Micro Basic Virology

_______ is used by the virus to get out of the host cell after it replicates.

*Neuraminidase* is used by the virus to get out of the host cell after it replicates.

What is involved in the maturation process?

1. *Coalescing* -bringing different components together 2. *Assembly* of the viral particles, which usually occurs in the cytoplasm 3. Eventually, the *release* of the virus

How are prion diseases transmitted?

1. *Direct inoculation into the CNS* 2. *Percutaneous exposure* -this is actually how Kuru is transmitted--through handling the brains (not eating them as was previously thought) 3. *Ingestion* -this is how cows acquire mad cow disease --apparently it's still up in the air as to whether humans can acquire mad cow from eating contaminated beef.

POE replication and spread to nearby cells (beyond the adjacent cells)

Can spread via: -liquid spaces -the lymphatics -mucus membranes --this is especially seen in the respiratory tract

In the body, what is the most important antiviral factor?

Cell-mediated immunity -i.e. cytotoxic T cells --kill infected self-cells

In a(n) _____ infection, progeny will continue to be made for long periods of time, but at reduced numbers.

Chronic You don't see as many progeny being produced per cell as you do during an acute infection.

Transcription results in the early and late production of viral mRNA. Early transcription will be devoted to making mRNA for...

Early transcription will be devoted to making mRNA for *regulatory proteins and proteins used later on for DNA replication*.

The general (active) process for how a virus translocates across the cell membrane is called ________.

Endocytosis This is an active process where the viruses are taken up and put in a vacuole.

_____ virus attaches to acetyl-choline

Rabies

Reverse Transcriptase is an enzyme that can create ____ from ____.

Reverse Transcriptase is an enzyme that can create *DNA* from *RNA*.

The ______ is the most common cause of infant diarrhea, and young children worldwide.

Rotavirus (Reoviridae family)

The term used to describe a virus exiting the host (not the host cell; the entire host organism) is _________.

Shedding The deeper in the target cell is, the more interesting the ways they get out of the body.

How does the virus uncoat?

Since the virus doesn't have any enzymes, the host actually removes the lipid envelope and the capsid and releases the virus.

What kinds of compounds do the spikes on a viral envelope contain?

Some influenza virus spikes contain hemagglutinin. -hemagglutinin causes the agglutination of RBCs. neuraminidase is also found in the envelope

What happens after the virus is uncoated?

Transcription and translation of the viral nucleic acids. (i.e. the synthesis step).

Transcription results in the early and late production of viral _____.

Transcription results in the early and late production of viral *mRNA*.

True or False: The host will make the enzymes needed for both the RNA dependent RNA polymerase and the DNA dependent RNA polymerase.

True

True or False: Most viruses that cause illness are exogenous.

True (i.e. you get them from somebody else)

True or False: For skin viruses like herpes, the portal of entry is also the primary target.

True Although it's the neural tissue that it really goes after.

True or False: Some viruses can use multiple receptor sites on a host cell to attach.

True HIV will bind to a number of chemokine binding sites on CD4 cells.

True or False: Disease only happens in a viral infection if the virus has replicated sufficiently to damage essential cells, which don't grow back very quickly.

True In addition to actually damaging cells, there is a release of toxic products from infected tissues, which is part of the inflammatory response.

True or False: The viral budding process can eventually kill the host cell.

True It just takes longer than the explosive, lysis exit of the naked viruses. Note that during the budding process, the virus is actually taking a piece of the host cell membrane with it and it becomes part of the viral envelope.

True or False: Generally, during chronic infection, the progeny are initially released without harm to the host.

True It's only after a long period of time that you would see harm to the host.

True or False: (-) sense ssRNA is not infectious.

True Meaning that a (-) ssRNA strand released into the cell can't do anything by itself. The (-) ssRNA strand is therefore used as a template to produce an mRNA, which codes for virus protein. The host uses the (-) ssRNA to make mRNA.

True or False: Selection pressure favors the transmission of less virulent viruses in terms of dominance.

True Most of the viruses that make it for longer periods of time are the less virulent strains. It's not good for a pathogen to kill its host.

True or False: Prodromal symptoms are due to viral infection and replication at the POE.

True Prodromal = early symptom (or set of symptoms) that might indicate the start of a disease before specific symptoms occur. Prodromal symptoms precede the attack on the target tissue. They are very nonspecific.

True or False: Only cells that contain receptors for the virus are infected.

True Receptors are specific

True or False: Budding is a process used by some enveloped viruses to exit the nucleus of a host cell.

True The nucleus has a nuclear membrane and some viruses exit the nucleus via the budding process. -Recall that some viruses go through the maturation process in the nucleus, but it is more common for virus maturation to occur in the cytoplasm. ALL enveloped viruses use the budding process to exit the host cell at the plasma membrane. -Thus if the virus exits the nucleus via the budding process, it will also exit the plasma membrane via the same budding process.

True or False: The sequences that make up the two prion proteins (normal and abnormal) are identical.

True The two proteins only differ by how they are folded. -Thus the problem arises in the tertiary (and quaternary?) structures of the prions. The prions are folded in such a way that they resist normal digestion by proteolytic enzymes and they don't fall apart at high temperatures.

The release of enveloped viral progeny from the host cell is done more slowly through a _____ process.

budding

The capsid is made up of subunits called _________.

capsomeres

Hepatitis B virus is an example of a(n) ______ infection.

chronic

DNA virus replication, transcription and assembly will generally occur in the...

cytoplasm in organelles....unless it's in the nucleus.

Viruses that are constantly living within us are known as ________.

endogenous -endogenous viruses can be re-activated to an infectious form (e.g. herpes and HIV)

The envelope surrounds the _______.

nucleocapsid (so I guess the envelope is the outermost structure...)

How are latent infections re-activated?

some kind of stress

Virus shedding also takes place at the ______.

target tissue

The passive process for the translocation of a virus across the cell membrane is called ______.

viropexis

How does a (-) sense ssRNA virus make more viral progeny?

In order to get more (-) ssRNA viral progeny, a complementary (+) ssRNA strand intermediate needs to be made. The (+) ssRNA strand will be used as the template for making more (-) ssRNA viral progeny.

The ______ is the capsid and the nucleic acid that lies within.

nucleocapsid

___ sense ssRNA is infectious.

(+) this is because it's all ready to go...it's already mRNA

___ sense ssRNA is used as a template to create mRNA

(-)

An enzyme that is going to be used for making specific viral DNAs is going to be a

*DNA dependent RNA polymerase*

How does a (+) sense ssRNA virus make more viral progeny?

*It needs to synthesize a complementary (-) sense ssRNA strand.* -this (-) strand serves as the *template* for more (+) progeny strands. In terms of protein synthesis, (+) ssRNA is already acting as it's own mRNA; it's already acting on the machinery to produce early and late protein synthesis for the virus.

How is neuraminidase used in the viral life cycle?

*Neuraminidase is used by the virus to get out of the host cell after it replicates*. When *influenza* virus replicates, it *attaches to the interior cell surface using hemagglutinin*, a molecule found on the surface of the virus that *binds to sialic acid groups*. Sialic acids are found on various glycoproteins at the host cell surface, and the virus exploits these groups to bind the host cell. In order for the virus to be released from the cell, *neuraminidase must enzymatically cleave the sialic acid groups from host glycoproteins*. Since the cleavage of the sialic groups is an integral part of influenza replication, blocking the function of neuraminidase with neuraminidase inhibitors is an effective way to treat influenza.

___ sense ssRNA can act as mRNA for translation.

(+)

What are the basic steps of viral pathogenesis (i.e. infection)?

1. *Infect at Portal of Entry* (the initial site where they get into the body) -most viruses have 1 POE -the portal of entry may or may not be the primary target --therefore, depending on the virus, it may need to travel a significant distance from where the POE is. 2. *Replication at Portal of Entry* -in most cases you have immediate replication at portal of entry -a single viral particle can't do much, so this replication is important 3. *Dissemination* around the POE as well as to the Principal Target site where it multiplies. -Generally (not always), it's at the target site where you start to see signs and symptoms that are associated with the specific viral disease. -*Dissemination includes Replication & Shedding* -shedding = virus gets out of the host. --You can shed virus asymptomatically.

Which host defense factors play a role in viral infections?

1. *Innate* -inflammation -production of cytokines -production of interferons -NK cells 2. *Cell-mediated (T-cells)* -kills infected self-cells 3. *Humoral (Ab)* -not much of a role in stopping an acute infection. -However, they do play a role in preventing future infections. 4. *Interferons* (Anti-viral) -inhibit some portion of virus replication *nonspecifically* --this can be done either directly (by the interferon itself) or indirectly (by a protein produced by interferon). -gamma-interferon is frequently used as therapy in viral infections.

What are the determining factors for tissue tropism in terms of viral infection?

1. *Presence of specific receptor sites* that the virus needs to attach -viruses have selected these sites 2. *Particular cell transcription factors* that recognize specific viral promoters. -i.e. that particular host's ability to support the replication of the virus. 3. *Physical barriers* 4. *Physical parameters* such as the host cell's: -temperature -pH -O2 tension -enzymes present --e.g. rhinoviruses grow best at slightly reduced temperatures and slightly reduced pH (which is why they are found in the upper respiratory system)

What are the main functions of a capsid?

1. *Protection* -The nucleic acid (either RNA or DNA) does not do well in the environment for very long. 2. On viruses that don't have an envelope (*naked* viruses), the *capsid also contains specific receptor sites* for their specific host tissue. -Tissue tropism is incredibly important for viruses. *Not all viruses will grow in all cells.* 3. The capsid may contain *other components* (besides receptor sites) *which allow the virus to enter its host cell* (or be taken up by the host cell).

Besides RNA and DNA polymerase, what are some other virus associated, enzymes (these may be host-derived)

1. *Protein kinase* -a kinase enzyme that modifies other proteins by chemically *adding phosphate groups* to them (phosphorylation). 2. *Phosphatases* -an enzyme that *removes a phosphate group* from its substrate. -This action is directly opposite to that of phosphorylases and kinases, which attach phosphate groups to their substrates by using energetic molecules like ATP. 3. *Ribonucleases* -Ribonuclease (commonly abbreviated *RNase*) is a type of nuclease that catalyzes the *degradation of RNA* into smaller components.

What are some Factors Affecting Pathogenesis (i.e. how pathogenic a virus is going to be) ?

1. *Target Accessibility* -are there physical barriers between the POE and the target? (i.e. mucus membranes and tissues) -What's the distance from the POE to the target site? -What are the natural defense mechanisms and what are their competencies? 2. *Target Cell Susceptibility* -there are some cells that will intrinsically not replicate certain viruses. -Are there corresponding attachment sites on the inside and the outside? -Do the target cells have the right intracellular environment for replication? 3. *Virus Susceptibility to Host Defenses*

The most frequent exits (shedding) for viruses are from....

1. *Upper respiratory* -talking, coughing, sneezing 2. *The GI tract*

The *Indirect damage* caused by viruses to the host cell is a result of...

1. *When viral genetic material gets integrated into the host cell genome*. -As mentioned before, this can lead to mutations and malignancies. 2. The *general inflammatory response* from the host's immune system.

What are the 4 outcomes of viral infection?

1. Acute infection 2. Latent infection 3. Chronic Infection 4. Nothing (immune system gets rid of it. May have subclinical infection for a time)

What are the general steps of the virus replication cycle?

1. Attachment (adsorption) 2. Penetration (translocation) 3. Uncoating 4. Transcription 5. Macromolecular synthesis (translation) 6. Assembly 7. Release

What are two ways that the virus obtains it envelope?

1. It's made by the host machinery 2. It's ripped off of the host membrane when the virus exits the host in a process called budding.

What is a typical viral envelope composed of?

1. Lipids 2. glycoproteins

What are the two kinds of ssRNA viruses?

1. SS (+) sense/polarity RNA 2. SS (-) sense/polarity RNA

What are some important conditions that must be met in order for the virus to attach (adsorb) to the host cell?

1. The *appropriate ionic conditions* 2. The *appropriate pH* 3. The *appropriate temperature*

While the naked viruses are growing inside the host cell and preparing for release, they're acting on the host cell in certain ways. What sorts of things do they do to the host cell?

1. They're *inhibiting the normal metabolic pathways* of the host cell 2. They're *causing disintegration* of the host cell's *cellular cytoskeleton* 3. There's *breakdown* and *alteration* of the host *cell membranes* Basically, these cells are being primed to explode.

Dissemination from POE What are the two ways?

1. Viremic spread 2. Neural spread (less common)

POE Routes

1. eat (GI) -fecal-oral 2. inhale (respiratory) -droplets (small and large) -viruses that don't last long in the environment must be transmitted over short distances. -viruses that are airborne, can last for a longer period of time. 3. touch (direct contact) -contact with lesions -blood and body fluids -insect bites (arthropod borne)

The variables that influence the outcome (i.e. whether it will be a subclinical infection, a mild infection, or a severe infection) are usually dependent on...

1. the virus dose in the original sample 2. The infectivity of the virus 3. Its virulence 4. The location where the implantation took place

There are ____ virus-binding sites on each eukaryotic cell.

10^5

A(n) _____ infection is the result of a lot of viral replication over a short period of time.

Acute Eventually the immune system catches up with this infection and either eliminates it or you die.

Which virus family contains the first 2 viruses that were shown to be carcinogenic?

Adenoviridae

What is a prion?

An abnormally folded protein structure. -The damage that occurs as a result of the abnormal folding and the resistance of these structures to any kind of degradation is what is attributed to the cause of the associated signs and symptoms. Prions have been held responsible for a number of degenerative brain diseases, including mad cow disease, Creutzfeldt-Jakob disease, fatal familial insomnia, kuru, and an unusual form of hereditary dementia known as Gertsmann-Straeussler-Scheinker disease. -It's thought that the accumulation of this non-biodegradable material and the aggregation of the PrP^Sc's in the brain is what causes the neurological degeneration seen in these disease states. *A prion is neither bacterial nor fungal nor viral and contains no genetic material*.

An enzyme that is going to be used for making specific viral RNAs is going to be a....

An enzyme that is going to be used for making specific viral RNAs is going to be a *RNA dependent RNA polymerase*

Most human viral pathogens are _________ viruses.

Most human viral pathogens are *single stranded RNA* viruses.

True or False: In animal viruses, the nucleic acid (RNA or DNA) tends to be circular.

False Animal viruses are more linear. Bacterial viruses contain circular (RNA or DNA).

True or False: Although the effects of prion diseases on the brain are very deleterious, they tend to progress slowly, which often contributes to the late diagnosis of a prion disease by a clinician.

False Prion diseases progress very rapidly

True or False: The attachment of a virus to the host cell surface requires ATP.

False Recall: Viruses have no way to make or store energy.

True or False: Generally, it's at the POE where you start to see signs and symptoms that are associated with the specific viral disease.

False Specific signs & symptoms are due to infection of the target site, which is not always the same as the POE.

True or False: Some animal viruses have a mechanism for injecting their genetic material into the cell upon attachment.

False That is a mechanism used by bacteriophage, but animal viruses must enter the cell after attachment. This means that if you can stop the animal virus from getting into the cell then you can stop the infection.

True or False: The GI symptoms associated with the flu are a direct result of the influenza virus on the target tissue.

False The target for the influenza virus is the respiratory system. The GI symptoms that are associated with the flu are a result of your own immune system.

True or False: Regardless of whether the POE is the target or not, there will be symptoms of viral disease at the POE.

False There may or may not be symptoms at the POE -the virus may be killing expendable cells at the POE, or you may get prodromal symptoms, but not the disease itself.

True or False: Host cells that viruses attach to usually have abnormal receptors which are specific for viral attachment.

False These receptor sites weren't specifically made by the cell for viruses. Over time, viruses have adapted to particular receptor sites that the host cell uses for something else.

Fomite viruses tend to be very environmentally ________.

Hardy This is typical of GI viruses

In prion disease, it's thought that the accumulation of this ________ material and the _______ of the PrP^Sc's in the brain is what causes the neurological degeneration seen in these disease states.

In prion disease, it's thought that the accumulation of this *non-biodegradable* material and the *aggregation* of the PrP^Sc's in the brain is what causes the neurological degeneration seen in these disease states.

How do viruses evade the immune system?

In the case of HIV, it replicates in macrophages and T lymphocytes, which are the very cells that are used to kill them. Other viruses can avoid the action of the T-cells by blocking the antigen processing. Others can express glycopeptides that interfere with interferon action.

In the case of a (+)ssRNA animal virus, the (+)ssRNA acts as mRNA for synthesis of viral _____ and the ______ for new viruses.

In the case of a (+)ssRNA animal virus, the (+)ssRNA acts as mRNA for synthesis of viral *proteins* and the *genome* for new viruses.

In the case of a (-)ssRNA animal virus, the (+)ssRNA acts as mRNA for synthesis of viral _____ and acts as a ______ for the synthesis of the (-)ssRNA ______ for new viruses.

In the case of a (-)ssRNA animal virus, the (+)ssRNA acts as mRNA for synthesis of viral *proteins* and acts as a *template* for the synthesis of the (-)ssRNA *genome* for new viruses.

What is the significance of segmented RNA viruses such as influenza?

Influenza type A has 8 segments; this is why it stays ahead of you in terms of vaccines, because its constantly resorting (you have to get a new one every year).

What is tissue tropism in terms of viral infection?

It refers to the fact that *viruses have affinity for specific host tissues*

The first thing that needs to happen in the synthesis step is the virus needs to create viral mRNA. How is this done with a DNA virus?

It's very much like any DNA synthesis. The DNA makes mRNA -the host is making the mRNA using the viral nucleic acid as the template. -Transcription results in the early and late production of viral mRNA. --Early will be things like regulatory proteins and proteins used later on for DNA replication. --Late protein synthesis will cover virus capsid. Transcription and translation eventually yields viral protein and the production of viral progeny DNA or RNA.

Transcription results in the early and late production of viral mRNA. Late transcription will be devoted to making mRNA for ...

Late transcription will be devoted to making mRNA for *the virus capsid*.

The ______ of virus to its host cell is random.

The *adsorption* of virus to its host cell is random. -they were just in the right place at the right time -they found the host and the right site on the host However, the *attachment is specific*! -they attach to a specific host cell receptor site. --*sometimes there is more than one specific receptor site*. -The host cell receptor site is keyed by a specific receptor site on the viral surface. --it doesn't matter if it's a naked virus or one with an envelope.

The _____ is simply an accumulation of proteins that encloses the nucleic acid.

The *capsid* is simply an accumulation of proteins that encloses the nucleic acid.

The ______ prion protein is designated as PrP^c, whereas the _______ prion protein is designated as PrP^Sc.

The *normal* prion protein is designated as PrP^c, whereas the *abnormal* prion protein is designated as PrP^Sc.

Not all viruses will propagate in all cells. What makes viruses so specialized?

The *receptor sites* that they have in their capsid, or in their envelope (if they have one).

The H of H1N1 refers to the specific type of _________ and the N refers to __________.

The H of H1N1 refers to the specific type of *hemagglutinin* and the N refers to *neuraminidase*. The number refers to the type. -H1 = hemagglutinin type 1 -N1 = neuraminidase type 1

What is the outermost structure of a virus?

The capsid

The classification of viruses has shifted from symptoms, or how it was transmitted, to....

The classification of viruses has shifted from symptoms, or how it was transmitted, to *the type and structure of the genome* -is it DNA or RNA? -is it double stranded or single stranded? -how big is it? -what's the symmetry of the capsid? -does it have an envelope or is it naked? -how does it replicate? --some viruses replicate entirely in the host cytoplasm, whereas others replicate in the nucleus. --some do both; the protein capsids will be synthesized in the cytoplasm, and their nucleic acid is synthesized in the nucleus.

The *Direct damage* caused by viruses to the host cell is a result of...

The damage caused by viruses to the host cell is a result of *disruption of normal host cell synthetic pathways*. -Virus replication will steal many of the macromolecular components/machinery as well as the energy (ATP) that cell would normally use for making its own stuff. -There is also competition for the cell's ribosomes by the viral mRNAs. --interestingly, viral mRNAs seem to have dominance (increased affinity) for the ribosomes over the native host cell mRNA. -Also competition for promoters and transcriptional enhancers, such as RNA polymerase; these yet again, get dedicated to the production of virus progeny instead of host cell components. Unlike bacteria, viruses don't: -deprive the host cell of nutrients -release toxins

Besides icosahedral, what's another common capsid configuration?

The helical configuration long stringy viruses like tobacco mosaic virus

What is the most common capsid configuration?

The icosahedral configuration.

What is the drawback for viral detection kits?

The sensitivity of the test -i.e. how many viruses do you need in order to show a positive result?

How does HIV cross the cell membrane?

The viral envelope fuses with the cell membrane, goes through several other steps and then is taken into the membrane. The virus actually briefly becomes part of the membrane.

POE replication and spread via cell-to-cell

The virus can spread to adjacent cells either extracellularly or intracellularly. -contributes to local infection at the POE

Neural dissemination from POE

The virus spreads through axons and dendrites. -This is advantageous for the virus because they are shielded from Ab, the inflammatory response, and antivirals that can't cross the blood brain barrier. -E.g. happens in herpes & rabies Interesting fact: Rabies has to make its way to the CNS, which is its target, and then make its way to the salivary glands where it is shed. -you get rabies from a bite

If the POE is also the target...

The virus will go through continued replication and shedding right at that entry site.

Transcription and translation eventually yields viral ____ and the production of viral _____ DNA or RNA.

Transcription and translation eventually yields viral *protein* and the production of viral *progeny* DNA or RNA.

True or False: Prions are transmissible and infectious agents.

True Their infectious abilities come from the fact that the abnormal prions can induce other normal prions to fold abnormally. When you introduce an abnormal prion protein to a normal one, you end up with amplification of the abnormal prion because the normals are getting converted to the abnormals. PrP^c --> PrP^Sc -The abnormal one is serving as a template for the creation of more abnormally folded prion proteins.

True or False: Some viruses contain enzymes in their envelope.

True There may be virus associated enzymes or at least virus associated enzyme activity. Some of which may be carried by the virus, many of which are dictated by the virus for the host cell to make.

True or False: There is no inflammatory response or Ab response to a PrP^Sc

True They are self proteins, they are just misfolded.

True or False: Typically, in individuals who are immunocompetent, the viremic stage is short-lived.

True This is because your immune system (i.e. interferons), is sufficient to kill the virus in the bloodstream. -unfortunately it also doesn't take very long for the virus to reach its site via the bloodstream. --so they can still find their site.

True or False: 50% or more of human viral infections are subclinical.

True This means that your immune system is working to eliminate the signs and symptoms of the virus.

Once the virus enters the cell, what is the next step?

Uncoating Viral nucleic acid is released from the capsid and/or envelope

What are the arthropod borne (mosquitos, ticks, lice, etc.) virus families?

Used to be one group called arbovirus, but now they are separated. 1. *Togaviridae* -WEE, EEE, Rubella 2. *Flaviviridae* -Yellow Fever, West Nile, Dengue, Hepatitis C 3. *Bunyaviridae* -Hanta virus, Crimean-Congo hemorrhagic fever

Viral groups are based on _______ structure.

Viral groups are based on *groups* structure. Genomic sequences are being used to decipher exactly what viruses are related. This has shown that not all hepatitis viruses are the same...in fact they aren't even in the same group.

_____ is the principle mode of dissemination for viruses.

Viremia

What is viremia?

Viremia = The presence of virus in the blood. -but generally the virus does not replicate in the blood. -Replication occurs at the POE, and then the progeny diffuse through the lymphatics and into the bloodstream, and then they finally release into their target tissue. -In most cases, once the virus is in the bloodstream, they can pretty much access the target no matter where it is. -When they are at the target organ, they will replicate again. --If they kill a sufficient number of cells at the target organ, you will see the typical signs and symptoms of the viral disease. --Virus shedding also takes place at the target tissue.

According to Dr. Vaughn, there are 20 viral families. Within each family there are hundreds and hundreds of different ______. Within each species there are thousands of different _____.

Within each family there are hundreds and hundreds of different *species*. Within each species there are thousands of different *serotypes*.

What are some Diagnostic Considerations for viruses?

You want something that's fast and accurate. 1. Virus *antigen detection* kits -these are extremely popular -some of these work on the ELISA principal --others use lateral flow (an immunochromatographic assay) 2. *PCR* -detects the actual nucleic acid -This is the best way, but the downside is that it's expensive

A common characteristic of prion proteins is that they _______ into filaments.

aggregate This aggregation is directly related to the improper folding of the proteins. -recall that non-polar, hydrophobic residues aggregate together due to the entropy of water; this is known as the hydrophobic effect. According to Dr. Vaughn, the variability between normal and diseased prion proteins is only found in the alpha helix, but not in the beta-sheets. -However I don't think that is a true statement.

________ infections constitute the major source of transmission to other individuals.

inapparent (i.e. subclinical; no signs and symptoms) People who are infected but asymptomatic, will have an immunological response. -There are viruses that are multiplying in the individual.

During a(n) _____ infection, *progeny viruses are not produced*; the viral DNA will persist within the host cell.

latent Latent infection occurs with some DNA viruses, like herpes. -In the case of herpes, the viral DNA persists in the form of an extrachromosomal body. In latent viral infections, the viral DNA is immortalized because it replicates along with the host cell. -in some retroviruses this can lead to more serious consequences; because it is part of the host genome, there can be transformation of the host genome due to the extra bit of DNA, which can lead to malignancy.

The first thing that needs to happen in the synthesis step is the virus needs to create viral _____.

mRNA How this is done depends on the type of virus.

(+) sense and (-) sense are analogous to...

mirror images.

The release of _____ viral progeny from the host cell is spontaneous and explosive and causes lysis of the host cell.

naked (non-enveloped) You get these gigantic crystalline arrays of virus progeny particles that start to build up inside the host cell and are released upon lysis of the host cell. -500 to 1000 progeny are released upon lysis (Recall that some bacterial viruses are also released from their host cell via lysis)

Which virus is the largest (in size, not in number)

the smallpox virus (Poxviridae) (~300 nm) -same size as chlamydia.