Seroconverting blood donors as a resource for characterising and optimising recent infection testing algorithms for incidence estimation

Study design approaches for future active-controlled HIV prevention trials

Objectives

Vigorous discussions are ongoing about future efficacy trial designs of candidate human immunodeficiency virus (HIV) prevention interventions. The study design challenges of HIV prevention interventions are considerable given rapid evolution of the prevention landscape and evidence of multiple modalities of highly effective products; future trials will likely be 'active-controlled', i.e., not include a placebo arm. Thus, novel design approaches are needed to accurately assess new interventions against these highly effective active controls.

Methods

To discuss active control design challenges and identify solutions, an initial virtual workshop series was hosted and supported by the International AIDS Enterprise (October 2020-March 2021). Subsequent symposia discussions continue to advance these efforts. As the non-inferiority design is an important conceptual reference design for guiding active control trials, we adopt several of its principles in our proposed design approaches.

Results

We discuss six potential study design approaches for formally evaluating absolute prevention efficacy given data from an active-controlled HIV prevention trial including using data from: 1) a registrational cohort, 2) recency assays, 3) an external trial placebo arm, 4) a biomarker of HIV incidence/exposure, 5) an anti-retroviral drug concentration as a mediator of prevention efficacy, and 6) immune biomarkers as a mediator of prevention efficacy.

Conclusions

Our understanding of these proposed novel approaches to future trial designs remains incomplete and there are many future statistical research needs. Yet, each of these approaches, within the context of an active-controlled trial, have the potential to yield reliable evidence of efficacy for future biomedical interventions.

Facilitating Next-Generation Pre-Exposure Prophylaxis Clinical Trials Using HIV Recent Infection Assays: A Consensus Statement from the Forum HIV Prevention Trial Design Project

Standard-of-care HIV pre-exposure prophylaxis (PrEP) is highly efficacious, but uptake of and persistence on a daily oral pill is low in many settings. Evaluation of alternate PrEP products will require innovation to avoid the unpractically large sample sizes in noninferiority trials. We propose estimating HIV incidence in people not on PrEP as an external counterfactual to which on-PrEP incidence in trial subjects can be compared. HIV recent infection testing algorithms (RITAs), such as the limiting antigen avidity assay plus viral load used on specimens from untreated HIV positive people identified during screening, is one possible approach. Its feasibility is partly dependent on the sample size needed to ensure adequate power, which is impacted by RITA performance, the number of recent infections identified, the expected efficacy of the intervention, and other factors. Screening sample sizes to support detection of an 80% reduction in incidence for 3 key populations are more modest, and comparable to the number of participants in recent phase III PrEP trials. Sample sizes would be significantly larger in populations with lower incidence, where the false recency rate is higher or if PrEP efficacy is expected to be lower. Our proposed counterfactual approach appears to be feasible, offers high statistical power, and is nearly contemporaneous with the on-PrEP population. It will be important to monitor the performance of this approach during new product development for HIV prevention. If successful, it could be a model for preventive HIV vaccines and prevention of other infectious diseases.

HIV incidence in South African blood donors from 2012 to 2016: a comparison of estimation methods

BACKGROUND

Measuring incidence is important for monitoring and maintaining the safety of the blood supply. Blood collected from repeat-donors has provided the opportunity to follow blood donors over time and has been used to estimate the incidence of viral infections. These incidence estimates have been extrapolated to first-time donors using the ratio of NAT yield cases in first-time versus repeat-donors. We describe a model to estimate incidence in first-time donors using the limiting antigen (LAg) avidity assay and compare its results with those from established models.

METHODS

HIV-positive first-time donations were tested for recency using the LAg assay. Three models were compared; incidence estimated for (1) first-time donors using LAg avidity, (2) first-time and repeat-donors separately using the NAT yield window period (WP) model and (3) repeat-donors using the incidence/WP model.

RESULTS

HIV incidence in first-time donors was estimated at 3·32 (CI 3·11, 3·55) and 3·81 (CI 3·07, 4·73) per 1000 PY using the LAg assay and NAT yield WP models, respectively. Incidence in repeat-donors was between 2·0- and 2·5-fold lower than in first-time donors estimated at 1·56 (CI 1·37, 1·77) and 1·94 (CI 1·86-2·01) per 1000 PY using the NAT yield/WP and incidence/WP models, respectively.

CONCLUSION

Testing HIV-positive donations using the LAg assay provides a reliable method to estimate incidence in first-time donors for countries that collect the majority of blood from first-time donors and do not screen with NAT.

Development of an international external quality assurance program for HIV-1 incidence using the Limiting Antigen Avidity assay

Laboratory assays for identifying recent HIV-1 infections are widely used for estimating incidence in cross-sectional population-level surveys in global HIV-1surveillance. Adequate assay and laboratory performance are required to ensure accurate incidence estimates. The NIAID-supported External Quality Assurance Program Oversight Laboratory (EQAPOL) established a proficiency testing program for the most widely-used incidence assay, the HIV-1 Limiting Antigen Avidity EIA (LAg), with US Centers for Disease Control and Prevention (CDC)-approved kits manufactured by Sedia Biosciences Corporation and Maxim Biomedical. The objective of this program is to monitor the performance of participating laboratories. Four rounds of blinded external proficiency (EP) panels were distributed to up to twenty testing sites (7 North American, 5 African, 4 Asian, 2 South American and 2 European). These panels consisted of ten plasma samples: three blinded well-characterized HIV-1-seropositive samples that were included as replicates and an HIV-negative control. The seropositive samples spanned the dynamic range of the assay and are categorized as either recent or long-term infection. Participating sites performed the assay according to manufacturers’ instructions and completed an online survey to gather information on kit manufacturer, lot of kit used, laboratory procedures and the experience of technicians. On average, fifteen sites participated in each round of testing, with an average of four sites testing with only the Maxim assay, seven testing with only the Sedia assay and five sites utilizing both assays. Overall, the Sedia and Maxim assays yielded similar infection status categorization across the laboratories; however, for most of the nine HIV+ samples tested, there were significant differences in the optical density readouts, ODn (N = 8) and OD (N = 7), between LAg kit manufacturers (p < 0.05 based on mixed effects models. The EQAPOL LAg program is important for monitoring laboratory performance as well as detecting variations between manufacturers of HIV-1incidence assays.

Strengthening HIV surveillance: measurements to track the epidemic in real time

Surveillance for HIV as a public health initiative requires timely, detailed and robust data to systematically understand burden of infection, transmission patterns, direct prevention efforts, guide funding, identify new infections and predict future trends in the epidemic. The methods for HIV surveillance have evolved to reliably track the epidemic and identify new infections in real time. Initially HIV surveillance relied primarily on the reporting of AIDS cases followed by measuring antibodies to HIV to determine prevalence in key populations. With the roll-out of antiretroviral therapy (ART) resulting in better survival and the corresponding increase in HIV prevalence, the landscape of surveillance shifted further to track HIV prevalence and incidence within the context of programmes. Recent developments in laboratory assays that potentially measure and differentiate recent versus established HIV infection offer a cost-effective method for the rapid estimation of HIV incidence. These tests continue to be validated and are increasingly useful in informing the status of the epidemic in real time. Surveillance of heterogeneity of infections contributing to sub-epidemics requires methods to identify affected populations, density, key geographical locations and phylogenetically linked or clustered infections. Such methods could provide a nuanced understanding of the epidemic and prioritise prevention efforts to those most vulnerable. This paper brings together recent developments and challenges facing HIV surveillance, together with the application of newer assays and methods to fast-track the HIV prevention and treatment response.

Using HIV networks to inform real time prevention interventions

Objective

To reconstruct the local HIV-1 transmission network from 1996 to 2011 and use network data to evaluate and guide efforts to interrupt transmission.

Design

HIV-1 pol sequence data were analyzed to infer the local transmission network.

Methods

We analyzed HIV-1 pol sequence data to infer a partial local transmission network among 478 recently HIV-1 infected persons and 170 of their sexual and social contacts in San Diego, California. A transmission network score (TNS) was developed to estimate the risk of HIV transmission from a newly diagnosed individual to a new partner and target prevention interventions.

Results

HIV-1 pol sequences from 339 individuals (52.3%) were highly similar to sequences from at least one other participant (i.e., clustered). A high TNS (top 25%) was significantly correlated with baseline risk behaviors (number of unique sexual partners and insertive unprotected anal intercourse (p = 0.014 and p = 0.0455, respectively) and predicted risk of transmission (p<0.0001). Retrospective analysis of antiretroviral therapy (ART) use, and simulations of ART targeted to individuals with the highest TNS, showed significantly reduced network level HIV transmission (p<0.05).

Conclusions

Sequence data from an HIV-1 screening program focused on recently infected persons and their social and sexual contacts enabled the characterization of a highly connected transmission network. The network-based risk score (TNS) was highly correlated with transmission risk behaviors and outcomes, and can be used identify and target effective prevention interventions, like ART, to those at a greater risk for HIV-1 transmission.

High percentage of recent HIV infection among HIV-positive individuals newly diagnosed at voluntary counseling and testing sites in Poland

To gain insight into HIV transmission we estimated the proportion of those recently infected. We examined data from HIV-positive patients and a random 10% sample of HIV-negative patients tested at Voluntary Counseling and Testing sites in Poland in 2006. Archived samples from positive patients were tested by three assays to differentiate recent from long-standing infection. Using logistic regression, we examined the association of recent infection (at least one assay) with age, sex, HIV exposure category, and the interval between self-reported HIV exposure and previous HIV test. Of 13,511 tests, 154 (1.1%) were HIV positive, representing 19.7% (n=783) of new diagnoses in Poland in 2006. Demographic and behavioral data were linked for 95, of whom 45 (47%) were recently infected and 1,001 were HIV negative. New diagnoses were more likely to be injectors (17% vs. 2%), men who have sex with men (MSM) (37% vs. 12%), and less frequent condom users (7.8% vs. 14% always) compared to HIV negatives. The median number of partners during the past 12 months was one and two among positives and negatives, but was higher among MSM-four and three, respectively. Ever injectors were less likely to be recently infected (adjusted OR=0.15, 95%CI=0.03-0.73). Having two or more sexual partners in the past 12 months was an independent predictor of recent infection (4.01, 1.4-11.49). We found no evidence that age or sex predicted recent infection. These data reinforce health education campaigns for safe sex messages, especially among MSM. They also suggest, albeit based on a subset of new diagnoses, that interventions should not be limited to selected age/sex groups.

Workshop summary: Novel biomarkers for HIV incidence assay development

Reliable methods for measuring human immunodeficiency virus (HIV) incidence are a high priority for HIV prevention. They are particularly important to assess the population-level effectiveness of new prevention strategies, to evaluate the community-wide impact of ongoing prevention programs, and to assess whether a proposed prevention trial can be performed in a timely and cost-efficient manner in a particular population and setting. New incidence assays and algorithms that are accurate, rapid, cost-efficient, and can be performed on easily-obtained specimens are urgently needed. On May 4, 2011, the Division of AIDS (DAIDS), National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH), sponsored a 1-day workshop to examine strategies for developing new assays to distinguish recent from chronic HIV infections. Participants included leading investigators, clinicians, public health experts, industry, regulatory specialists, and other stakeholders. Immune-based parameters, markers of viral sequence diversity, and other biomarkers such as telomere length were evaluated. Emerging nanotechnology and chip-based diagnostics, including algorithms for performing diverse assays on a single platform, were also reviewed. This report summarizes the presentations, panel discussions, and the consensus reached for pursuing the development of a new generation of HIV incidence assays.