Comparing a lternative vaccination schedules to control PRRS

Recent information about alternative vaccination schedules to control (first step before eradication) PRRS in pig farm

Comparing alternative vaccination schedules to control PRRS

I. Díaz, M. Gimeno, A. Callén, J. Pujols, S. López, C. Charreyre, F. Joisel, E. Mateu & T. Jirásek(tomas.jirasek@mevet.cz)

EXPERIMENT 1: Development of PRRSV-specific immune responses after repeated PROGRESSIS®

immunizations

IV IV IV

MLVIV IV

MLV

EXPERIMENT 2: Development of PRRSV-specific immune responses after attenuated vaccine (MLV) primo-immunization followed with a MLV or PROGRESSIS® recall vaccination

IV = Progressis®Ch= Challenge. Strain2749, EU type. ORF5 99% similar to LV

Evaluation of the humoral responses:

• PRRSV-specific total antibodies (ELISA IDEXX)• PRRSV-specific neutralizing antibodies (VNT)

Evaluation of the cell-mediated immune response:

• PRRSV-specific IFN-γ-secreting cells (IFN-γ-SC)

(n=21) Months of age

GROUP 1,5 2,5 3,5 4,5 5,5 6,5 7.5 (+0) +21

A - IV IV - - IV CH END

B IV IV - - IV IV CH END

C - - - - - - CH END

Experiment 1. Development of PRRSV-specific immune responses after repeated

PROGRESSIS® immunizations

TOTAL ANTIBODIES (ELISA Idexx)

0

0,2

0,4

0,6

0,8

1

1,2

1,4

1,6

1,8

2

-7 PI 0 PI +7 PI +14 PI + 21 PI

S/P

ratio

A B C

Months of age

Group 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5

A IV IV IV Ch END

B IV IV IV IV Ch END

C Pl Pl Pl Ch END

Positive pigs

Day +0 Day +7

Group A 5/7 7/7

Group B 4/7 5/7

Group C 0/7 0/7

Challenge

Months of age

Group 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5

A IV IV IV Ch END

B IV IV IV IV Ch END

C Pl Pl Pl Ch END

Months of age7.5 (0 dpi) 14 dpi 21 dpi

A1/71

7/7a

3.7 ± 0.57/7

4 ± 0.6a

B3/7

2.3 ± 0.67/7a

3.8 ± 1.57/7

4.6 ± 0.8a

C0/7

-2/7b

4 ± 06/7

3 ± 0.9b

NEUTRALIZING ANTIBODIES (VNT)

PROPORTION OF POSITIVE PIGSMEAN TITRES (log2) ± STAND. DEV.

∅

PRRSV

∅

PRRSV

ELISPOT IFN-γ

CELL-MEDIATED IMMUNITY (ELISPOT IFNγ)

PRR

SV-s

peci

fic IF

N-γ

-SC

/ 10

6 PB

MC

Challenge1.5 2.5 3.5 4.5 5.5 6.5 7.5 (+0

PI)+7 PI +14 PI +21 PI

0

25

50

75

100

125

150

175

A B C

a

b

a

a

a

b

a

b

c

a†

b

a‡

Months of age

Group 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5

A IV IV IV Ch END

B IV IV IV IV Ch END

C Pl Pl Pl Ch END

Development of PRRSV-specific immune responses after repeated PROGRESSIS®

immunizations

IV IV IV

1. Repeated IV immunizations increased cell-mediated immunity and neutralizing antibodies –after the second immunization-.

2. Development of cell-mediated immunity are supposed to be T helper cells and cytotoxic T-cells (Piras et al., 2005). The pattern observed in the present study agreed with the development of memory cells.

3. After the challenge, IV vaccinated pigs showed a significant increase in the neutralizing antibodies production –in proportion of positive pigs and in mean titres-.

VACCINATION SCHEDULE BALANCE SAFETY/EFICACY

(n=32) Months of age

GROUP 1,5 4,5 5,5 6,5 7,5

A MLV IV - CH END

B MLV MLV - CH END

C MLV IV IV CH END

D - - - CH END

EXPERIMENT 2: Development of PRRSV-specific immune responses after attenuated vaccine

(MLV) primo-immunization followed with a MLV or PROGRESSIS® recall vaccination

IV = Progressis®Ch= Challenge. Strain2749, EU type. ORF5 99% similar to LV

Evaluation of the humoral responses:• PRRSV-specific total antibodies (ELISA IDEXX)• PRRSV-specific neutralizing antibodies (VNT)

Evaluation of the cell-mediated immune response:• PRRSV-specific IFN-γ-secreting cells (IFN-γ-SC)

Virological analysis• Viremia by RT-PCR (+0,+3,+7,+14,+21)

(n=32) Months of age

GROUP 1,5 4,5 5,5 6,5 7,5

A MLV IV - CH ENDB MLV MLV - CH ENDC MLV IV IV CH ENDD - - - CH END

0

0,4

0,8

1,2

1,6

2

2,4

2,8

3,2

1,5 2,5 3,5 4,5 5,5 6,5 END

S/P

ratio

ABCD

Challenge

TOTAL ANTIBODIES (ELISA Idexx)

Months of age4,5 5,5 6,5 (0 dpi) 14 dpi

AMLV+IV

1/81 ± 0

2/8ab

2 ± 1.45/8a

2.8 ± 0.88/8a

3.2 ± 0.7ab

BMLV+MLV

0/8-

4/8a

1.5 ± 15/8a

1.6 ± 0.97/8ab

2.1 ± 1.3b

CMLV+IV+IV

3/81 ± 0

5/8a

1.4 ± 0.5 6/8a

2.2 ± 1.68/8a

3.6 ± 1.2a*

DCONTROL

0/8-

0/8b

-0/8b

-4/8b

2.2 ± 0.5b

PROPORTION OF POSITIVE PIGSMEAN TITRES (log2) ± STAND. DEV

(n=32) Months of age

GROUP 1,5 4,5 5,5 6,5 7,5

A MLV IV - CH END

B MLV MLV - CH END

C MLV IV IV CH END

D - - - CH END

NEUTRALIZING ANTIBODIES (VNT)

(n=32) Months of age

GROUP 1,5 4,5 5,5 6,5 7,5A MLV IV - CH ENDB MLV MLV - CH ENDC MLV IV IV CH ENDD - - - CH END

1,5 2,5 3,5 4,5 5,5 6,5 (+0 PI) +7 PI +14 PI +21 PI0

25

50

75

100

125

150

175

200

A B C

PRR

SV-s

peci

fic IF

N-γ

-SC

/ 10

6 PB

MC

a

a

b

c

a

ab

b

c

a†

b

ab†

b

a

ab

b

aa

b

b

b

MLVPrimo-immunization

Re-vaccination

Challenge

CELL-MEDIATED IMMUNITY (ELISPOT IFNγ)

(n=32) Months of age

GROUP 1,5 4,5 5,5 6,5 7,5

A MLV IV - CH END

B MLV MLV - CH END

C MLV IV IV CH END

D - - - CH END

A 0 3 79 - - +12 - - -15 - - +18 - - -21 - - -24 - + -27 - - -30 - - -

VIREMIA by RT-PCR

B 0 3 7 10 - - -13 - - -16 - - +19 - - -22 - - -25 - - -28 - - -31 - - -

C 0 3 7 11 - - -14 - - -17 - - -20 - - -23 - + -26 - + -29 - - -32 - - -

D 0 3 7 1 - + -2 - + -3 - + -4 - + -5 - + -6 - + +7 - + -8 - + -

No significant differences among

vaccinated groups

Development of PRRSV-specific immune responses after attenuated

vaccine (MLV) primo-immunization followed with a MLV or

PROGRESSIS® recall vaccination

After a MLV primo-immunization:

1. IV re-vaccination induced a significant increase in the development of cell-mediated immunity (anamnestic response).

2. After the challenge, MLV+IV+IV group developed the highest PRRSV-specific immune responses (cell-mediated immunity and neutralizing antibodies).

3. All the vaccination schedules reached similar levels of protection.

MLV

IV IV

MLV

VACCINATION SCHEDULE BALANCE SAFETY/EFICACY