Hepatitis E virus (HEV) infection results in hepatitis E, an acute and self-limited disease. The virus is transmitted in a faecal–oral manner and is a major cause of viral hepatitis in much of the developing world, where it causes rampant sporadic infections and large epidemics. A curious feature of hepatitis E is the unusually high rates of mortality that are observed in pregnant women, in whom the disease is exacerbated by the development of fulminant liver disease. In the absence of viable in vitro propagation systems, several geographical isolates of HEV have been maintained in vivo in nonhuman primates and, subsequently, the viral genome has been cloned and sequenced. HEV has been classified provisionally into a separate family known as the HEV-like viruses, which has at least four recognised genotypes, but has only a single serotype. The viral genome is a positive-stranded (+)RNA of ~7.5 kb and encodes at least three proteins. Open reading frame 1 (ORF1) encodes the viral nonstructural polyprotein, which has domains that are homologous to some of the replication and processing enzymes found in other +RNA viruses. The HEV protein itself remains poorly characterised. The protein encoded by open reading frame 2 (ORF2) is the major HEV capsid protein, and the protein encoded by open reading frame 3 (ORF3) appears to be involved in virus–host interactions. Several questions related to the biology, epidemiology and pathogenesis of HEV remain unanswered; the progress of a few of these is reviewed here.

Viruses replicate inside host cells, where they use host biochemical and structural components to facilitate the production of new virus particles. As a consequence of co-evolution with their hosts, viruses have acquired host genes and genetic mutations that confer dominance over normal cell function. Research on virus–cell interactions has focused on the identification of mechanisms of virus dominance in order to develop therapeutic strategies for preventing productive infection. Although such research remains an essential part of molecular virology, viruses are also important genetic tools that can be used to analyse cell function. Because virus genomes contain genetic information, some of which was derived from host cells, it is possible that the analyses of virus–host interactions might lead to the identification of functionally dominant virus genes and novel eukaryotic counterparts. In this article, we have described how transforming and non-transforming viruses can control cell motility (cell migration or membrane projection), and explained how the analysis of virus cytopathic effects (CPEs) led to the identification of a novel family of cellular genes that regulate diverse aspects of cell motility.

Human papillomaviruses (HPVs) are ubiquitous DNA viruses that infect cutaneous and mucosal epithelia. A subset of HPVs infects the female genital tract, to induce cervical lesions that can progress to malignancy in some women. DNA from HPVs can be found in >94% of cervical carcinomas (CaCx) worldwide; this strong association suggests that it might be possible to develop either prophylaxis or therapies for cervical neoplasia, based on the manipulation of human immune responses against HPVs. This review examines the current research into human immune responses against HPVs in CaCx and the potential impact of this research on human health.

The effectiveness of anti-cancer chemotherapy can be limited by acute suppression of the bone marrow (myelosuppression). There is also a risk of therapy-related secondary haematopoietic malignancy as well as acute and longer term effects in other tissues. Clinical strategies have been established to address some of these problems, particularly toxic effects on the bone marrow (acute myelotoxicity); however, there is still substantial scope for improving the management of chronic toxicity and mutagenicity to haematopoietic cells and collateral damage to non-haematopoietic cells during chemotherapy. In this review, we have discussed a novel strategy that involves the transfer and expression of drug-resistance functions into haematopoietic stem cells and more-mature blood progenitor cells, to overcome both the acute and long-term deleterious effects of anti-tumour treatment in bone marrow. The potential advantages of this approach include: (1) the in vivo selection of protected cell populations, which offers the possibility of intensification or escalation of chemotherapeutic drug doses; (2) a reduction in the frequency of therapy-related leukaemia and (3) tumour sensitisation to chemotherapy at the same time as haematopoietic protection.

The human leukocyte antigen class I allele HLA-B27 is a major histocompatibility complex (MHC) antigen that is strongly associated with the spondyloarthritic group of human rheumatic diseases, the most commmon of which is ankylosing spondylitis. Although the mechanism underlying this disease association remains unknown, numerous theories have been proposed. Much more is known of the natural role of HLA-B27 in binding and presenting antigenic peptides to T cells. The ‘arthritogenic peptide hypothesis’ suggests that the role of HLA-B27 in disease relates to its specificity for binding certain peptides. Recently, it has also been shown that HLA-B27 has an unusual cell biology and can adopt a novel homodimeric structure. In this review, a molecular model of the HLA-B27 homodimer is presented and the possible pathogenic significance of such a structure is discussed.

The past 20 years have seen rapid advances in the understanding of the biology of human cancers, and a large body of evidence now supports the idea that accumulated genetic changes underlie the development of neoplasia. In this article, we have reviewed the current research into the genetic bases of cancer and discussed the potential clinical applications of recent advances, with particular reference to the possibility of using molecular genetic tests for pre-symptomatic screening, clinical diagnosis and clinical staging. The possibility that the genetic profile of a tumour, its ‘molecular fingerprint’, will improve the ability of oncologists to predict tumour behaviour and thus help to determine optimum treatment has also been considered. Although the potential for the application of molecular genetic technologies is enormous, these technologies have yet to be subjected to rigorous evaluation in a clinical setting, and much work needs to be done before they are adopted for use in routine clinical care.

An international consortium of genome centres, advanced development teams and funding agencies has begun the task of sequencing the genome of the parasite Plasmodium falciparum, the most important cause of human malaria. Sequencing is proceeding chromosome by chromosome, and the annotated sequence of chromosome 2 is nearly finished. With the continual release of sequence data as they are generated, malaria researchers have access to a steady stream of genomic sequences and will soon have the complete annotation of all of the estimated 5000–7000 P. falciparum genes. The task will then be how to best apply these data to the development of new anti-malarial drugs, vaccines and diagnostic tests. This review provides a brief overview of the Malaria Genome Sequencing Project and suggests potential directions for future malaria research.

The premise that there are genes that wield a strong influence on longevity has, until recently, not been a popular one and there has been no concerted effort to find such genes. However, the finding that single genes can have large effects on the lifespans of yeast, worms and flies raises the possibility that individual genes in mammals may similarly have relatively large effects on longevity. Recent advances in mammalian genetics, many associated with the large-scale efforts to sequence the human and mouse genomes, have accelerated the search for longevity genes, principally in mice. Here, we review results using animal models that have recently shed light on genes regulating longevity and ageing patterns. A large number of genetically defined strains of mice are available and this, together with their established history of use in genetic research and their relatively short lifespans, has made murine models particularly useful. We also review our own work in which genes regulating mouse lifespan and those regulating cell cycling of haematopoietic progenitor cells have been mapped to the same locations in the genome. These results suggest that some of the same genes affect both traits, and further suggest a cause-and-effect relationship between cumulative cell-cycle activity and longevity of an organism.

Infection with Entamoeba histolytica, the protozoan parasite that causes amoebic colitis and liver abscess, results in 34 million to 50 million symptomatic cases of amoebiasis (all illnesses caused by E. histolytica, including amoebic dysentery) worldwide each year, causing 40 thousand to 100 thousand deaths annually. As a result of accruing biochemical, genetic and immunological data, E. histolytica was re-defined in 1993 to recognise the existence of two morphologically identical but genetically distinct human parasites: E. histolytica, the aetiological agent of invasive intestinal and extraintestinal amoebiasis, and Entamoeba dispar, a non-pathogenic intestinal parasite. Because microscopy is unable to distinguish between these two organisms, it should no longer be relied upon to diagnose amoebiasis. Sensitive and specific molecular techniques that are able to distinguish E. histolytica from E. dispar have been developed recently; they include (1) the detection of an E. histolytica antigen using an enzyme-linked immunosorbent assay (ELISA), (2) the use of the polymerase chain reaction (PCR) to amplify amoebic DNA, and (3) the culture of stool samples followed by isoenzyme analysis. Of these three test methods, only antigen detection using ELISA can be performed rapidly and easily, making it the diagnostic test method of choice for clinical use in the developing world, where the morbidity and mortality caused by E. histolytica are greatest. However, the PCR method is a powerful tool for the genetic typing of different amoebic strains. Together these two methods should result in both improved clinical diagnosis and treatment of amoebiasis, and a greater understanding of the epidemiology of E. histolytica. Such knowledge will not only assist public health efforts to control amoebiasis, but also facilitate the careful testing of the anti-amoebic vaccines that are currently being developed.

Poliomyelitis is a paralytic disease of the motor neurones of the central nervous system, which is caused by poliovirus. The virus is transmitted by the faecal–oral route, and if virus replication is confined to the gut, it is harmless. Poliomyelitis is an ancient human disease, but was rare until the beginning of the 20th century, when children began to be exposed to the virus at older ages and were, therefore, no longer protected by maternal antibody, which had already been lost. Inactivated polio vaccines are increasingly being used in those countries in which poliomyelitis has been brought under control; however, live vaccines are still the most widely used types and the World Health Organization (WHO) have set the goal of using such vaccines to eliminate the wild-type virus throughout the world by the year 2000. Substantial progress has been made to this end; however, the strains of poliovirus that are used as vaccines are able to adapt rapidly to the human gut, losing their attenuated (weakened) character within a few weeks. Currently, there is urgent debate about the best method of stopping vaccination against poliomyelitis once the wild-type poliovirus has been eliminated completely, so that the vaccine-strain virus will also be eliminated. Proposed strategies include the abrupt cessation of vaccination with the live virus worldwide, followed by the optional use of inactivated vaccines for an appropriate period. Further information about both the epidemiology and the pathogenesis of the disease is required before an informed choice can be made. The topics covered in this article include a brief history of studies of the disease, its pathogenesis and its control by vaccination, the molecular biology of the live vaccines, which have been extremely successful in controlling poliomyelitis so far, and the concerns that are raised as the eradication of the wild-type virus approaches.

Patients with the autoimmune rheumatic disease systemic lupus erythematosus (SLE or ‘lupus’) develop a wide variety of clinical and serological manifestations including the presence of antibodies to double-stranded DNA (dsDNA), which are often diagnostic and potentially pathogenic. In this review, we have examined the links between the structure and function of anti-dsDNA antibodies, emphasising their clinical associations. We have also reviewed studies involving animal models, the analysis of human antibody sequences and studies of, and using, computer modelling and crystal structure.

Resistance to anti-cancer drugs (drug resistance) can be defined in the laboratory by the amount of anti-cancer drug that is required to produce a given level of cell death (drug response). Clinical drug resistance can be defined either as a lack of reduction of the size of a tumour following chemotherapy or as the occurrence of clinical relapse after an initial ‘positive’ response to anti-tumour treatment. Many studies of tumour samples do not directly measure drug resistance in the laboratory (because it is difficult to perform functional assays on tumour tissue); instead, key proteins or genes that are involved in particular mechanisms of drug resistance have been proposed as ‘markers’ of drug resistance. In this review, we have focused on the problems that can arise when attempts are made to relate the relevance of laboratory-identified molecular mechanisms of drug resistance to anti-cancer drug resistance that occurs in patients.

The term epilepsy encompasses a heterogeneous group of disorders, with a lifetime cumulative incidence of 3%. Genetic factors are thought to contribute to the aetiology in up to 60% of cases. Various molecular and cellular mechanisms give rise to epilepsy, and epilepsy genes fall into several distinct categories. They include genes in which mutations cause abnormal ion-channel function, disordered brain development, progressive neurodegeneration and disturbances of cerebral energy metabolism. In this review, we have focused on current understanding of the molecular genetic bases of human inherited epilepsies. Particular reference has been given to specific idiopathic epilepsies, neuronal migration disorders (cortical dysgeneses) and the progressive myoclonic epilepsies, and how information about this group of disorders might be used to develop new treatment strategies.

Osteoporosis is a common condition of men and women, which is characterised by an increase in bone fragility due to a reduction in the amount of bone tissue. Predisposition to osteoporosis is largely genetically determined, and it is likely that several genes, each having a small effect, are involved. Bone density is determined by the peak bone mass achieved, and the rate and timing of subsequent bone loss. Twin and family studies suggest that the genetic determinants of bone density in later life influence predominantly, but not exclusively, peak bone mass. Although many genes influence bone density in both males and females, at different skeletal sites and in different age groups, it is likely that the magnitude of individual genetic effects differs in different population subsets and in different environmental settings. Thus, weak to moderate genetic effects might be identified only in specific subsets of the population. Rapid advances in the field of human genetics during the past decade have greatly improved our chances of successfully identifying genes that are involved in complex genetic conditions such as osteoporosis, and ultimately might lead to the development of new diagnostic and predictive tests as well as novel treatments for this condition. In this review, we have outlined the methods that are currently being employed to identify osteoporosis genes and also the progress that has been made to date in this field.

Gene therapy continues to offer much hope for the future treatment of a variety of clinical conditions. The development of tailored, novel gene transfer vectors will improve the efficiency and stability of therapeutic gene expression in the many settings of gene therapy. In the context of tissue and organ transplantation, gene therapy is being harnessed to prevent the acute and chronic rejection of transplanted tissues by introducing either new genes that are important in preventing rejection (e.g. co-stimulatory blocking molecules or immunosuppressive cytokines) or antisense nucleic acids to block the production of rejection-associated molecules such as adhesion molecules. The delivery of genes by gene therapy vectors that encode foreign donor antigens (alloantigens) might also be an effective means of inducing donor-specific unresponsiveness (immunological tolerance) in the recipient, perhaps eliminating the requirement for potentially harmful whole-body immunosuppression.

T lymphocytes (T cells) play critical roles in the regulation of immune responses, and are responsible for mediating many of the effector mechanisms of the immune system. For this reason, there has always been a need for assays to measure accurately the activity of populations of T cells, both in model (animal) systems and in humans. The expansion of the biotechnology industry has led to a dramatic increase in the number of novel immunotherapeutics that are being developed for the treatment of cancer, autoimmune disorders and infectious diseases. This increase in activity in the field of immunotherapy, coupled with the expense of clinical trials, has led to renewed interest in methods that accurately assess T-cell function, as researchers seek to maximise the amount of information that can be obtained from each clinical study. Assessing the quantitative and qualitative nature of a T-cell response, for example following vaccination or immunosuppressive therapy, can provide valuable information about the efficacy of a treatment, in place of a clinical endpoint. This article reviews some of the established methods that are used to monitor human T-cell activity, and describes some new approaches that are in development to increase the speed, sensitivity and relevance of such methods.

Human herpesvirus 6 (HHV-6) is a T-lymphotropic herpesvirus, which infects almost all children by the age of two years and persists lifelong. Two distinct variants of HHV-6, HHV-6A and HHV-6B, have been described, and the latter has been shown to be a common cause of acute febrile illnesses in young children, including exanthem subitum (roseola). HHV-6 has also been associated with a number of neurological disorders, including encephalitis and seizures, and the virus has been postulated to play a role in acquired immunodeficiency syndrome (AIDS), multiple sclerosis (MS) and chronic fatigue immunodeficiency syndrome (CFIDS). This review provides a critical summary of research conducted on HHV-6.

Human herpesvirus 7 (HHV-7) is a recently described T-lymphotropic herpesvirus, which infects almost all children by the age of three years and persists lifelong, with the shedding of infectious virus in saliva. HHV-7 is similar to human herpesvirus 6 (HHV-6) in its genetic content and in many of its biological properties, which include the ability to cause at least some cases of exanthem subitum (roseola). Despite these similarities, important differences between HHV-7 and HHV-6 exist, including the fact that HHV-7 binds to the cellular CD4 molecule and uses this protein as a necessary component of its receptor, while HHV-6 binds to a different (and unknown) receptor. Furthermore, the pathogenesis and sequelae of HHV-7 infection remain very poorly understood. This review provides a critical summary of research on HHV-7.

Malaria remains one of the biggest health problems in large parts of the world. In sub-Saharan Africa alone, it is currently estimated that there are more than 150 million clinical cases annually, and that about 2 million people die from the disease every year. The bulk of malaria-related morbidity and mortality in an endemic setting (malaria is regularly found) is concentrated in children below the age of five years, and the increasing resistance to infection and disease with age is conventionally thought to reflect a slow and gradual acquisition of protective immunity. Many recent and comprehensive reviews of malarial immunity exist; rather than attempting to add another, this review summarises some of the recent evidence on how protective immunity is acquired in humans and what precipitates clinical disease, specifically as it relates to populations living in areas where the disease is endemic. It is becoming increasingly clear that naturally acquired protective immunity depends largely on responses directed against highly variable parasite antigens. This implies that a successful blood-stage vaccine against this disease must be able to either induce protective responses against many of these variants, or artificially initiate protective immune responses that do not normally occur following natural exposure to the parasites. Such protective immune responses might either rely on a different immunological mechanism, or be directed against other antigens, other than those seen in naturally acquired protective immunity. It remains to be seen whether it will be possible to induce protective responses such as these by ‘artificially’ immunising humans.

During the past 30 years, organ transplantation has developed from a highly experimental procedure into an important part of routine clinical practice. This is reflected by the fact that graft survival times, which were once considered in terms of days or weeks, are now measured in terms of years or decades, with enormous corresponding benefits for the patient. Much of this improvement is due to the development of sophisticated immunosuppressive drugs that inhibit the rejection response mediated by the immune system of the recipient. However, almost without exception, all of the grafts that are transplanted from one genetically disparate individual to another are eventually rejected. The Holy Grail in transplantation is the development of protocols that lead to transplantation tolerance and provide stable graft function without long-term drug therapy. In this article, we have discussed the need for alternatives to current immunosuppression and reviewed the results of animal models, which suggest that long-term stable tolerance is an achievable goal.