Beyond Blood Smears: Qualification of Plasmodium 18S rRNA as a Biomarker for Controlled Human Malaria Infections.

18S rRNA is a biomarker that provides an alternative to thick blood smears in controlled human malaria infection (CHMI) trials. We reviewed data from CHMI trials at non-endemic sites that used blood smears and Plasmodium 18S rRNA/rDNA biomarker nucleic acid tests (NATs) for time to positivity. We validated a multiplex quantitative reverse transcription-polymerase chain reaction (qRT-PCR) for Plasmodium 18S rRNA, prospectively compared blood smears and qRT-PCR for three trials, and modeled treatment effects at different biomarker-defined parasite densities to assess the impact on infection detection, symptom reduction, and measured intervention efficacy. Literature review demonstrated accelerated NAT-based infection detection compared with blood smears (mean acceleration: 3.2-3.6 days). For prospectively tested trials, the validated Plasmodium 18S rRNA qRT-PCR positivity was earlier (7.6 days; 95% CI: 7.1-8.1 days) than blood smears (11.0 days; 95% CI: 10.3-11.8 days) and significantly preceded the onset of grade 2 malaria-related symptoms (12.2 days; 95% CI: 10.6-13.3 days). Discrepant analysis showed that the risk of a blood smear-positive, biomarker-negative result was negligible. Data modeling predicted that treatment triggered by specific biomarker-defined thresholds can differentiate complete, partial, and non-protective outcomes and eliminate many grade 2 and most grade 3 malaria-related symptoms post-CHMI. Plasmodium 18S rRNA is a sensitive and specific biomarker that can justifiably replace blood smears for infection detection in CHMI trials in non-endemic settings. This study led to biomarker qualification through the U.S. Food and Drug Administration for use in CHMI studies at non-endemic sites, which will facilitate biomarker use for the qualified context of use in drug and vaccine trials.

A framework for the assessment and implementation of diagnostics in outbreak situations.

OBSERVATION: Outbreak situations require in vitro diagnostics (IVDs) to identify those who are infected and to track the infectious agent in the population. However, such IVDs are typically not available and must be developed. In addition, the process of IVD development, assessment, and implementation are very time and resource intensive. Recognising the extraordinary public health need for IVDs in an outbreak situation, streamlined processes are needed to provide tests that meet the standard of a reasonable assurance of safety and effectiveness in the shortest amount of time. These IVDs are designated for outbreak use. ADDRESSING ISSUES: This paper presents a pathway to the outbreak use of IVDs that can be considered by countries experiencing an outbreak situation. It takes into account recognition of the outbreak, product development, regulatory evaluation, implementation, and monitoring of the outbreak-use test. Streamlined assessment programmes for emergency-use tests have been established by the US Food and Drug Administration and the World Health Organization. These programmes take into account test requirements for the country in which the outbreak exists. Therefore, countries can consider adopting these tests without the need to conduct expensive and time consuming assessments, such as performance studies. Key responsible parties are identified for each step of the pathway, recognising that transparency and communication among all parties are critical.

Perspectives on introduction and implementation of new point-of-care diagnostic tests.

In recent years, there has been significant investment from both the private and public sectors in the development of diagnostic technologies to meet the need for human immunodeficiency virus (HIV) and tuberculosis testing in low-resource settings. Future investments should ensure that the most appropriate technologies are adopted in settings where they will have a sustainable impact. Achieving these aims requires the involvement of many stakeholders, as their needs, operational constraints, and priorities are often distinct. Here, we discuss these considerations from different perspectives representing those of various stakeholders involved in the development, introduction, and implementation of diagnostic tests. We also discuss some opportunities to address these considerations.

Detection of human T-lymphotropic virus (HTLV) tax sequences in New York City blood donors seronegative for HTLV types 1 and 2.

A potential public health concern is the reported detection of the human T-lymphotropic virus (HTLV) tax gene in the lymphocytes of up to 11% of a low-risk group of New York City blood donors (NYBD). This study aimed to independently confirm the prevalence of HTLV tax sequences in 293 NYBD. All NYBD tested negative for antibodies to HTLV types 1 and 2 and HTLV Tax. HTLV tax sequences were not detected in the NYBD lymphocytes. These data demonstrate the lack of HTLV-1 tax in this group of NYBD at low risk for HTLV infection.