Patricia Domínguez

Phylogenetic networks to study the origin and evolution of porcine circovirus type 2 (PCV2) in Cuba.

Porcine circovirus type 2 (PCV2) is the essential etiological infectious agent of postweaning multisystemic wasting syndrome (PMWS), which is considered one of the most economically important swine diseases worldwide. In this study, a comparison between methodologies based on classical phylogenetic trees and networks to infer the origin of PCV2 in Cuba was performed. In addition, the mechanisms supporting the genetic variability of Cuban PCV2 populations were investigated. A retrospective study, using pig sera collected in Cuba from 1993 to 2004, to evaluate the presence of PCV2 genome and PCV2-specific antibodies was also conducted and revealed a lack of evidence of PCV2 infection in Cuban swine from years 1993 to 2004. A total of 24 complete Cuban PCV2 sequences collected between 2005 and 2009 from different regions of the country were analyzed. Three classical methods of phylogenetic analysis, namely Neighbour-Joining, Maximum Parsimony and Bayesian Inference, as well as haplotype network construction, were used. Whereas the classical phylogenetic trees suggested different origins for the Cuban PCV2 strains, the haplotype network revealed a direct connection between all the Cuban sequences in agreement with the obtained epidemiological and viral sequence data. Moreover, the importation of pigs carried out in 2005 from the Quebec-Ontario region, Canada, seems to be the most likely origin of PCV2 in Cuba. Likewise, the genetic variability of Cuban PCV2 sequences was supported by geographic segregation and positive selection pressure with estimated rates of nucleotide substitution on the order of 3.12×10(-3) and 6.57×10(-3) substitutions/site/year, which are closer to those reported for RNA viruses.

Early onset and long lasting protection in pigs provided by a classical swine fever E2-vaccine candidate produced in the milk of goats.

For vaccination against classical swine fever virus (CSFV), it is strongly desirable to induce a rapid and long lasting protection. At present, only live attenuated CSFV vaccines have shown early onset of protection, differing with the recombinant subunit-based vaccines reported so far. Recently, a new vaccine formulation based on E2 envelope viral glycoprotein produced in the milk of goats (E2his) has been shown to induce a highly protective response in pigs against CSFV infection. Pigs immunized with a single dose of this vaccine candidate, formulated as a water-in oil emulsion, elicited an effective response against CSF as early as 7 days post-vaccination. No severe CSF clinical signs were observed and no animals died although the challenge dose was 10(5)PDL(50) of a highly pathogenic CSFV strain. Noticeably, this response completely prevented CSFV infection in pigs when they were challenged under the same conditions 2 weeks after a single dose of the recombinant E2his vaccine formulation. A schedule consisting of a primary immunization with the same vaccine candidate, followed by a booster dose 2 weeks later induced a highly protective response against CSFV infection for as long as 9 months post-vaccination. These promising results demonstrate by far the feasibility of using the E2his-based vaccine in regional programs for preventing and controlling CSF.

First report of porcine circovirus type 2 infections in Cuba.

To obtain information about the porcine circovirus type 2 (PCV2) infection status of pigs in Cuba and the probable association of PCV2 with other porcine viruses, tissue samples collected from ill pigs were evaluated using polymerase chain reaction (PCR). The PCR analysis showed that 67.7% of the samples (23/34) from seven swine herds of six different geographic regions were detected to be positive for PCV2. Ten of the 23 PCV2 positive samples (43.5%) shown a concurrent infection with porcine parvovirus (PPV) and 17 of 23 PCV2 positive samples (73.9%) exhibited a concomitant infection with classical swine fever virus (CSFV). This study is the first report of PCV2 infecting pigs with different clinical conditions in Cuban swine herds and provides evidence of PCV2 co-infection with PPV and CSFV in the field.