Microalgal-derived Compounds that Fight Viruses

  Algae Europe December 2022

Study: Evaluation of Microalgae Antiviral Activity and Their Bioactive Compounds.

Agroup of researchers in Italy studied the presence of a large number of microalgal-derived compounds that suggest the potential antiviral benefits of a diet enriched with microalgae, according to Dr. Liji Thomas, MD in news-medical.net as published in the journal Antibiotics.

Marine algae already contribute almost a tenth of biomedical molecules. Additionally, microalgae proliferate abundantly at low energy costs while producing high amounts of medicinal compounds.

Microalgae yield a variety of chemicals such as carbohydrate-binding proteins, called lectins, that bind directly to viral glycoproteins added post-translationally via specifically-oriented carbohydrate recognition domains; polysaccharides with sulfate groups and acidic polysaccharides; pigments; peptides and proteins; flavonoids and polyphenols; and glycolipids.

Types of antiviral compounds

Cyanobacterial lectins include Agglutinin OAA, Cyanovirin-N, Microcystis Viridis Lectin, Microvirin, and Scytovirin, from species such as Oscillatoria agardhii strain NIES-204, Nostoc ellipsosporum and Microcystis aeruginosa PCC7806. All of these inhibit a range of diseases such as human immunodeficiency virus (HIV) 1 and 2, hepatitis C (HCV), the hemorrhagic fever ZEBOV, influenza A, B, and herpes simplex (HSV).

Polysaccharides are produced by both spirulina and Porphyridium microalgae. Sulfate polysaccharides may occupy the viral attachment sites on the envelope via the negative charge on the sulfate group that binds to the positive charges on the envelope, creating a non-reversible complex.

Other promising sulfate-polysaccharides from spirulina include the calcium-spirulan, which is active against HIV1 and HSV, as well as the cytomegalovirus, mumps and influenza. 

Varicella zoster, murine leukemia virus and HSV are also inhibited by Porphyridium species.

Other microalgae produce sulfate polysaccharides that inhibit picornaviruses, those causing diverse conditions ranging from myocarditis and encephalitis, through neurological and reproductive diseases, to diabetes, and parainfluenza viruses, responsible for severe pediatric respiratory disease, as well as HIV, HSV, and mumps.

Microalgal pigments such as pheoporbide and carotenoids are used in biomedical applications on a wide scale. These may inhibit viral entry as well as having post-viral entry effects.

Carotenoids inhibit cytokine storm

Carotenoids, in particular, may counteract the cytokine storm implicated in severe COVID-19 by inhibiting the excessive production of antiviral reactive oxygen species and reactive nitrogen-oxygen species. While these are useful in reducing viral replication, they also activate transcription nuclear factor-KB, inducing the JAK/STAT inflammation pathway.

Since the cytokine storm also induces life-threatening acute respiratory distress syndrome (ARDS), and acute lung injury (ALI) associated with multi-organ damage, carotenoids may have a still higher utility beyond their direct effects on the virus.

Other pigments with antioxidant and antiviral activity include phycobiliproteins and astaxanthin. The latter is reported to reduce both ARDS and ALI.

Some microalgae produce peptides that show antiviral activity in aquaculture and in silkworms. Flavonoids have potent antiviral activity, such as marennine, a bluish-grey pigment from Haslea ostrearia, active against HIV and HSV. This can be manufactured in a bioreactor and is also used in food, coloring agents and cosmetics.

Glycolipids are likewise produced by microalgae, and some show potent virucidal effects against HSV2 and HIV, using different mechanisms of action such as DNA polymerase inhibition or damaging the viral envelope to promote viral lysis.

Potential for vaccine production

Apart from their compounds, microalgae have the ability to act as vectors expressing double-stranded RNA and thus interfere with viral mRNA to inhibit replication. One example is the green microalga Chlamydomonas reinhardtii, used against a shrimp virus.

Other vaccines could be created using microalga bioengineered in other ways.

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