Plant Lectins Fight Viruses in Studies

mannose-binding lectins

Low lectin levels are linked to many conditions.

Scientific research finds that lectins from plants can treat lethal viruses such as Ebola. SARS (severe acute respiratory syndrome) and the feline infectious peritonitis virus (FIPV). And low lectin levels have been linked to a number of dangerous diseases.

Other research has found that Ebola virus requires more than contact with a symptomatic patient: It also requires an immune system unable to defend itself against the virus.

This lack of defense can come in the form of immunosuppression, but it can also come from a deficient production of mannose-binding lectins, which may well be the result of a poor diet or other stress factors that erodes the immune system.

As investigators have found over the past decade of research on not just viruses, but many other infectious diseases, part of immunosuppression comes in the form of a lack of production of mannose-binding lectins.

These natural biochemicals are produced by a healthy immune system and they have the distinction of being able to break apart glycoproteins that cover many viruses, as well as certain bacteria and yeasts.

Some of these dangerous microbes use these glycoprotein envelopes to protect themselves from the immune system, and to help them penetrate cell membranes – which also have glycoproteins in their membranes.

As such a glycoprotein enveloped virus or microorganism penetrates the cell membrane, it can wreck its havoc upon the cell.

Viruses do this by inserting genetic information that hijacks the DNA and RNA of the cell – making the cell a clone for the virus to replicate.

Lectin deficiencies implicated in many diseases

The mechanisms mentioned above with regard to mannose-binding lectins are not anecdotal. They come from a flurry of research.

To be precise, researchers have found in numerous studies that deficiencies in mannose-binding lectins in the bloodstream have are associated with the following diseases:

  • Research from the Graduate School of Dalian Medical University found that sepsis patients had significantly lower mannose-binding lectin levels in their blood compared to healthy control patients.
  • University of Ottawa researchers found that patients with tuberculosis had significantly lower blood levels of mannose-binding lectins.
  • Research from Copenhagen University Hospital found in a study of 98 kidney disease patients that those with higher mannose-binding lectin levels had better cardiovascular health, as measured by pulse wave velocity. Lower pulse wave velocity levels were associated with higher mannose-binding lectin levels. Higher pulse wave velocity levels are associated with less artery elasticity.
  • Research from Argentina’s CONICET and the Laboratorio de Biología Molecular in Buenos Aires found that insufficiencies in mannose-binding lectin levels lead to greater risk of severe infantile cystic fibrosis. Even among those with CFTR mutations, higher mannose-binding lectin levels had better outcomes.
  • University of Liverpool researchers found that lower mannose-binding lectin levels were associated with a higher risk of recurrent Clostridium difficile infections. MBL did not appear to reduce the risk of initial infection, however. The researchers stated: “Serum MBL concentration …. was associated with Clostridium difficile infection recurrence, indicating that MBL acts as a modulator of disease, rather than a predisposing factor.”
  • An Italian review of five studies found that mutations of the MBL2 gene – which can predispose a person to reduced MBL levels – was associated with a greater risk of vulvovaginal candidiasis – Candida infections of the vagina.
  • Researchers from Italy’s Bambino Gesù Children’s Hospital found that infants with MBL2 gene mutations (resulting in lower levels of mannose-binding lectins) had a greater risk of neurological conditions.
  • Research from China’s General Hospital of Southern Medical University found that newborns with lower mannose-binding lectin levels had significantly greater risk of contracting neonatal sepsis.
  • Research from Spain’s Hospital University of Bellvitge found that low levels of mannose-binding lectins in the blood are associated with greater inflammation levels in kidney patients.
  • Researchers from the Duke University School of Medicine found in a small study that low levels of MBL were significantly associated with recurring sinusitis. They found infections of Staphylococcus aureus and Pseudomonas aeruginosa were more evident among low MBL patients.
  • Research from the Korea University College of Medicine found after reviewing 12 studies that included over 3,500 people with rheumatoid arthritis and primary Sjögren’s syndrome that lower MBL levels were associated with higher levels of RA and Sjögren’s syndrome – as determined by genotype.
  • Research from Poland’s Institute of Medical Biology found that ovarian cancer was associated with MBL deficiency, as determined by genotype. They concluded that ovarian cancer was associated with alterations in MBL genes.
  • Research from China’s TianJin People’s Hospital found that low levels of mannose-binding lectins were associated with a greater risk of death from pneumonia. They stated in their conclusion: “Both the mannose-binding lectin and C-reactive protein [tests] can serve as inflammatory markers in predicting the outcome of patients with community-acquired pneumonia.”
  • Spanish researchers found that lower mannose-binding lectin levels were associated with severe respiratory insufficiency in influenza A virus infections.
  • Research from Australia’s Royal Adelaide Hospital found that lower mannose-binding lectin levels resulted in greater COPD severity.
  • Research from Brazil and New York’s Weill Cornell Medical College found that postmenopausal women with lower MBL levels – found from MBL genotypes (codon 54 polymorphism) – had greater risk of hypertension and insulin resistance.
  • University of Chieti researchers found that higher mannose-binding lectin levels were associated with greater repair following traumatic brain injuries.
  • University of Barcelona researchers found that mannose-binding lectin deficiencies was associated with a greater risk of invasive pneumococcal disease (IPD).
  • Researchers from Seoul’s University of Ulsan College of Medicine found that persistant infections with Staphylococcus aureus was significantly associated with deficiencies of mannose-binding lectins in the bloodstream.
  • University of Edinburgh researchers found that Mannose-binding lectin deficiency is associated with non-cystic fibrosis bronchiectasis – a condition of damaged bronchial passages.
  • Research from Japan’s Ritsumeikan University found that mannose-binding lectins had anticancer properties. The researchers studied 330 patients with colon cancer and found that mannose-binding lectins will bind to tumors in attempts to heal the tissues. Those patients with tumors bound with mannose-binding lectins had a more favorable prognosis.
  • We can add to this the research availed in and enveloped viruses such as herpes, HIV, hepatitis-C, H1N1, Ebola and SARS.
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mucosal membranes

Mannose-binding Lectins from Plants

Speaking of SARS, an important study from The Netherlands’ University of Gent studied plant-derived mannose-binding lectins on SARS (severe acute respiratory syndrome) and the feline infectious peritonitis virus (FIPV).

The researchers studied known plant lectins from 33 different plants. The researchers utilized Vero E6 cells to determine the ability of these lectins to inhibit the replication of the two viruses.

The cells were infected with SARS and the FIPV viruses with three and four day incubation period to allow for significant replication of the viruses. Then each of the mannose-binding lectins from each plant species – specifically agglutinins that have been shown to be active in humans – were tested against the two viruses.

Of the 33 plant lectins tested, 15 were significantly antiviral against both the SARS and the FIPV viruses. In addition, five lectins were antiviral against only the SARS and two were antiviral against only the FIPV, and only eight of the lectins were not antiviral against any of the viruses.

Those antiviral lectins were successful in inhibiting the replication of the viruses.

Here is the list of the mannose-binding plant lectins that were antiviral against both the SARS and FIPV viruses from the research:

  • Amaryllis (Hippeastrum hybrid)
  • Snowdrop (Galanthus nivalis)
  • Daffodil (Narcissus pseudonarcissus)
  • Red spider lily (Lycoris radiate)
  • Leek (Allium porrum)
  • Ramsons (Allium ursinum)
  • Taro (Colocasia esculenta)
  • Cymbidium orchid (Cymbidium hybrid)
  • Twayblade (Listera ovata)
  • Broad-leaved helleborine (Epipactis helleborine)
  • Tulip (Tulipa hybrid)
  • Black mulberry tree (Morus Nigra)
  • The other plant lectins that were antiviral against both included:
  • Tabacco plant (Nicotiana tabacum)
  • Stinging nettle (Urtica dioica)

Here are the plants whose lectins that were antiviral but not against both viruses:

  • Solomon’s Seal (Polygonatum multiflorum)
  • Mistletoe (Viscum album)
  • Iris (Iris hybrid)
  • Yellow wood (Cladastris lutea)

Note that both SARS and FIPV and extremely virulent because of their envelopment with glycoproteins that protect the virus against many agents as well as provide a means into the cell.

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In my previous paper, I investigated the research on two species of red algae shown to contain mannose-binding lectins having antiviral properties against herpes, HIV, Hepatitis-C and Ebola, as well as SARS. These viruses have similar glycoprotein envelopes.

The bottom line from this study is that mannose-binding lectins are available from plants. Yes, our body produces mannose-binding lectins and these are important factors in our immune system that allow us to fight various infections and diseases.

But the research clearly illustrates that we can supplement our bodies with plant-provided mannose-binding lectins. And for those of us who might be deficient in MBL, we can supplement with our MBLs with those provided by plants, which would include those listed above along with red algae.

To these we can add that Argentina researchers found that mannose-binding lectins from sunflower seedlings were antifungal.

And researchers from the Tokyo Medical and Dental University also found that plant-derived mannose-binding lectins exhibited antifungal properties.

Protecting our body’s Mannose-binding Lectin capacity

Research has found that between 7% and 30% of the population among Western countries is deficient in mannose-binding lectins. Interestingly, U.S. research has indicated between 7-10%, while research in the UK has indicated between 10% and 30%.

Does this mean we are born with a MBL deficiency from mutations among the MBL2 gene?

While this is an emerging topic and there is more research to be done, there is clear evidence that our lifestyles have a lot to do with our body’s innate ability to produce mannose-binding lectins.

Researchers from the University of Ottawa and China’s Central South University tested 205 tuberculosis patients along with 216 control subjects, and found that mannose-binding lectin levels can be reduced by the following:

  • Smoking or secondhand smoke exposure
  • Exposure to solid cooking fuel exhaust

These relationships are revealed by the study from Australia’s Royal Adelaide Hospital that showed high levels of oxidative stress reduced levels of mannose-binding lectins via oxidation – whereby the lectins were oxidized (oxMBL).

The researchers also found the oxidation of MBL created dysfunctional macrophage activity – which decreased the ability of the patients to fight their lung infections.

When we put the pieces together – of MBL being oxidized together with the effects of smoking and carbon monoxide exposure (the result of solid fuel cooking) – which other research has found causes higher levels of oxidative stress – we find a clear relationship between healthy lifestyles and higher MBL levels.

If we then combine in the research laid out above related to the relationships between mannose-binding lectin deficiencies and a number of disease scenarios, we can correlate that diet also has a lot to do with our MBL levels.

The reality is that our diets can be either alkaline or acidic. Alkaline diets are known for their ability to reduce oxidation within the body because they contain more antioxidants.

On the other hand, diets that are more acidic – meaning they have fewer antioxidants and produce more free radicals – would by default also reduce the body’s mannose-binding lectin levels.

Sun and vitamin D levels may also predispose higher MBL levels. University of Copenhagen research found in a study of nearly 1,000 children that mannose-binding lectin levels were lower in the wintertime and higher in the summertime.


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