Comparison of an amplified enzyme-linked immunosorbent assay with procedures based on molecular biology for assessing human immunodeficiency virus type 1 viral load

Detection of Snake Venom in Post-Antivenom Samples by Dissociation Treatment Followed by Enzyme Immunoassay

Venom detection is crucial for confirmation of envenomation and snake type in snake-bite patients. Enzyme immunoassay (EIA) is used to detect venom, but antivenom in samples prevents venom detection. We aimed to detect snake venom in post-antivenom samples after dissociating venom-antivenom complexes with glycine-HCl (pH 2.2) and heating for 30 min at 950 °C. Serum samples underwent dissociation treatment and then Russell’s viper venom or Australian elapid venom measured by EIA. In confirmed Russell’s viper bites with venom detected pre-antivenom (positive controls), no venom was detected in untreated post-antivenom samples, but was after dissociation treatment. In 104 non-envenomed patients (negative controls), no venom was detected after dissociation treatment. In suspected Russell’s viper bites, ten patients with no pre-antivenom samples had venom detected in post-antivenom samples after dissociation treatment. In 20 patients with no venom detected pre-antivenom, 13 had venom detected post-antivenom after dissociation treatment. In another 85 suspected Russell’s viper bites with no venom detected pre-antivenom, 50 had venom detected after dissociation treatment. Dissociation treatment was also successful for Australian snake envenomation including taipan, mulga, tiger snake and brown snake. Snake venom can be detected by EIA in post-antivenom samples after dissociation treatment allowing confirmation of diagnosis of envenomation post-antivenom.

An application of capsid-specific artificial ankyrin repeat protein produced in E. coli for immunochromatographic assay as a surrogate for antibody

Immunochromatographic strip test is a unique type of rapid test that has been developed for use as part of a diagnostic kit for the rapid detection of antibodies and/or other proteins of interest. For the detection of target proteins, most of the commercial tests are assembled based on the conjugation of colloidal gold particles to monoclonal antibodies embedded within the conjugate pad of a strip test. In this study, we tested the novel concept of using an artificial non-antibody structure for generating a colloidal gold conjugate (CGC). We exploited the property of an ankyrin repeat protein that specifically binds to the HIV-1 capsid protein termed Ank(GAG)1D4. This construct was applied as a model structure to create Ank1D4-CGC and used as a new type of visible detector system and termed it ankyrin-based immunochromatographic strip (ABIS) test. The ABIS test was shown to be highly sensitive with a lower limit of detection of the target protein at 0.1 μg/ml. Moreover, the ABIS test was not only highly sensitive but also shared a level of specificity within the same range of the commercial test kit. The results of the studies presented herein therefore demonstrate the novel application of an artificial non-immunoglobulin structure (ankyrin repeat protein) as the new line of a visible detector using a rapid diagnostic test with characteristics that have the potential to be superior to those that utilize antibody-based tests.

Using a simplified human immunodeficiency virus type 1 p24 antigen assay to diagnose pediatric HIV-infection in Malawi

BACKGROUND

There is a worldwide need for a pediatric HIV-1 diagnostic test that has a high diagnostic accuracy, is technically simple and cost efficient. The Up24 HIV-1 assay, which requires both the HIV-1 p24 ELISA and the ELAST signal amplification kit, has previously been shown to be a robust tool to diagnose pediatric HIV-1 from dried whole blood spots (DBS) (Cachafeiro et al., JCM 2009;47:459-62(13)). In order to make the assay more accessible to a resource-limited clinical setting, we eliminated the ELAST system, which simplified the Up24 assay, reduced its cost, and tested the accuracy of the modified assay in a rural Malawian hospital.

OBJECTIVES

In this proof of concept study, we tested the ability of a simplified Up24 antigen assay, without ELAST, to detect HIV-1 on DBS obtained via heel prick from 6-week-old Malawian infants.

STUDY DESIGN

A case-control study of DBS collected from 113 HIV-infected and 109 HIV-negative infants, using the HIV-1 DNA PCR assay as the reference standard.

RESULTS

The simplified HIV-1 Up24 assay had a sensitivity and specificity of 84% and 98%, respectively. When HIV-1 prevalence is 15%, the positive- and negative-predictive values are 89% and 97%, respectively.

CONCLUSION

The simplified Up24 assay has a good positive- and a robust negative-predictive values, is easier to perform and has a reduced cost compared to both HIV DNA PCR and Up24 assays. With additional testing, the simplified Up24 assay has the potential to increase global access to pediatric HIV-1 diagnostics.

Evaluation of the ultrasensitive human immunodeficiency virus type 1 (HIV-1) p24 antigen assay performed on dried blood spots for diagnosis of HIV-1 infection in infants

The diagnostic accuracy of the modified p24 antigen assay performed on pediatric dried blood spots was evaluated. Samples analyzed within 6 weeks of collection yielded no false-positive results (specificity, 100%) and few false-negative results (sensitivity, 96.5% to 98.3%). Laboratory services with limited resources should assess this option for routine infant diagnosis.

Potential of a simplified p24 assay for early diagnosis of infant human immunodeficiency virus type 1 infection in Haiti

With global efforts to scale up the prevention of mother-to-child transmission services and pediatric antiretroviral therapy, there is an urgent need to introduce a simple, low-cost infant human immunodeficiency virus test in the field. We postulated that the p24 antigen capture enzyme-linked immunosorbent assay could be simplified by eliminating signal amplification without compromising diagnostic accuracy.

Ultrasensitive human immunodeficiency virus type 1 p24 antigen assay modified for use on dried whole-blood spots as a reliable, affordable test for infant diagnosis

The ultrasensitive human immunodeficiency virus (HIV) p24 antigen assay was modified for use on pediatric dried whole-blood spots on Whatman no. 1 filter paper. The modified assay was found to be reliable and accurate, making it an affordable tool for pediatric HIV diagnosis in developing countries.

Magnetic micro- and nanoparticle mediated activation of mechanosensitive ion channels

Most cells are known to respond to mechanical cues, which initiate biochemical signalling pathways and play a role in cell membrane electrodynamics. These cues can be transduced either via direct activation of mechanosensitive (MS) ion channels or through deformation of the cell membrane and cytoskeleton. Investigation of the function and role of these ion channels is a fertile area of research and studies aimed at characterizing and understanding the mechanoactive regions of these channels and how they interact with the cytoskeleton are fundamental to discovering the specific role that mechanical cues play in cells. In this review, we will focus on novel techniques, which use magnetic micro- and nanoparticles coupled to external applied magnetic fields for activating and investigating MS ion channels and cytoskeletal mechanics.

Evaluation of an ultrasensitive p24 antigen assay as a potential alternative to human immunodeficiency virus type 1 RNA viral load assay in resource-limited settings

An inexpensive enzyme-linked immunosorbent assay method for human immunodeficiency virus type 1 quantitation, ultrasensitive p24 antigen assay (Up24), was compared with RNA viral load assay (VL). Up24 had 100% sensitivity of detection at a viral load of >/=30,000, with sensitivity of 46.4% at a viral load of <30,000 (232 specimens from 65 seropositive subjects). The assay was highly reproducible, with excellent correlation between duplicates and among three laboratories.

p24 Antigen detection assay modified with a booster step for diagnosis and monitoring of human immunodeficiency virus type 1 infection

We modified a p24 antigen enzyme-linked immunosorbent assay as a method for diagnosis and monitoring of human immunodeficiency virus type 1 (HIV-1) subtype E infection. This modified assay is based on the use of preheated immune complex dissociation combined with a booster step using a regular Vironostika HIV-1 p24 antigen assay (bioMerieux) to decrease the lower limit of p24 antigen detection from 10 pg/ml (lower limit achievable when using a regular p24 antigen assay) to 0.5 pg/ml (100 virions/ml) by the new method. The correlation between the values obtained by the HIV-1 RNA (Amplicor HIV-1 Monitor) assay and the p24 antigen assay modified with a booster step antigen assay in 160 frozen plasma samples with known viral load and 80 blind fresh plasma samples by Spearman rank were 0.671 (R(2) = 0.450; P < 0.01) and 0.782 (R(2) = 0.612; P < 0.01). During antiretroviral treatment, the change of p24 antigen level at >/=0.5 log correlated well with the level of HIV-1 in plasma. In order to improve the early diagnosis of HIV-1 infection in 121 infants born to HIV-1-infected mothers, a heat-denatured plasma p24 antigen assay modified with a booster step was compared with DNA-PCR and HIV RNA (nucleic acid sequence-based amplification) assays. The sensitivity of the antigen test modified with a booster step was similar to that of the HIV-1 RNA (NASBA QL) assay and better than that of the DNA-PCR assay (100 versus 61.90%) for subjects 1 to 2 months old. The overall results from this study might renew interest in p24 antigen detection as an easily affordable alternative method for diagnosis of HIV-1 infection and monitoring of disease progression in developing countries.

Comparison of an assay using signal amplification of the heat-dissociated p24 antigen with the Roche Monitor human immunodeficiency virus RNA assay

We compared an assay using signal amplification of a heat-dissociated p24 antigen (HDAg) with the Roche Monitor human immunodeficiency virus (HIV) RNA assay. The two assays gave comparable results when 130 specimens from 130 patients were tested (r = 0.60, P < 0.0001). The HDAg assay was almost as sensitive (85%) as the Roche HIV RNA kit (95%), just as specific (25 negative results from 25 HIV seronegative volunteers [100%]), less variable (mean log standard deviation of 0.07 compared to 0.11 when eight specimens were tested three or four times), and less expensive (reagent and labor costs, $8 versus $75). The assay appeared to be useful for monitoring established patients (n = 17) and identifying seroconverters (n = 4). HIV subtypes A to F were all recognized. This assay should be useful for monitoring patients in resource-poor countries and for monitoring vaccine recipients.