Some fucoidans have been shown to block the entry of coated viruses to cells, thereby potentially preventing or halting the progress of infections. Undaria pinnatifida fucoidan produced by Marinova has been shown to be a highly effective in vitro inhibitor of Herpes Simplex viruses (HSV1 and HSV2) (Thompson, 2004). In addition, other fucoidan extracts have demonstrated protection against Herpes virus infection (Hayashi, 2008; Hayashi, 2008). Fucoidans have also demonstrated potential to inhibit influenza viruses (Hayashi, 2008). Oral delivery of an Undaria pinnatifida fucoidan extract has been shown to inhibit lung damage and clinical signs of respiratory infection in vivo via indirect anti-inflammatory activity. Research in a severe Influenza A H1N1 mouse model using orally administered Undaria pinnatifida fucoidan produced by Marinova (equivalent to 1-2g day human dose) showed attenuation of both clinical signs and lung damage (Richards, 2020). The mechanism of action appeared to be modulation of pathology, rather than inhibition of virus, indicating that this particular fucoidan may have utility regardless of the pathogen causing damage.
In vitro, some fucoidans have been shown to inhibit several different strains of influenza, including H1N1 (Hayashi, 2008; Wang, 2017), H5N1 (Makarenkova, 2010), H5N3 and H7N2 (Synytsa, 2014) and parainfluenza (Taoda, 2008). Clinically, one fucoidan extract reduced pro-viral loads in patients with HTLV-1 (Araya, 2011) and another showed benefits for patients with chronic hepatitis C (Mori, 2012). Other fucoidan extracts have also been shown to exhibit activity against Newcastle virus (Elizondo-Gonzalez, 2012), canine distemper (Trejo-Avila, 2014) and the measles virus (Morán-Santibañez, 2016).
Compromised lung function is a feature of both infection driven and non-infective pathologies. Viral infections, including the pandemic strain SARS-CoV-2, that affect lung function can cause both acute and long-term chronic damage. SARS-CoV-2 infection suppresses innate immunity and promotes an inflammatory response. Targeting these aspects of SARS-CoV-2 is not only important as the pandemic affects greater proportions of the population, but is also important in addressing regular colds and flu. In clinical and animal studies investigating general immune functions, various fucoidan extracts have been shown to increase innate immunity and decrease inflammation (Kuznetsova 2020, Fitton 2015, Fitton 2019). In addition, high purity fucoidan extracts produced by Marinova have been shown to attenuate pulmonary damage in a model of acute viral infection (Richards, 2020). A recent review published by Marinova (Fitton, 2021) summarizes the current research on fucoidan with regard to viral lung infections and lung damage and highlights key areas for further research in this application.