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Background Bacillus Calmette-Guerin (BCG) vaccine is widely used for the prevention of tuberculosis, despite limited efficacy. Most immunological studies of BCG or Mycobacterium tuberculosis strains grow bacteria in the presence of detergent, which also strips the mycobacterial capsule. The impact of the capsule on vaccine efficacy has not been explored. Methods We tested the influence of detergent in cultures of BCG and M. tuberculosis strains on the outcome of vaccination experiments on mice and transcriptional responses on M. tuberculosis Results Vaccination of mice with encapsulated BCG promoted a more potent immune response relative to vaccination with unencapsulated BCG, including higher polysaccharide-specific capsule antibody titers, higher interferon γ and interleukin 17 splenic responses, and more multifunctional CD4(+) T cells. These differences correlated with variability in the bacterial burden in lung and spleen of mice infected with encapsulated or unencapsulated M. tuberculosis The combination of vaccination and challenge with encapsulated strains resulted in the greatest protection efficacy. The transcriptome of encapsulated M. tuberculosis was similar to that of starvation, hypoxia, stationary phase, or nonreplicating persistence. Conclusions The presence of detergent in growth media and a capsule on BCG were associated with differences in the outcome of vaccination, implying that these are important variables in immunological studies.

Background Many studies have documented lower vaccine efficacy among children in low-income countries, compared with their counterparts in high-income countries. This disparity is especially apparent with respect to oral vaccines such as rotavirus and oral polio vaccines. One potential contributing factor is the presence of maternal antenatal helminth infections, which can modulate the infant's developing immune system. Methods Using a multiplex immunoassay, we tested plasma immunoglobulin A (IgA) or immunoglobulin G (IgG) levels specific for antigens in 9 routinely administered childhood vaccines among 1639 children aged approximately 13 months enrolled in the ECUAVIDA (Ecuador Life) birth cohort study in Ecuador. We compared vaccine responses in 712 children of mothers who tested positive for helminth infections in the last trimester of pregnancy to responses in 927 children of mothers without helminth infection. Results Plasma IgA levels specific for antigens in rotavirus vaccine and oral polio vaccine containing poliovirus serotypes 1 and 3 were all significantly higher in children of helminth-infected mothers, compared with children of uninfected mothers. Plasma IgG levels specific for diphtheria, tetanus, pertussis, measles, rubella, and Haemophilus influenzae type b vaccine antigens were comparable between the 2 groups. Conclusions Antenatal maternal helminth infections were not associated with reduced antibody responses to infant vaccines, but rather with modestly increased IgA responses to oral vaccines.

BACKGROUND Human immunodeficiency virus (HIV)-exposed infants are at increased risk of invasive Group B Streptococcus (GBS) disease; however, the reason for this increased susceptibility has not been characterized. METHODS We compared GBS capsular and surface-protein maternal immunoglobin G antibody concentrations and cord-maternal ratios between HIV-infected and HIV-uninfected mother-newborn dyads. RESULTS Median capsular antibody concentrations (µg/mL) were lower in HIV-infected than HIV-uninfected women for serotypes Ib (P = .033) and V (P = .040); and for pilus island (PI)-1 (P = .016), PI-2a (P = .015), PI-2b (P = .015), and fibrinogen-binding protein A (P < .001). For serotypes Ia and III, cord-maternal ratios were 37.4% (P < .001) and 32.5% (P = .027) lower in HIV-infected compared to HIV-uninfected mother-newborn dyads. The adjusted odds of having capsular antibody concentration ≥2 µg/mL when comparing HIV-infected to -uninfected women were 0.33 (95% confidence interval [CI], .15-.75) and 0.34 (95% CI, .12-1.00) for serotypes Ia and III, respectively. Antibody levels and cord-maternal ratios were independent of CD4(+) lymphocyte counts or HIV-1 viral load. CONCLUSIONS The lower GBS antibody concentrations and reduced transplacental antibody transfer in HIV-infected women, which likely contribute to their infants being at heightened susceptibility for invasive GBS disease, could possibly be mitigated by vaccination with a GBS conjugate vaccine currently under clinical development.

Two hundred twenty-one Gambian children vaccinated previously with one, two, or three doses of a meningococcal conjugate vaccine or two doses of polysaccharide vaccine before the age of 6 months were revaccinated at the age of 18-24 months with either meningococcal polysaccharide, conjugate, or inactivated polio vaccines. Children who had previously received one, two, or three doses of conjugate vaccine had significantly (P < .001) higher anti-group C meningococcal antibody levels following revaccination than did children vaccinated with a polysaccharide vaccine for the first time. Children vaccinated previously with two doses of polysaccharide vaccine had a lower group C antibody response than did control children. Group A antibody responses following revaccination of children who had previously received polysaccharide or conjugate vaccine were not significantly higher than those in control children. Thus, immunologic memory was probably induced by the group C but not by the group A component of the conjugate vaccine.

Transplacental transfer of specific IgG antibodies was studied in 46 pairs of human immunodeficiency virus type 1 (HIV-1)-seropositive women and their neonates and in 53 pairs of healthy HIV-seronegative mothers and their newborns. Neonatal and maternal sera were assessed by nephelometry for total levels of serum IgG and by ELISA for IgG antibodies to herpes simplex virus (HSV), varicella-zoster virus (VZV), measles virus, tetanus toxoid, streptolysin O, and Streptococcus pneumoniae capsular antigens. Placental transfer of IgG antibodies to VZV, tetanus toxoid, measles, streptolysin O, and S. pneumoniae was decreased by maternal HIV infection. Maternal levels of total IgG had an independent effect on transfer of antibodies to HSV, VZV, measles, and S. pneumoniae. Neonatal antibody levels to tetanus toxoid, measles, and S. pneumoniae were significantly lower in the HIV group. Both maternal hypergammaglobulinemia and maternal HIV infection may contribute to these low antibody levels at birth and thus lead to early infection in this high-risk population.

The effects of age, sex, and possible prior exposure to serogroup C meningococci on group C-specific antibody levels (total and functional) were examined in 2- to 19-year-olds just before and 1 and 12 months after immunization with divalent (groups A + C) meningococcal capsular polysaccharide vaccine. Only age was found to have a significant effect on antibody levels. At 1 month, only 50% of 2- to 6-year-olds had detectable serum bactericidal antibody, in contrast to 84.1% and 96.3% of 9- to 12- and 13- to 19-year-olds, respectively. By 12 months, only 20%, 40.9%, and 53.8% of subjects in these age groups had serum bactericidal antibody, suggesting that current meningococcal C polysaccharide vaccines provide only short-term protection. However, the drop in total specific antibody levels (by EIA) was less pronounced. Persistence of antibodies detectable by EIA (but not serum bactericidal antibodies) suggests that this vaccine may also give rise to antibodies of low affinity or directed to nonfunctional (nonprotective) epitopes (or both).

Healthy adults > or = 50 years old were immunized with either pentavalent Corynebacterium diphtheriae C7 (beta197) cross-reactive material (CRM197) protein-conjugated pneumococcal vaccine (CV) containing 10 microgram each of capsular oligosaccharides from serotypes 6B, 14, 18C, 19F, and 23F or with licensed (23-valent, 25 microgram/serotype) pneumococcal polysaccharide vaccine (PV). Adverse reactions, predominantly local in nature, occurred in 20 of 23 CV recipients versus 13 of 23 PV recipients (P

Antibodies to pneumococcal capsular polysaccharides were measured by EIA in acute- and convalescent-phase nasopharyngeal aspirates from 120 children with acute otitis media. Nasopharyngeal IgM- and IgG-class antibodies were rare, whereas IgA was detected more often, occurred independently from serum IgA, and correlated with the presence of the secretory component in pneumococcal antibody, indicating local production of IgA. Thirty-four percent of the children with pneumococci in middle ear fluid developed a nasopharyngeal IgA response to the polysaccharide pool of serotypes 6B, 14, 19F, and 23F compared with 7% of the children with pneumococci only in the nasopharynx or not found at all (P = .004). The responses were observed in children of all ages, the youngest 6 months of age. This supports the hypothesis that mucosal immunity to bacterial polysaccharides matures earlier than systemic immunity.

The recent recognition of type V strains as a frequent cause of group B streptococcal (GBS) infection in both infants and adults prompted investigation of an effective vaccine against these organisms. Purified GBS type V polysaccharide was covalently linked to tetanus toxoid to form a type V polysaccharide-tetanus toxoid conjugate vaccine. The conjugate elicited type V polysaccharide-specific IgG antibodies in rabbits, while unconjugated type V polysaccharide did not. Conjugate-induced rabbit antibodies were opsonic in vitro and protected mice against challenge with type V GBS. Efficacy of the conjugate vaccine also was demonstrated in a maternal vaccination/neonatal challenge model in mice. A GBS type V polysaccharide-tetanus toxoid conjugate is an effective immunogen in animal models and may be a useful component for inclusion in a multivalent GBS vaccine for human use.

Conjugate vaccines against Haemophilus influenzae type b (Hib) may modify Hib pharyngeal colonization. Hib colonization was compared in 371 infants and their families. In Oxfordshire, infants received PRP-T (polyribosylribitol phosphate conjugated to tetanus toxoid) and in Buckinghamshire they did not (controls). Infants were followed at 6, 9, and 12 months of age. Also, 6 unvaccinated Hib carriers were vaccinated and followed for 6 weeks. Hib acquisition was lower in vaccinees than controls (P < .01). During surveillance, 1.5% of vaccinees and 6.3% of controls carried Hib (P = .04). Among those with family Hib exposure, the carriage rates were 8.7% and 38.5% (P = .07), respectively. Hiv carriage rates were lower among vaccinees' unvaccinated siblings. Giving conjugate vaccine to a child carrying Hib did not rapidly terminate carriage. Thus, a primary means by which herd immunity to Hib is induced in a vaccinated population may be through reduction or delay in the initial acquisition of Hib.

Vibrio vulnificus produces a capsular polysaccharide (CPS) that is essential for virulence. CPS from V. vulnificus clinical strain MO6-24 has been purified and the structure determined. In preliminary screening with antisera raised to MO6-24 CPS, 4 (19%) of 21 clinical isolates (including MO6-24), but none of 67 environmental V. vulnificus isolates, agglutinated with anti-MO6-24 antisera (P = .003). CPS was isolated from a subset of 12 clinical and 7 environmental isolates and analyzed by high-performance anion-exchange chromatography and one-dimensional nuclear magnetic resonance. MO6-24 and 1 other serologically positive strain had identical CPS structures; the other 2 serologically positive strains had substitutions in two of four sugar residues. Thirteen other capsular types were identified among the remaining 15 strains from which CPS was extracted.

Haemophilus influenzae type b (Hib) conjugate vaccines reduced oropharyngeal carriage of Hib among children in Finland and the United States. To study the mechanisms of this reduction, a colonization model in infant rats with passively administered antibodies was developed. Of the pups, 94% were colonized 48 h and 64% 7 days after intranasal inoculation with approximately 2500 cfu of Hib. Intranasally administered anti-Hib antibodies, including human IgG and both serum and secretory IgA (sIgA) as well as murine monoclonal anti-Hib capsular polysaccharide (PS) of IgG1 isotype, given simultaneously with, before, or after bacteria, significantly reduced nasopharyngeal colonization by Hib. Hib colonization was also significantly reduced when the antibodies were given intraperitoneally, with a resultant anti-Hib PS serum concentration of > or = 7 micrograms/mL. Thus, anti-Hib PS antibodies, both sIgA and IgG, can function on the mucosal surface and prevent colonization.

The serum antibody response to the capsular polysaccharide of Haemophilus influenzae type b (Hib) was studied in 30 children aged 1 day-5 years with invasive Hib infections. From each child, serum was obtained 0-2 days, 5-11 days, 1 month, and 6-12 months after onset of symptoms. Total antibodies were determined with RIA and isotypes with ELISA. Only 2 children had antibody levels above the estimated protective level (0.15 microgram/mL) in the first serum sample. The antibody response was age dependent with wide individual variations. Children > or = 2 years had increases in IgG, IgM, and IgA antibodies with predominance of IgG. The initial IgG response was IgG1 and IgG2 with predominance of IgG1. In the last serum sample, IgG1 antibodies had decreased while IgG2 antibodies remained unchanged. Only 2 of 7 children < 1 year had a detectable antibody response. The correlation coefficient for total antibodies compared with the sum of IgG, IgM, and IgA was .88 (P < .0001) and for IgG compared with the sum of IgG1 and IgG2 was .97 (P < .0001).

Phagocytosis may be important in clearing Haemophilus influenzae from the bloodstream. To define the effect of type b capsule on phagocytosis, binding and ingestion by macrophages was measured for 5 isogenic sets of capsule-sufficient strains (clinical isolates and type b transformants of capsule-deficient mutants) and capsule-deficient mutants (strains lacking a 9-kb EcoRI fragment of chromosomal DNA associated with type b capsule expression). Capsule-sufficient strains were not bound in the absence of serum, whereas capsule-deficient strains were bound and ingested (1.8-5.1 organisms/macrophage; 59%-97% ingested). In the presence of nonimmune serum, capsule-sufficient strains were largely bound but not ingested (4.7-7.2 organisms/macrophage; 7%-21% ingested), whereas capsule-deficient strains were nearly all ingested (6.2-10.5 organisms/macrophage; 93%-97% ingested). Strains resisting ingestion caused persistent bacteremia 24 h after intravenous challenge in mice and were more likely than readily ingested strains to cause persistent bacteremia or death in infant rats. Thus, type b capsule inhibits ingestion by macrophages; resistance to ingestion may be an important virulence determinant of type b organisms.

Prospective surveillance of Haemophilus influenzae type b (Hib) disease has been done since 1981 in two high-risk populations, White Mountain Apaches and Navajos. The attack rate in children less than 5 years of age is 5-10 times higher than in the general US population. Three vaccines were evaluated. Unconjugated Hib capsular polysaccharide produced lower antibody responses in 18- and 24-month-old Apache infants than in white infants. HbOC (Hib oligosaccharide covalently linked to the nontoxic mutant diphtheria toxin CRM197) produced low antibody responses in Navajo infants after one or two doses but induced responses similar to those in whites after three doses. The responses of 18-month-old Navajos to HbOC were lower than those of whites, but most achieved protective levels. PRP-OMP (Hib capsular polysaccharide linked to the outer membrane protein complex of Neisseria meningitidis) produced good immune responses in 2-month-old Navajo and Apache infants after a single dose. This vaccine was greater than 90% efficacious in protecting Navajo infants from Hib disease when given at 2 and 4 months of age. Even a single dose achieved a high protective efficacy.

A human hyperimmune globulin termed bacterial polysaccharide immune globulin (BPIG) has been prepared from plasma donors immunized with Haemophilus influenzae type b (Hib), pneumococcal, and meningococcal vaccines. At a dose of 0.5 ml/kg, BPIG increased levels of antibody to Hib by greater than 0.15 microgram/ml within 4-6 h and by 2-4 micrograms/ml at 72 h. Thereafter, antibody declined, with a mean half-life of 27 days. BPIG treatment of Apache infants did not impair their active antibody responses to concurrently administered diphtheria-tetanus-pertussis or Hib oligosaccharide-diptheria CRM197 conjugate vaccines. In high-risk Apache infants, BPIG given at 2, 6, and 10 months of age provided significant protection from invasive Hib infection during infancy. Thus, BPIG may have utility in the prevention of Hib infections in high-risk patients who cannot be immunized adequately with Hib conjugate vaccines.

The molecular basis of central nervous system invasiveness by Haemophilus influenzae has been studied by using genetically defined mutants and in vivo and in vitro model systems. Capsular polysaccharide and lipopolysaccharide are important microbial determinants of the ability of H. influenzae to traverse the nasopharynx and localize in the cerebrospinal fluid and meninges after bacteremia. The genes for type b capsule confer greater invasive potential than do those for other capsular polysaccharides, although the molecular basis for this is not understood. Mutants have also indicated the role of lipopolysaccharide in enhancing the efficiency of bacterial translocation from the nose to the blood and in facilitating intravascular survival. Organisms that localize successfully in the blood and central nervous system are the progeny of a small fraction of the original challenge inoculum, often a single bacterium.

In Haemophilus influenzae type b (Hib) strains the cap locus with very few exceptions contains an unstable direct repeat of approximately 17 kb of DNA flanking an approximately 1-kb bridge region containing the gene bexA. Each repeat contains genes necessary for polysaccharide synthesis, export, and surface expression, with BexA a critical component of the polysaccharide exporter. Only rare Hib strains have been identified in which cap lacks a direct repeat, though this is the norm for non-b serotypes. Examination of the ends of this single-copy locus shows that cap has the structure of a compound transposon: Copies of the insertion element IS1016 flank the gene cluster. This gives strains the capacity to amplify genes at cap by unequal homologous recombination. The cap duplication in Hib strains--subserving augmented production of polysaccharide--has apparently arisen in this way and become fixed in the population through deletion of one copy of bexA.

The relationships among capsular type, protein type, and penicillin resistance for capsular group 9 Streptococcus pneumoniae collected in northwestern Canada between 1974 and 1987 were examined. The group 9 relatively penicillin-resistant (RPR) isolates were of the rare 9L capsular type. Of 47 penicillin-susceptible (PS) group 9 isolates that were typed for capsule, only 1 was 9L. Among 29 PS group 9 isolates that were protein typed, 9 protein types were observed. Of the 70 RPR isolates, 51 were protein type P23, 1 was P19, and 18 could not be typed (P0). Protein types P23 differed from P0 by a single epitope on pneumococcal surface protein A. These results suggest that the Canadian P23 and P0 capsular group 9 isolates are likely subclones of a primordial 9L RPR strain.

Contributions to science and to the practice of medicine are built on the shoulders of our predecessors. For us, the shoulders of Dr. Maxwell Finland were singularly broad and strong: In addition to his skills as a physician and a teacher, he was a visionary and a scientist. Dr. Finland started his career by caring for and studying patients with pneumooccal pneumonia [1,2]. He realized the need for understanding the immunologic properties of the pneumococcus capsular polysaccharides (CP) and their relation to clinical disease caused by this pathogen. Some of his contributions that guided our efforts to develop effective vaccines for prevention of systemic infections due to capsulated bacterial pathogens are cited in table 1 [3-16]. Our main interest has been toward preventing meningitis and other systemic infections caused by Haemophilus influenzae type b (Hib). Progress by us and by other laboratories toward developing Hib conjugates has been rapid, and vaccines manufactured by three companies have been licensed recently for children ^18 months of age. The advent of Hib conjugates licensed for universal immunization of infants, administered concurrently with diphtheria and tetanus toxoids and pertussis vaccine (DTP), is imminent. We are confident that chemists and engineers will continue to improve these first Hib conjugates and that even more effective products will be available soon. Accordingly, in addition to reviewing our contributions and those of our colleagues with these new Hib vaccines, we will illustrate how the development of polysaccharide-protein conjugates may provide opportunities for studying the pathogenesis of other bacterial diseases and ultimately for preventing them through new vaccines. Surface polysaccharides may serve both as virulence factors and as protective antigens for bacteria whose invasion of the blood is their primary pathogenic event [17]. These

From 1969 to 1988, 8 cases of systemic Haemophilus influenzae type b (Hib) disease occurred among 5288 patients with cancer. For the first 4 years of life, systemic Hib disease was significantly greater in leukemic children than in the general population (606/100,000 vs. 90/100,000, respectively). Fifty children aged 2-6 years with acute leukemia were vaccinated with a Hib conjugate vaccine, ProHibit. The overall response rate was 50%; however, 75% of children receiving leukemic therapy for less than 12 months responded versus 18% of those treated longer. After vaccination, the geometric mean antibody concentration was 7.2 micrograms/ml, appreciably lower than for normal children of similar ages. After 12 months, the geometric mean antibody concentration had declined to 0.35 micrograms/ml, and 75% of subjects had antibody levels greater than or equal to 0.15 micrograms/ml. A booster dose for unsuccessfully vaccinated subjects was of minimal benefit. Children with acute leukemia in remission who were treated according to the leukemia therapy protocol of St. Jude Children's Research Hospital had a good likelihood of responding to the conjugate Hib vaccine if administered within a year of initiation of chemotherapy.

The occurrence of Haemophilus influenzae type b capsular polysaccharide antigenemia and antigenuria following immunization was studied in 48 healthy 2-month-old infants. Each received a conjugate vaccine consisting of H. influenzae type b capsular polysaccharide covalently linked to Neisseria meningitidis serotype b outer membrane protein at 2 and 4 months of age. Infants were alternated at enrollment for collection of blood and urine after either the first or second dose. Specimens were obtained "early" (2-3 days) after immunization and "late" (7 days) after immunization and assayed for antigen. Antigen was detected in the serum of 3 (6%) of 48 infants, uniformly in the "early" specimen obtained after the first dose of vaccine. Antigenuria occurred in 37 (80%) of 46 infants; for greater than or equal to 7 days in 12 (26%). Antigenuria was frequent after administration of the vaccine but antigenemia was not. These data should be considered in the evaluation of an infant with suspected H. influenzae type b invasive disease.

Antibodies against nonencapsulated Haemophilus influenzae and Moraxella (Branhamella) catarrhalis were measured by ELISA in paired sera from 158 adult patients with pneumonia. A mixture of 10 clinical isolates of each species was used as antigen. Eleven patients (7%) showed significant increases in antibody to H. influenzae. In 3 of them, the organism was isolated from transtracheal aspirate and in another 7 from sputum, nasopharynx, or both. Six patients with nonencapsulated H. influenzae in transtracheal aspirate cultures did not show any antibody increase. Six patients had significant increases in antibody to M. catarrhalis. The organism was isolated in transtracheal aspirates from 1 of them and in sputum and nasopharynx (or both) from another 3. Two patients with M. catarrhalis in transtracheal aspirate cultures showed no antibody response. In conclusion, the serologic methods increased the possibility to diagnose infections caused by the two agents but had low sensitivity.

The interference of antibodies to pneumococcal cell wall polysaccharide (CWPS) in the measurement of antibodies to capsular polysaccharides in children was assessed after vaccination with pneumococcal polysaccharide vaccine. ELISAs were developed to measure IgG subclasses specific for pneumococcal types 3, 6, 19, and 23 and CWPS. Analysis of antibody levels to all four capsular polysaccharides was affected by the presence of antibodies to CWPS, and their removal altered both anti-capsular polysaccharide antibody levels and the interpretation of responses to the vaccine. Thus, it is likely that CWPS contaminating pure capsular polysaccharide reagents used in most standard immunoassays is responsible for falsely elevated measurements of antibodies to capsular polysaccharide and the incorrect assessment of anti-pneumococcal antibody status in childhood.

Maternal immunization with the capsular polysaccharide (PRP) vaccine of Haemophilus influenzae type b has been shown to extend the time that protective levels of maternal antibody are detected in infants. In a randomized, blinded trial, PRP or placebo was administered uneventfully to 213 women in the third trimester of pregnancy. Infants born to PRP recipients had significantly higher levels of antibody to PRP than did infants born to placebo recipients: 2.73 micrograms/ml compared with 0.33 microgram/ml. It was estimated that infants of mothers who received the PRP vaccine would be protected for an average of 4 months compared to an average of only 2 months for those of mothers who received placebo. Infants were followed for invasive H. influenzae type b disease through the first year of life; none was detected.

The two isotypes of the fourth complement component are C4A and C4B. C4B forms ester bonds more efficiently than C4A and so, in theory, is more likely than C4A to bind to polysaccharide capsules of encapsulated bacteria. Two studies have reported homozygous C4B deficiency in patients with meningitis or bacteremia caused by encapsulated organisms. In the present study the association between C4B deficiency and these disorders was evaluated in four groups: patients with bacteremia, those with meningitis, those who developed Haemophilus influenzae type b (Hib) disease after Hib polysaccharide vaccination, and patients less than 1 year old with meningitis. Healthy adults served as controls. Of the 257 patients, 2.3% had homozygous C4B deficiency compared with 3.7% of 349 controls. According to these data, there is no increase in homozygous C4B deficiency among patients with bacteremia or meningitis caused by encapsulated bacteria.

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.

The functional affinity, or avidity, of antibody to the capsular polysaccharide of Haemophilus influenzae (Hib-PS) was measured in serum samples from 12 adult male subjects before and after immunization with Hib-PS vaccine. Mean avidity increased from 0.74 nM-1 to 1.5 nM-1 after immunization (P less than .05, paired Student's t test). The Bureau of Biologics reference antiserum had an avidity constant of 12 nM-1, which was the highest of all 25 serum samples studied.

Levels of antibody to the K1 polysaccharide capsule were examined in sera from patients naturally infected with K1-positive Escherichia coli, in sera from volunteers vaccinated with a group B meningococcal vaccine, in immune globulin prepared for intravenous use, and in a preparation of murine IgM monoclonal antibody to group B meningococci. In a phagocytic assay, the monoclonal antibody in mouse ascites fluid killed K1-positive E. coli to a final dilution of 1:250,000 (48 ng of antibody protein/ml); no killing was observed with any of the other antibody sources. This monoclonal antibody, which required human complement and exhibited a prozone when high concentrations of antibody (greater than 6 micrograms/ml) were used, killed all K1-positive strains but none of the K1-negative strains of E. coli tested. Levels of K1-binding antibody in the sera of vaccinated volunteers exceeded antibody levels resulting from natural infection or present in commercially prepared immunoglobulin and were less than those obtained in mouse ascites fluid containing the monoclonal antibody.

The antibody responses of children immunized with Haemophilus influenzae type b polysaccharide vaccine were examined in relation to the absence or presence of the Km(1) or G2m(23) immunoglobulin allotype. Ninety-seven children, 12-83 months of age, were immunized. Sera were obtained before immunization and two months later. Total serum antibody to the type b capsule was detected by a radioactive antigen-binding assay. IgG and IgM antibody responses were measured by enzyme-linked immunosorbent assay. Antibody responses to the type b capsule were more than threefold higher in blacks with the Km(1) immunoglobulin allotype compared with those in blacks lacking this allotype (P less than .02). The isotype affected was IgG (P less than .01) and not IgM. Serum concentrations of IgG2, but not of IgG1, also were higher in blacks with Km(1) (P less than .003). In whites there were no significant differences in the total or IgG-specific antibody responses to the type b capsule in relation to the Km(1) or G2m(23) allotype.

Hemophilus influenzae type b polysaccharide-Neisseria meningitidis group B outer membrane protein complex vaccine was administered in a single dose to 38 children ages 24-53 mo (group 1) and to 78 children ages 12-23 mo (group 2) and in two doses to 84 children ages 2-11 mo (group 3). The geometric mean concentration of the capsular antibody before and after the vaccine regimen, respectively, were 0.35 microgram/ml and 12.59 micrograms/ml in group 1, 0.18 microgram/ml and 4.79 microgram/ml in group 2, and 0.15 microgram/ml and 3.80 micrograms/ml in group 3. After completing the vaccine regimen, concentrations of capsular antibody were greater than or equal to 0.15 microgram/ml in 199 (99.5%) of the 200 children and greater than or equal to 1.0 microgram/ml in 168 (84%) of the children. There were no serious and few minor adverse reactions to the vaccine. This vaccine is immunogenic in infants and young children.

Thirty-one type II and eight nontypable group B streptococcal isolates were categorized by the presence of the trypsin-resistant and trypsin-sensitive components of the Ibc protein antigen and studied for opsonization differences by using polymorphonuclear leukocyte chemiluminescence (CL). Type II strains varied in their ease of opsonization: strains possessing both components of the Ibc protein elicited a significantly lower mean CL peak (P less than or equal to .05) and a smaller CL integral (P less than or equal to .01) than did type II strains lacking both components or strains lacking type polysaccharide antigen but possessing the Ibc protein antigen. These strain differences were seen consistently with different sera and were also observed in an opsonophagocytic killing assay. Differences in opsonizing ability and bacterial killing were found for three standard test sera but could not be related to the concentration of type-specific antibody to capsular polysaccharide antigen. Our studies suggested that the Ibc protein antigen was one factor that contributed to the resistance to opsonization of strains of type II group B streptococci.