Evolutionary-Related High- and Low-Virulent Classical Swine Fever Virus Isolates Reveal Viral Determinants of Virulence

Classical swine fever (CSF) has been eradicated from Western and Central Europe but remains endemic in parts of Central and South America, Asia, and the Caribbean. CSF virus (CSFV) has been endemic in Cuba since 1993, most likely following an escape of the highly virulent Margarita/1958 strain. In recent years, chronic and persistent infections with low-virulent CSFV have been observed. Amino acid substitutions located in immunodominant epitopes of the envelope glycoprotein E2 of the attenuated isolates were attributed to positive selection due to suboptimal vaccination and control. To obtain a complete picture of the mutations involved in attenuation, we applied forward and reverse genetics using the evolutionary-related low-virulent CSFV/Pinar del Rio (CSF1058)/2010 (PdR) and highly virulent Margarita/1958 isolates. Sequence comparison of the two viruses recovered from experimental infections in pigs revealed 40 amino acid differences. Interestingly, the amino acid substitutions clustered in E2 and the NS5A and NS5B proteins. A long poly-uridine sequence was identified previously in the 3' untranslated region (UTR) of PdR. We constructed functional cDNA clones of the PdR and Margarita strains and generated eight recombinant viruses by introducing single or multiple gene fragments from Margarita into the PdR backbone. All chimeric viruses had comparable replication characteristics in porcine monocyte-derived macrophages. Recombinant PdR viruses carrying either E2 or NS5A/NS5B of Margarita, with 36 or 5 uridines in the 3'UTR, remained low virulent in 3-month-old pigs. The combination of these elements recovered the high-virulent Margarita phenotype. These results show that CSFV evolution towards attenuated variants in the field involved mutations in both structural and non-structural proteins and the UTRs, which act synergistically to determine virulence.

Positive selection pressure on E2 protein of classical swine fever virus drives variations in virulence, pathogenesis and antigenicity: Implication for epidemiological surveillance in endemic areas

Classical swine fever (CSF), caused by CSF virus (CSFV), is considered one of the most important infectious diseases with devasting consequences for the pig industry. Recent reports describe the emergence of new CSFV strains resulting from the action of positive selection pressure, due mainly to the bottleneck effect generated by ineffective vaccination. Even though a decrease in the genetic diversity of the positively selected CSFV strains has been observed by several research groups, there is little information about the effect of this selective force on the virulence degree, antigenicity and pathogenicity of this type of strains. Hence, the aim of the current study was to determine the effect of the positive selection pressure on these three parameters of CSFV strains, emerged as result of the bottleneck effects induced by improper vaccination in a CSF-endemic area. Moreover, the effect of the positively selected strains on the epidemiological surveillance system was assessed. By the combination of in vitro, in vivo and immunoinformatic approaches, we revealed that the action of the positive selection pressure induces a decrease in virulence and alteration in pathogenicity and antigenicity. However, we also noted that the evolutionary process of CSFV, especially in segregated microenvironments, could contribute to the gain-fitness event, restoring the highly virulent pattern of the circulating strains. Besides, we denoted that the presence of low virulent strains selected by bottleneck effect after inefficient vaccination can lead to a relevant challenge for the epidemiological surveillance of CSF, contributing to under-reports of the disease, favouring the perpetuation of the virus in the field. In this study, B-cell and CTL epitopes on the E2 3D-structure model were also identified. Thus, the current study provides novel and significant insights into variation in virulence, pathogenesis and antigenicity experienced by CSFV strains after the positive selection pressure effect.

Measurement Invariance of the Brief Multidimensional Student’s Life Satisfaction Scale Among Adolescents and Emerging Adults Across 23 Cultural Contexts

There is hardly any cross-cultural research on the measurement invariance of the Brief Multidimensional Students’ Life Satisfaction Scales (BMSLSS). The current article evaluates the measurement invariance of the BMSLSS across cultural contexts. This cross-sectional study sampled 7,739 adolescents and emerging adults in 23 countries. A multi-group confirmatory factor analysis showed a good fit of configural and partial measurement weights invariance models, indicating similar patterns and strengths in factor loading for both adolescents and emerging adults across various countries. We found insufficient evidence for scalar invariance in both the adolescents’ and the emerging adults’ samples. A multi-level confirmatory factor analysis indicated configural invariance of the structure at country and individual level. Internal consistency, evaluated by alpha and omega coefficients per country, yielded acceptable results. The translated BMSLSS across different cultural contexts presents good psychometric characteristics similar to what has been reported in the original scale, though scalar invariance remains problematic. Our results indicate that the BMSLSS forms a brief measure of life satisfaction, which has accrued substantial evidence of construct validity, thus suitable for use in cross-cultural surveys with adolescents and emerging adults, although evaluation of degree of invariance must be carried out to ensure its suitability for mean comparisons.

Childhood sexual abuse and attachment insecurities as predictors of women's own and perceived-partner extradyadic involvement

We examined the association between self-reported childhood sexual abuse and a woman's own and perceived-partner extradyadic involvement (EDI). The association was examined both directly and as potentially mediated by attachment-related anxiety and avoidance in a sample of 807 French Canadian women. In line with our hypotheses, we found that a personal history of CSA is associated with a woman's own and perceived-partner EDI and with the woman's levels of attachment anxiety and avoidance. The association between CSA and own EDI was partially mediated by attachment-related avoidance. The results suggest that a sense of betrayal stemming from CSA predisposes a woman to avoidance, which in turn predisposes her to EDI. The association between CSA and perceived-partner EDI was partially mediated by both attachment anxiety and avoidance. These results suggest that victims of CSA become suspicious of others' relational behavior and intentions, which contribute to attachment-related anxiety and avoidance and both own and perceived-partner EDI.

Origin and evolution of viruses causing classical swine fever in Cuba

We have analyzed the origin and evolution of viruses from the classical swine fever (CSF) epidemic that affects Cuba since 2001 by nucleotide sequencing of regions within the E2 glycoprotein and the NS5B (polymerase) genes. The sequence of 190 nucleotides from E2 gene was determined for 10 CSF viruses isolated at different locations of the island, and used for phylogenetic analyses, including sequences from viruses of the 1993--1997 epizootic, previously determined, as well as those from representatives of the different CSFV genotypes. The phylogenetic tree obtained indicates that viruses circulating at present belong to the subgroup 1.2 and are closely related to those isolated during the 1993--1997 epizootic, including the strain Margarita used for vaccine potency tests in Cuba. However, the pattern of evolution revealed by these analyses was different than that observed previously, in which western isolates were almost identical to Margarita strain, while eastern isolates showed a higher level of genetic diversification. In this case, all the viruses analyzed grouped in an independent, define cluster that is closely related, albeit distinguishable, from that of Margarita-related viruses that previously circulated in the western part of Cuba. In addition, the 2001--2003 viruses showed a branched pattern with a level of sequence diversification similar to that observed in the eastern 1993--1997 viruses. Interestingly, a significant fraction (about 54%) of the mutations found in the E2 sequence led to amino acid replacements. This high rate of non-synonymous mutations was not found in the previous Cuban epizootic and has not been reported for other CSF outbreaks. In spite of these amino acid replacements, no antigenic changes were observed in the reactivity of different isolates with CSFV-specific MAbs and polyclonal sera. The phylogenetic tree derived from 409 nucleotides of NS5B gene of seven isolates and Margarita strain, was consistent with that obtained from E2 sequences. In this region, encoding a non-structural protein, a low level of fixation of non-synonymous mutations was observed. The results obtained suggests that epidemiological factors affecting CSFV spread during the current epizootic in Cuba can favour the fixation of non-synonymous mutation in the E2 gene, which could be associated with a lower severity in the clinical signs developed by most of the affected animals.

No association between secretor status of ABO blood group antigens and juvenile periodontitis

The aim of this study was to determine the association between secretor status of ABO blood group antigens and localized juvenile periodontitis (LJP). Forty-three patients with LJP (mean age 20.8 years) diagnosed according to Baer's criteria were selected. Thirty two periodontally healthy normal subjects (mean age 24.7 years) were use as control. Samples of blood and saliva were collected from patients and from control subjects. ABO blood group was determined by agglutination of erythrocytes with appropriate antisera. Determination of soluble ABO antigens in saliva was made by the haemagglutination inhibition assay. Subjects with O blood group were most frequent in both groups. The distribution of blood groups, and secretor and non-secretor status of ABO group antigens in LJP patients and control subjects was not significant. The results provide support for the hypothesis that there is no association between non-secretor status and LJP.

An RT-PCR assay for the specific detection of classical swine fever virus in clinical samples

A simple reverse transcriptase-polymerase chain reaction (RT-PCR) assay has been developed for the specific amplification of DNA after reverse transcription of RNA from the classical swine fever virus (CSFV). A pair of oligonucleotides was selected from an area of high homology in the genome of CSFV strains, but which differed from the corresponding sequences in the genome of bovine viral diarrhea virus (BVDV) strains. Using these primers (CSFV1-CSFV2), a CSFV specific DNA band of 174 bp was amplified from the CSFV RNA extracted from four reference strains and 14 field isolates, as well as from 25 organ extracts and eight buffy coats and serum samples of experimentally infected animals. No amplification was observed with the RNA from four BVDV reference and vaccine strains and seven field isolates. This RT-PCR assay made it possible, in a one-step reaction, to detect CSFV rapidly, sensitively and specifically in cell culture supernatants and in clinical specimens.

[Effect of a sodium fluoride solution at different temperatures on the solubility of deciduous dental enamel]

An in vitro study about the influence of temperature on the solubility of deciduous powdered enamel protected by sodium fluoride (0.05%) was made to observe the variation of the weight loss when the tissue was exposed to 0.5 N lactate buffer at pH 4.5. The protective capacity of fluoride to decrease the acid solubility in temporary tooth enamel presumably can be attribute to increase the temperature measured by scale centrigrade.