Yen Phan
May 15, 2014
Andrew Grosovsky
Final Seminar Paper
For our presentation project, we decided to compare vaccine and antibiotic treatment for
viral and bacterial infections in order to illustrate the challenges of controlling the emerging
viruses and epidemics. Our question is how do emerging viruses increase the importance of
vaccines in controlling epidemics? The reason why we choose this particular questions this that
viruses have caused some of the most dramatic and deadly disease pandemics in human history.
In the 20th century alone smallpox killed between 300-500 million people before its eradication
in 1980. The 1918-1919 “Spanish Flu” pandemic infected roughly one-third of the world's
human population causing an estimated 50-100 million deaths. In 2009, a novel swine-origin
H1N1 strain of influenza virus rapidly spread to over 213 countries causing the first declared
pandemic of the 21st century. From these staggering statistics, emerging virus is one of the
biggest threat people in our society face and will be a big problem in the future since more and
more people are traveling all over the world then ever before. Virus can easily spread between
people to people within a few months and it could spread all over the worlds and there is nothing
to stop it until we have a new vaccine for it and that could take months to develop. Millions of
people would have die from this epidemic in the meantime. I really wanted to know more about
vaccine and antibiotic to understand why it is so hard to treat so that we can find a solution to the
problems and treat the disease in the future.
With the topics and questions in mind, I searched the web to know everything I could
regard to vaccine and antibiotic to see how it play a role in emerging virus. Some of the
examples of the website I looked into are the World Health Organization, the History of
Vaccine.org, Centers for Disease Control and Prevention-Understanding How does Vaccines
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works, Vaccines.gov and the University of California San Francisco- Immunology Module,
University of South Carolina School of Medicine Immunology, and countless other sources
online.
Based on the source, I found that a vaccine is a substance that is used to stimulate our
immune system to produce antibodies. It also provides immunity without actually infecting us
with the disease. There are different ways vaccines are created. In weakening the virus,
producers take out the weakened form of a virus and so it cannot reproduce rapidly. The virus
then cannot do much harm to the body. Memory B cells from our body store memory of virus, so
if the same virus enters the body again the memory B cells can produces the immune response
and attack the virus quickly preventing it from reproducing in the future. In inactivate the virus,
the vaccine viruses are first killed with a chemical and so it cannot reproduce or cause any
disease. In some vaccines, a protein or a part of the virus that resides on the surface of the virus
is removed and used as a vaccine. This vaccine is used when an immune response to one part of
the virus is responsible for protection against the disease. Lastly, a vaccine can be produce by
inactivating the toxins, a harmful protein, that viruses make to harm humans. Several vaccines
with a chemical are made to inactivate the toxins, so they cannot cause the disease.
After knowing how are vaccines created, I looked into the functions and mechanism of
how does vaccines work. There are several ways a vaccine work. Each vaccine is designed to
work in a specific way to stop the virus from reproducing. In interference in DNA synthesis, the
vaccines mimic DNA or RNA building blocks so that it can stop enzyme from making the new
viral DNA. In block reverse transcriptase, after the virus releases its genetic material into a host
cell, reverse transcriptase converts the viral RNA into a complementary piece of DNA. Block
reverse transcriptase prevents reverse transcriptase, so that virus cannot incorporate its RNA into
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the host DNA and replicate. In block integration fusion of viral DNA with host DNA, the drug
tried to prevent the viral DNA from entering the host DNA. In inhibit uncoating of viruses; the
virus will uncoated and release genomic material in the human cell through viral or host
enzymes, or by capsid dissociation. Drugs prevent the virus from uncoating by blocking the
proteins on the capsid responsible for uncoating, such as ion channel proteins. For example, in
the case of Measles, also known as Rubeola, is a highly infectious illness caused by rubeola
virus. Viruses can only consists a hereditary molecule (DNA or RNA) strand. The DNA
segments get incorporated into the host cells DNA. Then, the viral DNA reproduced with the
host cell. Measles vaccine works by blocking the reverse transcriptase to stop the viruses from
reproducing rapidly.
After knowing about vaccine, I looked into the functions and mechanism of antibiotics.
Antibiotics are substances that are used to kill or inhibit the growth of bacteria. Most of the
antibiotics are modified chemically from original compounds found in nature, while some of the
antibiotics are isolated and produced from living organisms. They either prevent the bacterial
cells from multiplying so that the bacterial population remains the same, allowing the host’s
defense mechanism to fight the infection or kill the bacteria. For example, it works by stopping
the mechanism responsible for building their cell walls. Some antibiotics kill bacteria directly
and they are classified as bactericidal, while other antibiotics prevent bacteria cell division and
they are classified as bacteriostatic. Antibiotics are classified by target specificity; it can be
classified as narrow spectrum and broad range depending on the number of bacteria it targets.
Narrow-spectrum antibiotics target specific bacteria whereas broad range antibiotics target many
groups of bacteria. For example, in the case of penicillin G, it will destroy only a few species of
bacteria so therefore it is classified as a narrow spectrum antibiotic.
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Different antibiotics have different modes of action to target specific sites within bacterial
cells. In the case of inhibitors of cell wall and membrane functions, human do not have cell
walls, but bacteria do. Therefore, a drug that targets cell walls can selectively inhibit or kill
bacterial organisms. Cell membranes are segregate by the intra- and extracellular flow of
substances. Drug that target cell membrane will disrupt or damage to this structure and result in
leakage of solutes essential for the cell’s survival. In inhibitors of protein synthesis, the
production of protein or protein synthesis is necessary for the survival and replication of bacterial
cells. Antibacterial agents target bacterial protein synthesis by binding to either the 30S or 50S
subunits of the ribosomes, which disrupt cellular metabolism and leading disruption in cellular
replication. In inhibitors of nucleic acid synthesis, DNA and RNA are keys to the replication of
bacteria. Some antibiotics work by binding to components involved in the process of DNA or
RNA synthesis, which interfere with cellular processes leading to disruption in cellar
replication. Lastly, in inhibitors of other metabolic processes, other antibiotics act on selected
cellular processes essential for the survival of the bacterial pathogens. For example, both
sulfonamides and trimethoprim disrupt the folic acid pathway, which is necessary step for
bacteria to produce precursors important for DNA synthesis. As an example of bacteria that can
be treated using antibiotics, Staphylococcus Aureus is a common bacterium that causes
infections in different parts of the body. Antibiotics inhibit the synthesis of cell wall of bacteria
and prevent growth. In the case of Methicillin-resistant Staphylococcus Aureus also known as
Methicillin Resistant Staphylococcus Aureus, it's resistant to commonly used antibiotics.
Based on all the research and data gathered, antibiotics are effective against a range of
bacteria; vaccines are specific to unique antigens. Humans have antibodies and other immunity
mechanism to defend itself against infection. In addition, bacteria are large and complex
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microorganism that can be targeted using antibodies from multiple bacterial sites; therefore it’s
easier to treat bacteria. On the other hand, viruses are very small and simple in structure so
specific vaccines are needed to treat virus infection. If new form of virus appears then there
would not be any treatment for it right away, whereas if a new form of bacteria appears then
there are antibiotics and other factors to fight the bacteria. Therefore, no effective medication
will be immediately available to control the spread of newly emerging viruses. Further questions
to be address for a better grasp of emerging virus are why can’t we come up with a permanent
vaccine for Influenza? How can we make vaccine more affordable? What are news ways to
target bacteria that are resistant to antibiotics?