Viewing 25 reply threads
  • Author
    Posts
    • #14010
      bioshare
      Participant

      Hi,

      All the knowledge I had about viruses is that they cannot live without host.But what exactly an inactive virus ( either by drying for sufficiently long time or by chemicals) means ? Does it mean that it is permanently destroyed for future and cannot be made active even by supplying again the lost nutrients or it means a sort of dormancy? When people say "inactive" , can it be taken as permanent destruction without being any danger in near future? I am asking for any virus or hiv in particular.Replies are appreciated.

      Thanks

      Bioshare

    • #101996
      biohazard
      Participant

      Viruses do not really "live" at all – when they are outside the host cell, they are not doing anything except drifting around and waiting to meet a suitable target cell to infect. So, viruses do not need a host to live, but they need a host to make copties of themselves.

      The term "inactive" or "inactivated" virus typically means the virus has become or been made permanently inactive. This can happen in various ways, but normally it means that some parts of the virus get destroyed by chemicals, physical factors or biological mechanisms. It requires permanent changes to the proteins, lipid envelope or the nucleic acids of the virus, thus rendering the viral particle inactive in terms of the ability to infect its target cells or to replicate inside them.

      Typical inactivating agents (such as detergents) denature viral proteins, dissolve the lipid envelope or break down nucleic acids. Heat and light (especially UV light) can cause some of these events to happen as well. Many organisms also have protein and nucleic acid degrading enzymes within their cells that are used to splice the viral particles into pieces before they infect the cells.

      Genetically engineered viruses can be inactive in such a way that they cannot replicate in the host cell, but they can enter the cells and deliver genetic material into them – these can be used as gene delivery vectors.

      HIV is pretty typical as a virus: it is quite fragile and gets easily destroyed (inactivated) by many common environmental factors, as well as by the common detergents and similar chemical substances. It stays alive in body fluids and gets quickly inactivated outside the body.

      Some (mostly environmental) viruses are more durable and can stay alive in moist environments for longer periods of time; there are viruses in seas and fresh water, as well as in the soil, but even there they require the presence of their host organisms and would disappear quite soon if they cannot find any hosts.

      Viruses without lipid membrane are more resistant to some chemicals whose primary way of action is dissolving lipids; DNA-containing viruses are generally more durable than RNA viruses.

    • #102033
      bioshare
      Participant

      Thanks "biohazard" for detailed explanation but I am still not clear. Are they get permanently destroyed or there is still possibility after their inactivation.Also if only drying can cause complete inactivation.

    • #102039
      biohazard
      Participant

      By definition, "inactive" viruses are permanently destroyed.

      However, in theory you could have various viral particles which themselves would all be inactive (unable to cause disease), but could spontaneously form an infectious virion. But if you have, for example, a product that contains inactivated viruses (like some vaccines do), then they must be made inactive in such a way that they cannot form infectious particles anymore – they are permanently "dead".

    • #102040
      bioshare
      Participant

      When you say , viral particles are inactive (unable to cause disease), then I guess you are talking of inactivated virus outside host and thus unable to infect but my question is that if these inactive viral particles are again supplied with their requirements (say , they are injected into bloodstream of their host, which was their ideal environment) , can they be infectious to this new host ?

      If the answer to this is No , then my second question is : if drying of the fluid containing viral particles is only sufficient to cause such irreversible inactivation ?

    • #102045
      biohazard
      Participant
      quote bioshare:

      When you say , viral particles are inactive (unable to cause disease), then I guess you are talking of inactivated virus outside host and thus unable to infect but my question is that if these inactive viral particles are again supplied with their requirements (say , they are injected into bloodstream of their host, which was their ideal environment) , can they be infectious to this new host ?

      If the answer to this is No , then my second question is : if drying of the fluid containing viral particles is only sufficient to cause such irreversible inactivation ?

      The term "inactive" applies to viruses both inside and outside the host. Basically, what happens in such inactivation event is permanent cross-linking of viral proteins, dissolution of the lipid membrane and/or splicing of the nucleic acids. Artificially, some of these events can be countered – for example a new lipid envelope can be given to an intact viral protein capsule or an undamaged vrial genome can be repacked into a new protein capsule, but these require sophisticated laboratory environments. If you inject inactivated viruses into a host, the viruses cannot cause infection – if they can, they were not inactive.

      For majority of human viruses simple drying is enough to permanently inactivate the viruses in such a way that they do not cause disease even if re-injected to the host later. Even viruses that spread outside the host (like flu viruses by aerosoles) die quite often if exposed to dry air. In moist surroundings and protected from light many of them last longer. For example, many enteroviruses can stay alive in the soil and water for longer periods of time.

    • #102049
      Julie5
      Participant

      So, if inactive means, effectively, ‘dead’ what is the term that is used for when a virus is not in a host, just hanging out looking to mug one? Is it ‘dormant’?

      Also, what does the term ‘attenuated’ mean in terms of vaccines? Does it mean inactive (dead) or simply a less virulent strain in some way?

      Many thanks!

    • #102060
      bioshare
      Participant

      Yes ,Julie, I think then the correct term should be "dormant". But I await reply from other experts on the area.

      Would like "biohazard" to confirm.

      Thanks,

    • #102093
      biohazard
      Participant
      quote Julie5:

      So, if inactive means, effectively, ‘dead’ what is the term that is used for when a virus is not in a host, just hanging out looking to mug one? Is it ‘dormant’?

      Also, what does the term ‘attenuated’ mean in terms of vaccines? Does it mean inactive (dead) or simply a less virulent strain in some way?

      Many thanks!

      ‘Dormant’ is quite a good word to describe viruses outside the host (or more precicely, the host cell). However, that would mean that all viral particles are "dormant" except when they bind to their target receptor on the cell surface and inject their genome and possible enzymes inside the cell. In my opinion you could just as well call any non-inactive viruses ‘active’ viruses, because they are active so that they can recognize the target cell and infect it.

      Maybe think viruses as biological bombs: a bomb can be disarmed (= inactivated) and a disarmed bomb will not explode upon finding its taget. An intact bomb is ‘active’, even though there is nothing actively happening inside the bomb – there is activation only briefly when it hits the target. The same goes with viruses: nothing happens, except when it hits the target.

      Now, an attenuated virus is a virus that has been manipulated in a way that some key element(s) of its virulence have been removed. You could think an attenuated virus as a practice bomb or munition: it has an intact casing (=protein capsule) and fuse (=proteins that recognize the target cell) but it lacks the most or all of the explosive material (=parts of the genome required for infection, or some enzymes that help the virus to be copied inside the target cell). So, the practice bomb makes a loud bang but no harm is done, and the attenuated virus may sometimes infect the cells around its injection site, but is unable to spread the infection. Or more often, it simply cannot enter any cells, because its ‘targeting system’ has been altered as well.

      In practice, attenuated viruses are usually mutated in another host organisms so much that they cause the original, protective immune response in human, but cannot spread in humans because they have mutated to use that other host organism (their genome and proteins made by the genome have been altered from the original ones).

      Did my examples make any sense to you? 🙂

    • #102101
      Julie5
      Participant

      Yes indeed – many thanks!

    • #102113
      bioshare
      Participant

      So , will it be perfectly correct to say that :

      A virus in host – Active or alive
      A virus outside host ,in stage capable of transmitting infection – dormant
      A virus outside host , in stage of never transmitting infection – inactivated(or destroyed completely)

      Thanks,

      Bioshare

    • #102114
      biohazard
      Participant

      I think those are all correct, but as far as I know the term ‘dormant’ is not commonly used. This is mostly because there is no really a need to distinquish active and dormant viruses – after all, even a dormant virus is ‘active’ in such a way that it is always ready to infect a cell if it find suitable one. And even an ‘active’ virus is not doing much: it simply gets triggered upon binding on its target receptor, automatically injecting its contents to the target cell and after that the host does the work (although some viral enzymes may take part in the processes, but they are not inside the virus any more).

      In my opinion, you should be just fine with the terms ‘active’ and ‘inactive’ (or, ‘live’ and ‘dead’, but those are not quite as good as viruses are not really ‘alive’ as we usually define it). When the virus gets inside the host cell, it actually gets dismantled there: it unloads its genome and the capsule proteins are discarded. If the virus contains its own enzymes, those are also transported to the cytoplasm. Actually, you cannot really say the infecting virus is ‘active’ when its inside the host, because it is no more! The new viruses produced by its genome, in turn, are active, get ejected from the host cell (often killing it) and then start a new cycle of host-searching.

      So, also here you could perhaps use the ‘biological bomb’ analoque: when the virus infects the cell, it ‘detonates’ – that is, breaks down into pieces, which then force the host cell to manufacture more viral pieces and assemble them as brand new viral particles, ‘bombs’ ready to infect new cells.

      Perhaps the most precise terms would be ‘intact’ and ‘broken’ (or something similar) – an intact virus is a virus that is in one piece, ready to infect and briefly undergoes activation upon binding its target before it is dismantled. A broken virus, in turn, is a virus that has lost the function of one or more essential parts and cannot cause infection. Maybe add a third term ‘attenuated’, which means a virus that is intact, but in wrong environment to work properly.

    • #102140
      biohazard
      Participant

      Just a minor addition/correction: some viruses enter their target cell as a whole virion (=intact viral particle) after the receptor binding, and only inside the cell release their contents. But I don’t think this really changes anything I said above, just a minor tweak to the chain of events in the viral infection 🙂

    • #102162
      bioshare
      Participant

      Thanks a lot for all that information. I am pretty clear now on the topic.

      Bioshare

    • #102321
      bioshare
      Participant

      Hi again,

      Although I got a pretty clear explanation for my previous posting, but I still need a reassurance about some points( talking of HIV virus) mentioned below as some people made me confused on the topic .Please reply by answering correspondinly .

      1. Does HIV virus dies/inactivates if sufficiently dried (without any other method of destroying) and is there any possibility It can get reactivated it in future? E.g if I had HIV positive blood (1 or 2 drops) on a piece of cloth , which was dried sufficiently as per its concentration(say 20 days or more), after which I use this portion of cloth to cover someone’s bleeding wound, will he/she get infected.i.e dried HIV injected again to bloodstream.

      2. Does common household detergents are sufficient to destroy HIV permanently or they just wash/wipe HIV .Do they actually kill/permanently inactivates it ? When people answer that common question of washing HIV stained clothes,they say detergents/soaps kill HIV but usually they are considering the fact that clothes are something which normally donot come in contact with one’s bloodstream, but I am asking from the scenerio where these clothes are likely to contact person’s bloodtstream directly,Will it be safe to use detergents in this situation? If No then whats the solutio for this ?

      Sorry for a lengthy posting but I want to clear the concepts.

      Thanks,

      Bioshare

    • #102322
      canalon
      Participant

      1- It depends. All HIV will probably be inactvated after 20 days but it will depends on many things like for example temperature, light exposure and number of viruses in the blood. Very unlikely, but anyway covering someone’s bleeding wound with a dirty piece of fabric is probably not a good thing anyway.

      2- It depends, again. Once again of the amount of blood in the stain, but also of the detergent. Many laundry detergent contains some bleaching agents and will probably severely damage the viruses. But even if they do not, the simple fact that you remove the stain with water will probably dilute the amount of virus to negligible quantities. So clothes that have been washed should be perfectly safe. And if they went through the dryer or air dried in the sun, then I cannot have any doubt.

    • #102327
      biohazard
      Participant

      Canalon is right I think: it depends. I’ll add something little to his answers.

      1) After drying, 90 to 99% of the viruses die within hours accroding to CDC. In studies where 100 000 times concentrated amounts of the virus were used (when compared to normal serum levels), HIV could be detected with cell culture methods up to 3 days. This means that with the most sensitive methods they could find some active viruses after 3 days from greatly concentrated samples. With all probability a normal blood-stained cloth or fabric should be non-infectious much sooner than this when dried. If exposed to UV light or heat, the times are much shorter.

      In any case, a couple of drops of dried blood should be completely safe after 20 days.

      2) Detergents, alcohol, UV light and heat are very effective against HIV. I do not know the exact composition of "common houshold detergents" in your area, so I cannot say for sure how effectively they kill the virus, but the chances are they do it well. In hospitals they consider blood-stained linen to be HIV free after 25 mins of machine wash at 70 C (~160 F) with detergents – so, pretty much the standard washing procedure for white wash should suffice. Actually any normal machine wash program with detergents should be enough to completely remove the chance of infection, but for this I do not have "official" information.

      In general, HIV is a very sensitive virus because of its lipid coat (good target for detergents) and ssRNA genome (good target for everything).

      Hope these helped.

    • #102357
      bioshare
      Participant

      Response to canalon :

      You said , it will be dilluted when washing with water, but as HIV is held bonded to and within the dried blood molecules strongly attached to cloth, will dillution work to MOVE and affect the virus to make it dilluted?

      Bioshare

    • #102358
      bioshare
      Participant

      Response to Biohazard :

      1.

      > Many facts given by CDC are different from what others say. I am not arguing but I came across so many postings and answers on internet all giving diferent concepts from CDC . e.g see 162 page , 2nd last paragraph on right hand side of this book " Prescription for nutritional healing" which says HIV can stay for many days and that also in inactive state and then becomes infectious again ( also that its not as fragile as normally people think).

      url: id=2s_q2y_J3rwC&printsec=frontcover&dq=nutritional++healing&source=bl&ots=cR70qPHewX&sig=AP4pIavNQ1RWEJD2gEYOhrchS8M&hl=en&ei=IGPlTJfOCYGfcefq6eQK&sa=X&oi=book_result&ct=result&resnum=1&ved=0CBwQ6AEwAA#v=onepage&q&f=false

      > Also see this site which says some different things about HIV than we normally know ( under the section "Nature of HIV")
      url : http://www.invitation.to/dance/hiv.htm

      2. As you said for hospitals, do they use normal detergent OR with bleach ? Does detergent without bleach would be sufficient?

      Bioshare

    • #102359
      canalon
      Participant

      The point of washing is to remove dilute dirt. Normal wash will break most of the crust and expose most of the virion. Soap and large volumes of water will dilute a lot. so no problem.

      to the upper post
      1. your first link does not work. And I wish the second did not either. Trust the CDC not the conspiracy theorist loons. I will not even try to describe how wrong they are (even when it comes to web design, first, my head hurt after only 30s of trying to read that).
      2. Probably the second, but as biohazard and me told you it would probably not matter since HIV is a fragile virus.

    • #102367
      bioshare
      Participant

      Ok, I believe you, but I wish you see the first link, its a good book and don’t seem like a conspiracy theroist.It didn’t work because it was not pasted completely. Here it is:

      just search for "prescription for nutritional healing" on google (page -162, right hand side , 2nd last paragraph)

      or

      http://books.google.co.in/books?id=2s_q … &q&f=false

      Thanks for sweet responses

      Bioshare

    • #102370
      canalon
      Participant

      Sadly, for some reason, Google decided to block page 160-162 from me.
      But you are right, no conspiracy theory in here. Just a repertoire of all the woo and stupid of alternative medicine that never proved its value beyond placebo at best, and sometimes actively hurt the convert. A great read if you have money and possibly health to waste.
      Statistically there is no way to differentiate the potential healing value of anything in this book from anything that would have been randomly typed by a monkey on a computer. This might be popular, but so is superstition and I would not recommend trusting at all.
      The CDC advices are backed by scientist and understanding of what HIV is and does. This is backed by ignorance and superstition. Trust what you want, I know what I would do.

    • #105906
      Falko
      Participant

      No doubt, outside of a living cell, a virus is an inactive particle, but within an appropriate host cell it becomes active. Some animal viruses, for instance, produce latent infections, in which the virus persists in a quiet state, becoming periodically active in acute episodes, as in the case of the herpes simplex virus.

    • #110711
      amirasung
      Participant

      i got a question…why some viruses can cause disease and some don’t??

    • #110712
      biohazard
      Participant

      All viruses can cause a "disease" in some way. They are parasites and thus by definition harmful to their hosts in some way. However, in order to cause a human disease the virus must be able to bind its target molecule on a human cell, enter the cell and produce copies of itself. Finally, it must be able to escape the cell and infect others. If any one of those steps fails, there will be no disease. Failure can be the result of wrong specificity (the virus infects completely different cell types or species), immune defense, viral inactivation due to other external sources and so on.

      Also, many human viruses are so specialized to infect humans that they cause mild and subclinical infections that normally go unnoticed – there is no real use for most viruses to cause a wide-spread immune activation, and/or a fulminant disease that kills their host.

      Actually many of the most dangerous viral diseases are caused by viruses that do not normally infect humans, but by chance happen to do so. The wildly activating human immune response is then often the biggest culprit for the severe symptoms, the virus itself not so much.

    • #110713
      JorgeLobo
      Participant

      An infective viral particle population without a coincident host or cell for replication is not per se "dormant." Viral dormancy (or latency) is more commonly used to describe the presence of viral infectivity in a host without causng an obvious disease. Example would be herpes zoster remaining in he host in absence of apparent diease after chickenpox establishing shnigles decades later. Folks have also referred to initial HIV infection of lymphocytes by such terms.

      I’m not aware of a term of art for an infective virus in absence of a host. ATCC sells for example VR-96 influenza "virus" frozen.

Viewing 25 reply threads
  • You must be logged in to reply to this topic.