPS antibodies is mediated by antibodies specific for the LPS O-chain moiety of the corresponding virulent bacterium. Furthermore, our results indicate that protectiveness is restricted to a small population of antibodies with high affinity for particular O-chain epitopes.

Safety and immunogenicity of Pseudomonas aeruginosa conjugate A vaccine in cystic fibrosis.

To assess the safety and immunogenicity of a Pseudomonas aeruginosa octavalent O-polysaccharide-toxin A conjugate vaccine, 22 patients (mean age 7 years) with cystic fibrosis who had no history of colonisation with P aeruginosa were immunised with the vaccine. Adverse reactions were mild and self-limiting. IgG antibody concentrations to all vaccine antigens were significantly raised after vaccination and remained so for 12 months. Immunisation produced opsonic and toxin A neutralising antibodies. A booster dose given at 12 months led to an anamnestic response. There was no significant change in clinical status after vaccination. Further work to assess efficacy in patients with cystic fibrosis can now be considered since our findings support the safety and immunogenicity of the vaccine.

Production and characterization of a human hyperimmune intravenous immunoglobulin against Pseudomonas aeruginosa and Klebsiella species.

A hyperimmune globulin for intravenous use (H-IVIG) was prepared from the plasma of donors immunized with Pseudomonas aeruginosa and Klebsiella vaccines. H-IVIG preparations contained substantially higher IgG antibody levels to all nine P. aeruginosa vaccine antigens and to 22 of the 24 Klebsiella vaccine antigens than did commercial IVIG. The H-IVIG was more effective at promoting the opsonophagocytic killing of P. aeruginosa and Klebsiella vaccine serotype strains than normal IVIG. The H-IVIG neutralized greater than 20 times more toxin A than commercial IVIG. Only the H-IVIG offered significant protection against Klebsiella K2 sepsis. The H-IVIG provided significantly better protection against six of the eight P. aeruginosa vaccine serotypes than normal IVIG when compared in a murine burn wound sepsis model. The H-IVIG also protected mice against an Enterobacter aerogenes challenge, whereas normal IVIG was ineffective.