Can you get HIV twice? Apparently you can. An HIV patient
in Montreal's McGill AIDS Centre has become infected with
two different forms of the virus. A superinfection such
as this was previously thought to be out of the question
� until now.
Conventional wisdom had it that
an infection with a given variant of HIV foreclosed
the possibility of new infections, but doctors were
taken by surprise when one patient's clonal profile
"suddenly took off at a sharp tangent," according to
lead author Dr Mark Wainberg, director of the McGill
AIDS Centre.
"Normally these changes in clonal
profile are slow and predictable, with only minimal
variation over months, but this was completely different,"
he said. Suspicions of an HIV superinfection were rapidly
confirmed when the centre's doctors identified the partner
who had transmitted the second virus to their patient.
Moreover, the second infection,
like the first, was a multidrug-resistant type of the
disease. "It looks like it might have a fitness advantage,"
said Dr Wainberg. "It effectively cleared out and took
over from the old infection in fairly short order."
The patient in question has not
yet developed AIDS and is not taking any antiretroviral
treatments. Unfortunately, a superinfection with a resistant
virus is not a promising sign in terms of prognosis.
"It means that when treatment does begin, it might prove
quite difficult." Dr Wainberg believes that antiretroviral
drugs would normally be protective against superinfection
unless the new viruses were specifically resistant to
the drugs being taken.
The discovery of one patient in
Montreal after so many years of treating HIV patients
does not mean that superinfection is a rarity, says
Dr Wainberg. "It has more to do with the kind of work
we were doing. Other cases have popped up just recently;
Luc Ferrand in Geneva had one, and so did Susan Little
at the University of California in San Diego. If people
looked harder, I'm sure they would find plenty."
The news is published in
a study reported in the August 20 issue of the journal
AIDS, whose principal finding was a confirmation
that very little mutation is observed in existing infections.
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