The majority of proteins in cow’s milk are caseins, which occur in four groups (α-s1, α-s2, β, and k) encoded by different genes (CSN1S1, CSN1S2, CSN2, and CSN3, respectively). In this study, we focused on the β-casein allele variants A1 and A2 due to their influence on milk’s technological characteristics and human health. Digestion of the β-casein variant A1 leads to the formation of β-casomorphin 7 (BCM-7), a bioactive peptide that has been suggested to be a possible cause of various human diseases and associated with low milk digestibility. The potential negative role of the β-casein variant A1 in human health has stimulated the planning of cattle breeding programs based on genetic selection to increase the frequency of the A2 variant, which is associated with increased milk digestibility. The aim of this work was to evaluate the frequencies of the different β-casein variants in Italian Holstein Friesian dairy cows from cattle farms located in central Italy to select a population of A2 homozygous animals. β-casein genotypes were identified by evaluating the presence of single nucleotide polymorphisms (SNPs) of the CSN2 gene using PCR and sequencing analysis. The frequency of the desirable β-casein variant A2 in the studied bovine population was 0.61. The frequency of the undesirable A1 variant in the studied bovine population was 0.30. The frequency of the A2 allele was higher than expected for the breed; therefore, genetic selection for the A2 variant in these animals could be achieved in a fairly short time using A2 homozygous bulls.
Maedi-visna virus (MVV) and caprine arthritis encephalitis virus (CAEV), referred to as small ruminant lentiviruses (SRLVs), belong to the genus Lentivirus of the Retroviridae family. SRLVs infect both sheep and goats, causing significant economic losses and animal welfare damage. Recent findings suggest an association between serological status and allelic variants of different genes such as TMEM154, TLR9, MYD88 and CCR5. The aim of this work was to investigate the role of specific polymorphisms of these genes in SRLVs infection in some sheep flocks in Italy. In addition to those already known, novel variants in the TMEM154 (P7H, I74V, I105V) gene were detected in this study. The risk of infection was determined finding an association between the serological status and polymorphisms P7H, E35K, N70I, I74V, I105V of TMEM154, R447Q, A462S and G520R in TLR9 gene, H176H* and K190K* in MYD88 genes, while no statistical association was observed for the 4-bp deletion of the CCR5 gene. Since no vaccines or treatments have been developed, a genetically based approach could be an innovative strategy to prevent and to control SRLVs infection. Our findings are an important starting point in order to define the genetic resistance profile towards SRLVs infection.
Small ruminant lentiviruses (SRLVs) represent a very heterogeneous group of ss-RNA viruses that infect sheep and goats worldwide. They cause important, deleterious effects on animal production and limit the animal trade. SRLVs show a high genetic variability due to high mutation rate and frequent recombination events. Indeed, five genotypes (A-E) and several subtypes have been detected. The aim of this work was to genetically characterize SRLVs circulating in central Italy. On this basis, a phylogenetic study on the gag-pol genetic region of 133 sheep, collected from 19 naturally infected flocks, was conducted. In addition, to evaluate the frequency of mutation and the selective pressure on this region, a WebLogo 3 analysis was performed, and the dN/dS ratio was computed. The results showed that 26 samples out of 133 were clustered in genotype A and 106 samples belonged to genotype B, as follows: A9 (n = 8), A11 (n = 10), A24 (n = 7), B1 (n = 2), B2 (n = 59), and B3 (n = 45). No recombination events were found. Mutations were localized mainly in the VR-2 region, and the dN/dS ratio of 0.028 indicated the existence of purifying selection. Since the genetic diversity of SRLVs could make serological identification difficult, it is important to perform molecular characterization to ensure a more reliable diagnosis, to maintain flock health status, and for the application of local and national control programs.
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