HIV Testing Blog

HIV-1 diagnosis in babies born to seropositive mothers is one of the challenges of HIV epidemics in children. A simple, rapid protocol was developed for quantifying HIV-1 DNA in whole blood samples and was used in the ANRS French pediatric cohort in conditions of prevention of mother-to-child transmission. A quantitative HIV-1 DNA protocol (LTR real-time PCR) requiring small blood volumes was developed. First, analytical reproducibility was evaluated on 172 samples. Results obtained on blood cell pellets and Ficoll-Hypaque separated mononuclear cells were compared in 48 adult HIV-1 samples. Second, the protocol was applied to HIV-1 diagnosis in infants in parallel with plasma HIV-RNA quantitation. This prospective study was performed in children born between May 2005 and April 2007 included in the ANRS cohort. The assay showed good reproducibility. The 95% detection cut-off value was 6 copies/PCR, that is, 40 copies/10(6) leukocytes. HIV-DNA levels in whole blood were highly correlated with those obtained after Ficoll-Hypaque separation (r = 0.900, P < 0.0001). A total of 3,002 specimens from 1,135 infants were tested. The specificity of HIV-DNA and HIV-RNA assays was 100%. HIV-1 infection was diagnosed in nine infants before age 60 days. HIV-DNA levels were low, underlining the need for sensitive assays when highly active antiretroviral therapy (HAART) has been given. The performances of this HIV-DNA assay showed that it is adapted to early diagnosis in children. The results were equivalent to those of HIV-RNA assay. HIV-DNA may be used even in masked primary infection in newborns whose mothers have received HAART. J. Med. Virol. 81:217-223, 2009. (c) 2008 Wiley-Liss, Inc.

A fourth generation HIV testing assay detected almost two-thirds of individuals with acute HIV infection, investigators report in an article published in the online edition of the Journal of Acquired Immune Deficiency Syndromes. The researchers believe that their results show the ARCHITECT HIV Ag/AB Combo Assay to have significant advantages, including the time needed to obtain a result compared to the current pooled HIV RNA testing strategy used to diagnose acute HIV infection. Such assays are already routinely used in the United Kingdom.

Diagnosis of acute HIV infection relies on detection of HIV virus using viral load tests, or p24 antigen. Pooled HIV viral load testing has been shown to be an effective means of diagnosing acute infections. However, it is slow, it typically taking between seven and 21 days to obtain the results, cumbersome, and labourious. It is therefore not a realistic technology for resource-limited settings, nor for addressing the problem of ongoing transmission from people during acute infection.
The ARCHITECT Combo assay was positive for 13 of the 21 acute samples. The median viral load of individuals testing positive with this technology was significantly higher than that of individuals testing negative (662,ooo copies/ml vs. 3576 copies/ml).

“The failure to diagnose acute HIV infection represents an important public health problem”, note the investigators, “persons with primary infection may be up to 10 times more likely to transmit HIV per sexual act than are individuals with established infections”.

For the complete article, please refer to http://www.aidsmap.com/en/news/D9111996-68D9-4F3D-A499-C9559819B045.asp.