merrill@park.bu.edu (04/26/91)
A comment and a question. First, RE: the recent discussion of "How long does it take for an HIV positive individual to seroconvert after exposure" and the related discussion of the USC study. What the USC researchers did was study the serostatus of men who were known to be infected with the virus (by amplification analysis for viral DNA.) The researchers found that their subjects could be HIV-positve (by the more sensitive test) for many years without becoming HIV-positive on an ELISA. As several posters have pointed out, this does not show that the particular "infective event" that caused the eventual progression to antibody positivity happened many years before the later seroconversion, but it should certainly be seen that there is that possibility. Moreover, the USC data *do* clearly show that individuals can be carrying the virus for many years, and, quite possibly, transmitting it, without testing positive on an antibody-based test. In fact, the lack of control for sexual practices in the USC study shows that the time from infection to seroconversion is *longer* than the study's estimate, not shorter. If their patients had been practicing safe sex during the interim, they would certainly not have seroconverted any earlier than they did. Thus, they would have seroconverted (if, in fact, they ever seroconverted) after a longer period of seronegativity, and, therefore, the average time between contracting the virus and seroconverting is, in fact, longer than the USC study shows, not shorter. The fine point of this analysis is the question of whether the men who were virus-positive but antibody-negative would *ever* have seroconverted without a later exposure. We simply do not know---and, in my opnion, no responsible medical or quasi-medical department should give out otherwise. Certainly, there is the possibility that the infected individuals might have remain "totally asymptomatic" forever, but given the evidence that some cofactor is necessary to trigger progression of the disease, and the accumulating evidence that many different cofactors will serve, I think it poor practice to ignore the very real possibility that late seroconversion might happen. It is important to recognize at least one consequence of this analysis. If you were exposed to HIV 2 years ago, have been safe ever since, and have not yet seroconverted, (a) this fact does not mean you have not contracted the virus, and (b) it does not mean that you will never seroconvert. This latter is rendered more relevant by all the data about a wide variety of cofactors: it could be that the trigger which will eventually set a progression to seropositivity might well be years after the initial infection with the virus. A question along the same lines. I seem to remember reading something like "T4 cell counts in HIV positive individuals tend to be relatively constant, but to be punctuated by sudden decreases." Am I hallucinating this remark? Or is this a "fact"? Can someone give me a reference in the literature? Thank you. -- John Merrill / merrill@bucasb.bu.edu