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Development and Qualification of an Opsonophagocytic Killing Assay To Assess Immunogenicity of a Bioconjugated Escherichia coli Vaccine.

ABSTRACT: The global burden of disease caused by extraintestinal pathogenic Escherichia coli (ExPEC) is increasing as the prevalence of multidrug-resistant strains rises. A multivalent ExPEC O-antigen bioconjugate vaccine could have a substantial impact in preventing bacteremia and urinary tract infections. Development of an ExPEC vaccine requires a readout to assess the functionality of antibodies. We developed an opsonophagocytic killing assay (OPA) for four ExPEC serotypes (serotypes O1A, O2, O6A, and O25B) based on methods established for pneumococcal conjugate vaccines. The performance of the assay was assessed with human serum by computing the precision, linearity, trueness, total error, working range, and specificity. Serotypes O1A and O6A met the acceptance criteria for precision (coefficient of variation for repeatability and intermediate precision, ?50%), linearity (90% confidence interval of the slope of each strain, 0.80, 1.25), trueness (relative bias range, -30% to 30%), and total error (total error range, -65% to 183%) at five serum concentrations and serotypes O2 and O25B met the acceptance criteria at four concentrations (the lowest concentration for serotypes O2 and O25B did not meet the system suitability test of maximum killing of ?85% of E. coli cells). All serotypes met the acceptance criteria for specificity (opsonization index value reductions of ?20% for heterologous serum preadsorption and ?70% for homologous serum preadsorption). The assay working range was defined on the basis of the lowest and highest concentrations at which the assay jointly fulfilled the target acceptance criteria for linearity, precision, and accuracy. An OPA suitable for multiple E. coli serotypes has been developed, qualified, and used to assess the immunogenicity of a 4-valent E. coli bioconjugate vaccine (ExPEC4V) administered to humans.

SUBMITTER: Abbanat D

PROVIDER: S-EPMC5717180 | biostudies-literature | 2017 Dec

REPOSITORIES: biostudies-literature

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Development and Qualification of an Opsonophagocytic Killing Assay To Assess Immunogenicity of a Bioconjugated Escherichia coli Vaccine.

Abbanat Darren D Davies Todd A TA Amsler Karen K He Wenping W Fae Kellen K Janssen Sarah S Poolman Jan T JT van den Dobbelsteen Germie P J M GPJM

Clinical and vaccine immunology : CVI 20171205 12

The global burden of disease caused by extraintestinal pathogenic <i>Escherichia coli</i> (ExPEC) is increasing as the prevalence of multidrug-resistant strains rises. A multivalent ExPEC O-antigen bioconjugate vaccine could have a substantial impact in preventing bacteremia and urinary tract infections. Development of an ExPEC vaccine requires a readout to assess the functionality of antibodies. We developed an opsonophagocytic killing assay (OPA) for four ExPEC serotypes (serotypes O1A, O2, O6 ...[more]

PMID: 28971965

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Project description:IntroductionEnterotoxigenic Escherichia coli (ETEC) is a common cause of infectious diarrhoea and a leading cause of morbidity and mortality in children living in resource-limited settings. It is also the leading cause of travellers' diarrhoea among civilian and military travellers. Its dual importance in global public health and travel medicine highlights the need for an effective vaccine. ETEC express colonization factors (CFs) that mediate adherence to the small intestine. An epidemiologically prevalent CF is coli surface antigen 6 (CS6). We assessed the safety and immunogenicity of a CS6-targeted candidate vaccine, CssBA, co-administered intramuscularly with the double-mutant heat-labile enterotoxin, dmLT [LT(R192G/L211A)].MethodsThis was an open-label trial. Fifty subjects received three intramuscular injections (Days 1, 22 and 43) of CssBA alone (5 µg), dmLT alone (0.1 µg) or CssBA (5, 15, 45 µg) + dmLT (0.1 and 0.5 µg). Subjects were actively monitored for adverse events for 28 days following the third vaccination. Antibody responses (IgG and IgA) were characterized in the serum and from lymphocyte supernatants (ALS) to CS6 and the native ETEC heat labile enterotoxin, LT.ResultsAcross all dose cohorts, the vaccine was safe and well-tolerated with no vaccine-related severe or serious adverse events. Among vaccine-related adverse events, a majority (98%) were mild with 79% being short-lived vaccine site reactions. Robust antibody responses were induced in a dose-dependent manner with a clear dmLT adjuvant effect. Response rates in subjects receiving 45 µg CssBA and 0.5 µg dmLT ranged from 50 to 100% across assays.ConclusionThis is the first study to demonstrate the safety and immunogenicity of CssBA and/or dmLT administered intramuscularly. Co-administration of the two components induced robust immune responses to CS6 and LT, paving the way for future studies to evaluate the efficacy of this vaccine target and development of a multivalent, subunit ETEC vaccine.

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Development and Qualification of an Opsonophagocytic Killing Assay To Assess Immunogenicity of a Bioconjugated Escherichia coli Vaccine.

Publications

Development and Qualification of an Opsonophagocytic Killing Assay To Assess Immunogenicity of a Bioconjugated Escherichia coli Vaccine.

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