Development of An Effective Viral Vaccine Platform: "The Ebola Story,"

January 22, 2021

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John K. Rose, PhD, professor emeritus of pathology and senior research scientist, provided details of development of the Merck Ebola vaccine, which was FDA licensed in 2019, and work on VSV (vesicular stomatitis viruses) in general.

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00:00Thank you very much for the opportunity
00:02to tell you about the history of the VSV
00:05vaccine platform and how it was used to
00:08make the approved Ebola vaccine as required.
00:11I disclosed that I am on the Scientific
00:13Advisory Board for Carriage incorporation.
00:15My talk today is unrelated to
00:18any work at or funded by Karajan.
00:21Alright, development of an effective
00:23viral vaccine platform. The Ebola story.
00:26So the Merck Ebola vaccine.
00:28Merck Ebola vaccine is called Erve Bo.
00:31It's a recombinant VSV expressing
00:33the Zaire Ebola virus glycoprotein.
00:35This was fully licensed by the
00:38FDA in December 2019.
00:40It's the only vaccine based on an engineered
00:44recombinant virus that's licensed in the US.
00:47Vaccine is built on the sicular stomatitis
00:50virus or VSV vaccine platform that we
00:53developed in our laboratory at Yale.
00:55And how did this happen?
00:57It's an extremely long story.
00:58I can't really do it in 15 minutes,
01:01so I refer you to this article
01:03written by Helen brands.
01:04Well, at stat it's called against all odds.
01:07The inside story of how scientists across
01:09three continents produced any Bola vaccine.
01:11She spent at least six months on it.
01:13If you really want a good read,
01:15take a look at this.
01:17It's if you Google Hellenbrand well, Ebola
01:19vaccine will probably be your first hit.
01:22Alright, what is VSV?
01:24It's a non lethal pathogen of cattle.
01:27It causes vesicular lesions of the mouth,
01:28the tongue that eats,
01:29and the hubs and animals can't eat for
01:31a couple of weeks, but they recover.
01:33VSV grows rapidly to very high
01:35titers in tissue culture,
01:37but it's not a human pathogen.
01:40Yes,
01:40we also generates potent innate
01:42antibody and T cell based community.
01:46So it's been a favorite of molecular
01:48biologists like me and also immunologists.
01:55PSV is the prototype for the large group of
01:58Nonsegmented negative strand RNA viruses.
02:00There are numerous serious
02:01pathogens in this group.
02:03I just mentioned a couple of them here.
02:06Rabies is 90. Excuse me?
02:08Nearly 100% fatal measles, you know about.
02:11Ebola and Marburg are the feel of
02:14viruses and Ebola can be up to 90% fatal.
02:17They cause hemorrhagic fevers.
02:19Alright, VSV, it's a bullet shaped virus.
02:22This one favorite pictures taken
02:25by former postdoc Michael Witt.
02:27And bullet shaped particles contain the
02:29helical nucleocapsid drawn in cartoon form.
02:32Here the RNA is a negative strand shown in
02:35yellow bound to the nucleocapsid protein
02:37and because this is the negative strand,
02:40it doesn't encode protein directly.
02:43Virus has to carry a PLB race and
02:46RNA dependent RNA polymerase that
02:48was discovered by David Baltimore.
02:50He was my former mentor and I learned
02:53about VSV in his lab in between the
02:56nucleocapsid and the membrane there is a
02:58matrix protein and then the glycoprotein
03:01spikes stick through that membrane.
03:06All right, generating
03:07recombinant virus vaccines.
03:08Why would we ever think about
03:10doing something like that?
03:12The reason is that vaccines that are
03:14based on live attenuated viruses
03:16often induced lifelong immunity
03:18to infection after a single dose.
03:20Examples are the measles vaccine,
03:22which is about 98% effective
03:24vaccinia virus relative of smallpox,
03:26which used to eliminate that
03:28horrible disease from the Earth.
03:30And live poliovirus vaccines
03:32are also extremely effective.
03:33So in the early 1980s,
03:35researchers began to use recombinant
03:37DNA technology to generate live
03:39virus vaccines built on attenuated
03:41viruses expressing foreign antigens.
03:42The first person I heard of doing
03:45this was Bernie Moss at the NIH,
03:47and he is still working on this.
03:51So at that time we thought VSV could be
03:53an ideal recombinant vaccine system,
03:55but we had no method for recovering
03:57VSV either from DNA or RNA copies,
04:00and this is because there is no
04:02infectious RNA or DNA copy for
04:04VSP or any of the NS viruses.
04:06So this was very frustrating.
04:08But finally in 1994,
04:10after over six years of failures,
04:12we were able to recover live VSV using
04:15a multi DNA transfection protocol
04:17that assembled a VSV anti genome
04:20and protein complex inside the cell
04:22bound to the VSV polymerase subunits
04:25and that got the system going.
04:29It's rather complicated if you
04:31want the details.
04:32We published this the first recovery of
04:35ESV from DNA in 1990 five 26 years ago.
04:38I can't believe it,
04:39but this opened up VSP for genetic
04:41analysis and we also noted at
04:43this time it might be possible to
04:46genetically engineer recombinant VSV
04:48is displaying foreign antigens and
04:50we might be able to use these two as
04:53vaccines protecting against other viruses.
04:56Alright,
04:56so there were major questions to be answered.
04:58We had wonderful people joining the lab.
05:00Once we had this system and.
05:03Could we express foreign genes
05:04in the VSV recombinants with the
05:06genes be stable in their comments?
05:08Could such recumbents be useful
05:10as vaccines and many viruses?
05:12Many RNA viruses? Recumbents are not stable.
05:15Alright, so we got to work on this.
05:18And found he used the conserved
05:20stop start signals that are present
05:22in the VSV genomes.
05:23Put them around a new gene stuck a new
05:26gene in all convenient restriction
05:27sites engineered into this.
05:29We could make a recombinant virus and
05:31it grew just a wild type titers and
05:34most importantly it was completely
05:35stable for at least 15 passages
05:37involving millionfold expansion at
05:39each passage. So this set to us, you know.
05:42Maybe maybe this could be a vaccine,
05:45and our first model system wasn't
05:47influenza model in mice and this
05:49was anjanette Robertson.
05:50Evelyn Kretchmar,
05:50who started this work in my lab.
05:53So we made a VSV via CS5 genes,
05:56NPM giannell and we stuck in an
05:59HAG and that's the HA is the major
06:02protective antigen for flu.
06:03We made another one that's an
06:05attenuated VSV we truncate the tail
06:07of the SVG and that makes it non
06:09pathogenic. In animals.
06:10We also made a version where we take
06:13out the G and put in the HA and this
06:16is the only data that I will show.
06:18We put these into animals.
06:19This is a vaccine study is
06:21our average mouse weights.
06:22This is the time of vaccination and
06:25then the time of challenge with a
06:27lethal dose of flu is here at 35 days.
06:30And what you can see in the controls
06:33in the blue triangles is to animals
06:35that haven't been vaccinated,
06:37die within seven days.
06:39All of the vaccine animals survive just fine,
06:43not even weight loss.
06:44After the challenge,
06:45the one virus that's a little
06:47hot is the wild type virus,
06:50which causes mice to lose weight.
06:52Importantly,
06:53the influenza neutralizing antibody
06:55titers that we saw generated by
06:58these vectors were greater than
06:59one to 4001 to 20 is what you
07:02need to protect mouse from flu.
07:04Also similar number in humans,
07:06so this is 200 times what
07:08you need to protect.
07:10It was also sterilizing immunity.
07:12We couldn't detect any flu replication
07:15in these protected animals.
07:16Alright, so these are the first experiments
07:18that established VSDS as vaccine vectors.
07:20We engineered them with convenient
07:22restriction sites all over the place,
07:24so you could put in jeans
07:26in different positions.
07:26If the foreign gene encoded a membrane,
07:29protein it off and ended up in the
07:31surface of the virus particle,
07:33which is a good place to
07:35be to generate immunity.
07:36So they grew to high titers.
07:39Stable gene expression.
07:40We could accommodate over 4 kilobases
07:42of foreign genes in multiple positions.
07:45Strong antibody CT cell responses.
07:47An importantly there was
07:48no pre existing immunity.
07:50No significant community
07:51to the vector in humans.
07:53Alright.
07:54Another important point was that
07:56we found this is a paper in 1999.
07:59You're going to actually replace
08:01the VSV G with a very distantly.
08:05Very foreign glycoprotein from a
08:07retrovirus from HIV and now you have.
08:10You can make a VSV which has the
08:13HIV coat and shows the specificity
08:16of infection that HIV has.
08:19Alright.
08:20So the first brick that we put
08:22on the foundation was that
08:25for influenza virus later on,
08:27Gen.
08:28Schwartz and others in my lab
08:30went on to study avian flu,
08:32which we thought might be the next pandemic,
08:35and it still could be.
08:37We studied respiratory syncytial virus.
08:39Our major focus was HIV aids using
08:42Sivs and Shift models in monkeys and
08:45this led to clinical trials which
08:47I don't have time to go into now.
08:50We also worked on SARS.
08:54But by the time we had these vectors,
08:56SARS was illuminated through
08:57public health measures.
08:58Papilloma virus plague chicken,
08:59gunia, Zika, nipah.
09:00These are all all these things in
09:03green are examples of ones that we
09:05where we made the factors in our lab,
09:07and.
09:08They were often tested in other labs
09:10where they could work with the pathogens,
09:13but what about what about Ebola?
09:14These examples in white are
09:16examples of studies where we
09:18simply sent the vectors to other people.
09:20We couldn't work on Ebola and Marburg at
09:23Yale we didn't have facilities for that.
09:26So we sent these out to hundreds of labs,
09:28including labs in Europe.
09:30And we sent to a lab actually
09:32at the University of Marburg,
09:35Hans Dieter, Clanks lab.
09:36We sent the vectors there,
09:38Anna guy there Heinz,
09:40Feldmann was making these recombinants,
09:42and then Hines moved to
09:44Canada to their BL4 lab,
09:46where he could do studies using
09:49the Ebola and Marburg vectors
09:51built on RV SV platform.
09:53And his paper the 1st paper.
09:55They did small animal studies first.
09:57The 1st paper in Monkeys is shown here.
09:59Nature Meadow.
10:00In 2005,
10:01so they made these recombinant VSV's
10:03expressing the Ebola glycoprotein
10:05or the Marburg single IM injection
10:08completely protective immune
10:09response and most importantly
10:11they had no evidence of Ebola or
10:14Marburg replication in any of the
10:16protected animals after challenge,
10:19so sterilizing immunity apparently.
10:21Alright,
10:21so how did the VSV Ebola
10:24vaccine get to Africa?
10:26Well,
10:26I wasn't really involved in any of this.
10:29I've read about it in in the public
10:31press and I've read it Mountain
10:33Helens article and I'm going to
10:35summarize this just very briefly,
10:37so the Canadian Government
10:39patented the VSV Ebola vaccine,
10:40but they found no market for it.
10:43Canada then sold the vaccine
10:44rights to a small company in Iowa,
10:47and they apparently didn't
10:48do anything with it.
10:49Then in 2014 there was this major
10:52outbreak of Ebola in West Africa.
10:54Thousands of people were dying.
10:56Cases were being imported into
10:57the US and to other countries.
11:00It was a real panic situation and
11:02because the VSV Ebola vaccine had
11:04been tested extensively in monkeys
11:06and also in one exposed lab worker,
11:08it was a reasonable candidate.
11:10This is actually important right
11:12here that they used it in somebody
11:14who had been exposed because they
11:16knew that the ESV Ebola vaccine
11:18worked in monkeys even after the
11:20monkeys were exposed to Ebola.
11:22At least up to 24 hours.
11:24They could protect with this vaccine,
11:26so it's a very.
11:28Fast response that protects.
11:29So Merck bought the vaccine,
11:31started producing it,
11:32and organized clinical trials,
11:33and there are many people involved
11:35in clinical trials.
11:36I don't know any of them.
11:38Merck ship the vaccine to West Africa,
11:41where it was used for clinical
11:43trials in the field.
11:45And here's the paper on this.
11:47This was published in Lancet in 2015.
11:49Single dose VSV Ebola vaccine
11:51was 100% effective and this
11:53was a ring vaccination study.
11:55It's an interesting way
11:56of doing it in the field,
11:58but in the case where they
12:00got the vaccine in early,
12:02they protected everybody around in the ring.
12:04In the case where they got the
12:07vaccine and later they had,
12:09I think 16 infections.
12:11So anyway, look,
12:12looked really good and it
12:15continues to be used so.
12:17Just to summarize,
12:18the Merck VSV Ebola vaccine,
12:20fully licensed by the European
12:22Commission and by the FDA
12:24and late 2019. It's also been
12:27licensed in eight African countries.
12:30Over 350,000 people have been
12:31vaccinated with the VSV Ebola vaccine,
12:33and there are stockpiles that I
12:36think are even much larger than that.
12:39Antibodies are the major correlate
12:41of protection and they persist for
12:44at least two years after vaccination,
12:46and it's really exciting to see our
12:49basic vaccine vector work go this far.
12:52Alright, normally at this point I would
12:54have a slide thanking all of the people
12:57who got involved in this work in my lab.
12:59All of our collaborators,
13:00but it would just be too many and I would
13:02leave out somebody really important.
13:04Then there are also all the people who
13:06took the vaccine and out into the field.
13:09In Africa,
13:10working under dangerous conditions,
13:11especially most recently in the
13:14Democratic Republic of the Congo and
13:17now we've got covid. On top of that.
13:20Alright, so?
13:22We don't have any format for questions here,
13:25but there's obviously there must be
13:27a question in some people's minds.
13:29What about a VSV SARS Co V2 vaccine?
13:33Alright,
13:33well I was already semi retired
13:35and beginning to close down my
13:38lab as the pandemic emerged,
13:40but with support and encouragement from
13:42Chen Liu, our new chair of Pathology.
13:46Timber yard bensky began this collaboration
13:50with Craig Wyland's lab to make VSV SARS,
13:52two Spike Suda types and also recombinants.
13:55And we've made the pseudotyped.
13:56The Recumbents have been more problematic
13:59'cause they don't grow very well.
14:01In the meantime,
14:02it became clear very quickly
14:04through the Grapevine and preprint
14:06servers that major laboratories in
14:08companies had already made VSV SARS.
14:10Two spiker comments they had initiated
14:12animal studies, and these were.
14:14These were looking very good.
14:17So Merck has initiated Phase
14:19one clinical trials with the VSV
14:22stars to spike recombinant.
14:24They haven't really published on this,
14:26but often big companies don't publish
14:28the Israel Institute for Biological
14:29Research is also doing clinical
14:31trials with a similar recombinant.
14:33And they have published on that
14:35in a hamster model,
14:37where it appears to give
14:39sterilizing protection.
14:40So I hope the vaccines that are already
14:43in use or in phase three trials will
14:47be sufficient to control this pandemic.
14:50You know we've got.
14:52We've got the M RNA vaccines
14:53that look really good there.
14:55It seems to be in short supply.
14:58The various adenovirus vectors
14:59are extremely good.
15:00Their protein vaccines in the pipeline
15:03and they are likely to work also,
15:05but if these are not sufficient,
15:07I think of ESV based SARS.
15:09Two vaccine is likely to be an
15:12effective single dose vaccine.
15:14Then I will stop there and say thank you.