Friday, 6 April 2012

Genetics of Infectious Diseases

In today’s society, we all can accept that we will get sick at multiple stages in our lives. But what if they way we handling sickness for better or worse was coded into our genes? Scientists around the globe have been working on case studies, trying to identify which genes help us prevent sickness. These genes can be tracked through the population to certain loci points (Hill, 2012). As you would expect, these studies are finding connection between people’s ability to hold off diseases and natural selection.

Research like this has been continuing over many decades with one of the most notable feats occurring in the 1950’s (Allison, 1954). In this decade it was found that a blood group with a special haemoglobin variant was useful for protection against malaria. An important thing to take away from this though is that not everyone will have this variant; a host’s protection will depend of said host’s genes  (Arevalo-Herrera, 2005).

Scientists are approaching this problem by looking at the genes on fraternal and identical twins, thus allowing them to examine the latter in greater detail (Gedda, 1984). By conducting this study, it has been found that a greater harmony between the identical twins then with the fraternal ones (Newport et al, 1989).
While we look at these results and examine our genes closely, it is important to also remembering that we may have genes protecting us from diseases that have died out already (Grossman et al, 2010). This may affect the result received as one cannot perform a case study on an extinct disease, thus making it harder for that gene to be tracked to a certain loci. Due to these genes floating around, signals that scientists are looking for may be weakened as the pathogen interacts with host genomes. This has the potential to mess up some calculations  (Sabeti, 2007).
 In theory, a scientist would want non-selected markers in the case study; however, natural selection has rendered each of us with different variants making this a little trickier. What is good about this though is that said gene can be traced back through the population to a loci point (Sanchez-Mazas, 2011).
While they are trying, it is almost impossible to do all pathogens in one go. Hence the main diseases that are being investigated are malaria, tuberculosis, HIV and leprosy.  Performing to best in terms of results is leprosy. It has proven the most successful in tracing back through the population (Mira et al, 2004).

A change has taken place over the last decade in research regarding infectious disease susceptibility. These changes have forwarded advances in human genomics, allowing for a greater rate of progression with no signs of slowing down.  Amazing discoveries have been identified through this research revealing patterns between host genes and those on the infectious pathogens, even coming down through natural selection. It is only now that a true understanding between the challenges faced by pathogens and a long term need to accommodate with the microbial world is coming through.

Tim Bartley

Works Cited
Allison, A. C. (1954, - -). Protection afforded by sickle-cell trait against subtertain malaria infection. Br. Med. J., pp. 290-294.
Arevalo-Herrera, M. e. (2005). Immunogenicity and protective efficacy of recombinant vaccine based on the receptor-binding domain of the Plasmodium vivax Duffy binding protein in Aotus monkeys. Am. J. Trop. Med., pp. 25-31.
Gedda, L. e. (1984). Heredity and infectious diseases: A twin study. Acta Genet. Med. Gemellol (Roma) 33, pp. 497-500.
Grossman, S. R. (2010). A composite of multiple signals distinguishes causal variants in regions of positive selection. Science 327, pp. 883-886.
Hill, A. V. (2012, March 16th). Evolution, revolution and heresy in the the genetics of infecious diseases susceptibility . The Royal Society , pp. 840-849.
Newport, M. J.-A. (2004). Genetic regulation of immune responses to vaccines in early life. Genes Immun, 5., pp. 122-129.
Sabeti, P. C. (2007). Genome-wide detection and characterization of positive selection in human populations. Nature 449, pp. 913-918.
Sanchez-Mazas, A. e. (2011). Immunogenetics as a tool in anthropological studies. Immunology 133., pp. 143-164.

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