Volume 6, Issue No. 2

BIOTECHNOLOGY & YOU

a magazine of biotechnology applications in healthcare, agriculture, the environment, and industry

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Volume 6, Issue No. 2

Your World/Our World describes the application ofbiotechnology to problems facing our world. Wehope that you find it an interesting way to learnabout science and engineering.

Development by:The Pennsylvania Biotechnology Association,The PBA Education Committee, andSnavely Associates, Ltd.

Writing & Editing by:The Writing Company, Cathryn M. Delude andKenneth W. Mirvis, Ed.D.

Design by:Snavely Associates, Ltd.

Illustrations by:Patrick W. Britten

Diagnostics Issue Coordinator:Cynthia Gawron-Burke

Science Advisors:Warren C. Bogard, ConsultantBarbara Handelin, Ph.D., Handelin AssociatesLarry McClain, Centocor, Inc.

Publication Contributor:Gail B. C. Marsella, Branch Text Press

Special Thanks:The PBA is grateful to the members of the EducationCommittee for their contributions:

Keith Buckingham, Friends’ Central SchoolJohn C. Campbell, SmithKline BeechamCeil M. Ciociola, PRIME, Inc.Stephen R. Collins, JRH BioSciencesRoberta Cooks, The Franklin Institute Science MuseumJeff Davidson, Pennsylvania Biotechnology AssociationAlan Gardner, SmithKline BeechamCynthia Gawron-BurkeAnthony Green, Puresyn, Inc.Barbara Handelin, Handelin & AssociatesLinda C. Hendricks, SmithKline BeechamDaniel M. Keller, Keller BroadcastingCathy A. Kodroff, Howson & HowsonDustin Landis, Merck & Company, Inc.Barbara McHale, Gwynedd Mercy CollegeJune Rae Merwin, The West CompanyM. Kay OluwoleLois H. Peck, Philadelphia College ofPharmacy & ScienceJill M. Roberts Lewis, BioDiligence PartnersJean ScholzAlthea K. Talento, Merck Institute for ScienceEducationJohn Tedesco, Brandywine Consultants, Inc.Adam Yorke, SmithKline BeechamLaurence A. Weinberger, Esquire, Committee Chair

If you would like to make suggestions or commentsabout Your World/Our World, please contact us at:Internet: 73150.1623@compuserve.comor write to:Pennsylvania Biotechnology Association1524 W. College Avenue, Suite 206State College, PA 16801Copyright 1997, PBA. All rights reserved.

MedicalDetectives

46

Immunodiagnostics:Locks & Keys

Genetic Diagnostics: InterlockingDNA Molecules

8 The StrepThroat Control

10 Safeguarding theBlood Bank

Detecting Disease by its Disease

14 Ann Kirsch, Senior Medical Technologist

15 The Antibody Sandwich Test

On the Cover:A nurse from the 1950s would recognize some ways we diagnose disease, such as X-rays and throatsamples. But our new knowledge about molecular biology - how molecules fit together as a lock and key -has given us new diagnostic tools. One of these tools uses immune cells from mice to produce antibodies todetect a specific virus (upper left) or bacterium.

Cover Collage by: Cramer Studio

A C T I V I T Y

12P R O F I L E

The New Diagnostics

3

color of your mucus indicate infection?

These clues help doctors reach adiagnosis, which is an explanation ofwhat causes the disease symptoms. Adiagnostic test allows doctors togather the data needed to reach thatexplanation. Until recently, mostdiagnostic tests could only tell usabout the symptoms of the diseaserather than the real cause of thedisease. For example, in diagnosinglung cancer we could see tumors onX-rays but couldn’t define the geneticchanges that caused them. We couldfind the chemical “footprints” ofmany viral infections but could notidentify the specific virus.

Advances in science have given doctorspowerful new tools that help search forand interpret a whole new set ofbiological clues. These diagnostictools are made possible by a newunderstanding of how biologicalsystems work for both human bodiesand the disease-causing organisms.Scientists have learned that natureuses the interlocking shapes ofspecialized molecules to do some veryimportant work in the cells. Now theyare learning to use nature’s specialdesigns to diagnose and treat disease.

The following articles will show youtwo examples of nature’s specificity –in the immune system and in thegenetic “blueprint” for growth and allcellular functions – and how we canuse these systems in diagnostictesting. Later articles in this issuedemonstrate how these tests arehelping doctors become bettermedical detectives in their effort tofight disease. ■

Suppose you wake up with arunny nose. Do you have avirus or an allergy? Then you

get a sore throat. Is it from thevirus, the post-nasal drip of yourallergies, or a bacterial strepinfection? Now you are coughing.

Is it because of a viral cold? Asthmabrought on by allergies? Bacterial

lung infection?

Solving the mystery of yourillness is important, since itdetermines the treatmentyou receive. Allergies callfor medicines that

overcome the allergicreaction. Strep

throat requiresantibiotics tokill thebacteriabefore theycause moreseriousproblems.But if you

just havethe

commoncold, none of

these medicineswill help you and could make youworse in the long run.

To solve such a mystery, doctorswork as medical detectives, sorting

through clues to identify a likelysuspect. Is it hay fever season and doyou have a family history of allergies?Do you have a fever that usuallyaccompanies many bacterial and viralinfections but not allergies? Does the

MEDICALDETECTIVESMEDICALDETECTIVES

4

Why can you become immune (resistant) to one disease but not another?Why do some people have allergies, cancer, or heart disease? Why aresome people born with a genetic disease such as sickle cell anemia or

cystic fibrosis? Your own blood contains molecular traces that can answer suchquestions. But these molecules exist only in tiny amounts among numerousother molecules and cells. How do we find them? Naturehas given us a tool: the unique and interlocking shapesof certain molecules that fit together like matching puzzlepieces. Let’s take an imagi- nary trip inside the body to seehow these interlocking mol- ecules work and how we can usethem to test for diseases in the laboratory....

Immunodiagnostics:First Stop: The Immune SystemAs you travel through your bloodvessels, you see cells of different sizesand shapes. Some are your own bloodcells, and some are viruses, bacteria,and other particles. Zoom closer tonotice the bumps sticking out all overthe surface of each cell (as shownhere). These bumps act like labels forthe cell, helping your body divide cellsinto two camps: self (the body’s ownfriendly cells) and non-self (foreign,potentially dangerous cells andparticles).

Now you see a large molecule with aY-shaped pincher attaching itself to abump on a bacterium. Your ownimmune cells created this moleculespecifically to fit that bacterium’sbump. Your immune cells know thisbacterium is foreign because of the“non-self” shapes of its bumps. Yourspecialized molecule is called an

An antibody captures a foreign cell’s antigen.

5

You’ve dropped by the lab to see howscientists use the three-dimensional,interlocking shape of antibodies andantigens to detect a virus in yourblood. They use a process nick-named the “sandwich test.” Here’show it works:

Scientists figure out whichantibody the immune systemproduces in response to one of thevirus’s antigens. They make copiesof that antibody as described onpage 7. To start the sandwich,they anchor a layer of specificantibodies to the bottom slice of“bread.” To make the filling, theyspread a sample of your blood overthe antibody slice. If your bloodcontains the virus with antigensthat match that particular

antibody, the antibody’s pinchersgrab the virus and hold it to theslice. (None of the other sub-stances in your blood stick.)Everything that didn’t stick is“washed” away, leaving only theattached virus behind as the fillingof the sandwich.

But how do you “see” if any ofthese tiny viruses have stuck? Byputting on the top slice of bread.This top layer has antibodies thatwill also grab the virus by anantigen, but these antibodies havea signal that will change color, giveoff light, or show radioactivity.These signal antibodies will stick

L cks & Keys

Side Trip to the Laboratory: The Sandwich Test

1. Antibody fragments thatrecognize the virus are “anchored”to a plate (bottom slice).

Computer generated graphic: The surface ofthis RhinoFab virus cell shows “bumps” of proteinsthat act as antigens and trigger the production ofantibodies.

By attaching itself to the antigen, theantibody targets the bacterium fordestruction by other immune cells.Thus, the antibody/antigen match isone part of your complex immunesystem, which is designed to detecttiny amounts of foreign “invaders”with almost 100% accuracy – andthen mount defenses against them. ■

3. Signal antibodies that alsorecognize the virus attach to it(top slice).

to any antigens that were capturedin the “filling.” The sandwich is“washed” again, leaving behind thesignal antibodies that are stuck tothe antigens in the filling. Thus, asignal will only show if the virusantigens are present. If there is nosignal, the virus is not present, andthe doctor must look for otherexplanations for your symptoms.Because these tests are based onthe workings of the immunesystem, they are calledimmunodiagnostics. ▼

2. Test sample is spread over theantibodies. Antibodies capture thevirus by the antigen (filling).

antibody because it works “against”(anti) the foreign body. The bump iscalled the antigen because it isantibody generating.

Each type of cell has uniquely shapedantigens. Your immune cells can tellone shape from another, and theycreate antibodies with matchingshapes for each antigen that belongsto a foreign bacterium or virus. Thatmatch is so specific that one antibodyfits only one type of antigen, like alock fitting only one key.

6

Genetic Diagnostics:Next Stop: The DNA Inside theNucleusYour trip takes you inside a cell to itscommand center or nucleus, whereyou find the long, twisted moleculecalled DNA (DeoxyriboNucleic Acid).This “genetic information” moleculehas the shape of a twisted ladder, withtwo side rails “zipped” together.

A combination of four differentmolecules (A, T, C, and G) make up therungs of the ladder. These fourmolecules, called bases, act like lettersin a genetic alphabet. Their sequenceor order determines the meaning oftheir “sentences.” A DNA sentence is agene that carries the instructions tothe cell. The sequence for each gene isunique, and scientists are learning to“read” the sequences of the DNAlanguage to identify genes anddiscover what they do. So far, theyhave found a number of genes thatdirectly or indirectly cause diseases.

When a cell divides, it makes an exactcopy of the entire DNA sequence. Thisexactness ensures that the new cellkeeps the unique sequences of its

genes. This exactcopying

dependson

the matching shape of paired mol-ecules. Each of the four bases, A, T, C,and G, has a unique shape. Further-more, their shapes create matchingpairs that fit into each other like 3-Dpuzzle pieces. A and T fit together, andso do C and G. These matchingmolecules are called complementarybase pairs. On a double strand of DNA,A is always opposite T and C is alwaysopposite G (as shown on this page). Infact, the reason the two DNA strandsare bound together is because of theprecise and strong attraction theseinterlocking shapes have for eachother. The bonds created by theseinterlocking shapes form the “rungs”of the doubled-sided DNA “ladder.”

In the Laboratory: Making aDNA ProbeMany health problems result fromslight variations in the sequence ofone or more genes. These genetic

differencescould be

inherited,

The bases along one rail of the twisted DNAladder line up with the matching shapes of baseson the opposite rail.

or the genes could be damaged beforeor after birth. As scientists identitygenetic footprints for different medicalconditions, they can make geneticdiagnostic tests. These tests depend onthe attraction that the interlockingDNA molecules have for each other.This attraction allows scientists to“fish” or probe for certain forms ofgenes. DNA probes can find the slightvariations in genetic sequences thatare responsible for a medical conditionin a particular patient. Here’s how aprobe works:

First, scientists identify a uniquesequence in a gene associated with thedisease. They create a single strand ofDNA for thatsequenceto bethe

DNA Double Helix

Complementary Base Pairs

7

cancer cells

InterlockingDNA Molecules

probe, and they make many copies ofthis probe. They attach a signal to theprobe, so it will glow, change color, orgive off detectable radioactivity(similar to the top slice of the immu-nological “sandwich” test).

Next, doctors take a sample of blood orother tissue from a patient and separateout the DNA. The double strands ofDNA are then “unzipped” and stuck to aspecial paper. This paper is put in asolution with copies of the probe. Thebases in the single-strands of sampleDNA attract the complementary basesin the single-stranded probe. If theprobe finds its exact puzzle match inthe DNA sample, the probe sticks to it

and the two strands“zip” together (asshown below). Thesolution is then“washed” off,leaving behind onlythe probes that have

attached to their matchingsequence. If the probe’s signalshows, the patient’s DNA hasthe genetic sequence inquestion. On the other hand, ifthe patient’s DNA does not havethat genetic sequence, noprobes will stick and thesample gives off no signal. ■

Monoclonal Antibodies

ImmuneCells

Virus

1. Injectvirus

2. Extractimmunecells

3. Fused cells:Immortalantibodyfactories

4. Grow clones offused cells

5. Each clone pro-duces antibodies

6. Test antibodies forreaction to virus

CancerCellsCancerCells

A DNA probe sticks to a strand of DNA if and onlyif each of its bases lines up with their matching(complementary) bases on the opposite strand.

Fused cells

virusScientists make the large number

of antibodies needed forimmunodiagnostic tests in tiny

factories - cells! In one method, they caninject a mouse with a virus (1) so itsimmune cells make antibodies againstthe virus. They extract these immunecells from the mouse (2), but they don’tyet know which of these cells make theright antibody. They fuse all the immunecells with certain cancer cells (3) thatdivide continuously. Immune cells (likeother normal cells) only divide a fewtimes and then die. The fused cell isan “immortal” antibody factory that cando what neither cell can do alone.Scientists allow each fused cell to growinto a colony of identical clones (4).Each clone churns out thousands ofidentical monoclonal antibodies (5) -so called because they are fromclones of one (“mono”) cell. Finally,scientists test each colony to see whichproduce the antibodies that bind tothe virus’s antigens (6). Then theycollect these antibodies forimmunodiagnostic tests.▼

8

Has this ever happened toyou? Your flashlight is getting dim, butyou just put new batteries in it. How

can you tell if the new batteries are theproblem or if something else is wrong? You

could replace the flashlightbatteries with ones you know aregood or put the questionablebatteries in an appliance you knowworks properly. Better, you coulduse the “test strip” provided withmany batteries. The test stripmeasures the power of thebattery against a standard ofpower. If the batteries test weak,you know to replace them. Ifthey test strong, you must lookfor another explanation foryour dimming flashlight.

The battery test strip actslike a control that allows you

to make conclusions about the state of thebatteries and then take the right action. In otherwords, the control allows you to verify that your“diagnosis” of weak batteries is truly the cause ofthe “sick” flashlight before you try to “treat” theproblem with different batteries.

In much the same way, doctors and scientists needcontrols to make sure their diagnostic tests work asthey expect. You may already be familiar with onevery common diagnostic test that has a built-incontrol.

THIN

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ABOUT THIS!!...How is the controlwindow in the rapidstrep test like a batterytest strip.

ThroatControl

Photo by: Bruce CramerDigital Editing by: David Hinnergardt

9

StrepBacteriaPresent

Side interior view of test strip

Top view

StrepBacteriaNOT Present

ControlWindow

TestWindow

PositiveTestResult

NegativeTestResult

ControlWindow

TestWindow

The Rapid Strep TestWelcome to the doctor’s office. Yoursore throat that began on page 3 hasgotten worse, and the nurse justswabbed your throat to see if youhave strep throat.

Traditionally, this sample is sent to thelab to be grown in a “culture” (anutrient-rich dish) for 24 to 48 hours.In that time, any strep bacteria in thesample will grow enough to be visible.In the meantime, you continue tosuffer – and your doctor faces adilemma: If you do indeed have strep,you need quick treatment withantibiotics, because the bacteria cancause serious health conditions,including rheumatic fever and heartproblems. Still, you should not take theantibiotics that kill the strep bacteria ifyou don’t have it. The antibiotics willnot help you, and taking them can helpother bacteria in your body becomeresistant to the antibiotic so themedicine will not be as effective whenyou need it in the future.

Because this serious dilemma is socommon, scientists developed the“rapid strep test” (shown to the right).Because this immune reactionhappens quickly, the results areavailable within 10 minutes. If the testshows you do have strep throat,antibiotic treatments will soon put youout of your misery. If the test showsyou do not have it, you’re probablysuffering from a virus and need a lot offluids, bed rest, and TLC. You canlearn more about the differencesbetween bacterial and viral diseases,and how these differences affectdiagnostics in the next article. ■

STREP STEPS

What if there was no signal ineither the Test Window or theControl Window? Could you tellwhether or not you had strepthroat?

?WhAt if

The rapid strep test strip below contains a place for putting the test solution(1) which “wicks” or flows through the strip. Anti-strep antibodies with asignal are anchored to a test area (2). A control area (3) has a chemical thatchanges color when the solution reaches it.

A swab with throat sample is placed in a solution to get the bacteria off.When antibodies in the test area capture the strep bacteria, their signalshows in the Test Window. When the solution reaches the end, the chemicalsproduce a signal in the Control Window.

When the test solution does not contain strep bacteria, nothing binds to theantibodies and no signal appears in the Test Window. The solution

triggers a color change when it reaches the chemicals underthe Control Window, indicating the test is complete.

1 2 3

10

herpes that causes cold sores. Peoplewith this virus can go for months oryears without symptoms while thevirus hides out in their nerve cells.Suddenly something triggers it intoaction, and it uses the host cells tomake copies of itself. When these newviruses burst out of the cells, a coldsore appears.

A similar hide-and-wait processhappens with HIV, the virus that causesAIDS, and hepatitis, a liver diseasecaused by a virus. Because of their longlatency period, people can carry aroundthese viruses without knowing they aresick – and they could donate bloodwithout knowing it is infected. Anyonewho receives that infected blood alsoreceives a deadly disease. That is why itis so important to have a reliablescreening test.

Immunodiagnotics To TheRescueAlthough viruses can evade traditionallaboratory diagnostics, they cannotcompletely fool your amazing immune

Safeguarding theBlood Bank

When tennis great ArthurAshe won the 1968 U.S.Open and later the

Wimbledon title, he did more thandefeat his rivals. He also defeated long-standing racial barriers by becomingthe first black man to play on the U.S.Davis Cup team and then playprofessional tennis. In 1992, hesaddened the public by announcinghe had AIDS as a result of contractingthe HIV virus from a blood transfusionduring heart surgery more than 10years before. In 1993 he died, at theage of 49.

ganisms is essential, since they aredifficult or impossible to cure.

The Truth About Bacteria andVirusesProtecting the blood supply frombacteria is relatively easy. First of all,bacteria are independent, one-celledorganisms that multiply in thebloodstream, mucus, organs, andother body tissues. When blood andtissue samples are taken, thebacteria are large enough to be seenunder a microscope. They are easy togrow in a lab culture, and can beattacked by antibiotics that seek outthe free-floating organism anddisrupt its life cycle.

A virus, on the other hand, is a tiny“incomplete” organism – a parasite –and hard to see. (See illustrationbelow.) A virus does not have all themachinery of a living cell, but livesinside the “host” cell it infects. Ithijacks the host cell’s machinery to doits own work, including reproduction.

Since a virus lives inside a host cell, it ishard to detect and it is protected fromthe attacks of both the immunesystem’s antibodies and medicalantibiotics. Furthermore, because itonly reproduces inside its host, it won’tgrow in most laboratory cultures.Therefore, a viral disease can evade bothdetection and treatment.

To make matters worse, many virusescan live within the host cell for a longtime without damaging it andcausing symptoms of disease. Thislong latency period (the time it just“hangs out” in the cell) makes itimpossible to tell if a person isinfected. Common viruses with longlatency periods include the kind of

The bacterium on the left lives independently as acomplete organism. The smaller virus on the rightis a parasite that depends on a host cell for manyfunctions. A virus is not much more than a smallgenome (set of DNA) inside a protein shell.

THIN

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ABOUT THIS!!...Drugstores sell severaldo-it-yourself diagnostickits, including one forHIV, the virus thatcauses AIDS. What are

some good things aboutself-test kits? What are

some potential problems?Why do the kits always recom-mend talking over test resultswith a doctor, whatever theresult?

Blood Banks: Risk or Rescue?Arthur Ashe was one of thousandswho contracted AIDS from the bloodsupply before an accurate and widely-available screening test was devel-oped. Today, every pint of blood in thenation’s blood bank must pass aninspection that includes a test for theHIV virus and other deadly virusesand bacteria. These tests use theimmunodiagnostic “antibodysandwich” technique as discussed onpage 7. Screening for these microor-

11

Screen TestsCan you think of anything besides blood that comes inlarge volumes and needs to be screened for disease? Youdrink several glasses of two such things each day: milkand water. Milk can carry low concentrations of bacteriafrom the cow or the processing. Likewise, water containsmany microbes and some of these can survive chlorina-tion. Screening the huge amounts of milk and watersupplied to consumers has become much easier with asystem of multiple antibodies that captures tinyamounts of disease-causing bugs as the liquid passesthrough. For example, the current way to test for thewater-borne parasite cryptosporidium (which means“mystery spore” in Latin) takes several days. Scientistsare developing both immunodiagnostic and genetictests that will take only hours. As the chart on the backcover shows, the new diagnostics are at work in manyfields outside medicine.▼

A deposit in the bloodbank: Each year,hospitals use millions ofpints of blood.This blood savesthe lives of surgerypatients, accidentvictims, andpeople withdiseases.Most of thisblood comes from donations fromordinary people during blood drives.The blood is then screened for diseaseand stored for later use.

Screening Fluids for Microbial Contamination: Large quantities ofmilk are sent through a capture chamber. The beads in the chamberare removed and tested to determine if disease-causing microbes arepresent and if the milk is safe for drinking.

Purd

ue U

nive

rsit

y

Uta

h St

ate

Uni

vers

ity

...Blood bank tests arehighly sensitive, sothey produce some“false positives” (the

results show disease ispresent when it is not)

but no “false negatives” (theresults show there is no diseasewhen there really is). Why is thislevel of sensitivity important forpublic safety?

THIN

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ABOUT THIS!!system with its fantastic ability torecognize tell-tale antigens on aforeign cell. Your immune cells get aquick glimpse of the free-swimmingvirus before it slinks inside your cells.That glimpse can give them thechance to make antibodies against it.These antibodies do not have anopportunity to kill the virus while ithides in your cells, but they givescientists the opportunity to makeimmune-based tests that can screenthe blood supply. Scientists makecopies of these antibodies to use in“sandwich tests.” If these tests findantibodies to the virus in a bloodsample, then the blood probablycontains the virus, too. In that case,that blood donation is discarded so itwill not infect other people.

In such a way, immunodiagnostics hassafeguarded the blood bank fromdeadly viruses, so the tragedy of ArthurAshe and others like him will not berepeated. This knowledge should helpyou rest easier, since we never knowwhen we might need rescue by a bloodtransfusion. ■

Close up image of virus

12

Prader Willi Syndrome is an inherited geneticdisease caused when a large section of aChromosome 15 is deleted. A probe representingthe deleted section attaches to the normalChromosome 15 (shows as a bright spot on thephotograph) but not to the abnormal one.

VYSI

S, In

c.

Whether it’s a gene forbaldness or cancer, thediscovery of a gene associ-

ated with a human condition gets a lotof fanfare. People always hope thediscovery will lead to a cure ortreatment. Behind the fanfare is thedouble-edged sword of diagnostics.Genetic diagnostics allows you to findout if you carry the form of a gene

Predisposing Cancer GenesThe headlines about genetic discover-ies often make it seem as if you couldbe “fated” to get a certain cancer inyour future. In reality, geneticdiagnostic tests can only tell if youare “predisposed” to it; that is, if youhave a greater chance of developingthat cancer than other people withother forms of the gene.

associated with a disease. If knowingcan help prevent the disease (such asby changing diet or exercise habits orby catching a tumor early enough)then it’s a good thing. But if there isno prevention or treatment, manypeople would rather not know. Theymay not want to live with the anxiety,and/or they may fear discriminationfrom health and life insurancecompanies, employees, or otherpeople. The following examples showboth sides of the diagnostic sword.

Two chromosomes ...break apart... ...swap pieces...in cell...

Colon Cancer Gene Discovered

How a Damaged Cell Becomes Cancerous

13

Deadly Ebola Outbreak in Kikwit

For example, a gene important tobreast cells has a form that is connectedwith a small percentage (only 5%) ofbreast cancers. Yet, a woman with thatform of the gene has a very high chanceof getting breast cancer (50% by theage of 40 and a 80-90% by the age of70). When a female has many relativeswho have had early breast cancer,should she be tested to see if she hasthis gene? The answer would be easier ifthere were a clear way to prevent thecancer, but there is not.

Genetic diagnostics for predisposinggenes depends on the fact that each ofyour cells carries an identical copy ofthe entire set of genes that youinherited from your parents. Bytesting the genes in any one cell, wecan theoretically tell if you inherited adisease form of a gene. We could eventest a new born baby for a disease thatcould develop in old age.

Cancers Caused by Cell DamageAlthough you start out with identicalgenes in all your cells, as you age andgrow some genes undergo changes.Radiation from the sun and X-rays,chemicals and infections can damagethe DNA in some cells. A damaged genesometimes leads to cancer. A cancer cellstops doing its usual job and grows outof control, creating a tumor or mass ofbad cells. To find that cancer, geneticdiagnostics must analyze cells from thetissue in question, not just any cell inyour body.

We become violently ill or die, andthe disease spreads quickly andwidely.

To control an emerging disease,scientists first must know whatkind of virus causes it. However,studying the virus’ antigen or ourantibody response can take months.

Luckily, genetic diagnostics givesscientists a much quicker way tostudy the virus by going straight tosequencing the virus’s genome(complete DNA). Scientists useDNA Probes and computers to“read out” the order of the A.C.T,Gmolecules along the strand of DNA.(See pages 6 and 7.) They comparethis sequence to those of otherviruses whose sequences are filed inhuge data bases. This analysesshows what the unknown virus isrelated to and how it works.▼

An outbreak of the deadly Ebolavirus in this tiny African commu-nity caused worldwide panic. Thedoctors and nurses who operatedon the same patient becameterribly ill. The illness spreadquickly and most victims died.Medical researchers rushed toZaire, identified the Ebola virusas the cause, and controlled theoutbreak.

This crisis was one of manyrecent outbreaks of previouslyunknown infectious diseases.These new emerging diseaseshave broken out of their normalparasitic life cycles with a certainspecies and have infected humanbeings. The viruses may causeonly mild harm to their normalhosts. Because they are new tous, we do not have naturalantibodies to help us resist them.

and rejoin in thewrong way.

Genetic diagnosticsraises difficultquestions: Do youhave a right toknow (or not to

know) your geneticmakeup? Can your

right to privacy keepother people from finding outsensitive information about yourgenes? Does testing babies andchildren conflict with theirfreedom of choice, since theycannot give “informed consent”to be tested?

THIN

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ABOUT THIS!!

The Story of an Emerging Disease - Kikwit, Zaire, 1995

For example, when a type of immunecell in your blood called a lympho-cyte is damaged, a section of DNAresponsible for producing antibodiesbreaks off and inserts itself in themiddle of a DNA section thatcontrols the cell’s life span. Insteadof producing helpful antibodies, thecell divides out of control, causingthe cancer lymphoma. To detect thiscancer, scientists create a DNA probefor the sequence with the wrongcombination. This probe recognizesonly cancerous blood cells, notnormal ones. Such testing can findcancer in the early stage when it isstill treatable. Thus, while somegenetic diagnostics can lead to life-wrenching decisions, others can leadto life-saving treatment. ■

14

It was an ER nightmare. Theambulance rushed theautomobile accident

victim to theemergency room,where doctors andnurses workedfrantically to savehis life. Heneeded manyblood transfu-sions. The ERcalled the nearbyMiller MemorialBlood Bank formore blood.

One of Ann’s jobs at the Miller Memorial Blood Bank is to be sure patientsreceive the right kind of blood – and to be sure it is disease-free. (See chart.)Complicated blood-matching tests make sure that donated blood will be compat-ible with a patient’s blood type. The screening tests determine the “blood type,”such as A, B, AB and O negative or positive, etc., and analyze other antibodies inan individual’s blood. If a person receives the wrong type of blood, it can bedisastrous. To do these tests, Ann uses a variety of machines and instruments,and performs control tests to confirm the accuracy. Her work includes thetroubleshooting and problem solving required when machines act up or testresults don’t make sense.

Ann’s problem was that the accident victim needed more blood platelets (a fragilpart of the blood used in transfusions) than her blood bank had processed.Without more platelets, the man would die. Ann and her team worked throughthe night processing blood that had been been donated earlier that day for thepatient. They knew it was a life and death matter, but they had to keep calm andfocused to avoid a potentially deadly mistake.

Even without the crisis atmosphere, Ann knows her work is important. “I alwaysknow that I’m helping someone, and it’s gratifying to know that there is a needfor what I do,” she says. “I’m proud of our facility and of how conscientous mycoworkers are. In this job, as in any health care profession, you need compas-sion in addition to scientific knowledge.”

As a medical technologist, Ann merges the profession of nurse and medicalresearcher. Hers is one of many new and interesting careers that use the latesttools of biotechnology. Ann entered this field after earning her bachelor’s degreein chemistry from Cabrini College. She went to a job fair looking for a career thatwould allow her to work in her field without going to graduate school first. Afterlearning about medical technology, she earned a certificate in the field from theSacred Heart Hospital School of Medical Technology in Allentown, PA. ■

Ann Kirsch uses the new tools of medical diagnostics in her career as SeniorMedical Technologist at The Miller Memorial Blood Bank.

Tests Performed on DonatedBlood at Miller Memorial

HIV antigen and HIVantibody(the virus that causes AIDS)

Hepatitis B and C(viruses that cause a liverdisease)

Corzyme(part of a Hepatitis test)

ALT(a liver enzyme that helpsinterpret the results of thehepatitis tests)

Human LymphotropicVirus(causes the cancer leukemia)

Syphilis(a sexually-transmitteddisease)

ABO and RH(blood typing)

Antibody screen(part of compatabilityblood typing)

Profile of Ann KirshSenior MedicalTechnologist

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15

For this activity, you will conduct animmunodiagnostic test using a modelof the “sandwich” method. Of course,this model will not look like a peanutbutter sandwich, but you will seethree levels where antigens arecaptured for detection. Work in smallgroups using the following materials.

Materials• Bottom of egg carton

• 4 Eggs (plastic, wooden, or hardboiled – not raw!) that fit into thecarton’s cups

• Cubes, balls, and other objects ofsimilar size to the eggs

• Modeling clay

• Scissors

• Brightly colored marker (one color)

• Cardboard box

Preparation of Antibodies1) Cut the bottom of the egg carton

in half, so each section has tworows of three cups.

2) Leave one section as is (the“bottom slice antibodies”).

3) Cut the other section into sixindividual cups (“top slice antibod-ies”).

4) Turn the separate cups upsidedown and color them with yourmarker (the signal).

5) Set these separate cups aside.

Preparation of Antigens1) Leave two eggs as they are.

2) Using the modeling clay, cover theother two eggs or make bumpsso they do not fit in the egg cartoncups.

3) Mix the four eggs with cubes, balls,and other objects in a box. Thismixture represents a blood samplewith different kinds of cells.

IACTIVITY:ACTIVITY:The Antibody Sandwich Test

Procedure1) Place the half egg carton (bottom

slice of antibodies) on your deskor table.

2) “Expose” this carton to your“sample” by spreading the mixtureof objects on your desk. See whichof the objects fit precisely into theegg cups. The shape of the egg cupmust fit exactly to the contour ofthe object.

3) The egg carton captures any cellswith antigens that match the egg cupantibodies. If the antigens are largeror a different shape, they do not fit.

4) “Wash” the sample by removing theobjects that do not fit in the eggcups. The eggs (antigens) thatremain in the carton represent thesandwich “filling.”

5) “Expose” the eggs to the separate eggcup antibodies. These cups will fit ontop of any egg antigen that has beencaptured by the bottom egg carton’santibodies.

6) “Wash” the egg carton again,removing any separate egg cupantibodies that did not find an eggantigen. There should beseparate egg cups placedupside down on theeggs in the carton.

7) Notice the“signal” given offby the colored spoton top layer ofantibodies. This signalallows you to detect thepresence of eggs in thecarton! What is your diagnosisfor this blood sample?

Discussion1) In a real test, the top of the

“filling” antigen would not look sosimilar to the bottom, so the toplayer of antibodies would have adifferent shape.

2) As in this test, antibodies are veryspecific about which antigens theycapture. For instance, althoughan egg covered with modeling clayis very similar to a plain egg, itshould not have been similarenough to fit in the antibody.

3) A variation of the sandwich testtargets an antibody rather than anantigen for the filling. Such testswork because some antibodiestarget a different antibody insteadof an antigen. ■

15

16

Dear Students:

Biotechnology and the rapid advances of science are in thenews - and we expect this to continue over the course of yourlife. This issue of Your World/Our World is designed to allow youto explore how biotechnology will influence your life and yourworld by delving into the science of diagnostics. We hope you find itinteresting and useful.

Further, we encourage you to continue studying science and mathso you can help make tomorrow’s scientific discoveries or helpexplain them to your friends and family. You will find amazingdiscoveries - and we hope that you will want to understand them at abasic and applied level.

Sincerely,

Janice T. BourqueExecutive Director, Massachusetts Biotechnology Council

Sponsor

The Massachusetts Biotechnology Council

Directors of the Massachusetts Biotechnolog Council

Mark SkaletskyGelTex Pharmacueticals, Inc.

Richard F. PopsAlkermes, Inc.

David J. McLachlanGenzyme Corp.

Sherri C. ObergAcusphere, Inc.

Michael J. AstrueBiogen, Inc.

Joseph DonovanMassachusettsOffice of Business Development

Patrick GageGenetics Institute, Inc.

Malcolm MorvillePhytera, Inc.

Christopher K. MirabelliLeukoSite, Inc.

Alison Taunton-RigbyAquila Biopharmaceuticals, Inc.

Una RyanT Cell Sciences, Inc.

Hisham SamraSerono Laboratories

Terry McGuirePolaris Venture Partners

Cynthia FisherViacord, Inc.

Spiros JamasAlpha-Beta Technology, Inc.

Chris ColecchiMassachusetts General Hospital

Diagnostics atWork

The new diagnostics are used inmany fields. Here are a fewexamples:

Water QualityDetect the tiny, infectiouscryptosporidium parasite indrinking water.

Food SafetyDetect contaminants thatcause bacterial infections inmeat and milk, as well asunsafe levels of antibiotics,pesticides,and otherchemicals.

AgricultureDetect disease anddiagnosinggenetic health for breedinganimals and crops.

Environmental HealthIdentify and locate pollutantsof soil, air, and water.

MilitaryIdentify use of biologicalweapons (chemicals andmicroorganisms).

Health and MedicineImmunodiagnostic testsinclude:*StrepRubella (measles)TuberculosisPregnacyHIV (causes AIDS)Ulcer bacteria (Helicobacter

pylori)Endrocine (glandular) tests for

thyroidVitamin and mineral

metabolismFertilityAntibody markers for some

cancersDrug screening in urine

samplesBlood bank screening (see

chart on page 14)

*Some of these tests can be given in thedoctor’s office, while others must be sent to aclinical laboratory. Some are available inboth formats.