ABSTRACT
The first-ever recent Marburg virus (MARV) outbreak in Ghana, West Africa and Equatorial Guinea has refocused efforts towards the development of therapeutics since no vaccine or treatment has been approved. mRNA vaccines were proven successful in a pandemic-response to severe acute respiratory syndrome coronavirus-2, making it an appealing vaccine platform to target highly pathogenic emerging viruses. Here, 1-methyl-pseudouridine-modified mRNA vaccines formulated in lipid nanoparticles (LNP) were developed against MARV and the closely-related Ravn virus (RAVV), which were based on sequences of the glycoproteins (GP) of the two viruses. Vaccination of guinea pigs with both vaccines elicited robust binding and neutralizing antibodies and conferred complete protection against virus replication, disease and death. The study characterized antibody responses to identify disparities in the binding and functional profiles between the two viruses and regions in GP that are broadly reactive. For the first time, the glycan cap is highlighted as an immunoreactive site for marburgviruses, inducing both binding and neutralizing antibody responses that are dependent on the virus. Profiling the antibody responses against the two viruses provided an insight into how antigenic differences may affect the response towards conserved GP regions which would otherwise be predicted to be cross-reactive and has implications for the future design of broadly protective vaccines. The results support the use of mRNA-LNPs against pathogens of high consequence.
Subject(s)
Coronavirus Infections , DeathABSTRACT
The infection caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) resulted in a pandemic with huge death toll and economic consequences. The virus attaches itself to the human epithelial cells through noncovalent bonding of its spike protein with the angiotensin-converting enzyme-2 (ACE2) receptor on the host cell. We hypothesized that perturbing the functionally active conformation of spike protein through reduction of its solvent accessible disulfide bond, thereby disintegrating its structural architecture, may be a feasible strategy to prevent infection. Proteomics data showed that N-acetyl cysteine (NAC), an antioxidant and mucolytic agent been widely in use in clinical medicine, forms covalent conjugates with solvent accessible cysteine residues of spike protein that were disulfide bonded in the native state. In silico analysis indicated that this covalent conjugation perturbed the stereo specific orientations of the interacting key residues of spike protein that resulted in threefold weakening in the binding affinity of spike protein with ACE2 receptor. Antiviral assay using VeroE6 cells showed that NAC caused 54.3% inhibition in SARS-CoV-2 replication. Interestingly, almost all SARS-Cov-2 variants conserved cystine residues in the spike protein. Our observed results open avenues for exploring in vivo pharmaco-preventive and therapeutic potential of NAC for Coronavirus Disease 2019 (COVID-19).