Injecting coxsackievirus B infected mice with DAF and CAR receptors stopped the virus

[Hip]

In the studies quoted below, recombinant (= artificially synthesized) DAF and CAR receptors were experimentally injected into mice that had coxsackievirus B infections. DAF and CAR are receptors are normally located on the surface of the cell, and coxsackievirus B latches onto these receptors in order to break into and infect a cell.

It would appear that by injecting these artificial, recombinant DAF and CAR receptors into the mice, the coxsackieviruses attached to the recombinant DAF and CAR receptors instead, rather than the real DAF and CAR receptors on the mice's cells. Doing this blocked the coxsackievirus infection.

This might translate to a chronic fatigue syndrome treatment option in the future, as of course ME/CFS is strongly linked to chronic coxsackievirus B infection. It looks promising.

Inhibition of coxsackie B virus infection by soluble forms of its receptors: binding affinities, altered particle formation, and competition with cellular receptors

J Virol. September 2005.

Goodfellow IG, Evans DJ, Blom AM, Kerrigan D, Miners JS, Morgan BP, Spiller OB.
School of Animal and Microbial Sciences, University of Reading, United Kingdom.

We previously reported that soluble decay-accelerating factor (DAF) and coxsackievirus-adenovirus receptor (CAR) blocked coxsackievirus B3 (CVB3) myocarditis in mice, but only soluble CAR blocked CVB3-mediated pancreatitis.

Here, we report that the in vitro mechanisms of viral inhibition by these soluble receptors also differ. Soluble DAF inhibited virus infection through the formation of reversible complexes with CVB3, while binding of soluble CAR to CVB induced the formation of altered (A) particles with a resultant irreversible loss of infectivity.

A-particle formation was characterized by loss of VP4 from the virions and required incubation of CVB3-CAR complexes at 37 degrees C. Dimeric soluble DAF (DAF-Fc) was found to be 125-fold-more effective at inhibiting CVB3 than monomeric DAF, which corresponded to a 100-fold increase in binding affinity as determined by surface plasmon resonance analysis.

Soluble CAR and soluble dimeric CAR (CAR-Fc) bound to CVB3 with 5,000- and 10,000-fold-higher affinities than the equivalent forms of DAF. While DAF-Fc was 125-fold-more effective at inhibiting virus than monomeric DAF, complement regulation by DAF-Fc was decreased 4 fold.

Therefore, while the virus binding was a cooperative event, complement regulation was hindered by the molecular orientation of DAF-Fc, indicating that the regions responsible for complement regulation and virus binding do not completely overlap. Relative contributions of CVB binding affinity, receptor binding footprint on the virus capsid, and induction of capsid conformation alterations for the ability of cellular DAF and CAR to act as receptors are discussed.

PMID: 16140777

Virus receptor trap neutralizes coxsackievirus in experimental murine viral myocarditis

Cardiovasc Res. August 2006.

Byung-Kwan Lim, Jin-Ho Choi, Jae-Hwan Nam, Chae-Ok Gil, Jae-Ok Shin, Soo-Hyeon Yun, Duk-Kyung Kim and Eun-Seok Jeon.
Department of Medicine, Sungkyunkwan University School of Medicine, Cardiac and Vascular Center, Samsung Medical Center, 50 Il-won Dong, Kangnam-Ku, Seoul 135-710, Korea.

Objective: The coxsackie and adenovirus receptor (CAR) and the decay-accelerating factor (DAF) are receptors for coxsackievirus B3 (CVB3), which is known as the major cause of human viral myocarditis. We investigated the potential for therapeutic use of soluble virus receptor fusion proteins.

Methods We designed and generated a novel virus receptor trap (hCARhDAF:Fc) consisting of both CVB3 receptors and the Fc portion of human IgG1 and evaluated its antiviral effects in experimental CVB3 myocarditis.

Results: Among four soluble virus receptor fusion proteins (hCAR:Fc, hDAF:Fc, hCARhDAF:Fc and hDAFhCAR:Fc), hCAR:Fc and hCARhDAF:Fc in the supernatant of transfected cells neutralized echovirus, adenovirus, and various serotypes of CVB in a dose-dependent manner. Both soluble viral receptor proteins bound to the VP0 and VP1 capsid proteins of CVB3. The in vivo efficacy of viral receptor proteins was evaluated by intramuscular injection of plasmid (hCAR:Fc or hCARhDAF:Fc) followed by electroporation in a murine model of CVB3 myocarditis. Serum levels of the virus receptor proteins increased relative to baseline values from day 3 and peaked on day 14 at 12.9-fold for hCAR:Fc and 7.1-fold for hCARhDAF:Fc. The 3-week survival rate was significantly higher in hCARhDAF:Fc-treated mice (61%) than in hCAR:Fc-treated mice (29%) and in controls (15%; p<0.05). Myocardial inflammation, fibrosis, and myocardial virus titers were all significantly reduced in the hCAR:Fc and hCARhDAF:Fc groups compared to the controls.

Conclusion Our soluble virus receptor trap, hCARhDAF:Fc, attenuated viral infection, myocardial inflammation, and fibrosis, resulting in higher survival rates in mice with coxsackieviral myocarditis. Furthermore, it consists exclusively of human components, and we demonstrated that this soluble virus receptor trap may be used as a potential candidate for a novel therapeutic agent for the treatment of acute viral myocarditis during the viremic phase.

PMID: 16806133

Wikipedia says of this:

Recombinant soluble DAF-Fc has been tested in mice as an anti-enterovirus therapy for heart damage; however, the human enterovirus that was tested binds much more strongly to human DAF than to mouse or rat DAF. Echoviruses and coxsackie B viruses that use human decay-accelerating factor (DAF) as a receptor do not bind the rodent analogues of DAF and DAF-Fc has yet to be tested in humans.

 

[alex3619]

Hi Hip, this approach will work with ANY virus. It has one drawback though. The receptor-virus combination can be seen by the immune system. If an antibody based immune response is launched, there is a risk of an autoimmune attack on those receptors. Now for acute life-threatening viral attack, the risk is probably worth it. For a chronic viral infection the risk is probably not worth it.

There is another approach that is similar but I don't have a reference handy. They could put the receptors in a filter and pass the blood through it, similar to dialysis.

Bye, Alex

 

[Hip]

Hi Hip, this approach will work with ANY virus. It has one drawback though. The receptor-virus combination can be seen by the immune system. If an antibody based immune response is launched, there is a risk of an autoimmune attack on those receptors. Now for acute life-threatening viral attack, the risk is probably worth it. For a chronic viral infection the risk is probably not worth it.

Very interesting point, Alex. Is an autoimmune attack on the receptors a known and observed risk of such a therapy, or this a theoretical concern, as far as you know? I can certainly imagine it could be a problem.

 

[alex3619]

Hi Hip, its a theoretical concern, but well grounded. It is why molecular mimicry is such an issue with pathogens. An antibody binds to a particular shape of molecule (where shape includes things like charges and not just physical shape). If a receptor binds to a virus, then the immune system could flag the virus-receptor complex as a target. The immune system will look for a match. Under those circumstances it might accidentally lock onto the receptor part (and hence induce autoimmunity), or an overlap between receptor and virus (which is less worrying). Bye, Alex

 

[Hip]

If a receptor binds to a virus, then the immune system could flag the virus-receptor complex as a target. The immune system will look for a match.

I wonder if this is the cause of many types of autoimmunity in general. In ME/CFS, 50% of patients have antibodies to the acetylcholine muscarinic receptor (ref: here).

The acetylcholine muscarinic receptor is found on the parasympathetic ("rest and digest") nervous system, and these muscarinic receptor antibodies are likely causing some parasympathetic dysfunction and dysautonomia.

But what I'd like to know is how the immune system comes to make the mistake of creating antibodies against the muscarinic receptor. Might it be a similar thing to what you have described, where a receptor somehow gets attached to a viral particle?

 

[alex3619]

Hi Hip, thats one theory. The other is basically a mistaken identity theory. Something toxic in the blood, or just seems to be toxic, has a simlar amino acid configuration to, for example, the acetylcholine receptor. So the body makes antibodies to the first substance, but then they have an effect on the recptor (though perhaps a weaker effect as its only a similar molecule, not quite the same). This is the thought behing mimicry: some pathogens deliberately make proteins similar to ones in the body. If the body mounts an immune defence, it also attacks itself, weakening itself so the pathogen has a better chance of survival. Bye, Alex