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Microbiology - Unit 3 - Zach H. > Human Disease: Viruses & Prions 1 > Flashcards

Human Disease: Viruses & Prions 1 Flashcards

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1
Q

List the general characteristics of viruses.

A
  • Obligatory intracellular parasites
  • contain DNA or RNA
  • contain a protein coat
  • some are enclosed by an envelope
  • some viruses have spikes
  • most viruses infect only specific types of cells in one host
  • Host range is determined by specific host attachment sites and cellular factors
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2
Q

Viruses are classified by morphology. What are the classes?

A
  • Helical viruses
  • Polyhedral viruses
  • Enveloped viruses
  • Complex viruses
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3
Q

Give two examples of a helical virus.

A
  • Rabies
  • Ebola hemorrhagic fever

long rods, helical structure

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4
Q

Give two examples of a polyhedral virus.

A
  • adenovirus
  • poliovirus

polyhedral = many sided, 20 triangular faces

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5
Q

Give two examples of a enveloped virus.

A
  • influenza virus
  • herpes simplex virus

roughly spherical, unless otherwise noted

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6
Q

Give an example of a complex virus.

A
  • bacteriophage
  • poxvirus

capsid does not enter the cell like it does in eukaryotic enveloped viruses

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7
Q

What are the steps in multiplication of an animal virus?

A

> Attachment - viruses attach to cell membrane.

 - pinocytosis 
 - fusion

> Penetration/Entry - endocytosis or fusion.

> Uncoating - viral or host enzymes.

> Biosynthesis - production of nucleic acid and proteins.

> Maturation - nucleic acid and capsid proteins assemble.

> Release - by budding (enveloped viruses) or rupture.

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8
Q

What are the special features of biosynthesis of ssDNA viruses?

A

Cellular enzyme transcribes viral DNA in nucleus.

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9
Q

What are the special features of biosynthesis of dsDNA viruses?

A
  • Cellular enzyme transcribes viral DNA in nucleus.

- Viral enzyme transcribes viral DNA in virion, in cytoplasm.

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10
Q

What are the special features of biosynthesis of DNA, reverse transcriptase, viruses?

A

Cellular enzyme transcribes viral DNA in nucleus; reverse transcriptase copies mRNA to make viral DNA.

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11
Q

What are the special features of biosynthesis of RNA, + strand, viruses?

A

Viral RNA functions as a template for synthesis of RNA polymerase which copies negative strand RNA to make mRNA in cytoplasm.

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12
Q

What are the special features of biosynthesis of RNA, negative strand, viruses?

A

Viral enzyme copies viral RNA to make mRNA in cytoplasm.

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13
Q

What are the special features of biosynthesis of dsRNA viruses?

A

Viral enzyme copies - strand RNA to make mRNA in cytoplasm.

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14
Q

What are the special features of biosynthesis of RNA ,reverse transcriptase, viruses?

A

Viral enzyme copies viral RNA to make DNA in cytoplasm; DNA moves to nucleus.

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15
Q

Latent and Persistent Viral Infections

A

> Virus remains in asymptomatic host cell for long periods.
- cold sores, shingles

> Disease process occurs over a long period; generally is fatal.
- subacute sclerosing panencephalitis (measles virus)

persistent infection does not drop off

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16
Q

What are the characteristics that viruses are classified on?

A
  • nucleic acid type
  • presence or absence of envelope
  • capsid symmetry
  • dimensions of virion and capsid

NOT classified on morphology

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17
Q

What is the alternative classification scheme for viruses?

A

> David Baltimore

  • focuses on viral genome and process used to synthesize viral mRNA
  • 7 life cycle groups based on:
    • dsDNA
    • ssDNA
    • dsRNA
    • ssRNA (+ or - strand)
    • retrovirus
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18
Q

What family is the RNA virus that causes HIV in?

A

retroviridae

  • Pandemic with uncertain origin.
    • HIV-1 evolved from chimp virus SIVcpz
  • Only group M HIV-1 is widespread in U.S.
  • HIV-2 is widespread in Africa.
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19
Q

What is the transmission of HIV?

A

When infected blood, semen, or vaginal secretions come in contact with uninfected person’s broken skin or mucous membranes.

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20
Q

What is the life cycle of HIV?

A

> Virion has viral protein spike, gp120.
- attaches to CD4 cells (T helper cells and other cells) and co-receptors CCR5 and CXCR-4.

> RNA virus carries reverse transcriptase into host cell.

> Reverse transcribed into dsDNA, which integrates into human genome as provirus.

> Integrates into host cell’s DNA as a provirus.

> Can remain latent - asymptomatic.

> Can direct synthesis of viral RNA -> synthesis of new viral particles.
- new virion are assembled and released through budding and eventual lysis.

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21
Q

What is the course of disease - HIV to AIDS?

A

> Some patients rapidly develop clinical AIDS; die within 2-3 years.

> Some patients remain relatively healthy for at least 10 years post infection.

> In majority of patients HIV infection progresses to AIDS in 8-10 years.

> T helper cell count reduces and opportunistic infections begin.

patients that are long term persistent with HIV have Abs that recognize HIV better than patients that die quickly. Typically, patients with HIV have a problem because the HIV can invade the Abs that have been made by the humoral immune system against HIV virus

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22
Q

What are the CDC classification system for stages of acute, HIV-related conditions?

A

> 2-8 weeks after infection.
Most experience brief illness called acute retroviral syndrome.
Rapid multiplication and dissemination of virus throughout body.
Stimulation of immune response.

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23
Q

What are the CDC classification system for stages of asymptomatic (latent), HIV-related conditions?

A

> May last from 6 months to 10 or more years.
Levels of detectable HIV in blood decrease, although viral replication continues.
Effects on immune functions may occur.

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24
Q

What are the CDC classification system for stages of chronic symptomatic, HIV-related conditions?

A

> Formerly called AIDS-related complex.
Can last for months to years.
Viral replication continues.
Numbers of CD4 cells in blood significantly decrease.
- results in patients developing a variety of illnesses often caused by opportunistic pathogens and AIDS related cancers.

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25
What are the CDC classification system for stages of AIDS (fourth and last stage), HIV-related conditions?
> Immune system no longer able to defend against virus.
26
What is the definition of AIDS?
All HIV-infected individuals who have fewer than 200 CD4 T cells/microliter of blood or a CD4 cell percentage of lymphocytes of less than 14.
27
What are the central nervous system diseases that can be caused by HIV?
> Headaches, fever, subtle cognitive changes, abnormal reflexes, and ataxia. > Dementia and severe sensory and motor changes observed in advanced cases. > Autoimmune neuropathies, cerebrovascular disease, and brain tumors are common.
28
How is HIV diagnosed?
> viral isolation and culture > assays for reverse transcriptase activity or viral antigens > most commonly done by detection of specific anti-HIV Abs in the blood - routine screening tests use ELISA assays which have many flase positive results which are retested using Western blot technique > most sensitive test uses polymerase chain reaction
29
What is the treatment for AIDS?
> No cure for AIDS > Treatment directed at reducing viral load, disease symptoms, and treating disease and malignancies. > Most successful treatment involves a combination. - nucleoside reverse transcriptase inhibitors (e.g., AZT) - nonnucleoside reverse transcriptase inhibitors (e.g., delavirdine) - protease inhibitors (e.g., indinavir) - fusion inhibitors (Fls) - prevent entry of HIV into cells, (e.g., enfuvirtide)
30
What is the prevention and control of HIV?
> Achieved primarily through education. > Barrier protection from blood and body fluids. > Not sharing intravenous needs or syringes. > Continued screening of blood and blood products.
31
What is the current research for HIV vaccines?
> Not available but ongoing research. > Ideal vaccine. - would stimulate the production of neutralizing Abs which would bind to virus preventing it from entering host cells - promote formation of cytotoxic T cells capable of destroying cells infected with virus > Problems with development of vaccine. - envelope proteins of virus continually change their antigenic properties
32
What has the study of long-term nonprogressors of HIV patients found?
> HIV-infected people who: - maintain CD+ T cell counts of at least 600 cells/ul of blood. - have 10 years after documented infection. > Explanations of phenomena: - effective immune response to relatively conserved proteins. - initial infection was with attenuated strain. - predisposing genetic differences.
33
What are the characteristics of dsDNA viruses?
> Largest group of known viruses. > Most bacteriophages have dsDNA. > Important vertebrate viruses: - herpesviruses - poxviruses > Insect viruses. > Some rely on host's DNA/RNA polymerases.
34
What are the herpesviridae subfamilies?
- alpha - beta - gamma - unclassified subfamilies
35
Which viruses are in the Herpesviridae subfamily, alpha?
> herpes simplex virus I and II | > varicella zoster virus (HSV-3) - chicken pox and shingles.
36
Which viruses are in the Herpesviridae subfamily, beta?
cytomegalovirus (HSV-5)
37
Which viruses are in the Herpesviridae subfamily, gamma?
> Epstein-Barr virus (HSV-4) - infectious mononucleosis. > Some cancers (Kaposi's sarcoma).
38
What are the characteristics of Herpesvirus virions?
- icosahedral - 120-200 nm - pleomorphic - enveloped - surface spikes - linear genomes (50-100 genes) - targets are epithelial or nerve cells - envelope surrounds tegument (layer of proteins) which surrounds nucleocapsid
39
What are the targets of Herpesvirus virons?
- epithelial cells | - nerve cells
40
What are the two types of Herpesvirus infections?
> productive (primary) infections - 50,000-200,000 virions produced/cell - cell dies due to degraded DNA > Latent infections - occurs in neuronal cells - infectious virus not detected - can be reactivated in neurons - production infection recurs
41
What are the characteristics of a Herpesvirus productive infection?
> receptor mediated attachment > virus envelope fuses with host cell membrane > linear dsDNA enters nucleus, circularizes - immediate early and early proteins made * used for viral DNA replication - late gene transcription * viral structural proteins > nucleocapsid assembles and leaves nucleus > tegument proteins associate with nucleocapsid > virus envelope is generated by Golgi apparatus > mature enveloped virion leaves cell
42
What are the characteristics of a Herpesvirus latent infection in epithelial cells?
> viral protein, VP16 and host cell factor (HCF) may enter nucleus with the viral genome > both required for full expression of immediate early genes and lytic infection
43
What are the characteristics of a Herpesvirus latent infection in neurons?
> VP16 and HCF do not enter nucleus > immediate early gene expression decreased > small noncoding RNAs (microRNAs) produced by virus also reduce immediate early genes
44
Where can the HSV-1 remain latent at in patients?
Trigeminal nerve ganglia
45
Herpes Simplex
> Human herpesvirus 1 (HSV-1) and 2 (HSV-2). > Cold sores or fever blisters (vesicles on lips). > Herpes gladiatorum (vesicles on skin). > Herpetic whitlow (vesicles on fingers). > Herpes encephalitis > HSV-1 can remain latent in trigeminal nerve ganglia.
46
Are cold sores (fever blisters (herpes labialis)) usually caused by herpes simple virus type 1 (HSV-1) or herpes simplex virus type 2 (HSV-2)?
Usually caused by herpes simplex virus type 1 (HSV-1); rarely herpes simplex virus type 2 (HSV-2). **enveloped dsDNA virus with icosahedral capsid**
47
What are the clinical manifestations of cold sores (typically caused by HSV-1)?
> characteristic blister at site of inoculation > gingivostomatitis - lips, mouth, and gums > herpetic keratitis - cornea > lifetime latency develops, with periodic reactivation in times of stress
48
What is the treatment, prevention, and control of cold sores?
> diagnosis by ELISA, direct fluorescent antibody screening of tissue or PCR > acyclovir and other antivirals > no vaccine, education important
49
Is genital herpes typically caused by HSV-1 or HSV-2?
Usually caused by herpes simplex type 2 (HSV-2). - linear dsDNA - enveloped virus Very common sexually transmitted disease and to infant during vaginal delivery (congenital or neonatal herpes) Active and latent disease with reactivations.
50
What are the clinical manifestations of genital herpes?
> fever, burning sensation, genital soreness, and blisters in infected area > blisters heal spontaneously, but virus remains latent and is periodically reactivated
51
How is genital herpes treated?
With antiviral drugs (e.g., acyclovir).
52
What are the characteristics of congenital (neonatal) herpes?
> usually HSV-2 > one of the most life-threatening of all infections in newborns > 1,500-2,200 babies/year in U.S. > can result in neurologic involvement and blindness > Caesarian section recommended
53
In patients with herpes simplex, where can HSV-2 remain latent?
sacral nerve ganglia
54
What can herpes simplex caused by HSV-2 cause?
HSV-2 encephalitis - 70% fatality. Remains latent in sacral nerve ganglia. Encephalitis treatment - acyclovir.
55
What are the characteristics of chickenpox (Varicella) and shingles (Herpes Zoster)?
> DNA virus, member of Herpesviridae (HHV-3) > Humans serve as reservoir and source > Acquired by droplet inhalation into respiratory system > Chickenpox: - results from initial infection - vaccine prevents or shortens illness > Shingles (herpes zoster; postherpetic neuralgia): - reactivated form of chickenpox * virus resides in cranial and sensory neurons * reactivation - virus migrates down neuron
56
What is the treatment for chickenpox (varicella) and shingles (herpes zoster)?
supportive; acyclovir and others
57
What causes mononucleosis (infectious)?
Epstein-Barr virus (EBV, HHV-4)
58
What are the characteristics of Epstein-Barr virus?
``` > herpes virus > dsDNA > icosahedral with envelope > infects B cells and epithelial cells > also associated with Burkitt's lymphoma and nasopharyngeal carcinoma ```
59
How is mononucleosis spread?
Mouth-to-mouth contact. **transmitted via saliva**
60
Are mononucleosis infections in children symptomatic or asymptomatic?
asymptomatic
61
What is mononucleosis characterized by in a blood smear?
proliferation of monocytes
62
What are the clinical manifestations of mononucleosis?
> Enlarged LNs and spleen, sore throat, headache, nausea, general weakness, and tiredness, and mild fever. > Self-limited disease, lasting 1-6 weeks.
63
What is the treatment, prevention, and control of mononucleosis?
> rapid diagnostic tests | > symptomatic - supportive therapy
64
What can Epstein-Barr virus (HHV-4) cause?
> Burkitt's lymphoma > Nasopharyngeal carcinoma **cancer in immunosuppressed individuals and in malaria and AIDS patients**
65
What causes cytomegalovirus inclusion disease?
human cytomegalovirus (HCMV, HHV-5)
66
What are the characteristics of human cytomegalovirus (HCMV, HHV-5)?
> dsDNA virus, Herpesviridae > enveloped icosahedral capsid > HCMV can infect any cell of the body (monocyte, lymphocyte, epithelial) > causes formation of intra-nuclear inclusion bodies and cytoplasmic inclusions > infected cells swell (cyto-, mega-) > virus shed in semen and cervical solutions - can be transmitted by transfusions/organ transplants, blood > transmitted across the placenta; may cause mental retardation > latent in white blood cells > usually asymptomatic infection - can be serious in immunocompromised individuals - leading cause of congenital viral disease - symptoms often resemble mononucleosis
67
What is the treatment, prevention, and control of HCMV disease?
> antiviral agents used for high-risk patients > avoiding close personal contact with infected individual > blood transfusions and organ transplants from seronegative donors
68
What can human herpesvirus-8 (HHV-8) cause?
Kaposi's sarcoma * cutaneous lesion with or without internal involvement* * primarily in AIDS patients*
69
What kind of cells does HHV-8 target?
Lymphocytes and other cells.
70
How many different viruses cause hepatitis?
11 different viruses: > 2 herpesviruses - Epstein-Barr virus (EBV) and cytomegalovirus (CMV). > 9 hepatotropic viruses
71
What is the transmission of hepatitis A?
fecal-oral
72
What is the transmission of hepatitis B?
- parenteral | - STI
73
What is the transmission of hepatitis C?
parenteral
74
What is the transmission of hepatitis D?
- pareteral | - HBV coinfection
75
What is the transmission of hepatitis E?
fecal-oral
76
What is the pathogen that causes hepatitis A?
Picornaviridae
77
What is the pathogen that causes hepatitis B?
Hepadnaviridae
78
What is the pathogen that causes hepatitis C?
Filoviridae
79
What is the pathogen that causes hepatitis D?
Deltaviridae
80
What is the pathogen that causes hepatitis E?
Caliciviridae
81
Which types of hepatitis do not cause chronic liver disease?
Hepatitis A and E
82
Which types of hepatitis cause chronic liver disease?
Hepatitis B, C, D
83
What is the vaccine against hepatitis A?
inactivated virus
84
What is the vaccine against hepatitis B?
recombinant
85
What is the vaccine against hepatitis C
none
86
What is the vaccine against hepatitis D?
HBV vaccine
87
What is the vaccine against hepatitis E?
HAV vaccine
88
What are the characteristics of Hepatitis B virus (HBV)?
> dsDNA virus > Dane particle is infectious virion > transmitted through body fluids and intra-venous equipment > can pass the placenta and breast milk > 1.25 million chronically infected in U.S., 200 million worldwide
89
What are the clinical signs of hepatitis B?
> most cases are asymptomatic > generalized symptoms occurs after 1-3 month incubation period > virus infects liver hepatic cells causing liver damage - yellow appearance (jaundice) results from bilirubin accumulation > chronic infection can cause development of primary liver cancer (2nd only to tobacco as known cause of cancer)
90
What is done for the prevention and control of hepatitis B?
> passive immunotherapy within 7 days of exposure > excluding contact with contaminated materials > vaccination of high-risk groups: - 0-18 year olds - contacts of carriers - health-care professionals

Microbiology - Unit 3 - Zach H. (1 decks)

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