Vaccines, Antiviral Drugs and Gene Therapy

1. ANTIVIRAL DRUGS
VACCINES
GENE THERAPY
0

2. OVERVIEW
• Antiviral drugs- definition, description, history, important
antiviral drugs, flu antiviral therapy, AIDS antiviral drugs
• Vaccines-definition, history, current status, important
vaccines, immunological responses
• Gene therapy- definition, history, mode of action, current
status
i

3. ANTIVIRAL DRUGS
1
MOMINA SHAHID

4. • Vaccines have provided considerable success in
preventing viral disease.
• But, they have modest or often no therapeutic
effect for individuals who already are infected.
• Consequently, our second arm of antiviral
defense has been the development and use of
antiviral drugs.
• They can stop an infection once it has started.
2

5. However, despite almost 50 years of
research, our arsenal of antiviral drugs
remains dangerously small.
Only about 30 antiviral drugs are
available on the US market.
Most against HIV and herpes viruses.
3

6. WHY WE HAVE SO FEW
ANTIVIRAL DRUGS?
1. Compounds interfering with virus growth can
adversely affect the host cell.
• Side effects are common
• Every step in viral life cycle engages host functions
4

7. 2. Many medically important viruses are dangerous, can't
be tested in model systems, or can't be propagated.
• Difficult or impossible to grow in the
laboratory (hepatitis B and C, papilloma viruses)
• Have no available animal model of human disease
(smallpox virus, HIV ,measles virus)
• Will kill investigators who aren't careful (Ebola virus ,
Lassa fever virus ,Small pox virus)
5

8. 3. Antiviral drug must block viral replication
completely.
• Partial inhibition is not acceptable for an antiviral
drug. If a drug does not block virus replication
completely, resistant viruses will emerge.
6

9. 4. Antiviral drug discovery is time consuming
and expensive.
7

10. HISTORICAL PERSPECTIVE
• The first modest search for antiviral drugs occurred in
the early 1950’s.
• Chemists looked at derivatives of the sulfonamide
antibiotics.
• In the 1960’s and 1970’s, drug companies launched
huge “blind-screening” programs to find chemicals
with antiviral activity.
8

11. BLIND SCREENING
• Random chemicals and natural product mixtures tested for
ability to block replication of a variety of viruses in cell
culture systems.
• The mechanism of how these compounds inhibit the virus
is not given any importance.
• Despite considerable efforts, very little success was
achieved.
• Amantadine was discovered which is effective for
treatment of influenza A virus infections. 9

12. DISCOVERING ANTIVIRAL
COMPOUNDS TODAY
• New technology and recombinant DNA
technology have made targeted discovery
possible.
• Blind screening procedures have lost
popularity among pharmaceutical companies.
10

13. ANTIVIRAL AGENTS
• Most antiviral drugs are antimetabolites.
• Antimetabolites resemble structures of nitrogenous bases
(purine and pyrimidine).
• Antimetabolites are prodrugs that are activated by host cell
enzymes or viral enzymes (mostly kinases).
• Most of the antiviral drugs have ‘VIR’ hidden somewhere in
their names.
An antimetabolite is a chemical that inhibits the use of a metabolite,
which is another chemical that is part of normal metabolism. 11

14. STEPS FOR VIRAL
REPLICATION
① Adsorption and penetration into host cell
② Uncoating of viral nucleic acid
③ Synthesis of regulatory proteins
④ Synthesis of RNA or DNA
⑤ Synthesis of structural proteins
⑥ Assembly of viral particles
⑦ Release from host cell
12

15. MECHANISM OF ACTION AND
ASSOCIATED DRUG
MECHANISM OF ACTION EFFECTIVE DRUG
Adsorption Enfuvirtide
Penetration Alpha-Interferon
Uncoating Amantadine
Early protein synthesis No drug
Nucleic acid synthesis Acyclovir
Late protein synthesis Ritonavir-Protease inhibitor
Packaging and assembly No drug
Viral release Zanamivir-Neuraminidase
inhibitor
1
3

16. ENFUVIRTIDE
• Enfuvirtide is used along with other medications to treat
human immunodeficiency virus (HIV) infection.
• Enfuvirtide is in a class of medications called HIV entry
inhibitors.
• It works by decreasing the amount of HIV in the blood.
Although enfuvirtide does not cure HIV, it may decrease
chance of developing acquired immunodeficiency
syndrome (AIDS) and HIV-related illnesses such as serious
infections or cancer.
• Taking these medications along with practicing safer sex
and making other life-style changes may decrease the risk
of transmitting the HIV virus to other people. 14

17. ALPHA-INTERFERON
• Cells that have been infected with virus produce interferon,
which sends a signal to other cells of the body to resist viral
growth.
• When first discovered in 1957, interferon was thought to be
a single substance, but since then several types have been
discovered, each produced by a different type of cell.
• Alpha interferon is produced by white blood cells other
than lymphocytes.
• All interferons inhibit viral replication.
15

18. AMANTADINE
• Amantadine is a drug that has U.S. Food and Drug
Administration approval for use both as an antiviral and
an antiparkinsonian drug.
• The mechanism of Amantadine's antiviral activity involves
interference with a viral protein M2 (an ion
channel), which is required for the viral particle to become
"uncoated" once taken inside a cell by endocytosis.
Influenza B does not possess M2 channels, and thus the
drug is ineffective towards all Influenza B strains.
• Amantadine has been associated with several central
nervous system side effects. CNS side effects include
nervousness, anxiety, agitation, insomnia and difficulty in
concentrating. 1
6

19. VETERINARY MISUSE
• In 2005, Chinese poultry farmers were reported to have
used amantadine to protect birds against avian influenza.
• According to international livestock regulations,
amantadine is approved only for use in humans.
• Chickens in China have received an estimated 2.6 billion
doses of amantadine.
• Avian flu (H5N1) strains in China and southeast Asia are
now resistant to amantadine, although strains circulating
elsewhere still seem to be sensitive.
• If amantadine-resistant strains of the virus spread, the
drugs of choice in an avian flu outbreak will probably be
restricted to the scarcer and costlier zanamivir, which work
by a differentmechanism.
17

20. ACYCLOVIR
• Acyclovir is a guanosine analogue antiviral drug.
• It is one of the most commonly used antiviral drugs.
• It is used for the treatment of herpes simplex virus infections,
as well as in the treatment of varicella zoster (chickenpox)
• Acyclovir is converted by host cell kinases to acyclovir
triphosphate that competitively inhibits and inactivates DNA
polymerases and inhibit nucleic acid synthesis.
• Overdose symptoms may include seizure (convulsions),
hallucinations, and urinating less than usual or not at all.
18

21. RITOVIR
• Ritovir is prescribed for HIV (Human Immunodeficiency
Virus) infection either alone or combined with other
antiviral agents.
• It is a protease inhibitor.
• It cleaves polyproteins.
• Prevents late protein synthesis by inhibiting post
translation modifications as segments of polyproteins after
cleaved make a capsid.
• Block protease to cleave polyprotein.
• Useful in HIV because it produces a polyprotein which is
cleaved later. HIV includes a protease, and so considerable
research has been performed to find "protease inhibitors"
to attack HIV at that phase of its life cycle.
• No use in influenza.
19

22. ZANAMIVIR
• Zanamivir is a neuraminidase inhibitor used in the
treatment of influenza caused by influenza A and B
viruses.
• It was the first neuraminidase inhibitor commercially
developed.
• Zanamivir works by binding to the active site of the
neuraminidase protein, rendering the influenza virus
unable to escape its host cell and infect others.
• It is also an inhibitor of influenza virus replication in
vitro and in vivo.
• In clinical trials, zanamivir was found to reduce the time-to-
symptom resolution by 1.5 days if therapy was started
within 48 hours of the onset of symptoms.
20

23. ANTIVIRAL THERAPY FOR FLU
21

24. INFLUENZA A STRAIN STRUCTURE
2
2

25. INFLUENZA B STRAIN STRUCTURE
23

26. • Influenza A and B viruses carry two surface glycoproteins,
the haemagglutinin (HA) and the neuraminidase (NA).
Both proteins have been found to recognize the same host
cell molecule, sialic acid. The Hemagglutinin protein
facilitates viral attachment while neuraminidase is involved
in viral release.
• Only Influenza A has M2 protein.
• Amantadine and Rimantadine block M2 protein.
• Both of these drugs are ineffective against influenza B
strain.
• Zanamivir – a neuraminidase inhibitor is effective for both
influenza A and B strain but it is costly compared to
amantadine and rimantadine.
• Start medicines within 2 days
• Treatment time is 5 days
24

27. HIGH RISK GROUP
• < 2 years
• >65 years
• Pregnant women
• Chronic diseases
• Severe diseases
• Hospitalized
25

28. HIV LIFE CYCLE
26

29. INITIAL THERAPY
• AZT is the first U.S. government-approved treatment for HIV,
• AZT inhibits the enzyme (reverse transcriptase) that HIV uses to
synthesize DNA, and thus prevents viral DNA from forming.
• It slows HIV replication in patients, but does not stop it entirely.
• HIV may become AZT-resistant over time, and therefore AZT is
now usually used in conjunction with other anti-HIV drugs in
the combination therapy called highly active antiretroviral
therapy (HAART).
• Early long-term higher-dose therapy with AZT was initially
associated with side effects including
anemia, neutropenia, hepatotoxicity, cardiomyopathy,
and myopathy. All of these conditions were generally found to be
reversible upon reduction of AZT dosages
• When first prescribed, AZT was given in high doses, which
commonly caused severe side-effects. Recommended doses are
now much lower, and as a result, side-effects have lessened
27

30. CLASSES OF ANTI-HIV DRUGS
• Nucleoside+ Nucleotide Reverse Transcriptase Inhibitor
• Non Nucleoside Reverse Transcriptase Inhibitor
• Protease Inhibitor
• Fusion and attachment Inhibitor
• Integrase Inhibitor
28

31. 29

32. References
http://en.wikipedia.org/wiki/Highly_active_antiretroviral_t
herapy
http://www.aidsmap.com/Side-effects/page/1730907/
http://www.nlm.nih.gov/medlineplus/druginfo/meds/a6820
64.html
http://www.cdc.gov/flu/
30

33. VACCINES
31
SEHRISH QAMAR

34. WHAT IS A VACCINE?
A vaccine is any preparation used as a preventive
inoculation to confer immunity against a specific
disease, usually using a harmless form of the disease
agent, such as killed or weakened bacteria or viruses.
The purpose of which is to stimulate antibody
production.
32

35. SOME BASICS
Most often the terms vaccination and immunization are used
interchangeably but their meanings are not exactly the same.
• A vaccine is a product that produces immunity from a disease and
can be administered through needle injections, by mouth, or by
aerosol.
• Vaccination is when a vaccine is administered to a person (usually
by injection).
• Immunization is what happens in one’s body after they have
been vaccinated. The vaccine stimulates one’s immune system so
that it can recognize the disease and offer protection from future
infection.
33

36. HISTORICAL MILESTONES
Vaccination is a miracle of modern medicine. In the past 50 years, it’s saved
more lives worldwide than any other medical product or procedure.
• 429 BC: Thucydides notices that people who survive smallpox do not
get re-infected
As long ago as 429 BC, the Greek historian Thucydides observed that those
who survived the smallpox plague in Athens did not become re-infected with
the disease.
• 900 AD: Chinese discover variolation
The Chinese were the first to discover and use a primitive form of vaccination
called variolation.
• 1700s: Variolation spreads around the world
Variolation eventually spread to Turkey, and arrived in England in the early
18th century. At this time, smallpox was the most infectious disease in Europe.
34

37. 1796: Edward Jenner discovers vaccination
British physician, Dr. Edward Jenner, discovered vaccination in its modern
form and proved to the scientific community that it worked.
1803: Royal Jennerian Institute founded
Support for vaccination grew. Jenner was awarded government funding, and in
1803 the Royal Jennerian Institutewas founded.
1870s: Violent opposition to vaccination
Although vaccination was taken up enthusiastically by many, there was some
violent opposition as it became more widespread. People felt that it took away
their civil liberties, particularly now that it was compulsory.
1880s: A vaccine against rabies
Louis Pasteur improved vaccination, and developed a rabies vaccine.
1890: Emil von Behring discovers the basis of diphtheria and tetanus
vaccines
German scientist, Emil von Behring, was awarded the first Nobel Prize in
Physiology orMedicine.
35

38. 1879
First Laboratory
Vaccine
Louis Pasteur
produced the
first laboratory-developed
vaccine: the
vaccine for
chicken cholera.
36

39. An image from the Florentine Codex
compiled in Mexico in the 1500’s
showing the devastating effects of
Smallpox on the native population.
Edward Jenner with
James Phipps.
37

40. 1920s: Vaccines become widely available
By the end of the 1920s, vaccines for diphtheria, tetanus, whooping
cough and tuberculosis were all available.
1955: Polio vaccination begins
Polio vaccination was introduced in the UK and it dramatically reduced the
number of cases.
1956: WHO fights to eradicate smallpox
The first attempt to use the smallpox vaccine on a global scale began when the
World Health Organization (WHO) decided to try and eradicate
smallpox across the world.
1980: Smallpox eradicated from the world
Smallpox was declared eradicated in 1980. It was one of the most remarkable
achievements in the history of medicine.
2008: Cervical cancer scientist awarded Nobel Prize
Professor Harald zur Hausen discovered that cervical cancer was caused by a
virus, making it possible to develop a vaccine for the disease.
38

41. 2008: NHS vaccinates girls against cancer
In England, the NHS cervical cancer vaccination programme began
whereby all 12-13 year-old-girls are offered HPV vaccination to protect them
against cervical cancer. This is the first time that a routine universal vaccine
was been given to prevent a type of cancer.
2013: NHS vaccinates against shingles and rotavirus
The NHS vaccination programme sees the introduction of rotavirus
vaccination for babies and a shingles vaccine for over-70s. A children's flu
vaccine is launched which is given as a nasal spray rather than an injection.
39

42. MECHANISM OF ACTION
Vaccines Produce:
• Humoral immunity (B cell response) i.e. most
bacterial vaccines
OR
• Cell-mediated immunity (T cell response) i.e. live
vaccines such as MMR and BCG
40

43. Humoral Immunity primarily
produces antibodies in the blood
circulation as a sensing or
recognizing function of the
immune system to the presence of
foreign antigens in the body.
Cell Mediated Immunity
primarily destroys, digests and
expels foreign antigens out of the
body through the activity of its
cells found in the thymus, tonsils,
adenoids, spleen, lymph nodes
and lymph system throughout the
body. This process of destroying,
digesting and discharging foreign
antigens from the body is known
as the acute inflammatory
response and is often accompanied
by the classic signs of
inflammation: fever, pain, malaise
and discharge of mucus, pus, skin
rash or diarrhea.
41

44. A vaccination consists of introducing a disease agent or
disease antigen into an individual’s body without
causing the disease. If the disease agent provoked the
whole immune system into action it would cause all the
symptoms of the disease. The symptoms of a disease are
primarily the symptoms (fever, pain, malaise, loss of
function) of the acute inflammatory response to the
disease. So the trick of a vaccination is to stimulate the
immune system just enough so that it makes antibodies
and remembers the disease antigen but not so much
that it provokes an acute inflammatory response by the
cellular immune system and makes us sick with the
disease we are trying to prevent.
42

45. VACCINES PRODUCING HUMORAL
IMMUNITY
• B cells are a type of lymphocyte (white blood
cells) capable of producing antibodies.
• B cells with the right receptor shape recognise
a vaccine antigen and bind to it
• The B cells are activated to produce a clone of
antibodies with the same specificity
43

46. 44

47. VACCINES PRODUCING HUMORAL
IMMUNITY
• The B cells mature and become “plasma”
cells (capable of excreting 2000 molecules
antibody/second) and “memory” cells
• If the “memory” cells encounter the
antigen again they will change into plasma
cells and produce large numbers of specific
antibodies
• The size, specificity and speed of the
response will increase with repeated exposure
45

48. HELP FROM T CELLS IN THE HUMORAL
RESPONSE
A certain type of T cell (helper or CD4 cell) can help
B cells differentiate into clones. (Where this is an
essential element for a particular vaccine this is
termed a “T cell dependent” response)
46

49. PRIMARY IMMUNE RESPONSE
• Primary immune
response develops
in the weeks
following first
exposure to an
antigen. Mainly
IgM antibody
• Secondary
immune response
is faster and more
powerful.
Predominantly
IgG antibody
47

50. DIFFERENT TYPES OF VACCINES
Vaccines are made using several different processes. The different
vaccine types each require different development techniques.
Live, Attenuated Vaccines
Attenuated vaccines can be made in several different ways. Some of the
most common methods involve passing the disease-causing virus
through a series of cell cultures or animal embryos (typically chick
embryos). Using chick embryos as an example, the virus is grown in
different embryos in a series. With each passage, the virus becomes
better at replicating in chick cells, but loses its ability to replicate in
human cells. When the resulting vaccine virus is given to a human, it
will be unable to replicate enough to cause illness, but will still provoke
an immune response that can protect against future infection.
Examples: Measles, mumps, rubella, Varicella (chickenpox),
Influenza and Rotavirus
48

51. Vaccine type
Vaccines of this type on U.S.
Recommended Childhood (ages 0-6)
Immunization Schedule
Live, attenuated
Measles, mumps, rubella (MMR combined
vaccine)
Varicella (chickenpox)
Influenza (nasal spray)
Rotavirus
Inactivated/Killed
Polio (IPV)
Hepatitis A
Toxoid (inactivated toxin)
Diphtheria, tetanus (part of DTaP combined
immunization)
Subunit/conjugate
Hepatitis B
Influenza (injection)
Haemophilus influenza type b (Hib)
Pertussis (part of DTaP combined
immunization)
Pneumococcal
Meningococcal
49

52. Vaccine type Other available vaccines
Live, attenuated
Zoster (shingles)
Yellow fever
Inactivated/Killed Rabies
Subunit/conjugate Human papillomavirus (HPV)
50

53. Killed or Inactivated Vaccines:
Vaccines of this type are created by inactivating a pathogen, typically
using heat or chemicals such as formaldehyde or formalin. This
destroys the pathogen’s ability to replicate, but keeps it “intact” so
that the immune system can still recognize it.
Examples: Polio (IPV), Hepatitis A
Toxoids:
Some bacterial diseases are not directly caused by a bacterium itself,
but by a toxin produced by the bacterium. One example is tetanus:
its symptoms are not caused by the Clostridium tetani bacterium,
but by a neurotoxin it produces. Immunizations for this type of
pathogen can be made by inactivating the toxin that causes disease
symptoms. As with organisms or viruses used in killed or inactivated
vaccines, this can be done via treatment with a chemical such as
formalin, or by using heat or other methods. Immunizations created
using inactivated toxins are called toxoids.
Examples: Diphtheria, tetanus 51

54. Subunit and
Conjugate Vaccines:
Both subunit and conjugate
vaccines contain only pieces
of the pathogens they
protect against. Subunit
vaccines use only part of a
target pathogen to provoke a
response from the immune
system. This may be done by
isolating a specific protein
from a pathogen and
presenting it as an antigen
on its own. Another type of
subunit vaccine can be
created via genetic
engineering.
Examples: Acellular
pertussis vaccine and
influenza vaccine.
52

55. VACCINE PREVENTABLE DISEASES
Some vaccine-preventable
diseases are
listed below:
• Cholera
• Diphtheria
• Hepatitis A
• Hepatitis B
• Influenza
• Rabies
• Rubella
• Smallpox
• Tetanus
• Influenza Disease
• Invasive Meningococcal
Disease
• Japanese Encephalitis
• Measles
• Mumps
• Pertussis
• Pneumococcal
• Poliomyelitis
• Typhoid
• Varicella
• Yellow Fever
53

56. DISEASE ERADICATION
• When a disease stops circulating in
a region, it’s considered eliminated
in that region. Polio, for example,
was eliminated in the United
States by 1979 after widespread
vaccination efforts.
• If a particular disease is eliminated
worldwide, it’s considered
eradicated. To date, only one
infectious disease that affects
humans has been eradicated. In
1980, after decades of efforts by the
World Health Organization, the
World Health Assembly endorsed
a statement declaring smallpox
eradicated.
Smallpox eradication
campaign
54

57. DISEASE ERADICATION
• The eradication of smallpox raised hopes that the
same could be accomplished for other diseases,
with many named as possibilities: polio, mumps,
and Guinea worm disease, among others. Malaria
has also been considered, and its incidence has
been reduced drastically in many countries. It
presents a challenge to the traditional idea of
eradication, however, in that having malaria does
not result in lifelong immunity against it (as
smallpox and many other diseases do).
55

58. Red is measles,
green is whooping
cough, yellow is
polio, and blue is
rubella.
56

59. Factors Influencing Vaccination uptake in
Pakistan
Pakistan, one of the three endemic polio reservoirs, is posing a
serious threat to the success of the Global Polio Eradication
Initiative to eradicate polio completely. Some of the hurdles known
to retard the campaign include:
i. The war against terrorism
ii. Misconceptions about polio vaccine
iii. Religious misinterpretations
iv. Frustration among vaccinators
v. Lack of awareness
vi. Social considerations
vii. Natural calamities
viii.Inaccessibility
Inefficient vaccines and weak health management is
found at the hub of majority of the challenges. 57

60. 58

61. REFERENCES
www.unicef.org
www.historyofvaccines.org
www.vaccines.com
http://www.immune.org.nz/types-vaccines
http://wenliang.myweb.uga.edu/mystudy/immunology/Scie
nceOfImmunology/NotesImages/Topic247NotesImage2.gif
http://www.who.int/i
http://philipincao.crestonecolorado.com/index_htm_files/H
ow%20Vaccinations%20Work.pdfmmunization/documents/
Elsevier_Vaccine_immunology.pdf
59

62. GENE THERAPY
NEELAM PERVEEN 60

63. GENES
• Are carried on a chromosome
• The basic unit of heredity
• Encode how to make a protein-DNARNA
proteins
• Proteins carry out most of life’s function.
• When altered causes dysfunction of a protein
• When there is a mutation in the gene, then it
will change the codon, which will change
which amino acid is called for which will
change the conformation of the protein which
will change the function of the protein.
Genetic disorders result from mutations in the
genome.
61

64. GENE THERAPY
• It is a technique for correcting defective genes that are
responsible for disease development. Its the elaboration of the
recombinant DNA technology that brought gene therapy into
the realm of feasibility.
62

65. Classes
• There are two basic "classes" of gene therapy.
 Somatic cell gene therapy : Somatic cell gene therapy
changes/fixes/replaces genes in just one person. The
targeted cells are the only ones affected, the changes are
not passed on to that person's offspring.
 Germ line gene therapy: · Germ line gene therapy makes
changes in the sperm or egg of an individual. The changes
that are made, adding or subtracting genes from the
person's DNA, will be passed on to their offspring. This
type of gene therapy raises a lot of ethical questions
because it impacts the inheritance patterns of humans.
63

66. APPROACHES
• There are four approaches:
1. A normal gene inserted to compensate for a nonfunctional
gene.
2. An abnormal gene traded for a normal gene
3. An abnormal gene repaired through selective reverse
mutation
4. Change the regulation of gene pairs
64

67. AIM
• Gene insertion therapy aims to insert a good copy of the
gene or the desired gene without regard to the presence of
the deleterious gene.
• It does not attempt to eliminate or delete the bad gene. The
objective here is to insert the non defective or desired gene
in such a way that it makes enough product to compensate
for the inability of the defective resident gene to produce
such a product.
• The celebrated cases of the first human gene therapy trial
involving adenosine deaminase deficiency is an example of
this approach.
65

68. SUCCESSFUL GENE THERAPY FOR SEVERE
COMBINE IMMUNODEFICIENCY
• Infants with severe combined immunodeficiency
are unable to mount an adaptive immune response,
because they have a profound deficiency of
lymphocytes.
• severe combined immunodeficiency is inherited as
an X-linked recessive disease, which for all practical
purposes affects only boys. In the other half of the
patients with severe combined immunodeficiency,
the inheritance is autosomal recessive — and there
are several abnormalities in the immune system
when the defective gene is encoded on an
autosome. 66

69. SEVERE COMBINE
IMMUNODEFICIENCY CONT.
• A previous attempt at gene therapy for
immunodeficiency was successful in
children with severe combined
immunodeficiency due to a deficiency of
adenosine deaminase. In these patients,
peripheral T cells were transduced with a
vector bearing the gene for adenosine
deaminase. The experiment was extremely
labor intensive, because mature peripheral-blood
T cells were modified rather than
stem cells, and the procedure therefore had
to be repeated many times to achieve
success.
67

70. HOW IT WORKS
• A vector delivers the therapeutic gene into a patient’s target cell
• The target cells become infected with the viral vector
• The vector’s genetic material is inserted into the target cell
• Functional proteins are created from the therapeutic gene causing
the cell to return to a normal state
68

71. THE FIRST CASE
• The first gene therapy was performed on September 14th,
1990
• Ashanti DeSilva was treated for SCID
• Sever combined immunodeficiency
• Doctors removed her white blood cells, inserted the missing
gene into the WBC, and then put them back into her blood
stream.
• This strengthened her immune system
• Only worked for a few months 
69

72. SCID CONT.
70

73. GENE THERAPY
In vivo Ex vivo
71

74. IN VIVO GENE THERAPY
• The genetic material is transferred directly into the
body of the patient
• More or less random process
• Small ability to control
• Less manipulations
• Only available option for tissues that can not be grown
in vitro; or if grown cells can not be transferred back
72

75. EX VIVO GENE THERAPY
• The genetic material is first transferred into the cells grown
in vitro
• Controlled process
• Genetically altered cells are selected and expanded
• More manipulations
• Cells are then returned back to the patient
73

76. HOW TO FIX A PROBLEM?
USE VECTORS
A
B C A a beneficial gene
virus modified virus
• A virus is found which replicates by inserting its genes into
the host cell's genome. This virus has three genes - A, B and
C.
• Gene A encodes a protein which allows this virus to insert
itself into the host's genome.
• Genes B and C actually cause the disease this virus is
associated with.
• Replace B and C with a beneficial gene. Thus, the modified
virus could introduce your 'good gene' into the host cell's
genome without causing any disease.
74

77. VIRUSES
• Replicate by inserting their DNA into a host cell
• Gene therapy can use this to insert genes that encode for a
desired protein to create the desired trait
• Four different types
75

78. RETROVIRUSES
• Created double stranded DNA copies from RNA
genome
• The retrovirus goes through reverse transcription
using reverse transcriptase and RNA
• the double stranded viral genome integrates into the
human genome using integrase
• integrase inserts the gene anywhere because it has no
specific site
• May cause insertional mutagenesis
• One gene disrupts another gene’s code (disrupted cell
division causes cancer from uncontrolled cell division)
• vectors used are derived from the human
immunodeficiency virus (HIV) and are being
evaluated for safety
76

79. ADENOVIRUSES
• Are double stranded DNA genome that cause respiratory,
intestinal, and eye infections in humans
• The inserted DNA is not incorporate into genome
• Not replicated though 
• Has to be reinserted when more cells divide
• Ex. Common cold
77

80. ADENOVIRUS cont.
http://en.wikipedia.org/wiki/Gene_therapy
78

81. ADENO-ASSOCIATED VIRUSES
• Adenoassociated virus, a virus much smaller than the adenovirus
but usually isolated with adenovirus as that virus needed for the
reproduction of adeno-associated virus, can also infect human
cells, and its genes are integrated into the host cell chromosome,
therefore allowing for the long-term, stable expression of the gene.
• Adeno-associated Virus- small, single stranded DNA that insert
genetic material at a specific point on chromosome 19
• From parvovirus family- causes no known disease and doesn't
trigger patient immune response.
• Low information capacity
• Gene is always "on" so the protein is always being expressed,
possibly even in instances when it isn't needed.
• Hemophilia treatments, for example, a gene-carrying vector could
be injected into a muscle, prompting the muscle cells to produce
Factor IX and thus prevent bleeding.
• Study by Wilson and Kathy High (University of Pennsylvania),
patients have not needed Factor IX injections for more than a
year 79

82. HERPES SIMPLEX VIRUSES
• Double stranded DNA viruses that infect
neurons
• Herpes virus, with some members causing
cold sores in humans, has the proclivity to
infect cells of the nervous system and
therefore may provide the vehicle to deliver
desired genes to this otherwise generally
inaccessible system.
• Other herpes viruses preferentially infect
human cells in the blood, and vectors
based on them could be utilized to deliver
genes to the immune cells.
• Ex. Herpes simplex virus type 1
80

83. NON-VIRAL OPTIONS
• Direct introduction of therapeutic DNA
• But only with certain tissue
• Requires a lot of DNA 
• Creation of artificial lipid sphere with aqueous core, liposome
• Carries therapeutic DNA through membrane
• Chemically linking DNA to molecule that will bind to special
cell receptors
• DNA is engulfed by cell membrane
• Less effective 
• Trying to introduce a 47th chromosome
• Exist alongside the 46 others
• Could carry a lot of information
• But how to get the big molecule through membranes?
81

84. CURRENT STATUS
• FDA has not approved any human gene therapy
product for sale
• Reason:
January 2003, halt to using retrovirus vectors in blood
stem cells because children developed leukemia-like
condition after successful treatment for X-linked
severe combined immunodeficiency disease 82

85. GENE THERAPY IN PAKISTAN
• Breast cancer is one of the most common cancers among women around the
world. It accounts for 22.9% of all the cancers and 18% of all female cancers
in the world.
• One million new cases of breast cancer are diagnosed every year. Pakistan
has more alarming situation with 90,000 new cases and ending up into
40,000 deaths annually. The risk factor for a female to develop breast cancer
as compared with male is 100 : 1.
• The traditional way of treatment is by surgery, chemotherapy or
radiotherapy. Advanced breast cancer is very difficult to treat with any of the
traditional treatment options. A new treatment option in the form of gene
therapy can be a promising treatment for breast cancer.
• Gene therapy provides treatment option in the form of targeting mutated
gene, expression of cancer markers on the surface of cells, blocking the
metastasis and induction of apoptosis, etc.
• Gene therapy showed very promising results for treatment of various
cancers. All this is being trialed, experimented and practiced outside of
Pakistan. Therefore, there is an immense need that this kind of work should
be started in Pakistan. There are many good research institutes as well as
well-reputed hospitals in Pakistan working over it. 83

86. POPULAR CULTURE
• Gene therapy is the basis for the
plotline of the film I Am Legend
• I Am Legend is a 2007
American post-apocalyptic science
fiction horror film directed
by Francis Lawrence and
starring Will Smith. Smith
plays virologist Robert Neville,
who is immune to a man-made
virus originally created to
cure cancer. He works to create a
remedy while defending himself
against mutants created by the
virus.
84

87. POPULAR CULTURE CONT.
• Gene therapy is the basis for the
plotline of the film Rise of the
Planet of the Apes
• In the 2011 film Rise of the Planet
of the Apes, a fictional gene
therapy called ALZ-112 was a drug
that was a possible cure
for Alzheimer's disease, the
therapy increased the host's
intelligence and made their irises
green, along with the revised
therapy called 113 which increased
intelligence in apes yet was a
deadly, internal virus in humans.
85

88. PROBLEMS WITH GENE THERAPY
• Short Lived
• Hard to rapidly integrate therapeutic DNA into genome and
rapidly dividing nature of cells prevent gene therapy from long
time
• Would have to have multiple rounds of therapy
• Immune Response
• new things introduced leads to immune response
• increased response when a repeat offender enters
• Viral Vectors
• patient could have toxic, immune, inflammatory response
• also may cause disease once inside
• Multigene Disorders
• Heart disease, high blood pressure, Alzheimer’s, arthritis and
diabetes are hard to treat because you need to introduce more
than one gene
• May induce a tumor if integrated in a tumor suppressor gene
because insertional mutagenesis 86

89. References
• http://openreads.com/chapter/one-world-chapter-7-advances-in-genetics-
gene-therapy/
• http://my.safaribooksonline.com/book/biotechnology/0131010115/gene-therapy/
ch07#X2ludGVybmFsX0h0bWxWaWV3P3htbGlkPTAtMTMtM
TAxMDExLTUlMkZjaDA3bGV2MXNlYzMmcXVlcnk9
87

90. 88