The document discusses various aspects of acquired immunity to bacteria, viruses, protozoa, and helminths. It describes the mechanisms of both innate and adaptive immunity. For bacteria, the key immune responses are neutralization of toxins, killing bacteria through antibodies and complement, and opsonization leading to phagocytosis. Viruses can evade the immune response through antigenic variation and by inhibiting interferons and antibodies. Immunity to protozoa and helminths involves both humoral and cell-mediated responses, though parasites have developed mechanisms to avoid these defenses.

1. Acquired Immunity to Bacteria
and Related Organisms
Pakawadee Kumpolngam D.V.M.

2. • Acquired immunity
– Immunity to Toxigenic Bacteria
– Immunity to Invasive Bacteria
– Immunity to Intracellular Bacteria
– Modification of bacterial disease by immune responses
• Evasion of the immune response
– Prevention of recognition
– Resistance to effector mechanisms
• Adverse consequences of the immune responses
• Serology of bacterial infections
• Immunity to fungal infections

3. Acquired-immune responses to bacterial
infection
There are 5 basic mechanisms
• Neutralization : toxins or enzymes by antibody
• Killing bacteria : antibodies and complement
• Opsonization : by antibodies and complement, resulting
phagocytosis and destruction
• Intracellular destruction : by activated macrophages
• Direct killing : by cytotoxic T cells and NK cells

4. Acquired immunity
The mechanisms by which the immune responses can protect the body against
bacterial invasion.

5. Acquired immunity
• Immunity to Toxigenic Bacteria
– Toxigenic bacteria such as B. anthracis
– Immune response eliminate bacteria and
neutralize their exotoxins
– Neutralization : Antibody prevents Toxin from
binding to its receptors on a target cell.
– Once the toxin has combined with receptors,
antibodies ineffective in reversing this
combination.

6. Immunity to Invasive Bacteria
• Alternative or lectin pathways : innate defense mechanisms
-> MAC -> Lysis
• Antibody and Complement activate Classical pathway to
destroy bacteria -> MAC -> Lysis
• Antibodies or C3b against surface antigens of Bacteria :
capsular (K) antigen or cell wall (O) antigen
– Antibodies or C3b act as opsonins
• Opsonization : antibodies and complement against bacteria
resulting phagocytosis by neutrophils and macrophages
• Bacteria are either opsonized or lysed

7. Immunity to Intracellular Bacteria
• Bacteria can evade intracellular destruction

8. Immunity to Intracellular Bacteria

9. Evasion of the immune response
1. Avioding antibody
- Change protein surface
- Produce protease destroy Ab.
2. Avoiding phagocytosis
- Capsule protect macrophage
- Produce protein interfere macrophage function
3. Avoiding complement
4. Inhibit the expression of MHC I and II on DC surface

10. Immunity to Intracellular Bacteria
IFN-γ
IL-2
The type of immune response stimulated by bacteria depends on whether the
bacteria are live or dead and whether they grow inside or outside cells.

11. Acquired immunity :
Johne’s disease
(Mycobacterium paratuberculosis)
• Modification of bacterial disease
by immune responses
A.Lepromatous form
-poor cell-mediated response
-very high antibody levels
-lesion contain so many bacteria
B.Tuberculoid form
-intense cell-mediated response
-minimal antibody response
-lesion contain very few bacteria

12. Modification of bacterial disease by immune
responses
Immune response can swing between Th1 and Th2 response, perhaps several times,
this variation appears to be a common feature of chronic infection such as tuberculosis.

13. Adverse consequences of the immune
responses
• The adverse consequences of the immune responses
correspond in their mechanism to the
Hypersensitivity types described in next chapter.
For example
– a local Type I hypersensitivity
– Type II cytotoxic reaction
– Type III immune complex reaction

14. Serology of bacterial infections
• Detecting the specific antibodies
– Bacterial agglutination tests

15. Immunity to fungal infections
• Innate immunity
– Phagocytosis by
neutrophils and
macrophages
– γδ T cells at epithelium
– NK cells
• Adaptive immunity
– Th1 response
– Opsonization : antibody
induce phagocytosis

16. Acquired Immunity to Viruses

17. Acquired Immunity to Viruses
• Virus structure and antigens
• Pathogenesis of virus infections
• Immunity to virus
• Evasion of the immune response by virus
• Adverse consequences of immunity to viruses
• Serology of viral diseases

18. Virus structure and antigens
• Viral antigens
Nucleic acid core
Capsid protein
Envelope
– Lipoprotein
– Glycoprotein
• Cannot grow or
reproduce without host
cell

19. Innate immunity to Viruses
• Interferons
The sequential production of interferon and antibody following intranasal
vaccination of calves with infectious bovine rhinotracheitis vaccine. (From
data kindly provided by Dr. M savan.)

20. Innate immunity to Viruses
1. Interferons
• Type I IFN : IFN α, β, τ and δ
• Type II IFN : IFN γ (gamma)
• IFN α/ß are released from virus-infected
cells or plasmacytoid DCs
– stimulate autocrine and
paracrine into antiviral stages
• IFN γ released from NK cells and
Th1 cells
– stimulate cytotoxic T cells and
Macrophages

21. Innate immunity to Viruses
2. NK cells
• NK cells cytotoxicity is stimulated by IFN α
• NK cells produce IFN γ -> antiviral effect
• NK cells reduce severity of viral infection before the
development of acquired immunity

22. Immunity to virus
 Antibody-Mediated Immunity
 Cell-mediated Immunity
 Interferons
 NK cells

23. Immunity to virus

24. Evasion of the immune response
by viruses
• Inhibition of Humoral immunity
– They undergo mutation, selection and change the
structure of their hemagglutinins and neuraminidases :
H16 N9 (2011)
– Antigenic drift / Antigenic shift (Antigenic variation)
• Interference with Interferons and Antibody
• Inhibition of Apoptosis
– Virus can replicate in infected cells
• Inhibition of Cytotoxic T cells and NK Cells
– Inhibit mature DCs and induce DCs dead
• Latency : HIV

25. Inhibition of Humoral immunity

26. Adverse consequences of immunity to
viruses
• Infectious canine hepatitis
– Canine adenovirus 1
• Feline Infectious Peritonitis (FIP)
– Coronavirus

27. Adverse consequences of immunity to
viruses
 Infectious canine hepatitis

28. Adverse consequences of immunity to
viruses
 Feline Infectious
Peritonitis (FIP)
 Immune-complexes
deposite in serosal
blood vessel causing
 Pleuritis
 Peritonitis
 Glomerulonephritis

29. Serology of viral diseases
• Test to detect and identify Viruses and
Antibodies
– Immunofluorescence
– ELISA
– HA, HI
– Gel precipitation
– Western blotting
– Complement fixation
– Virus neutralization

30. Immunity to Parasites
http://www.huldaclarkzappers.com/php2/therapies.php

31. Immunity to Parasites
• Immunity to Protozoa
– Innate immunity
– Acquired immunity
– Evasion of the immune response
– Adverse consequences
– Vaccination

32. Immunity to Protozoa
Innate immunity
• In vertebrates, extracellular protozoa are eliminated
by phagocytosis and complement activation.
• T cell responses.
- Extracellular protozoa - Th2 cytokines released for
antibody production.
- Intracellular protozoa - Cytotoxic lymphocytes
(CTL’s) kill infected cells. Th1 cytokines produced
to activate macrophages

33. Immunity to Protozoa
Acquired immunity
• Antibody responses.
- Extracellular protozoa are eliminated by
opsonization, complement activation and
ADCC.
- Intracellular protozoa are prevented from
entering the host cells by a process of
neutralisation e.g. neutralising antibody
against malaria sporozoites, blocks cell
receptor for entry into liver cells.

34. Immunity to Protozoa
• Acquired immunity
• Th1 response for
intracellular parasite
• T. gondii tachizoites
grow within cells, the
infected cell rupture
and tachizoites are
released to invade
other cells.

35. Immunity to Protozoa
• Acquired immunity
The points in the life cycle of
Toxoplasma gondii at which
the immune system can exert
a controlling influence.

36. Immunity to Protozoa
• Evasion of the immune response
1. Avoid antibody
- Trypanosomes with a new surface glycoprotein antigen
2. Avoid neutrophil attachment and phagocytosis
- T. gondii inhibit lysosome-phagosome fusion
3. Many protozoa are immunosuppressive
- Plasmodium suppress DCs to process antigen

37. Immunity to Protozoa
• Adverse consequences
Hypersensitivity types
– Type I hypersensitivity
– Type II cytotoxic reaction
– Type III immune complex reaction
– Type IV hypersensitivity reaction

38. Immunity to Protozoa
• Vaccination
Successful vaccination against protozoan
infections of domestic animals is currently
limited to coccidiosis, babesiosis, giardiasis
and theileriosis

39. Acquired Immunity to Parasites
• Immunity to Helminths
– Humoral immunity
– Eosinophils and Parasite destruction
– Cell-mediated immunity
– Evasion of the immune response
– Vaccination

40. Immunity to Helminths
• Most helminths extracellular & too large for
phagocytosis.
• For the larger worms, e.g. some gastrointestinal
nematodes host develops inflammation and
hypersensitivity.
• Eosinophils & IgE activated to initiate inflammatory
response
• Mast cells release histamine elicited reactions are
similar to allergic reactions.

41. Immunity to Helminths
• Humoral immunity
The mechanisms involved in the self-cure reaction against intestinal helminths.

42. Immunity to Helminths
• Horse skin allergy by
migrating parasitic
helminth larvae.
• Eosinophils presence
• Type I hypersensitivity

43. Immunity to Helminths
• The factors involved in the
activation of eosinophils
– Granulocyte-macrophage
colony-stimulating factor
(GM-CSF)
– EAF ; Eosinophil Activating
Factor
– PAF ; Platelet-Activation
Factor

44. Immunity to Helminths
• Eosinophils and Parasite destruction
Some of the molecules released from eosinophils that
cause damage to parasitic helminths.

45. Immunity to Helminths
• Eosinophils and Parasite destruction
Some effects of the immune responses on the stages of helminth development.

46. Immunity to Helminths
• Cell-mediated immunity

47. Immunity to Helminths
• Evasion of the immune response

48. Immunity to Helminths
• Vaccination
– Traditional vaccines little use
– Recombinant T. ovis vaccine can induce protective
immunity in seep
• Prevention
– Control or prevent an infestation of helminths
– Treat by drug

49. Antibody function and immune response to organisms

50. Acquired Immunity to Parasites
• Immunity to Arthropods
– Demodectic Mange
– Flea-Bite dermatitis
– Tick infestation
– Hypodermal infestation

51. Immunity to Arthropods
Demodectic Mange
• T cell response
• Infiltrating lymphocytes
• Granuloma formation
• Type I,IV hypersensitivity
reaction

52. • Flea-Bite dermatitis
© 2013 Campus Veterinary Clinic

53. Immunity to Arthropods
• Tick infestation
www.parasiticpests.com

54. Immunity to Arthropods
• Hypodermal infestation
• Hypodermin A, the
protease secreted by
larvae
• inhibit immune
responses and reduce
IL-2

55. Reference
• Tizard, I. R., 2009. Veterinary Immunology an
introduction. 8th. Elsevier Saunders.
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