Abstract:
Antimicrobial resistance alongside other challenges in tuberculosis (TB) therapeutics have stirred renewed interest
in host-directed interventions, including the role of antibodies as adjunct therapeutic agents. This study
assessed the binding efficacy of two novel IgG1 opsonic monoclonal antibodies (MABs; GG9 & JG7) at 5, 10, and
25 μg/mL to live cultures of Mycobacterium tuberculosis, M. avium, M. bovis, M. fortuitum, M. intracellulare, and
M. smegmatis American Type Culture Collection laboratory reference strains, as well as clinical susceptible, multidrug
resistant, and extensively drug resistant M. tuberculosis strains using indirect enzyme-linked immunosorbent
assays. These three MAB concentrations were selected from a range of concentrations used in previous optimization
(binding and functional) assays. Both MABs bound to all mycobacterial species and sub-types tested, albeit
to varying degrees. Statistically significant differences in MAB binding activity were observed when comparing
the highest and lowest MAB concentrations (p < 0.05) for both MABs GG9 and JG7, irrespective of the
M. tuberculosis resistance profile. Binding affinity increased with an increase in MAB concentration, and optimal
binding was observed at 25 μg/mL. JG7 showed better binding activity than GG9. Both MABs also bound to five
MOTT species, albeit at varied levels. This non-selective binding to different mycobacterial species suggests a
potential role for GG9 and JG7 as adjunctive agents in anti-TB chemotherapy with the aim to enhance bacterial
killing.
