New vaccine shown promise in preventing secondary strokes after an ischemic stroke

New research published in journal Hypertension shows that vaccine called S100A9 may be able to replace oral blood thinners to reduce the risk of secondary strokes in patients with recent ischemic stroke.

Japanese researchers successfully tested an experimental vaccine in mice and found that it provided protection against blood clots for more than two months without increasing the risk of bleeding or causing an autoimmune response.

The vaccine, S100A9, inhibits blood clot formation and, during the study, protected the arteries of treated mice from forming new clots for more than two months, and additionally, worked as well as the oral blood thinner clopidogrel in a major artery, according to Hironori Nakagami, M.D., Ph.D., study co-author and professor at Osaka University, in Japan.

“Many stroke patients don’t take their blood thinning drugs as prescribed, which makes it more likely they will have another stroke. This vaccine might one day help solve this issue since it would only need to be injected periodically,” Nakagami said.

Citation: Tomohiro Kawano, M.D.; Munehisa Shimamura, M.D., Ph.D.; Tatsuya Iso, M.D., Ph.D.; Hiroshi Koriyama, M.D., Ph.D.; Shuko Takeda; Tsutomu Sasaki, M.D., Ph.D.; Manabu Sakaguchi, M.D., Ph.D.; Ryuichi Morishita, M.D., Ph.D.; and Hideki Mochizuki, M.D., Ph.D.

Researchers create heat stable vaccines using silica

Researchers at the University of Bath, working with colleagues at the University of Newcastle, have created a technique which can keep vaccines intact at high temperatures by encasing them in silica cages. When a protein in solution is mixed with silica, silicon dioxide binds closely around the protein to match its shape and encases the protein. A major advantage of this method is that it doesn’t require freeze-drying, something that around half of all vaccines won’t survive intact. A powder of ensilicated proteins and the silica cage enveloping the protein means it can be heated to 100°C or stored at 22°C for at least six months with no loss of function.

Once the protein has been encased in silica it can be stored or transported without refrigeration before the silica coat can be removed chemically, leaving the proteins unaffected.

The discovery means that vaccines and other important medicines could be transported much more easily, cheaply and safely, especially to remote areas or places lacking infrastructure where the need is often greatest.

The teams call their method ensilication and hope it will solve the costly and often impractical need for a cold chain to protect protein-based products including vaccines, antibodies and enzymes. The research is published in the journal Scientific Reports. The research team tested the method on three proteins; one from a tetanus vaccine, horse haemoglobin and an enzyme from egg white.

Citation: Chen, Yun-Chu, Tristan Smith, Robert H. Hicks, Aswin Doekhie, Francoise Koumanov, Stephen A. Wells, Karen J. Edler, Jean Van Den Elsen, Geoffrey D. Holman, Kevin J. Marchbank, and Asel Sartbaeva. “Thermal stability, storage and release of proteins with tailored fit in silica.” Scientific Reports 7 (2017): 46568.
Research funding: Royal Society, The Annett Trust
Adapted from press release by the University of Bath.

Current vaccination trials using Zika Purified Inactivated Virus (ZPIV) vaccine

The first of five early stage clinical trials to test the safety and ability of an investigational Zika vaccine candidate called the Zika Purified Inactivated Virus (ZPIV) vaccine to generate an immune system response has begun at the Walter Reed Army Institute of Research (WRAIR) Clinical Trial Center in Silver Spring, Maryland.

The experimental Zika Purified Inactivated Virus (ZPIV) vaccine is based on the same technology WRAIR used in 2009 to successfully develop a vaccine for another flavivirus called Japanese encephalitis. The Zika Purified Inactivated Virus (ZPIV) vaccine contains whole Zika virus particles that have been inactivated, meaning that the virus cannot replicate and cause disease in humans. However, the protein shell of the inactivated virus remains intact so it can be recognized by the immune system and evoke an immune response. The National Institute of Allergy and Infectious Diseases (NIAID) partially supported the preclinical development of the Zika Purified Inactivated Virus (ZPIV) vaccine candidate, including safety testing and non-human primate studies that found that the vaccine induced antibodies that neutralized the virus and protected the animals from disease when they were challenged with Zika virus. WRAIR, NIAID and the Biomedical Advanced Research and Development Authority (BARDA) part of the HHS Office of the Assistant Secretary for Preparedness and Response (ASPR) have established a joint Research Collaboration Agreement to support the development of this vaccine.

Led by WRAIR principal investigator Maj. Leyi Lin, M.D., the new study aims to enroll 75 people ages 18 to 49 years with no prior flavivirus infection. Flaviviruses include Zika virus, yellow fever virus, dengue virus, Japanese encephalitis virus and West Nile virus. Participants will be randomly divided into three groups: the first group (25 participants) will receive two intramuscular injections of the Zika Purified Inactivated Virus (ZPIV)  test vaccine or a placebo (saline) 28 days apart; the other two groups (25 participants each) will receive a two-dose regimen of a Japanese encephalitis virus vaccine or one dose of a yellow fever vaccine before beginning the two-dose Zika Purified Inactivated Virus (ZPIV) vaccine regimen. Investigators chose to administer additional flavivirus vaccines because U.S. service members are often vaccinated against these diseases before deploying to Zika-endemic areas.

Additionally, a subgroup of 30 of the participants who receive the two-dose Zika Purified Inactivated Virus (ZPIV) regimen will receive a third dose one year later. All participants in the trial will receive the same Zika Purified Inactivated Virus (ZPIV) vaccine dose at each injection (5 micrograms). A DoD Research Monitor, an independent physician not associated with the protocol, will monitor the conduct of the trial and report any safety issues to the WRAIR Institutional Review Board. Another independent group, the Safety Monitoring Committee, will also monitor participant safety, review data and report any issues to NIAID. As the regulatory sponsor, NIAID ensures the trial follows the study protocol and informs the FDA of any significant adverse events or risks. NIAID also maintains the Investigational New Drug (IND) application (link is external) for the candidate vaccine. The WRAIR study is expected to be completed by fall 2018.

Four additional Phase 1 studies to evaluate the Zika Purified Inactivated Virus (ZPIV) investigational vaccine are expected to launch in the coming months. These include

A trial enrolling 90 adults ages 18-49 years at the Center for Vaccine Development at the Saint Louis University School of Medicine. This site is an NIAID-funded Vaccine and Treatment Evaluation Unit, and Sarah George, M.D., will serve as principal investigator. All participants will receive either two injections of Zika Purified Inactivated Virus (ZPIV) or a placebo 28 days apart. Participants will be randomly assigned to receive either a high, moderate or low dose at both injections to evaluate the optimal dose for use in larger future studies.

A trial enrolling 90 adults ages 21-49 years at the clinical research center CAIMED, part of Ponce Health Sciences University in Puerto Rico. The site is supported by NIAID via a subcontract from the Saint Louis University School of Medicine. This trial will examine the vaccine’s safety and immunogenicity in participants who have already been naturally exposed to dengue virus. Participants will be randomly assigned to receive either a high dose, moderate dose or a placebo. Elizabeth A. Barranco, M.D., will lead the trial.

NIAID’s Vaccine Research Center (VRC) will test the Zika Purified Inactivated Virus (ZPIV) vaccine candidate as a boost vaccination to its DNA Zika vaccine candidate, which entered Phase 1 clinical trials in August. The next part of the study, which will enroll 60 additional participants ages 18-50 years, will take place at the NIH Clinical Center in Bethesda, Maryland, the Center for Vaccine Development at the University of Maryland School of Medicine’s Institute for Global Health in Baltimore, and Emory University in Atlanta. Half of the participants will receive the NIAID Zika virus investigational DNA vaccine followed by a Zika Purified Inactivated Virus (ZPIV) vaccine boost four or 12 weeks later. The remaining participants will receive only two doses of Zika Purified Inactivated Virus (ZPIV) vaccine four or 12 weeks apart. Julie Ledgerwood, D.O., chief of the VRC’s clinical trials program, will serve as principal investigator.

A WRAIR-funded trial enrolling 48 adults ages 18-50 years will be conducted at the Center for Virology and Vaccine Research, part of Beth Israel Deaconess Medical Center and Harvard Medical School in Boston. One group of participants will receive a single dose of the Zika Purified Inactivated Virus (ZPIV)  vaccine and all other participants will receive two doses of the Zika Purified Inactivated Virus (ZPIV) vaccine at varying intervals. Kathryn Stephenson, M.D., M.P.H., of Beth Israel Deaconess Medical Center, will lead the trial.

Scientists with Walter Reed Army Institute of Research, part of the U.S. Department of Defense (DoD), developed the vaccine. The National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH), is co-funding the Phase 1 clinical trial with Walter Reed Army Institute of Research, serving as the regulatory sponsor and providing other support. BARDA is funding the advanced development of the Zika Purified Inactivated Virus (ZPIV) vaccine candidate through a six-year contract with Sanofi Pasteur, which established a collaborative research and development agreement with WRAIR to accelerate further development of the vaccine.

Adapted from press release by NIH and Walter Reed Army Institute of Research

Scientists find why it is difficult to create vaccine for Hepatitis C virus

Researchers have been trying for decades to develop a vaccine against the globally endemic hepatitis C virus (HCV). Now scientists at The Scripps Research Institute (TSRI) have discovered one reason why success has so far been elusive. Using a sophisticated array of techniques for mapping tiny molecular structures, the TSRI scientists analyzed a lab-made version of a key viral protein, which has been employed in some candidate hepatitis C virus vaccines to induce the body’s antibody response to the virus. The researchers found that the part of this protein meant as the prime target of the vaccine is surprisingly flexible. Presenting a wide variety of shapes to the immune system, it thus likely elicits a wide variety of antibodies, most of which cannot block viral infection. The report, published online ahead of print by the Proceedings of the National Academy of Sciences the week of October 24, 2016.

Key protein on hepatitis C virus, E2, is exceptionally flexible,
 helping to explain why scientists have had difficulty targeting
it with a vaccine. Credit: Christina Corbaci and Leopold Kong

The Law and Wilson laboratories have been working together in recent years to study hepatitis C virus structure for clues to successful vaccine design. In 2013, for example, the team successfully mapped the atomic structure of the viral envelope protein E2, including the site where it binds to surface receptors on liver cells. Because this receptor-binding site on E2 is crucial to hepatitis C virus’s ability to infect its hosts, it has an amino-acid sequence that is relatively invariant from strain to strain. The receptor-binding site is also relatively accessible to antibodies, and indeed many of the antibodies that have been found to neutralize a broad set of hepatitis C virus strains do so by targeting this site.

For all these reasons, hepatitis C virus’s receptor-binding site has been considered an excellent target for a vaccine. But although candidate hepatitis C virus vaccines mimicking the E2 protein have elicited high levels of antibodies against the receptor-binding site, these antibody responses–in both animal models and human clinical trials–have not been very effective at preventing hepatitis C virus infection of liver cells in laboratory assays.

To understand why, the Law and Wilson laboratories teamed up with TSRI Associate Professor Andrew Ward and used electron microscopy and several other advanced structural analysis tools to take a closer look at hepatitis C virus’s E2 protein, in particular the dynamics of its receptor binding site. Their investigations focused on the “recombinant” form of the E2 protein, produced in the lab and therefore isolated from the rest of the virus. Recombinant E2 is a prime candidate for hepatitis C virus vaccine design and is much easier to purify and study than E2 from whole virus particles.

One finding was that recombinant E2, probably due to its many strong disulfide bonds, has great structural stability, with an unusually high melting point of 85°C. However, the TSRI scientists also found evidence that, within this highly buttressed construction, the receptor binding site portion is extraordinarily loose and flexible in the recombinant protein. “It adopts a very wide range of conformations,” said study first author Leopold Kong, of TSRI at the time of the study, now at the National Institutes of Health.

Prior studies have shown that hepatitis C virus’s receptor binding site adopts a narrow range of conformations (shapes) when bound by virus-neutralizing antibodies. A vaccine that elicited high levels of antibodies against only these key conformations would in principle provide effective protection. But this study suggests that the E2 protein used in candidate vaccines displays far too many other binding-site conformations–and thus elicits antibodies that mostly do nothing to stop the actual virus.

Law and Wilson and their colleagues plan to follow up by studying E2 and its receptor binding site as they are presented on the surface of the actual virus. They also plan to design a new version of E2 or even an entirely different scaffold protein, on which the receptor binding site is stabilized in conformations that will elicit virus-neutralizing antibodies.

Citation: Structural flexibility at a major conserved antibody target on hepatitis C virus E2 antigen.
Authors: Leopold Kong, et., al.
Journal: Proceedings of National Academy of Sciences
Research funding: National Institutes of Health, Skaggs Institute for Chemical Biology
Adapted from press release by The Scripps Research Institute

New vaccine targets found for Plasmodium vivax Malaria

Thousands died and more than 13 million people fell ill with malaria caused by the parasite Plasmodium vivax last year. There is no vaccine for the disease, partly because multiple strains of P. vivax circulate globally, making it difficult to develop a vaccine. Now, researchers studying a protein crucial for the parasite’s survival have found two portions of that protein that do not vary across many strains. Antibodies against these portions of the protein protect against disease, according to researchers at Washington University School of Medicine in St. Louis. The study is available online in the Proceedings of the National Academy of Sciences.

“This protein – called Duffy binding protein – is the most promising target for vaccine development because it is almost impossible for the parasite to cause infection without it,” said Niraj Tolia, associate professor of molecular microbiology and the study’s senior author.

If the parasite does not bind to the human protein – either because antibodies block the binding site or because the human protein is missing – the parasite is unable to cause disease. P. vivax is found all over the world, but it causes relatively little disease in Africa, where many people lack this specific protein on their red blood cells.

Tolia and colleagues studied three antibodies that are known to prevent a range of binding proteins from latching on to the human protein, and identified the portion of the binding protein to which the antibodies were bound. Two antibodies bound to the same portion, or epitope, while the third bound at another spot. “Our study helps define what we should be targeting to get universal protection,” Tolia said.

Press release: Vaccine targets identified for deadly form of malaria