I wanted to address the question we had in class about how superantigens are beneficial for Group A Streptococcus (GAS) if this causes a huge increase in cytokines and even cytokine storm, often killing a patient. There is very little literature explaining this question, but I did find a study that looked at the levels for transcripts expressed by GAS in human blood to better understand this problem. The paper suggests that the release of the superantigens may be due to the environment the bacterium is in. The main issue with this study and others is that it is difficult to mimic the exact environment in humans the bacterium lives in. Also, the persons genetics makes the environment different person to person.
I do have a few ideas from all the literature and again these are just ideas nothing FACT. If the release of cytokines causes vasodilation this may allow easier access for the bacterium to travel in its host leading to better infection. Also, in nature if you kill the host this may allow the bacterium to infect other species. Since you have a mass of food any predator that comes along to eat "you" may be infected with this bacterium. I think that another question that should be asked is "is this side effect of the superantigen more prevalent today than in the past, if so why?"
Anyways, I do apologize that I could find the definite answer. The truth is...... no one knows.
Group A Streptococcus transcriptome dynamics during growth in human blood reveals bacterial adaptive and survival strategies.
Graham MR, Virtaneva K, Porcella SF, Barry WT, Gowen BB, Johnson CR, Wright FA, Musser JM.
Am J Pathol. 2005 Feb;166(2):455-65.
- PMID:
- 15681829
That is a very good point and I was having the same question in my mind as well. In my opinion I would think that it would be more prevalent today with all the sorts of drugs and therapy treatments available out there but I would also think that over all the years "evolution" certainly would play a major role in this as well in both the host as well as the bacterium...
ReplyDeleteAlso another point is maybe if other species are more prone or adaptive to them... who knows
It would seem that the T cell response to superantigen would be counterproductive for Streptococcus and the ideas you present for reasons why superantigens exist are interesting. I found a paper that offers another hypothesis: superantigens interfere with the protective adaptive immune response by disrupting specific antibody production as well as antigen specific T cell responses. I guess this means that superantigens kick up T cell responses, but since they are not antigen specific responses the Streptococcus has essentially bought some additional time to do damage undetected.
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Streptococcus pyogenes: Insight into the function of the streptococcal superantigens
Sriskandan S, Faulkner L, Hopkins P
Int J Biochem Cell Biol 39 (2007) 12-19
I think you hit the nail on the head regarding how this bacteria can survive even though it is killing its host. The dead host can still be infectious to other organisms. It probably didn't evolve in humans then since we don't eat our dead. A bacteria that has this unique ability could potentially develope antibiotic resistance making it a super bacteria that makes super antigen right? All the more reson not to abuse antibiotics.
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