Identification and characterization of microRNAs in porcine circovirus type 2 and African swine fever virus infections in vivo

On Friday 30th of   September, at 11:00 am, the doctoral thesis dissertation of Fernando Núñez will be held at the Hall of the Faculty of Veterinary Medicine at the UAB. The thesis is entitled: Identification and characterization of microRNAs in porcine circovirus type 2 and African swine fever virus infections in vivo. The thesis was conducted at IRTA-CReSA facilities, under the direction of Dr. Jose Ignacio Núñez.

MicroRNAs (miRNAs) are small, non- coding RNA molecules with post- transcriptional regulatory functions that inhibit protein sinthesys. Trheir imprtance has increased in the last few years due to their huge importance in a great number of biological processes. The study of miRNA mediated viral- host interactions has emerged the last decade as they have increased their  importance in the antiviral defense.

miRNA sequence (red line) in its origin

Four different studies were carried out in order to analyze the expression of porcine microRNAs (miRNAs) and viral miRNAs in two separate in vivo infections with porcine circovirus type 2 (PCV2) and African swine fever virus (ASFV). PCV2 is the essential etiological infectious agent of PCV2-systemic disease and it has been associated with other swine diseases, all of them collectively known as porcine circovirus diseases. African swine fever is a re-expanding devastating viral disease, a highly lethal hemorrhagic disease that is currently threatening the pig industry worldwide. miRNAs are a new class of small non-coding RNAs that regulate gene
expression post-transcriptionally.  


The objective of the first study was to identify the miRNA expression pattern in PCV2 subclinically infected and non-infected pigs. For this purpose an experimental PCV2 infection was carried out and small-RNA libraries were constructed. High throughput sequencing determined differences in miRNA expression due to the disease. These miRNAs also were involved in immunological and PCV2 disease- related pathways.

The objective of the second study was to explore if PCV2 can encode viral miRNAs. Viral miRNAs have been recently described and their number has increased in the past few years. From the constructed small RNA libraries, deep sequencing data revealed that PCV2 does not express miRNAs in an in vivo subclinical infection.

In the third study it was analyzed porcine miRNAs differentially expressed in pigs experimentally infected with a virulent strain at different times and animals infected with virulent strain and animals with its derived attenuated strain at same time. Differences in porcine miRNA expression between these viruses and conditions were analyzed. These miRNAs were found associated with cellular genes involved in pathways related to the immune response and virus-host interaction as well as with viral genes.

Global miRNAs network interaction between miRNAs , cellular and viral target genes and biological pathways in which miRNAs are involved in ASFV infection.

In the fourth study, it was explored if ASFV can encode viral miRNAs. For this end, both previous strains E75 and E75CV1 were used in addition to samples from pigs infected with the attenuated strain and necropsied at 31 dpi and animals infected with the attenuated strain, re- inoculated at 31 dpi with virulent strain Ba71 and necropsied at 38 dpi. The deep sequencing from the small RNA libraries indicated that ASFV does not encode viral miRNAs in any of these conditions.

The study of the miRNAs expression will contribute to a better understanding of PCV2 and ASFV pathogenesis, essential in the development of any strategy in order to control the diseases.

Ths studies included in this thesis have been published in the following scientific papers:

PhD studies developed by Fernando Núñez Hernández were supported by the “Formació i contractació de personal investigador novell” fellowship provided by the “Agència de Gestió d'Ajuts Universitaris i de Recerca” from Generalitat de Catalunya.

This work was supported by the project AGL2010-22358-C02 from Spanish Minister of Economy and Competitiveness.

To contact with this thesis director:

Dr. Jose Ignacio Núñez Garrote
Phone: +34 93 467 40 40
Campus UAB, Edifici CReSA s/n,  08193  Bellaterra (Cerdanyola del Vallès) Spain

About IRTA:

IRTA is a research institute devoted to R+D+I in a variety of agri-food areas, such as vegetal production, animal production, food industries, environment and global change, and agri-food economy. The transfer of scientific advances contribute to the modernization, competitiveness and sustainable development of agriculture, food and aquaculture sectors, the supply of healthy and quality foods for consumers and, consequently, improving the welfare of the population. IRTA is assigned to the Departament d’Agricultura, Ramaderia, Pesca i Alimentació (DARP, Department of Agriculture) of the Generalitat de Catalunya (Government of Catalonia).

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