Determination of HIV status of infants born to HIV-infected mothers: A review of the diagnostic methods with special focus on the applicability of p24 antigen testing in developing countries

Tethering of the IgG1 Antibody to Amorphous Silica for Immunosensor Development: A Molecular Dynamics Study

A key factor for improving the sensitivity and performance of immunosensors based on mechanical-plasmonic methods is the orientation of the antibody proteins immobilized on the inorganic surface. Although experimental techniques fail to determine surface phenomena at the molecular level, modern simulations open the possibility for improving our understanding of protein-surface interactions. In this work, replica exchange molecular dynamics (REMD) simulations have been used to model the IgG1 protein tethered onto the amorphous silica surface by considering a united-atom model and a relatively large system (2500 nm² surface). Additional molecular dynamics (MD) simulations have been conducted to derive an atomistic model for the amorphous silica surface using the cristobalite crystal structure as a starting point and to examine the structure of the free IgG1 antibody in the solution for comparison when immobilized. Analyses of the trajectories obtained for the tethered IgG1, which was sampled considering 32 different temperatures, have been used to define the geometry of the protein with respect to the inorganic surface. The tilt angle of the protein with respect to the surface plane increases with temperature, the most populated values being 24, 66, and 87° at the lowest (250 K), room (298 K), and the highest (380 K) temperatures. This variation indicates that the importance of protein-surface interactions decreases with increasing temperature. The influence of the surface on the structure of the antibody is very significant in the constant region, which is directly involved in the tethering process, while it is relatively unimportant for the antigen-binding fragments, which are farthest from the surface. These results are expected to contribute to the development of improved mechanical-plasmonic sensor microarrays in the near future.

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.

Early Infant Diagnosis Sample Management in Mashonaland West Province, Zimbabwe, 2017

Background

In 2016, Mashonaland West Province had 7.4% (520) dried blood spot (DBS) samples for early infant diagnosis (EID) rejected by the Zimbabwe National Microbiology Reference Laboratory (NMRL). The samples were suboptimal, delaying treatment initiation for HIV-infected children. EID is the entry point to HIV treatment services in exposed infants. We determined reasons for DBS sample rejections and suggested solutions.

Methods

A cause-effect analysis, modelled on Ishikawa, was used to identify factors impacting DBS sample quality. Interviewer-administered questionnaires and evaluation of sample collection process, using Standard Operating Procedure (SOP) was conducted. Rejected samples were reviewed. Epi Info™ was used to analyze findings.

Results

Eleven (73.3%) facilities did not adhere to SOP and (86.7%) did not evaluate DBS sample quality before sending for testing. Delayed feedback (up to 4 weeks) from NMRL extended EID delay for 14 (93.3%) of the facilities. Of the 53 participants, 62% knew valid sample identification. Insufficient samples resulted in most rejections (77.9%). Lack of training (94.3%) and ineffective supervision (69.8%) were also cited.

Conclusion

Sample rejections could have been averted through SOP adherence. Ineffective supervision, exacerbated by delayed communication of rejections, extended EID delay, disadvantaging potential ART beneficiaries. Following this study, enhanced quality control through perstage evaluations was recommended to enhance DBS sample quality.

Moving forward with treatment options for HIV-infected children

INTRODUCTION

Current international guidelines recommend to treat all HIV-1 infected patients regardless of CD4 cell count. Despite the remarkable worldwide progress for universal access to antiretroviral during the last decade, the pediatric population remains fragile due to lack of randomized studies, inappropriate antiretroviral formulations, adherence difficulties, drug toxicity and development of resistance.

AREAS COVERED

This review summarizes the latest recommendations and advances for the treatment of HIV-infected children and highlights the potential complications of a lifelong antiretroviral treatment initiated early in life.

EXPERT OPINION

International guidelines recommend to start combination antiretroviral therapy (cART) as fast as possible in all children diagnosed with HIV-1. The principal goal is to improve survival and reduce mortality as well as rapidly decrease HIV reservoirs. This remains a challenge in resource-limited settings were diagnostic tools and treatment access may be limited. Different new strategies are in the pipeline such as immunotherapy in combination with very early cART initiation to seek remission or functional cure. For the time being and awaiting for long term remission or cure, there is a need for further pharmacokinetics studies, more pediatric formulations with improved palatability and implementation of randomized trials for the newer antiretroviral drugs.

Adjusting for time-dependent sensitivity in an illness-death model, with application to mother-to-child transmission of HIV

In mother-to-child transmission of HIV, identifying infected infants relies on a diagnostic test with imperfect sensitivity that is administered at scheduled visits. Under this scenario, a participant's true state may be unknown at the start and end times of the study, and the detection of transitions into illness may be delayed or missed altogether. This could lead to biased estimates of the risk of transmission and covariate associations. When a test has imperfect sensitivity, but perfect specificity, the additional uncertainty can be captured as a random variable measuring delay in detection. The cumulative distribution then defines a time-dependent sensitivity function that increases over time. We present a maximum likelihood based illness-death model that accounts for imperfect sensitivity by including the delay as an exponential distribution. We specify transition rates as penalized B-splines to allow for nonhomogeneity of risk and discuss the model under Markov and semi-Markov assumptions. We apply this method to our motivating data set, a study of 1499 mother and infant pairs at three sites in Africa.

Tracking the progress of HIV: the impact of point-of-care tests on antiretroviral therapy

It is now around 30 years since the discovery of HIV, the virus that causes AIDS. More than 70 million people have been infected in that time and around 35 million have died. The majority of those currently living with HIV/AIDS are in low- and middle-income countries, with sub-Saharan Africa bearing a disproportionate burden of the global disease. In high-income countries, the introduction of antiretroviral therapy (ART) has drastically reduced the morbidity and mortality associated with HIV. Patients on ART are now predicted to have near-normal life expectancy and the role of treatment is increasingly recognized in preventing new infections. In low- and middle-income countries, treatment is now more widely available and around half of those who need ART are currently receiving it. Early diagnosis of HIV is essential if ART is to be optimally implemented. Lab-based diagnostics for screening, diagnosis, treatment initiation, and the monitoring of treatment efficacy are critical in managing the disease and reducing the number of new infections each year. The introduction of point-of-care HIV rapid tests has transformed the epidemic, particularly in low- and middle-income countries. For the first time, these point-of-care tests allow for the rapid identification of infected individuals outside the laboratory who can undergo counseling and treatment and, in the case of pregnant women, allow the timely initiation of ART to reduce the risk of vertical transmission. Although survival is markedly improved with ART even in the absence of laboratory monitoring, long-term management of people living with HIV on ART, and their partners, is essential to ensure successful viral suppression. The burden of disease in many resource-poor settings with high HIV prevalence has challenged the ability of local laboratories to effectively monitor those on ART. Diagnostics used to initiate and monitor treatment are now moving out of the laboratory and into the field. These new point-of-care tests for viral load and CD4 are poised to further transform the disease and shift the treatment paradigm in low- and middle-income countries.

Detection of HIV-1 p24 antigen using a simple and highly sensitive chemiluminescence immunoassay

Aim: Our study aimed to improve the p24 antigen assay, which is a well-established and widely adopted method for the early detection of HIV-1 infections, in order to increase its sensitivity and efficiency and reduce its cost if possible. Materials & methods: We tested HIV-1 standard p24-positive samples and an HIV-1 p24 antigen panel using a new luminol-based chemiluminescence immunoassay (CLIA) based on a typical ‘sandwich’ p24 ELISA with two antibodies, but utilizing luminol as the luminescence compound, which is oxidized by hydrogen peroxide in the presence of horseradish peroxidase in an alkaline environment. A standard curve for the p24 antigen CLIA was generated and fitted a third-order polynomial regression model very well. To quantify p24 antigen, we investigated the linear standard curve fitting by measuring and comparing the effective assay range, r2 value and error of each function. Results: The p24 antigen CLIA showed a detection limit of 0.5 pg/ml and a detection range of 0.5–5 × 103 pg/ml. The specificity and sensitivity of this assay were further evaluated, and were both found to be 100% for the HIV-1 p24 antigen panel. The luminescence reaction of the CLIA p24 assay takes only 2 min to perform, which greatly reduced the diagnosis time. Additionally, the CLIA p24 assay is as affordable as the normal ELISA method. Conclusion: In our studies, the p24 antigen CLIA shows improved sensitivity, a wider range of response and was less time-consuming than ELISA, as traditional ELISA uses chromogen or a substrate that changes color when cleaved by the enzyme attached to a second antibody. This seems to be an easy and affordable method for the diagnosis of HIV-1 infection and monitoring of disease progression in developing countries. Although more advantages have been seen in CLIA than in ELISA, additional studies are still needed to confirm this.