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Clinical assays rapidly predict bacterial susceptibility to monoclonal antibody therapy
Matthew J. Slarve, Neven Bowler, Elizabeth Burk, Jun Yan, Ulrike Carlino-MacDonald, Thomas A. Russo, Brian M. Luna, Brad Spellberg
Matthew J. Slarve, Neven Bowler, Elizabeth Burk, Jun Yan, Ulrike Carlino-MacDonald, Thomas A. Russo, Brian M. Luna, Brad Spellberg
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Resource and Technical Advance Infectious disease

Clinical assays rapidly predict bacterial susceptibility to monoclonal antibody therapy

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Abstract

With antimicrobial resistance (AMR) emerging as a major threat to global health, monoclonal antibodies (MAbs) have become a promising means to combat difficult-to-treat AMR infections. Unfortunately, in contrast with standard antimicrobials, for which there are well-validated clinical laboratory methodologies to determine whether an infecting pathogen is susceptible or resistant to a specific antimicrobial drug, no assays have been described that can inform clinical investigators or clinicians regarding the clinical efficacy of a MAb against a specific pathogenic strain. Using Acinetobacter baumannii as a model organism, we established and validated 2 facile clinical susceptibility assays, which used flow cytometry and latex bead agglutination, to determine susceptibility (predicting in vivo efficacy) or resistance (predicting in vivo failure) of 1 newly established and 3 previously described anti–A. baumannii MAbs. These simple assays exhibited impressive sensitivity, specificity, and reproducibility, with clear susceptibility breakpoints that predicted the in vivo outcomes in our preclinical model with excellent fidelity. These MAb susceptibility assays have the potential to enable and facilitate clinical development and deployment of MAbs that generally target the surface of microbes.

Authors

Matthew J. Slarve, Neven Bowler, Elizabeth Burk, Jun Yan, Ulrike Carlino-MacDonald, Thomas A. Russo, Brian M. Luna, Brad Spellberg

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Figure 3

MAb10 has potent efficacy in in vitro and in vivo assays.

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MAb10 has potent efficacy in in vitro and in vivo assays.
(A) A. baumann...
(A) A. baumannii strain 1127417 was incubated with murine MAb10 (blue peak) or isotype control antibody (black peak), followed by an Alexa Fluor 647 secondary antibody, and 10,000 total events were assayed via flow cytometry. The gate shows the percentage of events in the murine MAb10 group that were brighter than the isotype group. (B) IFN-γ–activated RAW 246.7 cells were infected with murine A. baumannii strain 1127417 and given either isotype control treatment or 10 μg murine MAb10 for a 1-hour incubation. Cells were fixed and stained with Hema stain, and phagocytosed bacteria were counted in replicates of 5 photos per well and 3 wells per treatment. ****P < 0.0001, Mann-Whitney U test. (C) A 100× light microscopy photo with oil immersion showing RAW 246.7 cells having phagocytosed A. baumannii 1127417 with either isotype control treatment (left) or 10 μg murine MAb10 treatment (right). (D) C3H mice (n = 8) were infected with 4 × 107 CFU/mouse A. baumannii strain 1127417, then given either isotype control treatment or 1, 5, 50, or 150 μg murine MAb10 treatment. **P < 0.01, log-rank test. (E) Sprague-Dawley rats (n = 4) in which a subcutaneous fluid collection was created were infected with 1 × 109 CFU/mL A. baumannii strain 1127417, followed by intraperitoneal delivery of 0, 5, or 10 mg/kg MAb10. Fluid aliquots were collected from the abscess at 0, 24, 48, and 72 hours after infection and assayed for CFU/mL. *P < 0.05, 1-way ANOVA. (F) A. baumannii strain 1127417 was incubated with humanized MAb10 (blue peak) or isotype control antibody (black peak), followed by an Alexa Fluor 647 secondary antibody, and 10,000 total events were assayed via flow cytometry. Gate shows the percentage of events in the humanized MAb10 group that were brighter than the isotype group. (G) C3H mice were infected with 4 × 107 CFU/mouse A. baumannii strain 1127417 and given either isotype control treatment or 5 μg murine humanized MAb10 treatment (n = 8 and n = 7, respectively). *P = 0.0112, log-rank test. D and F represent the summed data of 2 separate in vivo experiments each.

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