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SEROLOGY 101

Or How To Interpret Those Funny-Looking

Graphs

Dr. Victoria Bowes

Animal Health Centre

Abbotsford, BC

Presented June 4, 2003

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Avian Immune System

NON-SPECIFIC IMMUNITY:

anatomicskin, mucus, cilia

body temperature

genetic factors

sneeze, cough, vomitage, nutrition

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Avian Immune System

SPECIFIC IMMUNITY:

Passive (provided in the yolk to chicks)

Acquired (must be produced by the bird)

(by infection or vaccination)

Cellslymphocytes, macrophages Antibodies -produced by B-lymphocytes

Memory

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The Immune Response

Must recognizeforeign or potentially

harmful intruders

Produce and co-ordinate specific

(antibodies) and non-specific(lymphocytes)reactions to ATTACH, TRAP and

ELIMINATE

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The Immune Response

antibody: a protein produced in response to

the presence of a specificantigen

antigen: a molecule capable of eliciting animmune response, usually large, complex

and foreign

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The Immune Response

Example:

An IB virus that has its surface receptors

coated in antibodies cannot attach itself to

the cells lining the trachea, the first step in

infection.

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The Immune Response

PRIMARY: novel foreign antigen isprocessed, specific antibodies are slowly

produced (short-lived) and memory cellsbecome dormant

SECONDARY: memory cells encountertheir specific antigen and are activated,antibody production is rapid and potent

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Vaccines

Vaccines = INSURANCE (something you

may never use but you be very glad to have

if ever needed)

Live : gives best immune response but

has side effects (weakened strains of virus)

Killed: less side effects but poorer

immune response (excluding adjuvants)

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Serology

The detection of antibodiesin serum

Test methods: plate agglutination

hemagglutination inhibition

ELISA

Interpreting results: negativevaccination

field challenge

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Blood

55% fluid: mostly water

45% solid: cells (500:1 red : white cells),

enzymes, proteins, nutrients

transports oxygen & nutrients while

removing waste

serum Vs plasma

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The Animal Health Monitoring Lab

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ELISA

E nzyme

L inked

I mmuno

S orbantA ssay

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ELISA

easily automated

sensitive & specific

antigen-coated test plates capturespecific

antibodies in diluted blood sample and

reagents turn shades of blue depending and

the amount of antibody present

generates computer graph histogram

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The Elisa Plate Reader

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ELISA plate

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HI plate

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Serological Strategies

DIAGNOSTIC: field challenge

paired samples

ASSESS VACCINATION RESPONSE:protective and maternal titres

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Serological Strategies

small sample size is used to infer the condition ofa larger population of birds

statistical techniques dictate sample size ofsignificance

variables: flock size 12-24 /air space?

testing type

pooling samples reduces test sensitivity(dilutional)

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Interpretation

Serology results must be interpreted inassociation with other sources of

information: vaccination historyproduction data

condemnation data

cl inical signsnecropsy f indings

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Limitations

seroconversion takes 4-20 days

tests only circulating antibody

static measure (rising, stable, falling)

cant differentiate field vs. vaccine strains

cross-reactions test error

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Titres or Titers

a unit of measurement of antibody

uses pre-determined reference numbers

historically measured by sample dilution

until a standard reaction was produced

dilution = titre

a titre of 32 the antibody of 64

2X the antibody of 16

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Doubling

DilutionsLog Titres

1 0

2 1

4 2

8 3

16 4

32 5

64 6

128 7

256 8

512 9

1024 10

2048 11

Field Challenge Prime Plus Killed

Interpretation

No immunity Maternal Immunity

Poor Immunity

Live Prime Vaccine

2nd Live Prime VaccineProtection Against Mortality

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Interpreting Results

123 A BB 18 X 345 IBD-XR 123flock #

A orB1st or 2nd bleeding BBbroiler breeder (or TU, BR)

18age in weeks

Xsubmitter code (hatchery, vet) 345owner code

IBD-XRtest name

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Interpreting Results

MEAN TITRES:

the averagetitrenumber (zero to >10,000)

each titre group (bottom line of graph)represents a different titre range depending

on the virus

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Titre

Group

Reovirus

MG/MS

IB, IBD

NDV

AE

0 0-537 0-395 0-444

1 538-1075 396-999 445-769

2 1076-1999 1000-1999 770-1215

3 2000-2999 2000-2999 1216-1661

4 3000-3999 3000-3999 1662-2107

5 4000-4999 4000-4999 2108-2553

6 5000-5999 5000-5999 2554-2999

7 6000-7999 6000-7999 3000-3444

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Interpreting Results

UNIFORMITY:

%CV (coefficient of variation)

< 30% excellent

30-50% good

51-80% fair> 81% poor or bimodal

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Standards

Optimum Titres: minimum titre level toprovide long duration immunity for breeder

hens, also assuming protective. Assessed 4weeks post-killed vaccine.

ND 8/10 > 7 IBV 8/10 > 6IBD 8/10 > 8 Reo 8/10 >5

AE 8/10 >4

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Interpretation

EXAMPLES

The following are typical histograms

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5 week unvaccinated broilers

negative titres

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5 week broilers

IBD vaccination or challenge?

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5 week vaccinated broilers

IBD challenge, poor vaccine?

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62 week layer bloods waning titres

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pre & post-killed IBD titres

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pre & post-killed reovirus titres

+ challenge?

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NDV titres

poor prime boosted by killed vaccine

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IBV

uneven prime, suboptimal titres

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