Neural Transplantation for Huntington's Disease: Experimental Rationale and Recommendations for Clinical Trials

Huntington's disease (HD) is a neurodegenerative disorder affecting motor function, personality, and cognition. This paper reviews the experimental data that demonstrate the potential for transplantation of fetal striatum and trophic factor secreting cells to serve as innovative treatment strategies for HD. Transplantation strategies have been effective in replacing lost neurons or preventing the degeneration of neurons destined to die in both rodent and nonhuman primate models of HD. In this regard, a logical series of investigations has proven that grafts of fetal striatum survive, reinnervate the host, and restore function impaired following excitotoxic lesions of the striatum. Furthermore, transplants of cells genetically modified to secrete trophic factors such as nerve growth factor protect striatal neurons from degeneration due to excitotoxicity or mitochondrial dysfunction. Given the disabling and progressive nature of HD, coupled with the absence of any meaningful medical therapy, it is reasonable to consider clinical trials of neural transplantation for this disease. Fetal striatal implants will most likely be the first transplant strategy attempted for HD. This paper describes the variable parameters we believe to be critical for consideration for the design of clinical trials using fetal striatal implants for the treatment of HD.

[Transplantation as a care about neighbour health and life]

Taking into account current developments in medicine and the increasingly extended lifespan of our patients, the role of transplantation and the related issues have become increasingly more urgent and have demanded more attention in recent years. Transplantation is a branch of medical studies which has been developed as a result of the need to find answers to unsuccessful organ transplants. Transplants are the future of the contemporary medicine and provide better prospects for patients with defective organs. In spite of the rapid development and huge successes achieved in the field of transplantation, the major problem we are facing, both in terms of the legal and ethical aspects, is the lack of the organ donors. Developing social awareness and continuous education can bring about positive changes to the current shortage of donors. The role of the church and the media in promoting the importance of organ donation will also greatly contribute to the future success of transplantation thus saving human lives.

[The reconstructive sequence in the 21st century. A reconstructive clockwork]

Mathes and Nahai introduced the conventional reconstructive ladder in 1982 to address tissue defects starting with primary and secondary closure of wounds followed by autologous skin grafting. Regional and local pedicled flaps, tissue expansion and free tissue transfer were further steps. Despite enormous achievements and refinements in these techniques, clinical situations and problems occur beyond the scope of these conventional reconstructive measures. Composite tissue allotransplantation (CTA) of partial faces or of unilateral or bilateral forearms and upper arms, are a novel part of transplantation medicine. The initially reported clinical results are encouraging, especially in light of the initial clinical reports of organ transplantation. However, short and long term problems such as potential tumor induction by immunosuppression and chronic rejection must be taken into consideration. Given the fact that patients receiving CTA have already undergone various reconstructive procedures before, patients often gain tremendous improvement in the quality of life. Robots such as the Da Vinci system for surgeons and the Penelope assistant robot have found their way into the surgical routine. While even microsurgical anastomosis has been accomplished using the Da Vinci system, the total amount of time and resources spent is beyond being practical at present. Regeneration and tissue engineering are of distinct interest in reconstructive surgery. Adipose-derived stem cell transfer is able not only to improve contour defects by volume effects, but also to improve the quality of the overlying skin. Therefore we would propose that these novel techniques, CTA, robotics, regeneration and tissue engineering should be considered as potential future integral cogs in the reconstructive mechanism for the 21st century with the patient being at the centre of the reconstructive efforts.

Gene therapy in transplantation: Toward clinical trials

The genetic modification of organs or cells is an attractive approach to protect allogeneic transplants from acute rejection and other complications. The transplant setting offers a unique opportunity to utilize ex vivo gene therapy for the modification of allogeneic organs and tissues prior to implantation. However, significant challenges exist in the application of this concept to human organ transplantation, including the large number of potential molecular targets, the diversity and safety profile of available vector delivery systems and the merging of gene-based therapies with existing immunosuppressive regimens. Accordingly, many different therapeutic concepts and vector systems have been investigated in preclinical studies with the aim of prolonging allograft survival. However, the translation of promising gene therapy strategies to transplant clinical trials has lagged behind the progress made in other medical fields. This review describes the recent preclinical applications of gene transfer to transplantation, and critically evaluates the degree to which gene therapy has been tested clinically in organ transplant recipients.

Metabonomics: a useful tool for the future surgeon

BACKGROUND

In the past decade or so, a range of technologies have emerged that have shown promise in increasing our understanding of disease processes and progression. These advances are referred to as the "omics" technologies; genomics, transcriptomics, and proteomics. More recently, another "omics" approach has come to the fore: metabonomics, and this technology has the potential for significant clinical impact. Metabonomics refers to the analysis of the metabolome, that is, the metabolic profile of a system. The advantage of studying the metabolome is that the end points of biological events are elucidated.

RESULTS

Although still in its infancy, the metabonomics approach has shown immense promise in areas as diverse as toxicology studies to the discovery of biomarkers of disease. It has also been applied to studies of both renal and hepatic transplants. Metabolome analysis may be conducted on a variety of biological fluids and tissue types and may utilize a number of different technology platforms, mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy being the most popular. In this review, we cover the background to the evolution of metabonomics and its applications with particular emphasis on clinical applications.

CONCLUSIONS

We conclude with the suggestion that metabonomics offers a platform for further biomarker development, drug development, and in the field of medicine.

Composite tissue transplantation: a rapidly advancing field

Composite tissue allotransplantation (CTA) is emerging as a potential treatment for complex tissue defects. It is currently being performed with increasing frequency in the clinic. The feasibility of the procedure has been confirmed through 30 hand transplantation, 3 facial reconstructions, and vascularized knee, esophageal, and tracheal allografts. A major drawback for CTA is the requirement for lifelong immunosuppression. The toxicity of these agents has limited the widespread application of CTA. Methods to reduce or eliminate the requirement for immunosuppression and promote CTA acceptance would represent a significant step forward in the field. Multiple studies suggest that mixed chimerism established by bone marrow transplantation promotes tolerance resulting in allograft acceptance. This overview focuses on the history and the exponentially expanding applications of the new frontier in CTA transplantation: immunology associated with CTA; preclinical animal models of CTA; clinical experience with CTA; and advances in mixed chimerism-induced tolerance in CTA. Additionally, some important hurdles that must be overcome in using bone marrow chimerism to induce tolerance to CTA are also discussed.

Transplant biology at a crossroads

Despite major advances in transplantation biology, allowing transplants not just of critical organs like heart and kidney but also of limbs and faces, researchers are still struggling to minimize the risks from achieving the level of immunosuppression needed to make the body accept foreign tissues.

Life in death: an overview of solid organ transplant in Shiraz, Iran

Advances in organ preservation, immunosuppression, and surgical procedures have resulted in improved outcomes and survival rates. However, regarding organ transplant in different communities, these advances raise major ethical, policy, and religious issues. Transplant progress in Iran, in relation to the rest of the world, has been slow at times and quick during others. Between 1988 and 1993, there was a rapid surge in experiments with tissue transplant in Iran, and the Shiraz Organ Transplantation Center, established in 1988, rose to become a pioneer of the most significant improvements, a leading center for organ transplant, and the only center for liver transplant in Iran. In this article, we review milestones in the development of a successful organ transplant program and implementation of legislation in Iran. The Shiraz model of transplant is a new program that attempts to overcome the problems of organ shortage. We provide a description of the Iranian model of transplant and its restrictions and examine the most promising future trends in this exciting field.

Transplantation research in Iran: a bibliometric study

BACKGROUND

Scientific articles are indicators of research interest and efforts in every country. The aim of the current study is to describe the characteristics of the transplantation-related research efforts with respect to the domestic published works in Iran between 1993 and 2003.

MATERIALS AND METHODS

In a descriptive design, we searched IranMedex (Iranian database for indexing medical articles; available at: http//www.iranmedex.com) for all the biomedical articles published between 1993 and 2003 in 91 Iranian journals. The search was conducted using "transplantation" and "transplant" as key words. A printed copy of the references was reviewed individually so as to identify the transplanted organ, study design, number of authors, and type of article.

RESULTS

Among 11371 articles, 545 (4.8%) were related to transplantation. An increasing trend was observed in the number of publications from 1993 to 2003. Most articles were published in Farsi (90%). The most frequently published articles were original articles (84.4%). The main subjects of were kidney (61.7%), followed by liver (12%) and bone marrow transplantation (10.8%). Cornea was the topic of research in only 3% of the papers. Of all manuscripts, 9.5% consisted of clinical trials. The mean number of authors was 3.6 +/- 2.2 (1 to 14).

CONCLUSIONS

Iranian researchers seem to be interested in the topic of transplantation; however, some fields of transplantation are neglected. This pooling of valuable information can be used by other countries, especially by researchers from the Middle East Society for Organ Transplantation region. Such databases could form an invaluable network for an exchange of experience in the region to solve common problems.

Organ donation and utilization in the United States, 1996-2005

The success of clinical transplantation as a therapy for end-stage organ failure is limited by the availability of suitable organs for transplant. This article discusses continued efforts by the transplant community to collaboratively improve the organ supply. There were 7593 deceased organ donors in 2005. This represents an all-time high and a 6% increase over 2004. Increases were noted in deceased organ donation of all types of organs; notable is the increase in lung donation, which occurred in 17% of all deceased donors. The percentage of deceased donations that occurred following cardiac death has also reached a new high at 7%. The number of living donors decreased by 2%, from 7003 in 2004 to 6895 in 2005. This article discusses the continued efforts of the Organ Donation Breakthrough Collaborative and the Organ Transplantation Breakthrough Collaborative to support organ recovery and use and to encourage the expectation that for every deceased donor, all organs will be placed and transplanted.

Pediatric transplantation in the United States, 1996-2005

Solid organ transplantation is accepted as a standard lifesaving therapy for end-stage organ failure in children. This article reviews trends in pediatric transplantation from 1996 to 2005 using OPTN data analyzed by the Scientific Registry of Transplant Recipients. Over this period, children have contributed significantly to the donor pool, and although the number of pediatric donors has fallen from 1062 to 900, this still accounts for 12% of all deceased donors. In 2005, 2% of 89,884 candidates listed for transplantation were less than 18 years old; in 2005, 1955 children, or 7% of 28,105 recipients, received a transplant. Improvement in waiting list mortality is documented for most organs, but pretransplant mortality, especially among the youngest children, remains a concern. Posttransplant survival for both patients and allografts similarly has shown improvement throughout the period; in most cases, survival is as good as or better than that seen in adults. Examination of immunosuppressive practices shows an increasing tendency across organs toward tacrolimus-based regimens. In addition, use of induction immunotherapy in the form of anti-lymphocyte antibody preparations, especially the interleukin-2 receptor antagonists, has increased steadily. Despite documented advances in care and outcomes for children undergoing transplantation, several considerations remain that require attention as we attempt to optimize transplant management.

A recipient risk score for deceased donor renal allocation

BACKGROUND

The current shortage of deceased donor kidneys makes it difficult to design a kidney allocation scheme that balances optimal utility with supply. The aim of this study is to derive a recipient risk score (RRS) that could be used with the deceased donor score (DDS) to maximize the total number of years of renal allograft function as a means to improve allocation.

METHODS

We retrospectively reviewed 47,535 adult recipients of deceased donor renal transplants between 1995 and 2002 from the United Network for Organ Sharing Standard Transplant Analysis and Research Files. Multivariable Cox regression models were used to derive an RRS and estimate recipient and graft survival as a function of RRS. Annual rates of organ supply and recipient demand for deceased donor kidneys were estimated from expectancy data and expressed in renal years (years provided by a functioning kidney allograft). Renal-year analyses were used to optimize allocation.

RESULTS

The strongest predictors of recipient survival after transplantation used in the RRS were recipient age, history of diabetes mellitus, history of angina, and time on dialysis therapy. When used with DDS, RRS provided a utility-based allocation system for deceased donor kidneys that theoretically increased the annual (2002) rate of supply by 15%.

CONCLUSION

The RRS is a practical system that, when combined with a method to assess donor organs, such as DDS, may improve deceased donor renal allocation.

The Transplantation Society--new key opinion leaders of tomorrow 2006

One of the new initiatives taken by the immediate past president of The Transplantation Society, KJ Wood, is to introduce a new series of meetings named 'New Key Opinion Leaders of Tomorrow'. The Transplantation Society invites the leading young investigators in the field of transplantation to participate in this meeting together with the present leaders of the field. The key objective of this meeting is to identify the potential key opinion leaders of tomorrow. Each presentation during the meeting was jointly given by the senior and junior investigators. The meeting in Buenos Aires covered six main topics on clinical, translational and basic transplantation. These included: innate immunity and inflammation; transplant infectious diseases; tumour and transplantation; medical and ethical aspects of transplantation; dendritic cells (stimulating and manipulating the immune response to a transplant); and ABO incompatible donor recipient pairs. This report focuses on the emerging biological therapeutics and their ramifications on clinical transplantation.

[Changes in the transplantation world--from altruism to a utilitarian approach]

The lack of organs for transplantation is a worldwide problem that has created a moral conflict between the traditional altruistic basis of organ donation and alternative solutions based on utilitarian grounds. Survival of grafts achieved in recent decades after unrelated living-donor kidney transplantation between spouses is longer than with deceased donor transplantation. This experience justified the extension of kidney donation beyond the traditional close family relationships including: anonymous donors and paired exchange programs. However, unrelated donation of kidneys within altruistic norms could not provide an ultimate solution for the lack of organs for transplantation. On the other hand, globalization and development of advanced medical technology in developing countries that do not provide transplantation for all their citizens, created an opportunity for a worldwide flourish of transplant tourism as an alternative solution for transplant candidates. Transplant tourism functions according to market laws and is profit-driven, as opposed to the legal organ exchange programs in Europe and the U.S.A., which are non-profit and patient-oriented. The transition from trade in kidneys from unrelated living-donors to the use of other organs (heart, lung and liver) from death penalty prisoners in China was only a matter of deciding where to lay the moral border when justifying the act for the sake of life-saving. Considering the inability of current legal altruistic transplantation practice to supply the growing need for organs, healthcare authorities and professional transplantation organizations have to tackle the donor crisis by designing legally acceptable utilitarian solutions. For instance, through the formation of international organ exchange programs under formal agreements or, in the case of kidney transplantation, through the establishment of a regulated compensated donation system.

World Transplant Congress. Boston, Massachusetts, USA, 22-27 July 2006

The World Transplant Congress (WTC) is the first joint international transplant meeting co-organised by the Transplantation Society, the American Society of Transplantation (AST) and the American Society of Transplant Surgeons (ASTS). It was the first meeting of this calibre that was being held by three world-renowned authorities in the field of transplantation. Under the direction of the congress president, AB Cosimi, the attendance of this meeting is a 'must' for all working in the field of transplantation. The congress had provided an important forum for the exchange of new scientific and clinical information that is relevant to solid organ and tissue transplantation. In addition, it also created an arena for the interchange of ideas regarding the care and management of transplant recipients. There were many sessions that were engineered in order to facilitate the discussion of socioeconomic, ethical and regulatory issues related transplantation. On the whole, the meeting has set a very high standard for any future transplant congresses to match-providing the delegates with updates on transplantation with the new scientific prospectives in T cell costimulation, innate immunity (dendritic cells), anatomy of immune response and regulatory T cell biology. More importantly, it has highlighted the potentials of harnessing these new findings for future biological therapies in preventing rejection and inducing tolerance.

Is clinical tolerance realistic in the next decade?

Tolerance to allografts would mean a better quality of life and prognosis for transplant patients. Despite the first descriptions of tolerance to alloantigens over 50 years ago, deliberately induced tolerance in the clinic on a wide scale remains a goal that is not quite in reach. However, much progress has been made in understanding tolerance in rodent models and in the few reports of induced or spontaneously occurring tolerance in humans. Here, we review this progress made in the quest to achieve clinical tolerance.

The cancer and leukemia group B transplant committee

The Transplant Committee of the Cancer and Leukemia Group B has a robust portfolio of studies and is poised to make significant contributions to the field. We are working in collaboration with the Cancer and Leukemia Group B Leukemia and Lymphoma Disease Committees and importantly in collaboration with other groups to define the role of both autologous and reduced-intensity allogeneic transplantation in the management of selected hematologic malignancies. Some of our studies have the potential to change the standard of care in areas such as the maintenance therapy for multiple myeloma after autologous transplantation and to generate the data that could lead to acceptance of new approaches to the initial post-remission therapy of older adults with acute myeloid leukemia. The cooperative group setting allows us to advance the transplant field by showing which approaches are successful outside of single institutions and are therefore feasible on a generalized basis.

Liver and intestine transplantation in the United States, 1995-2004

Three years of survival data are now available and the impact of the model for end-stage liver disease (MELD) allocation system is becoming clear. After a decline in new registrants to the waiting list in 2002, the number increased to 10 856 new patients in 2004. Since the implementation of MELD, the percentage of patients who have been on the list for 1-2 years has declined from 24% to 19%. There has been a shift upward in the percentage of patients with higher MELD scores on the waiting list. An increasing percentage of adult living donor liver recipients are over the age of 50 years; from 1% in 1997 to 51% in 2004. Parents donating to children (93% of living donors in 1995), represented only 14% in 2004. Long-term adjusted patient survival declined with increasing recipient age in adults following either DDLT or LDLT. Cirrhosis caused by chronic hepatitis C virus (HCV) is the leading indication for liver transplantation and is associated with reduced long-term survival in recipients with HCV compared to those without HCV, 68% at 5 years compared to 76%. Although the intestine waiting list has more than doubled over the last decade, an increasing number of centers now perform intestinal transplantation with greater success.

Transplant Surgeon Formation: Vocation, Incentives, Between Old and New Surgeon Generations

The training of the transplant surgeon is one of the most difficult paths in medicine. The transplant surgeon must be trained as a general and a vascular surgeon; he has to be skilled and upgraded in transplant surgical technique; he has to decide the suitability of the donor and of the organs as well as the immunosuppressive therapy for each recipient; he must know the intensive care unit, hepatology, and nephrology. The transplant surgeon has to deal with surgical, infectious, and metabolic complications after organ transplantation. Thus, clinical formation of the transplant surgeon is multifactorial and always upgraded. However, transplants never happen in the morning; retrivals are more likely to be in the night (especially the holidays ones). "Weekend" is a word not frequently used by transplant surgeons. Moreover, when the transplant procedure happens, the normal activity of the ward and of the outpatient clinic were have to be done. The transplant surgeon must have a sort of "vocation" for such a job. Organ harvesting setting is a good proof of adaptability, always during nighttime, often in small hospitals with operating room nurses unfamiliar with the procedure, sometimes waiting for some colleagues or delaying the surgery. This vocation is enhanced by enthusiasm, but incentives are necessary to feed this love. Incentives should be professional and economic; transplant surgeons should be allowed to make clinical decisions, to choose the surgical technique of transplantation, to control the decision process. Lastly, due to the "total on call," the surgeon should profit from a right salary avoiding extramural activities.

The history and activities of transplantation in Turkey

The cornerstone events of transplantation history in Turkey are summarized herein. In 1975, we performed the first living-related renal transplant in Turkey. This was followed in 1978, by the first deceased donor kidney transplantation, using an organ supplied by Eurotransplant. In 1979 the law on harvesting, storage, grafting, and transplantation of organs and tissues was enacted; later that year, the first local deceased donor kidney transplantation was performed by our team. In 1988, another groundbreaking event in Turkey was successfully achieved; the first cadaveric liver transplantation; and in 1990, the first pediatric living-related segmental liver transplantation in Turkey and in the region by our team. One month later, an adult-to-adult living-related liver transplantation was successfully performed. Until now, we have performed 1506 kidney and since 1988, 121 liver transplantations. During 29 years of solid organ transplantation history in Turkey, 6686 kidney transplants have been performed nationwide in 28 different centers; 696 livers; 13278 corneas; 2883 bone marrow; 132 hearts; and 15 pancreas transplants. In 2001, the health ministry established the National Coordination Center as an umbrella organization to promote transplantation activities, especially for deceased donor organ procurement. Transplantation activities are accelerating day by day all around the country, but deceased donors are still far below the desired rates. Improvements in the fields of education and coordination should increase the quality and the quantity of transplantation activities.

[Ethicolegal issues of organ donation as the main obstacle to the progress of clinical transplantation]

Ethicolegal issues present the main factor hindering obtaining organs from corpses and living donors, the distribution of cadaveric organs, and the financial providence of donorship in Russia. The actual Russian legislation is contradictory in terms of obtaining relatives' consent for the transplantation of cadaveric organs. There are no precise definitions of the degree of genetic relationship between the donor and recipient sufficient for transplantation. Selling and purchasing human organs is strictly prohibited, while financial compensation of the living donor seems to be a fair measure. Providing the possibility to verify brain death is a necessary condition for expanding the cadaveric organ pool. The organ shortage leads to improper distribution of donor organs. All these problems have to be solved for the progress of organ transplantation in Russia.

What's new--what's hot in basic science: American Transplant Congress 2004

The field of transplantation biology has, in the past year, given rise to several improved models explaining the in vivo phenomena of allograft rejection and acceptance. Although T-cells remain central participants in allorecognition, innate immune cells are increasingly recognized as critical. There is also growing acceptance that T-cell responses can vary widely not only based on their repertoire, but also on their immune experience in general, and their participation in homeostatic proliferation. Additional signaling pathways and molecules, such as the Janus kinase pathway and vascular endothelial growth factor have been added to those recognized as important in pharmacologic immunosuppression, and the concepts of regulation, once polarized between CD8+ and CD4+ camps, have begun to converge upon a recognition that there are many phenotypes of regulatory cells. In addition to improved basic science, several translational fields have accelerated in the past 12 months. Promising and clinically applicable islet transplant regimens have been developed and look appropriate for near-term clinical trials. Significant progress in discordant xenotransplantation is also apparent. This manuscript will review the past year in transplantation science as reported at the 2004 American Transplant Congress.

What's new--what's hot in clinical science: American Transplant Congress 2004

The American Transplant Congress 2004, held in Boston last May, was the biggest conference in the history of the event, with over 4000 attendees. A wide variety of clinical topics were presented and discussed, all advancing the field of solid organ transplantation. This manuscript will attempt to summarize the presentations at the meeting. Particularly 'hot' clinical topics included the recent passage of a law to increase organ recovery, the use of expanded criteria kidney donors, a new model for the allocation of deceased donor lungs, survival following liver transplantation and its potential effect on liver allocation and the use of novel immunosuppressive drugs.

New approaches to replacing failing organs

The foremost cause of death and disability is organ failure. Failure of the heart, lungs, kidney, and liver is typically addressed by organ transplantation; however, the number of human organs available for this purpose is quite limited. For this reason, some new technologies are being advanced for the treatment of organ failure. This communication summarizes potential limitations of these technologies.

Pediatric transplantation

Analysis of the OPTN/SRTR database demonstrates that, in 2002, pediatric recipients accounted for 7% of all recipients, while pediatric individuals accounted for 14% of deceased organ donors. For children fortunate enough to receive a transplant, there has been continued improvement in outcomes following all forms of transplantation. Current 1-year graft survival is generally excellent, with survival rates following transplantation in many cases equaling or exceeding those of all other recipients. In renal transplantation, despite excellent early graft survival, there is evidence that long-term graft survival for adolescent recipients is well below that of other recipients. A causative role for noncompliance is possible. While the significant improvements in graft and patient survival are laudable, waiting list mortality remains excessive. Pediatric candidates awaiting liver, intestine, and thoracic transplantation face mortality rates generally greater than those of their adult counterparts. This finding is particularly pronounced in patients aged 5 years and younger. While mortality awaiting transplantation is an important consideration in refining organ allocation strategies, it is important to realize that other issues, in addition to mortality, are critical for children. Consideration of the impact of end-stage organ disease on growth and development is often equally important, both while awaiting and after transplantation.

Transplant data: sources, collection, and caveats

By examining the sources, quality and organization of transplant data available, as well as making observations about data reporting patterns and accuracy, we hope to improve understanding of existing results, help researchers with study design and stimulate new exploratory initiatives. The primary data source, collected by the OPTN, has benefited from extensive recent technological advances. Transplant professionals now report patient and donor data more easily, quickly, and accurately, improving data timeliness and precision. Secondary sources may be incorporated, improving the accuracy and expanding the scope of analyses. For example, auxiliary mortality data allows more accurate survival analysis and conclusions regarding the completeness of center-reported post-transplant follow-up. Furthermore, such sources enable examination of outcomes not reported by centers, such as mortality after waiting list removal, providing more appropriate comparisons of waiting list and post-transplant mortality. Complex collection and reporting processes require specific analytical methods and may lead to potential pitfalls. Patterns in the timing of reporting adverse events differ from those for 'positive' events, yielding the need for care in choosing cohorts and censor dates to avoid bias. These choices are further complicated by the use of multiple sources of data, with different time lags and reporting patterns.