BREAKING! Australia Now Turning To Oysters As A Cure For COVID-19! Cavortin A Compound Found In Oysters Could Be A Potential SARS-CoV-2 Antiviral!
: Maybe as a result of an oversupply of Pacific oysters due to a trade spat with China, Australians are desperate to find alternative uses for their oysters or maybe there is some scientific basis after all since a study has been published in the peer reviewed journal: Reviews In Medical Virology, showing the possible benefits of hemoplymph from Pacific oysters (Crassostrea gigas) as an antiviral against the SARS-CoV-2 coronavirus.
More importantly, the same study team actually conducted a vitro study confirming the efficacy of hemoplymph from Pacific oysters (Crassostrea gigas) as an antiviral against the SARS-CoV-2 coronavirus as the team tested the antiviral activity of Pacific oyster's hemolymph against a human coronavirus, HCoV-229E. An eight-fold reduction in infectivity of HCoV-229E on Huh-7 cells was observed in the presence of 10% C. gigas
hemolymph. Antiviral activity of C. gigas
hemolymph positively correlated with its concentration and appears to be active during an intracellular stage of HCoV-229E infection.
That study was published as a preprint format and is currently undergoing peer review.
The study team from, Flinders University, Bedford Park, South Australia found that Pacific oysters have antiviral activity against the human coronavirus HCoV-229E.
The HCoV-229E is a coronavirus strain and is one of the viruses responsible for the common cold. The virus has infected both humans and bats. While the SARS-CoV-2 is wreaking havoc worldwide, the study team purposefully selected HCoV-229E for the study because it can be handled safely in laboratories, making it more accessible for coronavirus research.
The SARS-CoV-2 Antivirals
study lead by Dr Peter G. Speck of Flinders University, found that Pacific oysters caused an eight-fold reduction in cells infected with HCoV-229E.
Interestingly antiviral activity occurred in a concentration-dependent manner and most likely targeted the intracellular stage of HCoV-229E infection.
The study findings may help with producing antiviral strategies against coronaviruses such as SARS-CoV-2. In addition, the researchers suggest future research may want to identify the compound that gives Pacific Oysters its antiviral abilities.
For the study, Huh-7 cells were collected and stained with 0.4% trypan blue. In addition, 12 C. gigas oysters that were grown in South Australia were used.
Upon opening the C. gigas oysters, hemolymph was taken out of the pericardial cavity, sterilized, and stored in the fridge.
Hemolymph, or haemolymph, is a fluid, analogous to the blood in vertebrates, that circulates in the interior of the arthropod (invertebrate) body, remaining in direct contact with the animal's tissues. It is composed of a fluid
plasma in which hemolymph cells called hemocytes are suspended.
During the study, Huh-7 cell death increased as hemolymph concentration surpassed 10%, making 10% the cap for concentration use in assays.
The study findings revealed that Huh-7 cells in 10% C. gigas hemolymph were found to show antiviral activity when exposed to HCoV-229E. An eight-fold reduction was found in the HCoV-229E titer, indicating an 87.5% antiviral activity.
The antiviral activity appears dose-dependent. A positive correlation was observed between antiviral activity and the concentration of C. gigas hemolymph.
The study team note the dose-dependent activity is similar to what’s observed with the C. gigas hemolymph protein, cavortin, against HSV-1.
The team suggest that antiviral effects most likely occur during an intracellular stage of infection.
Past studies suggest antiviral activity was highest when C. gigas hemolymph was added 0-2 hours after HSV-1 infection suggesting the effect was exerted after virus attachment and entry.
In order to study this for HCoV-229E infection, the study exposed Huh-7 cells to HCoV-229E infection where the C. gigas hemolymph was added immediately or 1 hour after infection.
Interestingly there was no difference in antiviral activity when the oysters were placed right after infection or after an hour.
As a result of Huh-7 cells showing no changes in antiviral activity, the study team suggest C. gigas hemolymph exerts its effects during an intracellular stage of HCoV-229E infection.
It should be noted that other research in this field has confirmed the presence of antiviral compounds during an intracellular stage of HCoV-229E infection. For example, FK06, an immunosuppressive compound stops viral replication in Huh-7 cells, and thapsigargin disrupts the intracellular stage by blocking replication or activating unknown antiviral effector systems in Huh-7 cells.
Antivirals From The Sea
The effectiveness of mollusc-derived antiviral agents has been proven in many different laboratory and animal studies, while its efficacy against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has also been proposed by recent in silico studies.
According to the study team, marine invertebrates represent an unexploited source of medicinal compounds. More specifically, marine organisms of the phylum Mollusca have miraculous innate immunity, which also entails the production of powerful antiviral compounds.
Currently the only antiviral drug derived from marine invertebrates that is available on the market is known as vidarabine; however, this compound subsequently inspired the design of acyclovir (drug that we used against herpesviruses) and zidovudine (one of the first drugs used in the treatment of HIV-infection).
The to date success of these drugs thus exemplifies how marine invertebrates are not only a direct source of antiviral compounds but can also inspire the synthesis of entirely new ones. And taking into account the fact that there are approximately 100,000 species in the aforementioned phylum, mankind barely scratched the surface on the opportunity here.
However, despite the proven activity of many mollusc-derived antivirals in vitro
(which includes human viruses), as well as their diverse mechanisms of action, they were not used clinically yet. One of the reasons is that their modes of action are not entirely elucidated.
Researchers know that the lipophilic digestive gland extract and the circulatory fluid of greenlip abalone (Haliotis laevigata
) can inhibit the entry or hamper early intracellular stage of the infection with the herpes simplex virus type 1 in Vero cells (i.e., kidney epithelial cells extracted from an African green monkey).
Importantly, the inhibition of herpes simplex virus type 1 has also been seen in vitro with the extracts from the European flat oyster (Ostrea edulis
), common cockle (Cerastoderma edule
), the common whelk (Buccinum undatum
), Japanese carpet shell (Ruditapes philippinarum
), blacklip abalone (Haliotis rubra
), the Mediterranean mussel (Mytilus galloprovincialis
) and veined rapa whelk (Rapanosa venosa
The potent antiviral activity of certain molluscs also extends to other herpesviruses (such as Epstein-Barr virus), while oyster hemolymph also harbors compounds active against infectious pancreatic necrosis virus and human adenovirus type 5.
Pacific Oysters (Crassostrea gigas)
It is known that intracellular zinc shows high inhibitory activity against various coronaviral enzymes-most notably 3C-like and papain-like proteases and RNA-dependent RNA polymerase pivotal for viral replication. Therefore, zinc has the propensity to act as a therapeutic agent for SARS-CoV-2, which can be improved by coupling with a metal chaperone.
Interestingly the Pacific oyster (Crassostrea gigas) has a high zinc content and also contains cavortin (its major hemolymph protein) as a metal chaperone, it is indeed possible that there is a potential antiviral activity against SARS-CoV-2.
Also, it may also act as a metal chaperone which enables the movement of zinc into host cells.
To date, the specific mechanism behind cavortin’s antiviral activity is still unknown, and there is also a question of its bioavailability in cell culture and animal models. However, the unexplored potential for a new antiviral compound against SARS-CoV-2 is definitely tempting.
It should be noted that there is a problem of a stringent biosafety level for laboratories working with SARS-CoV-2. However, during the initial screening endeavors, common cold coronaviruses can be used in order to screen compounds with potential universal action. In any case, the remarkable diversity of molluscs may again play in our favor.
The study team is now in the midst of initiating actual clinical trials in Australia using hemoplymph from Pacific oysters (Crassostrea gigas)
to treat COVID-19 patients.
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