HIV diagnostics: challenges and opportunities

Towards an ultra-rapid smartphone- connected test for infectious diseases

The development is reported of an ultra-rapid, point-of-care diagnostic device which harnesses surface acoustic wave (SAW) biochips, to detect HIV in a finger prick of blood within 10 seconds (sample-in-result-out). The disposable quartz biochip, based on microelectronic components found in every consumer smartphone, is extremely fast because no complex labelling, amplification or wash steps are needed. A pocket-sized control box reads out the SAW signal and displays results electronically. High analytical sensitivity and specificity are found with model and real patient blood samples. The findings presented here open up the potential of consumer electronics to cut lengthy test waiting times, giving patients on the spot access to potentially life-saving treatment and supporting more timely public health interventions to prevent disease transmission.

Availability and Use of HIV Monitoring and Early Infant Diagnosis Technologies in WHO Member States in 2011-2013: Analysis of Annual Surveys at the Facility Level

BACKGROUND

The Joint United Nations Programme on HIV and AIDS (UNAIDS) 90-90-90 targets have reinforced the importance of functioning laboratory services to ensure prompt diagnosis and to assess treatment efficacy. We surveyed the availability and utilization of technologies for HIV treatment monitoring and early infant diagnosis (EID) in World Health Organization (WHO) Member States.

METHODS AND FINDINGS

The survey questionnaire included 14 structured questions focusing on HIV testing, cluster of differentiation 4 (CD4) testing, HIV viral load (VL) testing, and EID and was administered annually from 2012 to 2014 through WHO country offices, with each survey covering the previous 12-mo period. Across 127 targeted countries, survey response rates were 60% in 2012, 67% in 2013, and 78% in 2014. There were encouraging trends towards increased procurement of CD4 and VL/EID instruments in reporting countries. Globally, the capacity of available CD4 instruments was sufficient to meet the demand of all people living with HIV/AIDS (PLWHA), irrespective of treatment status (4.62 theoretical tests per PLWHA in 2013 [median 7.33; interquartile range (IQR) 3.44-17.75; median absolute deviation (MAD) 4.35]). The capacity of VL instruments was inadequate to cover all PLWHA in many reporting countries (0.44 tests per PLWHA in 2013 [median 0.90; IQR 0.30-2.40; MAD 0.74]). Of concern, only 13.7% of existing CD4 capacity (median 4.3%; IQR 1.1%-12.1%; MAD 3.8%) and only 36.5% of existing VL capacity (median 9.4%; IQR 2.3%-28.9%; MAD 8.2%) was being utilized across reporting countries in 2013. By the end of 2013, 7.4% of all CD4 instruments (5.8% CD4 conventional instruments and 11.0% of CD4 point of care [POC]) and 10% of VL/EID instruments were reportedly not in use because of lack of reagents, the equipment not being installed or deployed, maintenance, and staff training requirements. Major limitations of this survey included under-reporting and/or incomplete reporting in some national programmes and noncoverage of the private sector.

CONCLUSION

This is the first attempt to comprehensively gather information on HIV testing technology coverage in WHO Member States. The survey results suggest that major operational changes will need to be implemented, particularly in low- and middle-income countries, if the 90-90-90 targets are to be met.

Designing Fluorescent Peptide Sensors with Dual Specificity for the Detection of HIV-1 Protease

HIV-1 protease is a key enzyme in the life cycle of HIV/AIDS, as it is responsible for the formation of the mature virus particle. We demonstrate here that phage-display peptides raised against this enzyme can be used as peptide sensors for the detection of HIV-1 protease in a simple, one-pot assay. The presence of the enzyme is detected through an energy transfer between two peptide sensors when simultaneously complexed with the target protein. The multivalent nature of this assay increases the specificity of the detection by requiring all molecules to be interacting in order for there to be a FRET signal. We also perform molecular dynamics simulations to explore the interaction between the protease and the peptides in order to guide the design of these peptide sensors and to understand the mechanisms which cause these simultaneous binding events. This approach aims to facilitate the development of new assays for enzymes that are not dependent on the cleavage of a substrate and do not require multiple washing steps.

Development of a microchip Europium nanoparticle immunoassay for sensitive point-of-care HIV detection

Rapid, sensitive and specific diagnostic assays play an indispensable role in determination of HIV infection stages and evaluation of efficacy of antiretroviral therapy. Recently, our laboratory developed a sensitive Europium nanoparticle-based microtiter-plate immunoassay capable of detecting target analytes at subpicogram per milliliter levels without the use of catalytic enzymes and signal amplification processes. Encouraged by its sensitivity and simplicity, we continued to miniaturize this assay to a microchip platform for the purpose of converting the benchtop assay technique to a point-of-care test. It was found that detection capability of the microchip platform could be readily improved using Europium nanoparticle probes. We were able to routinely detect 5 pg/mL (4.6 attomoles) of HIV-1 p24 antigen at a signal-to-blank ratio of 1.5, a sensitivity level reasonably close to that of microtiter-plate Europium nanoparticle assay. Meanwhile, use of the microchip platform effectively reduced sample/reagent consumption 4.5 fold and shortened total assay time 2 fold in comparison with microtiter plate assays. Complex matrix substance in plasma negatively affected the microchip assays and the effects could be minimized by diluting the samples before loading. With further improvements in sensitivity, reproducibility, usability, assay process simplification, and incorporation of portable time-resolved fluorescence reader, Europium nanoparticle immunoassay technology could be adapted to meet the challenges of point-of-care diagnosis of HIV or other health-threatening pathogens at bedside or in resource-limited settings.

Large-scale graphene micropattern nano-biohybrids: high-performance transducers for FET-type flexible fluidic HIV immunoassays

Large-scale FET-type graphene micropattern (GM) nano-biohybrid-based immunosensor (GMNS) is fabricated in a controlled fashion to detect human immunodeficiency virus 2 antibody. Flexible GMNS shows a highly sensitive response and excellent mechanical bendability. The flexible GMNS in fluidic systems also has a stable response. This is the first experimental demonstration of a large-scale flexible fluidic FET-type immunoassay based on GM nano-biohybrids.

A novel RealTime HIV-1 Qualitative assay for the detection of HIV-1 nucleic acids in dried blood spots and plasma

Abbott RealTime HIV-1 Qualitative is an in vitro real-time PCR assay for detecting HIV-1 nucleic acids in human plasma and dried blood spots (DBS). The assay was designed to be used in diagnosis of HIV-1 infections in pediatric and adult patients, with an emphasis on the applicability in resource-limited settings. Use of DBS facilitates specimen collection from remote areas and transportation to testing laboratories. Small sample input requirement facilitates testing of specimens with limited collection volume. The Abbott RealTime HIV-1 Qualitative assay is capable of detecting HIV-1 group M subtypes A-H, group O and group N samples. HIV-1 virus concentrations detected with 95% probability were 80 copies/mL of plasma using the plasma protocol, and 2469 copies/mL of whole blood using the DBS protocol. The assay detected HIV-1 infection in 13 seroconversion panels an average 10.5 days earlier than an HIV-1 antibody test and 4.9 days earlier than a p24 antigen test. For specimens collected from 6 weeks to 18 months old infants born to HIV-1 positive mothers, assay results using both the DBS and plasma protocols agreed well with the Roche Amplicor HIV-1 DNA Test version 1.5 (95.5% agreement for DBS and 97.8% agreement for plasma).