Blockade of TMPRSS2-mediated priming of SARS-CoV-2 by the N-terminal peptide of lactoferrin

In addition to vaccines, there is an urgent need for supplemental antiviral therapeutics to dampen the persistent COVID-19 pandemic caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). The transmembrane protease serine 2 (TMPRSS2), which is responsible for the proteolytic processing of the SARS-CoV-2 spike protein as virus priming for cell entry, appears as a rational therapeutic target for the clearance of SARS-CoV-2 infection. Accordingly, selective inhibitors of TMPRSS2 represent potential tools for prevention and treatment of COVID-19. Here, we tested the inhibitory capacities of the human milk glycoprotein lactoferrin and its N-terminal peptide pLF1, which we identified as inhibitors of plasminogen, a serine protease homologous to TMPRSS2. In vitro proteolysis assays revealed that, unlike full-length lactoferrin, pLF1 significantly inhibited the proteolytic activity of TMPRSS2. pLF1 inhibited both the proteolytic processing of the SARS-CoV-2 spike protein and the SARS-CoV-2 infection of simian Vero cells. Because lactoferrin is a natural product and several biologically active peptides, such as the N-terminally derived lactoferricins, are produced naturally by pepsin-mediated digestion, natural or synthetic peptides from lactoferrin represent well-achievable candidates for supporting prevention and treatment of COVID-19.

Humoral and cellular immune responses and their kinetics vary in dependence of diagnosis and treatment in immunocompromised patients upon COVID-19 mRNA vaccination.

BackgroundKnowledge about humoral and cellular immunogenicity and their kinetics following SARS-CoV-2 mRNA vaccinations in immunosuppressed patients is limited. MethodsAntibody and cytokine responses were assessed in 263 patients with either solid tumors (SOT, n=63), multiple myeloma (MM, n=70) or inflammatory bowel diseases (IBD, n=130) undergoing various immunosuppressive regimens and from 66 healthy controls before the first and the second, as well as four weeks and 5-6 months after the second mRNA vaccine dose with either BNT162b2 or mRNA-1273. FindingsFour weeks after the second dose, seroconversion was lower in cancer than in IBD patients and controls, with the highest non-responder rate in MM patients (17.1%). S1-specific IgG levels correlated with neutralizing antibody titers. While antibody responses correlated with cellular responses in controls and IBD patients, IFN-{gamma} and antibody responses did not in SOT and MM patients. At six months, 19.6% of patients with MM and 7.3% with SOT had become seronegative, while IBD patients and controls remained seropositive in 96.3% and 100%, respectively. Vaccinees receiving mRNA-1273 presented higher antibody levels than those vaccinated with BNT162b2. InterpretationCancer patients may launch an inadequate seroresponse in the immediate time range following vaccination and up to six months, correlating with vaccine-specific cellular responses. These findings propose antibody testing in immunosuppressed - along with cellular testing - provides guidance for administration of additional vaccine doses, or may indicate the necessity for antibody treatment. IBD patients respond well to the vaccine, but treatment such as with TNF- inhibitors may reduce persistence of immune responses. FundingThe study was sponsored and financed by the Medical University of Vienna - third party funding by the Institute of Specific Prophylaxis and Tropical Medicine. AOR. and HS acknowledge funding by the Austrian Science Fund (FWF, P 34253-B).