Now New Methods are Used to Detect HIV Antibodies

by Bidita Debnath on? May 26, 2013 at 10:27 AM AIDS/HIV News Detection of HIV antibodies is used to monitor trials of experimental HIV/AIDS vaccines and diagnose HIV infection.
New, more sensitive detection systems being developed use microspheres to capture HIV antibodies and can measure even small amounts of multiple antibodies at one time. This novel multiplex immunoassay approach is described in an article in BioResearch Open Access, a peer-reviewed open access journal from Mary Ann Liebert, Inc., publishers (http://www.liebertpub.com). The article is available on the BioResearch Open Access website (http://www.liebertpub.com/biores).

The ability to detect very low levels of HIV virus is critical for early detection of HIV infection and to assess the effectiveness of an AIDS vaccine. Rebecca L.R. Powell and coauthors from the International AIDS Vaccine Initiative, Brooklyn, NY, compared the microsphere-based BioPlex? Suspension Array System to conventional ELISA antibody test methods for detecting simian immunodeficiency virus (SIV) in SIV-infected rhesus macaques.

The specificity of the two methods were comparable. The microsphere-based test system successfully detected four key HIV antibodies simultaneously in SIV-infected animals, compared to noninfected control animals. Furthermore, in blood samples that tested negative for one or more HIV antibody using an ELISA test, the microsphere assay was often able to detect the antibody in the sample.

The findings were presented in the article "A Multiplex Microsphere-Based Immunoassay Increases the Sensitivity of SIV-Specific Antibody Detection in Serum Samples and Mucosal Specimens Collected from Rhesus Macaques Infected with SIVmac239." (http://online.liebertpub.com/doi/full/10.1089/biores.2013.0009)

"This new method provides a significant improvement over standard ELISA techniques, allowing increased sensitivity for specific antibody detection?which is highly important for assessing vaccine efficacy," says BioResearch Open Access Editor Jane Taylor, PhD, MRC Centre for Regenerative Medicine, University of Edinburgh, Scotland.

Source-Eurekalert

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For Severe Form Of Rheumatoid Arthritis, Enzyme-Activating Antibodies Revealed As Marker

They have performed a series of lab experiments designed to unravel the workings of a key enzyme widely considered a possible trigger of rheumatoid arthritis.

Reporting in the journal Science Translational Medicine online May 22, the Johns Hopkins team describes how it found the novel antibodies to peptidylarginine deiminase 4, or PAD4, in blood samples from people with aggressive inflammation and connective tissue damage.

Researchers say the presence of so-called PAD3/PAD4 cross-reactive autoantibodies could serve as the basis for the first antibody-specific diagnostic test to distinguish those with severe rheumatoid arthritis from those with less aggressive forms of the disease.

"Identifying early on a subset of patients with severe rheumatoid arthritis could benefit their health, as these patients could start aggressive drug therapy immediately and find the most effective treatment option," says senior study investigator Antony Rosen, M.D. Rosen, director of rheumatology and the Mary Betty Stevens Professor at the Johns Hopkins University School of Medicine, says that a third, or 1 million of the more than 3 million Americans - mostly women - estimated to have rheumatoid arthritis have an aggressive form of the disease.

In the study, the antibodies were present - in 18 percent of 44 fluid samples from one research collection and in 12 percent of another collection of 194 - but only in people with severe cases of rheumatoid arthritis. Past research shows that those with the most aggressive disease are less likely to respond to anti-inflammatory treatments with steroids and other drugs.

An examination of patients'' medical records revealed that 80 percent of patients with the antibody saw their disease worsen over the previous year, while only 53 percent without the antibody showed disease progression. In comparing average scores of disease-damaged joints, researchers found that those with the antibody had an average deterioration in joints and bones by a score of 49. Those without the antibody had an average degradation in their score of 7.5, indicating much milder disease.

In a related finding, the Johns Hopkins team also uncovered how the PAD3/PAD4 cross-reactive auto-antibodies might contribute to more severe, erosive disease in rheumatoid arthritis. The team performed a series of experiments to gauge the antibodies'' effects on PAD4 in response to varying cell levels of calcium, on which PAD enzymes depend.

Lab experiments showed that the antibodies greatly increase PAD4 enzyme function at the low levels of calcium normally present in human cells. Results showed that PAD4 activity was 500 times greater in the presence of antibodies than when they were absent. Tests of the antibody and enzymes'' chemical structures later showed that the antibodies bind to PAD4 in the same region as calcium, suggesting to researchers that the antibodies might be substituting for calcium in activating the enzyme.

According to Rosen, the series of experiments, which took two years to complete, represents the first evidence of an antibody having a direct role in generating the targets of the immune response, or auto-antigens, in rheumatoid arthritis.

"Our results suggest that drugs inhibiting the PAD4 enzyme may have real benefit in patients with severe rheumatoid arthritis and represent an important field of study for investigating new and alternative treatments," says lead study investigator and biologist Erika Darrah, Ph.D.

Darrah says the team next plans long-term monitoring of arthritis sufferers to find out when the antibody first appears in the blood, and when intervention may have maximum impact in preventing or stalling disease progression. The team also plans further experiments to see if the antibody is taking control of the chemical pathways normally used by other cell proteins to control PAD4 sensitivity to calcium.

Funding support for this study was provided by the National Institutes of Health, and corresponding grant number T32-AR048522; the American College of Rheumatology; the Donald B. and Dorothy L. Stabler Foundation; and Sibley Memorial Hospital.

In addition to Rosen and Darrah, other Johns Hopkins researchers involved in this study were Jon Giles, M.D.; Michelle Ols, Ph.D.; and Felipe Andrade, M.D., Ph.D. Additional research assistance was provided by enzymologist Herbert Bull, Ph.D.

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