Ebola - Why fatal to humans but not chimps

[Murdstone]

Ebola - chimpanzee - not fatal - bush meat - fatal to humans - why?

 

[aroc91]

Ebola - chimpanzee - not fatal

Sure about that?

http://jid.oxfordjournals.org/content/179/Supplement_1/S120.full

 

[gravenewworld]

Maybe you meant bats?

Like bacteria and most other pathogens, infection begins with sugars and carbohydrate patterns that cover the surface of all cells and pathogens. For example, LPS, which are on the surface of bacteria are highly potent immune antigens and are the root cause of sepsis. In order to infect a cell, viruses must first bind to the surface of a cell. The is almost always heavily mediated in some way by glycosylation structures on cell surface/viral/bacteria surface proteins--that's why they're called glycoproteins.

One of the first lines of defense for pathogen infection that are circulating in your body right now are known as what are called mannose binding lectins (MBLs). Lectins are essentially just proteins that bind to sugars. MBLs will often bind to the surface of many types of pathogens in order to reduce or prevent their ability to infect cells. Glycoproteins on the surfaces of filoviruses such as Ebola (which they use to enter cells) are very heavily glycosylated and contain high mannose type glycan structures, making them very good substrates for binding by MBLs.

The reason bats may be able to harbor ebola without becoming infected is probably due to innate differences in their immunity compared to human. I'd be a lot of money on the idea that somewhere along our evolutionary history, we diverged far away from bats in terms of the types and quantity of MBLs we produce. Bats may be producing much higher serum quantities of MBLs as well as different variants which may help them to be resistant to ebola since it'd prevent viruses from entering the cell.

In fact, you can prevent ebola infected mice from dying if they get dosed with enough MBL :

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3071052/http://jid.oxfordjournals.org/content/203/2/175.full.pdf

 

[zoki85]

Dogs and cats are resistant?

 

[Torbjorn_L]

"While pigs that have been infected with RESTV tend to show symptoms of the disease, it has been shown that dogs may become infected with EBOV and remain asymptomatic. Dogs in some parts of Africa scavenge for their food and it is known that they sometimes eat infected animals and the corpses of humans. Although they remain asymptomatic, a 2005 survey of dogs during an EBOV outbreak found that over 31.8% showed a seroprevalence for EBOV closest to an outbreak versus 9% a farther distance away.[156]" [ http://en.wikipedia.org/wiki/Ebola_virus_disease ]

 

[zoki85]

Yes, looks like most species of mammals are resistant. This has some similarity with a Smallpox .
Similar mortality, period of incubation, and animals were ok with it .
But it was much more contagiuos than ebola (therefore, more dangerous )

 

[FactChecker]

It is fatal to chimps. They tested the spread of ebola through air by placing cages of chimps side-by-side and seeing if infections in one cage spread to the other. It did not. I remember reading that infected chimps died. They are also using chimps to test ebola vaccines.
P.S. ebola outbreaks have killed about one third of the world's gorillas.

 

[Shadowmaru]

It is fatal to chimps. They tested the spread of ebola through air by placing cages of chimps side-by-side and seeing if infections in one cage spread to the other. It did not. I remember reading that infected chimps died. They are also using chimps to test ebola vaccines.
P.S. ebola outbreaks have killed about one third of the world's gorillas.

I read the study on this, and the chimps did not have contact with each other, but caught the virus. It's never been proven, but well documented and accepted the chimps did not have contact with each other, so that would leave only one conclusion.

 

[FactChecker]

I read the study on this, and the chimps did not have contact with each other, but caught the virus. It's never been proven, but well documented and accepted the chimps did not have contact with each other, so that would leave only one conclusion.

That happened at first. Later, they were more careful when cleaning the cages. The ebola did not spread from cage to cage after that. The conclusion was that there was cross contamination when the cages were cleaned.

 

[Shadowmaru]

That happened at first. Later, they were more careful when cleaning the cages. The ebola did not spread from cage to cage after that. The conclusion was that there was cross contamination when the cages were cleaned.

I'm not sure I read that part, RE - Extra cleaning and it never jumped. The monkeys got sick, one after another, some in different rooms. They were all terminated in the end.

 

[Torbjorn_L]

I'm faintly amazed by the seeming success of using surviving humans as serum donors instead of the usual (IIRC) horse or rabbit. The probably can't use asymptomatic dogs though. Bummer.

[The vaccines coming out are likely only taking care of of the most virulent lineage. But at least 2 are circulating in the current outbreak(s), as seen by the different survival frequencies in the different areas. By the way, it would have been nice to vaccinate against all of them at once.]

that would leave only one conclusion.

Are you suggesting an air or water borne virus? It is not. [ http://www.cdc.gov/vhf/ebola/transmission/index.html?s_cid=cs_3923 ]

 

[Ygggdrasil]

I'm faintly amazed by the seeming success of using surviving humans as serum donors instead of the usual (IIRC) horse or rabbit. The probably can't use asymptomatic dogs though. Bummer.

Wouldn't the human immune system recognize horse or rabbit serum as foreign and attack those antibodies?

[The vaccines coming out are likely only taking care of of the most virulent lineage. But at least 2 are circulating in the current outbreak(s), as seen by the different survival frequencies in the different areas. By the way, it would have been nice to vaccinate against all of them at once.]

What evidence is there for two circulating strains? As far as I know, the best evidence suggests the current ebola outbreak originates from one zoonotic event and no other strains have arisen (http://www.sciencemag.org/content/345/6202/1369). The different survival frequencies in different areas could simply be a result of differing qualities of medical care in the different areas.

 

[atyy]

What evidence is there for two circulating strains? As far as I know, the best evidence suggests the current ebola outbreak originates from one zoonotic event and no other strains have arisen (http://www.sciencemag.org/content/345/6202/1369). The different survival frequencies in different areas could simply be a result of differing qualities of medical care in the different areas.

Congo is reported to have a different strain from the West African outbreak. http://news.sciencemag.org/africa/2...la-unrelated-escalating-west-african-epidemic: "A new Ebola outbreak in the Democratic Republic of the Congo (DRC) is unrelated to the 6-month-old epidemic in West Africa, a genetic analysis has confirmed. Although the virus belongs to the same species, Ebola-Zaire, the strain is genetically so different that it "is definitely not a dissemination of the outbreak in West Africa,” says virologist Eric Leroy of the International Centre for Medical Research of Franceville, the World Health Organization (WHO) collaborating center in Gabon that is characterizing the DRC virus."

 

[Ygggdrasil]

Congo is reported to have a different strain from the West African outbreak. http://news.sciencemag.org/africa/2...la-unrelated-escalating-west-african-epidemic: "A new Ebola outbreak in the Democratic Republic of the Congo (DRC) is unrelated to the 6-month-old epidemic in West Africa, a genetic analysis has confirmed. Although the virus belongs to the same species, Ebola-Zaire, the strain is genetically so different that it "is definitely not a dissemination of the outbreak in West Africa,” says virologist Eric Leroy of the International Centre for Medical Research of Franceville, the World Health Organization (WHO) collaborating center in Gabon that is characterizing the DRC virus."

Thanks for the info, I must have missed that. Does anyone know about the broadness of the specificity of the vaccines under development? I was under the impression that the current antibody therapies (e.g. ZMapp) and the vaccines were developed based on virus from previous outbreaks of Ebola-Zaire. Are these treatments thought to be effective against all known forms of Ebola-Zaire or do the strains differ enough that different treatments are required for different strains (or does the virus mutate enough that it will quickly evade any drug or vaccine we develop)?

 

[atyy]

Thanks for the info, I must have missed that. Does anyone know about the broadness of the specificity of the vaccines under development? I was under the impression that the current antibody therapies (e.g. ZMapp) and the vaccines were developed based on virus from previous outbreaks of Ebola-Zaire. Are these treatments thought to be effective against all known forms of Ebola-Zaire or do the strains differ enough that different treatments are required for different strains (or does the virus mutate enough that it will quickly evade any drug or vaccine we develop)?

I'm pretty much just reading the news reports, but my guess is that there are concerns about strain. A recent very promising test of ZMapp in animals used a different strain from the one in the current West African outbreak. However, they also did additional ex vivo tests against the current strain. That they did these additional tests would seem to me that they don't automatically know how effective ZMapp is against a different strain.
http://www.nature.com/news/ebola-drug-saves-infected-monkeys-1.15793: "The strain of Ebola virus used in the study is not the same as the one causing the current outbreak. But researchers showed that the antibodies in ZMapp recognize the current form of the virus in cell cultures, and the parts of the virus recognized by the drug are present in the strain of Ebola that has caused the outbreak."
http://www.nature.com/nature/journal/v514/n7520/full/nature13777.html: "Advanced disease, as indicated by elevated liver enzymes, mucosal haemorrhages and generalized petechia could be reversed, leading to full recovery. ELISA and neutralizing antibody assays indicate that ZMapp is cross-reactive with the Guinean variant of Ebola."

 

[Shadowmaru]

I'm faintly amazed by the seeming success of using surviving humans as serum donors instead of the usual (IIRC) horse or rabbit. The probably can't use asymptomatic dogs though. Bummer.

[The vaccines coming out are likely only taking care of of the most virulent lineage. But at least 2 are circulating in the current outbreak(s), as seen by the different survival frequencies in the different areas. By the way, it would have been nice to vaccinate against all of them at once.]
Are you suggesting an air or water borne virus? It is not. [ http://www.cdc.gov/vhf/ebola/transmission/index.html?s_cid=cs_3923 ]

This depends what you class as Air Borne ?

Sneezing into someone else's face ? The Virus can also survive on surfaces outside of the host.

 

[Torbjorn_L]

Wouldn't the human immune system recognize horse or rabbit serum as foreign and attack those antibodies?

I was thinking of making polyclonal antibodies, I believe. I don't know if you can use the serum directly.

[ http://en.wikipedia.org/wiki/Polyclonal_antibodies ]

What evidence is there for two circulating strains? As far as I know, the best evidence suggests the current ebola outbreak originates from one zoonotic event and no other strains have arisen (http://www.sciencemag.org/content/345/6202/1369). The different survival frequencies in different areas could simply be a result of differing qualities of medical care in the different areas.

"In August 2014, the WHO reported an outbreak of Ebola virus in the Boende District, Democratic Republic of the Congo.[139] They confirmed that the current strain of the virus is the Zaire Ebola species, which is common in the country (the name "Zaire" is the former name of DR Congo). The virology results and epidemiological findings indicate no connection to the current epidemic in West Africa. "

[ http://en.wikipedia.org/wiki/Ebola_virus_epidemic_in_West_Africa ]

 

[Torbjorn_L]

This depends what you class as Air Borne ?

Sneezing into someone else's face ? The Virus can also survive on surfaces outside of the host.

The survival outside the body is on the order of hiv and flu I believe, some 15 minutes. The original comment was asking for your clarification, if you think the virus will spread from room to room by air convection only. Currently it will need a carrier for spreading.

 

[Ygggdrasil]

I was thinking of making polyclonal antibodies, I believe. I don't know if you can use the serum directly.

Still, the human immune system will recognize non-human antibodies as foreign, and cause an immune reaction to those antibodies. For example, doctors used to use monoclonal antibodies from mice to treat various conditions until the recognized that the foreign antibodies were causing an immune reaction that would lower the effectiveness of the treatment and cause potentially serious side effects (http://en.wikipedia.org/wiki/Human_anti-mouse_antibody). Treating Ebola patients with non-human antibodies might work if they require only one dose, but after that one dose, the immune system will have been primed to react to subsequent doses of antibody.

 

[Torbjorn_L]

Good thing I'm no doctor...