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Category Archive for 'Infection'

Epistasis refers to the influence of one genomic mutation or variant on the phenotypic effects of another mutation or variant.  Based on available evidence and theory, this phenomenon has a major influence on evolutionary trajectories for organisms of all sorts.  The role of epistasis has been studied primarily in the context of adaptive evolutionary change.  […]

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Toxoplasma gondii is an intracellular protozoan parasite that infects many different vertebrate species asexually and undergoes a sexual cycle after infecting cats (http://www.cdc.gov/parasites/toxoplasmosis/, 2013).  Parasite oocysts are potentially introduced into the human environment in cat feces.  T. gondii is of interest in clinical medicine because humans can serve as accidental intermediate hosts when they ingest […]

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A careful reading of the review of fever in “Fever: Friend or Foe?”, reveals the embarrassing deficiency in medical science’s understanding of how fever, much less anorexia, functions in infection. Since fever (as well as anorexia and other components of the acute-phase response) is induced by our own cytokines, it is virtually axiomatic that fever […]

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A central focus of recent research aimed at developing a vaccine for HIV-1 is the identification of potent broadly-neutralizing antibodies (bNAbs).  Due to work from several laboratories, many such antibodies have now been identified, produced in quantity as monoclonal antibodies, and characterized with respect to key properties such as epitope specificity, affinity for the corresponding […]

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Currently, I am on vacation near the beach in South Carolina.  Consequently, I have opted for a topic that is bit different than the majority of my monthly commentaries in that it focuses not on a recent original report but instead on a conceptual point made in a book over thirty years ago.  Nevertheless, after […]

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The term “genetic code” is associated with a measure of ambiguity.  For molecular biologists, “genetic code” has historically referred to a table that provides for each messenger RNA ribonucleotide triplet the corresponding amino acid that is incorporated into the growing end of a nascent polypeptide chain, i.e. the translation from RNA sequence to protein sequence.  […]

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  Recently, a valued friend and scientific colleague of mine (Jonathan Yewdell of the NIAID in Bethesda) made me aware of a netcast (http://www.twiv.tv/) and associated blog (http://www.virology.ws/) relating to virology.  The originator of both is Vincent Racaniello, a well-known and highly regarded virologist and professor of microbiology at Columbia University.  Dr. Racaniello currently happens […]

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In 1996, Dean et al. (Science), demonstrated that a loss-of-function allele (CCR5Δ32) encoding a version of the chemokine receptor, CCR5, confers very substantial resistance to infection with HIV-1 in the homozygous state and slows progression in the heterozygous state.  Given the relatively recent origin of HIV-1, this finding raised the question of what source of […]

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A major problem confronting physicians, nurses, and other hospital personnel is transmission of pathogens among inpatients or between medical personnel and inpatients (in either direction).  A crucial component in efforts to control such infectious outbreaks in hospital wards is determining whether particular cases are linked by instances of person-to-person transmission.  Standard methods of analysis involve […]

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A paper recently appearing in Science (Näsvall et al. 2012) offers a new insights into the mechanisms by which gene duplication can lead to new genes, gene products, and functions.  The new scheme is termed the innovation-amplification-divergence (IAD) model. 

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Influenza A viruses continue to be of enormous interest to biomedical researchers and clinicians alike.  In addition to the annual influenza epidemics, which have been inferred to cause substantial excess mortality, there is the ever-present threat of a global pandemic due to several features of influenza virus biology.  A high mutation rate associated with a […]

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There have been claims that variations in the composition of the intestinal flora influence individual health going back at least to the early years of the 1900s.  Late in his career, Ilya Mechnikov, co-receipient of the Nobel Prize for Physiology or Medicine in 1908 (along with Paul Ehrlich) and a pioneer in the study of […]

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The new tools for determining nucleotide sequences for whole genomes can sometimes present a problem of data analysis: How can mutations that influence important phenotypes be distinguished from mutations that may be of minimal or no impact on fitness, so-called passenger mutations that arise and persist primarily by chance and can greatly outnumber adaptive genetic […]

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As noted in my last post, the selective advantage of heterozygosity for the sickle allele at the beta-globin locus has been known since Allison’s report in 1954 (Lancet).  Nevertheless, a plausible and detailed mechanism to account for the protective effect of an allele that is typically highly deleterious when homozygous has not been forthcoming until […]

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Infections by multiple strains of the same pathogen—coinfections or superinfections—raise interesting and challenging problems. From the perspective of the pathogen, superinfection is a trade-off: superinfecting strains will compete with resident strains for host resources but for many pathogens, coinfection or superinfection may be necessary for sexual recombination or genetic exchange and multiple pathogen strains may […]

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Among the most pressing global public health problems at present is the AIDS epidemic.  While it is clear that chemotherapy and behavioral interventions have much to offer in limiting the spread of infections by the causative virus, HIV-1, interest in developing a vaccine remains strong.  Immunization would potentially provide a relatively cost-effective and scalable approach […]

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In the May 26 (2011) issue of Nature, Vijaykrishna et al. address patterns of evolution and transmission exhibited by swine influenza A viruses (SwIV) isolated from pigs beings slaughtered in Hong Kong between May 1998 and January 2010.  Although the focus of the study is on viruses that circulate in swine, this study is relevant […]

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In his essay (2011) on the history of Darwinian (or evolutionary) medicine, Jonathan Fuller describes potentially relevant interests and insights that preceded the famous paper by Nesse and Williams (1991) that is widely regarded as having catalyzed the resurgence of interest in applying evolutionary concepts and principles to medicine.  For example, the author describes aspects […]

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Among human pathogens, Streptococcus pneumoniae holds an especially prominent place in the history of biomedical investigation.  Griffith (1928) described the transforming principle, a soluble substance released by dead, virulent pneumococci that could render living avirulent pneumococci able to effectively kill a mouse.  Oswald Avery’s commitment to curing pneumococcal pneumonia (http://profiles.nlm.nih.gov/ps/retrieve/Narrative/CC/p-nid/37) led him and his collaborators […]

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In the early years of the last century, Paul Ehrlich coined the term “magic bullet” to indicate a therapeutic agent that targeted an infectious agent or tumor with exquisite specificity (Schwartz, 2004).  He was inspired by his work with antibodies to imagine a future age of impressively discriminating and extremely effective drugs.  Perhaps the class […]

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