Annette Alaeus

Quantification of plasma HIV-1 RNA levels has rapidly become the main tool for monitoring disease progression and treatment. However, some first-generation assays do not accurately quantify all HIV-1 subtypes. This study compares the first-generation and two newer prototype Amplicor HIV-1 Monitor assays (Roche Diagnostic Systems) in terms of their performance in quantifying HIV-1 RNA in stored plasma samples from 101 individuals infected with various genetic subtypes of HIV-1 (28 subtype A, 18 B, 26 C, 20 D, 2 E, 3 G, 2 H, and 2 J). The HIV-1 subtype had previously been determined by direct sequencing of the V3 domain of the env gene. The results from the three assays agreed for subtypes B and C, as well as for most subtype D samples. In contrast, the first-generation assay reported significantly lower plasma HIV-1 RNA levels than did the two newer versions of the assay for most subtype A, E, G, and H samples. There were no differences in mean plasma HIV-1 RNA levels between individuals infected with subtypes A, B, C, and D if the results from the two newer test versions were used, and if an adjustment was made between subtypes for differences in CD4 count. Thus, this study confirms that the first-generation assay does not accurately quantify HIV-1 RNA levels in many individuals infected with subtype A, E, G, and H. These problems appeared to have been greatly reduced in the two new prototype versions.

HIV-1 is characterized by a high degree of genetic variation and can be divided into at least 10 distinct genetic subtypes. The purpose of this study was to investigate whether the rate of disease progression shows subtype-specific differences. The investigation was divided into two parts; one study in which 49 ethnic Africans were compared with 49 ethnic Swedes irrespective of the subtype of the infecting virus, and a second study in which 126 individuals infected with different genetic subtypes (28 with subtype A, 59 with subtype B, 21 with subtype C and 18 with subtype D) were compared. CD4 cell counts, the rate of CD4 cell decline, plasma HIV-1 RNA levels, clinical status and antiviral treatment were prospectively and retrospectively recorded. The HIV-1 subtype had previously been determined by direct sequencing of the V3 domain of the env gene. There were no significant differences in the rate of CD4 cell decline or clinical disease progression between Africans and Swedes over an observation period of 2 years. Similarly, there were no differences in the rate of CD4 cell decline, clinical progression or plasma HIV-1 RNA levels between individuals infected with subtypes A, B, C or D over a mean observation period of 44 months. Neither the genetic subtype of the virus nor the ethnicity of the host appear to be major determinants of disease progression.