p24 antigen rapid test for diagnosis of acute pediatric HIV infection

New technologies and reagents in lateral flow assay (LFA) designs for enhancing accuracy and sensitivity

Lateral flow assays (LFAs) are a popular method for quick and affordable diagnostic testing because they are easy to use, portable, and user-friendly. However, LFA design has always faced challenges regarding sensitivity, accuracy, and complexity of the operation. By integrating new technologies and reagents, the sensitivity and accuracy of LFAs can be improved while minimizing the complexity and potential for false positives. Surface enhanced Raman spectroscopy (SERS), photoacoustic techniques, fluorescence resonance energy transfer (FRET), and the integration of smartphones and thermal readers can improve LFA accuracy and sensitivity. To ensure reliable and accurate results, careful assay design and validation, appropriate controls, and optimization of assay conditions are necessary. Continued innovation in LFA technology is crucial to improving the reliability and accuracy of rapid diagnostic testing and expanding its applications to various areas, such as food testing, water quality monitoring, and environmental testing.

Increasing the initiation of antiretroviral therapy through optimal placement of diagnostic technologies for pediatric HIV in Zimbabwe: A modeling analysis

OBJECTIVES

Point-of-care (POC) devices for infant HIV testing provide timely result-return and increase antiretroviral (ART) initiation. We aimed to optimally locate POC devices to increase 30-day ART initiation in Matabeleland South, Zimbabwe.

METHODS

We developed an optimization model to identify the locations for limited POC devices at health facilities, maximizing the number of infants who receive HIV test results and initiate ART within 30 days of testing. We compared location-optimization model results to non-model-based decision heuristics, which are more practical and less data-intensive. Heuristics assign POC devices based on demand, test positivity, laboratory result-return probability, and POC machine functionality.

RESULTS

With the current placement of 11 existing POC machines, 37% of all tested infants with HIV were projected to receive results and 35% were projected to initiate ART within 30 days of testing. With optimal placement of existing machines, 46% were projected to receive results and 44% to initiate ART within 30 days, retaining three machines in current locations, moving eight to new facilities. Relocation based on the highest POC device functionality would be the best-performing heuristic decision (44% receiving results and 42% initiating ART withing 30 days); although, it still would not perform as well as the optimization-based approach.

CONCLUSION

Optimal and ad hoc heuristic relocation of limited POC machines would increase timely result-return and ART initiation, without further, often costly, interventions. Location optimization can enhance decision-making regarding the placement of medical technologies for HIV care.

The contemporary immunoassays for HIV diagnosis: a concise overview

Recent advances in human immunodeficiency virus (HIV) diagnostics have improved the management of disease progression significantly, which have also boosted the efficacy of antiviral therapies. The detection of HIV at the earliest is very important. A highly recognized and effective virological biomarker for acute HIV infections is p24 antigen. This brief overview is based on advances of HIV diagnosis while focusing on the latest HIV testing technologies including HIV-specific antigens detecting assays of both anti-HIV antibodies and p24 antigen. In addition to other emerging molecular diagnostics for acute HIV infection, the utilization of p24 antigen has been summarized. Moreover, it has been explained how these immunoassays have reduced the window period for detection of HIV in the acute stage of infection.

Lateral flow assays for viruses diagnosis: Up-to-date technology and future prospects

Bacteria, viruses, and parasites are harmful microorganisms that cause infectious diseases. Early detection of diseases is critical to prevent disease transmission and provide epidemic preparedness, as these can cause widespread deaths and public health crises, particularly in resource-limited countries. Lateral flow assay (LFA) systems are simple-to-use, disposable, inexpensive diagnostic devices to test biomarkers in blood and urine samples. Thus, LFA has recently received significant attention, especially during the pandemic. Here, first of all, the design principles and working mechanisms of existing LFA methods are examined. Then, current LFA implementation strategies are presented for communicable disease diagnoses, including COVID-19, zika and dengue, HIV, hepatitis, influenza, malaria, and other pathogens. Furthermore, this review focuses on an overview of current problems and accessible solutions in detecting infectious agents and diseases by LFA, focusing on increasing sensitivity with various detection methods. In addition, future trends in LFA-based diagnostics are envisioned.

Point-of-care p24 antigen detection for early infant diagnosis of HIV infection: cross-sectional and longitudinal studies in Zambia

BACKGROUND

Early infant diagnosis of HIV infection is challenging in sub-Saharan Africa, particularly in rural areas, leading to delays in diagnosis and treatment. Use of a point-of-care test would overcome many challenges. This study evaluated the validity of a novel point-of-care p24 antigen detection test (LYNX) in rural and urban settings in southern Zambia.

METHODS

Two studies were conducted: a cross-sectional study from 2014 to 2015 at Macha Hospital (LYNX Hospital study) and a longitudinal study from 2016 to 2018 at 12 health facilities in Southern Province, Zambia (NSEBA study). In both studies, children attending the facilities for early infant diagnosis were enrolled and a blood sample was collected for routine testing at the central lab and immediate on-site testing with the LYNX test. The performance of the LYNX test was measured in comparison to nucleic acid-based testing at the central lab.

RESULTS

In the LYNX Hospital study, 210 tests were performed at a median age of 23.5 weeks (IQR: 8.9, 29.0). The sensitivity and specificity of the test were 70.0 and 100.0%, respectively. In the NSEBA study, 2608 tests were performed, including 1305 at birth and 1222 on children ≥4 weeks of age. For samples tested at birth, sensitivity was 13.6% (95% CI: 2.9, 34.9) and specificity was 99.6% (95% CI: 99.1, 99.9). While specificity was high for all ages, sensitivity increased with age and was higher for participants tested at ≥4 weeks of age (80.6%; 95% CI: 67.4, 93.7). Children with positive nucleic acid tests were more likely to be negative by the LYNX test if their mother received antiretroviral therapy during pregnancy (60.7% vs. 24.2%; p = 004).

CONCLUSIONS

Considering the high specificity and moderate sensitivity that increased with age, the LYNX test could be of value for early infant diagnosis for infants ≥4 weeks of age, particularly in rural areas where centralized testing leads to long delays. Point-of-care tests with moderate sensitivity and high specificity that are affordable, easy-to-use, and easily implemented and maintained should be developed to expand access to testing and deliver same-day results to infants in areas where it is not feasible to implement nucleic acid-based point-of-care assays.

Development and optimization of thermal contrast amplification lateral flow immunoassays for ultrasensitive HIV p24 protein detection

Detection of human immunodeficiency virus (HIV) p24 protein at a single pg/ml concentration in point-of-care (POC) settings is important because it can facilitate acute HIV infection diagnosis with a detection sensitivity approaching that of laboratory-based assays. However, the limit of detection (LOD) of lateral flow immunoassays (LFAs), the most prominent POC diagnostic platform, falls short of that of laboratory protein detection methods such as enzyme-linked immunosorbent assay (ELISA). Here, we report the development and optimization of a thermal contrast amplification (TCA) LFA that will allow ultrasensitive detection of 8 pg/ml p24 protein spiked into human serum at POC, approaching the LOD of a laboratory test. To achieve this aim, we pursued several innovations as follows: (a) defining a new quantitative figure of merit for LFA design based on the specific to nonspecific binding ratio (BR); (b) using different sizes and shapes of gold nanoparticles (GNPs) in the systematic optimization of TCA LFA designs; and (c) exploring new laser wavelengths and power regimes for TCA LFA designs. First, we optimized the blocking buffer for the membrane and running buffer by quantitatively measuring the BR using a TCA reader. The TCA reader interprets the thermal signal (i.e., temperature) of GNPs within the membrane when irradiated by a laser at the plasmon resonance wavelength of the particle. This process results in higher detection and quantitation of GNPs than in traditional visual detection (i.e., color intensity). Further, we investigated the effect of laser power (30, 100, 200 mW), GNP size and shape (30 and 100 nm gold spheres, 150 nm gold-silica shells), and laser wavelength (532, 800 nm). Applying these innovations to a new TCA LFA design, we demonstrated that 100 nm spheres with a 100 mW 532 nm laser provided the best performance (i.e., LOD = 8 pg/ml). This LOD is significantly better than that of the current colorimetric LFA and is in the range of the laboratory-based p24 ELISA. In summary, this TCA LFA for p24 protein shows promise for detecting acute HIV infection in POC settings.

The advanced role of carbon quantum dots in nanomedical applications

Carbon quantum dots (CQDs) have emerged as a potential material in the diverse fields of biomedical applications due to their numerous advantageous properties including fluorescence, water solubility, biocompatibility, low toxicity, small size and ease of modification, inexpensive scale-up production, and versatile conjugation with other nanoparticles. Thus, CQDs became a preferable choice in various biomedical applications such as nanocarriers for drugs, therapeutic genes, photosensitizers, and antibacterial molecules. Further, their potentials have also been verified in multifunctional diagnostic platforms, cellular and bacterial bio-imaging, development of theranostics nanomedicine, etc. This review provides a concise insight into the progress and evolution in the field of CQD research with respect to methods/materials available in bio-imaging, theranostics, cancer/gene therapy, diagnostics, etc. Further, our discussion is extended to explore the role of CQDs in nanomedicine which is considered to be the future of biomedicine. This study will thus help biomedical researchers in tapping the potential of CQDs to overcome various existing technological challenges.

Diagnosis of Human Immunodeficiency Virus Infection

HIV diagnostics have played a central role in the remarkable progress in identifying, staging, initiating, and monitoring infected individuals on life-saving antiretroviral therapy. They are also useful in surveillance and outbreak responses, allowing for assessment of disease burden and identification of vulnerable populations and transmission "hot spots," thus enabling planning, appropriate interventions, and allocation of appropriate funding. HIV diagnostics are critical in achieving epidemic control and require a hybrid of conventional laboratory-based diagnostic tests and new technologies, including point-of-care (POC) testing, to expand coverage, increase access, and positively impact patient management. In this review, we provide (i) a historical perspective on the evolution of HIV diagnostics (serologic and molecular) and their interplay with WHO normative guidelines, (ii) a description of the role of conventional and POC testing within the tiered laboratory diagnostic network, (iii) information on the evaluations and selection of appropriate diagnostics, (iv) a description of the quality management systems needed to ensure reliability of testing, and (v) strategies to increase access while reducing the time to return results to patients. Maintaining the central role of HIV diagnostics in programs requires periodic monitoring and optimization with quality assurance in order to inform adjustments or alignment to achieve epidemic control.

p24 revisited: a landscape review of antigen detection for early HIV diagnosis

: Despite major advances in HIV testing, early detection of infection at the point of care (PoC) remains a key challenge. Although rapid antibody PoC and laboratory-based nucleic acid amplification tests dominate the diagnostics market, the viral capsid protein p24 is recognized as an alternative early virological biomarker of infection. However, the detection of ultra-low levels of p24 at the PoC has proven challenging. Here we review the landscape of p24 diagnostics to identify knowledge gaps and barriers and help shape future research agendas. Five hundred and seventy-four research articles to May 2018 that propose or evaluate diagnostic assays for p24 were identified and reviewed. We give a brief history of diagnostic development, and the utility of p24 as a biomarker in different populations such as infants, the newly infected, those on preexposure prophylaxis and self-testers. We review the performance of commercial p24 assays and consider elements such as immune complex disruption, resource-poor settings, prevalence, and assay antibodies. Emerging and ultrasensitive assays are reviewed and show a number of promising approaches but further translation has been limited. We summarize studies on the health economic benefits of using antigen testing. Finally, we speculate on the future uses of high-performance p24 assays, particularly, if available in self-test format.

Recent advances in nanoparticle-based lateral flow immunoassay as a point-of-care diagnostic tool for infectious agents and diseases

Recent advances in lateral flow immunoassay-based devices as a point-of-care analytical tool for the detection of infectious diseases are reviewed.

Single Domain Antibodies as New Biomarker Detectors

Biomarkers are defined as indicators of biological processes, pathogenic processes, or pharmacological responses to a therapeutic intervention. Biomarkers have been widely used for early detection, prediction of response after treatment, and for monitoring the progression of diseases. Antibodies represent promising tools for recognition of biomarkers, and are widely deployed as analytical tools in clinical settings. For immunodiagnostics, antibodies are now exploited as binders for antigens of interest across a range of platforms. More recently, the discovery of antibody surface display and combinatorial chemistry techniques has allowed the exploration of new binders from a range of animals, for instance variable domains of new antigen receptors (V_NAR) from shark and variable heavy chain domains (V_HH) or nanobodies from camelids. These single domain antibodies (sdAbs) have some advantages over conventional murine immunoglobulin owing to the lack of a light chain, making them the smallest natural biomarker binders thus far identified. In this review, we will discuss several biomarkers used as a means to validate diseases progress. The potential functionality of modern singe domain antigen binders derived from phylogenetically early animals as new biomarker detectors for current diagnostic and research platforms development will be described.

A Stimuli-Responsive, Binary Reagent System for Rapid Isolation of Protein Biomarkers

Magnetic microbeads exhibit rapid separation characteristics and are widely employed for biomolecule and cell isolations in research laboratories, clinical diagnostics assays, and cell therapy manufacturing. However, micrometer particle diameters compromise biomarker recognition, which leads to long incubation times and significant reagent demands. Here, a stimuli-responsive binary reagent system is presented that combines the nanoscale benefits of efficient biomarker recognition and the microscale benefits of rapid magnetic separation. This system comprises magnetic nanoparticles and polymer-antibody (Ab) conjugates that transition from hydrophilic nanoscale reagents to microscale aggregates in response to temperature stimuli. The binary reagent system was benchmarked against Ab-labeled Dynabeads in terms of biomarker isolation kinetics, assay speed, and reagent needs. Surface plasmon resonance (SPR) measurements showed that polymer conjugation did not significantly alter the Ab's binding affinity or kinetics. ELISA analysis showed that the unconjugated Ab, polymer-Ab conjugates, and Ab-labeled Dynabeads exhibited similar equilibrium dissociation constants (Kd), ∼2 nM. However, the binary reagent system isolated HIV p24 antigen from spiked serum specimens (150 pg/mL) much more quickly than Dynabeads, which resulted in shorter binding times by tens of minutes, or about 30-50% shorter overall assay times. The binary reagent system showed improved performance because the Ab molecules were not conjugated to large, solid microparticle surfaces. This stimuli-responsive binary reagent system illustrates the potential advantages of nanoscale reagents in molecule and cell isolations for both research and clinical applications.

Point-of-care diagnostics, a major opportunity for change in traditional diagnostic approaches: potential and limitations

'Point-of-care' (POC) diagnostics are a powerful emerging healthcare approach. They can rapidly provide statistically significant results, are simple to use, do not require specialized equipment and are cost-effective. For these reasons, they have the potential to play a major role in revolutionizing the diagnosis, initiation and monitoring of treatment of major global diseases. This review focuses on antibody-based POC devices that target four major global diseases: cardiovascular diseases, prostate cancer, HIV infection and tuberculosis. The key statistics and pathology of each disease is described in detail, followed by an in-depth discussion on emerging POC devices that target each disease, highlighting their potential and limitations.

A serial risk score approach to disease classification that accounts for accuracy and cost

The performance of diagnostic tests for disease classification is often measured by accuracy (e.g., sensitivity or specificity); however, costs of the diagnostic test are a concern as well. Combinations of multiple diagnostic tests may improve accuracy, but incur additional costs. Here, we consider serial testing approaches that maintain accuracy while controlling costs of the diagnostic tests. We present a serial risk score classification approach. The basic idea is to sequentially test with additional diagnostic tests just until persons are classified. In this way, it is not necessary to test all persons with all tests. The methods are studied in simulations and compared with logistic regression. We applied the methods to data from HIV cohort studies to identify HIV infected individuals who are recently infected (<1 year) by testing with assays for multiple biomarkers. We find that the serial risk score classification approach can maintain accuracy while achieving a reduction in cost compared to testing all individuals with all assays.

Acute HIV-1 infection is as common as malaria in young febrile adults seeking care in coastal Kenya

Background:

Febrile adults are usually not tested for acute HIV-1 infection (AHI) in Africa. We assessed a strategy to diagnose AHI among young adult patients seeking care.

Methods:

Young adults (<30 years) who met predefined AHI criteria at care seeking, including fever, sexually transmitted disease symptoms, diarrhoea, body pains or multiple partners were referred from five pharmacies and screened at five health facilities. Prevalent HIV-1 was diagnosed by nationally recommended serial rapid HIV-1 testing. Willing HIV-1-negative patients were evaluated for AHI, defined as a positive p24 antigen test, and subsequent seroconversion or RNA detection. Febrile patients evaluated for AHI were also screened for malaria using a rapid test, with PCR confirmation of positives.

Results:

In 3602 adults seeking care, overall HIV-1 prevalence was 3.9%: 7.6% (68/897) among patients meeting AHI criteria vs. 2.6% (71/2705) among those who did not (P < 0.001). AHI was diagnosed in five of 506 HIV-1-negative or discordant patients who met AHI risk criteria and were completely evaluated [prevalence 1.0%, 95% confidence interval (CI) 0.3–2.3%]. Of these five AHI cases, four were diagnosed among the 241 patients with fever (prevalence 1.7%, 95% CI 0.5–4.2%), vs. one among 265 non-febrile patients (prevalence 0.4%, 95% CI 0.0–2.0%, P = 0.1). Malaria was confirmed by PCR in four (1.7%) of the 241 febrile patients.

Conclusion:

AHI was as common as confirmed malaria in young febrile adults seeking care. An AHI detection strategy targeting young febrile adults seeking care at pharmacies and health facilities is feasible and should be considered as an HIV-prevention strategy in high-transmission settings.

Point of Care Technologies for HIV

Effective prevention of HIV/AIDS requires early diagnosis, initiation of therapy, and regular plasma viral load monitoring of the infected individual. In addition, incidence estimation using accurate and sensitive assays is needed to facilitate HIV prevention efforts in the public health setting. Therefore, more affordable and accessible point-of-care (POC) technologies capable of providing early diagnosis, HIV viral load measurements, and CD4 counts in settings where HIV is most prevalent are needed to enable appropriate intervention strategies and ultimately stop transmission of the virus within these populations to achieve the future goal of an AIDS-free generation. This review discusses the available and emerging POC technologies for future application to these unmet public health needs.

Micro- and nanotechnology for HIV/AIDS diagnostics in resource-limited settings

Thirty-four million people are living with HIV worldwide, a disproportionate number of whom live in resource-limited settings. Proper clinical management of AIDS, the disease caused by HIV, requires regular monitoring of both the status of the host's immune system and levels of the virus in their blood. Therefore, more accessible technologies capable of performing a CD4+ T cell count and HIV viral load measurement in settings where HIV is most prevalent are desperately needed to enable better treatment strategies and ultimately quell the spread of the virus within populations. This review discusses micro- and nanotechnology solutions to performing these key clinical measurements in resource-limited settings.

A liposome-based ion release impedance sensor for biological detection

Low-cost detection of pathogens and biomolecules at the point-of-care promises to revolutionize medicine through more individualized monitoring and increased accessibility to diagnostics in remote and resource-limited areas. While many approaches to biosensing are still limited by expensive components or inadequate portability, we present here an ELISA-inspired lab-on-a-chip strategy for biological detection based on liposome tagging and ion-release impedance spectroscopy. Ion-encapsulating dipalmitoylphosphatidylcholine (DPPC) liposomes can be functionalized with antibodies and are stable in deionized water yet permeabilized for ion release upon heating, making them ideal reporters for electrical biosensing of surface-immobilized antigens. We demonstrate the quantification of these liposomes by real-time impedance measurements, as well as the qualitative detection of viruses as a proof-of-concept toward a portable platform for viral load determination which can be applied broadly to the detection of pathogens and other biomolecules.

Point-of-care testing for sexually transmitted infections: recent advances and implications for disease control

PURPOSE OF REVIEW

Sexually transmitted infections (STIs) remain a major global public health issue, with more than 448 million incident bacterial infections each year. We review recent advances in STI point-of-care (POC) testing and implications for STI prevention and control.

RECENT FINDINGS

Accurate immunochromatographic assays to detect HIV, hepatitis C virus (HCV) and syphilis antibodies have made home or supervised self-testing possible. Several studies have demonstrated feasibility and excellent test characteristics for HIV, HCV and syphilis POC tests. Rapid oral HIV tests are now available for purchase at retail sites across the United States. Combined HIV and syphilis tests using a single finger prick blood sample are under evaluation.

SUMMARY

Oral POC STI tests with comparable performance to blood-based POC tests are available for self-testing. POC tests can expand screening, improve syndromic management and reduce loss to follow up. POC STI tests have the potential to facilitate prompt treatment and partner services. POC STI tests create opportunities for new social and financial models of community-based testing services. Increasing equity and access to testing will create challenges in linkage to care, quality assurance, partner services and surveillance. These important developments warrant research to understand appropriate contexts for implementation.

Rapid detection of HIV-1 proviral DNA for early infant diagnosis using recombinase polymerase amplification

Early diagnosis and treatment of human immunodeficiency virus type 1 (HIV-1) infection in infants can greatly reduce mortality rates. However, current infant HIV-1 diagnostics cannot reliably be performed at the point of care, often delaying treatment and compromising its efficacy. Recombinase polymerase amplification (RPA) is a novel technology that is ideal for an HIV-1 diagnostic, as it amplifies target DNA in <20 min at a constant temperature, without the need for complex thermocycling equipment. Here we tested 63 HIV-1-specific primer and probe combinations and identified two RPA assays that target distinct regions of the HIV-1 genome (long terminal repeat [LTR] and pol) and can reliably detect 3 copies of proviral DNA by the use of fluorescence detection and lateral-flow strip detection. These pol and LTR primers amplified 98.6% and 93%, respectively, of the diverse HIV-1 variants tested. This is the first example of an isothermal assay that consistently detects all of the major HIV-1 global subtypes.

Linkage of HIV-infected infants from diagnosis to antiretroviral therapy services across the Western Cape, South Africa

Introduction

Early infant diagnosis (EID) of HIV infection is an important service to reduce paediatric morbidity and mortality related to HIV/AIDS. Although South Africa has a national EID programme based on PCR testing, there are no population-wide data on the linkage of infants testing HIV PCR-positive to HIV care and treatment services.

Methods

We conducted a retrospective analysis of all public sector laboratory data from across the Western Cape province between 2005 and 2011. We linked positive HIV PCR results to subsequent HIV viral load testing to determine the proportion of infants who were successfully linked to HIV care.

Results

A total of 83 698 unique infant HIV PCR tests were documented, of which 6322 (8%) were PCR positive. The proportion of PCR-positive children declined from 12% in 2005 to 3% in 2011. Of the children testing PCR-positive, 4105 (65%) had subsequent viral load testing indicating successful linkage to care. The proportion of successfully linked infants increased from 54% in 2005 to 71% in 2010, while the median delay in days to successful linkage decreased from 146 days in 2005 to 33 days in 2010.

Discussion

From 2005 to 2011 there has been a reduction in the proportion of children testing HIV PCR-positive, and an increase in the proportion of infected infants successfully linked to HIV care and treatment, in this setting. However a large proportion of infected infants remain unlinked to antiretroviral therapy services and there is a clear need for interventions to further strengthen EID programmes.

Low-cost tools for diagnosing and monitoring HIV infection in low-resource settings

Low-cost technologies to diagnose and monitor human immunodeficiency virus (HIV) infection in developing countries are a major subject of current research and health care in the developing world. With the great need to increase access to affordable HIV monitoring services in rural areas of developing countries, much work has been focus on the development of point-of-care technologies that are affordable, robust, easy to use, portable and of sufficient quantitative accuracy to enable clinical decision-making. For diagnosis of HIV infection, some low-cost tests, such as lateral flow tests and enzyme-linked immunosorbent assays, are already in place and well established. However, portable quantitative tests for rapid HIV monitoring at the point of care have only recently been introduced to the market. In this review, we discuss low-cost tests for HIV diagnosis and monitoring in low-resource settings, including promising technologies for use at the point of care, that are available or close to market.

A lateral flow assay for quantitative detection of amplified HIV-1 RNA

Although the accessibility of HIV treatment in developing nations has increased dramatically over the past decade, viral load testing to monitor the response of patients receiving therapy is often unavailable. Existing viral load technologies are often too expensive or resource-intensive for poor settings, and there is no appropriate HIV viral load test currently available at the point-of-care in low resource settings. Here, we present a lateral flow assay that employs gold nanoparticle probes and gold enhancement solution to detect amplified HIV RNA quantitatively. Preliminary results show that, when coupled with nucleic acid sequence based amplification (NASBA), this assay can detect concentrations of HIV RNA that match the clinically relevant range of viral loads found in HIV patients. The lateral flow test is inexpensive, simple and rapid to perform, and requires few resources. Our results suggest that the lateral flow assay may be integrated with amplification and sample preparation technologies to serve as an HIV viral load test for low-resource settings.

Discerning Trends in Multiplex Immunoassay Technology with Potential for Resource-Limited Settings

BACKGROUND

In the search for more powerful tools for diagnoses of endemic diseases in resource-limited settings, we have been analyzing technologies with potential applicability. Increasingly, the process focuses on readily accessible bodily fluids combined with increasingly powerful multiplex capabilities to unambiguously diagnose a condition without resorting to reliance on a sophisticated reference laboratory. Although these technological advances may well have important implications for the sensitive and specific detection of disease, to date their clinical utility has not been demonstrated, especially in resource-limited settings. Furthermore, many emerging technological developments are in fields of physics or engineering, which are not readily available to or intelligible to clinicians or clinical laboratory scientists.

CONTENT

This review provides a look at technology trends that could have applicability to high-sensitivity multiplexed immunoassays in resource-limited settings. Various technologies are explained and assessed according to potential for reaching relevant limits of cost, sensitivity, and multiplex capability. Frequently, such work is reported in technical journals not normally read by clinical scientists, and the authors make enthusiastic claims for the potential of their technology while ignoring potential pitfalls. Thus it is important to draw attention to technical hurdles that authors may not be publicizing.

SUMMARY

Immunochromatographic assays, optical methods including those involving waveguides, electrochemical methods, magnetorestrictive methods, and field-effect transistor methods based on nanotubes, nanowires, and nanoribbons reveal possibilities as next-generation technologies.

Testing for acute HIV infection: implications for treatment as prevention

PURPOSE OF REVIEW

The aim of this study is to give an overview of the recent literature related to HIV testing with an emphasis on detecting acute HIV infection. Testing technology as well as implications for treatment as prevention will be discussed.

RECENT FINDINGS

HIV testing technology continues to evolve. Advances include updated immunologic formats that detect both HIV antibody and antigen (4th generation assays), new nucleic acid amplification tests, and continued development of rapid assays that can be used in either clinical or nonclinical settings. Because of these advances there are proposed changes for HIV diagnostic algorithms to encourage detection of acute infection. These technologic advances have implications for HIV prevention as testing is a cornerstone for all HIV prevention strategies. There is considerable new research indicating that treatment may be an important aspect of HIV prevention. Data also suggest that detection of acute infection will be important for the success of these prevention strategies.

SUMMARY

Continued improvements in technology and testing practice are vital for the success of HIV prevention. Detection of acute or early HIV infection will likely play a key role in the success of treatment as prevention, as well as play an important role in ongoing behavioral prevention strategies.

Amorphous carbon nanoparticles: a versatile label for rapid diagnostic (immuno)assays

Carbon nanoparticles (CNPs) labeled with reporter molecules can serve as signaling labels in rapid diagnostic assays as an alternative to gold, colored latex, silica, quantum dots, or up-converting phosphor nanoparticles. Detailed here is the preparation of biomolecule-labeled CNPs and examples of their use as a versatile label. CNPs can be loaded with a range of biomolecules, such as DNA, antibodies, and proteins (e.g., neutravidin or a fusion protein of neutravidin with an enzyme), and the resulting conjugates can be used to detect analytes of high or low molecular mass.

Early infant HIV-1 diagnosis programs in resource-limited settings: opportunities for improved outcomes and more cost-effective interventions

Early infant diagnosis (EID) of HIV-1 infection confers substantial benefits to HIV-infected and HIV-uninfected infants, to their families, and to programs providing prevention of mother-to-child transmission (PMTCT) services, but has been challenging to implement in resource-limited settings. In order to correctly inform parents/caregivers of infant infection status and link HIV-infected infants to care and treatment, a 'cascade' of events must successfully occur. A frequently cited barrier to expansion of EID programs is the cost of the required laboratory assays. However, substantial implementation barriers, as well as personnel and infrastructure requirements, exist at each step in the cascade. In this update, we review challenges to uptake at each step in the EID cascade, highlighting that even with the highest reported levels of uptake, nearly half of HIV-infected infants may not complete the cascade successfully. We next synthesize the available literature about the costs and cost effectiveness of EID programs; identify areas for future research; and place these findings within the context of the benefits and challenges to EID implementation in resource-limited settings.

Membrane-based plasma collection device for point-of-care diagnosis of HIV

A major requirement for the development of point-of-care tests for the detection of disease analytes is the need to separate plasma from whole blood in an efficient and rapid manner. Furthermore, the separated plasma must be able to elute efficiently the analyte of interest and serve effectively as a physical matrix to deliver the equivalent of neat plasma for downstream diagnostic analysis. Additionally, many applications require the use of heat shock to liberate immunocomplexed antigen found in the collected plasma. A membrane-based filter method is reported for rapid and efficient collection of plasma from a whole blood sample that is compatible with heat shock. Using pediatric human immunodeficiency virus as an example, this device elutes 100% of the input p24 core antigen post-collection and enables heat shock of plasma samples identical to neat plasma treatment.