Lecture 1 Flashcards
(142 cards)
1
Q
Causes of infectious disease
A
Infectious diseases are caused by pathogens, which are microorganisms that can cause disease in humans. Pathogens can include bacteria, viruses, fungi, and parasites.
2
Q
How microbes replicate
A
Microbes replicate in different ways, depending on the type of microbe. Bacteria replicate by binary fission, which is a process where one bacterium divides into two identical daughter cells. Viruses replicate by hijacking the host cell’s machinery and using it to make new copies of the virus. Fungi replicate by producing spores, which are tiny reproductive cells. Parasites replicate by reproducing inside the host organism.
3
Q
How microbes infect humans
A
Ingestion: Microbes can be ingested through food or water. For example, Salmonella bacteria can be ingested through contaminated chicken or eggs.
Inhalation: Microbes can be inhaled through the air. For example, Mycobacterium tuberculosis bacteria can be inhaled through the air and cause tuberculosis.
Contact: Microbes can be transmitted through contact with an infected person or animal. For example, the herpes simplex virus can be transmitted through contact with an infected person’s sores.
Vector-borne transmission: Microbes can be transmitted through vectors, which are animals that carry and transmit diseases. For example, the malaria parasite is transmitted by Anopheles mosquitoes
4
Q
Is all microbial life pathogenic?
A
No, not all microbial life is pathogenic. In fact, the vast majority of microbes are harmless to humans. In fact, many microbes are beneficial to humans, such as the bacteria that live in our gut and help us to digest food.
5
Q
Do all pathogenic microbes kill the host cell?
A
No, not all pathogenic microbes kill the host cell. Some microbes, such as viruses, can replicate inside the host cell without killing it. Other microbes, such as bacteria, can kill the host cell, but this is not always the case.
6
Q
Infectious Disease around the world
A
Used to be more regional, but through globalization, these specific regional diseases don’t really exist anymore. Diseases disseminate quickly & do not stick to certain regions. Before globalization, this did exist.
Examples: TB in areas of Africa and North America & West Nile virus in the states
7
Q
Explain the relationship between public health and infectious disease
A
Public health efforts help made the spread of disease less common, and decreased the death rate per year. As more money was put into funding certain initiatives like cleaning the water supply and the vaccines, there was a correlation seen with how many deaths were seen each year.
8
Q
When were antibacterial agents developed?
A
In the 20th century
9
Q
When did antivirals start to be developed? (before/after antibacterial agents)
A
Much later than antibacterial agents
10
Q
Why did antivirals start to be developed later?
A
Antivirals are more difficult to develop than antibiotics because viruses are more complex and replicate inside host cells & to develop viruses you would have to kill the infected cells and thus kill human cells
11
Q
21st century developments
A
genomic & proteomics
12
Q
Gene sequencing
A
Can now sequence an organism’s DNA in hours instead of years & development in this field has increased dramatically
13
Q
Antibiotic development
A
Antibiotics invented well up to the 2000, dwindled after
Diseases are becoming antibiotic resistance
There is a big market for antibiotics worldwide, big-pharma doesn’t want to engage since those markets cannot pay (broke)
14
Q
Antiviral discovery
A
Overall, is expensive.
AIDS epidemic in 1985 stimulated the development of many antivirals.
Viruses are complex and diverse, and there is no one-size-fits-all approach to antiviral drug development.
15
Q
Big pharma & their menace behavior?
A
The pharmaceutical industry is more interested in developing drugs for diseases with a large market potential, such as chronic diseases. Antiviral drugs often have a smaller market potential, as they are typically used to treat acute infections.
Flu shot - needs new variant every year, no real interest form BigPharm to develop/invest
16
Q
How does MRNA Vaccines play into this antiviral development?
A
mRNA introduced low cost way of manufacturing vaccines (SARS-COVID)
The development of new technologies, such as mRNA vaccines and gene editing, could revolutionize antiviral drug discovery.
17
Q
Size of viruses in comparison to bacteria and protozoa
A
Viruses: 0.03-0.3um
Bacteria: 0.1-10um
Viruses are 100-1000x smaller than bacteria
18
Q
How does the size of a microorganism affect its biology?
A
The size of a microorganism can have a big impact on its biology. For example, smaller microorganisms are able to move more quickly and squeeze into smaller spaces. While larger microorganisms are better able to store nutrients and reproduce.
19
Q
Increasing complexity of microorganisms?
A
Increasing complexity: viruses → bacteria → fungi → parasites
20
Q
Parasites
A
exist as single or multicellular structures with the same cell plan of our own cells including ORGANELLES like a nucleus and cytoplasmic
21
Q
Fungi
A
Eukaryotic, but have a rigid external wall that makes them seem more like plants than animals.
22
Q
Bacteria
A
Bacteria also have a cell wall, but with a cell plan called “prokaryotic” that lacks ORGANELLES.
NO organelles
23
Q
Viruses
A
Viruses are not cells at all.
*** THEY HAVE A DNA GENOME but they MUST take over another cell in order to replicate.
24
Q
Naked Virus
A
Is a virus that does not have a lipid envelope. ONLY contains the protein capsid that has the genome
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Enveloped Virus
An enveloped virus is a virus that has a lipid envelope surrounding its protein capsid that is derived from the host cell membrane when the virus buds off from the cell
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True or False: viruses contain organelles
FALSE: Viruses contain little more than DNA or RNA
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Bacteria
Smallest living cells.
Have a cytoplasm surrounded by a cell wall
However, they also do not have any organelles or a nucleus
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If bacteria have no nuclei, where does protein necessary to replicate go?
Their cytoplasm contains the ribosomes and a single, double-stranded DNA chromosome.
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How do bacteria divide?
Binary fission
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Fungi types
Are yeast or mold
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Structure of fungi
Fungi are eukaryotic and have a rigid external cell wall & all the organelles.
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How is the genome held in fungi?
Diploid or haploid state inside a nucleus
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Parasites
Most diverse and can range from unicellular amoebas to multicellular tapeworms
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Do parasites have organelles?
Yes. They are eukaryotic organisms that can be highly differentiated
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Do parasites always have to depend on another living thing to survive?
No. Most parasites are free living but some can depend on animals for survival.
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True or False: Bacteria are the smallest microorganism types & are the least complex
False. Viruses are the least complex since the only contain DNA or RNA
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Prokaryotic Cells
VIRUSES & BACTERIA:
No distinguished nucleus
No organelles
Extrachromosomal DNA exists in plasmids
No sterols
Cell walls of peptidoglycan
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Eukaryotic Cells
Fungi & parasites:
Has a nucleus
Has organelles
Has organelles for extrachromosomal DNA
Have sterols
& no peptidoglycan although sometimes cellulose can exist
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Common routes of transmission
Respiratory, Salivary, Eye, skin, genitally, blood, urine, animals
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Direct transmission
Coughing or sneezing on someone
Coming into contact with an infected person's bodily fluids, such as blood, saliva, or semen
Having sexual contact with an infected person
Touching an infected person's sores or rash
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indirect transmission
Being bitten by an infected mosquito
Eating contaminated food or water
Touching a contaminated surface and then touching your eyes, nose, or mouth
Breathing in contaminated air
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Horizontal transmission
From infected individual to another individual of the same generation.
Ex: Digate coughing on us in class while he had COVID. (he didn't give it to anyone but he could have 🙂)
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Vertical Transmission:
From mother to offspring. Ex: postpartum transmission or while in the womb.
EX: HIV from mother to baby
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Classes of microbiota
Microbiome (Our flora)
Commensal (residential, symbiotic)
Transient colonization
Opportunistic
Pathogenic
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Commensal microorganisms
A commensal is an organism that lives on or in another organism without causing harm or benefit. They are often essential for the health of the host, and their absence can lead to disease.
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Presence of commensal microorganisms in the body
More than 1000 species and there are billions of organisms
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What are the functions of commensal microorganisms in the body?
Digesting food, essential vitamins and growth factor as well as protection against invasion of pathogens. This is because they are territorial (as learned in immunology)
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Do children have a flora?
Yes, they will start to develop one at birth and over time it's something that is developed over age.
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What does the microbiome health depend on?
illness, age, diet and health
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What happens to the microbiome when we take antibiotics?
When we take antibiotics, they kill both harmful and beneficial bacteria in our gut. This can disrupt the balance of the microbiome and lead to a variety of health problems, including stomach problems. Doctors can suggest you eat yogurt (filled with probiotics) while you're on an antibiotic to help combat this
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Virulence
The circumstances that allow a microorganism to achieve infections and cause diseases
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Gaining access to the body:
Gaining access to the body:
Structures like pili and hairs on the body of the bacteria can help it attach to host cells
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Avoiding multiple host defenses:
Capsules, proteases, antigenic variation, etc
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Colonization of the host
Nutrient acquisition systems: Bacteria needs nutrients to survive & pumps that remove harmful substances like antibiotics
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Parasitizing host resources
examples to help understand it (not in the textbook):
Small molecules that bind iron and make it available to bacteria
Enzymes that lyse red blood cells, releasing iron and other nutrients
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Inducing toxicity and damage
Endotoxins/exotoxins that damage host cells
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Opportunistic microbes
(take advantage of an opportunity)
Microbiome dies (b/c of antibiotics or any other reason)
Pathogenic bacteria will take over & produce toxins that will cause injury
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Influences on the human microbiome
Host physiology:
Age/sex/site
Environment:
Climate/ geographic location
Immune system:
Previous exposures or inflammation
Host Genotype:
Genes like flaggirin
Lifestyle:
Occupation & hygiene
Pathobiology: conditions like diabetes
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Human Microbiome Project
The HMP aimed to characterize the human microbiota, which is the community of microorganisms that live on and in the human body. (dont think we need to know this)
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Resident Microbiota
Resident microbiota Are present in many different areas of the body and have low virulence which means that they do not cause disease. They help with digestion, boosting immunity and with protecting the body.
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Potential pathogens
Can exist on different parts of the body. Can become pathogenic but are usually kept in check by the immune system. Opportunistic because they will wait for a disruption to invade
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How do microbes get into the body?
Because human cells were not designed to receive the microorganisms, the pathogens are often exploiting some molecule important for some other essential function of the cell
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How do viruses get into the cell?
he virus first attaches to the host cell surface using receptor proteins on the surface of the virus and complementary receptors on the host cell surface (1). The virus then enters the host cell by endocytosis (2). Once inside the host cell, the virus uncoats and releases its genome (3). The viral genome is then replicated by the host cell's machinery (4). New viral proteins are also synthesized by the host cell (5). The new viral proteins and genome are then assembled into new virus particles (6). The new virus particles are then released from the host cell by exocytosis (7).
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How to bacteria get into the cell?
The bacterial cell attaches to the surface of the host cell. The bacterium then invades the host cell and spreads through the cell to the bloodstream. This type of infection is known as an invasive bacterial infection. Invasive bacterial infections can be very serious and can lead to death.
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How does the bacteria affect the cell even if it doesn't enter it?
Attaches to the surface of the host cell and injecting proteins into the cell. The cell is disrupted while the organism remains on the surface. This type of infection is known as a cytopathic infection. Cytopathic infections can damage or kill the host cell.
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Immune response against bacteria
Phagocytosis, which is a process by which a cell engulfs and digests another cell or particle.
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What are the properties of a virus?
Viruses are acellular, obligate intracellular parasites, and made up of genetic material and a protein coat.
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Which properties do all viruses share?
All viruses are acellular, obligate intracellular parasites, and made up of genetic material and a protein coat.
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Do all viruses kill the cells they infect?
No, not all viruses kill the cells they infect. Some viruses can cause the cell to lyse and release new virus particles, while others can integrate their genetic material into the host cell's genome and replicate along with the host cell's DNA.
70
Yes, all viruses are completely dependent on the host cell.
Yes, all viruses are completely dependent on the host cell. Viruses cannot replicate or produce energy on their own. They rely on the host cell's machinery to replicate and produce new virus particles.
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What are the five key properties of viruses?
All viruses are intracellular pathogens, must use some components of the host cell's biosynthetic machinery, are nucleic acid based, replicate by assembly of components, and are composed of the viral genome, a protective coat, and associated enzymes/proteins.
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What does it mean that viruses are intracellular pathogens?
It means that viruses can only live and reproduce inside of a host cell
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What does it mean that viruses must use some components of the host cell's biosynthetic machinery?
It means that viruses need to use some of the host cell's machinery to make new viral particles.
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What does it mean that viruses are nucleic acid based?
It means that the genetic material of a virus is made up of either DNA or RNA.
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What does it mean that viruses replicate by assembly of components?
It means that viruses make new viral particles by assembling together the different components of the virus, such as the capsid, envelope, and genome.
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What does it mean that viruses are composed of the viral genome, a protective coat, and associated enzymes/proteins?
It means that all viruses have a genetic material, a protein coat that protects the genetic material, and other enzymes and proteins that are needed for the virus to replicate and infect host cells.
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Naked Capsid Virus:
DNA & structural proteins & enzymes = Nucleocapsid
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Enveloped Virus
Nucleocapsid (everything from the naked capsid virus) + Glycoproteins and membrane
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Spike Protein
Spike proteins are viral surface proteins that mediate the attachment of the virus to host cells.
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Viral Attachment Proteins
Viral attachment proteins (VAPs) are a broader category of viral proteins that mediate the attachment of the virus to host cells.
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DNA VIRUSES
Contain double-stranded DNA (dsDNA) as their genetic material. Some common examples of DNA viruses include herpes simplex virus (HSV), human papillomavirus (HPV), and Epstein-Barr virus (EBV).
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RNA Viruses
contain single-stranded RNA (ssRNA) as their genetic material. Some common examples of RNA viruses include influenza virus, HIV, and SARS-CoV-2.
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Nucleic Acid component of a virus
DNA/ RNA
Single or double stranded
can be circular or linear
and continuous or segmented
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outer layer of a virus
Can be capsid (naked)
Enveloped
and enveloped have VAPs (viral attachment proteins)
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True/False: VAPs can attach to a capsid virus
FALSE: VAPS are embedded in the envelope of the virus and has no way of binding to the capsid
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Capsid Shape types
Spherical
icosahedral
filamentous
brick shaped
bullet shaped
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icosahedron
2 vertices, 20 faces, and 30 sides.
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What are the key differences between naked capsid viruses and enveloped viruses?
Naked capsid viruses are typically smaller and simpler in structure than enveloped viruses. They are also more resistant to environmental factors, such as heat and drying. Enveloped viruses are typically larger and more complex in structure than naked capsid viruses. They are also more susceptible to environmental factors, such as heat and drying.
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Positive-sense RNA (+RNA)
Positive-sense RNA refers to single-stranded RNA that can serve as mRNA (messenger RNA). In the context of viruses, positive-sense RNA viruses have genomes that can be directly translated into viral proteins by the host cell's ribosomes. Examples of +RNA viruses include the common cold viruses (rhinoviruses) and many other RNA viruses.
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Negative-sense RNA (-RNA):
Negative-sense RNA refers to single-stranded RNA that is complementary to the mRNA and cannot be directly translated into proteins. These viruses need to first transcribe their RNA into a complementary +RNA before protein synthesis can occur. Examples of -RNA viruses include the Ebola virus and influenza virus.
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+/- RNA (Ambisense RNA
Ambisense RNA refers to a type of genome found in some viruses that contains both positive-sense and negative-sense regions within the same genome. This means that some parts of the RNA can be directly translated into proteins (positive-sense), while other regions need to be transcribed into +RNA before translation can occur (negative-sense).
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+RNA via DNA (Retroviruses):
Retroviruses, like HIV, start with a positive-sense single-stranded RNA as their genetic material. When they infect a host cell, they use an enzyme called reverse transcriptase to change this RNA into DNA. This DNA is then inserted into the host cell's own DNA. This integrated DNA, called a provirus, acts like a recipe for making more RNA, allowing the virus to reproduce and multiply inside the host cell. This is how HIV and other retroviruses replicate in the body.
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DNA Viruses:
Classified by
Enveloped
Naked
Are more complicated in terms of function
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Viral Replication
Virus attaches to cell membrane (generally)
Phagocytized and brought into cell
Enveloped virus is uncoated and DNA/RNA is released
Replication and Translation occurs with viral DNA and structural proteins in cell
Assembly of virion - then is released
Varies depending on type of virus
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Explain the steps to viral replication
The process of a virus infecting a host cell typically follows a series of steps. It begins with the virus attaching to the cell membrane by binding to specific receptors. Once attached, the virus is often internalized into the cell through processes like phagocytosis or endocytosis. Inside the cell, the virus undergoes uncoating, where its protective protein coat is removed, exposing the viral genetic material. This genetic material is then replicated, transcribed into RNA or DNA, and translated into viral proteins using the host cell's machinery. These proteins are essential for the assembly of new virus particles within the host cell. Finally, the newly formed virions are released from the cell, allowing them to infect other cells and propagate the infection. The exact details of these steps can vary among different viruses, but this general process is a fundamental outline of viral infection and replication within host cells.
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Productive Viruses
Can lyse the infected cell
The term "productive virus" is often used to describe viruses that complete their replication cycle within the host cell, leading to the production of new virus particles (virions) that are released through cell lysis.
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Lysogenic Infection:
Non-productive:
Instead of actively replicating and producing new virions, the virus remains relatively dormant within the host cell. It doesn't lead to the immediate production of a large number of new virus particles. The integrated viral genome can persist in the host cell, and the cell continues to divide with the viral DNA.
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Oncogenic Transformation:
Some viruses, known as oncoviruses, have the potential to cause oncogenic (cancerous) transformation of the host cell. These viruses can introduce changes in the host cell's genetic material that promote uncontrolled cell growth and can ultimately lead to the development of cancer.
Outcome: The focus of these viruses is not primarily on actively replicating and producing virions but on influencing the host cell's behavior in ways that can result in cancer. This is a long-term health consequence of viral infection.
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Persistent Infections:
Description: In persistent non-productive infections, the virus can establish latent or chronic infections within the host cell.
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Latent Infection:
During latency, the virus remains within the host cell but does not actively produce new virions. It can periodically reactivate, leading to the production of new virus particles.
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Chronic Infection:
In chronic infections, the virus continuously replicates at a low level over an extended period without causing acute symptoms. Chronic infections can have long-term effects on the host's health, even though they may not lead to the massive production of virions.
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Cells can be
Permissive / non-permissive
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Permissive
Description: Permissive cells are those that allow viral replication or integration. They provide a suitable environment for the virus to complete its replication cycle and produce new virus particles (virions).
Outcome: The virus can replicate, assemble new virions, and ultimately, release them from the permissive cells.
(I am victim blaming these cells)
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Non-Permissive Cells:
Description: Non-permissive cells are not conducive to viral replication. While they may not allow viral replication, some non-permissive cells can still be transformative.
Outcome: The virus is unable to replicate within non-permissive cells, but in some cases, viral proteins or factors may influence the host cell's behavior in ways that promote transformation, which can lead to uncontrolled cell growth or other cellular changes.
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Abortive Cells:
Description: Abortive cells are incapable of supporting viral replication. In these cells, there is no successful replication of the virus, and the viral infection leads to cell death.
Outcome: The virus does not complete its replication cycle within abortive cells, and the cells ultimately die as a result of the viral infection.
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Viral Attachment Proteins (VAPs):
These are viral proteins or molecules that interact with specific receptors on the surface of host cells, allowing the virus to recognize and attach to the host cell.
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Host Range:
Refers to the range of different host species or cell types that a virus can infect. Viruses have varying host ranges.
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Tissue Tropism:
Tissue tropism refers to a virus's preference for infecting specific types of tissues or cells within a host organism. Some viruses have a broad tissue tropism, while others are more specific.
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Uncoating
Remove Coat: After entering the host cell, the virus must uncoat, which means removing its protective protein coat or capsid to release the viral genetic material.
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Synthesis:
Early Gene Products: These are non-structural proteins synthesized by the virus that are often involved in replication and other processes necessary for the virus's life cycle within the host cell.
Late Gene Products: Late gene products include structural proteins, such as those required for the assembly of new virus particles.
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Direct Membrane Fusion:
Virus attaches to cell membrane, the virus membrane will fuses with the plasma membrane, opens up the virus and release of viral material into the cell.
FUSION!
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What virus type is associated with a direct membrane fusion mechanism?
Enveloped.
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Can a naked virus come in through direct membrane fusion?
No, they typically do not use direct membrane fusion as their primary mechanism of entry into host cells
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Viropexis mechanism:
Virus attaches to the cell membrane, is entered into the cell inside a vesicle (made from the cell's plasma membrane) & enters into the cell where the pH will drop (which triggers a release of viral genome) & then to uncoat, the viral particle will remove its protein coat/capsid which allows the nucleocapsid to be released into the cytoplasm
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Can an enveloped virus enter through viroplexis
Yes
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Monocistronic RNA rule
Eukaryotic messenger RNA (mRNA) molecules typically encode a single protein product & only have a single protein-coding region active at a time.
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What can a virus do to follow this rule?
They often generate mRNA through splicing, a process where PRECURSOR RNAs containing MANY genes are processed by nuclear splicing enzymes to create separate monocistronic mRNA molecules for each gene.
Cheat the system by following the system baybee
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First method to follow the rule: Segmented RNA Genome
The simplest strategy: the mRNA transcribed from a given segment already constitutes a monocistronic mRNA.
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Third method to follow the rule: Negative Sense RNA
Since negative-sense RNA has to be converted into positive-sense RNA, RNA-dependent RNA polymerase (RdRp) will transcribe at the start of a gene and end transcription at the end of ONE gene. This will repeat until there are many positive-sense RNA strands, each containing one gene, which can then be translated into proteins
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Fourth method:
The positive-strand RNA genome has one ribosome binding site, which initiates translation near the 5' end.
Translated into a polyprotien which is then cleaved into several protein parts by proteolytic cleavages. Each protein product is derived from its own region of the polyprotein, effectively behaving as if it had its own mRNA.
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All viral replication depends on the production of __
mRNA
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Protein Synthesis
Protein synthesis in viruses requires the utilization of host cell ribosomes, transfer RNA (tRNA), and post-translational machinery.
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At the Ribosome
Production of Giant Polyprotein: Some viruses produce a single, large polyprotein that spans the entire viral genome. This polyprotein contains multiple protein-coding regions.
Production of Smaller Polypeptides: The giant polyprotein is subsequently cleaved into smaller polypeptides by proteases, resulting in individual protein products
Production: of individual proteins
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Achieving Preferential Translation: Selfish mechanism
Viruses may use various strategies to ensure the preferential translation of viral mRNA, allowing viral protein synthesis to take precedence over host cell proteins.
This can happen by:
blocking host DNA and mRNA from forming & degrading them
Decreasing Cellular Transcript Access/Concentration
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Assembly
Recognition Sequences: Viruses use specific recognition sequences to facilitate interactions between viral proteins, between viral proteins and nucleic acids, and between viral proteins and cellular membranes. These interactions are critical for the assembly of new virus particles.
Budding from the Plasma Membrane: In some cases, viruses utilize budding to exit the host cell. This process involves the insertion of viral membrane proteins (such as spike proteins) into the host cell's plasma membrane. The budding process allows new virus particles to form and be released from the cell's surface.
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Modes of Release
Buds through the plasma membrane
Budding Through Endoplasmic
Reticulum (ER)/Golgi:
Some viruses may remain within intracellular vesicles or compartments after budding, which can include ER and Golgi vesicles.
Passing Through ER and Transported to Surface (Endosomes): Certain viruses pass through the ER and are transported to the cell surface via endosomes. This mechanism allows for the eventual release of the viruses from the cell.
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Viral Budding
Virus will express spikes onto the infected cell membrane, and the matrix proteins will attract the nucleocapsid (new virus) to the cell membrane and is then removed from the cell, with a cell membrane surrounding the virus.
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DNA dependent, RNA polymerase
Produces mRNA
Utilized by DNA viruses
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DNA dependent, DNA polymerase
Viral DNA is replicated by viral DNA polymerase
Utilized by DNA viruses
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RNA Viruses (+)
RNA viruses begin translation as soon as the genome is uncoated
Contains the gene for viral polymerase to copy the genome for replication
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RNA-dependent, RNA polymerase
The RdRp also transcribes the viral RNA into mRNA, which can be used for translation into viral proteins.
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(-) RNA viruses
Must encode for a RNA-dependent RNA polymerase (RdRp) to transcribe the negative strand RNA into positive strand. The positive strand is then used to translate into proteins
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Parental (Wild-Type):
This refers to the original, unmutated form of a virus. It serves as a reference point for studying and comparing mutant viruses.
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Mutants (Change in Coding Sequences)
Mutant viruses have undergone genetic changes or mutations, typically in their coding sequences, which can affect their properties and behaviors.
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Lethal Mutations
Lethal Mutations: Mutations that render the virus nonviable or incapable of replicating are referred to as lethal mutations. These mutations can be detrimental to the virus.
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Deletion Mutations
These mutants have specific portions of their genetic material (nucleotide sequences) deleted. This deletion can result in loss of certain viral functions or proteins.
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Plaque Mutants
Plaques are clear zones that form on a lawn of host cells when viruses infect and kill the cells. Plaque mutants are viruses with mutations that affect the formation or appearance of plaques. These mutants are often used in virology research.
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Host Range Mutants:
Some mutants have altered host range, meaning they can infect a different range of host organisms than the wild-type virus.
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Attenuated Mutant
Attenuation refers to the reduction of a virus's virulence or ability to cause disease. Attenuated mutants are viruses with mutations that make them less pathogenic compared to the wild-type virus. They are often used in vaccine development to provide protection without causing illness.
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Conditional Mutants
Conditional mutants have mutations that affect the virus's behavior under specific conditions. For example, they may only replicate or express certain genes at certain temperatures or in the presence of specific factors.
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Antigenic Drift
Point mutations are tiny changes in a virus's genetic code, and they often happen because the virus's copying machinery isn't very good at proofreading. Over time, as the virus multiplies, these small errors can add up and lead to changes in the building blocks of the virus. These changes can cause the virus to look a little different to our immune system.
When this happens, our immune system may not recognize the virus as easily, allowing it to escape the immune defenses we've built up from previous encounters. This is why some viruses, like the flu, keep changing slightly, making it harder to develop vaccines that work perfectly against them.
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Antigenic Shift
Imagine a human flu virus and a swine flu virus infecting a pig's lung cell. As these viruses replicate, their genetic material, which is divided into segments, mixes in the same cell, leading to a major reshuffling of these genetic segments. The newly synthesized RNA segments can come from both viruses, creating various combinations. This process can give rise to parental virus types, as well as entirely new hybrid viruses with unique genetic compositions. & new strands of viruses.
this is scary.
