Algae-based oral recombinant vaccines

Journal Article.pdf

In this journal article, the authors present to us plant-based vaccines as a real solution to impacting worldwide death rate due to infectious diseases. Infectious diseases directly account for 25% of deaths in the world. Traditional vaccines are expensive to administer from all points of view, let it be from availability, infrastructural, development, and medical personal availability. Furthermore, this high associated cost of vaccine delivery hinders the development of new vaccines for diseases that could be prevented.

The added value of plant-based vaccines is that it is orally administered and thus elicits both mucosal and systemic immunity. Additionally, they avoid the associated high costs, the need for trained medical personnel, reduce the risks of infections associated with syringes utilization and improved safety compared to traditional recombinant vaccine since there is no risk of infections by mammalian pathogens. It was estimated that the cost of plant-produced vaccines might be as much as a thousand times less than traditional vaccine production.

However, plant-based vaccines have still not made it through licensing except for one product, a veterinary injectable vaccine against Newcastle disease virus in poultry made from purified antigen expressed in cultured tobacco cells. This is explained by the low yield of the protein, less than 1% total soluble protein (TSP) in lettuce, tomato, potato, and tobacco. Even with the help of improved techniques in recombinant viral vectors or Agrobacterium mediated transformation, the end product has still a low yield and is unstable (uneven expression across the plant).

Plant-based vaccines are still the subjects of many researches as plant cells are attractive for oral vaccines. Their rigid cell walls protect the antigen through the stomach into the intestines so that they can access the gut-associated lymphoid tissue. Unfortunately, the inedible tobacco plants have proven to be the highest-yielding plant in the land species.

Green microalgae has recently attracted the interest of many industries. It has proven to be a very competent protein production platform even when dealing with complex proteins.  It has also showed that it can yield product as high as 10% TSP with a sophisticated cellular folding machinery. It has already been used to produce full-length human antibodies with varying expression rate.

The advantages conferred by those unicellular green algae are many. They have all the qualities of plant systems and numerous unique ones over terrestrial plant as vaccine production manufactory.  Indeed, the utilization of algae allows for rapid biomass accumulation and the entirety of the biomass is utilized for target protein production without having to waste energy on supporting tissue that do not produce the target protein or can’t be harvested. The authors also remind us of the importance of the fact that algae are not restricted by season, soil fertility and cross contamination risks. Furthermore, they can easily be grown in enclosed bioreactor for higher yield production, withstand long storage period at room temperature when dried, and can endure the harsh conditions of the stomach such as low pH with low antigen degradation, making them the perfect host to produce edible vaccines.

Algae have been used as vaccine production host in the past with some success. It was discovered that codon optimization was critical for high yield and for the oral administration to be effective, the antigen had to be fused to a known mucosal adjuvant such as the beta subunit of cholera toxin (CTB). During a pre-clinical trial, mice were fed freeze-dried algae for 5 weeks and 80% of them survived a lethal challenge with Staphylococcus aurea that killed all control mice within 48hrs.

The authors summarize all the algae produced vaccine up to this day and enumerate the progresses that have been done on algae research; however, the predominant problem is still the low yield of target gene. It is important to note that all those experiments were done for the most part on the same alga model organism C. reinhardtii, and that we are still in early research phase of algae produced vaccines (less than 11 years). The authors also remind us that the advances made on this model organism can be readily applied to other organisms more suited for mass vaccine production. Furthermore, algae have proved to be having a complex folding machinery for heavily disulfide-bonded proteins and are reliable—keep in mind there is no glycosylation machinery in algal chloroplasts.

There is no doubt in the authors’ minds that algae are the right hosts to produced complex vaccine antigens, and that this point was proven repeatedly in the past. For the authors, it is a question of fine-tuning the method. Indeed, even though CTB is the favored adjuvant, fusion of the protein with this adjuvant has been suggested to impair CTB’s activity. This led to many other adjuvants being researched for oral administration. The authors suggest that future work should be directed into finding the proper antigen adjuvant fusion combination as well as optimization the expression levels.

For the authors the future of algae produced vaccine is not to be questioned, but defined and refined. Indeed, given the low associated costs and logistical requirements, the authors go as far as stating that plant or algal production may be the only available option for large scale inexpensive and efficient vaccination. The authors call for investors and the pharmaceutical industry as well to seriously consider this avenue and give it the attention it deserves.

What do you think?

Y.S.H.

Neuralstem Cell Therapy for ALS

I haven’t written in a long time but needed to share that little piece of news… that is bringing great joy to my heart. I am impatiently waiting for the results… I hope it went well:

Product status:
U.S.: FDA-approved NSI-566 Phase II trials commenced in September 2013, and concluded final surgeries in July 2014. Phase II concludes after six-month observation period.
Mexico City: NSI-566 Phase I / II trial expected to commence in 2014
Mechanism of Action: Rebuilding neural circuitry
Route of Administration: Direct injections into the spinal cord

Neuralstem is seeking to treat the symptoms of ALS via transplantation of its NSI-566 human spinal cord stem cells (HSSCs) directly into the gray matter of the patient’s spinal cord. In ALS, motor neurons die, leading to paralysis. In preclinical animal work, Neuralstem cells both made synaptic contact with the host motor neurons and expressed neurotrophic growth factors, which are protective of cells. View published papers here: 1, 2, 3.

Neuralstem initiated the first FDA-approved stem cell trial for ALS in January 2010, at Emory University. This Phase I safety trial, to evaluate the safety of the NSI-566 cells and surgical technique, was designed to enroll up to 18 patients. The Principal Investigator is Eva Feldman, MD, PhD, Director of the A. Alfred Taubman Medical Research Institute, Director of Research of the ALS Clinic at the University of Michigan Health System, and President of the American Neurological Association. The Site Investigator is Jonathan Glass, MD, Professor of Neurology, Emory School of Medicine and Director of the Emory ALS Center. The trial was awarded an Orphan Drug Designation by the FDA in February 2011.

In humans, Neuralstem expects that the transplanted cells will:

GRAFT permanently into the region where they were transplanted
REBUILD circuitry with the patient motor neurons
PROTECT patient neurons from further ravages of the disease

In a review of the safety data from the initial nine patients, Neuralstem cells were deemed to be safe, with no adverse reactions reported believed to be related to cells or surgical technique.
Neuralstem ALS Trials

Neuralstem concluded final surgeries in the company’s NSI-566/ALS Phase II trials in July 2014. This phase of the study will conclude after a six-month observation period. The Phase II trials were approved by the FDA to commence in April 2013, upon conclusion of the Phase I FDA-approved trial to test the safety of the neural stem cells and transplantation surgery in patients with ALS in February 2013. The National Institutes of Health and ALSA committed to generous grants in funding for the Phase II phase of the study.

The NSI-566/ALS Phase II dose escalation and safety trials commenced in September 2013, and expanded to three centers: Emory University Hospital in Atlanta, Georgia, site of Phase I; ALS Clinic at the University of Michigan Health System, in Ann Arbor, Michigan, and Massachusetts General Hospital in Boston. The trials were designed to treat up to 15 patients, in five different dosing cohorts. The final cohort have received a total of 16 million NSI-566 neural stem cells, through 40 surgical injections of 400,000 cells per injection. (Phase I maximum was 15 injections of 100,000 cells each.) All of the patients were ambulatory and resided within close geographic proximity to the research center where they participated. The first 12 patients received injections in the cervical region of the spinal cord only, where the stem cells could help preserve breathing function. The final three patients underwent lumbar transplantation and returned for the cervical treatment during a second surgery.

The Phase I safety trial enrolled 18 patients. The trial began with 12 late- to mid-stage patients who received a series of injections in the L2-L4 lumbar region. The first six patients were all non-ambulatory with permanent paralysis. Of these, the first three patients (Cohort A1) were treated with five unilateral cell injections, while the next three patients (Cohort A2) received ten bilateral injections in the same region. The trial then progressed to patients who were ambulatory. The first three of these (Cohort B) received five unilateral injections. The next three patients (Cohort C) received ten bilateral injections in the same lumbar region.

Neuralstem received approval from the FDA to move into the cervical (upper back) stage of the trial in the fall of 2011. The first of six patients in the cervical cohorts to receive stem cells was treated on November 18, 2011, which marked the first FDA-approved intraspinal surgical transplantation of stem cells into the cervical region. The trial then advanced to the final cervical cohort of three patients. The FDA approved the return of three patients from earlier cohorts to receive cervical transplants, making them the first to receive stem cell transplantation in both the lower and upper parts of their spinal cord. The first of these was treated in June 2012, and received five stem cell injections into the cervical region of the back, for a total of 15 injections, including the ten lower-back injections previously received. The last patient in the Phase I trial was treated in August 2012. The trial was designed as a safety trial to treat 18 patients, and concluded six months after the final surgery.