Amber J. Thompson

Maintenance of Immune Response throughout Childhood following Serogroup C Meningococcal Conjugate Vaccination in Early Childhood

ABSTRACT The objectives of this study were to evaluate the kinetics of antibody decline through childhood in a longitudinal study of a single cohort following serogroup C meningococcal (MenC) vaccine immunization in early childhood and to calculate the proportion of 11 to 13 year olds with protective levels of bactericidal antibody 10 years after immunization. United Kingdom children aged 11 to 13 years in 2010 who had previously taken part in a longitudinal study at the Oxford Vaccine Group had blood samples drawn between 2001 and 2010. Sera from each time point were analyzed for the MenC serum bactericidal antibody titer using a baby rabbit complement (rSBA) assay. The median age at MenC immunization was 21 months (range, 1 year 3 months to 3 years 9 months). The MenC rSBA geometric mean titer (GMT) at age 3.5 to 5 years was 8.0 (95% confidence interval, 6.5 to 9.9; n = 287). By age 11.5 to 13.5 years, the rSBA GMT had declined to 3.3 (2.5 to 4.4; n = 98). The percentage of children with rSBA titers of ≥1:8 (the threshold for protection) also declined from 38% (35% to 41%) to 15% (12% to 19%). We concluded that MenC rSBA titers wane rapidly following vaccination in early childhood and continue to decline into the second decade of life. Since nasopharyngeal colonization in adolescents probably provides the major reservoir for MenC in the population, declining immunity in this cohort is of concern. Sustaining high levels of antibody through booster vaccination in this cohort is likely necessary to avoid a resurgence of disease in the decade ahead.

A novel meningococcal outer membrane vesicle vaccine with constitutive expression of FetA: A phase I clinical trial

Summary Objectives Outer membrane vesicle (OMV) vaccines are used against outbreaks of capsular group B Neisseria meningitidis (MenB) caused by strains expressing particular PorA outer membrane proteins (OMPs). Ferric enterobactin receptor (FetA) is another variable OMP that induces type-specific bactericidal antibodies, and the combination of judiciously chosen PorA and FetA variants in vaccine formulations is a potential approach to broaden protection of such vaccines. Methods The OMV vaccine MenPF-1 was generated by genetically modifying N. meningitidis strain 44/76 to constitutively express FetA. Three doses of 25 μg or 50 μg of MenPF-1 were delivered intra-muscularly to 52 healthy adults. Results MenPF-1 was safe and well tolerated. Immunogenicity was measured by serum bactericidal assay (SBA) against wild-type and isogenic mutant strains. After 3 doses, the proportion of volunteers with SBA titres ≥1:4 (the putative protective titre) was 98% for the wild-type strain, and 77% for the strain 44/76 FetAonPorAoff compared to 51% in the strain 44/76 FetAoffPorAoff, demonstrating that vaccination with MenPF-1 simultaneously induced FetA and PorA bactericidal antibodies. Conclusion This study provides a proof-of-concept for generating bactericidal antibodies against FetA after OMV vaccination in humans. Prevalence-based choice of PorA and FetA types can be used to formulate a vaccine for broad protection against MenB disease.

Multi-component Polymeric System for Tumour Cell-Specific Gene Delivery Using a Universal Bungarotoxin Linker

ABSTRACTPurposeA new universal tool for specific, non-covalent and non-destructive attachment of a recombinant antibody fragment to a polymer-modified adenovirus has been utilised to regulate the tropism of adenoviral gene delivery vector.MethodsWe have prepared a multivalent reactive N-(2-hydroxypropyl)methacrylamide-based copolymer (PHPMA) bearing an α-bungarotoxin-binding peptide (BTXbp). The copolymer was used for covalent surface modification of adenoviral vectors (Ad). The α-bungarotoxin protein (BTX) has a nanomolar binding affinity for BTXbp, allowing non-covalent linkage of BTX fusion proteins. A single chain variable fragment of anti-PSMA antibody bearing BTX (scFv-BTX) binding to the prostate-specific membrane antigen (PSMA) was conjugated with the copolymer-coated adenovirus to enable specific infection of prostate cancer cells via PSMA receptors.ResultsAs shown by ELISA, the copolymer-coated virus exhibited much reduced binding to anti-Ad antibodies. Infection of PC-3 and LNCaP prostate cancer cells was ∼100-fold less efficient with copolymer-coated Ad than with un-modified Ad. Conjugation of scFv-BTX with Ad-PHPMA-BTXbp led to 5–10-fold restoration of infection in PSMA-positive LNCaP cells. In PSMA-negative PC-3 cells, the conjugation of scFv-BTX with Ad-PHPMA-BTXbp gave no enhancement of infection.ConclusionsWe have shown that the presented Ad-PHPMA-BTXbp/scFv-BTX system can be used as a universal tool for a receptor-specific virotherapy.

Effect of cryopreservation of peripheral blood mononuclear cells (PBMCs) on the variability of an antigen-specific memory B cell ELISpot

The ELISpot assay is used in vaccine studies for the quantification of antigen-specific memory B cells (BMEM), and can be performed using cryopreserved samples. The effects of cryopreservation on BMEM detection and the consistency of cultured ELISpot assays when performed by different operators or laboratories are unknown. In this study, blood was taken from healthy volunteers, and a cultured ELISpot assay was used to count BMEM specific for 2 routine vaccine antigens (diphtheria and tetanus toxoid). Results were assessed for intra- and inter-operator variation, and the effects of cryopreservation. Cryopreserved samples were shipped to a second laboratory in order to assess inter-laboratory variation. BMEM frequencies were very strongly correlated when comparing fresh and frozen samples processed by the same operator, and were also very strongly correlated when comparing 2 operators in the same laboratory. Results were slightly less consistent when samples were processed in different laboratories but correlation between the 2 measurements was still very strong. Although cell viability was reduced in some cryopreserved samples due to higher temperatures during transportation, BMEM could still be quantified. These results demonstrate the reproducibility of the ELISpot assay across operators and laboratories, and support the use of cryopreserved samples in future BMEM studies.

Evaluation of the Induction of Immune Memory following Infant Immunisation with Serogroup C Neisseria meningitidis Conjugate Vaccines - Exploratory Analyses within a Randomised Controlled Trial

Aim We measured meningococcal serogroup C (MenC)-specific memory B-cell responses in infants by Enzyme-Linked Immunospot (ELISpot) following different MenC conjugate vaccine schedules to investigate the impact of priming on immune memory. Methods Infants aged 2 months were randomised to receive 1 or 2 doses of MenC-CRM197 at 3 or 3 and 4 months, 1 dose of MenC-TT at 3 months, or no primary MenC doses. All children received a Haemophilus influenzae type b (Hib)-MenC booster at 12 months. Blood was drawn at 5, 12, 12 months +6 days and 13 months of age. Results Results were available for 110, 103, 76 and 44 children from each group respectively. Following primary immunisations, and prior to the 12-month booster, there were no significant differences between 1- or 2-dose primed children in the number of MenC memory B-cells detected. One month following the booster, children primed with 1 dose MenC-TT had more memory B-cells than children primed with either 1-dose (p = 0.001) or 2-dose (p<0.0001) MenC-CRM197. There were no differences in MenC memory B-cells detected in children who received 1 or 2 doses of MenC-CRM197 in infancy and un-primed children. Conclusions MenC-specific memory B-cell production may be more dependent on the type of primary vaccine used than the number of doses administered. Although the mechanistic differences between MenC-CRM197 and MenC-TT priming are unclear, it is possible that structural differences, including the carrier proteins, may underlie differential interactions with B- and T-cell populations, and thus different effects on various memory B-cell subsets. A MenC-TT/Hib-MenC-TT combination for priming/boosting may offer an advantage in inducing more persistent antibody. Trial Registration EU Clinical Trials Register 2009-016579-31 ClinicalTrials.gov NCT01129518

Randomized clinical trial to evaluate the immunogenicity of quadrivalent meningococcal conjugate and polysaccharide vaccines in adults in the United kingdom

ABSTRACT Meningococcal conjugate vaccines are today successfully deployed in universal programs for children and adolescents in different geographic regions to control meningitis and septicemia. However, in adults, the advantages of these conjugates over the older polysaccharide vaccines are less clear. In this randomized clinical trial, we demonstrated that both conjugate and polysaccharide quadrivalent meningococcal vaccines elicit protective antibody responses in adults aged 18 to 70. (This study has been registered at www.clinicaltrials.gov under registration no. NCT00901940.)

Humoral and cellular immunity to RSV in infants, children and adults.

BACKGROUND Respiratory syncytial virus (RSV) causes respiratory disease throughout life. Here we report differences in naturally acquired immunity with age and presumed exposure. METHODS A longitudinal, non-interventional, observational study was performed in healthy adults (20 paediatric healthcare workers and 10 non-healthcare workers), children (10 aged 3-6 years) and infants (5 aged 2-4 months and 20 aged 6-12 months). Blood samples were analysed for RSV-neutralising antibody titre, F/Ga/Gb-specific antibody titres, F-specific IgG/IgA memory B-cell frequencies and T-cell production of IFNγ, IL-4, IL-13 and IL-17. RESULTS Serum G-specific antibody titres were significantly lower in infants and children than adults. However, serum titres of F-specific and RSV-neutralising antibody and IFNγ-producing T-cell frequencies were low or absent in the infants, but comparable between children and adults. Interestingly, F-specific memory IgA B-cells could not be detected in paediatric samples and in samples from non-healthcare workers, but recordable IgA memory B-cells were found in 9/18 paediatric healthcare workers and 2/8 non-healthcare workers at the end of the RSV season. These responses waned 4-6 months later. By contrast, F-specific IgG memory B-cells were detectable in samples from all adults without significant variation across time points. T-cells producing IL-4, IL-13 and IL-17 responses were not detectable in peripheral blood from a subset of volunteers. CONCLUSIONS Repeated RSV exposure in early life generates immune responses that are inversely related to frequency of severe disease. Induction of F-specific antibody and cellular immune responses through infant vaccination might help to accelerate the development of protective immune responses at an early age. Clinicaltrials.gov reference NCT01563692 and NCT01640652.