Host-directed therapeutics, also called host targeted therapeutics, act via a host-mediated response to pathogens rather than acting directly on the pathogen, like traditional antibiotics. They can change the local environment in which the pathogen exists to make it less favorable for the pathogen to live and/or grow. With these therapies, pathogen killing, e.g.bactericidal effects, will likely only occur when it is co-delivered with a traditional agent that acts directly on the pathogen, such as an antibiotic, antifungal, or antiparasitic agent.[1][2][3] Several antiviral agents are host-directed therapeutics, and simply slow the virus progression rather than kill the virus. Host-directed therapeutics may limit pathogen proliferation, e.g., have bacteriostatic effects. Certain agents also have the ability to reduce bacterial load by enhancing host cell responses even in the absence of traditional antimicrobial agents.[4][5][6]

Types

Immunomodulatory

Intracellular pathogens often reside in immune cells like macrophages. These pathogens can be obligate or facultative intracellular pathogens. Changing the innate immune response of these host-cells can alter the pathogen's ability to live inside the cell. Many of these immunomodulatory host-directed therapies are adjuvants or pathogen-associated molecular patterns. They can include Toll-like receptors (TLRs), NOD-like receptors (NLRs), C-type lectin receptors (CLRs), mannose receptor (MR), dendritic cell-specific intracellular adhesion molecule 3 (ICAM3)-grabbing nonintegrin (DC-SIGN), complement receptors, Fc receptors, and DNA sensors (e.g., STING). Epithelial cells also host pathogens, like Salmonella enterica. These immunomodulatory agents can also alter the epithelial cell environments, since they also have a role in innate signalling.

Enhanced host cell function

Autophagy modulators are one type of method to enhance host cell functions. Pathogens like Mycobacterium tuberculosis (MTB), will be degraded in the autophagosome during an effective host response that will clear the bacteria. Because bacteria and other pathogens like MTB can take over cellular responses like autophagy, they can increase their survival in the body. By reactivating effective autophagy processes the pathogen could be cleared. Examples of this has been shown with MTB,[1] and Listeria monocytogenes.[1] OSU-03012 is thought to modulate autophagy in its effect on Salmonella enterica,[7][8] and Francisella tularensis.[9][10]

Pathology modification

Modifying lung and macrophage pathology has been shown to have a role in the host-directed therapies for MTB.[1]

References

  1. 1 2 3 4 Hawn TR, Matheson AI, Maley SN, Vandal O (December 2013). "Host-directed therapeutics for tuberculosis: can we harness the host?". Microbiology and Molecular Biology Reviews. 77 (4): 608–27. doi:10.1128/MMBR.00032-13. PMC 3973381. PMID 24296574.
  2. ↑ Mahon RN, Hafner R (2017). "Applying Precision Medicine and Immunotherapy Advances from Oncology to Host-Directed Therapies for Infectious Diseases". Frontiers in Immunology. 8: 688. doi:10.3389/fimmu.2017.00688. PMC 5489679. PMID 28706516.
  3. ↑ Armstrong-James D, Brown GD, Netea MG, Zelante T, Gresnigt MS, van de Veerdonk FL, Levitz SM (December 2017). "Immunotherapeutic approaches to treatment of fungal diseases". The Lancet. Infectious Diseases. 17 (12): e393–e402. doi:10.1016/S1473-3099(17)30442-5. hdl:10044/1/57316. PMID 28774700.
  4. ↑ Yang Z, Bedugnis A, Levinson S, Dinubile M, Stossel T, Lu Q, Kobzik L (September 2019). "Delayed Administration of Recombinant Plasma Gelsolin Improves Survival in a Murine Model of Penicillin-Susceptible and Penicillin-Resistant Pneumococcal Pneumonia". The Journal of Infectious Diseases. 220 (9): 1498–1502. doi:10.1093/infdis/jiz353. PMC 6761947. PMID 31287867.
  5. ↑ Ordija CM, Chiou TT, Yang Z, Deloid GM, de Oliveira Valdo M, Wang Z, et al. (June 2017). "Free actin impairs macrophage bacterial defenses via scavenger receptor MARCO interaction with reversal by plasma gelsolin". American Journal of Physiology. Lung Cellular and Molecular Physiology. 312 (6): L1018–L1028. doi:10.1152/ajplung.00067.2017. PMC 5495953. PMID 28385809.
  6. ↑ Yang Z, Chiou TT, Stossel TP, Kobzik L (July 2015). "Plasma gelsolin improves lung host defense against pneumonia by enhancing macrophage NOS3 function". American Journal of Physiology. Lung Cellular and Molecular Physiology. 309 (1): L11-6. doi:10.1152/ajplung.00094.2015. PMC 4491512. PMID 25957291.
  7. ↑ Chiu HC, Kulp SK, Soni S, Wang D, Gunn JS, Schlesinger LS, Chen CS (December 2009). "Eradication of intracellular Salmonella enterica serovar Typhimurium with a small-molecule, host cell-directed agent". Antimicrobial Agents and Chemotherapy. 53 (12): 5236–44. doi:10.1128/aac.00555-09. PMC 2786354. PMID 19805568.
  8. ↑ Hoang KV, Borteh HM, Rajaram MV, Peine KJ, Curry H, Collier MA, et al. (December 2014). "Acetalated dextran encapsulated AR-12 as a host-directed therapy to control Salmonella infection". International Journal of Pharmaceutics. 477 (1–2): 334–43. doi:10.1016/j.ijpharm.2014.10.022. PMC 4267924. PMID 25447826.
  9. ↑ Chiu HC, Soni S, Kulp SK, Curry H, Wang D, Gunn JS, et al. (December 2009). "Eradication of intracellular Francisella tularensis in THP-1 human macrophages with a novel autophagy inducing agent". Journal of Biomedical Science. 16 (1): 110. doi:10.1186/1423-0127-16-110. PMC 2801672. PMID 20003180.
  10. ↑ Hoang KV, Curry H, Collier MA, Borteh H, Bachelder EM, Schlesinger LS, et al. (April 2016). "Needle-Free Delivery of Acetalated Dextran-Encapsulated AR-12 Protects Mice from Francisella tularensis Lethal Challenge". Antimicrobial Agents and Chemotherapy. 60 (4): 2052–62. doi:10.1128/AAC.02228-15. PMC 4808193. PMID 26787696.
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