Dr. Reid Philips - Comparative Efficacy Evaluation of Two Modified-Live PRRS Vaccines

Evaluation of PRRSV challenge dose in vaccinated pigs

AASV Annual MeetingTechnical Partners Session

February 28th, 2016

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

Primary Objective: Question?

· In vaccinated pigs1. 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?

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

Study Design

Group

No. InglevacPRRS® MLVVaccinated

Pigs(2ml IM)

No. Non-vaccinatedChallenge

ControlPigs

PRRSV SDSU-73

ChallengeDosage

(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

Study Design

Parameter DayViremia 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 27Daily for 14 days until Day 42

ADWG 0, 28, 70

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

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

28 31 33 35 38 42 49 56 63 700%

20%40%60%80%

100%120%

Ingelvac PRRS® MLV

Challenge Control (non-vaccinated)

Ingelvac PRRS® MLV (no challenge)

Days

% P

CR

Pos

itive

Figure 1: Percentage of viremic pigs per treatment group challenged with 4 logs

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

28 31 33 35 38 42 49 56 63 700%

20%40%60%80%

100%120%

Ingelvac PRRS® MLV


Ingelvac PRRS® MLV (no challenge)

Days

% P

CR

Pos

itive

Figure 2. Percentage of viremic pigs per treatment group challenged with 2 logs

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

Results – Pyrexia/Fever

27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 4239.2

39.4

39.6

39.8

40.0

40.2

40.4

40.6

40.8

Ingelvac PRRS® MLV


Ingelvac PRRS® MLV (no chal-lenge)

Days

Deg

rees

(C°)

Figure 3. Average daily temperature per treatment group challenged with 4 logs of PRRSV


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

27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 4239.039.239.439.639.840.040.240.440.640.841.0

Ingelvac PRRS® MLVChallenge Con-trol (non-vac-cinated)Ingelvac PRRS® MLV (no chal-lenge)

Days

Deg

rees

(C°)

Figure 4. Average daily temperature per treatment group challenged with 2 logs of PRRSV


• 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

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


3 log challenge

2 log challenge

1 log challenge No-challenge



1 Statistically significant difference (P<0.05) in ADWG between Ingelvac PRRS®MLV and Challenge control groups based on model prediction

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


3 log challenge

2 log challenge

1 log challenge

No-challenge



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

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


· 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


· 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

Dr. Reid Philips - Comparative Efficacy Evaluation of Two Modified-Live PRRS Vaccines

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Transcript of Dr. Reid Philips - Comparative Efficacy Evaluation of Two Modified-Live PRRS Vaccines