Kawasaki disease (KD) is a self-limited systemic vasculitis, most often occurring in children 1–5 years old. It has a 2% recurrence rate and is associated with coronary aneurysms (CA), which can develop within two weeks of onset. A 25% increased risk is noted in patients who are recalcitrant to treatment. We describe a patient with recurrence of KD three times, approximately four years apart. A 10-year-old female with two previous episodes of KD, at 11 months and five years of age), in which she met five out of five criteria for KD and had no coronary involvement, presented with 15 days of fever, conjunctivitis and mucocutaneous changes. Infectious work-up was negative, and she was diagnosed with incomplete KD meeting three out of five criteria. An echocardiogram (ECHO) on day 12 revealed dilation of the right coronary artery (RCA) and left coronary artery (LCA). Treatment with intravenous immunoglobulin (IVIG) and high-dose aspirin was started at an outside hospital. After transfer, serial ECHOs showed evolving coronary aneurysms, left anterior descending (LAD) z-score + 8.2 and RCA z-score + 4.0. She received 10 mg/kg infliximab (day 18) and began clopidogrel. A cardiac MRI (day 20) demonstrated progression of the LAD aneurysm, with a z-score + 13, and warfarin was started. To our knowledge, this is the first report of recurrent KD occurring three times at ~5 year intervals.

The ability of Mycobacterium tuberculosis to respond and adapt to various stresses such as oxygen/nitrogen radicals and low pH inside macrophages is critical for the persistence of this human pathogen inside its host. We have previously shown that an AraC/XylS-type transcriptional regulator, VirS, which is induced in low pH, is involved in remodeling the architecture of the bacterial cell envelope. However, how VirS influences gene expression to coordinate these pH responses remains unclear. Here, using a genetic biosensor of cytoplasmic pH, we demonstrate that VirS is required for the intracellular pH maintenance in response to acidic stress and inside acidified macrophages. Furthermore, we observed that VirS plays an important role in blocking phagosomal-lysosomal fusions. Transcriptomics experiments revealed that VirS affects the expression of genes encoding metabolic enzymes, cell-wall envelope proteins, efflux pumps, ion transporters, detoxification enzymes, and transcriptional regulators expressed under low-pH stress. Employing electrophoretic mobility-shift assays, DNA footprinting, and in silico analysis, we identified a DNA sequence to which VirS binds and key residues in VirS required for its interaction with DNA. A significant role of VirS in M. tuberculosis survival in adverse conditions suggested it as a potential anti-mycobacterial drug target. To that end, we identified VirS inhibitors in a virtual screen; the top hit compounds inhibited its DNA-binding activity and also M. tuberculosis growth in vitro and inside macrophages. Our findings establish that VirS mediates M. tuberculosis responses to acidic stress and identify VirS-inhibiting compounds that may form the basis for developing more effective anti-mycobacterial agents.

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