Molecular epidemiology of infectious diseases

Data on molecular epidemiology of bacterial infections is summarized. The term definitions of "molecular epidemiology", "taxonomic species" are given, the limits and species structure of prokaryotes are described. The basic mechanisms of the prokaryotes variability in the epidemic process, as well as the possibilities and limitations of microbiological, molecular-biological and population--genetic typing methods, are characterized. The tactics of molecular-biological studies in analyzing the population structure on the global, regional and local levels is presented. The economic effectiveness of measures taken with due consideration of information on the clonal structure of causative agents of hospital infections is shown.     

The role of infectious diseases in biological conservation

Recent increases in the magnitude and rate of environmental change, including habitat loss, climate change and overexploitation, have been directly linked to the global loss of biodiversity. Wildlife extinction rates are estimated to be 100–1000 times greater than the historical norm, and up to 50% of higher taxonomic groups are critically endangered. While many types of environmental changes threaten the survival of species all over the planet, infectious disease has rarely been cited as the primary cause of global species extinctions. There is substantial evidence, however, that diseases can greatly impact local species populations by causing temporary or permanent declines in abundance. More importantly, pathogens can interact with other driving factors, such as habitat loss, climate change, overexploitation, invasive species and environmental pollution to contribute to local and global extinctions. Regrettably, our current lack of knowledge about the diversity and abundance of pathogens in natural systems has made it difficult to establish the relative importance of disease as a significant driver of species extinction, and the context when this is most likely to occur. Here, we review the role of infectious diseases in biological conservation. We summarize existing knowledge of disease-induced extinction at global and local scales and review the ecological and evolutionary forces that may facilitate disease-mediated extinction risk. We suggest that while disease alone may currently threaten few species, pathogens may be a significant threat to already-endangered species, especially when disease interacts with other drivers. We identify control strategies that may help reduce the negative effects of disease on wildlife and discuss the most critical challenges and future directions for the study of infectious diseases in the conservation sciences.     

Modeling human mitochondrial diseases in flies

Human mitochondrial diseases are associated with a wide range of clinical symptoms, and those that result from mutations in mitochondrial DNA affect at least 1 in 8500 individuals. The development of animal models that reproduce the variety of symptoms associated with this group of complex human disorders is a major focus of current research. Drosophila represents an attractive model, in large part because of its short life cycle, the availability of a number of powerful techniques to alter gene structure and regulation, and the presence of orthologs of many human disease genes. We describe here Drosophila models of mitochondrial DNA depletion, deafness, encephalopathy, Freidreich's ataxia, and diseases due to mitochondrial DNA mutations. We also describe several genetic approaches for gene manipulation in flies, including the recently developed method of targeted mutagenesis by recombinational knock-in.     

The role of tetraspanins in the pathogenesis of infectious diseases

Tetraspanin proteins on host cells are involved in the pathogenesis of infectious diseases at different stages. In this review, we will focus on tetraspanins expressed in the immune system and the role they play in the defense to viral, bacterial, parasitic and fungal infections.     

The role of interleukin-13 in infectious diseases and allergy

Cytokines, also referred to as interleukins, are the major orchestrators of host defence processes, and, as such, are involved in insults, repair and restoration of tissue homeostasis. This review summarises recent findings on and emerging models of the biological roles of the double-edged sword interleukin-13 (IL-13), which have been principally obtained from studies in mice that are deficient for IL-13, or its components. IL-13-mediated functions not only contribute to the susceptible phenotype in Leishmania major infection but also seem to play a protective role in chronic leishmaniasis. Moreover, IL-13 plays a key protective role in the expulsion of helminths from the gut while also actively contributing to the pathology in schistosomiasis. In allergic asthma, IL-13 has also been found to be a key factor. Therapeutic administration of an IL-13 inhibitor in mice successfully prevents both the allergic disease phenotype and schistosoma egg-induced lung pathology. If this scenario holds true in humans, we soon may have an efficient drug for treatment of IL-13-mediated diseases.     

Linking within- and between-host dynamics in the evolutionary epidemiology of infectious diseases

Nested models (also called embedded models) explicitly link dynamical processes that occur at different scales. Recently there has been considerable interest in linking within- and between-host levels of disease dynamics in the study of pathogen evolution. Here we review the extent to which these nested models have increased our understanding of pathogen evolution. We suggest that, although such models have been useful for determining the nature of tradeoffs between epidemiological parameters and for evaluating the consequences of conflicting selection pressures at different scales, the vast majority of previous results could likely have been obtained without the use of nested models per se. Nevertheless, these models have proven very useful through their highlighting of the importance of within-host disease dynamics on pathogen evolution.     

The role of glycosylases of the base excision DNA repair in pathogenesis of hereditary and infectious human diseases

DNA glycosylases are enzymes that initiate base excision repair, a process of removal of damaged bases from the cellular DNA. Recent data show that variants of two human DNA glycosylases, MUTYH and OGG1, are associated with an increased risk of cancer. In addition, activities of various DNA glycosylases have been implicated in protection of humans from neurodegenerative diseases, immune disorders and viral infections. On the other hand, DNA glycosylases from pathogenic microorganisms help them to avoid the host defensive systems. Thus, DNA glycosylases represent both potential therapeutic agents and drug targets.     

The divergent role of tumor necrosis factor receptors in infectious diseases

Tumor necrosis factor (TNF) receptor types 1 and 2 are broadly expressed by most cell types and are activated by binding of either TNF or lymphotoxin-beta. TNF receptor-mediated immune reactions are critically important in the pathogenesis and control of a variety of infections caused by bacteria, viruses, protozoa, and fungi. This review summarizes recent findings on the role of TNF receptors in infectious diseases and discusses the divergent functions of these receptors in immune responses.     

Impact of vaccination on the infectious diseases epidemiology: example of pertussis

Several vaccines are now routinely used since fifty years in different developed countries. Their principal impact has been to decrease morbidity and mortality of the infectious diseases they are targeting. One disease, smallpox, is eradicated, poliomyelitis will be soon, diphteria is controlled in several countries but pertussis is still endemic although an efficacious vaccine was used. Why? Pertussis is an example of an infection for which the immunity of the population has changed after the introduction of generalized vaccination with killed whole cell pertussis vaccines, from a natural immunity due to infection to different types of vaccine-induced immunity. These different types of immunity have changed the protection against infection, disease and transmission. The impact of the generalized vaccination in a human population has been an important change in the epidemiology of the disease. In fact, a child-to-child transmission observed before the introduction of vaccination is now replaced by an adolescent-adult to infant transmission. The major consequence is an increase in the mortality and morbidity in non vaccinated infants mostly contaminated by their parents. Researches undertaken on the agent of the disease, the bacterium, Bordetella pertussis, conducted to the development of subunits vaccines, efficacious and better tolerated by infants than whole-cell vaccines. Many developed countries decided to change vaccines but also to add vaccine boosters for adolescents and adults in order to stop the transmission of the disease to infants. However, even after 15 years of studies in many countries, pertussis is still underestimated in adults and generalized adult vaccination remains difficult. The new goal now is to give information to medical students and health care workers in general in order to increase adolescent and adult's vaccination coverage.     

Molecular biology and the diagnosis, epidemiology and pathogenesis of infectious diseases

Abstract In this short review, the impact of molecular biology on microbiology in general is described. Specifically, molecular biology is increasingly enlarging the available choice of methods for the diagnosis of microbial disease. In situ hybridization seems to be a particularly promising procedure. In epidemiology, an interesting facet is the high mutation rate of RNA viruses. In pathogenesis, molecular biology will help to elucidate pathways of infection and the targeting of pathogenic macromolecules within the cell and within an organism.     

Molecular biology and the diagnosis, epidemiology and pathogenesis of infectious diseases

In this short review, the impact of molecular biology on microbiology in general is described. Specifically, molecular biology is increasingly enlarging the available choice of methods for the diagnosis of microbial disease. In situ hybridization seems to be a particularly promising procedure. In epidemiology, an interesting facet is the high mutation rate of RNA viruses. In pathogenesis, molecular biology will help to elucidate pathways of infection and the targeting of pathogenic macromolecules within the cell and within an organism.     

On the role of reinfection in the transmission of infectious diseases

We introduce a spatial stochastic model for the spread of tuberculosis. After a primary infection, an individual may become sick (and infectious) through an endogenous reinfection or through an exogenous reinfection. We show that even in the absence of endogenous reinfection an epidemic is possible if the exogenous reinfection parameter is high enough. This is in sharp contrast with what happens for a mean field model corresponding to our spatial stochastic model.     

The pig: a model for human infectious diseases

An animal model to study human infectious diseases should accurately reproduce the various aspects of disease. Domestic pigs (Sus scrofa domesticus) are closely related to humans in terms of anatomy, genetics and physiology, and represent an excellent animal model to study various microbial infectious diseases. Indeed, experiments in pigs are much more likely to be predictive of therapeutic treatments in humans than experiments in rodents. In this review, we highlight the numerous advantages of the pig model for infectious disease research and vaccine development and document a few examples of human microbial infectious diseases for which the use of pigs as animal models has contributed to the acquisition of new knowledge to improve both animal and human health.