Combination assay detecting both human immunodeficiency virus (HIV) p24 antigen and anti-HIV antibodies opens a second diagnostic window

HIV-1 Capsid Uncoating Is a Multistep Process That Proceeds through Defect Formation Followed by Disassembly of the Capsid Lattice

The HIV-1 core consists of a cone-shaped capsid shell made of capsid protein (CA) hexamers and pentamers encapsulating the viral genome. HIV-1 capsid disassembly, referred to as uncoating, is important for productive infection; however, the location, timing, and regulation of uncoating remain controversial. Here, we employ amber codon suppression to directly label CA. In addition, a fluid phase fluorescent probe is incorporated into the viral core to detect small defects in the capsid lattice. This double-labeling strategy enables the visualization of uncoating of single cores in vitro and in living cells, which we found to always proceed through at least two distinct steps─the formation of a defect in the capsid lattice that initiates gradual loss of CA below a detectable level. Importantly, intact cores containing the fluid phase and CA fluorescent markers enter and uncoat in the nucleus, as evidenced by a sequential loss of both markers, prior to establishing productive infection. This two-step uncoating process is observed in different cells, including a macrophage line. Notably, the lag between the release of fluid phase marker and terminal loss of CA appears to be independent of the cell type or reverse transcription and is much longer (>5-fold) for nuclear capsids compared to cell-free cores or cores in the cytosol, suggesting that the capsid lattice is stabilized by capsid-binding nuclear factors. Our results imply that intact HIV-1 cores enter the cell nucleus and that uncoating is initiated through a localized defect in the capsid lattice prior to a global loss of CA.

High-Throughput NanoBiT-Based Screening for Inhibitors of HIV-1 Vpu and Host BST-2 Protein Interaction

Bone marrow stromal cell antigen 2 (BST-2), also known as CD317 or tetherin, has been identified as a host restriction factor that suppresses the release of enveloped viruses from host cells by physically tethering viral particles to the cell surface; however, this host defense can be subverted by multiple viruses. For example, human immunodeficiency virus (HIV)-1 encodes a specific accessory protein, viral protein U (Vpu), to counteract BST-2 by binding to it and directing its lysosomal degradation. Thus, blocking the interaction between Vpu and BST-2 will provide a promising strategy for anti-HIV therapy. Here, we report a NanoLuc Binary Technology (NanoBiT)-based high-throughput screening assay to detect inhibitors that disrupt the Vpu-BST-2 interaction. Out of more than 1000 compounds screened, four inhibitors were identified with strong activity at nontoxic concentrations. In subsequent cell-based BST-2 degradation assays, inhibitor Y-39983 HCl restored the cell-surface and total cellular level of BST-2 in the presence of Vpu. Furthermore, the Vpu-mediated enhancement of pesudotyped viral particle production was inhibited by Y-39983 HCl. Our findings indicate that our newly developed assay can be used for the discovery of potential antiviral molecules with novel mechanisms of action.

Evaluation of HIV-1 Regulatory and Structural Proteins as Antigen Candidate in Mice and Humans

BACKGROUND

The diagnosis of HIV infection is important among different groups. Moreover, combination antiretroviral therapy is used to treat HIV-1, but it cannot eradicate the infection. Thus, the development of therapeutic vaccines, along with antiretroviral therapy, is recommended. This study evaluates the values of four HIV proteins as antigen candidates in therapeutic vaccine design as well as a possible diagnostic marker for HIV infection in humans.

METHODS

In this study, the HIV-1 Tat and Rev regulatory proteins and structural Gp120 and p24 proteins were generated in E. coli expression system. Their immunogenicity was evaluated in BALB/ c mice using homologous and heterologous prime/boost strategies. Moreover, the detection of anti- HIV IgG antibodies against these recombinant proteins was assessed in untreated (Naïve/ HIV-infected), treated, and drug-resistant patients compared to the healthy (control) group as a possible diagnostic marker for HIV infection.

RESULTS

In humans, our results showed that among HIV-1 proteins, anti-Gp120 antibody was not detected in treated individuals compared to the healthy (control) group. The levels of anti-Gp120 antibody were significantly different between the treated group and Naïve as well as drug-resistant subjects. Moreover, the level of anti-p24 antibody was significantly lower in the treated group than the Naive group. In mice, the results of immunization indicated that the Rev antigen could significantly induce IgG2a, IgG2b, and IFN-γ secretion aimed at Th1 response as well as Granzyme B generation as CTL activity in comparison with other antigens. Furthermore, the heterologous DNA prime/ protein boost regimen was more potent than the homologous regimen for stimulation of cellular immunity.

CONCLUSION

Briefly, the levels of both anti-Gp120 and anti-p24 antibodies can be considered for the diagnosis of the HIV-infected individuals in different groups compared to the healthy group. Moreover, among four recombinant proteins, Rev elicited Th1 cellular immunity and CTL activity in mice as an antigen candidate in therapeutic vaccine development.

Efficacy of early antiretroviral therapy 36 hours after HIV infection in one blood donor

BACKGROUND

Discrepancies can occur with the use of clinical human immunodeficiency virus (HIV) diagnostic reagents for the HIV window period (WP; time from RNA to antibody detection by diagnostic or blood screening assays). Antiretroviral therapy (ART) during acute HIV infection can impact HIV-specific antibodies, antigens, and DNA/RNA detection. In this study, an HIV WP blood donor who initiated ART was monitored, evaluating the immunological and nucleic acid testing (NAT) results for early ART and discussing the potential effects on blood safety.

STUDY DESIGN AND METHODS

This was a follow-up study of a HIV WP donor detected 36 hours after high-risk sexual behavior, who was subsequently treated with ART. Immunological and NAT methods were comparatively analyzed.

RESULTS

The 4th generation HIV serologic assays were positive at Day 11, and the 3rd generation domestic anti-HIV assay was positive at Day 33. Individual donation (ID) NAT and minipool (MP) NAT of six samples were reactive, but 12-sample MP-NAT was nonreactive. ART resulted in a slow decline of HIV RNA, but HIV DNA was still detected on Day 757.

CONCLUSION

After ART, ID-NAT was more sensitive than MP-NAT or serologic detection; however, HIV DNA detection was more sensitive, with DNA but not RNA persistently detectable.

Rapid HIV Antigen-Antibody Assays and Detection of Acute HIV Infection in Sub-Saharan Africa

Detection of acute HIV infection is a unique problem that fourth-generation HIV assays were expected to alleviate. In this commentary, we draw attention to the limitations and challenges with use of currently available rapid antigen-antibody (Ag/Ab) combination tests for detection of acute HIV infection in sub-Saharan Africa. Laboratory-based HIV-1 Ag/Ab immunoassays are complex, requiring specialized equipment and handling that are currently not affordable in many settings in Africa. The point-of-care Ag/Ab platform on the other hand is easier to deploy and potentially more accessible in resource-limited settings. However, available fourth-generation HIV-1 rapid diagnostic tests have demonstrated poor performance characteristics in field studies where non-B subtypes of HIV-1 dominate. The potential for point-of-care HIV-1 Ag/Ab diagnostics to significantly improve detection of acute HIV infection remains yet to be realized in sub-Saharan Africa. Assay platforms need to be optimized to identify local circulating subtypes, and optimal algorithms need to be determined.

Acute HIV Infection in a Patient with Repeat HIV Antibody/Antigen Negative Results Presenting at an Urban Emergency Department: A Case Report

BACKGROUND

It is not uncommon for patients with human immunodeficiency virus (HIV) infections to visit the emergency department (ED) during seroconversion. However, patients with newly acquired HIV may not have a reactive screening result. We report a case of a patient who initially screened reactive on a fourth generation HIV test and subsequently nonreactive twice, but ultimately had positive viral load tests.

CASE REPORT

A 41-year-old woman experiencing symptoms of a sore throat, odynophagia, and back and flank pain for 5 days presented to the ED. The patient had a reactive HIV screen but negative confirmatory antibody test. The ED provider ordered a HIV viral load, informed the patient, and discharged with oral antibacterial agent. The patient returned the next day and after review of Visit 1 results, the ED provider ordered a second HIV screen, which had a nonreactive result. Another HIV viral load order was placed. The patient was discharged and returned a third time, 4 days after initial presentation. On this visit she was admitted, and the initial HIV viral load result returned positive. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: We report a case of a patient who initially screened reactive on a fourth generation HIV screening and then twice nonreactive on the same screening test, ultimately having positive viral loads. The most probable explanation for her series of atypical HIV results is that the patient presented during the p24 seroconversion window, which is graphically conveyed in Figure 1. If her first screening had been performed during the window, no further test would have been performed to rule out HIV, contributing to misdiagnosis. ED providers need to be aware that, at some time points during seroconversion from "negative" to "positive", patients recently infected with HIV and manifesting prodromal symptoms may nonetheless have a negative screening result.

Development of a new recombinant p24 ELISA system for diagnosis of bovine leukemia virus in serum and milk

Bovine leukemia virus (BLV) is a retrovirus that causes enzootic bovine leucosis. Here, we designed a p24 enzyme-linked immunosorbent assay (ELISA) to detect antibodies specific for BLV capsid protein p24 (encoded by the gag gene) in bovine serum samples. The p24 gene was inserted into an Escherichia coli expression system, and recombinant proteins (GST-p24, p24, and His-p24) were purified. His-p24 was the most suitable antigen for using in the ELISA. The cut-off point was calculated from a receiver operating characteristic curve derived from a set of 582 field samples that previously tested positive or negative by BLV-CoCoMo-qPCR-2, which detects BLV provirus. The new p24 ELISA showed almost the same specificity and sensitivity as a commercial gp51 ELISA kit when used to test field serum samples, and allowed monitoring of p24 antibodies in raw milk and whey. Comparing the results for the p24 ELISA and gp51 ELISA revealed that p24 antibodies were detected earlier than gp51 antibodies in three out of eight calves experimentally infected with BLV, indicating improved detection without diminishing BLV serodiagnosis. Thus, the p24 ELISA is a robust and reliable assay for detecting BLV antibodies in serum or milk, making it is a useful tool for large-scale BLV screening.

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.

Developments in the Diagnostic Techniques of Infectious Diseases: Rural and Urban Prospective

Objectives:

Diagnostics is the first step for the treatment and eradication of infectious microbial diseases. Due to ever evolving pathogens and emerging new diseases, there is an urgent need to identify suitable diagnostic techniques for better management of each disease. The success rate of specific diagnostic technique in any population depends on various factors including type of the microbial pathogen, availability of resources, technical expertise, disease severity and degree of epidemic of disease in the area. One of the important tasks of the policy makers is to identify and implement suitable diagnostic techniques for specific regions based on their specific requirements. In this review we have discussed various techniques available in the literature and their suitability for the target population based on above mentioned criteria.

Methods:

Diagnostic techniques evaluation of well documented representative microbial diseases; Tuberculosis (bacterial), Malaria (parasitic) and HIV (viral) were included in the study. Identification and collection of information and data was performed focusing on the diagnostic techniques used from the scientific publications from Pubmed, Science Access, Scopus, EMBASE and several regional databases. WHO and CDC database for Tuberculosis, Malaria and HIV were also included. These techniques were compared with respect to the financial resource availability, expertise and management, functional capacity, pathogen virulence and degree of epidemic in the population.

Results and Conclusion:

In case of Tuberculosis, ELISA and colorimetric techniques are successful in rural and urban communities with 80% – 90% sensitivity. Genotyping and SNP analysis are useful in drug resistant strains. Parasitic disease Malaria also follows the same trend with diagnostic techniques like RDTs being common in both population with fast results and around 90% sensitivity. STD disease like HIV however shows slight different trends due to urgent need of interference in rural epidemics of the disease. Rapid and sensitive immunotechniques like dipsticks and agglutination with almost 100% sensitivity are used in both rural and urban areas. For the confirmation further tests are done like protein Western and NAAT. Advance techniques could be the option for higher epidemic area, drug resistance and disease research, while rapid techniques would be suitable for low income areas and POC facilities. Therefore, suitability of the diagnostic techniques for better management depends not only on the financial resources and assessment skills of a community but sometimes on the disease itself. We have further discussed the technological improvements for specific settings (rural/urban) based on the past research for better management of diseases, which could be implemented for the understanding of understudied and newly emerging diseases.

Comparative evaluation of three FDA-approved HIV Ag/Ab combination tests using a genetically diverse HIV panel and diagnostic specimens

BACKGROUND

HIV Ag/Ab combination assays are recommended by CDC for routine screening and several HIV Ag/Ab combination tests are now FDA-approved. Maintaining high specificity and consistent sensitivity across diverse HIV strains is critical for these assays to accurately detect HIV infection and expedite delivery of patient results.

OBJECTIVES

To evaluate performance of three FDA-approved HIV tests: ARCHITECT HIV Combo (Abbott), ADVIA Centaur HIV Combo (Siemens) and BioPlex HIV Ag-Ab (Bio-Rad).

STUDY DESIGN

Sensitivity and specificity were evaluated using an extensive panel of 28 HIV infected human specimens and 17 cultured virus isolates representing multiple genotypes, 6 seroconversion panels, 4 human samples with acute infection, WHO p24 standard and 4020 clinical specimens.

RESULTS

The p24 limit of detection (LOD) for the WHO standard was 0.19IU/ml, 0.70IU/ml, and 1.77IU/ml in BioPlex, ARCHITECT, and Centaur respectively. The distribution of LODs across 15 HIV-1 isolates was substantially narrower in ARCHITECT (5-33pg/ml) than in BioPlex (11-198pg/ml) and Centaur (6-384pg/ml). All assays detected antibodies to the majority of HIV-1 and HIV-2 variants. However, reduced sensitivity was observed for Centaur in detection of antibodies to HIV-1 group M (CRF02_AG), O and N variants. BioPlex and ARCHITECT showed better seroconversion sensitivity than Centaur, detecting one bleed (3-7 days) earlier in 4 (BioPlex) and 3 (ARCHITECT) of 6 seroconversion panels. ARCHITECT demonstrated the highest specificity (99.90-100%) compared to BioPlex (99.80%) and Centaur (99.42%).

CONCLUSIONS

The overall performance of ARCHITECT and BioPlex was superior to Centaur, especially for detection of acute HIV infection.

Current diagnostic methods for HIV

Detection of HIV infection is essential for diagnosis and monitoring of the infection. There are different types of diagnostic tools available that are based on detection of HIV-specific antibodies, viral antigen or nucleic acid. Sensitivities and specificities of assays utilized for HIV detection have improved. Newer HIV testing technologies such as third-generation enzyme immunoassay which detect HIV-specific IgG and IgM antibodies, fourth-generation enzyme immunoassay which detect both anti-HIV antibodies and HIV p24 antigen and nucleic acid based tests for HIV RNA have significantly decreased the window period. This review provides an overview of current technologies for the detection and monitoring of HIV infection and recent advances in the field of HIV diagnosis.

Advances in nanomaterials and their applications in point of care (POC) devices for the diagnosis of infectious diseases

Nanotechnology has gained much attention over the last decades, as it offers unique opportunities for the advancement of the next generation of sensing tools. Point-of-care (POC) devices for the selective detection of biomolecules using engineered nanoparticles have become a main research thrust in the diagnostic field. This review presents an overview on how the POC-associated nanotechnology, currently applied for the identification of nucleic acids, proteins and antibodies, might be further exploited for the detection of infectious pathogens: although still premature, future integrations of nanoparticles with biological markers that target specific microorganisms will enable timely therapeutic intervention against life-threatening infectious diseases.

The Performance of the Abbott i2000 for Measuring Serum Markers of Infectious Diseases

BACKGROUND

To date, there is a trend that the chemiluminescent microparticle immunoassays (CMIA) and electrochemiluminescence immunoassays (ECIA) technology gradually replacing the enzyme-linked immunosorbent assay (ELISA). But the performance such as the limit of quantitation (LOQ), precision, linear range of CMIA, or ECIA for serum markers of infectious diseases has rarely been reported.

METHODS

Using proficiency testing samples and standard materials, we confirmed the LOQ of the ELISA and the precision, linear range, LOQ, and instrument biases of the Abbott i2000 for eight serum markers. We used the Abbott i2000 and ELISAs to assess five HIV samples; the researchers were blinded to the true status of the samples.

RESULTS

For the Abbott i2000, the coefficients of variation (CV) for the low, medium, and high concentration samples ranged from 1.06 to 12.74%, which were less than the allowable error; the linear ranges of HBsAg and HBsAb were 0.66-304.11 IU/ml and 8.16-1205.9 mIU/ml, respectively. For the Abbott i2000, the LOQs of HBsAg, HBsAb, HBeAg, HBeAb, HBcAb, anti-HCV, anti-TP, and anti-HIV were 0.026 IU/ml, 4 mIU/ml, 0.14 NCU/ml, 0.56 NCU/ml, 0.99 NCU/ml, 0.5 NCU/ml, 8.8 mIU/ml, and 1.92 NCU/ml, respectively, and these values were 0.16 IU/ml, 6.97 mIU/ml, 1.16 NCU/ml, 1.63 NCU/ml, 1.79 NCU/ml, 1.03 NCU/ml, 8.33 mIU/ml, and 1.3 NCU/ml, respectively, for the ELISA. When five HIV samples were blindly assessed, two cases were missed by the Abbott i2000 and the ELISA results were consistent with the expected results.

CONCLUSIONS

The Abbott i2000 performed significantly better than the ELISA on HBV and HCV screening; however, for anti-TP and anti-HIV, the ELISA remained the preferred method.

[Performance Assessment of a Newly Developed Rapid Diagnostic Reagent for Human Immunodeficiency Virus]

Extremely early diagnosis of human immunodeficiency virus (HIV) infection has been considered highly important for its treatment. We conducted a performance assessment of a newly developed rapid diagnostic reagent for HIV by using a fourth-generation immunochromatographic assay (Alere HIV Combo). We used whole-blood, plasma, and serum samples obtained from 250 Japanese adults who visited the Kawasaki Medical School Hospital and underwent HIV screening tests. We also used 12 types of commercial HIV-1 sero- conversion panels and World Health Organization standard antigens. This method, which has a detection sensitivity of 100% and a specificity of 99.3%, was as accurate as the chemiluminescent immunoassay (CLIA) method. In a sensitivity test using seroconversion panels in the early phase of infection, the mean duration until positive conversion was 19.3 days. With this method having a high detection sensitivity for HIV-1p24 antigen, the results from whole-blood samples were the same as those from plasma and serum samples. Therefore, it can be considered as a useful rapid measurement method for general practice.

Increased Sensitivity of HIV-1 p24 ELISA Using a Photochemical Signal Amplification System

BACKGROUND

In this study we describe a photochemical signal amplification method (PSAM) for increasing of the sensitivity of enzyme-linked immunosorbent assay (ELISA) for determination of HIV-1 p24 antigen. The photochemical signal amplification method is based on an autocatalytic photochemical reaction of a horseradish peroxidase (HRP) substrate, orthophenylenediamine (OPD).

METHODS

To compare the performance of PSAM-boosted ELISA with a conventional colorimetric ELISA for determination of HIV-1 p24 antigen we employed a PerkinElmer HIV-1 p24 ELISA kit, using conventional ELISA alongside ELISA + PSAM.

RESULTS

In the present study, we show that PSAM technology allows one to increase the analytical sensitivity and dynamic range of a commercial HIV-1 p24 ELISA kit, with and without immune-complex disruption, by a factor of approximately 40-fold.

CONCLUSIONS

ELISA + PSAM is compatible with commercially available microtiter plate readers, requires only an inexpensive illumination device, and the PSAM amplification step takes no longer than 15 min. This method can be used for both commercially available and in-house ELISA tests, and has the advantage of being considerably simpler and less costly than alternative signal amplification methods. This method can be used for both commercially available and in-house ELISA tests, and has the advantage of being considerably simpler and less costly than alternative signal amplification methods.

Prolonged second diagnostic window for human immunodeficiency virus type 1 in a fourth-generation immunoassay: are alternative testing strategies required?

Diagnosis of acute HIV is done by patient history and examination and testing of RNA, proviral DNA, and serology using fourth-generation antigen/antibody detection assays. We describe an HIV-1 primary infection with a second diagnostic window of 18 to 34 days on a fourth-generation immunoassay, which would have been missed using some current algorithms. Caution must be exercised when fourth-generation HIV-1 immunoassays are interpreted in isolation, and additional testing should be considered depending on patient risk assessment.

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.

Performances of four fourth-generation human immunodeficiency virus-1 screening assays

Fourth-generation human immunodeficiency virus-1 (HIV-1) screening assays have improved sensitivity, but vary in performance characteristics. The purpose of this study was to evaluate four different fourth-generation HIV-1 assays. These assays included the AxSYM HIV Ag/Ab Combo (Abbott diagnostics, Delkenheim, Germany), ARCHITECT HIV Ag/Ab Combo (Abbott), Elecsys 2010 HIV Combi (Roche Diagnostics GmbH, Mannheim, Germany), and Elecsys HIV Combi PT (Roche). A total of 1,306 samples that included 1,225 clinical samples and 81 samples consisting of seroconversion panels, an HIV-1 p24 antigen sensitivity panel, and dilution series of HIV-1 lysates and HIV-1 antibodies were tested. All of the assays had sensitivities of 100% on clinical samples. The specificities of the AxSYM, ARCHITECT, Elecsys 2010 HIV Combi, and Elecsys HIV Combi PT were 99.6, 99.6, 99.0, and 99.5%, respectively. Of the 81 samples with different levels of HIV antigen or antibody and/or subtypes, Elecsys HIV Combi PT and ARCHITECT HIV Ag/Ab Combo showed better analytical sensitivities than the other two assays. In summary, the performance characteristics of AxSYM, ARCHITECT, and Elecsys HIV Combi PT were comparable and satisfactory for clinical samples. ARCHITECT HIV Ag/Ab Combo and Elecsys HIV Combi PT have the higher analytical sensitivities, and would be preferable for reducing the window period.

Real-life evaluation of a human immunodeficiency virus screening algorithm using a single combined p24 antigen-antibody assay

Since May 2010, human immunodeficiency virus (HIV) screening in France has been performed using a single combined fourth-generation assay. One of our major concerns is to verify that this screening strategy is able to diagnose HIV primary infection as soon as possible. Thus, the sensitivity and specificity of this strategy were evaluated on 49,623 serum samples, including 29 primary infections, received for routine HIV testing between September 2010 and November 2011. Specimens were screened using the Enzygnost HIV Integral II enzyme-linked immunosorbent assay (ELISA) kit. All positive sera, according to the manufacturer's recommendations [signal-to-cutoff ratio (S/CO) ≥  1] were retested using the Architect HIV Ag/Ab Combo. Moreover, we defined a grey zone (0.5 < S/CO < 1) and sera within this grey zone were retested using the VIDAS HIV DUO Ultra test and HIV-1 RNA was checked by the Abbott RealTime PCR kit. Screening tests were positive for all primary infections. All samples within the grey zone proved VIDAS HIV DUO Ultra and HIV-1 RNA negative. Overall, the ELISA test sensitivity and specificity were 100 and 99.79 %, respectively. The false-positive rate was higher when S/CO was in the low range (1 to 5). Adding a second screening test for positive sera reduced the false-positive rate from 0.20 to 0.02 %. HIV screening with a single combined assay did not miss any documented primary infection during this evaluation period, even without extending the positivity zone.

Performance evaluation of a new fourth-generation HIV combination antigen-antibody assay

Education and diagnostic tests capable of early detection represent our most effective means of preventing transmission of human immunodeficiency virus (HIV). The importance of early detection is underlined by studies demonstrating increased life expectancy following early initiation of antiviral treatment. The Elecsys^® HIV combi PT assay is a fourth-generation antigen–antibody combination assay developed to allow earlier detection of seroconversion, and to have increased sensitivity and improved specificity. We aimed to determine how early the assay could detect infection compared with existing assays; whether all HIV variants could be detected; and the assay’s specificity using samples from blood donors, routine specimens, and patients with potential cross-reacting factors. Samples were identified as positive by the Elecsys^® assay 4.9 days after a positive polymerase chain reaction result (as determined by the panel supplier), which was earlier than the 5.3–7.1 days observed with comparators. The analytical sensitivity of the Elecsys^® HIV combi PT assay for the HIV-1 p24 antigen was 1.05 IU/mL, which compares favorably with the comparator assays. In addition, the Elecsys^® assay identified all screened HIV subtypes and displayed greater sensitivity to HIV-2 homologous antigen and antibodies to HIV-1 E and O and HIV-2 than the other assays. Overall, the specificity of the Elecsys^® assay was 99.88 % using samples from blood donors and 99.81 % when analyzing unselected samples. Potential cross-reacting factors did not interfere with assay performance. The Elecsys^® HIV combi PT assay is a sensitive and specific assay that has been granted the CE mark according to Directive 2009/886/EC.

Better control of early viral replication is associated with slower rate of elicited antiviral antibodies in the detuned enzyme immunoassay during primary HIV-1C infection

BACKGROUND

Estimation of HIV incidence rates is important for timing interventions, planning prevention studies, and monitoring the epidemic. This requires accurate estimation of the "recency period" (also known as the "window period") between seroconversion and achievement of specific detectable levels of anti-HIV antibody titers, such as the standardized optical density (SOD) in the early phase of HIV-1 infection.

METHODS

To obtain a better understanding of interpatient variation of the recency period, prospective measurements of antiviral antibody titers in the early phase of HIV-1 subtype C infection were quantified by Vironostika-LS. Time of seroconversion was estimated by Fiebig staging.

RESULTS

The profiles of SOD values during the first year of infection commonly showed slow initial increase followed by a more rapid increase, although in some patients, SOD values increased rapidly soon after seroconversion. Using an SOD cutoff of 1.0, the average duration of the recency period in subtype C infection in the local epidemic in Botswana was estimated to be 151 days (95% confidence interval: 130 to 172 days) post seroconversion. The recency period was significantly associated (P = 0.007) with the level of viral replication during the first 2-3 months post seroconversion. Reduction of SOD values after initiation of antiretroviral therapy (ART) was a dominant pattern in antiretroviral drug (ARV)-treated subjects.

CONCLUSIONS

Our data suggest that HIV incidence estimation based on sensitive/less sensitive enzyme immunoassay cross-sectional testing could be potentially improved by incorporation of viral load levels at the time of detection of a recent infection.

The risk of a second diagnostic window with 4th generation HIV assays: Two cases

BACKGROUND

Despite the improved sensitivity of the 4th generation combined antigen/antibody HIV assays, detection of HIV in the early phase of an infection may still be ineffective.

OBJECTIVES

Description of two cases that highlight the existence of the "second diagnostic window phase" observed with commonly used sensitive 4th generation HIV assays.

STUDY DESIGN

Samples were screened with different 4th generation HIV assays. HIV infection was confirmed with an HIV I/II antibody assay, a HIV-1 p24 antigen assay, the INNO-LIA HIV I/II Score Line immunoassay and HIV-1 PCR.

RESULTS

In both investigated cases, the limitations of the 4th generation HIV assays within the second diagnostic window were apparent.

CONCLUSIONS

The overall sensitivity of the commercial 4th generation HIV assays is currently higher than the 3rd generation HIV assays. Nevertheless, the rare occurrence of a second diagnostic window with 4th generation HIV assays strongly suggests that the following up testing algorithms need to be adjusted accordingly.

Assessment of the ability of a fourth-generation immunoassay for human immunodeficiency virus (HIV) antibody and p24 antigen to detect both acute and recent HIV infections in a high-risk setting

An immunoassay (IA) that simultaneously detects both antibody to human immunodeficiency virus (HIV) and HIV p24 antigen (Architect HIV Ag/Ab Combo) was evaluated for its ability to detect HIV infection by using a panel of specimens collected from individuals recently infected with HIV type 1 (HIV-1). This IA was found to be capable of detecting the majority (89%) of infections, including 80% of those considered acute infections based on the presence of HIV RNA and the lack of detectable antibody to HIV. Substantial improvements in detection of recent infections by the Architect HIV Ag/Ab Combo relative to previous generations of IAs as well as the capacity to detect acute infections have important implications for HIV prevention strategies.

Viral load and CD4+ T-cell dynamics in primary HIV-1 subtype C infection

BACKGROUND

Most knowledge of primary HIV-1 infection is based on subtype B studies, whereas the evolution of viral parameters in the early phase of HIV-1 subtype C infection is not well characterized.

METHODS

The kinetics of viral RNA, proviral DNA, CD4+ T-cell count, and subsets of CD4+ T cells expressing CCR5 or CXCR4 were characterized in 8 acute and 62 recent subtype C infections over the first year postseroconversion.

RESULTS

The viral RNA peak was 6.25 +/- 0.92 log10 copies per milliliter. After seroconversion, heterogeneity among acute cases was evident by patterns of change in viral load and CD4+ T-cell count over time. The patterns were supported by the rate of viral RNA decline from peak (P = 0.022), viral RNA means (P = 0.005), CD4 levels (P < 0.001), and CD4 decline to 350 (P = 0.011) or 200 (P = 0.046). Proviral DNA had no apparent peak and its mean was 2.59 +/- 0.69 log10 per 106 peripheral blood mononuclear cell. In recent infections, viral RNA set point was 4.00 +/- 0.97 log10 and viral RNA correlated inversely with CD4+ T cells (P < 0.001) and directly with proviral DNA (P < 0.001).

CONCLUSIONS

Distinct patterns of viral RNA evolution may exist shortly after seroconversion in HIV-1 subtype C infection. The study provides better understanding of the early phase of subtype C infection.

Early identification of seronegative human immunodeficiency virus type 1 infection with severe presentation

Specific antibodies against human immunodeficiency virus (HIV), usually used for diagnosis, almost invariably become detectable within 3 months of exposure. We report on a patient whose HIV infection was identified early by a combined antigen/antibody test, but seroconversion did not occur for 7 months, until the implementation of antiretroviral therapy.