Exploring Lectin Binding and Complement Activation in the Context of COVID-19 Infection: A Review of Immune Mechanisms

Background: The COVID-19 pandemic has aroused interest in understanding the immunological mechanisms involved in the response to SARS-CoV-2. The lectin pathway stands out in this scenario, since understanding the activation of this pathway during COVID-19 infection can provide valuable information about correlated immunological mechanisms, especially in the uncontrolled inflammatory response of severe cases.

Aim: Thus, the objective was to synthesize the available information on the role of the lectin pathway in the activation of the complement system and its relevance in the immune response and pathogenesis of COVID-19 infection.

Methods: This is a systematic review carried out according to the PRISMA guidelines using the PICOS strategy. The quality of the studies and risk of bias were evaluated using the Checklist Hawker. After the analysis, 11 pertinent studies with the objectives of this study were included.

Results: Patients with COVID-19 had high levels of mannose-binding lectin recognition protein (MBL), especially those with thromboembolic complications. MBL reduction due to certain genotypes (BB or AB) was associated with a more severe form of the disease. The interaction between VL recognition proteins and SARS-CoV-2 virus proteins suggests the activation of the complement system through this pathway. The interaction of SARS-CoV-2 protein N with the VL activator potentiates complement activation. There is a correlation between the genetic polymorphisms in the MBL2 gene and the expression of MBL in the tissues during infection.

Conclusion: Although some studies have not found consistent correlations between complement markers and disease severity, it is consensus that complement system activation is present in patients with COVID-19, and high levels of activation products are associated with more severe forms of the disease, suggesting that inadequate regulation of the complement system may contribute to the uncontrolled inflammatory response and serious complications of COVID-19. Future investigations should explore the specific mechanisms related to the activation of the complement system through the lectin pathway in SARS-CoV-2 infection, thus providing valuable insights for the development of more effective therapeutic strategies against COVID-19.