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Neural Biology 1 > Micro viruses 2 > Flashcards

Micro viruses 2 Flashcards

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1
Q

What are viruses ?

A

Viruses are sub cellular, infectious agents that are obligate intracellular parasites

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2
Q

What are the size of virus?

A

20-300nm in size - small

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3
Q

Why can viruses not do ?

A

Cannot replicate outside living cells

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4
Q

How can the viruses multiply ?

A

In order to multiply viruses have to get into a cell in

which they can replicate – a host cell

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5
Q

What do viruses take advantage of ?

A

the host cell’s metabolic machinery to create progeny virions
A broad variety of viruses contribute to human disease

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6
Q

What is the basic structure of the virus ?

A

The basic structure of a virus consists of a capsid surrounding the viral genome

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7
Q

What is the nucleocapsid ?

A

The genome and the capsid together

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8
Q

What is a capsid?

A

The capsid is a protein shell composed of repeating subunits called capsomeres

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9
Q

What is Icosohedral symmetry is the ?

A

preferred capsid morphology (20 equalateral triangular faces)

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10
Q

What are alternative morphologies ?

A
  • Helical nucleocapsid
  • Other virus families are surrounded by a lipid envelope (derived from the host cell membrane). The envelope is studded with glycosylated transmembrane proteins that are involved in host cell attachment
  • The viral genome may be composed of DNA or RNA (single stranded or double stranded)
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11
Q

How can viruses be classified by ?

A

according to their genome type and replication strategy (Baltimore classification)

  • dsDNA
  • ssDNA
  • dsRNA replicating via (+) sense RNA
  • ssRNA (+) sense genomes
  • ssRNA (-) antisense genomes- complementary sequence to messenger RNA sequence
  • Diploid ssRNA
  • Retroviruses (e.g HIV) (contain an enzyme (reverse transcriptase) that converts the retroviral RNA genome into double-stranded DNA.

ds = double stranded
ss- single stranded

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12
Q

What does the viral genome generate?

A

messenger RNA which is translated into proteins

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13
Q

what are the structures of virus like ?

A

different shape and forms

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14
Q

What is the Schematic representation of SARS-CoV-2 structure? (COVID-19)

A

This is an enveloped, positive-sense RNA virus with four main structural proteins, including spike (S) and membrane (M) glycoproteins, as well as envelope (E) and nucleocapsid (N) proteins.
-spike protein attaches iris to host cell

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15
Q

What viruses are clinically significant ?

A
  • Respiratory viruses
    1. Adenovirus (respiratory tract infections)
    2. Parainfluenza virus (pharyngitis (sore throat))
    3. Rhinovirus (tonsillitis and sinus infection)
    4. Corona viruses (e.g SARS CoV-1, SARS CoV-2) (severe acute respiratory syndrome
  • Retrovirus
    1. HIV (AIDS)
  • Papillomavirus (warts)
  • Pox virus
    1. Small pox
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16
Q

What are some more viruses of clinical significance ?

A 
Hepatitis virus
Hepatitis A-E (liver dysfunction)
Childhood diseases
Rubella
Rubeola (measles)
Mumps
Herpes virus
Herpes Simplex Virus (HSV-1, HSV-2), Cytomegalovirus (CMV), Epstein Barr Virus (EBV), Varicella Zoster Virus (VZV) (cold sores, glandular fever, lymphomas, shingles, acute CNS infections)
HSV-1 most common cause of corneal infections
17
Q

What are the strategies for infectivity and replication?

A
  • The first stage of viral infection involves entry into the host cell
  • Viruses utilise different strategies
  • Attachment
  • Translocation
  • Genome insertion (naked virus)
  • Membrane fusion (enveloped virus)
  • Endocytosis and endosome formation (enveloped virus)
18
Q

How is the replication of virus after entering the cell ( strategies for infectivity and replication ) ?

A
  • Viral genome transcribed to form new virions
  • Translation using host cellular machinery
  • First proteins synthesised are generally DNA or RNA polymerases
  • In general, DNA replication occurs in the nucleus, RNA replication occurs in the cytoplasm
19
Q

What happens with retroviruses after entering the cell ( strategies for infectivity and replication ) ?

A
  • Retroviruses are RNA viruses that convert their ssRNA into dsDNA
  • Structural proteins synthesised
  • Viral assembly primarily in the cytoplasm
  • Release of newly formed virions
20
Q

What is the life cycle of SARS-CoV-2?

A

SARS-CoV-2 is internalized by the cell via (i) membrane fusion or (ii) endocytosis. The SARS-CoV-2 spike binds to the angiotensin-converting enzyme 2 (ACE2) via its receptor-binding domain (RBD) and further releases its RNA (b), which will be translated into viral proteins (c,d). e–h, These proteins will form a replication complex to create additional RNA (e) that will further assemble with the viral proteins into a new virus (f), which will be released (g,h) via exocytosis

21
Q

What is the infectivity of humans?

A
  • Virus-induced pathology is the result of direct viral action leading to host cell death
  • Damage can also occur due to the immune response to viral antigens
22
Q

What are the routes of transmission ?

A

Viruses can be spread by a variety of routes:

  • Respiratory droplets
  • Faecal-oral
  • Parenteral
  • Sexual activity
23
Q

What ways immune system deals with virus ?

A
  1. through antibody response - neutralise virus- antibody binds to virus to prevent virus from infecting more cells
  2. Mediated destruction of viruses- antibodies can mediate cell death through antibody mediator cells- cytotoxicity - once virus has been identifies in cell– get T helper cell - activates cytotoxic T cells CD8 positive cells- these induces apoptosis
24
Q

What is latent infection ?

A

With some viruses, a latent infection can be established after a primary infection
e.g. Herpes viruses can remain latent in sensory ganglia

25
Q

What is diagnostic virology ?

A
  • Diagnosis of viral disease is often made on the clinical picture
  • In vitro propagation in cultured cells (cells can be fixed and screened for infection)
  • Serological tests can screen for anti-viral antibodies
  • PCR and hybridization techniques can be used for molecular diagnosis
26
Q

What are some antiviral agents ?

A

Virucides e.g. detergents, chloroform uv light
Antiviral agents that target specific components of the viral life cycle
Attachment
Penetration
Inhibition of replication
Other drugs stimulate the host immune response e.g. interferon
Active immunization with subunit or live attenuated viruses increases long-term protection e.g. MMR
Passive immunity can be achieved using high dose antiviral antibodies e.g. Varicella zoster

27
Q

What is chylamdia ?

A

Obligate intracellular pathogens

Once considered to be viruses but now known to be a Gram –ve bacterium

28
Q

What are the 3 species causing chylamadia ?

A
  • 3 species causing human disease
    -Chlamydia trachomatis
    (causes urogenital infection, conjunctivitis and trachoma)
    -Chlamydia pneumoniae (causes sinusitis, bronchitis and pneumonia)
    -Chlamydia psittaci (can cause pneumonia)
29
Q

What is the infectious agent in chlymidia ?

A
  • Infectious agent is the elementary body which binds to receptors on host cells
  • Unable to synthesise ATP
  • Responsive to certain antibiotics

Neural Biology 1 (58 decks)

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