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VACCINATION AGAINST A RECENTLY EMERGED VIRULENT PRRS VIRUS (RFLP 1-7-4)Jay G. Calvert PhD; Jose Angulo DVM; Gene Nemechek DVM; Marcia L. Keith BS; Lucas P Taylor MS; Douglas S. Pearce BS; Chadwick Brice BS; M. Corinne Lenz MS

North American PRRS SymposiumDecember 6, 2015

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Objective for Today:

• To share final results from a challenge study using Fostera® PRRS against a 2015 isolate of PRRS (RFLP 1-7-4) from a pig flow suffering from a severe clinical outbreak in North Carolina.

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Fostera® PRRS is a Modified-Live Vaccine Attenuated on Novel Engineered Cell Lines

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Background•Emerging viruses represent a common and recurrent threat. New strains differ in virulence, transmissibility, and persistence– “Atypical” PRRS (1996)– RFLP 1-8-4 (2002)– RFLP 1-18-2 (2008)– RFLP 1-26-2 (2009)– RFLP 1-7-4 (2014)

•A virulent new strain with an RFLP pattern of 1-7-4 appeared first in North Carolina in 2014 and subsequently in the upper Midwest.

•We conducted this study to gain a better understanding of the impact of PRRSV 1-7-4 in weaned pigs.– Expectations around immunized pigs under controlled conditions– Tools and interventions available to monitor, evaluate, and control

PRRS 1-7-4 in the field

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Relationship between Fostera® PRRS and Challenge Strain (RFLP 1-7-4)

ORF5 nucleotide sequence dendrogram of vaccine strains and representative field strains using the ClustalW algorithm (MegAlign and TreeView)

Recent virulent RFLP 1-7-4 isolates are equally distant from US vaccine strains and cluster with other Lineage 1 viruses

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Study Design & TimelineStudy Location: Midwest Veterinary Services Inc. in a BSL-2 facility.

Body Weight at arrival

Serum Sample collection & Vaccination (Day 0)

TX N Vaccination Challenge NecropsyNTX 6 NA NA Day 27

T01 20 Neg Control 1-7-4 Isolate (Day 28)

10 days post-challenge (Day 38)T02 20 Fostera® PRRS

Rectal temps, Clinical observations, weigh, serum sample(Day 27)

Clinical observations, Challenge(Day 28)

Rectal Temps, Serum sample(Days 31, 33, 35, 37)

Weigh, ADG, Necropsy, Lung lesion scores, lung samples(Day 38)

• Pigs were housed in separate rooms by treatment before challenge, then rehoused and comingled prior to challenge.

• All experiments involving animals were conducted in compliance with national legislation and subject to review by the local Institutional Animal Care and Use Committee (IACUC).

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Outcome Criteria

Primary variable– Percent lung lesions

Secondary variables– Clinical signs (incidence and duration)– Mortality– Level and duration of viremia (RT-qPCR)– Innate immune response (IFN-alpha)– Rectal temps– Average daily gain (ADG)

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Data Summary and Analysis

•The Zoetis-VMRD Biometrics group was responsible for data analysis through a centralized data management system (SAS/STAT version 9.3, SAS institute Cary NC)

•Only post-commingling data were analyzed using comparative statistics

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Lung Lesions

T01 (Control) T02 (Fostera® PRRS)0

5

10

15

20

25

30

35

40

45

30.4

11.9

Mea

n Pe

rcen

t Lun

g w

ith L

esio

ns

TX N Mean percent lung with lesions

Standard error

Lower 95% confidence

interval

Upper 95% confidence

interval

Range

T01 20 30.4 4.37 21.0 40.7 5.9-58.0

T02 20 11.9* 3.08 5.9 19.7 0.9-62.5

Back Transformed Least Squares Means Percent Lung with Lesions

*

*P = 0.0066

*Significant difference P≤ 0.05

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Incidence of Clinical SignsPercent of animals ever observed with an abnormal condition

T02T01T02T01T02T01T02T01

100%

80%

60%

40%

20%

0%

5%

60%

100%

60%

15%

30%

65%

30%

T02 (Fostera® PRRS)T01 (C

General Condition

CoughRespiratory Distress

Depression

Clinical Observation:

ontrol)

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Level of Viremia (RT-qPCR)

25 27 29 31 33 35 37 390.00E+00

5.00E+05

1.00E+06

1.50E+06

2.00E+06

2.50E+06

3.00E+06Vaccination reduces post-challenge viremia in serum

T01 viremiaT02 viremia

Study Day

PRR

SV R

NA

(cop

ies/

mL

seru

m)

*

*

P=0.0002

P<0.0001

*

P=0.0010

P=0.0317

*

Challenge

T01 (control)T02 (Fostera® PRRS)

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25 27 29 31 33 35 37 390

10

20

30

40

50

60

70

80

0.00E+00

5.00E+05

1.00E+06

1.50E+06

2.00E+06

2.50E+06

3.00E+06

Vaccination reduces post-challenge viremia and IFNα in serum

T01 IFN-alphaT02 IFN-alphaT01 viremiaT02 viremia

Study Day

IFN

α (p

g/m

L se

rum

)

PRR

SV R

NA

(cop

ies/

mL

seru

m)

*

† †

†

†Significant difference P< 0.05 for mean Serum IFNα titers.Challenge

Innate Immune Response (IFNα)Viremia and Interferon are Correlated

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Rectal TemperaturesMean Rectal Temperatures Post-Challenge

No significant differences were found when comparing post-challenge rectal temperatures across treatments.

27 28 29 30 31 32 33 34 35 36 37102.5

103

103.5

104

104.5

105

105.5

106

T01 (Control)

T02 (Fostera® PRRS)

Study Day

Deg

rees

Fah

renh

eit

Challenge

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T01 (Control) T02 (Fostera® PRRS)0.0000.1000.2000.3000.4000.5000.6000.7000.8000.900

0.240

0.830

AD

G (p

ound

s)Body weight & ADG post-challenge

  Day -5 Day 27 Day 37 ADG  D27 – D37

T01 (Control) 13.1 56.5 58.9 0.240T02 (Fostera® PRRS) 12.9 54.1 62.3 0.830*

*Significant difference P≤ 0.05*

*P=0.0001

Average Daily Gain (ADG) post-challenge

Mean body weight (pounds) before and after challenge and ADG post-challenge

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Summary of Results• Mean Percent Lung with Lesions: 30.4% (controls) vs 11.9%

(vaccinates) (P = 0.0066)

• Incidence of Clinical Signs: General condition 60% (controls) vs 30% (vaccinates); Depression 100% (controls) vs 65% (vaccinates); Respiratory distress 60% (controls) vs 30% (vaccinates)

• Mortality: No mortality was observed in either pre-challenge or post-challenge

• Viremia: At all post-challenge time points, serum from vaccinated pigs had significantly less virus RNA than serum from control pigs (P≤ 0.05)

• Rectal Temperatures: No significant differences between the treatment groups

• Growing performance: ADG post-challenge: 0.240 (controls) vs 0.830 (vaccinates) (P=0.0001)

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Conclusions•This study demonstrates a protective vaccine effect in animals vaccinated with Fostera® PRRS against respiratory disease caused by a virulent Lineage 1 (RFLP 1-7-4) PRRS virus

•Pigs vaccinated with Fostera® PRRS had 50% reduction in clinical signs (General Condition and Respiratory Disease) compared to non-vaccinated pigs

•Vaccination with Fostera® PRRS reduced levels of viremia which may, in turn, result in a decreased incidence of spread of infectious virus

•As a consequence of reduced viremia post-challenge, vaccination with Fostera® PRRS also reduced IFNα production post-challenge allowing animals to continue to grow in the face of a virulent 1-7-4 challenge

•Pigs vaccinated with Fostera® PRRS had significantly higher ADG during the post-challenge phase of the study

THANK YOU FOR YOUR ATTENTION

QUESTIONS?