Effect of SARS-CoV-2 Spike protein glycosylation on complement activation

The pandemic SARS-CoV-2 coronavirus is the cause of the disease called COVID-19 that it characterizes Severe pneumonia, among others. Until mid-December 2020 confirmed in the world over 69 million cases and over 1.5 million patients died. Sometimes the infection continues asymptomatic or mild, but many patients develop acute respiratory failure and often death. Difficulties in inhibiting the spread of the virus result from a lack of specific ones symptoms (these may resemble symptoms of other infections), lack of effective treatment, long the time from infection to the onset of symptoms, and transmission of the virus by infected individuals asymptomatic. An effective response of the immune system, both natural (innate) and acquired (production of specific antibodies) is crucial for the course of the infection and its sequelae. When the answer congenital will not eliminate the pathogen or adequately stimulate the acquired immune system, it may occur develop a sustained, severe, life-threatening inflammatory reaction. It manifests itself, inter alia, in the so-called cytokine storm leading to respiratory failure and organ damage. Complement system it is an important element of the body's first line of defense against pathogens. Some of its factors can recognize SARS-CoV-2 antigens, including the so-called Spike glycoprotein (Spike glycoprotein, S-gp) - virus surface protein containing sugar chains - glycans. This protein is similar to corresponding structure of a previously known other coronavirus - SARS-CoV-1 and contains mannose residues. Mannose-rich glycans may play an important role in the interaction of the virus with collectins such as MBL, CL-K1, CL-L1 or SP-D (explained below). Moreover, it is believed that S-gp may be a recognition structure by human phycolines. Collectins and ficolins, which are factors of innate immunity, act similarly to antibodies, but unlike them, their specificity (that is, the ability to recognize "foreign") is wide. Such factors specific to sugars are called lectins. These lectins, with the exception of SPD, have the ability to activate the complement (the so-called lectin pathway) thanks to the interaction with MASP, occurring with them in complexes. Some of them (MBL, CL-K1, SP-D) are specifically recognized mannose. Based on SARS-CoV-1 data and recent literature reports on SARS-CoV-2, we believe that the interaction of the complement system with the surface antigens of the second z These viruses could be critical to the course and sequelae of COVID-19: maybe contribute to the elimination of the virus but, on the other hand, to occur with over-activation unwanted, severe symptoms such as shock associated with organ damage. Possibility The adverse effects of complement activation suggest preliminary, promising treatment trials for COVID-19 with its inhibitors (inhibitors), including a selective (selective) pathway inhibitor lectin - narsoplimab. Moreover, these lectins are likely to modify specific binding antibodies to the Spike glycoprotein and, depending on the stage of infection, increase or inhibit their effect antivirus. To understand the role of SARS-CoV-2 glycosylation in the interaction with collectins and phicolins, we propose to test the binding of these factors - recombinant and present in serum (present in in complexes with MASP, and thus capable of activating complement) to the glycoprotein Spike SARS-CoV-2 and obtained by modifying its variants with a changed glycan structure. We are planning to manufacture (in a SARS-CoV-2 virus free system) of recombinant S-glycoprotein and 3 of its variants with an altered sugar pattern and evaluation of the importance of glycans (called N-glycans) in recognition of the virus by selected lectins. Spike SARS-CoV-1 glycoprotein obtained in a similar way will serve as a positive control. We also plan to investigate some of the biological consequences expected interactions (complement activation, influence on the interaction of S-gp with specific antibodies). The lectins tested will be: Mannose Binding Lectin (MBL), Liver Collectin 1 (CLL1), Renal Collectin 1 (CL-K1), Ficolin-1, Ficolin-2 and Ficolin-3. Additionally, we will analyze also pulmonary surfactant D (SP-D), which, as mentioned, does not activate complement (it recognizes mannose, however, and is present both in the serum and in the respiratory system). Lately in In Poland, there were cases of childhood multiorgan inflammatory syndrome temporarily associated with SARS-CoV-2 (PIMS-TS). The disease usually develops 3-4 weeks after infection with the SARS-CoV-2 virus, common in children / adolescents who have had no (or had mild) COVID-19 symptoms. In patients PIMS-TS has a fever, in most cases severe abdominal pain, diarrhea, and / or vomiting. Complications that are particularly life-threatening are damage to internal organs, including the heart.