id8b00135_si_001.pdf (1.05 MB)
High Throughput Screen Identifies Interferon γ‑Dependent Inhibitors of Toxoplasma gondii Growth
journal contribution
posted on 2018-07-30, 00:00 authored by Joshua B. Radke, Kimberly L. Carey, Subrata Shaw, Shailesh R. Metkar, Carol Mulrooney, Jennifer P. Gale, Joshua A. Bittker, Robert Hilgraf, Eamon Comer, Stuart L. Schreiber, Herbert W. Virgin, Jose R. Perez, L. David SibleyToxoplasma gondii is an obligate intracellular
parasite capable of causing severe disease due to congenital infection
and in patients with compromised immune systems. Control of infection
is dependent on a robust Th1 type immune response including production
of interferon gamma (IFN-γ), which is essential for control.
IFN-γ activates a variety of antimicrobial mechanisms in host
cells, which are then able to control intracellular parasites such
as T. gondii. Despite the effectiveness of these
pathways in controlling acute infection, the immune system is unable
to eradicate chronic infections that can persist for life. Similarly,
while antibiotic treatment can control acute infection, it is unable
to eliminate chronic infection. To identify compounds that would act
synergistically with IFN-γ, we performed a high-throughput screen
of diverse small molecule libraries to identify inhibitors of T. gondii. We identified a number of compounds that
inhibited parasite growth in vitro at low μM
concentrations and that demonstrated enhanced potency in the presence
of a low level of IFN-γ. A subset of these compounds act by
enhancing the recruitment of light chain 3 (LC3) to the parasite-containing
vacuole, suggesting they work by an autophagy-related process, while
others were independent of this pathway. The pattern of IFN-γ
dependence was shared among the majority of analogs from 6 priority
scaffolds, and analysis of structure activity relationships for one
such class revealed specific stereochemistry associated with this
feature. Identification of these IFN-γ-dependent leads may lead
to development of improved therapeutics due to their synergistic interactions
with immune responses.