CNS Viruses -- Togaviridae -- Alphaviruses and Rubiviruses

Question 1

What is the structure of the Togaviridae?

Answer 1

Small, enveloped, nonsegmented, + strand RNA

Question 2

What are the three genera of alphaviruses you need to know?

Answer 2

Western Equine Encephalitis (WEE), Eastern Equine Encephalitis (EEE), Venezuelan Equine Encephalitis (VEE)

Question 3

How do alphaviruses get into the cell?

Answer 3

Receptor-mediated endocytosis, pH-dependent exit from endosome

Question 4

What does their translated RNA transcript form?

Answer 4

Single large polyprotein

Question 5

How do alphaviruses get out of the cell?

Answer 5

Budding from plasma membrane

Question 6

Where do alphaviruses initially replicate in humans?

Answer 6

Muscle and fibroblasts of numerous organs

Question 7

After initial replication, what disease course do alphaviruses take?

Answer 7

Low level viremia with simultaneous CNS invasion

Question 8

How long do symptoms last before encephalitis ensues?

Answer 8

2 weeks

Question 9

Is there a vaccine for alphaviruses?

Answer 9

No and yes; VEE for lab workers; vaccines for horses