Viruses and Bacteria that Affect the Immune System

[TylerH]

What are some viruses and bacteria that affect the immune system? I'm writing a synthesis essay for my AP biology class about a virus or bacterium that affects the immune system (we're covering the immune system). Most of the obvious are already taken, eg. HIV, influenza, etc. I'm looking for anything that negatively affects the immune system. I would especially appreciate any esoteric viruses or bacteria, if anyone happens to be aware of any that fit the criteria.

Thanks,
Tyler

 

[bobze]

Something cool you could check into are bacteria that are obligate intracellular pathogens--Particularly those that replicate in immune cells. Like Rickettsia (the causative agent of rocky mountain spotted fever). There are other newer "emerging" bacterial disease that fit this bill as well such as Ehrlichia and Anaplama.

Most pathogenic bacteria and all viruses really interact with the immune system, as that is part of their "properties" (or virulence) that allows them to be pathogenic.

Some other good viral examples would be Epstein-Barr or Human T-cell lymphotropic virus.

 

[TylerH]

Thank you so much! I wrote my paper on Human T-cell Lymphotropic Virus Type 1. If I do say so myself, I had the most interesting virus of anyone in the class, and the credit goes to you for that.

If you'd like to read it: https://docs.google.com/leaf?id=0B6...NzE4OC00NGI3LTgwYWYtMWM5NzBmYjUyNTJi&hl=en_US. It's only a page.

 

[TylerH]

That's pretty cool. Being a comp. sci. nerd, I'm about as interested in biological-computer combinations as one could be (since I have motivations on both the computer and biological sides). I'm waiting on the ability for computers to communicate with us directly through our existing neural networks. I don't think it would be hard for us to adapt to a user interface build directly into our existing vision and allowing input via imagined motions. I guess the hardest part would be the neuroscience involved in communicating with our neural networks; programming the computers wouldn't be that hard, once the protocol is known.

 

[Ygggdrasil]

Just last week, the journal Science published two papers showing that some viruses rely the bacteria in our gut in order to infect their hosts. One paper looked at mouse mammary tumor virus (MMTV), a relative of HTLV. MMTV is passed from a mother mouse to its child via its milk. These researchers found that if they treated infected pregnant mice with antibiotics to wipe out their gut bacteria, the mice did not transmit the virus to their progeny. Antibiotics, while effective at killing bacteria, do not stop viral infections, so something strange was going on. After looking deeper into the problem, the researchers found that MMTV picks up molecules from the gut bacteria's cell walls, called lipopolysaccharides (LPS). When MMTV, now coated with LPS, infects a new host, it uses the LPS coating to trick the host's immune system; the LPS coating activates white blood cells and make them think that the body is being invaded by bacteria. The white blood cells release a signal that ramps the immune system up to fight bacteria, but unfortunately lowers the body's defenses against viruses. Therefore, by hiding behind the bacterial LPS molecules, MMTV has evolved a clever strategy to slip by the immune system's defenses.

While the research may not seem that relevant to humans -- after all, MMTV infects only mice -- another team of researchers showed that the same phenomenon occurs with two viruses that infect humans: poliovirus and reovirus. Although the paper suggests a different means by which LPS molecules aid viral infectivity, the basic result is the same: the viruses pick up LPS molecules from gut bacteria and these LPS molecules enhance the infectivity of the virus.

These two results are especially interesting because they challenge our understanding of the role of our intestinal microflora in immunity. Many previous studies had pointed to an entirely positive role for our natural gut bacteria in immunity: these bacteria crowd out potential pathogens and even play a role in guiding the proper maturation of the immune system. Indeed, previous research had even showed that mice lacking the proper natural gut bacteria are more susceptible to infection by certain viruses.

These two studies, therefore, add a new wrinkle to our view of how the immune system interacts with our intestinal microflora. But perhaps the result is not so surprising. As the communication between our microflora and our immune system have evolved an intimate relationship with each other, the interplay provides viruses and other pathogens with the opportunity to cross some signals and exploit these interactions for their own nefarious purposes.

Here's a link to the two studies I mentioned:
Kane et al. (2011) Successful Transmission of a Retrovirus Depends on the Commensal Microbiota. Science 334:245. http://dx.doi.org/10.1126/science.1210718

Kuss et al. (2011) Intestinal Microbiota Promote Enteric Virus Replication and Systemic Pathogenesis. Science 334: 249. http://dx.doi.org/10.1126/science.1211057