Abstract
Global processes, such as climate change, frequent and distant travelling and population growth, increase the risk of viral infection spread. Unfortunately, the number of effective and accessible medicines for the prevention and treatment of these infections is limited. Therefore, in recent years, efforts have been intensified to develop new antiviral medicines or vaccines. In this review article, the structure and activity of the most promising antiviral cyanobacterial products are presented. The antiviral cyanometabolites are mainly active against the human immunodeficiency virus (HIV) and other enveloped viruses such as herpes simplex virus (HSV), Ebola or the influenza viruses. The majority of the metabolites are classified as lectins, monomeric or dimeric proteins with unique amino acid sequences. They all show activity at the nanomolar range but differ in carbohydrate specificity and recognize a different epitope on high mannose oligosaccharides. The cyanobacterial lectins include cyanovirin-N (CV-N), scytovirin (SVN), microvirin (MVN), Microcystis viridis lectin (MVL), and Oscillatoria agardhii agglutinin (OAA). Cyanobacterial polysaccharides, peptides, and other metabolites also have potential to be used as antiviral drugs. The sulfated polysaccharide, calcium spirulan (CA-SP), inhibited infection by enveloped viruses, stimulated the immune system’s response, and showed antitumor activity. Microginins, the linear peptides, inhibit angiotensin-converting enzyme (ACE), therefore, their use in the treatment of COVID-19 patients with injury of the ACE2 expressing organs is considered. In addition, many cyanobacterial extracts were revealed to have antiviral activities, but the active agents have not been identified. This fact provides a good basis for further studies on the therapeutic potential of these microorganisms.
Highlights
Viruses and Viral Infections—A Global ProblemViruses are obligatory parasites composed of nucleic acids (DNA or RNA) packed in a protein capsid, in some cases enveloped with a lipid bilayer
Other classifications are based on morphological features and include enveloped and nonenveloped viruses, e.g., the Baltimore classification sorts viruses into groups based on the RNA production manner [2,3]
Besides interaction with human immunodeficiency virus (HIV) gp120 and inhibition of HIV infection, CV-N is active at a nanomolar level against other enveloped viruses such as simian immunodeficiency virus (SIV) and the chimeric SIV/HIV-1 virus (SHIV89.6P) [53], feline immunodeficiency virus (FIV), human herpes virus 6 (HHV-6), measles virus (MeV) [54], Ebola virus [55], hepatitis virus [56], and influenza virus [57], all with the N-linked high mannose oligosaccharides as glycoprotein components
Summary
Viruses are obligatory parasites composed of nucleic acids (DNA or RNA) packed in a protein capsid, in some cases enveloped with a lipid bilayer. A synthetic analogue of the compound, vidarabine, as an approved drug, inhibits the replication of viral DNA, and is effective in the treatment of herpes simplex virus (HSV-1 and HSV-2) and varicella zoster virus (VZV) [20] Natural products, such as flavonoids, oligostibens, coumarins and diarylheptanoids, are active against influenza virus neuraminidase [21]. The sulfated polysaccharides produced by marine algae belong to the broad-spectrum antivirals (BSAs) They disrupt different phases of viral infection by inhibition of attachment, penetration, uncoating, transcription and translation processes [23]. The aim of the current work was to review the existing knowledge on the antiviral compounds produced by cyanobacteria These prokaryotic, photosynthesizing microorganisms occur in all types of environments, including seas and oceans, lakes, rivers, hot springs, soil, rocks and ice [29]. Most of the studies were focused on lectins [33] and polysaccharides [34]
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