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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 4

MAb binding of A. baumannii strains assessed by flow cytometry predicts in vivo treatment outcomes.

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MAb binding of A. baumannii strains assessed by flow cytometry predicts ...
(A) Y axis shows the percentage survival at 7 days after infection of mice when given MAb treatment, indicated by color. X axis shows the percentage binding (percentage of events in flow cytometry that were brighter than the isotype control). Each data point represents a group of n = 3 mice, with a total of 19 strain/MAb combinations being tested (listed in Table 2). P < 0.001, Rho = 0.862, 2-sided Spearman rank correlation test. (B) Y axis shows the fold-reduction of blood CFU, 2 hours after A. baumannii infection and treatment with 15 μg MAb. X axis shows percentage binding each strain with the MAb tested. Strain identities are indicated by color; immunosuppressive regimen used for each strain is shown by shape of the points. Bars indicate medians; each data point represents a single mouse. A total of 12 strain/MAb combinations are shown, using 11 different strains, n = 3–5 mice per strain/MAb combo. P < 0.001, Rho = –0.669, 2-sided Spearman rank correlation test. (C) X axis shows the percentage binding by flow cytometry. Y axis combines the data from 12 CFU experiments and 19 survival experiments to indicate strain susceptibility to MAb therapy. CVF, cobra venom factor; Cyclo, cyclophosphamide.

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