Category: Animal Experimentation (page 1 of 2)

Authors of PLOS One Study on Benefits of Electro-Acupuncture Answer My Questions

Early last month, I communicated in a blog post a few questions I had about a study in Electro Acupuncture published in PLOS One. It took the authors a while to get to them, but the senior and corresponding author of that study, Professor Kai-Liang Wu, of the Fudan University Shanghai Cancer Center, graciously wrote a detailed reply to my question a week ago. I am going to put his response in this space in blocks. For better comprehension, I shall put my questions in italicized letters followed by his response; the boldface types are for emphasis, mine. My comments are interspersed with the blocks.

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Questions for Authors of Study on Benefits of Electro-Acupuncture After Brain Radiotherapy

The April 1 issue (-giggle-) of PLOS ONE published an article on the alternative medicine modality of electro-acupuncture (EA) by a group of investigators from Shanghai, China (DOI: 10.1371/journal.pone.0122087). The basic premises of the study are sound:

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Inflammation, Acupuncture, and HPA axis: Faulty Science Clouds Understanding

In the wake of my recent critique of acupuncture being touted as a remedy for allergic rhinitis, I was pointed (via a Twitter comment) towards a 2013 review in Evidence Based Complementary and Alternative Medicine, which purported to propose a mechanism for the much-claimed anti-inflammatory effects of acupuncture. There are several putative mechanisms, discussing all of which will make this post gargantuan. Therefore, I shall focus on the explanation involving the hypothalamus-pituitary-adrenal (HPA) axis.

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Bug’s “To-do”: Lose a few genes; Cause the Black Death

Yersinia pestis (YP) is a rod-shaped bacterium associated with the pandemic plagues that have devastated human civilization multiple times. According to available genetic evidence, an ancestral bacterium called Yersinia pseudotuberculosis (YPT) gave rise to this bug in China, from where it spread repeatedly westward to the rest of the world causing disease in both animals and humans.

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Lies, misrepresentation, cherry picking quotes: PeTA’s tactics to garner support against animal research

I work with immunology of infectious disease and study host-pathogen response. My work has naturally involved a good amount of animal experimentation, especially mouse models of various infections. These mouse models are incredibly useful, because they offer a valuable window into the process of infection, pathogenesis (‘disease production’), and the kind of immune response a vertebrate mammal generates to the infection. The same broad reasoning applies to rodent models of various metabolic and endocrine diseases, as well as cancer. These models are attractive because most often these research animals are genetically homogeneous, and therefore, provide a less complex (and more manageable) environment to study the genesis, as well as treatments, of a disease – while mimicking much of the same physiological responses seen in larger and more complex animals.

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Urgent Help Requested By Belgian Scientists

My readers may remember a previous post detailing a crisis in animal-based research in Italy. Early this morning I received a note from the Basel Declaration Society alerting me to an urgent situation developing in Belgium. Scientific research with non-human primates appears to be in serious jeopardy in that nation, but it is hardly likely that the fallout from any anti-science policy prohibiting research will remain restricted to Belgium alone. Bioscientists from Belgium are asking for immediate help and support from the world science community; Prof Rufin Vogels, current President of the Belgian Society for Neuroscience, and his colleagues have formulated a petition to the Ministers of the EU and the members of the Belgian parliament. The Basel Declaration Society (to which I am a signatory) is supporting this petition; I am including the text of the petition. Please read it and consider signing.

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Italian Biomedical Scientists Petition EC Officials and Italian Politicians Protesting Extreme Restrictions on Animal Research

I have written earlier about the peril that Italian Biomedical research finds itself in, due to extreme, immoderate and unreasonable restrictions on animal experimentation that the Italian Parliament approved recently. Via a missive from the Basel Declaration society (Disclaimer: I am an individual signatory to and supporter of the Basel Declaration), I learnt this morning about a PETITION (in Italian, and in English) that several prominent Italian Biomedical Scientists have launched, directed at European Commission officials and copied to several relevant ministers in Italy.

I am including here the text of the English version of the petition. Please read, support and share it. The place to put your name, email, and optionally, location and degree, is to the right side of the petition text (see the petition page link above). The field-names are unfortunately written in Italian even in the English page, but they are not difficult to understand. Upon signing the petition, you’d receive an email with a validation link which you must remember to click in order for your signature to be registered.

Please stand with these scientists for the sake of not only saving Italian scientific research, but also maintaining the integrity and continuity of biological research as a whole throughout the world.

Dr. Janez Potočnik

European Commissioner for the Environment
Directorate General for the Environment
European Commission
B-1049 Bruxelles


Dr. Susanna Louhimies
Policy Officer- Use of animals for scientific purposes
Directorate General for the Environment
Unit 3
European Commission
B- 1049 Bruxelles


Minister of Health of Italy
On. Beatrice Lorenzini

Minister of EU Affairs of Italy
On. Enzo Moavero Milanesi

Minister of the University and Scientific Research of Italy
On. Maria Chiara Carrozza

Subject: Implementation in Italy of EU Directive 63-2010 on the protection of animals used for scientific research in Italy. Art. 13, Law n. 96/2013.

Dear Dr. Potočnik:

We are writing to share our concerns on the criteria approved by the Italian Parliament concerning the implementation of the European Directive 2010/63 on the protection of laboratory animals in Italy.

As a scientific community we have approved and supported the decision to generate an harmonized approach shared by the whole Community.  The European discussion has lasted almost a decade and has led to a well-balanced compromise between the demands of animal welfare and the interests of research.

This well balanced compromise has been challenged by the Italian Parliament with
severe risks for the future of biomedical research in the country.

We ask you to help re-balance the discussion by warning the Italian Government that the Parliament has approved decisions is in violation of art. 2 of Directive EU 63-2010. If transformed into a legislative decree by the Government,  those decisions  will make the Italian law much more severe and restrictive than the EU Directive.

Specifically we ask you to convince the Italian Government to implement in Italy the EU Directive 63-2010 as the UE Parliament and Commission have licensed it. This will require the rejection of the Art. 13 of the national law of implementation of the EU Directives for 2013 (Legge di delegazione europea 2013, n. 96, published in the Gazzetta Ufficiale, Serie generale n. 194, 20/08/2013, into force since 04/09/2013).

The different paragraphs of art. 13 of the above mentioned law contains a severe limitation to the use of cats, dogs and non-human primates for basic research, limitations in the re-use of animals of any nature previously employed in procedures classified as of “moderate” severity, prohibition of research on non-anaesthetized animals, limitation in the use of genetically modified animals, a ban of animal experiments on xenotransplantation and drug addiction, a ban of animal breeding centers in the national territory.

We trust that the strict control and ethical review mechanisms proposed by the EU Directive are the most effective mechanisms to prevent unnecessary and unjustified pain and suffering for animals. The Italian scientific community is very supportive of this strict review process but opposes any total bans, as fully inappropriate to regulate the complexity of biomedical research, and liable to damage it severely without adding significant benefits to animal welfare.

In the interest of biomedical research in Italy, we ask you to follow our recommendations and help us obtain a new and well balanced Italian animal welfare legislation, in line with the European directive.

Yours sincerely,

Fabio BenfenatiProfessor of Physiology, University of Genova

Giovanni BerlucchiProfessor Emeritus of Physiology, University of Verona 

Roberto CaminitiProfessor of Physiology, University of Rome SAPIENZA, Chair, Committee of Animals in Research (CARE), Federation of the European Neuroscience Societies (FENS)

Enrico CherubiniProfessor of Physiology, SISSA, Trieste, President of the Italian Society of Neuroscience (SINS)

Francesco ClementiProfessor Emeritus of Pharmacology, University of Milan, and National Council of Research, Milan

Gaetano Di ChiaraProfessor of Pharmacology, University of Cagliari

Silvio GarattiniDirector, Institute for Pharmacological Research Mario Negri, Milan

Jacopo MeldolesiProfessor Emeritus of Pharmacology, University Vita-Salute San Raffaele, Milan, past President of the Italian Federation of Life Sciences

Giacomo RizzolattiProfessor Emeritus of Physiology, University of Parma

Carlo ReggianiProfessor of Physiology, University of Padua, President of the Italian Physiological Society

Piergiorgio StrataProfessor Emeritus of Physiology, University of Turin

Italian Biomedical Research in Peril

Those of you who are familiar with my views on animal experimentation (e.g. see here and here) probably know and understand that in order for biomedical science to progress for the benefit of humans and animals, it is important to engage in reasonable animal experimentation. I emphasize the word ‘reasonable’, because the welfare and humane treatment of research animals remains one amongst the most important tenets guiding animal experimentation. These tenets also behoove us biomedical researchers to actively seek non-animal, alternative study methods wherever possible, and employ rigorous analytical tools to minimize the number of animals to be used.

At the same time, however, I also emphasize that animal experimentation remains a very important and crucial experimental tool. Let’s take an example that I came across in today’s Nature Medicine alert. SARS (Severe Acquired Respiratory Syndrome), a form of viral pneumonia, affects a variety of small mammals, a fortuitous fact which the scientists have utilized for over a decade to study the ways and means to stop this deadly coronavirus pathogen. However, the etiological agent of the so-called MERS (Middle East Respiratory Syndrome), another coronavirus (CoV) that is wreaking havoc in Saudi Arabia, doesn’t seem to be able to infect the usual subjects, small lab animals (such as rodents) – reports Elizabeth Devitt (DOI: 10.1038/nm0813-952) in Nature Medicine News. This has seriously hampered the search for a treatment or preventive vaccine. Teams of scientists have, of necessity, moved to a non-human primate model, Rhesus Macaques, in which the MERS-CoV does cause a form of disease that is less severe than one seen in humans. In this model, possible vaccine candidates, as well as two antiviral drugs, are to be tested.

All this is why I found a piece of news in a recent Nature News Blog highly alarming and disappointing. Reported Alison Abbott, Italian parliament approves sweeping restrictions to use of research animals.

As Allison explained, Italy, as a member of the European Union, was required to legislate the protection of animals used in scientific research, following a 2010 EU directive that was seen as striking “a delicate balance between animal welfare and the needs of biomedical research” but was also amongst the strictest of such regulations around the world. However, the Italian Senate introduced last month a series of amendments in favour of placing extreme restrictions on animal research:

  • Forbidding the use of non-human primates, dogs and cats – except to test drugs or perform translational research,
  • Mandating anesthesia use even in mildly and transiently painful procedures, such as injections, and
  • Prohibiting animal use in some specific research areas, such as xenotransplantation (transplantation of cells and tissues between species, an important research area associated with transplant medicine), and addiction.

Not surprisingly, the scientific establishment of Italy is crying foul, voicing the concern that these measures would seriously hinder important biomedical research in Italy. It is not difficult at all to see why they should feel this way. Allison’s blog post is followed (at the last reading) by an illuminating discussion by five illustrious commenters, some noted biomedical researchers amongst them: neuroscientist Prof. Stefan Treue (Director of the German Primate Center, and Professor of Cognitive Neuroscience and Biological Psychology, University of Göttingen), Constitutional scholar Prof. Francesco Clementi (Professor of Political Science, University of Perugia), neuroscientist Prof. Nikos Logothetis (Director, “Physiology of Cognitive Processes” Department, Max Planck Institute for Biological Cybernetics, Tübingen), neuroscientist Prof. François Lachapelle (Research director, National Animal Welfare Office, INSERM) and Science blogger Dr. Paul Browne of the Speaking of Research blog. I encourage everyone to head over to Allison’s blog and read these comments.

Paul Browne’s comment brought back to my mind an excellent 2010 post he wrote along with Dr. Allyson Bennett on the Basel Declaration, “a declaration that affirms commitment to responsible research and animal welfare and calls for increased effort to facilitate public understanding of the essential role that animal studies play in contributing to scientific and medical progress” (Full Disclosure: I am an individual signatory to the Basel Declaration).

Particularly in relation to the Italian legislation’s intent to allow animal research for some, but not all, biomedical research, this line from the Declaration is especially important:

“…Biomedical research in particular cannot be separated into ‘basic’ and ‘applied’ research; it is a continuum stretching from studies of fundamental physiological processes to an understanding of the principles of disease and the development of therapies.”

Paul’s comment after Allison’s post includes a note of hope. He wrote, “… it has become apparent that the voices of science are beginning to be heard by Italian politicians.” I hope that is true – not only for Italy, but across the world, especially in the US, as well.

Checking in…

Hello there! Did you miss me? I’m kidding. Of course you didn’t. Anyway, I have been really busy in boring academic work (yes, I do have to keep doing what I do at the bench – sigh!), and haven’t found time to sit down and write. This brief interlude hasn’t ended yet, but I am checking in to say a quick ‘Hi!’ to you, and put down a few good news that caught my eyes via the Nature News highlights that comes to my inbox.

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Tuberculosis and rational vaccine design

Commenting on a recent study from her institution (McMaster University, Ontario, Canada), published in the journal Mucosal Immunology, Dr. Stephanie Swift, my blog colleague at Scilogs and a postdoctoral scientist working in host-pathogen interaction, wrote the other day about how vaccines can be used to train the innate immune system to recognize and repel dreaded pathogens, such as Mycobacterium tuberculosis (“M.tb”), the bacterium responsible for tuberculosis (‘TB’). [I shall highlight a few related points here, but do go read her post: it is informative and interesting.]

Immunologically speaking, the body’s defence mechanisms are dual layered. The first line of defence, called “innate” immune response, is a non-specific, general system; it is comprised of barrier mechanisms that hinder the entry of micro-organisms, as well as an immune cell-based (‘cellular’) and a non-cellular, protein-based (‘humoral’) compartment. The second line of defence – a more robust, specific and sustained response – is provided by another system, called “adaptive” immunity, which also employs many cellular and humoral mechanisms. As the names suggest, innate immunity is ‘always on’; when microbes try to invade, innate immune mechanisms stave off the first attack, and help recruit the components of adaptive immunity. Adaptive immunity serves as immunological memory that primes and programs the defence mechanisms, so that in the event of a second attack, the immune system responds in a focused manner, targeting the specific invading pathogen.

Tuberculosis remains a significant threat to public health globally; co-infection with HIV has driven its resurgence despite efforts to reduce its impact. An estimated 1.4 million people succumb to TB each year (WHO, 2011), with the largest burden observed in Africa and Southeast Asia. Although anti-tubercular drug discovery has revived itself lately with renewed vigor, focusing on adaptive immunity has been the mainstay of immune-based TB therapies – as Dr. Swift pointed out in her essay, too.

And is there a good reason for this focus? Yes, it appears, there is, but we need to remember some fundamental facts about this pervasive pathogen. M.tb, which likely evolved from soil-dwelling ancestors to become a human pathogen around 10000 years ago, is endowed with unique abilities geared towards survival and persistence:

  • M.tb is considered aerobic-to-facultative-anaerobe, which means it normally grows in presence of oxygen, but if oxygen is deficient, it can shift to other mechanisms of respiration that doesn’t require oxygen.
  • When oxygen and nutrients are plentiful, and temperature is 37˚C (as, say, in the lungs), M.tb makes more copies of itself in 18-24h (3-4 weeks on artificial medium in vitro). For a pathogen, this is an extremely slow rate of division.
  • When conditions are not propitious, M.tb has the unique ability to enter a dormant, non-replicative state with low respiratory rate or metabolic activities. When in this zen-like state, it is not affected by either host immune mechanisms or anti-tubercular drugs (which otherwise kill the growing bug). It also modifies its metabolism, via genetic changes, to adapt to the nutrient limitations.
  • M.tb possesses an unusual cell wall, thick and impermeable, composed of complex sugars (polysaccharides), amino acid-containing sugars (peptidoglycans), sugar-containing fatty acids (glycolipids) and long-chain fatty acids (e.g. mycolic acid). It is these latter lipid-components that are considered to protect the bacteria against weak disinfectants and desiccation.

Mycobacterium tuberculosis, under acid fast stain
M.tb revealed with a special stain specific for Mycobacteria, acid-fast Ziehl-Neelsen stain; Magnified 1000X. Image courtesy: CDC/Dr. George P. Kubica (1979).

Macrophages, members of first-line defence, are immune cells that engulf microbes via a process called phagocytosis, and kill them internally by:

  • Creating an acidic (low pH) environment inside the bubble-like enclosure, called a phagosome;
  • Producing hyper-reactive (and corrosive) chemical derivatives of oxygen and nitrogen, which causes damage to microbial DNA, lipids, proteins and other structural components;
  • Flooding the microbes with enzymes which, under the acidic condition, can break down (‘hydrolyze’) lipids and proteins in the outer layers of the microbes;
  • Releasing peptides (small proteins) with potent antimicrobial properties (such as cathelicidin, hepcidin, etc.), which pokes holes into the outer layers of the microbe, and
  • Undergoing a regulated suicide process known as apoptosis, in case the microbe is able to escape its enclosure and wade into the cytoplasm, the fluid-filled intracellular space, of the macrophage itself.

Immune messenger proteins – called cytokines, notably Interferon-γ – secreted by certain immune cells influence these defensive process by acting on and activating the same and other immune cells. Macrophages and another immune cell, known as dendritic cells, can pick up pieces of the destroyed microbes and their products, and display it to yet another immune cellular component, the T-lymphocytes, at which point the immune response traverses to the adaptive side; T-lymphocytes instruct B-lymphocytes to produce specific antibodies against the microbe, and create memory B-lymphocytes and memory T-lymphocytes in preparation of subsequent attacks; other immune cells are also appropriately instructed to recognize the pathogenic components for unleashing their destructive power in a focused manner on the microbe in the event of the next attack.

But… M.tb’s unique abilities include not only escaping elimination, but also surviving inside macrophages. It is thought that their unusual cell-wall composition allows them to invade resting macrophages silently. Once inside the resting or active macrophages, M.tb can shut down the internal processes by which macrophages kill and digest microbes. In addition, virulent M.tb can prevent the macrophage from undergoing apoptosis by blocking the self-destruct signal and making quick repairs to the already-destroyed cellular structures. (Note: If you are familiar with Stargate SG-1, this is an easy parallel with Replicators!)

In addition, inside activated macrophages, M.tb can tolerate the low pH environment by reducing the macrophage protein pumps responsible for acidification, up-scaling the production of its own urease enzyme, which produces ammonia to neutralize the excess acid, and programming a set of its own genes called aprABC, whose functions allow it to adapt to the acidic micro-environment inside the host cells. Therefore, M.tb essentially reprograms the host cells after entry to prevent its own destruction and ensure its persistence.

And that is not all. Once inside macrophages, M.tb has the ability to use a host-derived carbon source (most likely, cholesterol and glycerol) for its metabolic needs;  it modifies both its lipid metabolism and its toxic waste disposal mechanism to suit its environment. To prevent damage from corrosive ionic derivatives of oxygen and nitrogen, M.tb enhances the production of several key enzymes (such as, superoxide dismutases, peroxidases, and reductases) that can neutralize these ions, as well as repair the damages caused. There is some evidence that macrophages may use excess zinc ions inside the phagosome to kill M.tb, but recently it was discovered that the bacteria can safely pump out the zinc ions. It even counteracts the effect of the antimicrobial peptides by neutralizing their negative charge via a positively-charged lipid molecule on its membrane.

But wait, there is more! Ordinarily, macrophages with engulfed microbes migrate to tissue sites, where other cell types, such as monocytes, lymphocytes, and neutrophils are signaled and recruited to create a confined environment, called a granuloma, where a delicate balance is established between the host immune cells and the pathogen. Formation of well-organized granulomas, comprising different immune cells, is a characteristic feature of several microbes, mainly some respiratory fungal pathogens (such as Cryptococcus, Histoplasma etc.), and – of course – M.tb. In TB, a primary lesion or point of damage becomes a solid granuloma involving macrophages, monocytes, dendritic cells, T- and B-lymphocytes; solid granulomata in lungs may represent foci in which M.tb remain in a latent, quiescent condition – but not dead. Under certain circumstances, especially if the host immunity falters for some reason, they can be reactivated, and progress to active disease. The granuloma in this case becomes necrotic or caseous (filled with dead tissue and dissolved material), which allows for the bacteria to escape its immune-prison chamber, and spread elsewhere via blood, and to other persons via breathed/sneezed out air from the lungs.

pulmonary tuberculosis - granuloma: A, airway; B, blood vessel; G, granulomata
Image: Necrotizing granulomas (G) localized around an airway (A). (B) is a blood vessel. ©Dr. Yale Rosen; you can view more of the pulmonary pathology photos by fabulous Dr. Yale Rosen on Flickr.

It is clear that while the host innate immune system, led by the macrophages, can boast of a remarkable arsenal of microbicidal mechanisms in general, when it comes to M.tb, their efficacy is not guaranteed; during co-evolution with mammalian hosts for thousands of years, M.tb has been conditioned to defeat the hostile intracellular environment and persist in the host. Therefore, it is hardly surprising that most of the current vaccine candidates are not aimed at preventing or eliminating primary TB infection, but focus on priming the players of adaptive immunity to stave off the emergence of active disease by targeting the metabolically active, replicating pathogen.

Vaccine antigens are antigens which, when used to immunize, prime the immune system to recognize the same or similar structures in the invading pathogens and mount an immune response. A booster is one or more subsequent doses of the same or similar vaccine antigens, designed to further hone the ability of the immune system to focus on the target. The desired effect of this strategy is the establishment of a state of immunological memory, which allows the immune system to respond more rapidly and effectively to previously-encountered pathogens. The memory responses – which are often the principal antimicrobial response in an immunized host – are dependent on antigen-specific B- and T-lymphocyte populations made up of genetically identical (‘clonal’) cells, and are known to also differ qualitatively from primary responses, in terms of both antibody production and T-cell memory.

For the longest time, we have had the BCG vaccine, derived from a cousin of M.tb, the Mycobacterium bovis strain Bacillus Calmette-Guérin. Following WHO recommendations, BCG is routinely administered to neonates or infants in parts of the world endemic for TB; BCG is at least partially effective in preventing development of serious TB manifestations in children, such as TB-meningitis and disseminated (“miliary”) TB. However, it appears that for some reason, BCG vaccination is unable to sustain immunological memory, the sine qua non for adaptive immunity; this leads to highly variable protection from pulmonary TB as far as adults are concerned. To counter this, various investigators have started considering combining BCG vaccine with another vaccine antigen in a prime-boost strategy designed to maximize the benefits of both. Recombinant BCG vaccines, with improved immunogenicity profile, are in clinical trials now.

In addition, several new candidate vaccine antigens are being studied. Incidentally, a team of researchers from my institution (Johns Hopkins University, Baltimore) also published this month an interesting study in PLoS One, in which they identified a potential vaccine antigen that can protect against TB meningitis. This antigen is an Mtb protein, known as PknD, whose function involves helping the bacteria cross the barrier – known as the blood-brain barrier – that ordinarily keeps microbes from entering the brain. They had earlier discovered that an antibody that specifically recognizes this protein is able to neutralize its action. Therein lies the rationale of this vaccine program, which can potentially produce such an antibody in an immunized person, as well as produce T- and B-lymphocyte memory of this protein. This would likely protect specifically against TB meningitis, a high mortality outcome of disseminated TB.

However, as I indicated before, during the period of latency/dormancy, M.tb modifies its genetic program; as a consequence, the character of the antigens usually associated with the bacterium changes, and separate antigens expressed by the dormant pathogen predominate. Therefore, many investigators now consider that a sustained and effective control of dormant M.tb would require the vaccine-induced immune response to recognize target antigens on the latent bacterium. Mouse studies are ongoing, with encouraging results, using a latency-associated M.tb antigen, a protein called Rv2660c, which is selectively expressed during nutrient starvation.  

The prime-boost immunization strategies, focused towards developing immunological memory, have shown promise in battling M.tb, but the mechanism of their actions, particularly how they impact innate and adaptive immunity is yet unclear.

In the McMaster study that Dr. Swift commented on, the researchers used two engineered (recombinant) viral vaccines; the gene for an immunodominant early secreted M.tb protein Ag85A, was inserted into either of two viral vectors, derived from the genomes of adenovirus (Ad) and vesicular stomatitis virus (VSV). Once these vectors are taken up into host cells, this protein would be continuously produced within the host cells, and serve as the vaccine. Using the prime-boost strategy in a mouse model, they found both elicited similar M.tb-specific T-lymphocyte responses (that is, adaptive immunity) in the lung and spleen.

However, the picture changed drastically when they challenged the immunized mice with the bacterium, and studied the signatures (a.k.a. markers) of protection. The Ad-based boosting regimen was able to greatly clear M.tb from the lungs and spleen of the mice, and elicit high levels of a macrophage-stimulating cytokine called IL-12 in the lungs. In contrast, the VSV-based boosting showed no enhancement of protection against TB, and even elicited high levels of another cytokine called IL-10, which profoundly shuts down the anti-M.tb activity of macrophages. These cytokines were released from phagocytic cells that represent innate immunity. Therefore, clearly, Ad-based boost strategy enhanced the activation of innate immune system in the lung, which presumably resulted in the greater protection to TB.

The researchers figured out that the main difference between the two vector vaccines was in how they interacted with – and primed – the innate immune cells at the site of immunization. IL-12 is known to enhance the production of interferon-γ, as well as of the reactive Nitric Oxides, from these immune cells. In short, the immune cells exposed to the Ad-based boost became more efficient killers of M.tb.

In contrast, the researchers found that exposure to VSV-based boost led to increased release of another cytokine, called interferon-β, which has grossly different actions compared to interferon-γ. Increased interferon-β severely blunted the beneficial IL-12 responses in the M.tb-infected phagocytic innate immune cells; in addition, exposure to interferon-β made the immune cells inefficient in controlling the numbers of engulfed (phagocytosed) M.tb.

Whereas T-lymphocyte mediated adaptive immunity is essential and beneficial for many microbial pathogens, effective elimination of pathogens that hide in plain sight within immune cells itself, such as M.tb and HIV, requires the engagement of innate immunity which encounters them first, independent of the T-cells. To succeed against M.tb, a vaccine would need to engage both wings of the defence. As Dr. Swift pointed out, each of the viruses from which the respective vectors were derived:

“… enters lung cells in a certain way, attaching at different sites, activating different intracellular pathways, expressing different viral products and consequently engaging different parts of the immune system.”

Viral vectors offer an attractive choice for engaging adaptive immunity against different pathogens. This study shows how they can be used to strengthen innate immunity, too. These are important considerations for a rational vaccine design.

Two major studies discussed:

  • Jeyanathan M, Damjanovic D, Shaler CR, Lai R, Wortzman M, Yin C, Zganiacz A, Lichty BD, & Xing Z (2013). Differentially imprinted innate immunity by mucosal boost vaccination determines antituberculosis immune protective outcomes, independent of T-cell immunity. Mucosal immunology, 6 (3), 612-25 PMID: 23131783
  • Skerry, C., Pokkali, S., Pinn, M., Be, N., Harper, J., Karakousis, P., & Jain, S. (2013). Vaccination with Recombinant Mycobacterium tuberculosis PknD Attenuates Bacterial Dissemination to the Brain in Guinea Pigs PLoS ONE, 8 (6) DOI: 10.1371/journal.pone.0066310
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