Abstract
The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has led to coronavirus disease (COVID-19), a global health pandemic causing millions of deaths worldwide. However, the 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. However, TLRs may also act as a double-edged sword, and dysregulated TLR responses may enhance immune-mediated pathology, instead of providing protection. Therefore, a proper understanding of the interaction between TLRs and SARS-CoV-2 is of great importance for devising therapeutic and preventive strategies. The use of TLR agonists as vaccine adjuvants for human disease is a promising approach that could be applied in the investigation of COVID-19 vaccines. In this review, we discuss the recent progress in our understanding of host innate immune responses in SARS-CoV-2 infection, with particular focus on TLR response. In addition, we discuss the use of TLR agonists as vaccine adjuvants in enhancing the efficacy of COVID-19 vaccine.
Highlights
Coronaviruses (CoVs) are agents of emerging and re-emerging infection that pose a significant challenge to human health [1]
TLR2, which results in the hyperexpression of pro-inflammatory cytokines (Figure 1) that may contribute to disease severity [30], suggesting that TLR2-mediated inflammation plays a pathogenic role in SARS-CoV-2 infection
Results not published yet Results not published yet Current evidence suggests that the hyperinflammation that results from a dysregulated host innate immune response has a negative effect on the COVID-19 outcome
Summary
Coronaviruses (CoVs) are agents of emerging and re-emerging infection that pose a significant challenge to human health [1]. There is a need for further investigation of the host immune response to SARS-CoV-2 infection, including newly emerging variants, as well as the efficacy of vaccines against them. The key innate immune sensing receptors are germ line-encoded pattern-recognition receptors (PRRs), which mediate the initial sensing of infection by recognition of PAMPs, upon microbial invasion of the host [17,18]. TLR activation may act as a double-edged sword, and its dysregulated response may lead to immune-mediated pathology, instead of protection [27,28,29], which has been observed in cases of SARS-CoV-2 infection [30]. The potential of TLR agonists as adjuvants for COVID-19 vaccines has been discussed
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
