06 - dsDNA Viruses, Retroviruses, Prions

What is the main cause of viral gastroenteritis in infants and young children?

Rotavirus

Which species is Rotavirus found in?

Many mammalian species with a broad host range

Where does Rotavirus replicate?

In the cytoplasm

(without complete uncoating of the virion particle)

How many serogroups of Rotavirus are there?

7 serogroups (A-G)

Which serogroup of Rotavirus causes outbreaks in humans?

Serogroup A

How is Rotavirus transmitted?

Fecal-oral route

What is Rotavirus a significant cause of?

Severe diarrhea in infants and young children

When is the marked seasonal incidence for Rotavirus?

January through March

How long can infectious Rotavirus particles survive on surfaces?

For extended periods

Which part of the body does Rotavirus primarily infect?

Epithelial cells of the small intestine (jejunum)

Is Rotavirus resistant to stomach acid?

Yes, it is resistant to acidic pH of the stomach

What is the incubation period for Rotavirus?

48 hours or less

Can Rotavirus infections be subclinical?

Yes

What are the symptoms of a Rotavirus infection?

-Mild diarrhea/vomiting

-severe non-bloody watery diarrhea with dehydration

What is the infection rate of rotavirus worldwide?

Equal worldwide

How do Rotavirus infection outcomes vary based on global regions?

High malnutrition leads to increased severity of infection

What percentage of children in the US have Rotavirus antibodies by age 3 or 4?

90%

What is the mortality rate of Rotavirus in children? (developing vs. developed countries)

Low in younger children in developed countries

Higher in developing regions due to lack of medical care and high malnutrition

Do adults have immunity if they were infected with Rotavirus as children? What do they get?

Yes, only have a milder illness

Does breastfeeding affect the course of Rotavirus disease?

Yes, it leads to a milder disease course

What enzyme do Retroviruses contain?

Reverse transcriptase, which converts single-stranded RNA viral genome into double-stranded viral DNA

What is a unique feature of retroviruses?

They are disease-producing animal viruses

What is a major host cell protein found in the HIV virus envelope?

Major histocompatibility complex class 2 proteins (MACII)

How is HIV primarily transmitted? (4)

1) Sexually (heterosexual contact) through semen or vaginal secretion

2) Blood

3) Contaminated needles

4) Perinatally

What increases the risk of sexual transmission of HIV?

Ulcerative and nonulcerative infections

What is the chance of perinatal HIV transmission occuring without antiretroviral therapy?

15-45%

What happens if HIV is left untreated?

Leads to an immunodeficient state that allows opportunistic infections, progressing to AIDS and death

What cells are primarily infected by HIV initially?

CD4 lymphocytes

How does HIV progress?

Viral replication -> Progressive CD4 depletion -> Aids -> Death

What occurs during acute viremia in HIV infection?

High levels of virus replication in CD4 cells, with large amounts of the virus in the blood

What characterizes the latent phase of HIV?

Constant level of virus/infected cells and replacement of CD4 cells; can be clinically asymptomatic if the immune system is functional

What defines the transition from HIV infection to AIDS?

-CD4 count less than 200 AND

-Presence of a defining illness/opportunistic infection

What is AIDs?

A concurrent infection that attacks the immune system with HIV.
-release of mature virions, resulting in T cell death

What characterizes the end phase of HIV?

Encephalopathy/retinal ischemia

Name 8 AIDS-defining illnesses.

1) Candidiasis

2) Coccidioidomycosis

3) Cryptococcosis

4) CMV

5) Kaposi's sarcoma

6) Mycobacterium/tuberculosis

7) Pneumocystis pneumonia

8) Toxoplasmosis

What tests are used for HIV diagnosis and monitoring? (4)

-ELISA for screening

-Western Blot for confirmation

-PCR for identification

-Viral load and CD4 count

What is a normal viral load for HIV?

500-1500

Low: less than 200

What is PrEP and PEP in HIV treatment? What is each used for?

-PrEP is pre-exposure prophylaxis for high-risk individuals

-PEP is post-exposure prophylaxis initiated within 72 hours of a high-risk event to prevent replication of virus

What are Human T-cell Lymphotropic Viruses (HTLV)?

The first retroviruses associated with human diseases like adult T-cell leukemia and HTLV-associated myelopathy.

Which virus is associated with human disease in particular?

HTLV-1

Which strain of HTLV causes Adult T cell Leukemia (ATL)?

HTLV-1

What is HAM/TSP? What strain indicates its presence?

HTLV associated myelopathy (HAM/TSP)

– less common neurologic condition

-causing progressive weakness and ophthalmoplegia (CNS involvement indicated by presence of anti-HTLV1 antibodies in the CSF)

What is the most common transmission mode of HTLV-1 in endemic regions?

Mother-to-fetus or newborn transmission

What therapies/treatment result in a high survival rate for ATL and HAM?

Chemotherapy and Antiretroviral therapy

Traditional chemo is ineffective

True or false: Transmission of HTLV-1 varies with geographic areas and socioeconomic groups, and occurs primarily by cell associated virus

True

What are 3 ways HTLV-1 transmission occurs via cell associated virus?

1) Endemic regions - mother to fetus/newborn (most common)

2) Sexually via infected lymphocytes

3) Blood products containing intact cells

What type of leukemia is associated with HTLV-2?

Hairy cell leukemia in 5% of patients

Name that strain: Infection happens few years after infection, develops CNS involvement in a few years, causes muscular weakness and splenomegaly.

HTLV-2

What are prions?

Unconventional infectious agents

Describe prions

They're transmissible, resistant to degradation, and cause transmissible spongiform encephalopathies (TSE)

What is Bovine Spongiform Encephalopathy (BSE) commonly known as?

Mad Cow Disease

What causes Bovine Spongiform Encephalopathy?

Contaminated feed containing animal parts from diseased sheep or cattle

What is Creutzfeldt-Jakob Disease (CJD)?

A rare, rapidly progressive form of dementia that is fatal, with long incubation periods

How did CJD begin in the 1990s?

People in the UK ingested contaminated meat, or it also happened to others sporatically.

How does CJD occur in the brain? What is characteristic?

Disease protein starts to accumulate in brain creating webs/deforming gray matter which takes a characteristic spongiform appearance seen on autopsy

Early stags of ___________ are mistaken for Alzheimer's

CJD

True or false: CJD is fairly easy to fight

False. It is challenging to kill a protein that's not living!

How can Creutzfeldt-Jakob Disease be transmitted? (4)

1) Contaminated medical equipment

2) Human growth hormone injections

3) Corneal grafts

4) Transplants

What disease is often associated with fear of contact lens reuse?

CJD

Where in the eye can CJD be detected in? (3)

1) Anterior chamber

2) Vitreous

3) Cornea

All CJD patients must have rapidly progressive dementia AND how many other other signs?

2

Read this one just look it over. (In relation to CJD:)

Also need - anomalous EEG, MRI changes, brain injury protein in the CSF

What is characteristic of Kuru?

The only prion disease transmitted human-to-human

How does Kuru infection occur?

The infectious agent is acquired by an individual who was exposed to diseased brain tissue.

Where is Kuru seen?

Tribal populations practicing ritualistic cannibalism