The Confluence of Sex Hormones and Aging on Immunity

The immune systems of post-pubescent males and females differ significantly with profound consequences to health and disease. In many cases, sex-specific differences in the immune responses of young adults are also apparent in aged men and women. Moreover, as in young adults, aged women develop several late-adult onset autoimmune conditions more frequently than do men, while aged men continue to develop many cancers to a greater extent than aged women. However, sex differences in the immune systems of aged individuals have not been extensively investigated and data addressing the effectiveness of vaccinations and immunotherapies in aged men and women are scarce. In this review, we evaluate age- and sex hormone-related changes to innate and adaptive immunity, with consideration about how this impacts age- and sex-associated changes in the incidence and pathogenesis of autoimmunity and cancer as well as the efficacy of vaccination and cancer immunotherapy. We conclude that future preclinical and clinical studies should consider age and sex to better understand the ways in which these characteristics intersect with immune function and the resulting consequences for autoimmunity, cancer, and therapeutic interventions

Forward Genetic Screening Identifies a Small Molecule That Blocks <i>Toxoplasma gondii</i> Growth by Inhibiting Both Host- and Parasite-Encoded Kinases

<div><p>The simultaneous targeting of host and pathogen processes represents an untapped approach for the treatment of intracellular infections. Hypoxia-inducible factor-1 (HIF-1) is a host cell transcription factor that is activated by and required for the growth of the intracellular protozoan parasite <i>Toxoplasma gondii</i> at physiological oxygen levels. Parasite activation of HIF-1 is blocked by inhibiting the family of closely related Activin-Like Kinase (ALK) host cell receptors ALK4, ALK5, and ALK7, which was determined in part by use of an ALK4,5,7 inhibitor named SB505124. Besides inhibiting HIF-1 activation, SB505124 also potently blocks parasite replication under normoxic conditions. To determine whether SB505124 inhibition of parasite growth was exclusively due to inhibition of ALK4,5,7 or because the drug inhibited a second kinase, SB505124-resistant parasites were isolated by chemical mutagenesis. Whole-genome sequencing of these mutants revealed mutations in the <i>Toxoplasma</i> MAP kinase, TgMAPK1. Allelic replacement of mutant TgMAPK1 alleles into wild-type parasites was sufficient to confer SB505124 resistance. SB505124 independently impacts TgMAPK1 and ALK4,5,7 signaling since drug resistant parasites could not activate HIF-1 in the presence of SB505124 or grow in HIF-1 deficient cells. In addition, TgMAPK1 kinase activity is inhibited by SB505124. Finally, mice treated with SB505124 had significantly lower tissue burdens following <i>Toxoplasma</i> infection. These data therefore identify SB505124 as a novel small molecule inhibitor that acts by inhibiting two distinct targets, host HIF-1 and TgMAPK1.</p></div

SB505124 directly targets TgMAPK1.

<p>A. Strategy for endogenously tagging TgMAPK1 with 3×HA tag. B. Immunoprecipitated TgMAPK1-HA was separated by SDS-PAGE for western blotting antibody and <i>in vitro</i> kinase assays. C. Equivalent volumes of RH WT or RH:TgMAPK1-HA lysate were added anti-HA sepharose beads, then washed and then processed for <i>in vitro</i> autokinase assays. The lysates were then separated by SDS-PAGE and visualized by autoradiography. Shown is a representative assay. D. Equivalent amounts of TgMAPK1-HA was immunoprecipitated from RH:TgMAPK1HA lysates using anti-HA sepharose beads and processed for <i>in vitro</i> kinase assays in the presence of increasing concentrations of SB505124. A representative assay with relative amounts of TgMAPK1 activity in each reaction is shown. E. Dose response curve showing averaged data and standard deviations from 3 experiments. F. Lysates (80 µg) were prepared from RHΔKu80ΔHPT (WT), RHΔKu80ΔHPT:TgMAPK1^WT-HA, and RHΔKu80ΔHPT:TgMAPK1<i>^ts</i>^-HA parasites grown at 34°C. Epitope-tagged TgMAPK1 was then detected using rat anti-HA antisera in the whole cell lysate and the flow through and immunoprecipitates following immunoprecipitation using rabbit anti-HA antibody conjugated beads. G. Immunoprecipitates of the indicated HA-tagged TgMAPK1 alleles were washed in kinase assay buffer and then incubated with γ³²P-ATP for 60′ at 34°C. Shown are triplicate samples prepared from the same lysates immunoprecipitated in F. The experiment was repeated 3 independent times and representative gels are shown.</p

Toxoplasma secreting Cre recombinase for analysis of host-parasite interactions

We describe the use of site specific recombination to study the host-parasite interactions of Toxoplasma gondii. We present a Toxoplasma strain that efficiently injects a Cre fusion protein into host cells. In a Cre-reporter cell line, a single parasite invasion induced Cre-mediated recombination in 95% of infected host cells. By infecting Cre reporter mice with these parasites, host cell infection could also be monitored in vivo