1. Rotavirus
Presented by Group PCL2

2. Group 7 members: NSABIMANA Venuste 12113664 NYAZIYOSE Ignace 12113538
NZABONIMPA Clarisse
NZIYOMAZE Elie
NZAHUMUNYURWA Donat
RUGIRA Vive
RUKAMBA Jean de Dieu
SHABELI Philippe
SHEMA Origène
SIMBI Credo Sylvie
TSEMO Tagne Sandrine
TUYISENGE Elius

3. Family Reoviridae Genus Rotavirus

4. Introduction
Diarrheal disease has been recognized in humans since antiquity.
Until the early 1970s, a bacterial, viral, or parasitic etiology of diarrheal disease in children could be detected in fewer than 30% of cases
In 1973, Bishop and colleagues observed a virus particle in the intestinal tissue of children with diarrhea by using electron micrography.
This virus was subsequently called “rotavirus” because of its similarity in appearance to a wheel (rota is Latin for wheel).

5. Introduction First isolated in 1973 from children with diarrhea
EM identification from duodenal biopsies
Human and animal strains are anti-genetically distinct, and animal strains rarely cause infection in humans.

6. Introduction cont’ 60-80nm in size Non-enveloped virus
Double capsid virus
EM appearance of a wheel with radiating spokes
Icosahedral symmetry
double stranded (ds) RNA in 11 segments

7. Classification Groups, subgroups,
serotypes based on viral capsid proteins :
7 Groups (A through G)
Group A is the most common and has 2 subgroups
10 human serotypes based on G protein (VP 7) Classification of rotaviruses is grouped into serogroups and then serotypes , 7 antigenetically different
sero-groups – A-G

8. Group A rotaviruses
Group A rotaviruses • Cause most human disease – Further subdivided into subgroups • Principal etiologic agent of severe gastroenteritis in infants and young children • Responsible for 1 billion cases of severe diarrhea • Major cause of mortality among the young
Cause most human disease
Further subdivided into subgroups
• Principal etiologic agent of severe gastroenteritis in infants and young children
• Responsible for 1 billion cases of severe diarrhea
Major cause of mortality among the young

9. Other Rotaviruses
• Group B – Adult diarrhea • Group C – Primarily veterinary pathogens • Groups D, E, F, G – Only known to infect animals

10. Epidemiology - Worldwide
Millions are affected
600, ,000 deaths/year
A major cause of diarrhea-associated hospitalizations
Seroprevalence studies show that antibody is present in most by age 3.

11. Rotavirus- Worldwide distribution

12. Estimated Global Distribution of The 800,000 Annual Deaths
Caused By Rotavirus Diarrhea
. prevalent area

13. Epidemiology : U.S No. of children under 5y. affected ~ 2.7 million
Physician visits per year ~ 500,000
Hospitalizations per year ~ 50,000
Deaths per year ~
% cases w/ dehydration ~ 1-2.5%

14. Epidemiology
Age- 4months - 2 years Protection of younger infants through transplacental antibody transfer
Asymptomatic infections are common, especially in adults
Nosocomial infections
Outbreaks

15. Epidemiology Seasonality Winter months (Nov. through May in US)
Gradual spread W to E
Year-round in the tropics
Incubation period - thought to be <4 days

16. EPIDEMIOLOGY Differences in Groups
Group A infections are most common in human
Group B has been associated with outbreaks in adults in China
Group C is responsible for sporadic cases of diarrhea in infants around the world

17. Pathogenesis
Targeted host cells- mature enterocytes lining the tips of intestinal villi
Intermediate/infective sub-viral particle (ISVP) produced through proteolysis enter host cell by endocytosis

18. Structure Double capsid (outer and inner capsid) Core with genome
Capsid is cleaved by trypsin to form
ISVP- infective sub-viral particle

19. Rotavirus- EM Structure

20. Rotavirus- 3d structure

21. ROTAVIRUS- ultrastructure

22. Rotavirus- details of EM structure

23. Viral Structural Proteins (VP)
Outer structural proteins - VP7 and VP4
VP7=glycoprotein
VP4=protease-cleaved, P protein, viral hemagglutinin, and forms spikes from the surface
Inner core structural proteins VP 2, 3, 6
VP6 is an important antigenic determinant
VP4 determines how virulent the virus is and it determines the P-type of the virus.

24. Genome is composed of 11 segments of double-stranded RNA coding for six structural and five nonstructural proteins
Seven serological groups have been identified (A-G), three of which (groups A, B, and C) infect humans .

25. Nonstructural viral proteins
NSP1, the product of gene 5, is a nonstructural RNA-binding protein.
NSP2 is an RNA-binding protein that accumulates in cytoplasmic inclusions (viroplasms) and is required for genome replication.
NSP3 is bound to viral mRNAs in infected cells and it is responsible for the shutdown of cellular protein synthesis.

26. NON STRUCTURE PROTEINS
NSP4 is a viral enterotoxin to induce diarrhoea and was the first viral enterotoxin discovered.
NSP5 is encoded by genome segment 11 of rotavirus A and in virus-infected cells NSP5 accumulates in the viroplasm.
NSP6 is a nucleic acid binding protein, and is encoded by gene 11 from an out of phase open reading frame.

27. ROTAVIRUS Structure

28. Gene coding assignment

29. Rotavirus - Properties
Virus is stable in the environment Relatively resistant to hand washing agents Susceptible to disinfection with 95% ethanol, ‘Lysol’, formalin

30. Replication There are two possible ways of entry in the cell:
Direct penetration of the virion across the plasma membrane
Endocytosis

31. Early events
Early transcription, translation, and assembly of double-layered particles.
Some of the (+) RNA that is synthesized functions as mRNA . NSP2 and NSP5 play roles in the assembly of viroplasms, where cores are assembled from VP1, VP2 and VP3.
Some of the (+) RNA functions as templates for synthesis of (−) RNA.
VP6 is added to the core to form a progeny double-layered particle.

32. Late events Late transcription, translation and virion assembly.
NSP4 is synthesized in the endoplasmic reticulum,where it binds VP4 and a double-layered particle .
This complex buds into the endoplasmic reticulum, where the final stages of assembly occur.
VP7, also synthesized in the endoplasmic reticulum, is added to form the outer
layer of the capsid and the VP4 spikes are added.
Virions are released from the cell either by lysis or by exocytosis

34. Clinical Features Incubation period - thought to be <4 days
Fever- can be high grade (>102F in 30%)
Vomiting, nausea precede diarrhea
Diarrhea
- usually watery (no blood or leukocytes)
- lasts 3-9 days
- longer in malnourished and immune deficient indiv.
- NEC and hemorrhagic GE seen in neonates

35. Histopathology
Mature enterocytes lining the tips of intestinal villi are affected Villous atrophy and blunting Death of the mature enterocytes

36. Histopathology Infiltration of lamina propria with mononuclear cells
Repopulation of the villous tips with immature secretory cells [crypt hyperplasia]

37. Histopathology

38. Mechanism of diarrhea
Watery diarrhea due to net secretion of intestinal fluid
Activation of the enteric nervous system - possible role of enterotoxin

39. Clinical Features (contd.)
Dehydration is the main contributor to mortality.
Secondary malabsorption of lactose and fat, and chronic diarrhea are possible

40. CONT’
Recovery is usually complete.
However, severe diarrhea without fluid and electrolyte
replacement may result in dehydration and death .

41. Immunological Aspects
Immunoglobulin (Ig A) , in the lumen of the gut immunity
to infection .
Actively or passively acquired antibodies (including antibodies in
colostrum and mothers milk) lessen the severity of disease
but does not consistently prevent reinfection .
Absence of antibody small amounts of virus infection
and diarrhea .

42. Diagnosis
Antigen detection in stool by ELISA, Latex Agglutination (for Group A rotavirus)
EM- non-Group A viruses also
Culture- Group A rotaviruses can be cultured in monkey kidney cells
Serology for epidemiologic studies

43. Transmission Mainly person to person via fecal-oral route Fomites
Food and water-borne spread is possible
Spread via respiratory route is speculated

44. Treatment and Prevention
Supportive - oral, IV rehydration
Prevention
Hand washing and disinfection of surfaces

45. Rotavirus vaccine • Rotarix which is the latest(licensed in 2008)
RotaTeq(Rhesus rotavirus tetravalent vaccine) licensed in 2006
– Serotypes 1, 2, 3, 4 for VP7
– Reassortant strains
– Protective against 80% of the cases of severe diarrhea, 100% of the dehydration cases
Rotashield
• Was recommended at 2, 4 and 6 months of age
• Risk of intussusception (a bowel blockage that is treated in a hospital and may require surgery) 1 in 12,274 infants

46. REFERENCES Links: www.ncbi.nih.gov/pmc
Book:
Lange microbiology and Immunology review (10th Edition)

47. THANK YOU FOR YOUR KIND ATTENTION !!!