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不单单是李桐曾医生说的那些病情严重的,也有身体健康的啊。
HIV Infection in HIV Antibody Negative Individuals
HIV infection in HIV antibody negative individuals
There is another post on this topic: HIV infection in individuals who are HIV antibody negative:
The possibility that there are individuals who are infected with HIV but who are negative on the test for HIV antibodies has always been theoretically possible. Considerable evidence has accumulated for many years that there are indeed such individuals. Despite the importance of this phenomenon, it receives relatively little comment.
It sometimes seemed to me ever since I first tried to discuss this possibility in the mid 1980s that there was a wilful discouragement of any discussion of this topic.
In 1989 David Imagawa reported that that 31 of 133 HIV antibody negative men showed the presence of HIV.
In 27 of them this persisted for 36 months despite remaining seronegative [1]. This resulted in a vigorous response culminating in what almost looked like a retraction by the authors. At that time many unsuccessful attempts to replicate these results were reported, and the findings of David Imagawa were generally presented as due to technical errors, such as incorrect specimen labelling. In view of many subsequent findings, the likelihood is that David Imagawa and his colleagues were correct. The furious response to Imagawa’s paper is an indication of how non rational considerations can influence the progress of science. This is of course nothing new.
Curiously in a recent book, Imagawa’s findings are included in a list of what are stated to be errors and controversies in the HIV/AIDS epidemic that impeded scientific progress [2]
What in fact impeded progress was a rigid adherence to what was only a hypothetical, not an empirical model of the course of HIV infection.
David Imagawa died shortly after this controversy, and sadly did not live to see that his initial conclusions were absolutely consistent with what has been learned of the complexity and diversity of individual responses to HIV infection.
I certainly experienced considerable resistance and disbelief when I raised the possibility of silent HIV infections. In the late 1980s I took part in a NPR program, and was quite abruptly dismissed by another scientist (I have forgotten who) when I raised the absolutely reasonable theoretical possibility of persistent latent infections in antibody negative individuals.
Apart from very few exceptions there was an almost complete lack of interest in HIV seronegative, but infected individuals, by science writers; there was no shortage of community commentators who also seemed to be oblivious or uncaring of this phenomenon.
To be sure there were occasional reports of seronegative but infected individuals. Gus Cairns, a UK journalist wrote about this in the UK magazine, Positive nation. I wrote something about this as a result of an interview with him in 2000, which he published. I have scanned the article. I was unable to make a perfect copy, but a legible version can be seen by clicking HERE.
In the US reports confirming the existence of seronegative infected people continued to receive very little comment; what little there was was generally quite hostile..
Today this issue was again brought to my attention by an article I saw reporting the presence of HIV proteins and HIV RNA in cervical biopsies from women who were persistently HIV seronegative , at least for the duration of the study which was one year [3]. They did not have antibodies to HIV despite being infected; of course it is possible that they are in an unusually long “window period” and will eventually seroconvert. If we use “window period” in this sense then we can speak of a distribution of window periods of different lengths, including an indefinite one.
I expect that, as is usual this report will provoke little or absolutely no interest.
But it is enormously interesting; (just one of many questions: can these women infect their male partners?)
Seeing this article is the reason why I decided to make this issue the subject of this post.
It was no great surprise when evidence appeared that there were some individuals who were HIV infected but remained negative on the HIV antibody test. It must be said that there were probably more papers in the early years in which silent HIV infections in HIV antibody negative individuals was not observed.
In another approach, reports started to appear that HIV antibody negative individuals had T lymphocyte responses to HIV which means that they were exposed to the virus, not necessarily that they were infected – although that is quite a real possibility. Some early papers, before 2000, including those showing T cell responses can be seen by clicking HERE
. There was quite an extensive literature at that time, but most, as mentioned reported that there was no such thing as a silent antibody negative infection, apart from the short window period following infection.
Why has the possibility of prolonged latency always been theoretically possible?
As part of its life cycle HIV is turned into DNA and is then incorporated into the host genome. In infected cells it effectively becomes part of our genetic material. Once inserted into human DNA, it must be activated to start the process of making new virus particles. Cellular signals that start the process of activating HIV DNA include cytokines, which are messenger molecules produced and released by cells, which can then act on other cells to evoke a variety of responses. Amongst these HIV activating cytokines are those that are called proinflammatory cytokines. These appear during the course of many different infections. Once HIV DNA is activated, and at least some of its proteins made, these then mediate further activation.
There are some other factors that can activate HIV DNA.
Alloantigens are antigens expressed on foreign cells. When these antigens are in contact with a cell containing integrated HIV DNA, activation occurs; HIV DNA is transcribed and new viral particles made. In earlier days HIV was isolated from infected lymphocytes in this way. Latently infected lymphocytes were induced to produce HIV by culturing them together with lymphocytes from an uninfected donor.
It is the nature of HIV infection that it is frequently acquired in situations which involve exposure to foreign cells (to alloantigens). This may be exposure to semen in sexual transmission, or blood cells in the case of infection by shared needles, or by blood transfusion.
Herpes viruses have the ability to activate HIV if a cell is infected with both viruses. I suppose this must happen but I imagine doubly infected cells may not be found too frequently. Of course active herpetic infections in non HIV infected cells may be associated with the production of pro inflammatory cytokines, which circulate and can activate HIV DNA in a cell at a distance.
There is absolutely no reason not to expect that in some circumstances incorporation of HIV DNA into human DNA will result in a state of stable integration. This means that HIV DNA remains in the genome, it is not activated, and no virus is produced. Since antibodies are made as a response to viral proteins, and as none are made, the HIV antibody test will be negative.
So it was no surprise when such individuals were again reported in 1999 [4]. These individuals remained in good health and were reported to be antibody negative as long as they were observed [5].
We cannot know if these individuals may seroconvert (or maybe already have), but what is established is that stable integration of HIV DNA without seroconversion can occur. In such individuals limited expression of HIV can occur, at least sufficient to induce, if not antibodies, a cellular immune response.
The presence of such cellular immune responses in HIV antibody negative individuals is further evidence consistent with HIV DNA persistence, but in itself does not indicate this.
Demonstration of cell mediated immunity to HIV:
Apart from the identification of antibodies, specific immunity to HIV can also be detected by a much more elaborate test that measures cellular immunity rather than immunity determined by detecting specific anti HIV antibodies. In this case what is measured is the ability of lymphocytes to recognize HIV. They will do so only if they have been exposed to the virus, which would obviously be the case if they were taken from an infected individual.
The detection of such lymphocyte responses in the mid 1990s was one of the first indications that there may be infected people who don’t make antibodies. Other interpretations are that the infection was overcome, or that that the individual was infected with defective virus.
Gene Shearer was I believe the first to report this phenomenon. HIV antibody negative sexual partners of HIV positive people, as well as individuals who had occupational contact with HIV were among those showing these responses.
It is unknown how widespread this phenomenon of silent HIV infection is. It may be exceedingly rare. It is also unknown if this condition of stable integration is really just a prolonged “window” period that always follows all HIV infections.
But it is entirely possible that there are individuals in whom the ability to control HIV is such that they will remain healthy and HIV negative.
A number of different outcomes of HIV infection are possible:
Some of the factors that influence this:
Host genetic factors.
Size of the inoculum – the amount of infecting virus.
Route of infection
The particular virus strain.
HIV Infection in HIV Antibody Negative Individuals
AIDS, antibody negative, EBV, HIV infected, HIV seronegative, seroconversion
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