Immune response to pneumococcal polysaccharides 4 and 14 in elderly and young adults. I Antibody concentrations, avidity and functional activity

Streptococcus pneumoniae is a serious worldwide pathogen and the focus of numerous vaccine development projects. Currently the most widely accepted surrogate marker for evaluating the efficacy of a given vaccine is to utilize ELISA. Measurement of antibody concentration by ELISA without reduction in cross-reactive antibodies causes an overestimation of antibody concentration and therefore protection, this is most notable in the aged, an at risk group for this infection. We compared the immune response to the pneumococcal polysaccharides (PPS) 4 and 14 of 20 young to 20 elderly adults. Pre-and post-vaccination IgG antibody concentrations and antibody avidity against PPS4 and PPS14 were measured using two different enzyme-linked immunosorbant assay (ELISA) absorption protocols. All sera were pre-absorbed with either cell-wall polysaccharide (CPS), or CPS and serotype 22F polysaccharide. Pre- and post-vaccination IgG antibody concentrations for serotype 4, but not 14, were significantly lowered with the additional absorption with serotype 22F polysaccharide in both age groups. Young and elderly demonstrated a significant increase from pre- to post-immunization antibody concentration, using either absorption method; and opsonophagocytic antibody titers in response to both PPS4 and PPS14. The correlation coefficients between ELISA and opsonophagocytic assays were improved by additional absorption with serotype 22F in response to serotype 4, but not serotype 14 in all age groups. Opsonophagocytic antibody titers in a sub-group of elderly (>77 years of age) were significantly lower than the opsonophagocytic antibody concentrations in young adults. These results suggest the importance of eliminating cross-reactive antibodies from ELISA measurements by absorption of serum and an age-related impairment in the antibody response to pneumococcal polysaccharides

Mass Spectrometric Analysis of Multiple Pertussis Toxins and Toxoids

Bordetella pertussis (Bp) is the causative agent of pertussis, a vaccine preventable disease occurring primarily in children. In recent years, there has been increased reporting of pertussis. Current pertussis vaccines are acellular and consist of Bp proteins including the major virulence factor pertussis toxin (Ptx), a 5-subunit exotoxin. Variation in Ptx subunit amino acid (AA) sequence could possibly affect the immune response. A blind comparative mass spectrometric (MS) analysis of commercially available Ptx as well as the chemically modified toxoid (Ptxd) from licensed vaccines was performed to assess peptide sequence and AA coverage variability as well as relative amounts of Ptx subunits. Qualitatively, there are similarities among the various sources based on AA percent coverages and MS/MS fragmentation profiles. Additionally, based on a label-free mass spectrometry-based quantification method there is differential relative abundance of the subunits among the sources

Persistence of serogroup C antibody responses following quadrivalent meningococcal conjugate vaccination in United States military personnel

AbstractSerogroup C meningococcal (MenC) disease accounts for one-third of all meningococcal cases and causes meningococcal outbreaks in the U.S. Quadrivalent meningococcal vaccine conjugated to diphtheria toxoid (MenACYWD) was recommended in 2005 for adolescents and high risk groups such as military recruits. We evaluated anti-MenC antibody persistence in U.S. military personnel vaccinated with either MenACYWD or meningococcal polysaccharide vaccine (MPSV4). Twelve hundred subjects vaccinated with MenACYWD from 2006 to 2008 or MPSV4 from 2002 to 2004 were randomly selected from the Defense Medical Surveillance System. Baseline serologic responses to MenC were assessed in all subjects; 100 subjects per vaccine group were tested during one of the following six post-vaccination time-points: 5–7, 11–13, 17–19, 23–25, 29–31, or 35–37 months. Anti-MenC geometric mean titers (GMT) were measured by rabbit complement serum bactericidal assay (rSBA) and geometric mean concentrations (GMC) by enzyme-linked immunosorbent assay (ELISA). Continuous variables were compared using the Wilcoxon rank sum test and the proportion of subjects with an rSBA titer ≥8 by chi-square. Pre-vaccination rSBA GMT was <8 for the MenACWYD group. rSBA GMT increased to 703 at 5–7 months post-vaccination and decreased by 94% to 43 at 3 years post-vaccination. GMT was significantly lower in the MenACWYD group at 5–7 months post-vaccination compared to the MPSV4 group. The percentage of MenACWYD recipients achieving an rSBA titer of ≥8 decreased from 87% at 5–7 months to 54% at 3 years. There were no significant differences between vaccine groups in the proportion of subjects with a titer of ≥8 at any time-point. GMC for the MenACWYD group was 0.14μg/mL at baseline, 1.07μg/mL at 5–7 months, and 0.66μg/mL at 3 years, and significantly lower than the MPSV4 group at all time-points. Anti-MenC responses wane following vaccination with MenACYWD; a booster dose is needed to maintain protective levels of circulating antibody

Functional Antibodies to the O-Acetylated Pneumococcal Serotype 15B Capsular Polysaccharide Have Low Cross-Reactivities with Serotype 15C▿

The 23-valent pneumococcal polysaccharide (Ps) vaccine offer protection against vaccine serotypes, but its cross-protection against vaccine-related serotypes is variable. We have demonstrated that the functional antibodies to serotype 15B are specific to the O-acetylated 15B-Ps and that they have low cross-reactivity with serotype 15C. Demonstration of functionally cross-reactive antibodies to vaccine-related serotypes is important for surveillance and vaccine development

Assignment of Additional Anticapsular Antibody Concentrations to the Neisseria meningitidis Group A, C, Y, and W-135 Meningococcal Standard Reference Serum CDC1992

We assigned additional enzyme-linked immunosorbent assay antibody concentrations (immunoglobulin G [IgG], IgM, and IgA, and total) to the Neisseria meningitidis standard reference serum CDC1992 for groups Y and W-135 to 12 Centers for Disease Control and Prevention quality control sera. These assignments will supplement previous assignments and will aid in the evaluation of present and developing vaccines

Evaluation of Multiplex Flow Cytometric Opsonophagocytic Assays for Determination of Functional Anticapsular Antibodies to Streptococcus pneumoniae

The determination of functional antipneumococcal capsular polysaccharide antibodies by sequential testing of pre- and postvaccination serum samples one serotype at a time is sample-intensive and time-consuming and has a relatively low throughput. We tested several opsonophagocytic assay (OPA) formats, including the reference killing method, a monovalent bacterium-based flow method, a trivalent bacterium-based flow method, and a tetravalent bead-based flow method using a panel of sera (4 prevaccination and 16 postvaccination, from healthy adults immunized with the 23-valent pneumococcal polysaccharide vaccine). The trivalent and tetravalent methods allow simultaneous measurements of opsonic antibodies to multiple pneumococcal serotypes. The trivalent bacterial-flow OPA had significant correlation to the reference OPA method and to a previously published flow cytometric OPA (r values ranged from 0.61 to 0.91, P < 0.05) for serotypes 4, 6B, 9V, 14, 18C, 19F, and 23F. The tetravalent OPA had significant correlation to all OPA method formats tested (r values from 0.68 to 0.92, P < 0.05) for all seven serotypes tested. This tetravalent OPA is an alternative to other OPA methods for use during vaccine evaluation and clinical trials. Further, the flow cytometric multiplex OPA format has the potential for expansion beyond the current four serotypes to eight or more serotypes, which would further increase relative sample throughput while reducing reagent and sample volumes used