Drug Resistance Differences Among HIV Types and Subtypes: A Growing Problem

Although HIV-1 subtype B accounts for only 10% of worldwide HIV infections, almost all knowledge regarding antiretroviral (ARV) drug development and viral resistance is based on this subtype. More recently, an increasing body of evidence suggests that distinct HIV genetic variants possess different biological properties, including susceptibility and response to ARVs. In this review, we will summarize recent in vitro and in vivo studies reporting such differences. In general terms, infections with most HIV variants respond well to ARVs, but minor differences in susceptibility, in the emergence and selection of subtype-specific drug resistance mutations and in the acquisition of similar mutations over the period of ARV exposure have been reported. Such differences impact on drugresistance interpretation algorithms, which are mostly based on inference from sequence information. Despite the differences observed, clinical response to ARV therapy among subjects infected with distinct HIV variants is effective, and the dissemination of ARV access in developing countries where non-B subtypes prevail should not be delayed.