Final Exam

What is the most common vector-borne viral disease in the world?

Dengue

Which viral disease involves muscle and joint pain and a rash that may become hemorrhagic?

Dengue

What is the defining symptoms of severe dengue?

Greater hemorrhaging and risk of DIC

What cells does dengue virus infect?

Epidermal dendritic cells and keratinocytes

Severe dengue is thought to be the result of _________.

Antibody-dependent enhancement (ADE)

What is ADE?

• Virus uses antibody as second receptor → increased infectious dose

• Virus NOT neutralized

What process results in plasma leakage in severe dengue?

Cytokine storm (throughout organism) → activated complement and cytokines

What is the main approach in preventing dengue fever?

Mosquito control → use of insecticides and use of bacterium to interrupt viral replication

T/F: There is a vaccine available for dengue fever.

T

Which viral disease results in a bent posture due to sever joint pain?

Chikungunya

T/F: Joint pain associated with chikungunya can last for weeks after infection.

T

What are the vectors of dengue, zika and chikungunya?

Aedes mosquitos

Which viral infection can result in decreased helper T-cell population?

Chikungunya

Which viral infection has a possible connection to Guillain-Barré syndrome?

Zika virus

Which viral disease has resulted in microcephaly in infected infants?

Congenital zika syndrome

T/F: Zika virus is only transmitted by mosquitos.

F; Zika virus can also be sexually transmitted

Which parasitic disease is spread by the bite of a sandfly?

Leishmaniasis

What are the three forms of leishmaniasis?

• Cutaneous (CL)

• Mucocutaneous (ML)

• Visceral (VL)

Which type of leishmaniasis is most severe, widespread throughout the body, causes pancytopenia and is often fatal?

VL

Which form of a leishmania parasite is injected into a host and taken up by the skin?

Promastigote

What is the primary reservoir of transmission for leishmaniasis?

Humans

T/F: There is no vaccine available for leishmaniasis.

T

T/F: Neurons have regenerative capacity.

F; once damaged, neurons are very unlikely to regenerate

Which body system does not possess its own bacterial flora?

Nervous system

What is the nervous system’s primary defense against infection?

Isolation

What selective filter allows nutrients, such as oxygen, into the brain?

Blood-brain barrier

What system acts to ‘clean’ our brains?

Lymphatic waves → rinses into cervical lymphatic glands and the nose

T/F: Proteins, antibodies, RBCs and WBCs are typically found in CSF.

F; this indicates some kind of leakage and alerts medical personnel to a problem

What symptoms are commonly involved in nervous system infections?

Impaired ability to think, feel or move

The most common species that cause meningitis are often part of normal microbiota of the ___________.

Upper respiratory tract

What is the tell-tale symptom of meningitis?

Stiff neck

What is the case-fatality rate for untreated bacterial meningitis?

Approaches 100% fatality; can be within a few hours

What causes most of the damage to the CNS in meningitis?

Inflammatory response

Which is typically more severe, bacterial meningitis or viral meningitis?

Bacterial meningitis

How is bacterial meningitis spread?

Respiratory droplets

How is viral meningitis spread?

Fecal-oral route

What is the causative agent of pneumococcal meningitis?

Streptococcus pneumoniae

Mortality and neurological damage are more common with which type of meningitis?

Pneumococcal meningitis

Which type of meningitis is characterized by petechiae?

Meningococcal meningitis

Meningococcal meningitis is caused by ______.

Neisseria meningitidis

N. meningitidis easily acquires DNA through ________.

Horizontal gene transfer

Which vaccine saw a 98% decrease of infection in some areas?

Meningococcal meningitis

T/F: Meningococcal meningitis can be treated with a vaccine and antibiotics, such as penicillin.

T

T/F: There is treatment available for viral meningitis.

F

Sporadic encephalitis can result due to reactivation of ________.

Latent herpesvirus infections

What is the usual causative agent for viral encephalitis?

Arboviruses

What is a key characteristic of pathogens which cause viral encephalitis?

Production of nucleotide triphosphate that degrades host cell DNA for use by virus

T/F: Humans are the end-stage host for viral encephalitis infections.

T

Up to _____ of poliomyelitis cases are asymptomatic.

90%

Which infection can result in paralytic disease, and in severe cases paralysis of respiratory muscles?

Poliomyelitis

Which disease became more prevalent as sanitation increased?

Poliomyelitis

Which serotype of poliovirus is still circulating today?

Type 1

What is the causative agent of poliomyelitis?

Picornaviridae

How does poliovirus enter the body?

• Via the mouth; infection of throat and intestinal tract and invades bloodstream

• Rarely enters CNS; effects are peripheral

T/F: First infection of poliovirus later in life is more likely to result in paralytic disease.

T; no maternal antibodies in circulation

What is the difference in immunity for the sugar cube vaccine and injectable vaccine for polio?

Mucosal immunity vs. blood-borne immunity

Which vaccine most effectively cuts down on community transmission of poliovirus?

Sabin (sugar cube) vaccine

Which polio vaccine used a weakened live virus?

Sabin vaccine

Which polio vaccine used an inactivated poliovirus?

Salk vaccine; provided strong protection against paralytic disease

Which virus has a bullet-shaped appearance?

Rabies

Symptoms of rabies begin _______ after infection.

2-3 months

What are the two later stages of rabies?

• Encephalitic

• Paralytic

What form of rabies is characterized by increased salivation and difficulty swallowing?

Encephalitic rabies

Which form of rabies is characterized by flaccid paralysis and is less common and dramatic?

Paralytic rabies

T/F: If rabies is not treated before neurological symptoms begin, it will always result in death.

T

Rabies can be identified by ______ at site of viral entry.

Paresthesia

Replication of rabies virus in brain tissue results in formation of __________.

Inclusion bodies (Negri bodies)

Retrograde transport is observed in ______.

Rabies; virus travels backward along the axon to the cell body

Rabies is most often a result from ___ bites in areas without regular vaccination.

Dog

T/F: Treatment for rabies can be administered at any point after infection.

F; treatment is only effective if given BEFORE symptoms appear

What is an opportunistic fungal infection that often appears in HIV patients?

Cryptococcal meningoencephalitis

What is the causative agent of cryptococcal meningoencephalitis?

C. gattii

How does C. gattii persist in a host?

• Antiphagocytic capsule

• Production of melanin (antioxidant)

  • Lowers ROS and RNS

  • Covers activators of immune system (PAMPs)

• Production of urease

  • Blocks digestion by phagolysosome via pH increase

How does C. gattii enter a host?

Inhaled into lungs, where they are taken up by alveolar macrophages and multiply and eventually escape

What is the most common infection outside the lung?

Meningoencephalitis

T/F: Meningoencephalitis can be transmitted person-to-person.

F

What treatments are available for meningoencephalitis?

No vaccine; success w/ antifungal amphotericin B except in AIDS patients

What are the two forms of sleeping sickness?

• Gambiense

• Rhodesiense

What is the vector for sleeping sickness?

Tse Tse flies

What are key characteristics of trypanosomes?

• Antigenic variation

• Trans splicing and GPI anchors

• Mitochondrion and RNA editing

T/F: Trypanosomes are highly susceptible to antibodies and complement.

T

T/F: Trypanosomes can thrive in a host for a year or longer.

T; they are extracellular organisms

How do trypanosomes proliferate for so long in a host?

Characteristic waves of parasitemia; peaks every 5-7 days

How does trypanosomiasis maintain a population?

Antigenic variation; each wave represents a different variant

T/F: The surface coat of a trypanosome is made up almost entirely by a single protein.

T; Variant Surface Glycoprotein (VSG)

VSG is anchored into the membrane via a _______.

Glycolipid anchor

GPI anchor addition occurs immediately after ______

Translation

What portion of the protein serves a signal sequence in GPI anchoring?

C-terminal hydrophobic portion

____ are present on the surface as dimers.

VSGs

What is the only conservation detected in the outer domain of VSGs?

Position of cysteines

T/F: Only a single VSG can be detected at a time.

T

Regulation of promoter activity is used to control _________.

Gene expression

Transcription in trypanosomes is __________.

Polycistronic; more than one distinct protein

What is the difference between cis-splicing and trans-splicing?

Trans-splicing combines different RNA transcripts

What specific molecules acts to ensure the expression of only a single VSG at a time?

J (a-glucosyl-hydroxy-methyluracil)

In most cells mRNA is transcribed by Pol II, but VSG is transcribed by ______.

Pol I

What is Pol I generally responsible for transcribing?

Ribosomal RNA

What toxin can be used to inhibit Pol II?

a-amanitin

What diseases cause rare and mysterious chronic brain diseases in animals and humans?

Prion diseases

What disease is commonly known as “mad cow disease”?

Bovine spongiform encephalopathy (BSE)