Myeloid C-Type Lectin Receptors in Tuberculosis and HIV Immunity: Insights Into Co-infection?

Myeloid C-type lectin receptors in innate immune recognition

C-type lectin receptors (CLRs) expressed by myeloid cells constitute a versatile family of receptors that play a key role in innate immune recognition. Myeloid CLRs exhibit a remarkable ability to recognize an extensive array of ligands, from carbohydrates and beyond, and encompass pattern-associated molecular patterns (PAMPs), damage-associated molecular patterns (DAMPs), and markers of altered self. These receptors, classified into distinct subgroups, play pivotal roles in immune recognition and modulation of immune responses. Their intricate signaling pathways orchestrate a spectrum of cellular responses, influencing processes such as phagocytosis, cytokine production, and antigen presentation. Beyond their contributions to host defense in viral, bacterial, fungal, and parasitic infections, myeloid CLRs have been implicated in non-infectious diseases such as cancer, allergies, and autoimmunity. A nuanced understanding of myeloid CLR interactions with endogenous and microbial triggers is starting to uncover the context-dependent nature of their roles in innate immunity, with implications for therapeutic intervention.

Polymorphisms in Immune Genes and Their Association with Tuberculosis Susceptibility: An Analysis of the African Population

Tuberculosis remains a global health concern, with substantial mortality rates worldwide. Genetic factors play a significant role in influencing susceptibility to tuberculosis. This review examines the current progress in studying polymorphisms within immune genes associated with tuberculosis susceptibility, focusing on African populations. The roles of various proteins, including Toll-like receptors, Dendritic Cell-Specific Intercellular Adhesion Molecule-3 Grabbing Non-Integrin, vitamin D nuclear receptor, soluble C-type lectins such as surfactant proteins A and D, C-type Lectin Domain Family 4 Member E, and mannose-binding lectin, phagocyte cytokines such as Interleukin-1, Interleukin-6, Interleukin-10, Interleukin-12, and Interleukin-18, and chemokines such as Interleukin-8, monocyte chemoattractant protein 1, Regulated upon activation, normal T-cell expressed and secreted are explored in the context of tuberculosis susceptibility. We also address the potential impact of genetic variants on protein functions, as well as how these findings align with the genetic polymorphisms not associated with tuberculosis. Functional studies in model systems provide insights into the intricate host-pathogen interactions and susceptibility mechanisms. Despite progress, gaps in knowledge remain, highlighting the need for further investigations. This review emphasizes the association of Single Nucleotide Polymorphisms with diverse aspects of tuberculosis pathogenesis, including disease detection and Mycobacterium tuberculosis infection.

The Many Hosts of Mycobacteria 9 (MHM9): A conference report

The Many Hosts of Mycobacteria (MHM) meeting series brings together basic scientists, clinicians and veterinarians to promote robust discussion and dissemination of recent advances in our knowledge of numerous mycobacterial diseases, including human and bovine tuberculosis (TB), nontuberculous mycobacteria (NTM) infection, Hansen's disease (leprosy), Buruli ulcer and Johne's disease. The 9th MHM conference (MHM9) was held in July 2022 at The Ohio State University (OSU) and centered around the theme of "Confounders of Mycobacterial Disease." Confounders can and often do drive the transmission of mycobacterial diseases, as well as impact surveillance and treatment outcomes. Various confounders were presented and discussed at MHM9 including those that originate from the host (comorbidities and coinfections) as well as those arising from the environment (e.g., zoonotic exposures), economic inequality (e.g. healthcare disparities), stigma (a confounder of leprosy and TB for millennia), and historical neglect (a confounder in Native American Nations). This conference report summarizes select talks given at MHM9 highlighting recent research advances, as well as talks regarding the historic and ongoing impact of TB and other infectious diseases on Native American Nations, including those in Southwestern Alaska where the regional TB incidence rate is among the highest in the Western hemisphere.

Macrophage Polarity and Disease Control

Macrophages are present in most human tissues and have very diverse functions. Activated macrophages are usually divided into two phenotypes, M1 macrophages and M2 macrophages, which are altered by various factors such as microorganisms, tissue microenvironment, and cytokine signals. Macrophage polarity is very important for infections, inflammatory diseases, and malignancies; its management can be key in the prevention and treatment of diseases. In this review, we assess the current state of knowledge on macrophage polarity and report on its prospects as a therapeutic target.

The Manifesto of Pharmacoenosis: Merging HIV Pharmacology into Pathocoenosis and Syndemics in Developing Countries

Pathocoenosis and syndemics theories have emerged in the last decades meeting the frequent need of better understanding interconnections and reciprocal influences that coexistent communicable and non-communicable diseases play in a specific population. Nevertheless, the attention to pharmacokinetic and pharmacodynamics interactions of co-administered drugs for co-present diseases is to date limitedly paid to alert against detrimental pharmacological combos. Low and middle-income countries are plagued by the highest burden of HIV, tuberculosis, malaria, and helminthiasis, and they are experiencing an alarming rise in non-communicable disorders. In these settings, co-infections and comorbidities are common, but no tailored prescribing nor clinical trials are used to assess and exploit existing opportunities for the simultaneous and potentially synergistic treatment of intertwined diseases. Pharmacoenosis is the set of interactions that take place within a host as well as within a population due to the compresence of two or more diseases and their respective treatments. This framework should pilot integrated health programmes and routine clinical practice to face drug–drug interaction issues, avoiding negative co-administrations but also exploiting potential favourable ones to make the best out of the worst situations; still, to date, guiding data on the latter possibility is limited. Therefore, in this narrative review, we have briefly described both detrimental and favourable physiopathological interactions between HIV and other common co-occurring pathologies (malaria, tuberculosis, helminths, and cardiovascular disorders), and we have presented examples of advantageous potential pharmacological interactions among the drugs prescribed for these diseases from a pharmacokinetics, pharmacodynamics, and pharmacogenetics standpoint.

Novel Role for Macrophage Galactose-Type Lectin-1 to Regulate Innate Immunity against Mycobacterium tuberculosis

Tuberculosis (TB) caused by infection with Mycobacterium tuberculosis is characterized by inflammatory pathology and poorly understood mechanisms of innate immunity. Pattern recognition receptors, expressed on the surface of macrophages, determine the balance of inflammatory and antimicrobial functions that influence disease outcome. Carbohydrate moieties displayed by mycobacteria can serve as pattern recognition receptor ligands for some members of the C-type lectin receptor (CLR) family, interactions that mediate a variety of incompletely understood immune outcomes. This work identifies a novel role for the CLR macrophage galactose-type lectin (MGL)-1 in a mouse model (C57BL/6 and MGL-1^-/-) of experimental TB. Murine macrophages upregulated MGL-1 following in vitro exposure to M. tuberculosis, whereas MGL⁺ cells accumulated at sites of mycobacteria-driven inflammation in the lung. Pulmonary macrophages from MGL-1-deficient mice displayed increased production of proinflammatory cytokines (IL-1β, IL-6, and IFN-γ) that were associated with greater lipid accumulation, following M. tuberculosis infection. Surprisingly, for a CLR, we also observed MGL-1-dependent antimycobacterial activity as evidenced by greater M. tuberculosis proliferation in bone marrow-derived macrophages, and the lung, of MGL-1-deficient mice. Differential transcriptome analysis further revealed that loss of MGL-1 perturbs the activation of various genes involved in the regulation of inflammation and lipid metabolism in the setting of M. tuberculosis infection. These results identify MGL-1 signaling as an important mechanism that regulates innate immunity against M. tuberculosis and indicates the potential for the MGL pathway as a novel therapeutic target for anti-TB immunity.

Generation of Liposomes to Study the Effect of Mycobacterium Tuberculosis Lipids on HIV-1 cis- and trans-Infections

Tuberculosis (TB) is the leading cause of death among HIV-1-infected individuals and Mycobacterium tuberculosis (Mtb) co-infection is an early precipitate to AIDS. We aimed to determine whether Mtb strains differentially modulate cellular susceptibility to HIV-1 infection (cis- and trans-infection), via surface receptor interaction by their cell envelope lipids. Total lipids from pathogenic (lineage 4 Mtb H37Rv, CDC1551 and lineage 2 Mtb HN878, EU127) and non-pathogenic (Mycobacterium bovis BCG and Mycobacterium smegmatis) Mycobacterium strains were integrated into liposomes mimicking the lipid distribution and antigen accessibility of the mycobacterial cell wall. The resulting liposomes were tested for modulating in vitro HIV-1 cis- and trans-infection of TZM-bl cells using single-cycle infectious virus particles. Mtb glycolipids did not affect HIV-1 direct infection however, trans-infection of both R5 and X4 tropic HIV-1 strains were impaired in the presence of glycolipids from M. bovis, Mtb H37Rv and Mtb EU127 strains when using Raji-DC-SIGN cells or immature and mature dendritic cells (DCs) to capture virus. SL1, PDIM and TDM lipids were identified to be involved in DC-SIGN recognition and impairment of HIV-1 trans-infection. These findings indicate that variant strains of Mtb have differential effect on HIV-1 trans-infection with the potential to influence HIV-1 disease course in co-infected individuals.