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Protective Efficacy in Sheep of Adenovirus-Vectored Vaccines against Bluetongue Virus Is Associated with Specific T Cell Responses.

Martín V, Pascual E, Avia M, Peña L, Valcárcel F, Sevilla N - PLoS ONE (2015)

Bottom Line: Sheep vaccinated with Ad5-BTV-VP2 and Ad5-BTV-VP7 or only with Ad5-BTV-VP7 and challenged with BTV showed mild disease symptoms and reduced viremia.This partial protection was achieved in the absence of neutralizing antibodies but strong BTV-specific CD8+ T cell responses in those sheep vaccinated with Ad5-BTV-VP7.These data indicate that rAd5 is a suitable vaccine vector to induce T cell immunity during BTV vaccination and provide new data regarding the relevance of T cell responses in protection during BTV infection.

View Article: PubMed Central - PubMed

Affiliation: Centro de Investigación en Sanidad Animal (CISA-INIA), Instituto Nacional de Investigación Agraria y Alimentaria, Valdeolmos, Madrid, Spain.

ABSTRACT
Bluetongue virus (BTV) is an economically important Orbivirus of the Reoviridae family that causes a hemorrhagic disease in ruminants. Its control has been achieved by inactivated-vaccines that have proven to protect against homologous BTV challenge although unable to induce long-term immunity. Therefore, a more efficient control strategy needs to be developed. Recombinant adenovirus vectors are lead vaccine candidates for protection of several diseases, mainly because of their potency to induce potent T cell immunity. Here we report the induction of humoral and T-cell mediated responses able to protect animals against BTV challenge by recombinant replication-defective human adenovirus serotype 5 (Ad5) expressing either VP7, VP2 or NS3 BTV proteins. First we used the IFNAR(-/-) mouse model system to establish a proof of principle, and afterwards we assayed the protective efficacy in sheep, the natural host of BTV. Mice were completely protected against BTV challenge, developing humoral and BTV-specific CD8+- and CD4+-T cell responses by vaccination with the different rAd5. Sheep vaccinated with Ad5-BTV-VP2 and Ad5-BTV-VP7 or only with Ad5-BTV-VP7 and challenged with BTV showed mild disease symptoms and reduced viremia. This partial protection was achieved in the absence of neutralizing antibodies but strong BTV-specific CD8+ T cell responses in those sheep vaccinated with Ad5-BTV-VP7. These data indicate that rAd5 is a suitable vaccine vector to induce T cell immunity during BTV vaccination and provide new data regarding the relevance of T cell responses in protection during BTV infection.

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Histopathological lesions and viral load in vaccinated sheep.(A) Histopathological lesions in lungs sections stained with haematoxylin and eosin. Tissues were harvested at day 9 post-challenge with BTV-8. One representative animal is shown for each group. In control groups (PBS and Ad5-DsRed), pulmonary oedema with expansion of the interlobular septae and accumulation of protein rich fluid in airspaces was found. Magnification 100x. (B) Blood was collected from control (PBS and Ad5-DsRed) and vaccinated (Ad5-BTV-VP7 and Ad5-BTV-VP7 + Ad5-BTV-VP2) sheep at indicated times post-challenge with BTV-8. Total RNA was extracted from whole blood samples and RT-qPCR was performed as indicated in Material and Methods. Results are expressed as Ct. The cut off is indicated with a dotted line (Ct = 38 according to [39]).
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pone.0143273.g005: Histopathological lesions and viral load in vaccinated sheep.(A) Histopathological lesions in lungs sections stained with haematoxylin and eosin. Tissues were harvested at day 9 post-challenge with BTV-8. One representative animal is shown for each group. In control groups (PBS and Ad5-DsRed), pulmonary oedema with expansion of the interlobular septae and accumulation of protein rich fluid in airspaces was found. Magnification 100x. (B) Blood was collected from control (PBS and Ad5-DsRed) and vaccinated (Ad5-BTV-VP7 and Ad5-BTV-VP7 + Ad5-BTV-VP2) sheep at indicated times post-challenge with BTV-8. Total RNA was extracted from whole blood samples and RT-qPCR was performed as indicated in Material and Methods. Results are expressed as Ct. The cut off is indicated with a dotted line (Ct = 38 according to [39]).

Mentions: To determine the level of protection, viremia was evaluated in all animals by RT-qPCR. All sheep developed viremia, but in the vaccinated animals (group # 1 and # 2) the onset of viremia was delayed, lasted for a shorter time (cleared by D9pc or D14pc), and the Ct value was higher than in the control groups at the peak of viral replication (Ct values from 25 in control groups to 29.3 in vaccinated animals at D7pc) (Fig 5B). In general, viral loads remain significantly lower (Ad5-BTV-VP7 + Ad5-BTV-VP2 vaccinated sheep p value < 0.0397 and Ad5-BTV-VP7 vaccinated sheep p value < 0.0004, Mann-Whitney U test) than those obtained in control animals. Taken all the data together, vaccination with Ad5-BTV-VP7 and Ad5-BTV-VP2 protected sheep of BTV-challenge although this vaccination did not induce sterile protection.


Protective Efficacy in Sheep of Adenovirus-Vectored Vaccines against Bluetongue Virus Is Associated with Specific T Cell Responses.

Martín V, Pascual E, Avia M, Peña L, Valcárcel F, Sevilla N - PLoS ONE (2015)

Histopathological lesions and viral load in vaccinated sheep.(A) Histopathological lesions in lungs sections stained with haematoxylin and eosin. Tissues were harvested at day 9 post-challenge with BTV-8. One representative animal is shown for each group. In control groups (PBS and Ad5-DsRed), pulmonary oedema with expansion of the interlobular septae and accumulation of protein rich fluid in airspaces was found. Magnification 100x. (B) Blood was collected from control (PBS and Ad5-DsRed) and vaccinated (Ad5-BTV-VP7 and Ad5-BTV-VP7 + Ad5-BTV-VP2) sheep at indicated times post-challenge with BTV-8. Total RNA was extracted from whole blood samples and RT-qPCR was performed as indicated in Material and Methods. Results are expressed as Ct. The cut off is indicated with a dotted line (Ct = 38 according to [39]).
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4664254&req=5

pone.0143273.g005: Histopathological lesions and viral load in vaccinated sheep.(A) Histopathological lesions in lungs sections stained with haematoxylin and eosin. Tissues were harvested at day 9 post-challenge with BTV-8. One representative animal is shown for each group. In control groups (PBS and Ad5-DsRed), pulmonary oedema with expansion of the interlobular septae and accumulation of protein rich fluid in airspaces was found. Magnification 100x. (B) Blood was collected from control (PBS and Ad5-DsRed) and vaccinated (Ad5-BTV-VP7 and Ad5-BTV-VP7 + Ad5-BTV-VP2) sheep at indicated times post-challenge with BTV-8. Total RNA was extracted from whole blood samples and RT-qPCR was performed as indicated in Material and Methods. Results are expressed as Ct. The cut off is indicated with a dotted line (Ct = 38 according to [39]).
Mentions: To determine the level of protection, viremia was evaluated in all animals by RT-qPCR. All sheep developed viremia, but in the vaccinated animals (group # 1 and # 2) the onset of viremia was delayed, lasted for a shorter time (cleared by D9pc or D14pc), and the Ct value was higher than in the control groups at the peak of viral replication (Ct values from 25 in control groups to 29.3 in vaccinated animals at D7pc) (Fig 5B). In general, viral loads remain significantly lower (Ad5-BTV-VP7 + Ad5-BTV-VP2 vaccinated sheep p value < 0.0397 and Ad5-BTV-VP7 vaccinated sheep p value < 0.0004, Mann-Whitney U test) than those obtained in control animals. Taken all the data together, vaccination with Ad5-BTV-VP7 and Ad5-BTV-VP2 protected sheep of BTV-challenge although this vaccination did not induce sterile protection.

Bottom Line: Sheep vaccinated with Ad5-BTV-VP2 and Ad5-BTV-VP7 or only with Ad5-BTV-VP7 and challenged with BTV showed mild disease symptoms and reduced viremia.This partial protection was achieved in the absence of neutralizing antibodies but strong BTV-specific CD8+ T cell responses in those sheep vaccinated with Ad5-BTV-VP7.These data indicate that rAd5 is a suitable vaccine vector to induce T cell immunity during BTV vaccination and provide new data regarding the relevance of T cell responses in protection during BTV infection.

View Article: PubMed Central - PubMed

Affiliation: Centro de Investigación en Sanidad Animal (CISA-INIA), Instituto Nacional de Investigación Agraria y Alimentaria, Valdeolmos, Madrid, Spain.

ABSTRACT
Bluetongue virus (BTV) is an economically important Orbivirus of the Reoviridae family that causes a hemorrhagic disease in ruminants. Its control has been achieved by inactivated-vaccines that have proven to protect against homologous BTV challenge although unable to induce long-term immunity. Therefore, a more efficient control strategy needs to be developed. Recombinant adenovirus vectors are lead vaccine candidates for protection of several diseases, mainly because of their potency to induce potent T cell immunity. Here we report the induction of humoral and T-cell mediated responses able to protect animals against BTV challenge by recombinant replication-defective human adenovirus serotype 5 (Ad5) expressing either VP7, VP2 or NS3 BTV proteins. First we used the IFNAR(-/-) mouse model system to establish a proof of principle, and afterwards we assayed the protective efficacy in sheep, the natural host of BTV. Mice were completely protected against BTV challenge, developing humoral and BTV-specific CD8+- and CD4+-T cell responses by vaccination with the different rAd5. Sheep vaccinated with Ad5-BTV-VP2 and Ad5-BTV-VP7 or only with Ad5-BTV-VP7 and challenged with BTV showed mild disease symptoms and reduced viremia. This partial protection was achieved in the absence of neutralizing antibodies but strong BTV-specific CD8+ T cell responses in those sheep vaccinated with Ad5-BTV-VP7. These data indicate that rAd5 is a suitable vaccine vector to induce T cell immunity during BTV vaccination and provide new data regarding the relevance of T cell responses in protection during BTV infection.

Show MeSH
Related in: MedlinePlus