The results of a recent AIDS vaccine trial, RV144, have given researchers a clue about how to successfully inoculate against HIV. The trial took place in Thailand with over 16,000 participants, and concluded that the vaccine lowered the rate of HIV infection by 31% among those vaccinated compared to those who were not.
The trial hinted that antibodies found in mucosal sites may be vital for successful protection against HIV, sparking the attention of researchers. This marks the first time that a vaccine has had any success in preventing HIV infection.
A study published in BioResearch Open Access in June has capitalized on the opportunity offered by the RV114 trial. The authors studied rhesus macaques and SIV (simian immunodeficiency virus) in place of humans, and attempted to improve upon current methods for detecting antibodies.
This research compared the traditional antibody assay, ELISA (enzyme-linked immunosorbent assay) with a newly developed, highly sensitive multiplex assay based on microspheres. The microspheres are used with the Luminex xMAP® Technology, the leading multiplex assay provider.
A 4-plex bead array assay was developed to detect four different antibodies specific to SIVmac239 that may be useful as biomarkers for immunization—Envelope gp130 (Env), Gag p55 (Gag), Pol, and Nef. Multiplex technologies allow for the simultaneous detection of multiple components—in this case, the four antibodies.
The multiplex technology was tested by conducting assays on rhesus macaques chronically infected with SIV, whose ELISA tests of serum and mucus antibodies came up negative. The multiplex test used serum and rectal swabs as assay samples.
The bead-based multiplex assay was found to be more effective than ELISA. Here is a breakdown of the results. The assay:
- Detected all four SIV-specific antibodies in the infected animals compared to the controls.
- Detected Gag in serum in 79% of the cases in which ELISA failed to find it.
- Detected Gag in rectal swabs in 48% of failed ELISA cases.
- Detected Env in serum in 70% of failed ELISA cases.
- Detected Env in rectal swabs in 71% of failed ELISA cases.
- Is comparable to ELISA in overall assay specificity (94%-100% specificity).
The authors conclude that the 4-way multiplex assay is vastly superior to the ELISA method for detecting specific antibodies. It is faster and more efficient, able to test for multiple substances and find them when ELISA cannot. They suggest that this technique will be useful for discovering the association between the protection given by a vaccine and the antibody response it generates.