1. EGG INOCULATION Principles Practice and Vaccine Development
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EGG INOCULATION Principles Practice and Vaccine Development

2. Towards Developing Better Skills in Microbiology
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Towards Developing Better Skills in Microbiology
Egg inoculation continues to be a Important Student Exercise in Several Post Graduate Examinations in Medical Microbiology for evaluation. The Students should develop the Necessary skills to be familiar with the exercise in Virology

3. Viruses are Different From Other Microbes
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Viruses are Different From Other Microbes
Viruses are obligate intracellular parasites. They depend totally on their host cells for their existence. Their total host dependence makes it extremely difficult to get good insight of them natural conditions, because the internal characteristics of the host cells are likely to interfere with the observations. Due to these reasons, it has been found desirable that viruses are cultivated or grown in the laboratory itself.

4. Difficulties in Diagnosis of Viral Infections
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Difficulties in Diagnosis of Viral Infections
Can not be seen under light microscope
Can not be cultivated easily
Do not grow on culture media
Treatment was not available
Changed situation
Rapid techniques have emerged
Screening for Blood transfusion
Treatment available

5. Techniques used Microscopy Detection of Viral Antigen
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Techniques used
Microscopy
Detection of Viral Antigen
Growing and detecting viruses in
Tissue / Organ / Cell culture
Fertilized hen’s egg
Laboratory animal inoculation eg mice
Detection of antibody in serum
IgG – Rising titer in paired sample
IgM – Indicates current / recent infection

6. Microscopy  Electron Microscope / Immune Electron Microscopy
Light microscope – Inclusion bodies eg Negri Body in Rabies
Fluorescent Microscope -Fluorescent antibody technique

7. Demonstration of Viral Antigens
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Demonstration of Viral Antigens
Precipitation on gel eg HBsAg
Immunofluorescence
Counter Immuno Electro Phoresis (CIEP)
Enzyme Linkes Immuno Sorbant Assay (ELISA)
Dr.T.V.Rao MD

8. Isolation of Virus  Laboratory animals Fertilized Hen’s Egg
Chorioallantoic membrane
Allantoic cavity
Amniotic cavity
Yolk sac
Organ/Tissue/Cell Culture
Growth identified by serological method like neutralization.

9. Virus Culture  Embryonated Egg Cell Lines/ Tissue cultures
Chorioallantioc membrane (CAM)
Allantoic cavity
Amniotic cavity
Yolk Sac
Cell Lines/ Tissue cultures
Primary
Diploid/ Secondary
Continuous
Animal inoculation
Suckling mice

10. Embryonated Hen’s Egg Cultivation of Viruses and Bacteria
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Embryonated Hen’s Egg Cultivation of Viruses and Bacteria
Chorioallantoic membrane (CAM) – visible lesions called pocks. Each infectious virus particle forms one pock. e.g. Variola, Vaccinia virus
Allantoic cavity – Influenza virus (vaccine production) & paramyxoviruses
Amniotic cavity – primary isolation of Influenza virus
Yolk sac – Chlamydia, Rickettsia & some viruses

11. 
Embryonated eggs:
The Embryonated hen’s egg was first used for cultivation of viruses by Good Pasteur and Burnet (1931). Cultivation of viruses in organized tissues like chick embryo necessitates a different type of approach.. For all practical purposes they all themselves behave as tissue cultures. The process of cultivation of viruses in embryonated eggs depends on the type of egg which is used. The egg used for cultivation must be sterile and the shell should be intact and healthy.

12. Burnet as Director of the Hall Institute, 1944-1965
F.M. Burnet in the laboratory in the early 1950's, was experimenting on influenza virus genetics, using the developing hen's egg.

13. Burnet Wins Nobel Prize
Burnet was confirmed by the award of the 1960 Nobel Prize to him and Peter Medawar for the discovery of immunological tolerance, a discovery in immunology of minor importance compared with the clonal selection theory.

14. Only Embryonated Eggs Are Suitable for Growing Virus
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Only Embryonated Eggs Are Suitable for Growing Virus
Inoculated eggs are candled daily to see the chicken embryos inside.

15. Eggs are Used for Mass Vaccine Production in Influenza
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Eggs are Used for Mass Vaccine Production in Influenza
Animals and chick embryo were the first method that was used to cultivate virus. This method is rarely used as it is not convenient. However, when preparing for bulk virus, (e.g. antigen or vaccine production) the usage of chick embryo is useful.

16. Advantages of Fertile Eggs
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Advantages of Fertile Eggs
Fertile chicken eggs provide a convenient, space-saving incubator for many kinds of animal viruses.  Different viruses can be injected into an egg at different sites and the egg can be easily observed for viral replication throughout the development of the chicken embryo.

17. Advantages of Using Embryonated Eggs
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Advantages of Using Embryonated Eggs
Isolation and cultivation of many avian and few mammalian viruses
Ideal receptacle for virus to grow
Sterile & wide range of tissues and fluids
Cost- much less
Maintenance-easier
Less labor
Readily available

18. Advantages of Fertilized Eggs are
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Advantages of Fertilized Eggs are
Free from bacteria and many latent viruses. 
Free from specific and non specific factors of defense.

19. Structure and Utility of Fertilized Egg
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Structure and Utility of Fertilized Egg

20. Routes of Injecting the Fertilized Eggs
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22. Cultivation of Virus in Eggs
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Cultivation of Virus in Eggs
To cultivate viruses in eggs, the procedure adopted should be very simple. The eggs are kept in incubator and embryos of 7-12 days old are used. The egg containing embryo usually has an air apace at the larger end. The position of this sac is first determined.

23. Begin you Exercise with Candling Eggs
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Begin you Exercise with Candling Eggs
Candling is the process of holding a strong light above or below the egg to observe the embryo. A candling lamp consists of a strong electric bulb covered by a plastic or aluminum container that has a handle and an aperture. The egg is placed against this aperture and illuminated by the light. If you do not have a candling lamp, improvise. Try using a torch.

24. Marking the inoculation site:
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Marking the inoculation site:
1. Hold the blunt end of the egg against the aperture of the candling lamp and note the position of the head of the embryo.
2. Turn the egg a quarter turn away from the head.
3. Draw a line on the shell marking the edge of the air sac.
4. Draw an X approximately 2 mm above this line.
5. The X marks the inoculation site.

25. Materials Needed for Egg Inoculation
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Materials Needed for Egg Inoculation
Eggs: 9-day old or 10-day old embryonated eggs. Candle the eggs and mark the inoculation sites as described in Section 5. Eggs should be placed in an egg rack with the inoculation site uppermost.
Egg shell punch.
Cotton wool.
A 70 percent alcohol solution in water.
Syringe 1 mL.
Needles preferably 25 gauge, 16 mm.
Stationery tape (also called cello or sticky tape) or melted wax to seal the inoculation site.
Inoculum. This must be free of microbial contamination.
Discard tray.

26. Inoculation of the Allantoic cavity
1. Use cotton wool and 70 percent alcohol to swab the end of the eggs to be inoculated. Allow the alcohol to evaporate.
2. Swab the eggshell punch with 70 percent alcohol solution. Place used cotton wool in discard tray.
3. Pierce a hole in the end of the egg at the marked inoculation site.
4. Attach needle to 1 mL syringe.
5. Draw inoculum into 1 mL syringe.

27. Inoculation of the Allantoic cavity
6 Keeping the needle and syringe vertical, place the needle through the hole in the eggshell. The needle will need to penetrate approximately 16 mm into the egg to reach the allantoic cavity.
7. Inject 0.1 mL of inoculum into the egg.
8. Withdraw the needle from the egg.
9. Seal the hole in the shell with stationery tape or melted wax.
10. Discard the used needles and syringes.
11. Place the inoculated eggs into a second incubator. Check the temperature and humidity of incubate

28. Piercing a hole in the egg shell
A dental drill can be used if it is available. In most laboratories a tool called an eggshell punch can be improvised using materials that are cheap and easy to procure.

29. Routes of Egg Inoculation

30. Inoculating the Specimens
The rest of the embryo then gets exposed and ready for use. Virus suspension to be cultivated is taken in dropper and gently spread over the exposed embryo. After inoculation is thus completed, the open area of the shell is sealed eggs are incubated for one week as in hatching. The virus particles infect the membrane at random and create pock marked appearance against the transparent background. This indicate viral basis.

31. Chorioallantoic membrane (CAM):
CAM is inoculated mainly for growing poxvirus. Herpes simplex virus is also grown. Virus replication produces visible lesions, grey white area in transparent Cam. Each pock is derived from a single virion. Pocks produced by different virus have different morphology. Under optimal conditions, each infectious virus particle can form one pock. Pock counting, therefore can be used for the assay of pock forming virus such as vaccinia.

32. Piercing the Chorioallantoic Membrane
Little holes are drilled through the egg shell for infection of the chorio-allantoic membrane.

33. Can be used in few Fungal Infection
They provide a complex environment, including phagocytic cells, to study fungal host-pathogen interaction, but are of a lower developmental stage than adult mice.

35. Piercing the Shell with Needle

36. Injecting Infective Material with Needle

37. Overview of Inoculating Sites
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Overview of Inoculating Sites

38. 
Allantoic cavity:
Inoculation into the allantoic cavity provides a rich yield of influenza and some paramyxoviruses. Allantoic inoculation is employed for growing the influenza virus for vaccine production. Other allantoic vaccines include Yellow fever (17D strain), and rabies vaccines. Duck eggs are bigger and have a longer incubation period then hen’s egg. They therefore provide a better yield of rabies virus and were used for the preparation of the inactivated non-neural rabies vaccines.

39. ALLANTOIC ROUTE – INOCULATION SITE DETERMINATION
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ALLANTOIC ROUTE – INOCULATION SITE DETERMINATION

40. 
Amniotic cavity:
The amniotic sac is mainly inoculated for primary isolation of influenza a virus and the mumps virus.

41. Amniotic Route of Inoculation
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Amniotic Route of Inoculation

42. 
Yolk sac:
It is inoculated for the cultivation of some viruses as well as for some bacteria like Chlamydia and Rickettsia.

43. 
YOLK SAC ROUTE

44. Influenza Vaccine Development in Fertilized Eggs

45. Influenza Vaccine Traditional Methods- Influenza Examining the infected eggs Vaccine

46. How Vaccines are Produced in Eggs
In egg culture, flu viruses are injected into chicken egg embryos, where they multiply. After several days of incubation a machine opens the egg and harvests the virus, which is then purified and chemically killed. On average it takes one or two eggs to produce a single dose of annual flu vaccine. In cell culture, the virus is grown in animal or human cells, which are available in unlimited supply.

47. How the Reassortant Vaccines for Influenza Produced in Eggs
The egg is inoculated with a mixture of the epidemic influenza virus strain (red) and a standard strain (green) that can replicate in chicken eggs. Both strains replicate themselves, but as they do so their genetic material becomes mixed, producing hybrid viruses known as reassortants

48. Eggs as Tools for Developing Influenza Vaccines
Influenza vaccine manufacture in eggs, computer artwork. Fertilized chicken eggs can be used to produce vaccines against influenza viruses. The reassortants are analyzed, and those which have the epidemic strain surface proteins but other genes of the standard strain will be selected. These are injected into different eggs to replicate before harvesting.

49. Eggs are Used in Mass Scale Development of Vaccines

50. Egg Allergies and Vaccines
No suitable cell culture system exists and egg inoculation is the method of choice.   Influenza virus vaccines are still cultivated in eggs, and hence people with egg allergies cannot tolerate the influenza vaccines.

51. Follow all the Biosafety Considerations
All procedures involving the manipulation of infectious materials are conducted within biological safety cabinets, specially designed hoods, or other physical containment devices, or by personnel wearing appropriate personal protective clothing and equipment.
Dr.T.V.Rao MD