Battling Drug-Resistant HIV Strains in Newly Infected Patients
Genetic testing of all patients for reverse-transcriptase inhibitor
resistance showed mutations associated with zidovudine resistance in seven
patients; two patients had mutations associated with resistance to lamivudine
Genetic mutations associated with resistance to protease inhibitors were
detected in three patients, of whom two also had reverse-transcriptase
inhibitor-resistant mutations. Decreased sensitivity to three or four protease
inhibitors was seen in three patients, including one patient who had 12
mutations associated with resistance to multiple reverse-transcriptase
inhibitors and protease inhibitors.
The researchers recommend pretreatment resistance testing in all recently
infected individuals in order to start each patient on the
anti-HIV/antiretroviral treatment most likely to be effective. "Resistance
testing is important, especially in the case of primary infection ... to be
sure to give the best treatment, because the first treatment is the best chance
for the patient," says Yerly.
"I would certainly agree with that," says Carpenter. "You would
like to check and therefore treat with a regimen that is going to knock the
virus levels in [the patient's] blood down to undetectable levels -- that will
make transmission far less likely. If you have a resistant virus, and the
antiviral agents that you give are not effective in lowering the level in the
blood, then the likelihood of [transmitting] resistance, if the patient has any
unsafe behavior, is greater.
"That is what I think most of us would want to do -- in those few cases
where we see patients that early in the disease -- but we usually don't see
them until after that early period, by which time they often have several
different strains of resistant virus," says Carpenter.
Carpenter is not overly optimistic that drug-resistant HIV can be contained.
"We have not been able to do that very well with other [organisms] --
resistant Staphylococcus, for instance," he says. Despite this,
resistance testing may be the only option currently available. "The
alternative to knowing what agents the virus is resistant to," he says,
"is treating ineffectively, and the patient gets sicker and care becomes
much more expensive."