This study evaluated the effect of different PRRSV challenge doses in pigs vaccinated with Ingelvac PRRS MLV. The results showed that vaccinated pigs had reduced viremia, fever, and increased weight gain compared to non-vaccinated pigs across all challenge doses. For vaccinated pigs, challenges at or below 2 log had similar outcomes as non-challenged pigs. Conversely, non-vaccinated pigs saw measurable negative impacts from infection at all challenge doses. The study demonstrated that Ingelvac PRRS MLV vaccination can mitigate the consequences of PRRSV infection and protect pigs depending on challenge dose.

1. Evaluation of PRRSV challenge dose in
vaccinated pigs
AASV Annual Meeting
Technical Partners Session
February 28th, 2016

2. Objective of Study
 Evaluate the effect of PRRSV challenge dose in
Ingelvac PRRS® MLV vaccinated pigs in a
respiratory challenge model

3. Primary Objective:
Question?
 In vaccinated pigs
1. What challenge dose of virulent PRRSV is
required to cause infection and consequences
of infection?
- viremia, fever, reduced ADWG
2. Is there an infectious dose where vaccination
prevents consequences of infection?

4. Study Design
 Randomized, blinded vaccination-challenge study
 Pigs used for the study were 3 wks of age and
PRRSV naïve; confirmed PCR negative for
PRRSV

5. Study Design
Group
No. Inglevac
PRRS® MLV
Vaccinated
Pigs
(2ml IM)
No. Non-
vaccinated
Challenge
Control
Pigs
PRRSV SDSU-
73
Challenge
Dosage
(Log10TCID50/
ml)
(2ml IN)
Study
Termination
Day 0 Day 0 Day 28 Day 70
1 10 10 4
2 10 10 3
3 10 10 2
4 10 10 1
5 10 - None

6. Study Design
Parameter Day
Viremia PCR (+/-) 0, 7,14, 21, 28, 31, 33, 35, 38,
42, and weekly thereafter until
day 70
Temperature
(Pyrexia defined as a
rectal temp > 40.0°C)
Day 27
Daily for 14 days until Day 42
ADWG 0, 28, 70

7. Study Design
 Statistics
- Results summarized via descriptive statistics by day,
challenge dose and group
- For number days pyrexic and ADWG post-challenge
- Linear regression model incorporating treatment &
challenge dose
- P-value < 0.05 was used to indicate statistical
significance

8. Results – Viremia following 4 log virus challenge
 Following challenge, all pigs in Ingelvac PRRS® MLV vaccinated
groups 1 & 2 (4 and 3 log challenge) became viremic by day 31
 Following day 42 (14 days post-challenge), viremia begins
decreasing in vaccinates until day 70
 From day 42 to day 70, vaccinated pigs in groups 1 & 2 demonstrate
less percent PCR positive pigs than non-vaccinated-challenged pigs
- Reduction in post-challenge viremia in vaccinated pigs
0%
20%
40%
60%
80%
100%
120%
28 31 33 35 38 42 49 56 63 70
%PCRPositive
Days
Ingelvac PRRS® MLV
Challenge Control (non-
vaccinated)
Ingelvac PRRS® MLV
(no challenge)
Figure 1: Percentage of viremic pigs per treatment group challenged with 4 logs

9. Results – Viremia following 2 log virus challenge
 At a challenge dose of 2 logs or less (groups 3 & 4)
- Vaccinated pigs demonstrate less percent PCR positive pigs than the non-
vaccinated challenge controls
- Pattern of viremia following challenge is similar to vaccinated non-challenged pigs
- Consequences of challenge in vaccinates similar to non-challenged pigs
 As challenge dose decreases, the percentage of viremic pigs in
vaccinated groups decreases
 At all challenge doses, the non-vaccinated and challenged pigs show
similar post-challenge viremia profile
0%
20%
40%
60%
80%
100%
120%
28 31 33 35 38 42 49 56 63 70
%PCRPositive
Days
Ingelvac PRRS® MLV
Challenge Control (non-
vaccinated)
Ingelvac PRRS® MLV
(no challenge)
Figure 2. Percentage of viremic pigs per treatment group challenged with 2 logs

10. Results – Pyrexia/Fever
 At each challenge dose Ingelvac PRRS® MLV vaccinates
- Had significant decrease in fever days compared to non-vaccinates
- Maintained lower average temperature compared to non-vaccinates
 At PRRSV challenge of 2 logs or less
- Post-challenge temperatures of Ingelvac PRRS ® MLV vaccinated pigs are
similar to temperatures of vaccinated non-challenged pigs
Mean Number Days Pyrexic Post-Challenge
Treatment Group
4 log
challenge
3 log
challenge
2 log
challenge
1 log
challenge
No-
challenge
Ingelvac PRRS® MLV 4.41 4.21 1.01 1.41 1.8
Challenge Control
(non-vaccinated)
11.2 8.8 10.0 6.0 -
1 Statistically significant difference (P<0.05) in number of days pyrexic between groups based on model prediction

11. Results – Pyrexia/Fever
39.2
39.4
39.6
39.8
40.0
40.2
40.4
40.6
40.8
27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42
Degrees(C°)
Days
Ingelvac PRRS®
MLV
Challenge Control
(non-vaccinated)
Ingelvac PRRS®
MLV (no challenge)
Figure 3. Average daily temperature per treatment group challenged with 4 logs of PRRSV

12. Results – Pyrexia/Fever
At PRRSV challenge of 2 logs or less
• Post-challenge temperatures of Ingelvac PRRS ® MLV vaccinated pigs are
similar to temperatures of vaccinated non-challenged pigs
• Consequences of challenge in vaccinates similar to non-challenged pigs
39.0
39.2
39.4
39.6
39.8
40.0
40.2
40.4
40.6
40.8
41.0
27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42
Degrees(C°)
Days
Ingelvac PRRS®
MLV
Challenge
Control (non-
vaccinated)
Ingelvac PRRS®
MLV (no
challenge)
Figure 4. Average daily temperature per treatment group challenged with 2 logs of PRRSV

13. Results – Pyrexia/Fever
• Significant decrease in days pyrexic - vaccinates compared to non-
vaccinates at each challenge dose
• Days pyrexic decreased as challenge dose decreased in both vaccinated
and non-vaccinated groups
Figure 5. Number of Days Pyrexic by Group and Challenge Dose

14. Results – Average Daily Weight Gain
 Ingelvac PRRS® MLV vaccinated groups had higher ADWG
compared to non-vaccinated challenge controls @ all challenge
doses
- Statistically significant (P<0.05) in the 3, 2, and 1 log challenge groups &
at P<0.07 in the 4 log challenge group
 Measurable and negative ADWG impact in non-vaccinated
challenged groups at all challenge doses
- No significant difference in ADWG across all challenge doses in non-
vaccinated groups
ADWG (lbs) Days 28-70
Treatment Group
4 log
challenge
3 log
challenge
2 log
challenge
1 log
challenge
No-challenge
Ingelvac PRRS®
MLV
1.41 1.291 1.701 1.641 1.67
Challenge Control
(non-vaccinated)
1.18 1.06 1.15 1.23 -
1 Statistically significant difference (P<0.05) in ADWG between Ingelvac PRRS®MLV and Challenge control
groups based on model prediction

15. Results – Average Daily Weight Gain
 ADWG of Ingelvac PRRS® MLV vaccinated groups
challenged w/ 2 logs of PRRSV or less was numerically
similar to the ADWG of vaccinated non-challenged group
- Limited post-challenge ADWG impact in vaccinated pigs
- Consequences of challenge in vaccinates similar to non-
challenged pigs
1 Statistically significant difference (P<0.05) in ADWG between Ingelvac PRRS® MLV and Challenge
control groups based on model prediction
ADWG (lbs) Days 28-70
Treatment Group
4 log
challenge
3 log
challenge
2 log
challenge
1 log
challenge
No-
challenge
Ingelvac PRRS® MLV 1.41 1.291 1.701 1.641 1.67
Challenge Control
(non-vaccinated)
1.18 1.06 1.15 1.23 -

16. Results – Average Daily Weight Gain
 Significant increase in
ADWG in vaccinates based
on challenge dose
- 0.085 increase in ADWG for
each one log decrease in
challenge dose
 Measurable and negative
ADWG impact in non-
vaccinated challenged
groups at all challenge
doses
- No significant difference in
ADWG across all challenge
doses in non-vaccinated groups
Figure 6. Average Daily Weight Gain - Days 28-70
by Group and Challenge Dose

17. Summary – Take Home Message
• Objective of study was to evaluate effect of PRRSV
challenge dose in vaccinated pigs
• In this heterologous PRRSV challenge study Ingelvac®
PRRS MLV vaccinated pigs demonstrated:
- Reduction in viremia compared to challenge controls at all challenge
doses
- Reduction in fever compared to challenge controls at all challenge
doses
- Increased ADWG compared to challenge controls at all challenge
doses
- Mitigation of the negative consequences of PRRSV infection
compared to non-vaccinated challenged pigs at all challenge doses

18. Summary – Take Home Message
 For all endpoints – there was little indication of a difference
between 0 (no challenge), 1 and 2 log challenge in
vaccinated pigs
- Indicating a challenge dose effect in vaccinated pigs
- At a challenge of 2 logs or less, the consequences of
challenge in vaccinated pigs were similar to non-
challenged pigs
 Conversely, in non-vaccinated pigs, the post-challenge
viremia and impact on ADWG were similar across all
challenge doses
- Indicating no challenge dose effect in non-vaccinated pigs
- Measureable & negative impact at all challenge doses in
non-vaccinated pigs

19. Summary – Take Home Message
 As in previous studies; this study is another example
demonstrating the ability of Ingelvac PRRS® MLV vaccine
to protect against a relevant PRRSV challenge and
mitigate the biologic consequences of infection
 Based on challenge dose, the consequences of
challenge in vaccinated pigs can be similar to non-
challenged pigs
 Relevance in the field
- Implementation of “system-based” and “area/region
based” control programs
- Limiting the consequences of infection