ABSTRACT
Background: Managing blood volumes in pediatric studies is challenging and should be minimized where possible. Results: A sensitive liquid chromatography with tandem mass spectrometry (LC-MS/MS) method was validated and implemented across two phase III global pediatric trials. Two 10-µl aliquots of blood were collected at each time point using the Mitra® device. Concordance between plasma and dried blood was established from older pediatric patients. Incurred sample reanalysis was performed in both studies using the second Mitra tip and acceptance was greater than 83%. Conclusion: The use of microsampling to generate pharmacokinetic data in 2-18-year-old pediatric patients was successfully implemented. Positive feedback was received from clinical sites about the microsampling technique assisting with enrollment of pediatric patients.
Subject(s)
Dried Blood Spot Testing , Tandem Mass Spectrometry , Adolescent , Child , Child, Preschool , Humans , Blood Specimen Collection/methods , Chromatography, Liquid/methods , Dried Blood Spot Testing/methods , Specimen Handling/methods , Tandem Mass Spectrometry/methods , Clinical Trials, Phase III as TopicABSTRACT
Anthrax toxin (ATx) is composed of the binary exotoxins lethal toxin (LTx) and edema toxin (ETx). They have separate effector proteins (edema factor and lethal factor) but have the same binding protein, protective antigen (PA). PA is the primary immunogen in the current licensed vaccine anthrax vaccine adsorbed (AVA [BioThrax]). AVA confers protective immunity by stimulating production of ATx-neutralizing antibodies, which could block the intoxication process at several steps (binding of PA to the target cell surface, furin cleavage, toxin complex formation, and binding/translocation of ATx into the cell). To evaluate ATx neutralization by anti-AVA antibodies, we developed two low-temperature LTx neutralization activity (TNA) assays that distinguish antibody blocking before and after binding of PA to target cells (noncomplexed [NC] and receptor-bound [RB] TNA assays). These assays were used to investigate anti-PA antibody responses in AVA-vaccinated rhesus macaques (Macaca mulatta) that survived an aerosol challenge with Bacillus anthracis Ames spores. Results showed that macaque anti-AVA sera neutralized LTx in vitro, even when PA was prebound to cells. Neutralization titers in surviving versus nonsurviving animals and between prechallenge and postchallenge activities were highly correlated. These data demonstrate that AVA stimulates a myriad of antibodies that recognize multiple neutralizing epitopes and confirm that change, loss, or occlusion of epitopes after PA is processed from PA83 to PA63 at the cell surface does not significantly affect in vitro neutralizing efficacy. Furthermore, these data support the idea that the full-length PA83 monomer is an appropriate immunogen for inclusion in next-generation anthrax vaccines.
