Study of the role of CCR5 in a mouse model of intranasal challenge with Yersinia pestis

Addressing the dark matter of gene therapy: technical and ethical barriers to clinical application

Gene therapies for genetic diseases have been sought for decades, and the relatively recent development of the CRISPR/Cas9 gene-editing system has encouraged a new wave of interest in the field. There have nonetheless been significant setbacks to gene therapy, including unintended biological consequences, ethical scandals, and death. The major focus of research has been on technological problems such as delivery, potential immune responses, and both on and off-target effects in an effort to avoid negative clinical outcomes. While the field has concentrated on how we can better achieve gene therapies and gene editing techniques, there has been less focus on when and why we should use such technology. Here we combine discussion of both the technical and ethical barriers to the widespread clinical application of gene therapy and gene editing, providing a resource for gene therapy experts and novices alike. We discuss ethical problems and solutions, using cystic fibrosis and beta-thalassemia as case studies where gene therapy might be suitable, and provide examples of situations where human germline gene editing may be ethically permissible. Using such examples, we propose criteria to guide researchers and clinicians in deciding whether or not to pursue gene therapy as a treatment. Finally, we summarize how current progress in the field adheres to principles of biomedical ethics and highlight how this approach might fall short of ethical rigour using examples in the bioethics literature. Ultimately by addressing both the technical and ethical aspects of gene therapy and editing, new frameworks can be developed for the fair application of these potentially life-saving treatments.

CCR5 and CCR5Δ32 in bacterial and parasitic infections: Thinking chemokine receptors outside the HIV box

The CCR5 molecule was reported in 1996 as the main HIV-1 co-receptor. In that same year, the CCR5Δ32 genetic variant was described as a strong protective factor against HIV-1 infection. These findings led to extensive research regarding the CCR5, culminating in critical scientific advances, such as the development of CCR5 inhibitors for the treatment of HIV infection. Recently, the research landscape surrounding CCR5 has begun to change. Different research groups have realized that, since CCR5 has such important effects in the chemokine system, it could also affect other different physiological systems. Therefore, the effect of reduced CCR5 expression due to the presence of the CCR5Δ32 variant began to be further studied. Several studies have investigated the role of CCR5 and the impacts of CCR5Δ32 on autoimmune and inflammatory diseases, various types of cancer, and viral diseases. However, the role of CCR5 in diseases caused by bacteria and parasites is still poorly understood. Therefore, the aim of this article is to review the role of CCR5 and the effects of CCR5Δ32 on bacterial (brucellosis, osteomyelitis, pneumonia, tuberculosis and infection by Chlamydia trachomatis) and parasitic infections (toxoplasmosis, leishmaniasis, Chagas disease and schistosomiasis). Basic information about each of these infections was also addressed. The neglected role of CCR5 in fungal disease and emerging studies regarding the action of CCR5 on regulatory T cells are briefly covered in this review. Considering the "renaissance of CCR5 research," this article is useful for updating researchers who develop studies involving CCR5 and CCR5Δ32 in different infectious diseases.

Modeling Pneumonic Plague in Human Precision-Cut Lung Slices Highlights a Role for the Plasminogen Activator Protease in Facilitating Type 3 Secretion

Pneumonic plague is the deadliest form of disease caused by Yersinia pestis Key to the progression of infection is the activity of the plasminogen activator protease Pla. Deletion of Pla results in a decreased Y. pestis bacterial burden in the lung and failure to progress into the lethal proinflammatory phase of disease. While a number of putative functions have been attributed to Pla, its precise role in the pathogenesis of pneumonic plague is yet to be defined. Here, we show that Pla facilitates type 3 secretion into primary alveolar macrophages but not into the commonly used THP-1 cell line. We also establish human precision-cut lung slices as a platform for modeling early host/pathogen interactions during pneumonic plague and solidify the role of Pla in promoting optimal type 3 secretion using primary human tissue with relevant host cell heterogeneity. These results position Pla as a key player in the early host/pathogen interactions that define pneumonic plague and showcase the utility of human precision-cut lung slices as a platform to evaluate pulmonary infection by bacterial pathogens.

Paleogenetics and Past Infections: the Two Faces of the Coin of Human Immune Evolution

With the advent of next-generation sequencing, paleogenetics has considerably expanded over the past few years and notably encompassed the characterization of the genomes of archaic humans who lived more than 30,000 years ago. These paleogenetics investigations have revealed that admixture between modern and archaic humans occurred, with Neanderthals having contributed to 1.5% to 2.1% of modern Eurasian genomes, and Denisovans to 3% to 6% of modern Melanesian genomes and to approximately 0.2% of modern Asian genomes. Although these contributions are modest, they played a major role in shaping immune gene families, such as the HLA class I genes, for which the archaic alleles now represent more than 50% of the alleles in Europe and Asia. Such a high frequency is consistent with these archaic HLA class I variants having been positively selected because of their protective effect against contagious and devastating epidemics, such as those due to the plague agent Yersinia pestis or to Mycobacterium tuberculosis, which is responsible for deadly tuberculosis. While the exact nature of the infectious agents that contributed to the selection of the archaic variants is unknown, we are entering an exciting period in which paleogenetics and paleomicrobiology data can be integrated to generate a clearer picture of how the immune system of modern populations was shaped and the role admixture and epidemics have played in such evolutions.

Understanding the persistence of plague foci in Madagascar

Plague, a zoonosis caused by Yersinia pestis, is still found in Africa, Asia, and the Americas. Madagascar reports almost one third of the cases worldwide. Y. pestis can be encountered in three very different types of foci: urban, rural, and sylvatic. Flea vector and wild rodent host population dynamics are tightly correlated with modulation of climatic conditions, an association that could be crucial for both the maintenance of foci and human plague epidemics. The black rat Rattus rattus, the main host of Y. pestis in Madagascar, is found to exhibit high resistance to plague in endemic areas, opposing the concept of high mortality rates among rats exposed to the infection. Also, endemic fleas could play an essential role in maintenance of the foci. This review discusses recent advances in the understanding of the role of these factors as well as human behavior in the persistence of plague in Madagascar.

CCR5 polymorphism and plague resistance in natural populations of the black rat in Madagascar

Madagascar remains one of the world's largest plague foci. The black rat, Rattus rattus, is the main reservoir of plague in rural areas. This species is highly susceptible to plague in plague-free areas (low-altitude regions), whereas rats from the plague focus areas (central highlands) have evolved a disease-resistance polymorphism. We used the candidate gene CCR5 to investigate the genetic basis of plague resistance in R. rattus. We found a unique non-synonymous substitution (H184R) in a functionally important region of the gene. We then compared (i) CCR5 genotypes of dying and surviving plague-challenged rats and (ii) CCR5 allelic frequencies in plague focus and plague-free populations. Our results suggested a higher prevalence of the substitution in resistant animals compared to susceptible individuals, and a tendency for higher frequencies in plague focus areas compared to plague-free areas. Therefore, the CCR5 polymorphism may be involved in Malagasy black rat plague resistance. CCR5 and other undetermined plague resistance markers may provide useful biological information about host evolution and disease dynamics.