Viruses survive in CSF for a long time?

[asparagillus]

Hi all!

 

Studying for an exam here

 

I've heard that viruses can "hide" in cerebrospinal fluid from the immune system for a long time. Is this so? How come?

 

Can the cells of the immune system reach the CNS?

 

If the cells of the immune system cannot reach the CNS, how can the immune system defend, say, a brain abscess?

 

If anyone could point me to a website or give me other clues on where to find information regarding this, I would be much obliged.

 

TIA

[Monomer]

 

Studying for an exam here

 

Am I too late?

 

 

I've heard that viruses can "hide" in cerebrospinal fluid from the immune system for a long time. Is this so? How come?

 

It seems that HIV and HSV can "hide" in the CSF.

 

Check out this paper:

Transitory infection (Figure 7A) refers to infection sustained by short-lived CD4+ T cells trafficking into the CSF space from the blood. In simplified terms, activation of lymphocytes outside of the nervous system favors their promiscuous entry [43,27], and when infected by HIV, these activated CD4 cells can release HIV into the surrounding fluid. This type of infection is determined principally from outside of the CNS, and depends upon systemic infection and cell activation. Infected and uninfected cells are pushed into the CSF.

 

Autonomous infection (Figure 7B) refers to infection that is sustained within the CNS by longer-lived cells and does not require continuous repletion from the blood. This is the type of infection that is also assumed to be 'compartmentalized' [44] and is likely sustained by longer-lived cells of the monocyte lineage that assume residence as perivascular and meningeal macrophages [45] rather than trafficking lymphocytes [46]. Whether such infection is fully self-sustaining or requires renewal from outside remains uncertain [47], but in it, the rates of turnover are lower and the cellular pools are different from those of transitory infection. When accompanied by CSF pleocytosis, the reactive cells are pulled into the CSF space [48]. Both of these basic types of infection may occur simultaneously or sequentially, and indeed mixed infection with varying contributions of the two types may be the rule (Figure 7C).

 

It is believed that HIV can cross the blood-brain barrier inside circulating monocytes in the bloodstream ("Trojan horse theory"). Once inside, these monocytes become activated and are transformed into macrophages. Activated monocytes release virions into the brain tissue proximate to brain microvessels. These viral particles likely attract the attention of sentinel brain microglia and initiate an inflammatory cascade that may cause tissue damage to the BBB.

http:// http://en.wikipedia.org/wiki/Blood-brain_barrier

 

How HSV gains access to the brain is not known, but here are various hypotheses, Firstly, viruses may enter the brain from the blood stream. To do this the virus must be small, present in large numbers and able to cross the blood/brain barrier (BBB). Taking into account the properties of the virus this is a possible but probably infrequent route of entry to the central nervous system (CNS). Secondly, there is a direct route, via nerves, from the nose to the olfactory lobes of the brain. This route of infection certainly occurs in various animal “models” of HSE but the relevance to the human disease is uncertain. The virus may "move "from its site of latency via nerves to the base of the skull, cross the meninges and infect the brain. There is however little evidence to support this suggestion. A further possibility is that the virus moves from its site of latency in the trigeminal ganglia ”backwards” to the spinal cord and then upwards into the brain. The appropriate nerve pathways exists to support this suggestion but to date there is no definite evidence to support this or indeed any of the other suggested routes.

http:// http://www.encephalitis.info/TheIllness/TypesEncephalitis/HSE.html

 

 

Can the cells of the immune system reach the CNS?

 

Yes, but it seems to be only in the case of inflammation. Here's some info I found:

Pathogenic T cells can enter the CNS because of several reasons such as during viral infection of CNS, as a result of mechanical damage to CNS or inflammatory diseases of CNS or autoimmune reactions, for example in case of MS (an inflammatory disease of CNS believed to be caused by autoimmune T cells). Inflammation is now implicated to be involved also in other neurodegenerative diseases such as Alzheimer's and Parkinson's.

http://www.medicalnewstoday.com/articles/42306.php

 

Have a read of this:

http:// http://books.google.com/books?id=NWBtIpoJ5m4C&pg=PA114&vq=inflammation&dq=t+cells+enter+cns&source=gbs_search_s&sig=ACfU3U2dTKfdJzugNR2f9kvPUMJNZUCjQA#PPA114,M1

 

Maybe you'll find this interesting aswell:

http://www.geocities.com/HotSprings/3468/immucells1.html

[iNow]

What a complete answer. Nicely done.

[Dnasis]

There is also a virus which is known as tick borne encephalitis it is in the flaviviridae genus. which causes inflamation of the meningies (I can't remember how to spell I apologize) and thus is present within the CNS fluid. Encephalitis is also caused by HSV 2 whereby it is known to travel through the nerve ganglions however the process is not fully understood.