Ancylostoma
Forum Guru
Topics: 42
Posts: 642
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i forgot the exact mechanism. the phenomenon is called genetic drift, small changed in the genome. Genetic shift is genetic reassorment that occurs in segmented viruses , reovirus, orthomyxovirus (flu), bunyavirus, arena virus. and is reposible for pandemics.
Genetic drift is like genetic shif but to a smaller extent.
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| johnnyu041
Forum Junior
Topics: 2
Posts: 48
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okay antigenic shift is when hemagglutinin(HA) and neuroaminidase(NA) on the envelope is radically changed due to exchange of RNA segments between human and animal viruses, this happens around every 20 years and causes pandemics....antigenic drift on the other hand occur every year and are associated with spontaneous mutations which result in only slightly altered HA and NA and is responsible for endemic infections....this is the reason that one years flu vacciine will not work for the next year.
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| Ancylostoma
Forum Guru
Topics: 42
Posts: 642
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Good clarification, I new I was missing something
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| arivero
Forum Junior
Topics: 14
Posts: 50
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Thanx for the reply, but does HIV genetic shift have anything to do with Reverse Transcriptase changing its structure, and thats why the Virus is hard to treat?
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| Ancylostoma
Forum Guru
Topics: 42
Posts: 642
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simply put the changes are not in reverse transcriptase, they are in the structure of the virus, the structure is what we make antibodies 4 that help prevent entry of hiv in the cell. Second hiv effects t helper cells, decreases the expression of mhc complex protiens making it harder for cell mediated immunity to kill the sucker
if there were changes in the enzyme, this could possible effect the abilit of antiretrovirals from working, hence to prevent this resitance they always use two rti and a protease inhibitors. I 'm wrong someone correct me , but i'm prettey sure thats how it works.
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| arivero
Forum Junior
Topics: 14
Posts: 50
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You should be correct, I thought I got that one wrong. I hope it was an experimantal question. :-(
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| me007
Forum Guru
Topics: 72
Posts: 803
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might be this
HIV has additional ability to mutate easily, in large part due to the error rate of the reverse transcriptase enzyme, which introduces a mutation approximately once per 2000 incorporated nucleotides. This high mutation rate leads to the emergence of HIV variants within the infected person's cells that can resist immune attack, are more cytotoxic, can generate syncytia more readily, or can resist drug therapy. Over time, different tissues of the body may harbor differing HIV variants.
(from webpath)
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