"Abstract
... [Th]e immunopathogenesis of COVID-19, particularly the interaction between SARS-CoV-2 and host innate immunity, remains unclear. The innate immune system acts as the first line of host defense, which is critical for the initial detection of invading pathogens and the activation and shaping of adaptive immunity. Toll-like receptors (TLRs) are key sensors of innate immunity that recognize pathogen-associated molecular patterns and activate downstream signaling for pro-inflammatory cytokine and chemokine production...
1. Introduction
... TLR response ultimately may lead to the induction of interferons (IFNs), cytokines, and chemokines by several distinct signaling pathways, thereby limiting infection and promoting adaptive immune responses. However, TLR activation may act as a double-edged sword, and its dysregulated response may lead to immune-mediated pathology, instead of protection, which has also been observed in cases of SARS-CoV-2 infection. Therefore, a clear understanding of the role of TLRs in SARS-CoV-2 infection is critical for learning about the immunopathogenesis involved and for the development of therapeutic and preventive strategies against the disease. The focus of this article is to provide an overview of our recent understanding of TLR response to SARS-CoV-2 infection. In addition, the potential of TLR agonists as adjuvants for COVID-19 vaccines has also been discussed herein..."
Note: A TLC agonist is a substance that actives toll-like receptors. (source)
3. TLR Agonists as COVID-19 Vaccine Adjuvants
... To combat the COVID-19 pandemic, there is a critical need for the development of efficient and safe vaccines. Vaccine adjuvants are important for enhancing the immune response against corresponding pathogens, and selecting an appropriate adjuvant is important for vaccine efficacy...
... [S]o far, no phase II and III clinical trial results of TLR agonists for COVID-19 vaccines have been published."
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