Edit · MBS 326M Exam 3 Kim

what does Hepatitis A,B,C,D,E

failure in liver (cirrhosis)

is Rickettsia/Chlamydia a parasite

yes

does Rickettsia/Chlamydia (bacterial parasite) have ATP-generating metabolism

yes

Tissue tropism

tissue preference, range of tissue types a virus can infect

Difficulty in developing antiviral meds

Hard to discover

Have severe side effects

Viral genomes mutate faster than bacteria

Icosahedral capsids

Radial symmetry, based on icosahedron, a polyhedron with 20 identical triangular faced

where are viral envelopes derived from

(like herpesvirus) derived from host nuclear or endoplasmic reticulum membrane

how to spike proteins support virus structure

Spike proteins plug membrane onto capsid

Filamentous capsid

Helical symmetry

Helical tube around the genome

Generate flexible filament

filamentous capsid example

tobacco mosaic virus (TMV)

ebola virus

Amorphous/complex virus

No symmetrical form

Flexible core wall with genetic material

Viral envelope with spike protein

Amorphous/complex virus example

Vaccina virus and smallpox virus

What is another name for the Vaccinia Virus?

Cowpox virus

Who used the Vaccinia Virus to create the first successful vaccine?

Edward Jenner

What vaccine was developed from the Vaccinia Virus?

Smallpox vaccine

What is one use of the Vaccinia Virus in modern medicine?

Used as a genetic vector to develop vaccines against various animal diseases

Viral replication cycles

Host recognition and attachment

Genome entry

Assembly of progeny virions

Exit and transmission

viral replication: attachment- bacteriophage vs animal virus

bacteriophage- Tail fibers attach to cell wall proteins

animal virus- Attach to plasma membrane proteins and glycoproteins

viral replication: entry- bacteriophage vs animal virus

bacteriophage- Viral DNA injected into host cell

animal virus- Capsid enters by receptor-mediated endocytosis or fusion

viral replication: uncoating- bacteriophage vs animal virus

bacteriophage-N/A

animal virus- Enzymatic removal of capsid proteins

viral replication: biosynthesis- bacteriophage vs animal virus

bacteriophage-In cytoplasm (lysogeny possible)

animal virus- In nucleus (DNA viruses) or cytoplasm (RNA viruses) (Latency; cancer)

viral replication: release- bacteriophage vs animal virus

bacteriophage-Host cell is lysed

animal virus- Enveloped viruses bud out; nonenveloped viruses rupture the plasma membrane

Plaque assay (agar)

Bacteriophage infection forms plaques of lysed cells on a lawn of bacteria in Petri dish

bacteriophage growth curve

One-step growth curve

Multiplicity of Infection (MOI)

virions per every host cell infection. Ex: MOI of 5 means 5 viruses for every host cell

Eclipse period

undetectable in medium (0min-rise)

Rise period

phage particles start to appear (assembly phase)

Burst period

cell lysis complete

Animal virus culturing

Immortalized cell

Inoculated with viruses suspension

Viruses adhere to cells

Culture fluid is removed

Fluid replaced by a gelatin medium that holds bacteria and viruses in place

When host cell die, plaques observed

tenants of phage therapy

Also known as bacteriophage therapy, the use of bacteriophages to treat bacterial infections

Specificity

Safety; generally harmless to humans

Effectiveness; effective against antibiotic-resistant bacteria

Group 1 Pathway

dsDNA -> mRNA

Group 1 replication, translation, and transcription

Use host cell or own DNA polymerase; replicate within host cell nucleus

Transcription and translation via host cell RNA polymerase

Group 1 example

herpesvirus

Group 2 Pathway

ssDNA -> dsDNA -> mRNA

Group 2 replication, translation, and transcription

Use host cell DNA polymerase to create complementary strand and make dsDNA; replicate within host cell nucleus

Transcription and translation via host cell RNA polymerase

Group 2 example

Parvovirus

Group 3 Pathway

dsRNA -> RNA-dependent RNA- polymerase -> mRNA

Group 3 replication, translation, and transcription

Replicate in host cytoplasm

RdRp transcribes dsRNA into positive sense ssRNA (+ssRNA) which is read like mRNA via host ribosomes

Group 3 example

Rotavirus

Group 4 pathway

ssRNA (+) -> RNA-dependent RNA- polymerase -> mRNA

Group 4 replication, translation, and transcription

Genome replication: RdRp synthesizes complementary strand of +ssRNA to make -ssRNA which is used as template to make new +ssRNA

+ssRNA directly go to ribosomes for transcription and translation

Group 4 example

Coronavirus

Group 5 pathway

ssRNA (-) -> RNA-dependent RNA- polymerase -> mRNA -> ssRNA (-) for viral genome

Group 5 replication, translation, and transcription

Genome replication: RdRp synthesizes complementary strand of -ssRNA to make +ssRNA which is used as template to make new -ssRNA

Mechanism: RdRp transcribes -ssRNA to +ssRNA which can serve as mRNA for transcription and translation

Group 5 example

Influenza virus

Group 6 pathway

ssRNA (-) -> reverse transcriptase -> dsDNA -> mRNA

Group 6 replication, translation, and transcription

SsRNA (-) reverse transcribed into complementary dsDNA (cDNA) via viral reverse transcriptase

cDNA transported to nucleus and into host DNA via integrase

Genome replication: integrated viral DNA (provirus) is transcribed by host RNA polymerase

Provirus is transcribed into mRNA and translated by host ribosomes

what protein is used to transport cDNA into host nucleus

integrase

3 enzymes in capsid of HIV

reverse transcriptase, integrase, protease

Group 6 example

Retrovirus and HIV

Group 7 Pathway

dsDNA --> mRNA --> reverse transcriptase --> dsDNA for viral genome

Double stranded DNA with RNA intermediate

cccDNA formation

GROUP 7- dsDNA released into host nucleus and is converted into covalently double stranded closed circular DNA (cccDNA) by host cell enzyme (double circle DNA)

Group 7 replication, translation, and transcription

cccDNA transcribed into a +ssRNA known as pre-genomic RNA

viral reverse transcriptase converts pre-genomic RNA into partially dsDNA

cccDNA serves as template for transcription of viral mRNA by host RNA polymerase

what is pre-genomic RNA

cccDNA transcribed into a type of +ssRNA

What is the function of reverse transcriptase?

To use ssRNA to make ssDNA via RNA dependent DNA polymerase.

What enzyme is responsible for chopping off the ssRNA strand in reverse transcription?

RNase H.

what is used to make dsDNA from ssDNA?

Using DNA dependent DNA polymerase.

Antigenic drift

more minor and rapid mutations

New stains or virus via changes in genomic or minor changes in virus surface proteins

No longer recognized by antibodies

Antigenic Shift

major change and larger mutations

Resulting in chimeric virus

No longer recognized by antibodies

Can lead to pandemic due to rapid spread of new virus subtype

chimeric virus

Reassortment of genome segments (two virus infect host to create new virus)

Lead to highly virulent strains of a virus

Viral Evolution

Within a host: Evolve to infect different species

Herpes in horses and mice

Within a viral species population: strains evolve that vary in infectivity and virulence

Within an individual organism: Viruses evolve variants that resist therapeutic agents

how many adults does HPV affect?

80% of adults

which cancer is linked to HPV

cervical cancer

how does HPV spread

Strands are highly infectious via sexual contact

HPV prevention

Can be prevented by condoms and vaccination

HPV genome shape

Circular dsDNA

No envelope

8000 base pairs

Encoding eight genes; early genes are more important to take over host cell mechanisms than capsid protein coding genes (late genes)

E6 and E7 genes are viral oncogeneS

role of E6 and E7 genes in HPV

E6 and E7 genes are viral oncogenes

Where does HPV infect in the body?

Basal cells

What happens to HPV after it infects basal cells?

It remains dormant

What triggers HPV replication?

Keratinocytes differentiate

What is released when HPV infected cell shedding occurs?

HPV virions

What happens to HPV in the basal cells?

HPV integrates into the genome, lysogeny can lead to cancer

influenza capsid

No fixed capsid

influenza genome

(-) sense ssRNA

Eight chromosome segments

influenza Enveloped (spike proteins)

Hemagglutinin (HA): attachment via endocytosis

Neuraminidase (NA): exit via budding

how does Tamiflu work

inhibits neuraminidase (viral exit)

influenza antigenic SHIFT

"A" genome cause antigenic shift due to reassortment between human and avian strains with swine host

how does chronic HIV develop?

HIV titer increase and T-cell decline over time -> chronic HIV

when do most people check for HIV

Most people only enter clinic during clinical latency

What is the Baltimore classification of papillomaviruses?

Papillomaviruses fall into Group I of this system, which includes double-stranded DNA(dsDNA) viruses

How do overlapping genes affect viral replication

Viruses often have small genomes, so overlapping genes allow them to encode multipleproteins within a limited amount of genetic material. This efficient use of genome space iscrucial for viruses to pack all necessary information into their compact genomes

Why is the segmented genome important for the influenza virus

The segmented genome allows for genetic reassortment, which can lead to the emergence ofnew viral strains with different properties

Which steps in the HIV replication cycle are targeted by antiviral agents?

Antiviral agents target multiple steps in the HIV replication cycle, including binding, fusion,reverse transcription, integration, and protease activity.

How is HIV latency established?

HIV latency is established when the virus integrates its genetic material into the host cell'sDNA and enters a resting state. This often occurs in memory CD4+ T cells, which can persistfor long periods without dividing

Which of the following facts supports the argument that viruses are living

Some living pathogenic bacteria contain degenerate genomes and rely significantly on a host.

Culturing viruses is difficult because viruses

must be grown inside a living cell.

Sepsis

bacterial contamination

Asepsis

absence of significant contamination

Degerming

mechanical removal of microbes from a limited area

Commercial sterilization

killing Clostridium botulinum endospore from canned goods; kills all spores without altering the quality of food

Sterilization

destruction of ALL living cells, spores, and/or viruses

Disinfection

Removal of disease-causing microorganisms from inanimate surfaces, not necessarily sterilize

Sanitation

Reducing microbe numbers to "safe" levels, not necessarily sterilize

Cidal agents

lethal effects

static agents

Slow or stop metabolism or reproduction, but are not necessarily lethal

D-value

decimal reduction time, time required to kill 90% of cells

how does heat kill microorganisms

denature enzymes

Thermal death point (TDP)

lowest temp all cells are killed in 10 mins

Thermal death time (TDT)

minimal time all bacteria killed at a particular temp

High temp achieved by

increasing pressure