Viral Load Assays Under Development

Real-time PCR methods for the determination of HIV-1 viral load uses light cycler instrumentation, and the procedure has increased speed in detection over conventional PCR methods because of the removal of manipulations required for the detection of the PCR amplicon and the incorporation of rapid amplification coupled to fluorescence detection. However, the length of time taken to extract HIV-1 RNA from biological fluids is a hindrance. A recent method which uses lysates may have resolved this difficulty.[11] A further adaptation of realtime diagnosis are tests that are able to detect low copies of HIV-1 nucleic acid[12] as low-level replication of HIV-1 below the detection of current viral load assays may have some clinical importance. The HIV-1 Taqman 5' nuclease PCR is also under development and may have application to the large throughput applications such as the screening of plasma from blood donors.[13] Use of an internal control in each reaction is essential to monitor sensitivity. The optimization of new quantitative assays should take into consideration the diversity of HIV-1 and where possible be able to detect outlier strains and HIV-2.

Other screening assays currently in use in the molecular diagnosis of HIV-1 include the Roche Ampli-cor HIV-1 test which is a qualitative assay that utilizes PCR and nucleic acid hybridization for the detection of HIV DNA from whole blood. The assay was optimized for clade B viruses but there are additional primers which facilitate the detection of non-clade B viruses and has application for the detection of HIV in recently infected individuals prior to the production of antibodies. The

Table 1 Drugs available for use in combination antiretroviral therapy

Nucleoside analogues Nonnucleoside analogues

Nucleotide inhibitors

Protease inhibitors

Fusion inhibitors







Nevirapine Delavudine Efavirenz










Enfuvirtide method may also be adapted to detect HIV DNA in patients where antibody tests may be ineffective, such as infants born to HIV seropositive mothers.

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