The resistance of numerous bacterial pathogens of major clinical significance to many or all relevant antibiotics has become a public health threat of such magnitude that the latest U.N. General Assembly decided to hold a one-day meeting to address the issue (1). Recently, there has been substantial coverage of this issue in the general media, including by major news organizations such as the New York Times, National Public Radio, and the Washington Post (2-4). What the stories running in these outlets often fail to adequately emphasize is that the bacterial pathogens develop resistance to antibiotics by an evolutionary process. Furthermore, the solution to the problem of effectively treating these microbial agents of human disease requires not merely producing more antibiotics but also gaining deeper insights into the evolutionary processes by which antibiotic resistance comes into being and is transmitted between bacteria. In this context, a new study (5) from the laboratory of Roy Kishony, who is affiliated with both Technion and Harvard, is a novel and welcome advance in ways to study the evolution of bacterial antibiotic resistance and potentially to communicate about this process to the broader public.
Author: Neil Greenspan (Page 1 of 9)
In a recent blog post (http://evmed.asu.edu/blog/evolutionary-medicine-top-ten-questions), Randy Nesse suggests that the presentations and discussions at the second annual conference of the International Society for Evolution, Medicine, and Public Health (ISEMPH) were
“… instigated 25 years ago as George Williams and I discussed and grappled with how evolution could be useful for medicine, and what to call the enterprise.”
In her chapter (Bentley, 2016) introducing the just published book, “Evolutionary Thinking in Medicine: from Research to Policy and Practice,” the author acknowledges activity that can be considered evolutionary medicine in the years prior to 1991 but confines it to before roughly 1940. Following the end of World War II, Professor Bentley finds little to no evidence of significant work in the field until the 1990s. Unfortunately, these claims disregard substantial numbers of evolution-related studies that either influenced fundamental understanding of human health and disease or affected medical practice.
Earlier this year I was afforded the opportunity to hear Paul Schimmel, of the Scripps Research Institute, lecture on aminoacyl transfer RNA (tRNA) synthetases (aaRSs), a topic on which he is a leading authority. These enzymes attach particular amino acids to specific tRNA molecules for incorporating those amino acids into growing polypeptide chains by ribosomes. The basic features of these enzymes that contribute to the fundamental function of translating messenger RNAs (mRNAs) are conserved from humans through the most evolutionarily primitive single-celled organisms. Thus these enzymes might be presumed to correspond to prototypical vegetative gene products, i.e., gene products necessary for essential cellular functions that have little to do with more recently evolved functions beyond protein synthesis. So, it was extremely interesting to learn that in organisms that arose later in evolution there are other functions, unrelated to aminoacylation of tRNAs, associated with many of the aaRSs. These functions of aaRSs are summarized by Guo and Schimmel (Nature Chem. Biol., 2013).
Identifying broadly neutralizing antibodies against infectious agents such as influenza A viruses, HIV, and Plasmodium falciparum that display impressive degrees of antigenic variation is a major focus of investigators developing therapeutics and vaccines for pathogens of importance in public health (Corti and Lanzavecchia, 2013). In a previous post, I discussed one study (Klein et al., 2013) illustrating the sorts of unanticipated types of mutations found for broadly neutralizing antibodies against HIV. Lanzavecchia and colleagues have now identified antibodies reactive with antigens encoded by different isolates of Plasmodium falciparum and expressed on infected erythrocytes (Nature, 2015). They find an unexpected source for the heavy chain variable domain amino acid sequences that confer the broad anti-malarial reactivity against proteins in the RIFIN family.
Clinical organ transplantation is now a large medical enterprise, with more than 29,000 organ transplants performed in 2014 in the United States alone (https://www.unos.org/data/transplant-trends/#transplants_by_organ_type+year+2014). Nevertheless, the number of organ donors is insufficient to meet the demand for new organs. For example, in the U.S. during 2014, there were 17,104 kidney transplants but 101,035 individuals on the waiting list for such transplants. Therefore, a recent study in Science (Yang et al., 2015) offers an important proof of principle for a necessary but not necessarily sufficient step on the path to safely using pig organs to substitute for failing human organs.
It would be hard to identify an approach to cancer treatment that has received more attention recently than anti-checkpoint therapy (Pollack, 2015). This strategy for eliminating tumor cells is based on interfering with one or another pathway that inhibits the initial activation or functions of T cells, such as CD8+ cytotoxic T cells (CTL). Activated tumor-specific CTL can directly kill their targets. However, if copies of the T-cell surface molecule, PD-1, are bound by their physiological ligands on tumor cells, either PD-L1 or PD-L2, or other cells the ability of the T cell to perform its functions is substantially reduced. A report published in Science (2015) by Rizvi et al. last month addresses the question of whether tumor mutation burden correlates with response to anti-checkpoint therapy for non-small cell lung cancer (NSCLC).