Understanding the prevalence of transmission of treatment-resistant strains of virus is becoming more important as the HIV epidemic evolves to include a growing number of treated individuals who are healthy and sexually active. Although transmission of virus resistant to all classes of antiretroviral agents has been demonstrated, estimates of the frequency of resistant strains being transmitted to uninfected individuals is unknown. From a therapeutic standpoint, this is very important because complete suppression of HIV replication could be compromised if a newly-infected individual harbors drug-resistant virus.

Wegner and colleagues report seroprevalence of treatment-resistant virus from 114 treatment-naïve adults newly diagnosed among a military population within the last three years. Demographically, men comprise 97% of the group with an age range of 19-45 years (mean of 30), and 46% are Caucasian, while 40% are African American. Using the VircoGEN^TM system, genotype (presence of gene mutations) was assessed from 95 samples, and phenotype (actual sensitivity to virus as measured in a laboratory setting) from 91 samples. Based upon this reporting schema, genotypic abnormalities were further classified as either possibly resistant or or resistant, while the phenotypic profile was subdivided into intermediate resistant or resistant categories. For the most part, the genotypic profile was able to predict accurately the phenotypic pattern exhibited by virus.

Aside from demonstrating that mutant strains were frequently transmitted, these data are striking for the predominance of NNRTI resistance. The authors noted further that several different mutations invoking NNRTI resistance were seen in their analysis.