Togaviruses

1. Togaviruses fackrel@uwindsor.ca toga.ppt

2. Toga Viruses • Structure • Classification • Multiplication • Clinical manifestations • Epidemiology • Diagnosis • Control Baron’s Web Site

3. Togaviridiae • Rubivirus-rubella • Alphavirus- Equine Encephalitis, Sindbis • Pestivirus- animal pathogens • bovine viral diarrhea, hog cholera

4. Rubella German Measles (first diagnosed by German doctors) Three day Measles

5. Rubella: Structure • enveloped • icosahedral • ss RNA sense • 40-80 nm • 30 nm core • hemaglutinin peplomers + ssRNA

6. Rubella: Classification • Family Togaviridae • genus Rubivirus only member • single serotype • three structural polypeptides Unlike other Togaviruses rubella is not arthropod borne

7. Rubella: Multiplication • RNA is capped and polyadenylated • serves as mRNA -> nonstructural proteins • sense RNA -> antisense RNA • Antisense RNA template for progeny RNA • antisense RNA--> mRNA -> structural proteins • mature at intracytoplasmic membranes

8. Rubella: Clinical manifestations Postnatal • rash • lymphadenopathy • low grade fever Congenital • stillbirth • spontaneous abortion • birth defects

9. Congential Rubella • Ocular- cataracts, retinitis, glucoma ,microphthalmaia • Heart defects- patent ductus arteriosis • Deafness- cochelar deafness, central auditory imperception • CNS- mental retardation, encephalitis, microcephaly • Other- hepatitis, pneumonitis

10. Rubella: Pathogenesis • respiratory secretions -direct contact, droplet • multiplies in cells of respiratory system • extends to lymph nodes, spleen

11. Congential rubella occurs in unvaccinated susceptible young women Rubella: Epidemiology • worldwide • vaccines licenced 1969 • no new epidemics • incidence ~ 100 /year

12. Rubella: Host defenses • interferon • cell mediate immunity • neutralizing antibodies • hemagglutinin inhibiting antibodies asymptomatic reinfection possible

13. Rubella: Diagnosis • Clinical manifestations- rash, lymphadenopathy • Isolate virus respiratory tract • Detect Rubella IgM

14. Diagnosis: Congenital Rubella • isolate virus - urine, CSF, blood • maternal circulating IgG- lasts 6 months • Detect fetal or neonate IgM

15. Rubella: Control • live attentuated rubella vaccine • mumps-measles-rubella combination • subcutaneous • 15 months of age • asymptomatic in children • mild symptoms in adults

16. Rubella: Control Strategies • 10-20% young women not immunized • Therefore immunize • college students • health care personnel • military personnel • after childbirth, miscarriage or abortion USA data

17. Alphavirus Encephalitis Sindbis

18. Alphaviruses are arthropod borne (arboviruses)

19. Alphavirus: Structure • icosahedral 40-50 nm • enveloped • attachment glycoprotein • ss RNA, sense, monopartite

20. Alphavirus: Classification • common envelope glycoprotein • common capsid antigenic sites • 26 antigenic types

21. Alphavirus: Multiplication • RNA is capped and polyadenylated • serves as mRNA -> nonstructural proteins • sense RNA -> antisense RNA • Antisense RNA template for progeny RNA • antisense RNA--> mRNA -> structural proteins • mature at intracytoplasmic membranes

22. Subgenomic mRNA • sense strand -> antisense strand • 3’ one-third of antisense strand -> mRNA • mRNA -> structural proteins

23. Alphavirus: Clinical manifestations • Encephalitis viruses • fever, malaise, headache and/or encephalitis • Arthritis viruses • fever, rash, arthralgia, arthritis

24. Alphavirus: Epidemiology • mosquito-vertebrate-mosquito cycles • geographically restricted • epizootics- Venezuelan equine enchephalitis • urban epidemics- chikungunya virus • seasonal

25. Alphavirus: Diagnosis • clincal manifestations • known exposure • isolate virus • detect IgM

26. Alphavirus: Control • reduce mosquito populations • vaccinate vertebrate hosts- horses • vaccine humans at high risk of exposure