Donation archives and prospective donor-recipient repositories: indispensable tools for monitoring blood safety

In this issue of TRANSFUSION, the reports by Franklin and coworkers,¹ Yoshikawa and coworkers,² and Satake and coworkers³ illustrate how, worldwide, blood donation archives (defined as frozen aliquots of donation specimens retained primarily for operational purposes) and biospecimen repositories (collections of donor and/or recipient biospecimens that are made available to the research community) are instrumental in supporting blood center operations, resolving legal enquiries, and advancing the field of transfusion medicine through the conduct of key scientific investigations.

Franklin and colleagues describe the utilization of a systematic archive of samples from all donations given to the Scottish National Blood Service since shortly after the initiation of human immunodeficiency virus (HIV) antibody testing in the mid-1980s. This operational donation archive, which now consists of approximately 7 million cryopreserved donor serum samples, has been primarily accessed to inform recipient lookback notifications after donor seroconversion and to resolve cases of alleged blood transfusion transmission of infectious agents. Findings from an international survey aimed at understanding the objectives and status of donation archives in other parts of the world are also presented.

Yoshikawa and colleagues, with archived donation samples from the Japanese Red Cross (JRC), focus on dissecting the kinetics of not only the pre–hepatitis B surface antigen (HBsAg) window period (already scrutinized by previous Japanese and American studies) but more interestingly and, uniquely, its immediate aftermath.² This goal was accomplished by rigorous statistical analysis of hepatitis B virus (HBV) viral load and HBsAg data generated on serial samples from donors with incident HBV infections and for whom prior and subsequent samples were represented in the JRC systematic donation archive, which now includes approximately 55 million samples dating back to 1996. The study by Satake and colleagues utilizes the same archive to investigate cases of HBV in donors detected by HBsAg, anti–hepatitis B core antigen (HBc), and HBV nucleic acid test (NAT) screening (the latter performed on pools of 20-50 donations). Although the study design does not encompass the full spectrum of HBV infection in blood donors (due to the unique Japanese HBV screening strategy that defers donors who have high but not low-titer anti-HBc reactivity), it provides important new information on the shortcomings of pooled sample HBV NAT and, through compilation of lookback data from recipients of low-level DNA-positive transfusions, on differences in infectivity of transfusions from donations given during the early window period versus those from donors with so-called “occult” HBV infections who test anti-HBc–positive.

The main difference between the two nations was that the use of archived donation samples in Scotland was limited to resolving potential transfusion-transmitted cases, providing evidence for legal purposes and for testing samples corresponding to extant inventory when a new test was being implemented, whereas the JRC archive was also used to answer important scientific questions, that is, was employed as a research biospecimen repository. The survey by Franklin and coworkers reviewed policies and practices of routinely archiving donor samples in 24 developed countries, documenting remarkable disparities. Although operational donation archives are common in European countries, no routine donation archives have been established in several large wealthy countries outside Europe, including the United States, Canada, and Australia (only marker-reactive specimens are routinely stored in these countries). Of note, although not included in the survey, several resource-limited countries such as Brazil maintain universal donation repositories similar to those in Scotland and Japan, albeit for shorter (6-month) mandatory retention periods. The survey also documents marked disparities in policies on whether or not archived donor samples are opened to scientific research, either during or beyond their legal lifetime, in addition to being accessed for operational and legal reasons.

Over the past 25 years, different types of donor archives and biospecimen repositories have been constituted and used for the purpose of blood safety. As discussed by Franklin and coworkers, the first type of repository is a mandatory archive from all donations constituted to investigate legal cases implicating transfusion-transmissible agents, which seem to arise with increasing frequency around the world. In most cases, such archives consist of frozen, deep-well microtiter plates produced by automated filling of plate wells shadowing pipetting of serum or plasma samples into microtiter plates for serologic marker or NAT. As a consequence, the volume of plasma collected is generally below 1 mL, which considerably limits the possibility to conduct multiple studies for operational or scientific interest. Even in legal cases, a limited number of serologic or molecular assays can be performed. In a few countries such as Japan, Austria, Germany, New Zealand, Scotland, and the Netherlands, approximately 2 mL of serum or plasma is stored, providing more flexibility for both scientific and legal objectives. The approach taken in the Netherlands is noteworthy. Although in the rest of the country samples in the routine donation archive are destroyed after 2 years, samples in the Amsterdam repository, which consists of approximately 3 million donation samples collected and stored since 1987⁵ are retained indefinitely and have been made available as anonymized samples for research purposes, with data published in 15 original articles. In many countries, however, laws do not permit any other use of archived donation samples other than those required for clinical case investigations, even beyond the legally mandated retention life of the archive. Massive in size and operationally complex (especially if GMP requirements are enforced), the very high costs of constituting, storing, and occasionally by use of these donation archives are usually supported by the blood collection organizations. Unfortunately, due to restrictions in most countries noted above, the scientific return is minimal despite considerable potential, as illustrated by the two studies based on the JRC archive in this issue of TRANSFUSION.

Conversely, a number of research repositories have been constituted specifically for scientific purposes.⁴ Although operational archives are important, we feel strongly that research repositories are key to advancing the field and should be established and maintained. Such repositories have historically been supported or commissioned by research agencies to study specific questions regarding blood safety or for monitoring the safety of blood related to known, emerging, or unknown infectious agents. They may involve exclusively donor samples (e.g., the Transfusion Safety Study [TSS] Donor Repository and the Retrovirus Epidemiology Donor Study [REDS] General Serum Repository [GSR], and General Leukocyte/Plasma Repository [GLPR]), exclusively recipient samples (e.g., Frequency of Agents Communicable by Transfusion Study [FACTS] or Cooleycare) or samples from linked donor-recipient pairs. Such donor-recipient repositories are more complicated and expensive to create, but are also more powerful in that they can be used to establish rates of transmission of infectious agents by transfusions and to investigate correlates of transmission and pathogenicity questions. Examples of donor-recipient repositories in the United States include the NIH Clinical Center Studies, the Transfusion Transmitted Viruses Study (TTVS), the Viral Activation Transfusion Study (VATS), and the REDS Allogeneic Donor and Recipient Repository (RADAR); donor-recipient repositories established in Europe include the Amsterdam Blood Center donor-recipient cohort, the National Blood Service/National Health Service (NBS/NHS) donor-recipient study,⁵ and the Blood and the European Organ Transmissible Infectious Agents study (BOTIA). Details regarding these repositories are provided in Table 1, with references to resulting manuscripts posted on the TRANSFUSION Web site.

Being intended for multiple research usages, samples accessioned into these repositories come from donors and/or recipients who have given specific informed consent for long-term storage and testing, and often an extra tube of blood was obtained that was dedicated to building the repository. Consequently several milliliters of serum or plasma, distributed into multiple aliquots, were frozen in the early studies, while more recently established repositories also include frozen whole blood or cellular fractions (GLPR, VATS, RADAR, and BOTIA) to allow for detection of intracellular viruses or other infectious agents such as bacteria, parasites, and even prions. Given broader consent, these specimens can also be used for research beyond the field of transfusion medicine. For example, the REDS group has provided panels of HIV-reactive donor specimens for the evaluation of the HIV-SELECTEST, a new assay designed to differentiate HIV-specific antibodies induced by HIV vaccines from those induced during natural infection.⁶ This is a prime example of how these specimens can be used to evaluate a new technology with short-term impact for the conduct of clinical trials for the vaccines, and potential long-term impact for countries where HIV vaccination will eventually become highly prevalent, including potential use in not only diagnostic testing but also donor screening.

The cost of recipient or donor-recipient studies is considerably increased by the need to collect informed consent from prospective patients before or shortly after transfusion and to obtain one or more posttransfusion samples, often at home, to document seroconversion. Therefore, the number of linked samples in these repositories tends to be limited to 10,000 to 50,000, in contrast to the larger donor research repositories that range up to more than 500,000 donations. Certain recipient-based repositories can be used to assure with 95 percent confidence that a putative transfusion-transmissible agent with a prevalence 0.1 to 1 percent will be identified and its transmission rate assessed. Owing to their relatively modest size, however, a negative result might not exclude a transmission risk for low prevalence agents for which there is considerable public health concern.^7,8 We are now dealing almost exclusively with rare events in transfusion safety studies, with risks of emerging agents or yields of new tests as low as 1 in 100,000 or even 1 in 1,000,000 considered significant (e.g., the p24 controversy in the United States in the 1990s, the debate over variant Creutzfeldt-Jakob disease and human herpesvirus-8 transmission risk, and the incremental yield of individual donation relative to minipool NAT for HIV, HCV, and HBV). As a result of the high cost of building adequately powered donor-recipient repositories, research agencies are often limited in their ability to create these important resources. Moreover, research agencies would not support development of a repository if the participants did not appropriately consent and require proof of institutional review board (IRB) approval to proceed. IRBs in different countries and even different institutions within a country may vary in terms of what they approve or not, and definitions of adequate consents have evolved through time. This issue raises ethical and legal concerns regarding defined purpose repositories, for which donor and/or recipient consent may have been limited, for projects other than those initially intended. This is particularly a problem with respect to older repositories where consent forms may not be on par with currently accepted norm; fortunately most IRBs appreciate that consent policies have evolved and will usually accept requests for use of anonymized specimens in these situations. Access to biospecimens stored in government sponsored research repositories generally requires review by a committee comprised of scientific and ethical experts charged with reviewing whether the scientific merit of the request warrants use of this valuable, and often scarce, resource and whether appropriate consents and IRB approvals were obtained. Such requests can come from the original investigators involved in establishing the repository as well as from nonstudy investigators. Such a committee has been established by the US National Heart, Lung, and Blood Institute (NHLBI) to oversee repository accessioning requests for the NHLBI Biospecimen Repository (http://www.nhlbi.nih.gov/resources/medres/reposit/contents.htm).

There is clear evidence that the data obtained from studies with blood donor and/or recipient research biospecimen repositories have been of great value, since over 200 publications in peer-reviewed journals have resulted from studies generated from these repositories (Table 1 and supplementary material). The investigators using these repositories have made many seminal contributions to transfusion safety, such as establishing the viral origin and transmissibility by transfusion of the agents responsible for non-A, non-B hepatitis (HCV) and AIDS (HIV); the transmissibility by transfusion but lack of relation to hepatitis of GBV-C/HGV and Sen-V; and the contribution to blood safety of new assays such as improved generation antibody, HIV p24 antigen, and NAT assays.

In this age of the precautionary principle, the availability of large repositories representative of the donor population over time is becoming a necessary instrument for both research investigations and policy making. Funding of repositories of ever-increasing sizes should continue to be supported directly by governments, either via research institutions like the NIH or blood banking agencies like NBS or Sanquin. In the United Kingdom, for instance, the government through the NHS has constituted a bank of samples from 500,000 individuals, which will be stored for 20 years to study the genetic and proteomic markers potentially associated with a range of diseases. The time may come soon where a similar undertaking will be necessary for surveillance of new infectious disease threats, not only in a given country, but possibly regionally or even globally. Integration of the objectives of blood donor and recipient repositories developed for assessment of blood safety with those of disease biomarker repositories may present an opportunity to leverage both objectives at lower cost.⁸

Another critical question in the era of globalization of infectious disease threat is exemplified by SARS, bird flu, and other zoonotic agents that appear to be particularly common problems in Africa and Southeast Asia. This raises the question of whether developed countries that have so far funded research repositories should seriously consider the importance of including samples from selected developing countries where most of these emerging potential transfusion pathogens originate. This issue has been recognized with the recent establishment of the NHLBI-funded REDS II International program, which now includes collaborative networks of blood centers in Brazil and China, as well as by BOTIA, which includes a study arm in West Africa. The International Society of Blood Transfusion (ISBT) Working Party on Infectious Diseases has also initiated a project to try to establish a virtual repository of donor specimens, where participating blood centers store well-characterized donor samples of interest that are made available to investigators.

In view of the clear benefits, illustrated by the Japanese studies in this issue of TRANSFUSION, of accessing systematic donation archives for scientific purposes, we believe that restrictive legislation regarding the use of such archives, at least after their legal storage life has expired, should be reconsidered. The use of microtiter plate-formatted tubes allowing storage of larger volumes of plasma and whole blood rather than microplates should also be considered, so that not only operational and legal demands but also scientific needs can be taken into consideration, particularly in times of emergency. Storage of larger volumes will incur increased expense in the short term, but will considerably increase the blood safety and broader scientific and public health value of these repositories in the future. To make these resources powerful research tools it is important to address ethical and/or informed consent considerations when the specimens are collected to allow for their future use and to assure the availability of demographic, laboratory, and if appropriate, clinical data linked to the specimens. The ability to link to phenotypic information is key to optimal use of specimens and represents an administrative and data management challenge that needs to be met for the repositories to be useful. Finally, the concept of sharing is important: repository samples need to be made widely available to the scientific community and programs need to be established to increase awareness among the scientific community that this rich resource is available for their use.