Lesson 5.7. Multiplication of Human Viruses

Attachment to the Host Cell

Step 1 of Multiplication of Human Viruses

Brownian motion

ATTACHMENT TO THE HOST CELLS (STEPS):

1. Initial contact dependent on ______________

2. ___________________ during which electrostatic repulsion is reduced

3. ___________________ in virus-receptor-host-receptor configuration that initiates viral penetration through the cell membrane

1 = ?

Reversible phase

ATTACHMENT TO THE HOST CELLS (STEPS):

1. Initial contact dependent on ______________

2. ___________________ during which electrostatic repulsion is reduced

3. ___________________ in virus-receptor-host-receptor configuration that initiates viral penetration through the cell membrane

2 = ?

Irreversible changes

ATTACHMENT TO THE HOST CELLS (STEPS):

1. Initial contact dependent on ______________

2. ___________________ during which electrostatic repulsion is reduced

3. ___________________ in virus-receptor-host-receptor configuration that initiates viral penetration through the cell membrane

3 = ?

Viral receptors (glycoproteins)

Recognize and bind receptors on the host cells and provide the virus with its high specificity

Penetration of the Viral Particles

Step 2 of Multiplication of Human Viruses

Endocytosis

PENETRATION OF THE VIRAL PARTICLES:

• cell brings external materials into itself by engulfing them with its cell membrane, which then pinches off to form a vesicle or vacuole

• virus-host-receptor interaction triggers the cell membrane to engulf the virus particle, forming a cystosolic vacuole

for non-enveloped but with few enveloped viruses

ex of viruses that undergoes endocytosis

Fusion

PENETRATION OF THE VIRAL PARTICLE:

• happens to their envelope with the host-cell membrane, liberating the viral capsid within the cell cytoplasm

enveloped viruses

ex of viruses that undergoes fusion

Injection

PENETRATION OF THE VIRAL PARTICLE:

• for bacteriophage which infects bacteria by contracting their tail to inject DNA through the bacterial wall and membrane

Uncoating of the Viral Particle

Step 3 of Multiplication of Human Viruses

nucleic acid

UNCOATING OF THE VIRAL PARTICLE:

1. Release of the _______________ from the capsid

2. (a._____________) acidification of the cytosolic vacuoles following endosome fusion induces a conformational change in the capsid and the release of viral b._________ (helper proteins plus nucleic acid) into the cytoplasm

3. Partial uncoating () might also happen

1 = ?

endocytosis

UNCOATING OF THE VIRAL PARTICLE:

1. Release of the _______________ from the capsid

2. (a._____________) acidification of the cytosolic vacuoles following endosome fusion induces a conformational change in the capsid and the release of viral b._________ (helper proteins plus nucleic acid) into the cytoplasm

3. Partial uncoating (_________________) might also happen

2.a. = ?

nucleocapsid

UNCOATING OF THE VIRAL PARTICLE:

1. Release of the _______________ from the capsid

2. (a._____________) acidification of the cytosolic vacuoles following endosome fusion induces a conformational change in the capsid and the release of viral b._________ (helper proteins plus nucleic acid) into the cytoplasm

3. Partial uncoating (_______________) might also happen

2.b. = ?

reovirus

UNCOATING OF THE VIRAL PARTICLE:

1. Release of the _______________ from the capsid

2. (a._____________) acidification of the cytosolic vacuoles following endosome fusion induces a conformational change in the capsid and the release of viral b._________ (helper proteins plus nucleic acid) into the cytoplasm

3. Partial uncoating (_____________) might also happen

3 = ?

Replication of the Nucleic Acids and Translation of the Genome

Step 4 of Multiplication of Human Viruses

Viral Replication

Replication of the Nucleic Acids and Translation of the Genome

• ensures that the host cell synthesis machinery is taken over by the virus and the viral genome is replicated

viral mRNa

MECHANISM OF VIRAL REPLICATION:

1. Transcription of viral genes into ____________

2. Translation of the viral genome into _________

3. Replication of the _____________

1 = ?

proteins

MECHANISM OF VIRAL REPLICATION:

1. Transcription of viral genes into ____________

2. Translation of the viral genome into _________

3. Replication of the _____________

2 = ?

viral genome

MECHANISM OF VIRAL REPLICATION:

1. Transcription of viral genes into ____________

2. Translation of the viral genome into _________

3. Replication of the _____________

3 = ?

Transcription

the process by which genetic information in DNA or RNA is copied into messenger RNA (mRNA).

• DNA → mRNA

• RNA → mRNA

Translation

the process by which the mRNA is read by ribosomes (of the hijacked host cell) to make proteins.

• mRNA → Proteins

release of nucleocapsid

Transcription and Translation:

a. occur immediately after the ____________________ in to the cytoplasm

ensures:

b. production of early proteins such as _______________

c. hijacking of the _________________ machinery

a = ?

viral polymerases

Transcription and Translation:

a. occur immediately after the ____________________ in to the cytoplasm

ensures:

b. production of early proteins such as _______________

c. hijacking of the _________________ machinery

b = ?

cell synthesis

Transcription and Translation:

a. occur immediately after the ____________________ in to the cytoplasm

ensures:

b. production of early proteins such as _______________

c. hijacking of the _________________ machinery

c = ?

type of nucleic acid

REPLICATION OF THE NUCLEIC ACIDS AND TRANSLATION OF THE GENOME:

1. Replication depends on the _________________ carried by the virus

2. Viral mRNA: __________; several distinct proteins are encoded within a single piece of mRNA

3. Virus needs to use a virus-specific __________ to cut at the correct place the polyprotein produced by translation to restore the functionality of viral proteins

1 = ?

polycistronic

REPLICATION OF THE NUCLEIC ACIDS AND TRANSLATION OF THE GENOME:

1. Replication depends on the _________________ carried by the virus

2. Viral mRNA: __________; several distinct proteins are encoded within a single piece of mRNA

3. Virus needs to use a virus-specific __________ to cut at the correct place the polyprotein produced by translation to restore the functionality of viral proteins

2 = ?

protease

REPLICATION OF THE NUCLEIC ACIDS AND TRANSLATION OF THE GENOME:

1. Replication depends on the _________________ carried by the virus

2. Viral mRNA: __________; several distinct proteins are encoded within a single piece of mRNA

3. Virus needs to use a virus-specific __________ to cut at the correct place the polyprotein produced by translation to restore the functionality of viral proteins

3 = ?

positive strand RNA (poliovirus)

REPLICATION PROCESS:

• used directly as mRNA following the acquisition of a terminal sequence from the host cell

negative strand RNA (influenza virus)

REPLICATION PROCESS:

• transcribed into a positive RNA using an RNA-dependent RNA polymerase carried by the virus

ds DNA viruses (adenoviruses)

REPLICATION PROCESS:

• nucleic acid passes into the nucleus, where it is usually transcribed by a host DNA-dependent RNA polymerase

• Poxvirus - the enzyme is contained within the virus, allowing the relocation in the cytoplasm

SS RNA (HIV)

REPLICATION PROCESS:

• reverse transcribed to a ss proviral DNA by reverse transcriptase

• Acts both as an RNA and DNA directed DNA polymerase

• Has RNAase activity

• Proviral DNA can be transported to the cell nucleus where it can be integrated within the cell host genome by a viral integrase

Maturation or Assembly of Virions

Step 5 of Multiplication of Human Viruses

structural proteins

Maturation or Assembly of Virions

1. viral capsid starts to form from individual __________________

2. replicated viral genome and some viral proteins become packaged within the _______ (cytoplasm or in the cell nucleus)

3. (enveloped) envelope originates from the __________

4. presence of _____________________ may play an important role in the interaction of the nucleic acid and the structural proteins

1 = ?

capsid

Maturation or Assembly of Virions

1. viral capsid starts to form from individual __________________

2. replicated viral genome and some viral proteins become packaged within the _______ (cytoplasm or in the cell nucleus)

3. (enveloped) envelope originates from the __________

4. presence of _______________ may play an important role in the interaction of the nucleic acid and the structural proteins

2 = ?

host

Maturation or Assembly of Virions

1. viral capsid starts to form from individual __________________

2. replicated viral genome and some viral proteins become packaged within the _______ (cytoplasm or in the cell nucleus)

3. (enveloped) envelope originates from the __________

4. presence of _______________ may play an important role in the interaction of the nucleic acid and the structural proteins

3 = ?

chaperone proteins

Maturation or Assembly of Virions

1. viral capsid starts to form from individual __________________

2. replicated viral genome and some viral proteins become packaged within the _______ (cytoplasm or in the cell nucleus)

3. (enveloped) envelope originates from the __________

4. presence of ___________________ may play an important role in the interaction of the nucleic acid and the structural proteins

4 = ?

Release of Virions into the Surrounding Environment

Step 6 of Multiplication of Human Viruses

mature virions

Release of Virions into the Surrounding Environment:

• _____________________ are released from the host cell

budding process

Release of Virions into the Surrounding Environment:

• Enveloped Viruses are released by a ________________________ in which the Host cell will die following damage to its metabolism and housekeeping functions during viral replication

cell lysis

Release of Virions into the Surrounding Environment:

a. Non-enveloped Virus progeny accumulates within the host cell cytoplasm and is released following ______________.

b. Viruses (bacteriophages) produce a ______________________________ to lyse (causing a bursting) the host, enabling the release of infectious particles

c. Host _________________ as it cannot maintain normal housekeeping functions during viral infection

a = ?

lytic enzyme (peptide) or proteases

Release of Virions into the Surrounding Environment:

a. Non-enveloped Virus progeny accumulates within the host cell cytoplasm and is released following ______________.

b. Viruses (bacteriophages) produce a ______________________________ to lyse (causing a bursting) the host, enabling the release of infectious particles

c. Host ____________________ as it cannot maintain normal housekeeping functions during viral infection

b = ?

self-disintegrates

Release of Virions into the Surrounding Environment:

a. Non-enveloped Virus progeny accumulates within the host cell cytoplasm and is released following ______________.

b. Viruses (bacteriophages) produce a ______________________________ to lyse (causing a bursting) the host, enabling the release of infectious particles

c. Host ________________ as it cannot maintain normal housekeeping functions during viral infection

c = ?