Efficacy Studies against PCV-2 of a New Trivalent Vaccine including PCV-2a and PCV-2b Genotypes and Mycoplasma hyopneumoniae When Administered at 3 Weeks of Age.

This study aimed to evaluate the efficacy of a new trivalent vaccine containing inactivated Porcine Circovirus 1-2a and 1-2b chimeras and a Mycoplasma hyopneumoniae bacterin administered to pigs around 3 weeks of age. This trivalent vaccine has already been proved as efficacious in a split-dose regimen but has not been tested in a single-dose scenario. For this purpose, a total of four studies including two pre-clinical and two clinical studies were performed. Globally, a significant reduction in PCV-2 viraemia and faecal excretion was detected in vaccinated pigs compared to non-vaccinated animals, as well as lower histopathological lymphoid lesion plus PCV-2 immunohistochemistry scorings, and incidence of PCV-2-subclinical infection. Moreover, in field trial B, a significant increase in body weight and in average daily weight gain were detected in vaccinated animals compared to the non-vaccinated ones. Circulation of PCV-2b in field trial A and PCV-2a plus PCV-2d in field trial B was confirmed by virus sequencing. Hence, the efficacy of this new trivalent vaccine against a natural PCV-2a, PCV-2b or PCV-2d challenge was demonstrated in terms of reduction of histopathological lymphoid lesions and PCV-2 detection in tissues, serum and faeces, as well as improvement of production parameters.

Exploratory field study on the effects of porcine circovirus 2 (PCV-2) sow vaccination at different physiological stages mimicking blanket vaccination.

BACKGROUND: The objective of the present study was to explore the benefits of Porcine circovirus 2 (PCV-2) blanket vaccination in a sow herd on productive parameters, PCV-2 infection and immune status in sows and their progeny. For this purpose, 288 sows were distributed among four balanced experimental groups. One group remained as negative control group and the other three received 1 mL of PCV-2 Ingelvac Circoflex® intramuscularly at different productive cycle moments: before mating, mid gestation (42-49 days post-insemination) or late gestation (86-93 days post-insemination); phosphate buffered saline (PBS) was used as negative control item. Reproductive parameters from sows during gestation and body weight of their progeny from birth to weaning were recorded. Additionally, blood was collected from sows at each vaccination time and piglets at 3 weeks of age. Moreover, up to 4 placental umbilical cords (PUC) per sow were taken at peri-partum. Sera from sows and piglets were analysed for PCV-2 antibody detection using an enzyme-linked immunosorbent assay (ELISA). Sera from sows and PUC were tested to quantify viraemia using a real time quantitative polymerase chain reaction (qPCR) assay. RESULTS: Globally, results indicated that vaccinated sows showed heavier piglets at birth and at weaning, less cross-fostered piglets, lower viral load at farrowing as well as in PUC, and higher antibody levels at farrowing, compared to non-vaccinated ones. When all groups were compared among them, sows vaccinated at mid or late gestation had heavier piglets at birth than non-vaccinated sows, and lower proportion of PCV-2 positive PUC. Also, cross-fostering was less frequently practiced in sows vaccinated at pre-mating or mid gestation compared to non-vaccinated ones. CONCLUSIONS: In conclusion, the present study points out that PCV-2 sow vaccination at different time points of their physiological status (mimicking blanket vaccination) offers benefits at production and serological and virological levels.

Porcine circovirus 2 (PCV2) population study in experimentally infected pigs developing PCV2-systemic disease or a subclinical infection.

Porcine circovirus 2 (PCV2) is a single stranded DNA virus with one of the highest mutation rates among DNA viruses. This ability allows it to generate a cloud of mutants constantly providing new opportunities to adapt and evade the immune system. This pig pathogen is associated to many diseases, globally called porcine circovirus diseases (PCVD) and has been a threat to pig industry since its discovery in the early 90's. Although 11 ORFs have been predicted from its genome, only two main proteins have been deeply characterized, i.e. Rep and Cap. The structural Cap protein possesses the majority of the epitopic determinants of this non-enveloped virus. The evolution of PCV2 is affected by both natural and vaccine-induced immune responses, which enhances the genetic variability, especially in the most immunogenic Cap region. Intra-host variability has been also demonstrated in infected animals where long-lasting infections can take place. However, the association between this intra-host variability and pathogenesis has never been studied for this virus. Here, the within-host PCV2 variability was monitored over time by next generation sequencing during an experimental infection, demonstrating the presence of large heterogeneity. Remarkably, the level of quasispecies diversity, affecting particularly the Cap coding region, was statistically different depending on viremia levels and clinical signs detected after infection. Moreover, we proved the existence of hyper mutant subjects harboring a remarkably higher number of genetic variants. Altogether, these results suggest an interaction between genetic diversity, host immune system and disease severity.

Exploratory metagenomic analyses of periweaning failure-to-thrive syndrome-affected pigs.

Modern pig farming is characterised by the emergence of several syndromes whose aetiology is unclear or has a multifactorial origin, including periweaning failure-to-thrive syndrome (PFTS). In fact, its specific aetiology remains elusive, although several causes have been investigated over time. The present study aimed to investigate the potential role of viral agents in PFTS-affected and healthy animals by evaluating the virome composition of different organs using a metagenomic approach. This analysis allowed demonstrating a higher abundance of Porcine parvovirus 6 (PPV6) in healthy subjects while Ungulate bocaparvovirus 2 (BoPV2), Ungulate protoparvovirus 1 (PPV) and Porcine circovirus 3 (PCV-3) were increased in pigs with PFTS. No differential abundance of RNA viruses was found between PFTS-affected and control pigs. Remarkably, this is the first molecular characterisation of PPV6 and BoPV2 in Spain and one of the few all around the world, supporting their apparent widespread circulation. Interestingly, PCV-3 has been recently identified in several clinical-pathological conditions as well as in healthy pigs, while BoPV2 pathogenic potential is unknown. Although obtained results must be taken as preliminary, they open the door for further studies on the potential role of these viruses or their combination as predisposing factor/s for PFTS occurrence.

Porcine circovirus 2 (PCV-2) genetic variability under natural infection scenario reveals a complex network of viral quasispecies.

Porcine circovirus 2 (PCV-2) is a virus characterized by a high evolutionary rate, promoting the potential emergence of different genotypes and strains. Despite the likely relevance in the emergence of new PCV-2 variants, the subtle evolutionary patterns of PCV-2 at the individual-host level or over short transmission chains are still largely unknown. This study aimed to analyze the within-host genetic variability of PCV-2 subpopulations to unravel the forces driving PCV-2 evolution. A longitudinal weekly sampling was conducted on individual animals located in three farms after the first PCV-2 detection. The analysis of polymorphisms evaluated throughout the full PCV-2 genome demonstrated the presence of several single nucleotide polymorphisms (SNPs) especially in the genome region encoding for the capsid gene. The global haplotype reconstruction allowed inferring the virus transmission network over time, suggesting a relevant within-farm circulation. Evidences of co-infection and recombination involving multiple PCV-2 genotypes were found after mixing with pigs originating from other sources. The present study demonstrates the remarkable within-host genetic variability of PCV-2 quasispecies, suggesting the role of the natural selection induced by the host immune response in driving PCV-2 evolution. Moreover, the effect of pig management in multiple genotype coinfections occurrence and recombination likelihood was demonstrated.

Genetic variability of porcine circovirus 2 in vaccinating and non-vaccinating commercial farms.

Vaccines against porcine circovirus 2 (PCV2) are now widely used to control the diseases caused by the virus. Although the vaccines protect pigs against the disease, they do not lead to sterilizing immunity and therefore infections with PCV2 continue in farms. It is expected that, due to its high evolutionary rate, PCV2 can adapt quickly to environmental pressures such as vaccination. The goal of this study was to elucidate the molecular variation of PCV2 in relation to vaccination. PCV2 variability was investigated from samples of infected pigs from five farms where vaccination had never been applied and two farms where pigs had been vaccinated for at least 2 years. For the genetic analysis, full PCV2 genomes were amplified and subsequently pooled by vaccination status from serum of eight vaccinated, infected pigs and 16 non-vaccinated, infected pigs. Variability of viral populations was quantified using next-generation sequencing and subsequent bioinformatics analysis. The number of segregating sites was similar in the non-vaccinated (n=109) and vaccinated pools (n=96), but the distribution of these sites in the genome differed. Most notably, in the capsid gene, the number of segregating sites was observed only in the non-vaccinated population. Based on the structural analysis, it is expected that some low-frequency amino acids result in biologically low-fit viruses. On the contrary, D294 in replicase represents a novel amino acid which was dominant and unique in the vaccinated pool. This work showed that variable PCV2 populations were circulating in commercial farms, and that this variability was different in samples obtained from vaccinating and non-vaccinating farms.

Effect of sow and piglet porcine circovirus type 2 (PCV2) vaccination on piglet mortality, viraemia, antibody titre and production parameters.

The present study describes the effects of sow and/or piglet porcine circovirus type 2 (PCV2) vaccination on viraemia, antibody response and production parameters (average daily weight gain [ADWG] and mortality) of piglets from a PCV2 subclinically infected farm. Four hundred seventy-six piglets born from vaccinated (V) or non-vaccinated (NV) sows were further subdivided in a total of four groups: NV sows-NV pigs (NV-NV, n=134), NV sows-V pigs (NV-V, n=135);V sows-NV pigs (V-NV, n=104) and V sows-V pigs (V-V, n=103). A single vaccination of sows before mating was able to confer significantly higher antibody titres to their piglets at 4 weeks of age and a different PCV2 dynamics infection compared to piglets coming from NV sows. Piglet vaccination (independently of sow treatment) caused an earlier seroconversion and lower percentages of PCV2 infected pigs compared to the NV ones throughout their life. The double PCV2 vaccination strategy was able to reduce PCV2 infection but apparently caused some interference in piglet humoral response development. PCV2 vaccination was able to overcome this interference since the ADWG was improved in both groups of vaccinated piglets, independently of the sow treatment, being the highest ones obtained in the double vaccination group.

How cellulose-based leaf toughness and lamina density contribute to long leaf lifespans of shade-tolerant species.

Cell wall fibre and lamina density may interactively affect leaf toughness and leaf lifespan. Here, we tested this with seedlings of 24 neotropical tree species differing in shade tolerance and leaf lifespan under standardized field conditions (140-867 d in gaps; longer in shade). We quantified toughness with a cutting test, explicitly seeking a mechanistic linkage to fibre. Lamina density, but not fracture toughness, exhibited a plastic response to gaps vs shade, while neither trait was affected by leaf age. Toughness corrected for lamina density, a recently recognized indicator of material strength per unit mass, was linearly correlated with cellulose content per unit dry mass. Leaf lifespan was positively correlated with cellulose and toughness in shade-tolerant species but only weakly in gap-dependent species. Leaf lifespan was uncorrelated with lamina thickness, phenolics and tannin concentrations. In path analysis including all species, leaf lifespan was directly enhanced by density and toughness, and indirectly by cellulose via its effect on toughness. Different suites of leaf traits were correlated with early seedling survival in gaps vs shade. In conclusion, cellulose and lamina density jointly enhance leaf fracture toughness, and these carbon-based physical traits, rather than phenolic-based defence, explain species differences in herbivory, leaf lifespan and shade survival.