Archive for the “Immunology” Category
So, we thought the worse was over; we thought we are done fighting the bad guys, HIV, SARS and H1N1A, but now it seems that a new menace is eminent. Our chaotic and rather foolish use of antibiotics have created this unknown danger that could add a new chapter to the history of medicine and fighting infectious diseases. This danger is called New Delhi metallo Beta-Lactamase -1, AKA NDM-1
Meet the Bug
In December 2009, a super villain appeared on the scene; he’s violent, resistant and determined to do as much damage as he could. Our super villain is the NDM-1 (New Delhi metallo beta lactamase – 1), a newly emerging beta-lactam resistance enzyme including carbapenems, which are one of few alternatives used for antibiotic-resistant bacterial infections. The NDM-1 gene is classified as a Carbapenemases . The enzyme is named after the city in which it first appeared, New Delhi, the Indian capital. In December 2009, a Swedish patient in India acquired an antibiotic resistant infection. Being unsuccessfully treated in India, the patient was further transferred to Sweden. The carbapenem-resistant Klebsiella pneumoniae was identified carrying the novel NDM-1 gene. A later study in India found that carbapenem-resistant strains from patients in India carried the NDM-1.
In May 2010, an E. coli expressing the NDM-1 gene was isolated from a patient in the UK, the patient was of Indian origin and had visited India 18 months ago where he had been undergoing dialysis. According to CDC Morbidity and Mortality Weekly Report (MMWR) , as of June 2010, three Enterobacteriaceae isolates carrying the NDM-1 gene were discovered in the U.S., which were E. coli, Klebsiella pneumoniae, and Enterobacter cloacae, NDM-1 provided the three isolates with resistance to all antibiotics except for Aztreonam. Fortunately to the bacteria but unfortunately to our patient, the isolates conferred resistance even to Aztreonam by different mechanism other than the NDM-1, and the MMWR established that all the three U.S. isolates were related to patients who had medical care in India.
Furthermore, a team in India in July 2010, reported cases of Acinetobacter baumannii carrying the NDM-1 in India. A recent study by a multinational team published in “The Lancet Infectious Diseases, September 2010” reported that the isolation of 44 isolates with NDM-1 in Chennai, 26 in Haryana, 37 in the UK, and 73 in other sites in India and Pakistan. NDM-1 was mostly found among E. coli (36) and Klebsiella pneumoniae (111), which were highly resistant to all antibiotics. Luckily, all the studies have confirmed that all NDM-1 isolates were susceptible to the antibiotics tigecycline (the FDA-approved glycylcycline antibiotic developed by Francis Tally and marketed by Wyeth under the brand name Tygacil®), and colistin (polymyxin E antibiotic, which causes nephrotoxicity and neurotoxicity at high dose IV). Some unconfirmed reports indicate the NDM-1 appearing in Canada and Japan earlier this month (Sep 2010).
In June 2010, patient zero –the first reported death– was a Belgian man who had a car accident in Pakistan, first being treated in a hospital in Pakistan and he became infected with the Bug carrying the NDM-1. He was further transferred to Belgium where he was hospitalized with major leg injury, and despite being administered colistin, the patient died!
We now face a new challenge. Could this superbug mean the end of the beta-lactam antibiotics era?!
Tags: bacterial resistance
, escherichia coli
, klebsiella pneumoniae
, resistant strains
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Posted by: rose in Immunology
Cancer: An abnormal uncontrolled proliferation of cells. The immune system doesn’t show any response, as the cancer cells are just some normal cells, which have gone crazy. That means that they could deceive our immune system, which recognizes them as normal.
The point of weakness
Cancer cells usually express so-called cancer-specific antigens, which are not otherwise expressed by normal cells.
Using these antigens as a method of differentiation, we have to teach our immune system to wipe out these cells without affecting the innocent normal ones.
Whole cell vaccines: using tumor cells, derived from a patient or many patients or use human tumor cell lines designed in lab. This will elicit the immune response for all the antigens on cancer cells.
Antigen vaccines: using a specific antigen on the cancer cell through identifying a certain gene, then cloning the gene, which encodes for it.
Adjuvants: using chemical substances to enhance T-cell response such as Interleukin-2 “IL2″.
Vector: using viral vectors to deliver the gene of interest to cells, which makes the cancer more visible to the immune system.
One major obstacle facing cancer vaccines is that the response is not readily measurable. For chemotherapeutic drugs development, the end point is usually progression-free survival, which has shorter-term outcomes. Cancer vaccines are characterized by longer-term outcomes and increased survival rate.
For more information, Read here.
, antigen vaccine
, cell lines
, survival rate
, viral vector
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Not too long ago, I read about a research done at the Kennedy Institute of Rheumatology Division, which has identified a new ligand for Toll-like receptor 4. This receptor was previously known for activating the immune system through the detection of threats as lipopolysaccharide or gram-negative bacteria. The new ligand, Tenascin-C, is an extracellular glycoprotein, whose elevated expression in cases of inflammation provoked scientists to study its role in the process.
The study noted that its presence was critical to maintain the ongoing inflammation seen in cases of rheumatoid arthritis. In reference to this study, the author stated “We have uncovered one way that the immune system may be triggered to attack the joints in patients with rheumatoid arthritis. We hope our new findings can be used to develop new therapies that interfere with tenascin-C activation of the immune system and that these will reduce the painful inflammation that is a hallmark of this condition”
I was able to contact Dr Kim Midwood and obtained this brief interview:
1. Do you have any speculations as to why Tenascin-C is overly expressed in certain individuals causing prolonged inflammation cases, whilst remaining within normal levels in others?
What regulates tissue levels of tenascin-C is not currently known and this is something that we are working on finding out.
2. From the different ligands of TLR4, why was Tenascin-C of particular interest in your research?
I have a long standing interest in how cell behavior is influenced by the extracellular environment, and in particular the role of extracellular matrix proteins in regulating cell phenotype during the response to tissue injury. For the last 10 years, I’ve been studying the role of tenascin-C – a protein specifically and transiently expressed upon tissue injury, but persistently expressed in chronic inflammatory diseases such as rheumatoid arthritis. This pattern of expression, plus the high homology of tenascin-C domains to other known pro-inflammatory matrix molecules or ‘DAMPs’ prompted us to investigate whether tenascin-C was an endogenous activator of the immune response and whether its persistent expression in RA contributed to disease pathogenesis.
3. What do you think the extent of similarity will be between the mice & human response to the Tenascin-C blockage?
I cannot predict how differently the mouse and human will behave.
4. Do you suspect a certain mechanism of the increase in inflammatory molecules caused by Tenascin-C?
We know that tenascin-C activates TLR4, activation of this receptor is well known to induced the expression of pro-inflammatory genes via activation of many intracellular signaling pathways.
5. How do you see the potential of such study for rheumatoid arthritis patients?
We plan to identify ways to inhibit the pro-inflammatory action of tenascin-C in the hope that this may be useful in reducing chronic inflammation in the joint.
Original research paper: Tenascin-C is an endogenous activator of Toll-like receptor 4 that is essential for maintaining inflammation in arthritic joint disease. Nature Medicine 15, 774 – 780 (2009). PMID: 19561617 (Vote for the abstract on Biowizard)
Image Credit: Davidson College Undergraduate Course
Tags: chronic inflammation
, intracellular signal
, Kim Midwood
, rheumatoid arthritis
, rheumatoid therapy
, Toll-like receptor
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A team of Harvard scientists has taken the first step to solve mystery about why HIV patients are more susceptible to TB infection.
According to USAID, 42 million people are HIV infected & almost one third of them are also TB infected. It is believed that HIV interferes with the cellular and molecular mechanisms used by the lungs to fight TB infection.
This mystery has been solved when scientists extracted immune cells called “alveolar macrophages” from the lungs of asymptomatic HIV +ve patients as well as healthy patients ” HIV –ve.” They observed a decrease in response towards TB bacterium in HIV +ve patients when compared to HIV –ve patients.
A further examination of lung specimens showed an increased level of a molecule called IL-10, which elevates the amount of a protein called “BCL-3″ in alveolar macrophages and this reduces their ability to ward off TB infection.
It seems that HIV increases severity of TB infection, where both represent two of the most significant health challenges in human history.
Source: Science Daily.
Image credits: The HIV replication cycle.
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This is not a prison break scheme. I was shocked to hear on BBC that researchers published a study, in the journal Genetic Vaccines and Therapy, about a new route for the delivery of specifically DNA virus vaccinations. Using the vibrating needle, normally used in tattoo parlors, they first experimented with mice & found a 16-fold increase in the humoral & cell-mediated antibody response elicited by these animals compared to the intramuscular injection. The needle implants small DNA fragments into the epidermis, which triggers a non-specific immune response believed to be the reason for the higher antibody levels found despite the lower dose of DNA used.
Flattering as it sounds, a lot of skeptics doubt that it would become a complete replacement of the conventional routes currently in use. It does not come without a cheap price either. Many tattoo lovers loathe the accompanying pain. Plus, potential users won’t be getting a tattoo in the process either because the needle won’t be loaded with ink.
Just truly amazed at whoever first comes up with such ideas and tries putting them to the test.
Image Credit: Enquirer
, Gene Therapy
, immune response
2 Comments »
Researchers at Penn state discovered two new proteins which activate cells in the immune system & cause a rare form of blood cancer.
Helper T-cells can stimulate B lymphocytes to produce antibodies against the pathogen. Also, stimulate cytotoxic T-cell that kills infected cells.
Shortly after the elimination of pathogen, most of cytotoxic T-cells die while few of them remain to protect the body from re-infection with the same pathogen.
In some cases of autoimmune diseases these cells don’t die, but they expand & attack many tissues as bones to cause rheumatoid arthritis “RA” or bone marrow to cause leukemia.
Researchers at Penn state tried to find out conditions that cause abnormal expansion of these cells, they made an intricate computer modeling which follows up signals involved in either activation or death of these cells.
The researchers have found two proteins “IL-15 and PDGF” which are needed to cause activation & proliferation of T-cells. IL-15 causes activation, while PDGF stimulates their growth.
Another signaling protein called “NFκB” controlled by the two proteins which prevent the death of cancer cells whatever they are over expressed.All those proteins may become targets for drugs; when they blocked NFκB with drugs in cells from leukemia patients, an increase in mortality of abnormal T-cells has been observed.
So, the key is to find out what stimulates T-cells to survive & proliferate.
Source: Science Daily.
Image credits: Immune response.
Tags: cytotoxic T-cell
, intricate computer modeling
, Penn state
, rheumatoid arthritis
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Normally when we hear the word immunity, we think of defense against infections, graft rejection, inflammation, etc. But, what if this defense may cause more damage than the infection itself ? In this case, the immune system shows a certain privilege through acting smarter where it deviates its mechanisms in a way to down-regulate its own damaging mechanisms. This whole process is known as Anterior Chamber-Associated Immune Deviation (ACAID).
image credit: http://research.opt.indiana.edu/
ACAID is endogenous to specific sites such as the anterior chamber of the eye and the brain. The process is considered as saving in cases of ocular infections where the visual axis is easily deflected by inflammation leading to blindness. Also ACAID is considered beneficial in case of allografting as it downregulates the immune processes responsible for allograft rejection. The process was discovered by Medwar in 1940, when he first noticed that surprisingly certain tumors proliferate more rapidly in the anterior chamber of the eye than anywhere else. Medwar’s further studies demonstrated the role of the process in transplantation immunology.
As an example of ACAID, upon antigenic inoculation of anterior chamber of the eye, the immune deviation presents itself as follows: Instead of Natural Killer T-cells perform certain functions attributed to T-Helper & T-Cytotoxic cells, the antigen injected into the eye APCs (Antigen Presenting Cells) that carry antigen to the spleen. These APCs activate NKT cells which in turn produce certain cytokines as TGF-ß that induce the generation of CD8+Tr cells which by production of cytokines such as TGF-ß and IL-10, can downregulate subsequent Th1-mediated DTH reactions against the same antigen.
image credit : http://www.nature.com
Thus, regarding the beneficial effects that can be drawn from ACAID, current research is being conducted for inducing ACAID to avoid graft and transplant rejection. ACAID can be induced by animal injection with non-ocular APCs, e.g., peritoneal exudate cells (PECs) that have been precultured with TGF-ß and antigen in vitro. Such procedure is believed to be a step forward toward the success of transplantation.
Tags: Anterior Chamber Associated Immune Deviation
, T cells
, Visual axis
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“It’s an honor to announce that we’ve successfully discovered, cloned & characterized the densonucleosis virus (DNV) Antigen, which will be able to infect Anopheles gambiae. That will hinder its ability to transmit Malaria parasite, Plasmodium or, at least, reduce its lifespan. I’ve to tell you this: This will be the latest in Malaria control.” Well.. those are my words but, of course, it is not my discovery. It’s the team of researchers from Johns Hopkins who discovered it. To realize how big it’s; we first need to know the previous approaches & trials in Malaria control.
To think, just think, about control/ prevention of any of those vector-borne parasites; automatically researchers think about these:
1- Prevent infection – disease – transmission.
2- By looking at: the parasite’s life cycle – the mosquito – the human immune system.
3- So, it’ll look like that: get humans vaccinated – develop genetically modified mosquitoes incapable of transmitting the parasite or simply “I was so naive to think that it’s simple” kill them with insecticides (anti-vector measures) – target the parasite at any stage of its life cycle.
For decades, DDT (dichloro-diphenyl-trichloroethane) & Chloroquine were successfully used in eradication of Anopheles & Plasmodium respectively, “I do like this word, makes me sound like a pro”. Chloroquine was used in treatment as well as prevention, till the emergence of chloroquine-resistant Plasmodium parasites and DDT-resistant Anopheles mosquitoes. Yes, they overcame the humans’ arsenal. So, preventing spread of resistant parasites is the #1 priority.
We can’t talk about all control strategies today, so we’ll talk about anti-vector measures. What do they use in control programs as anti-vector measures?
1- Insecticide-treated bednets (ITNs) & long-lasting ITNs (LLINs) it helped kids to survive. The only allowed insecticides to be used in ITNs are pyrethroid insecticides, so when the pyrethroid resistance emerged, as usual, it was really bad.
2- Indoor residual spraying (IRS) using DDT
One word about the mechanism of action of DDT & pyrethroids, both target voltage-gated Na-channels. So, when a set of mutations change the protein structure; Congratulations! It’s resistance to both DDT & pyrethroids.
3- New approach: Molecular talk; Know more about “blood meal” host selection. Yes, Anopheles smells the host, so researchers want to identify that pathway.
4- Another new approach: They are investigating genes which encode proteins that may interrupt the development of the parasite in the Anopheles.
The latest as an anti-vector measure is using Paratransgenesis or “the genetic manipulation of insect symbiotic (mutualistic, commensal or parasitic) microorganisms”, I can’t get the term or the definition. I’ll say it like that: “Any other m.o. has a relationship with the vector”. The steps are:
1- Know the Ag (Pick the gift)
2- Get the gene(s) engineered to be successfully expressed (Wrap the gift)
3- Delivery to Anopheles (Deliver the gift)
So the gift will be the non-enveloped ssDNA virus called (DNV). Its genome is very small, when they say for a viral genome that it’s small, so it has to be small (4–6 kb). The entire genome can be placed in a plasmid.
Back to the story of the discovery, they were doing a totally unrelated experiment when they found that strange band/ zone. They isolated it from the gel, cloned, sequenced, ran through BLAST which showed that it looks like DNV of Aedes aegypti (AeDNV) but not the man himself. They did multiple tests to identify the Ag, e.g. Immunofluorescence assay. There was a trial to infect Anopheles gambiae with DNV of Aedes aegypti which wasn’t successful in infecting adults from Anopheles gambiae. But the novel “AgDNV is highly infectious to An. gambiae larvae, disseminates to adult tissues, and is passed on to subsequent generations.”
, anopheles gambiae
, anti-vector measures
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Aetiology and epidemiology
Meninigococcal meninigits and septicemia are devastating diseases caused by Neissieria meningitidis. Although infants and young children are the most susceptible to the disease, adults are also affected but with less incidence. N.meningitidis is a gram negative capsulated bacterium that has been classified into five serogroups (A, B, C, Y, W135) based on their polysaccharide capsule.
Over forty years, developing a vaccine against this dangerous bacterium proceeded with little success. In 1960, the purified polysaccharide antigens were used to develop a vaccine against four groups (A, C, Y, W135) . Unfortunately, this vaccine was highly effective in adults but didn’t give protection to young infants and children who represent the age group most susceptible to the disease. Another challenge is that this vaccine didn’t show success against serogroup B (known as:MenB).
More attempts to overcome the new challenge
Using capsular polysaccharide antigen, as a vaccine against MenB, wasn’t a very good idea. This is due to the fact that MenB capsular polysaccharide is highly similar (nearly identical) to N-acetyl neuraminic acid which is widely distributed in human tissue and that means it is a self antigen. The new vaccine was poorly immunogenic (and thus provide poor protection) and also it might elicit auto-antibodies.
As scientists never give up, they switched into the new trend in vaccinology: Reverse vaccinology. Due to the formerly mentioned, N.meningitidis was expected to be a very promising candidate for reverse vaccinology.
RV provides help
Using in silico technique (computational biology), the genome sequence was fed into a computer, 570 proteins of the bacterium surface were predicted. Going for more refinement, only 350 of these proteins were successfully expressed in E.coli and and used to immunise mice. The sera assays allowed the identification of certain proteins that elicit bactericidal antibodies and surprisingly, were conservative among different strains and this meets the criteria for a good vaccine.
As research is proceeding to deprive our pathogen from enjoying its life inside our bodies, this work suggested further research of other pathogens such as: Streptococcus pneumoniae, Chlamydia pneumoniae, Bascillus anthracis, T.B and group B Streptococcus.
A universal vaccine against serogroup B meningococcus.
, reverse vaccinology
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For many decades, conventional vaccinology has faced many obstacles. One major problem is that among several antigens of the microbe, you have to identify the most immunogenic (and thus protective) antigens (such as virulent factors, toxins, surface-associated proteins, etc.) suitable for vaccine development. This process is very fastidious and costs a lot as it relies mainly on traditional biochemical and microbiological methods. As a summary, it is carried out as following:
- Firstly, you have to cultivate the microbe and harvest proteins.
- Then you have to identify the antigens one by one.
- After that you can pass to vaccine development stage.
Introducing genomics has greatly contributed to providing a new impulse to vaccinology field. The major role it plays is in the antigen discovery stage. As the genome sequence of many microbes has been identified, the integration between the sequence, proteomics and microarray has introduced what is called “reverse vaccinology” . Reverse vaccinology (RV) means to identify and characterise the antigen using bioinformatics. In RV, you start from the genome and not from the pathogen itself i.e. you start from the opposite direction, that’s why it is called “reverse”.
RV will provide solutions to some problems that usually come up during vaccine development as:
- It will provide fast access to almost all antigens including:less common antigens and antigens not expressed in vitro.
- It represents a new approach for non culturable microorganisms.
On the other hand, the major disadvantage of RV is that it cannot be applied to non-proteinaceous antigens such as lipopolysaccharides and glycolipids.
, reverse vaccinology
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