Cancer Immunotherapy Continued: Non-transgenic T Cell Therapy

A number of adoptive T cell therapies are being examined for cancer treatment including isolation and culturing tumor infiltrating lymphocytes (TILs), isolating and expanding a specific T cell or clone, and generating novel T cells with chimeric receptors designed to target tumor cells and provide robust activation signals to the T cell. 1,2

Recently, I wrote a short essay about CAR T Cell therapy and how this therapy uses genetically modified T Cells to generate a large number of your own cells, capable of targeting tumors bearing a known antigen (e.g. CD19 as a Lymphoma marker).

T Cells are one of the immune system’s specific attackers, capable of recognizing cells bearing specific antigen only. They are engaged and activated via interactions with APCs presenting antigen bound to MHC molecules as well as other ‘secondary’ signals.  For a more complete description, see

In the case when the T Cell recognizes the antigen, it proliferates and activates if provided sufficient secondary signals in addition to TCR stimulation. In the absence of recognition, the T Cells will not stably bind the APC and therefor not receive sufficient signaling to activate.

T Cells ‘see’ antigen through presentation in the context of MHC molecules on the surface of Antigen Presenting Cells (APCs)

Some benefits to that therapy include incorporation of a well-designed chimeric antigen receptor capable of providing normal T Cell Receptor (TCR) signals as well as signals from co-receptors required to generate mature effector cells. Because this construct targets the CD19 molecule directly, it does not require processing and presentation of antigen via MHC I by the tumor cells (important because one strategy tumor cells use to evade immune detection is to down-regulate MHC I). Using the patient’s own cells also means that immunosuppressive drugs aren’t required to prevent the body from rejecting the therapy.

One drawback though, is that the construct is made synthetically and can only include antibody binding regions specific to known cell surface antigens. So, if you know the cells you want to get rid of, and you can make an antibody to bind those cells preferentially, CAR T Cells are a good therapy for you.

Using Non-Transgenic T cells, similar effects can be obtained with an inverse set of pros and cons. Because this therapy does not utilize chimeric receptors, cells specific for a known  antigen aren’t singularly generated. Rather, a diverse array of cells is generated against tumor targets without requiring the isolation and characterization of one particular antigen. As opposed to the CAR T Cells these cells can only interact with target cells that present antigen via their MHC I molecules, which can be a drawback in situations where the tumor cells have downregulated antigen presentation molecules.

The Non-transgenic cells used may be generated in several ways. One method includes the harvest of tumor tissue from the patient, followed by killing these cells and re-injecting them (possibly in the presence of an adjuvant) to illicit a targeted immune response. 7-10 days later, peripheral T Cells enhanced for target specificity by the vaccine can be harvested and amplified outside of the body. In this way, cells can be amplified to numbers far outpacing what might be found in the patient, while also providing additional activation signals to promote effector cell development.

A second way of utilizing non-Transgenic T Cells in therapy is to isolate only those T Cells found to be actively invading the tumor. This biases toward cells already selected for by the immune system that may simply not be able to keep pace with the tumor’s growth. Ex vivo amplification can provide these cells the boost in numbers required to tip the balance in favor of the patient.

Coupling any of these therapies with other treatments, such as the human monocloncal antibody anti-CTLA-4 (ipilimumab) 4, can further support T Cell efficacy – in this case by blocking checkpoints used to dampen the immune response following a period of activation. In healthy patients, these checkpoints allow the immune system to revert to a state of homeostasis once pathogens have been cleared. In cancer patients, the tumor may not yet be eradicated before checkpoint molecules begin to dampen the response. By interrupting these, the window during which T Cells are most effective is widened — at least in some patients.

This article has been cross-posted on Medium

A Few References:
1. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3315690/
2. https://depts.washington.edu/tumorvac/research/t-cell-therapy
3. My Medium Post
4. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1951510/

 

Measles and immune memory

There’s more than one reason to immunize your kids.

Even if just not getting measles was all you got for your immunization, it would still be worth it. But through some unknown mechanism, getting measles seems to erase prior immunological memory, by depleting B and T lymphocytes (so, we know the cause, but not how this happens).

Below, is a visualization of individuals’ lymphocyte numbers pre and post measles:

Apparently, naive cells are either not impacted, or only minimally so. Whereas all specific lymphocytes are completely depleted. Following resolution of the infection, the only antigen-specific lymphocytes that remain afterwards are those specific to measles. That is, you now have the immune system of a toddler, with the sole exception of having immunity to measles. Recovering that lost immunity takes approximately 2-3 years of being exposed to and contracting infection after infection to rebuild memory.

One of the reasons that investigators knew that there was something to investigate was that once measles vaccine became available, not only did deaths associated with measles decrease, but so did deaths associated with a number of other infections.

 

Autism’s False Prophets Questions – Part II

A second installment in questions referring to Paul Offit’s book, Autism’s False Prophets. These questions mark the last of those we will cover for this book.

Autism’s False Prophets                                                                           Name:

Chapter 11 Questions

A Place for Autism

1. What evidence is there for a genetic cause of autism?

2. Other than genetics, what other things may cause autism?

3. Who is the Autism Diva, and where did she come from?

4. Who is Peter Hotez, and how did he get involved in the public conversation about autism?

5. What does Peter Hotez think is the hardest part of being parent to an autistic child?

6. What does Kathleen Seidel say is a problem about the way that doctors and scientists see the world?

6. As always, at the end of a book like this, I like to ask for your feedback on whether you found this book important, what it might lack, and whether you think that I should keep using it in future classes.

 

Autism’s False Prophets Questions

I’ve been having a difficult time logging into ‘Blackboard’ today to post the questions for chapter 10 of Autism’s False Prophets. Although I don’t like posting any required material here, I’d rather get it out there, so if you are in my pathology class, please spread the word to other students to check in here.

Before you start, check out this video mentioned towards the back of the chapter…

Autism’s False Prophets                                                                           Name:

Chapter 10 Questions

Science and Society

“For many parents, the advice given by heathcare professionals about vaccines is just one more opinion in a sea of opinions offered by the internet.”

-Offit, chapter 10

1. What is the problem with Dan Burton’s assessment of what he saw at the Stop Autism Now Conference?

2. How would you interpret the actions of policymakers at the CDC who ‘invariably give these vaccines to their own children and grandchildren’? If you have read Offit’s other book, Vaccinated, do you recall who vaccine maker, Maurice Hilleman, insisted were the first to receive the Hepatitis vaccine made from human blood?

3. What does Offit say is even more important than reporting the source of funding for scientific investigation on? Why is this so?

4. What is ‘the price’ of empowering parents to make medical decisions about their childrens’ healthcare?

5. How does the ‘Scientific Method’ differ from what people often do in their day-to-day lives? How is it similar?

6. Using the scientific method, data serves to _____________________________ the null hypothesis. What can it NOT do? Why not?

7. Why is it evolutionarily successful to make ‘the best connections’? What flaws in logic can this leave?

8. What quotation did Stephen Strauss, former director of NCCAM keep framed on his office wall? What is the meaning of this quotation?

9. How many people, since 1958, have died from poisoned Halloween candy? (http://www.snopes.com/horrors/poison/halloween.asp)

 

ABO+/- : Micro -or- Patho extra credit opportunity

Blood transfusions were first successfully accomplished by Richard Lower in the 1660s. However, like many scientists, he lucked into the right system by using dogs for his experiments. Although there are a number of canine blood types (Dog Erythrocyte Antigens, or DEAs),  only one type, DEA 1.1 leads to severe hemolytic reactions – and only upon secondary transfusions. Therefore, his experiments were very successful, however, they were not easily repeatable in humans for many years.

Lower’s account (as I’ve pilfered from his Wiki page because it was not cited) is as follows:

“…towards the end of February 1665 [I] selected one dog of medium size, opened its jugular vein, and drew off blood, until … its strength was nearly gone. Then, to make up for the great loss of this dog by the blood of a second, I introduced blood from the cervical artery of a fairly large mastiff, which had been fastened alongside the first, until this latter animal showed … it was overfilled … by the inflowing blood.” After he “sewed up the jugular veins,” the animal recovered “with no sign of discomfort or of displeasure.”

The ABO blood typing system has been used since its discovery by Karl Landsteiner in 1901 to allow for life-saving transfusions following accidents, surgery, or to treat other conditions. Classification into the four blood groups most common today, (A, B, AB, and O) was soon afterwards achieved by the efforts of Jan Jansky and his massively significant mustache. The additional understanding and detection of the Rhesus antigen in 1937 with Alexander Wiener, further improved success with blood transfers.

Given the following blood typing card, explain the reactions you are seeing and how this indicates blood type. Also, what is meant by ‘Anti-D’?

 

An ounce of prevention: A microbiology extra credit opportunity

Most flu shots are administered I.M. (intra muscularly), therefore, at a 90 degree angle relative to the skin.

Bob and Sally go to get their annual Flu vaccine at the public clinic. Every year, the two go together and neither have contracted Influenza since they began five years ago.

This time, while he was getting his shot, he says to his nurse, “These shots are great. I haven’t been infected with the Flu for years, despite at least some of my co-workers getting sick every year.”

His nurse finishes his injection and then says, “Well, you might have gotten infected, but you’ve didn’t get sick.”

“What do you mean? Isn’t that the same thing?”

“Actually,” says the nurse, ” it’s not.”

Explain what the nurse means by ‘infection’ and ‘getting sick’ being different things. Include, in your explanation, why it is that a vaccine might not prevent organisms from getting into your body and even into your cells, but that they can still fail to make you ill. What cells and molecules are involved in protecting you in this way?

 

UPenn Webinar – ‘Mickey’s Got Measles’

Poor Mickey

Today, I attended the webinar, Mickey’s Got Measles, through the Live Faculty Lecture Series offered at the University of Pennsylvania. Today’s lecture focussed on the epidemiology of Measles, Herd Immunity, and Trends in Immunization was presented by Alison Buttenheim. Given the recent outbreak of Measles that puts 2015 well ahead of year-to-date infection numbers, it was very timely and an excellent lecture. If you have 50 minutes, I highly recommend that you check it out here.

 

Immunology – Aquaman style

I almost split a seem the first time I saw this cartoon several years ago.

 

A Pointer

For my Microbiology students….

“I feel kinda sick”

As we finish up the year dividing out time between Immunology and Epidemiology, you may find it useful or just interesting to take a look at the online Epidemiology course offered at Coursera. It is a six-part course taught by Lorraine Alexander and Karin Yeatts of the University of North Carolina, Chapel Hill.

As all Coursera classes, this is 100% free unless you would like to receive a signed certificate of completion.

Enjoy.

 

It’s a Wide World

Have you ever asked yourself, “how is it that our immune system can fight off almost everything?”

It’s one of those things that is easily ignored.

 It works. That’s all I care about.

If that’s not a good enough answer, then read on…

The answer lies somewhere between biology and statistics. And I want to  start with an analogy.

Think of a website that makes you log in when you visit (Google’s gmail, for instance). You come up with a password when you join and then use it every time you log in. Some annoying websites make you cycle your passwords regularly for security purposes. (I’m not saying there’s anything wrong with that, but it can be taxing to those who don’t use a password storage program. – by the way, I use Dashlane  and love it)

But every time you use a password, it’s off the list – you can’t use it again. So after about three changes, you start to sweat because you think your head is filling with all those old passwords and you can’t remember the latest one any more. As an analogy for the immune system, imagine a simple program that creates random passwords for you and ensures that they’re not repeats of any that you’ve used before.

Your immune system has no idea what you’ll come up against in the world. All it can do is make a vast repertoire of immune cells with the hope that it will be sufficient to react to anything. For simplicity, let’s just consider how cells make antibodies. To do this, your cells have a way of randomizing the protein sequence responsible for making these proteins.

The problem with this system, if it’s just a random grab-bag, is that sometimes those antibodies might bind to your proteins causing big problems. So, after the random process that generates antibodies, there is a second, non-random selection process that eliminates any that bind to you.

In my analogy, imagine that a random password is generated (the antibody), but then it checks to be sure it’s not the same as a previous password (no self – reactivity).

If you do any programming you can imagine outlining your code:

(let’s say passwords are 4-digit numbers from 0-9)

 

1. generate a random number from 0001 – 9999
2. cycle through old passwords
   1. check that the new password is not equal to the old password.
   2. If it matches, discard that password and go back to step I
   3. If it does not match, cycle to next old password
   4. Repeat until all old passwords have been checked
   5. Present new password to user

Now that I look at it this way, it is very much like evolution by natural selection. Random process à non-random selection.

To illustrate how this works with the actual proteins, it’s best to go to good old Janeway:

The top two panels show something more like the actual structure of the antibody. The bottom panel shows a simplified cartoon, highlighting the variable region and the constant region of antibodies. Think of the constant region as the backbone of the molecule – it comes in a few models, but doesn’t change.

The variable region is where the antibody binds its target. This is the region that gets scrambled up so the antibody will have a unique binding region.

The variable region is actually composed of several parts (V, D and J) that get pieced together, one of each sort. This accounts for some variability, but could only result in a handful of different types.

In addition to this mix-and-match, the joining of segments is also imperfect. Recall that DNA is ‘read’ in three-base codons. Because of this, adding one extra base in joining the elements will result in a frame-shift that creates even greater diversity. It also admits the real possibility that the protein made will be entirely unstable and useless. To account for this, each cell is positively selected for only ones that make stable receptors. It has two shots* at making this work. Once for each of the two chromosomes (one from your mom, and one from your dad) bearing this gene. If it succeeds, it goes on developing**; if it fails, it commits cellular suicide: apoptosis.

Another figure adapted from Janeway

The result is a pre-immune repertoire of about 10¹² antibodies available to protect you from any nasty ‘bugs’ out there.

 

* There is data supporting additional receptor editing. 

**         Heavy Chain is rearranged and interrogated first, then Light Chain.