Naked Science Forum
Life Sciences => Cells, Microbes & Viruses => Topic started by: diegostation on 09/05/2005 17:53:40
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Almost every week there are news about a possible new cure or vaccine for AIDS.
But those possible treatments seem to vanish and then another possible treatment appears on the news.
It seems that people are getting false hopes of an AIDS solution anytime soon.
So, have there really been any advancements on this field?
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This is a difficult one. As you can probably appreciate, it's now over 20 years since the French scientist Luc Montagnier identified HIV, in 1983, as the causative agent responsible for the immune-disabling disease AIDS.
At the time scientists thought that now they had the agent responsible, including its genetic sequence, that it would only be a matter of time before a vaccine could be produced to protect people from infection.
But, 22 years later, at least 45 million people have been infected with HIV, in 2002 alone there were 5 million new cases, 70% of them in sub-saharan Africa, and current predictions suggest 110 million cases by 2010.
This is a pandemic on an immense scale. Avian flu generates hysteria in the media, but at worst the 1918 Spanish 'flu killed 40 million people - far less than the number already infected with HIV (and hence destined to die unless we find an effective therapy).
The reason for this is that despite the best efforts of science, it has not been possible to produce a protective vaccine.
Part of the reason for this is that HIV is a very basic organism, termed a retrovirus, that uses a simple form of genetic material - called RNA - which is highly error-prone. The DNA found in our cells comprises 2 strands of genetic information, each the mirror-image of the other, meaning that the integrity of the information on one strand can be crossed-checked and repaired using the information on the opposite strand. But its RNA relative, used by HIV, comprises only one strand of genetic material, and frequently mistakes creep in when the virus copies its genetic material.
These mistakes alter the appearance of the virus, and how efficiently its molecular machinery operates. This presents a moving target to the immune system, making it difficult for the body to mount an effective response and clear the infection. If you add to that the fact that the virus is attacking and weakening the immune system itself, you can see straight away why HIV is such a problem.
The virus also hides itself away, in a latent form, within our own cells, periodically emerging to cause flurries of viral activity. So you therefore have a pathogen that is adept at the art of disguise, concealment, and immune-sabotage.
Nevertheless, scientists have been able to produce a panolply of anti-retroviral drugs which work by blocking the ability of the virus to copy its genetic material, hindering viral growth. But because HIV is constantly changing (mutating), it quickly overcomes the obstacle imposed by a single drug. As a result doctors now prescribe combinations of agents which attack the virus from several different angles at once, resulting in a so-called synergistic effect. This strategy is termed HAART or highly active anti-retroviral therapy, and has led to considerable improvements in patient survival, although the drugs themselves often produce severe side effects.
One downside of the use of these agents, apart from the side effects, is that the virus still eventually becomes resistant to their effects. And because many of the agents work in the same way, once the virus has circumvented the action of one, it is often also resistant to many of the other drugs in the same class that work the same way.
This has led to a progressive rise in the number of resistant forms of HIV in circulation within the community, meaning that people are now turning up to clinics with newly diagnosed HIV that is already resistant to some drugs.
More seriously, a man in New York presented earlier in 2005 with a form of HIV that was multiply drug-resistant and progressed to AIDS in just 4 months. Such mutliply-resistant forms of HIV can arise if a person who is already HIV-positive acquires a new form the virus from another person. If the two viral strains infect the same cell at the same time they can swap genetic material between themselves, breeding a 'supervirus' with all the worst features of both. This is likely to become an increasingly common problem as patients live longer, remain healthier, and feel better thanks to current therapies.
Thanks, in part, to these therapies there is presently an air of complacency about HIV to the extent that infection rates have risen considerably again, particularly amongst young people. This is almost certainly caused by an upswing in the practice of unprotected sex, and we know this because figures for other sexually transmitted infections have surged. If young people were practising safe sex (which means using barrier forms of contraception, rather than just not becoming pregnant which is most people's definition of safe sex !) then we wouldn't be seeing one girl in 10 between the age of 16 and 19 testing positive for chlamydia in the UK, and 1 woman in 4 in America testing positive for HSV-2, the genital form of herpes.
Chris
"I never forget a face, but in your case I'll make an exception"
- Groucho Marx
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Wow, no one's more clear than you man, by the way, what about a vaccine for aids? is there really a possibility for one? do you think it could come out earlier than a cure?
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Chris - thanks for a very understandable explanation of what a retrovirus is. I've heard the term bandied around often enough but never actually known what 1 was.
In your expert opinion, as the HIV virus is, as you phrased it, "adept at the art of disguise, concealment, and immune-sabotage.", do you think it will ever be possible to produce an effective method of curing it? Or will it just continue to be a rear-guard war of limited suppression?
Having lived in Uganda I've seen the devastation AIDS can cause. And, of course, it's not just those who have the disease who are affected. If parents have AIDS & are thus unable to work & earn money, or worse still, if they have died, it leaves the children in a parlous situation. I've seen villages where 90% of the adults have died of HIV. Without those adults to raise crops or bring money into the village the entire community becomes liable to malnutrition. This is a disease that has massive social consequences especially in the 3rd world.
Further to your statistics on STDs I heard the other day that in the UK the majority of females with gonorrhea (sp?) are under 25. I can't remember the exact figure but I remember thinking that was a pretty scary statistic.
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quote:
Originally posted by chris
The virus also hides itself away, in a latent form, within our own cells, periodically emerging to cause flurries of viral activity. So you therefore have a pathogen that is adept at the art of disguise, concealment, and immune-sabotage.
Sounds like an Al-Qaeda virus. Aren't we taking the 'terrorism' metaphor a bit far sometimes? Can't we just say it learns how to 'live off the land' and makes do with what's at hand, sometimes reemerging in full previous strenght?
That's how most natural processes take place, I think even the most benign symbiosis was some form of predation or alternatively invasion of sorts.
We either 'ate' our mitochondria and incorporated them for failure to digest them. Lucky thing. Either that or they invaded and settled.
'War', 'sabotage' etc. etc. may be the wrong kind of mindset for something that has more to do with 'trade' and coexistence failures.
I find it quite amusing to see that instead of coming to grips with our inability to see war as the shadow side, or breakdown of 'normal' negotiated trading, which it is, and instead 'export' or project our political onesided view to the medical profession, and biological situations.
Metaphors, metaphors.
[not intended personally chris, we all do it. just had to get it off my chest...'
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How would you propose negotiating with a virus? [:p]
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Same as you propose 'making war' on it I guess, by engaging with it.
We already are. Apparently, like with a lot of other diseases it does NOT catch 100% guaranteed with everyone on this planet. Some people are immune, and we need to know why. There are even indications that people in Europe that are direct descendants of the plague in the 1500's are among them, and they make up quite a percentage of the population, even. Maybe being immune to HIV/AIDS make people either more susceptible or on the other hand, immune to other diseases, as is seen more often with diseases like sicklecell anemia/malaria and typhus/lung emphysema. Those are mutually exclusive diseases, and even when the gen is not expressed, it can protect. That's because the diseases use the same gene switches, and you cannot have it both ways...
So we need to know what its likes and dislikes are, and maybe we can barter with it. Outsmart it with gene logic. This is a changing world. Only species that seem to understand, and appreciate that fact of life remain for the next round, it appears.
The living are the dead on holiday. -- Maurice de Maeterlinck (1862-1949)
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So, the good news is that I can't get typhus!
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Chris, your recap of HIV was awesomely clear and to the point.
I propose that we look at HIV as we would any other enemy. What are his strengths and what are his weaknesses? His strength is his amazing flexibility that makes it nearly impossible to destroy him with drugs or vaccine. His weakness? He is unable to make the jump to infecting a new host through touch or through water droplets, as Influenza is able to do. He requires blood to blood contact of IV drug use or sexual intercourse. Use his weakness. Shut down the VECTOR and you win the battle just as surely as you would by destroying the organism. The organism will be stranded in his surviving hosts, unable to infect any others.
This so far has been the only truly successful strategy against HIV, and in many millions of individuals it is a strategy that has worked well. Either by abstaining from sex or by using condoms, many individuals stay HIV-. The strategy breaks down when your partner cheats on you and infects you with HIV obtained from a third party, obviously- and that has been a huge problem.
A nice feature of this strategy of fighting the VECTOR rather than the organism is that it is cheaper. Billions of dollars are required to keep the HIV+ members of the human race alive for a normal life span. Educating and providing condoms to the HIV- members of Homo Sapiens is in theory cheaper- provided that the education is actually absorbed permanently with no cheating and if testing is available to verify that husband and wife are both HIV- and thereby able to safely have children.
If we remain somehow unable to figure out the way to make a vaccine ( and it has been 20 years so far) then dealing with the VECTOR will remain the only real hope for the human race. Those who adjust behaviors will survive, and those who do not will die, unless they are able to get reliable access to expensive antivirals for the rest of their lives.
chris wiegard
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Recently some news said that some scientists have discovered a way to erradicate de latent form of HIV in the body, and that could eliminate the infection and cure the person with HIV, Is it responsible to talk about a cure? I mean aren't these words a little too rushed? or is it that this way (that's made with an epilepsy medicine) have really shown truly effective results?
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That was very interesting reading the stats on diseases transmitted by unprotected sex (chlamydia) in the UK. It seems like this very real public health threat would be helped by some sort of public health campaign...
Even in Portugal where you might expect some resistance from a widely Catholic population, there is a very public advertising campaign on how to put on a condom - a poster shown on bus shelters, train stations etc.
Now that's a technique your folks never explained...!
Relax, Enjoy it, or what's the point..
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This thread has been an interesting one. I've decided to set up a social bookmark at Siphs to catalog references regarding AIDS treatment. I'd love to get some of you in on the list as you're clearly well read on the issue at hand. If you want to check out the list, it's at this link:
http://www.siphs.com/ate/references/aids_treatment_8.jsp
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mmm, great link. Goes to nothing but a blank page. Shameless self-link perhaps...?
Chris
"I never forget a face, but in your case I'll make an exception"
- Groucho Marx
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quote:
Originally posted by DoctorBeaver
How would you propose negotiating with a virus? [:p]
I had recently heard about a study that seemed to show that HIV was naturally becoming less virulent. If true, then it would imply that the virus and human genome are already negotiating, where the virus is saying 'if you give me a free ride, without too much hassle, then I wont kill you'. SIV seems already to have negotiated just such a deal with our monkey cousins. After all, it is not in the long term interest of a virus to kill its host - it needs its host for reproduction.
http://www.cleveland.com/news/plaindealer/index.ssf?/base/news/1127986229318330.xml&coll=2
quote:
study that staged a microbial version of a sports match suggests what many AIDS researchers have suspected all along: that HIV, which is expected to become the worst pandemic in human history, may actually be growing weaker over time.
Scientists from Cleveland and Antwerp, Belgium, pitted HIV specimens from 1986 to 1989 as AIDS roared onto the scene, against viruses from 2002-2003 in a series of competitions to determine which ones flexed more muscle, biologically speaking. They found that the 1980s specimens were fitter than their newer counterparts 75 percent of the time.
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[:)]
tejaswini
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ur question is justified . but cure for aids come only through miracle. the virus mutates faster than fashion in paris.that's why it is so difficult to find a vaccin. but research is going on to fight aids by increasing the immunity of the already infected patient . so"cure is better than prevention"[:)]
tejaswini
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As I understand it most viruses do tend to become less (rapidly) lethal over time. It makes sense, especially for a delicate virus like aids that needs close contact for transmission, since the longer the infected individuals are able to carry on infecting others, the more others they can infect. So there's an evolutionary pressure at work- the virus the largest re-infection ratio (there's a technical term, but I forget it) is most likely to be successful over time.
Basically, entirely killing the host population is counter-productive if you're a virus.
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quote:
Originally posted by rosy
As I understand it most viruses do tend to become less (rapidly) lethal over time. It makes sense, especially for a delicate virus like aids that needs close contact for transmission, since the longer the infected individuals are able to carry on infecting others, the more others they can infect. So there's an evolutionary pressure at work- the virus the largest re-infection ratio (there's a technical term, but I forget it) is most likely to be successful over time.
Basically, entirely killing the host population is counter-productive if you're a virus.
While I agree with all of the above, I suspect it would be only half the reason for this.
It is not only the fact that they can more easily infect others, but that they are switching from hunting to farming (i.e. they need a human alive, not dead; so by allowing the human to live, it has a guaranteed supply of cells to infect – one dead human = end of fresh cell supply from that human).
Another factor that I have often wondered about – how much is it a case of the virus killing the human, and how much a case of the human committing suicide (not just with regard to AIDS, but any viral disease). I would imagine that individual cells are designed to commit suicide if they become infected, in order to quarantine the infection from the rest of the body; so why not the whole organism being programmed to commit suicide to protect the species? Could not the increased longevity of an infected person also be a case that the organism has given up the attempt at voluntary quarantine? In extreme cases we do know that viruses (particularly retro-viruses) can become an integral part of the species genome, thus clearly the species in such cases had given up the attempt to maintain the integrity of its original genome and allowed this passenger to come aboard. Could AIDS be going the same way?