Most people heavily exposed to Mycobacterium tuberculosis become infected and develop latent Mtb infection. However, in a TB contact study in urban Uganda, approximately 9% of close adult contacts did not develop LTBI during two years of follow-up. In S. Africa, some miners do not develop LTBI despite more than 20 years of employment under the highest Mtb infection pressure in the world. These persons without evidence of LTBI despite intense Mtb exposure appear to be LTBI resisters (RSTRs). Monocytes after Mtb infection revealed transcriptional signatures that distinguished RSTRs from HHC with LTBI. These data support the hypothesis that host factors can distinguish RSTRs and that they have protective innate immune responses expressed in macrophages. HIV dysregulates immune responses to Mtb, thus HIV infected persons depend more on innate immunity to control Mtb than HIV- persons. Thus we hypothesize that innate mechanisms of resistance to LTBI are more readily identified in HIV+ RSTRs.
The aims are: 1. Identify, characterize and recruit cohorts of HIV+ individuals who resist latent Mtb infection among TB household contacts in Uganda and among miners in South Africa. Approach: Follow-up previously identified HIV+ RSTRs and recruit new RSTRs from among TB HHC in Uganda, and i S. Africa recruit a new cohort of HIV+ RSTRs. HIV+ LTBIs, and HIV- RSTRs and HIV- LTBIs will serve as controls. Hypothesis: HIV+ and HIV- RSTRs can be identified in populations with different Mtb exposures but host resistance mechanisms will be shared and thus enable assembly of robust cohorts for innate immune function studies.
Aim 2. Determine macrophage transcriptional signatures associated with resistance to latent Mtb infection in HIV+ persons. Approach: Compare early transcriptional responses to Mtb in macrophages between HIV+ RSTRs and LTBIs. Compare these to the responses of macrophages from HIV- RSTRs and HIV- LTBIs, and extend studies to alveolar macrophages. Hypothesis: Biological pathways in macrophages regulate resistance to Mtb infection and these pathways are more readily identified in HIV+ persons.
Aim 3. Determine cellular mechanisms of resistance to latent Mtb infection. Approach: a. Cellular knockouts through CRISPR/Cas9 technology and small molecule inhibitors to investigate how key genes and pathways identified in Aim 2 allow macrophages to resist or clear Mtb; b. Whole blood assays of Mtb killing to distinguish HIV+ RSTRs from LTBIs; c. Flow cytometry to examine whether innate unconventional T-cells are enriched in HIV+ RSTRs. Hypothesis: a. HIV+ RSTR use macrophage-specific pathways to control Mtb; b. A WBA can detect differences in control of Mtb growth between RSTRs and LTBIs; c. HIV+ RSTRs use unconventional innate T cells to control Mtb. For this project, we have assembled two experienced TB clinical research sites (Mulago Hospital in Uganda & the Aurum Institute in S. Africa) with epidemiologists, systems biologists, geneticists, immunologists, microbiologists, and clinicians at Makerere University in Uganda, Aurum Institute in S. Africa, University of Washington and Case Western Reserve University.
Identification of HIV+ and HIV- individuals persons who resist latent Mycobacterium tuberculosis (Mtb) infection and understanding the mechanism of this resistance will provide insight into our understanding of how humans can protect themselves against this infectious pathogen that causes tuberculosis (TB). This insight will also point to novel approaches to TB vaccine and host-directed therapy, and identify biomarkers of resistance to and/or clearance of Mtb infection.
|Simmons, Jason D; Stein, Catherine M; Seshadri, Chetan et al. (2018) Immunological mechanisms of human resistance to persistent Mycobacterium tuberculosis infection. Nat Rev Immunol 18:575-589|
|Stein, Catherine M; Zalwango, Sarah; Malone, LaShaunda L et al. (2018) Resistance and Susceptibility to Mycobacterium tuberculosis Infection and Disease in Tuberculosis Households in Kampala, Uganda. Am J Epidemiol 187:1477-1489|
|Stein, Catherine M; Sausville, Lindsay; Wejse, Christian et al. (2017) Genomics of human pulmonary tuberculosis: from genes to pathways. Curr Genet Med Rep 5:149-166|
|Seshadri, Chetan; Sedaghat, Nafiseh; Campo, Monica et al. (2017) Transcriptional networks are associated with resistance to Mycobacterium tuberculosis infection. PLoS One 12:e0175844|