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Re: your response to person from India
Apr 13, 2004

Dr. Sherer,

I noticed that you advised someone from India to have an ELISA test 6 months after exposure, since very occasionally, some may take 6 months to seroconvert. That makes a lot of sense, since I've read of such cases and I do not know why the CDC has moved towards a 3 month window for a definitive result (maybe newer generation ELISA's generally detect antibodies sooner?).

My questions, to which I can nowhere find a direct answer and would appreciate your advice are:

a. Do the FDA approved ELISA tests, with equal sensitivity, detect antibodies to "all" subtypes of HIV-1, group M and do the HIV-2 ELISA's detect antibodies to all groups and types of HIV-2? As HIV keeps evolving genetically and subtypes beyond M group K will eventually emerge (just as J was the last subtype a couple of years ago and now we are at"K"), will ELISA's be able to detect antibodies to these newer M subtypes?...namely, are all HIV-1 M group antibodies essentially the same for purposes of ELISA detection?

b. Does the bDNA or Roche 1.5 RNA test detect viral load for all HIV-1 subtypes?

c. What is the longest known time that anyone took to seroconvert?

Many thanks.

Response from Dr. Sherer

Thank you for yout thoughtful question.

The current generation of HIV-1 Elisas do detect antibodies to all sub-types of group M, and the HIV-2 ELISAs detect antibodies to HIV-2 subtypes as well. Yes, for the purposes of ELISA testing, all M group antibodies are essentially the same.

Yes, both the Roche 1.5 and the bDNA detect plasma HIV RNA for all HIV-1 sub-types.

Though there have been anecdotes of individuals who seroconverted months, or even a year or more after exposure, the question cannot be answered scientifically. It is likely that some of these patients had blunted immune responses (for whatever reason), or an excessive immune reaction with an excessively high antibody titer which impeded the assay (requiring dilution in order to detect the positive result), or other laboratory errors.

CDC reduced the time of confirmation out of recognition that the vast majority of patients seroconvert within 12 weeks, and in deference to the increasingly sensitive ELISA assays.

Desperately Seeking Undetectable...

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