HIV diagnostic tests: An overview

An HIV-1 Positive Woman Without Usual Immunodeficiency

Introduction: Acquired immune deficiency syndrome (AIDS) inflicts severe damage to the immune system. It transmits from one person to another through blood transfusions and vertical and sexual transmission. It should be noted that almost all papers reporting AIDS emphasized that HIV led to immune deficiency. However, this study reported the first HIV-1 seropositive woman who had an active viral load of HIV-1 without any signs or CD4 lymphocyte count depletion. Case Presentation: This study, for the first time, reported a 46-year-old HIV-1 seropositive woman without any signs and symptoms diagnosed 31 years ago by laboratory tests. Also, it is noteworthy that the patient had not received regular therapeutics during the infection period. Our serologic tests showed an active seropositive patient without any CD4 depletion. The viral load of HIV-1 was 132967.2 u/L, which was quantified by a real-time PCR assay. Also, a CBC test was performed and showed no abnormal results. Conclusions: An untreated HIV-1 positive patient without immunodeficiency is a rare condition, and we found no report of it in the literature. This article reported an HIV-1 positive patient in whom the infection was confirmed several times using the real-time PCR method.

Peptides to combat viral infectious diseases

Viral infectious diseases have resulted in millions of deaths throughout history and have created a significant public healthcare burden. Tremendous efforts have been placed by the scientific communities, health officials and government organizations to detect, treat, and prevent viral infection. However, the complicated life cycle and rapid genetic mutations of viruses demand continuous development of novel medicines with high efficacy and safety profiles. Peptides provide a promising outlook as a tool to combat the spread and re-emergence of viral infection. This article provides an overview of five viral infectious diseases with high global prevalence: influenza, chronic hepatitis B, acquired immunodeficiency syndrome, severe acute respiratory syndrome, and coronavirus disease 2019. The current and potential peptide-based therapies, vaccines, and diagnostics for each disease are discussed.

Ultra-low HIV-1 p24 detection limits with a bioelectronic sensor

Early diagnosis of the infection caused by human immunodeficiency virus type-1 (HIV-1) is vital to achieve efficient therapeutic treatment and limit the disease spreading when the viremia is at its highest level. To this end, a point-of-care HIV-1 detection carried out with label-free, low-cost, and ultra-sensitive screening technologies would be of great relevance. Herein, a label-free single molecule detection of HIV-1 p24 capsid protein with a large (wide-field) single-molecule transistor (SiMoT) sensor is proposed. The system is based on an electrolyte-gated field-effect transistor whose gate is bio-functionalized with the antibody against the HIV-1 p24 capsid protein. The device exhibits a limit of detection of a single protein and a limit of quantification in the 10 molecule range. This study paves the way for a low-cost technology that can quantify, with single-molecule precision, the transition of a biological organism from being "healthy" to being "diseased" by tracking a target biomarker. This can open to the possibility of performing the earliest possible diagnosis.

Barriers and Facilitators to HIV Testing in Migrants in High-Income Countries: A Systematic Review

Migrants, particularly from low- and middle-income countries, are at a heightened risk of adverse HIV outcomes. HIV testing may improve these outcomes. We reviewed and synthesised studies into migrants and HIV testing (outcome variable), published between January 1997 and April 2014. Papers using quantitative, qualitative and mixed methods designs, and samples with adult (≥18 years) migrants from low- and middle-income countries in high-income countries were included in the paper. Of 3155 papers retrieved, 31 met the inclusion criteria and are included in the review. A large number of barriers and facilitators to HIV testing were identified across the individual, social and structural levels. A number of study design and methodological issues, however, inhibited a comprehensive synthesis. There is no doubt that addressing HIV testing in migrants in high-income countries is complex; however, it has important implications for individual, community and population health, and a strong, empirically based response is warranted.

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.

A cocktail of thermally stable, chemically synthesized capture agents for the efficient detection of anti-gp41 antibodies from human sera

We report on a method to improve in vitro diagnostic assays that detect immune response, with specific application to HIV-1. The inherent polyclonal diversity of the humoral immune response was addressed by using sequential in situ click chemistry to develop a cocktail of peptide-based capture agents, the components of which were raised against different, representative anti-HIV antibodies that bind to a conserved epitope of the HIV-1 envelope protein gp41. The cocktail was used to detect anti-HIV-1 antibodies from a panel of sera collected from HIV-positive patients, with improved signal-to-noise ratio relative to the gold standard commercial recombinant protein antigen. The capture agents were stable when stored as a powder for two months at temperatures close to 60(o)C.

Development and evaluation of reverse-transcription loop-mediated isothermal amplification for rapid detection of human immunodeficiency virus type 1

PURPOSE

The objective of this study was to establish a reverse-transcription loop-mediated isothermal amplification (RT-LAMP) method for rapid detection of human immunodeficiency virus type 1 (HIV-1).

MATERIALS AND METHODS

The HIV-1 integrase gene region was selected because it was a conserved part of the HIV-1 genome. Six primers specific to eight regions of the HIV-1 integrase gene were designed. A total of 171 samples (18 HIV-1 confirmed positive samples and 153 serum specimens were collected in this study) were tested by RT-LAMP and reverse-transcription polymerase chain reaction (RT-PCR). After amplification in an isothermal water bath for 45 min, samples containing HIV-1 generated the expected ladder-like products while other viruses generated no product.

RESULTS

The sensitivity and specificity of the RT-LAMP assay were evaluated by comparison with RT-PCR. The assay was significantly more sensitive than normal gel-based RT-PCR.

CONCLUSION

Because it is specific and simple, the RT-LAMP assay can be widely applied in clinical laboratories for rapid detection of HIV-1.

Interlaboratory and interstudy reproducibility of a novel lateral-flow device and influence of antifungal therapy on detection of invasive pulmonary aspergillosis

Interest in lateral-flow devices (LFDs) as potential point-of-care assays for the diagnosis of infectious diseases has increased. Our objective was to evaluate the interlaboratory and interstudy reproducibility and the effects of antifungal therapy on an LFD developed for invasive pulmonary aspergillosis (IPA) detection. An established neutropenic guinea pig model of IPA caused by Aspergillus fumigatus was used. At predetermined time points (1 h and 3, 5, and 7 days postinoculation), blood and bronchoalveolar lavage (BAL) fluid were collected from infected and uninfected animals. In a separate experiment, guinea pigs were treated with posaconazole (10 mg/kg of body weight orally [p.o.] twice a day [BID]), voriconazole (10 mg/kg p.o. BID), liposomal amphotericin B (10 mg/kg intraperitoneally [i.p.] once a day [QD]), or caspofungin (2 mg/kg i.p. QD), and samples were collected on days 7 and 11. Each laboratory independently evaluated the IgG monoclonal antibody-based LFD. Galactomannan and (1 → 3)-β-D-glucan were also measured using commercially available kits. Good interlaboratory agreement was observed with the LFD, as the results for 97% (32/33) of the serum and 78.8% (26/33) of the BAL fluid samples from infected animals were in agreement. Good interstudy agreement was also observed. The serum sensitivity of each surrogate-marker assay was reduced in animals treated with antifungals. In contrast, these markers remained elevated within the BAL fluids of treated animals, which was consistent with the fungal burden and histopathology results. These results demonstrate that the LFD assay is reproducible between different laboratories and studies. However, the sensitivity of this assay and other markers of IPA may be reduced with serum in the presence of antifungal therapy.

Method for recovery and immunoaffinity enrichment of membrane proteins illustrated with metastatic ovarian cancer tissues

Integral membrane proteins play key biological roles in cell signaling, transport, and pathogen invasion. However, quantitative clinical assays for this critical class of proteins remain elusive and are generally limited to serum-soluble extracellular fragments. Furthermore, classic proteomic approaches to membrane protein analysis typically involve proteolytic digestion of the soluble pieces, resulting in separation of intra- and extracellular segments and significant informational loss. In this paper, we describe the development of a new method for the quantitative extraction of intact integral membrane proteins (including GPCRs) from solid metastatic ovarian tumors using pressure cycling technology in combination with a new (ProteoSolve-TD) buffer system. This new extraction buffer is compatible with immunoaffinity methods (e.g., ELISA and immunoaffinity chromatography), as well as conventional proteomic techniques (e.g., 2D gels, western blots). We demonstrate near quantitative recovery of membrane proteins EDG2, EDG4, FASLG, KDR, and LAMP-3 by western blots. We have also adapted commercial ELISAs for serum-soluble membrane protein fragments (e.g., sVEGFR2) to measure the tissue titers of their transmembrane progenitors. Finally, we demonstrate the compatibility of the new buffers with immunoaffinity enrichment/mass spectrometric characterization of tissue proteins.

Detection of invasive pulmonary aspergillosis in haematological malignancy patients by using lateral-flow technology

Invasive pulmonary aspergillosis (IPA) is a leading cause of morbidity and mortality in haematological malignancy patients and hematopoietic stem cell transplant recipients¹. Detection of IPA represents a formidable diagnostic challenge and, in the absence of a 'gold standard', relies on a combination of clinical data and microbiology and histopathology where feasible. Diagnosis of IPA must conform to the European Organization for Research and Treatment of Cancer and the National Institute of Allergy and Infectious Diseases Mycology Study Group (EORTC/MSG) consensus defining "proven", "probable", and "possible" invasive fungal diseases². Currently, no nucleic acid-based tests have been externally validated for IPA detection and so polymerase chain reaction (PCR) is not included in current EORTC/MSG diagnostic criteria.

Identification of Aspergillus in histological sections is problematic because of similarities in hyphal morphologies with other invasive fungal pathogens³, and proven identification requires isolation of the etiologic agent in pure culture. Culture-based approaches rely on the availability of biopsy samples, but these are not always accessible in sick patients, and do not always yield viable propagules for culture when obtained.

An important feature in the pathogenesis of Aspergillus is angio-invasion, a trait that provides opportunities to track the fungus immunologically using tests that detect characteristic antigenic signatures molecules in serum and bronchoalveolar lavage (BAL) fluids. This has led to the development of the Platelia enzyme immunoassay (GM-EIA) that detects Aspergillus galactomannan and a 'pan-fungal' assay (Fungitell test) that detects the conserved fungal cell wall component (1 →3)-β-D-glucan, but not in the mucorales that lack this component in their cell walls^1,4. Issues surrounding the accuracy of these tests^1,4-6 has led to the recent development of next-generation monoclonal antibody (MAb)-based assays that detect surrogate markers of infection^1,5.

Thornton⁵ recently described the generation of an Aspergillus-specific MAb (JF5) using hybridoma technology and its use to develop an immuno-chromatographic lateral-flow device (LFD) for the point-of-care (POC) diagnosis of IPA. A major advantage of the LFD is its ability to detect activity since MAb JF5 binds to an extracellular glycoprotein antigen that is secreted during active growth of the fungus only⁵. This is an important consideration when using fluids such as lung BAL for diagnosing IPA since Aspergillus spores are a common component of inhaled air. The utility of the device in diagnosing IPA has been demonstrated using an animal model of infection, where the LFD displayed improved sensitivity and specificity compared to the Platelia GM and Fungitell (1 → 3)-β-D-glucan assays⁷.

Here, we present a simple LFD procedure to detect Aspergillus antigen in human serum and BAL fluids. Its speed and accuracy provides a novel adjunct point-of-care test for diagnosis of IPA in haematological malignancy patients.

Development of an antigen-based rapid diagnostic test for the identification of blowfly (Calliphoridae) species of forensic significance

In this study we examine the limitations of currently used sequence-based approaches to blowfly (Calliphoridae) identification and evaluate the utility of an immunological approach to discriminate between blowfly species of forensic importance. By investigating antigenic similarity and dissimilarity between the first instar larval stages of four forensically important blowfly species, we have been able to identify immunoreactive proteins of potential use in the development of species-specific immuno-diagnostic tests. Here we outline our protein-based approach to species determination, and describe how it may be adapted to develop rapid diagnostic assays for the 'on-site' identification of blowfly species.

Plastid transformation of high-biomass tobacco variety Maryland Mammoth for production of human immunodeficiency virus type 1 (HIV-1) p24 antigen

Chloroplast transformation of the high-biomass tobacco variety Maryland Mammoth has been assessed as a production platform for the human immunodeficiency virus type 1 (HIV-1) p24 antigen. Maryland Mammoth offers the prospect of higher yields of intact functional protein per unit floor area of contained glasshouse per unit time prior to flowering. Two different transformation constructs, pZSJH1p24 (for the insertion of a native p24 cDNA between the rbcL and accD genes) and pZF5 (for the insertion of a chloroplast-codon-optimized p24 gene between trnfM and trnG) were examined for the production of p24. Plants generated with construct pZSJH1p24 exhibited a normal green phenotype, but p24 protein accumulated only in the youngest leaves (up to approximately 350 microg/g fresh weight or approximately 2.5% total soluble protein) and was undetectable in mature leaves. In contrast, some of the plants generated with pZF5 exhibited a yellow phenotype (pZF5-yellow) with detectable p24 accumulation (up to approximately 450 microg/g fresh weight or approximately 4.5% total soluble protein) in all leaves, regardless of age. Total protein in pZF5-yellow leaves was reduced by approximately 40%. The pZF5-yellow phenotype was associated with recombination between native and introduced direct repeat sequences of the rbcL 3' untransformed region in the plastid genome. Chloroplast-expressed p24 was recognized by a conformation-dependent monoclonal antibody to p24, and p24 protein could be purified from pZF5-yellow leaves using a simple procedure, involving ammonium sulphate precipitation and ion-exchange chromatography, without the use of an affinity tag. The purified p24 was shown to be full length with no modifications, such as glycosylation or phosphorylation, using N-terminal sequencing and mass spectrometry.

Rapid detection of HIV-1 by reverse-transcription, loop-mediated isothermal amplification (RT-LAMP)

A rapid, cost-effective diagnostic or confirmatory test for the detection of early HIV-1 infection is highly desired, especially for use in resource-poor or point-of-care settings. The reverse-transcription loop-mediated isothermal amplification (RT-LAMP) technology has been evaluated for the detection of HIV-1 DNA and RNA, using six RT-LAMP primers designed against highly conserved sequences located within the protease and p24 gene regions. Amplification from lab-adapted HIV-1 DNA and RNA was detected as early as 30 min, with maximum sensitivity of 10 and 100 copies per reaction, respectively, reached at 60 min. Comparable sensitivity was observed with extracted nucleic acid from plasma and blood samples of HIV-1-infected individuals. Furthermore, the RT-LAMP procedure was modified for the direct detection of HIV-1 nucleic acid in plasma and blood samples, eliminating the need for an additional nucleic acid extraction step and reducing the overall procedure time to approximately 90 min.

Development of an immunochromatographic lateral-flow device for rapid serodiagnosis of invasive aspergillosis

Aspergillus fumigatus is a cosmopolitan saprotrophic fungus that is second only to Candida species as a cause of invasive fungal infections in immunocompromised humans. Current immunodiagnostic tests for invasive aspergillosis (IA) are based on the detection of circulating galactomannan (GM) in a patient's serum by using a rat monoclonal antibody (MAb), EB-A2, that binds to tetra (1-->5)-beta-D-galactofuranoside, the immunodominant epitope in GM. The potential cross-reactivity of MAb EB-A2 with non-Aspergillus fungi, with contaminating GM in beta-lactam antibiotics and foodstuffs, and with bacterial lipoteichoic acids has prompted efforts to discover non-GM antigens that can act as surrogate markers for the diagnosis of IA. This paper describes the development of a mouse MAb, JF5, that binds to a protein epitope present on an extracellular glycoprotein antigen secreted constitutively during the active growth of A. fumigatus. The MAb was used to develop an immunochromatographic lateral-flow device (LFD) for the rapid (15-min) detection of Aspergillus antigens in human serum. The test is highly specific, reacting with antigens from Aspergillus species but not with antigens from a large number of clinically important fungi, including Candida species, Cryptococcus neoformans, Fusarium solani, Penicillium marneffei, Pseudallescheria boydii, and Rhizopus oryzae. The LFD was able to detect circulating antigen in serum samples from patients suspected of having or shown to have IA on the basis of their clinical symptoms and results from tests for GM and fungal (1-->3)-beta-D-glucan. The ease of use of the LFD provides a diagnostic platform for the routine testing of vulnerable patients who have an elevated risk of IA.

Selection and characterization of scFv antibodies against the Sin Nombre hantavirus nucleocapsid protein

Rodent-borne hantaviruses cause hemorrhagic fever with renal syndrome (HFRS) in the old world and hantavirus cardio-pulmonary syndrome (HCPS) in the new. Most cases of HCPS in North America are caused by Sin Nombre Virus (SNV). Current viral detection technologies depend upon the identification of anti-viral antibodies in patient serum. Detection of viral antigen may facilitate earlier detection of the pathogen. We describe here the characterization of two single-chain Fv antibodies (scFvs), selected from a large naïve phage antibody library, which are capable of identifying the Sin Nombre Virus nucleocapsid protein (SNV-N), with no cross reactivity with the nucleocapsid protein from other hantaviruses. The utility of such selected scFvs was increased by the creation of an scFv-alkaline phosphatase fusion protein which was able to directly detect virally produced material without the need for additional reagents.

The antigenic determinants on HIV p24 for CD4+ T cell inhibiting antibodies as determined by limited proteolysis, chemical modification, and mass spectrometry

In the last decade, mass spectrometry has been employed by more and more researchers for identifying the proteins in a macromolecular complex as well as for defining the surfaces of their binding interfaces. This characterization of protein-protein interfaces usually involves at least one of several different methodologies in addition to the actual mass spectrometry. For example, limited proteolysis is often used as a first step in defining regions of a protein that are protected from proteolysis when the protein of interest is part of a macromolecular complex. Other techniques used in conjunction with mass spectrometry for determining regions of a protein involved in protein-protein interactions include chemical modification, such as covalent cross-linking, acetylation of lysines, hydrogen-deuterium exchange, or other forms of modification. In this report, both limited proteolysis and chemical modification were combined with several mass spectrometric techniques in efforts to define the protein surface on the HIV core protein, p24, recognized by two different monoclonal human antibodies that were isolated from HIV+ patients. One of these antibodies, 1571, strongly inhibits the CD4+ T cell proliferative response to a known epitope (PEVIPMFSALSEGATP), while the other antibody, 241-D, does not inhibit as strongly. The epitopes for both of these antibodies were determined to be discontinuous and localized to the N-terminus of p24. Interestingly, the epitope recognized by the strongly inhibiting antibody, 1571, completely overlaps the T cell epitope PEVIPMFSALSEGATP, while the antibody 241-D binds to a region adjacent to the region of p24 recognized by the antibody 1571. These results suggest that, possibly due to epitope competition, antibodies produced during HIV infection can negatively affect CD4+ T cell-mediated immunity against the virus.