Immunological interactions in helminths-SARS CoV-2 coinfection: Could old enemy be a friend today?

Helminths are metazoan parasites affecting about one third of the worldwide population. Chronic helminth infections (CHIs) confer immunological tolerance to harmless and self-antigens mediated by regulatory T cells (Treg) that are up-regulated. In coronavirus disease 2019 (COVID-19), abnormal adaptive immune response and unrestrained innate immune response could result in local and systemic immune-mediated tissue damage. COVID-19 and CHIs establish complicated immune interactions due to SARS-CoV-2-induced immunological stimulation and CHIs-induced immunological tolerance. However, COVID-19 severity in patients with CHIs is mild, as immuno-suppressive anti-inflammatory cytokines counterbalance the risk of cytokine storm. Here, an overview of the interplay between helminths and COVID-19 severity is given. CHIs through helminth-derived molecules may suppress SARS-CoV-2 entry and associated hyperinflammation through attenuation of the TLR4/NF-kB signalling pathway. In addition, CHIs may reduce the COVID-19 severity by reducing the SARS-CoV-2 entry points at ACE2/DPP4/CD147 axis in the initial phase and immunomodulation in the late phase of the disease by suppressing TLR4/NF-kB signalling pathway.