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Anti-Viral Activity of Plant Extracts and Herbs
Jill Davies, PhD |
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"Modern Medical discovery; it moves in mighty leaps - it leapt straight past the common cold and gave it us for keeps." Pam Ayres (from 'Oh No! I've got a cold.")
Go to your Doctor with a viral infection and, chances are, you'll be told 'you have a viral infection'. It isn't that your Doctor is being churlish or sadistic, it's just that, as far as prescription medication goes, nothing more can be done. You probably already know that antibiotics are of no use - though you could be forgiven for wondering 'why not?' - and when your Doctor starts to sound more like your Great-grandmother ("rest plenty, drink plenty, and don't overdo it") you might well find yourself wondering why the miracles of modern medicine don't extend to a nasty cold. As if to add insult to injury, viral infections can often leave one feeling even more wretched than bacterial infections, which can be treated with antibiotics and they also have a nasty tendency to linger - leave one feeling 'out of sorts' for some time, even once the initial acute disease has subsided.
The 'magic bullet' approach of modern medicine originated with the scientist Ehrlich. The idea was to 'blitz the bug and spare the host'. But this is not possible with a virus, as a virus only 'comes alive' when it becomes part of the host. This is why antiviral drugs lag so far behind antibiotics; there are only a handful. Luckily, however, whilst there are few effective antiviral drugs available, there are many plant extracts with proven antiviral activity.
 To understand how to treat viral infections we really have to understand what a virus is and how they infect us.
Over 400 different viruses are known to infect humans and cause diseases - ranging from the common cold to certain forms of cancer. A virus is really little more than a fragment of genetic material (RNA or DNA depending on the type of virus) enclosed within a protein 'coat' (known as a 'capsid') or to quote Peter Medawar's memorable description as 'simply a piece of bad news wrapped up in protein.'
One hurdle in understanding viruses is their size - if the microscopic bacteria are small, they dwarf viruses, which are many thousands of times smaller. Bacteria are single-celled living organisms. When a virus is not inside a host cell it has a stable crystalline structure - like salt or sugar. It's just a tiny inert lifeless particle - as long as it remains outside the cell. Viruses can exist in this inert crystal-like state indefinitely it would seem. Recently, some Italian investigators discovered intact smallpox viruses in a human mummy from about 1000AD. The scientists were amazed to find they could culture the crystals of viruses and infect living cells.
Viruses are not capable of living outside their host, but, once inside their host, they are capable not only of hijacking the cells to reproduce copies of themselves many times over, but also of mutating so swiftly that the body's immune system is always aiming at a moving target.
The Virus Replication Cycle
The outside of every human cell is covered with many types of receptor, each type forming a special 'docking bay' for the various chemical messengers used to communicate between cells. For a virus to enter a host cell, the surface of the viral coat must fit exactly into receptor sites on the cell surface. If the fit is not precise then the viral information (the RNA and DNA depending on the type of virus) cannot enter the cell. This exactness of fit explains why viruses are species-specific. They will not infect cells of totally different species. Even in an ideal match-up only one out of every few thousand encounters between virus and cell will end up in the proper binding of the two causing infection which is lucky for us since we swim in a sea of invisible microbes.
Once a virus has attached to a receptor and bound to it, the receptor then acts as a channel through which the genetic information can travel into the cell. The virus then effectively hijacks the cell's own genome (its genetic program) by splicing itself into the cell's genetic code.
The new program inside the cell now takes over all the specialised machinery - the organelles - to its own purpose - manufacturing viral subunits, copies of the viral coat (the capsid) and all the enzymes and chemical messengers necessary to assemble many copies of the virus itself. This rogue assembly line is so effective that eventually the host cell bursts, releasing thousands of copies of the virus into the bloodstream. Each one of these new viruses is now ready to infect other healthy cells.
Diseases caused by viral infection, include: colds, flu, hepatitis (inflammation of the liver), mononucleosis (glandular fever), shingles, childhood diseases like measles, mumps, rubella and chickenpox, warts and verrucas, some forms of meningitis and encephalitis, polio, rabies, AIDS, and some forms of leukaemia and cancer.
The herbal approach to viral infection is two pronged:
· To stimulate the immune system and thus produce more immune cells and
immune chemicals.
· The specific use of antiviral herbs to disrupt the replication cycle so it cannot survive.
To support the immune system, herbalists have traditionally employed herbs that contain chemicals known by the tongue twisting designation "High Molecular Weight heterogenous polysaccharides". Certain types of these chemicals enhance the body's general immunity, for instance by increasing the total number of lymphocytes and helper T-cells or the activity of natural killer cells or macrophages (the 'pac-man' type of cell which gobbles up invaders) or by increasing the number of immune stimulating messenger molecules known as cytokines (e.g. interferon, interleukins).
Immune enhancing polysaccharides have been identified in herbs such as Siberian ginseng, astragalus, liquorice, bladderwrack and saw palmetto.
Traditionally, immune enhancing herbs like these are combined with those that increase the action of the eliminative channels. Detoxification and elimination is
fundamental to the enhancement of immune function. Herbs to support the eliminative channels include marshmallow and rehmannia for the kidneys, mullein and lobelia for the lungs, burdock and fenugreek for the skin and barberry and gentian for the digestion. The addition of herbs containing insulin, for instance burdock and elecampane, helps to balance blood sugar levels which is essential because fluctuations, either too high or too low, can considerably compromise immunity.
Nervines like skullcap and lobelia are often useful alongside these herbs to ease tension and counteract the action of stress, which is well-known to lower immunity.
The role of these immune enhancing herbs as part of a broad systemic treatment cannot be over-estimated - ultimately the body's own defences are strengthened and recovery is therefore faster and complete. However, specific antiviral plants can also be of significant use in dealing with the "speeding" up of the destruction of the virus by the immune system, which is ultimately the only way of overcoming a viral infection.
Antiviral compounds from herbs interrupt the virus replication cycle at one of these stages. For example, the chemical known as prunellin (a sulphated polysaccharide) from Self-Heal (Prunella vulgaris) blocks the receptor used by the HIV virus so the virus cannot 'dock'. A different chemical from nettle roots (UDA - an N-acetylglucosamine specific lectin) inhibits the same virus but by preventing the genetic information from the virus fusing with the host cell's genome.
Some compounds work by interfering with the enzymes needed to make copies of virus components. Pokeweed antiviral protein works in this way, as does baicalin (from Plantain) and Skullcap. These are all herbs found growing in our gardens, lawns and roadsides.
Acute viral infections are a head on crash between a virus and the immune system. Unlike bacterial infections which gradually increase in their virulence, viral infections have what is known in the trade as a "one-step growth-curve". A virus, once it has penetrated the host cell is no longer detectable (this is known as viral eclipse). It has the time to replicate itself many times over, totally unhindered by the immune system tucked away neatly inside its cosy host. Only releasing all these thousands of viruses when the cell literally bursts at the seams. One moment you are hale and hearty, the next POW! you are in the full throes of a major acute infection.
An acute infection is however not the only way a virus interacts with its host. Over the many generations of co-evolution viruses and hosts have adapted to each other. Even the common cold was a deadly plague 5,000 years ago, when it was a new kid on the block. Some viruses instead of precipitating an acute episode lie dormant within the hosts body - no viral proteins or particles are produced and these latent viruses remain in a state of suspended animation until the immune system weakens through stress, bacterial infection, accumulated toxins, or nutritional deficiency when, just when you needed it least, the virus makes the most of the lowered line of defence to have an outing itself. The herpes viruses are the archetypal examples of persistent latent viral infection. Cold sores the day before your most important interview, blind date, or family photo opportunity come courtesy of this very process of persistent latent viral infection. Post viral syndromes like Chronic Fatigue Immune Deficiency Syndrome (CFIDS), a disease previously known as just CFS or ME also appears to be a persistent viral infection. Epstein-Barr virus (EBV - the virus that causes glandular fever), herpes virus number 6 (HSV6) and a retrovirus (the same type of virus as HIV and human leukaemia viruses) have all been put forward as the possible cause.
The worst plague of all time was not AIDS or the Bubonic plague but more recently in 1918, it wiped out about 40 million people in just a matter of months. No pandemic before or since has killed more in such a short time. In that year you could have been arrested for sneezing in public.
The disease? 'Flu.
Influenza, a disease once thought to be the result of the influence of celestial transits, really has been the most dreadful viral disease in human history. What has made it such a scourge? Well, firstly, it is an RNA virus and so has a mutation rate up to 1 million times faster than DNA viruses. Only one other virus, HIV, mutates faster. Such changes mean that the needed remedies to stop the virus are continually changing, like shooting at a moving target. This process, known as 'antigenic drift' lies behind the yearly flu epidemics.
Flu doesn't just infect human's either, but also pigs and ducks. Ducks for example often have several different strains of 'flu thriving in the digestive tract with no apparent effect but such close proximity of different strains very occasionally results in a genetic reshuffle producing a recombinent strain of increased virulence. The 1918 epidemic was a recombinent strain created in a pig cell - the epidemic was referred to as 'Swine flu'. With flu there are two proteins on the viral coat, which determine the shape of the key, which needs to fit the host cell receptor to cause infection. They are known as H (for haemoglutinin) and N (for Neuraminidase). There are at least 14 different subtypes of H antigen and 9 of N antigen. Each subtype of H or N is totally different - the antibodies for one are no good for another. The combination of the two antigens gives the designation for the 'flu viruses success. Over 140 subtypes of the virus, each mutating over a million times faster than DNA and occasionally being spliced together in the new combination in the bellies of pigs and ducks. Truth as they say?..
In 1969 the US surgeon general, William H Stewart made the now infamous statement "the war against infectious disease has been won". He couldn't have been more wrong.
In the modern era of AIDS, and under the threat of biological warfare, of Ebola, of emergent viruses and persistent latent viral infection, antiviral compounds will be needed for some years yet. The briefest glance over the way the world's most deadly virus - influenza, - chops and changes might warn us to be on the look out for new antiviral herbal and plant compounds.
If you are reading this you are a survivor. We are the progeny of all the survivors of viral disease back across the entire history of our own species - but the viruses surrounding us today are not only those who have passed the evolutionary test but those new Frankenstein's created by human disturbance of the earth's own balance and immunity. Global warming, intensive farming, pollution, GM crops, deforestation, the economical exploitation of the developing world all create niches for viral replication and more worryingly for recombinent viruses to emerge.
Alongside antiviral and viral evolution the plant kingdom has been exposed to similar selection processes producing antiviral and immune stimulant properties and compounds. Many of the chemicals used by the plant to protect from viral infection also have antiviral activity in higher species. Using those antiviral herbs in combination with good nutrition and a healthy lifestyle can continue to combat viral attacks and maintain our legacy as survivors.
© Copyright Wholistic Research 2003
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