Lactic acid bacteria are components of the gastrointestinal tract microbiota in both humans and animals and are widely used as probiotics. Lactobacillus is the most closely related genus to probiotic activity. It is capable of releasing membrane microvesicles (MVs), whose primary functions include carrying and transmitting antigens to host tissues and modulating host defense responses. In the present study, MVs were isolated from Lactobacillus acidophilus resident in the ileum of free-living rats, and their immunostimulant effect was evaluated in two biological models. MVs were characterized using SDS-PAGE electrophoresis, electron microscopy, and nanoparticle tracking analysis. In the first model, the immunostimulatory effect of MVs was evaluated on ovine abomasal explants, which had been previously stimulated with MVs and then challenged with third-stage larvae of Haemonchus contortus. This resulted in a decrease in the percentage of larval association and favored the migration of inflammatory cells to the infection site. In the second model, the macrophage cell line RAW 264.7 was stimulated with MVs to evaluate the expression of transcripts encoding IL-1β and TNF-α. MVs isolated from L. acidophilus demonstrate immunostimulatory and probiotic effects in the two biological models assessed. This suggested that the MVs possess similar immunostimulatory effects as those reported for the parent bacteria.

Porcine parvovirus 5 (PPV5) is an unclassified member of the family Parvoviridae with no reported pathogenicity, although it is associated with multisystemic, reproductive, and respiratory diseases. Its open reading frame 1 (ORF1) encodes non-structural protein 1 (NS1), which is predicted to have helicase activity that is essential for viral replication. This protein contains a C-motif with an invariant asparagine residue that forms the core of the enzyme's active site, in conjunction with the Walker A and B motifs. The aim of this study was the phylogenetic and molecular characterization of the NS1 of PPV5 through nested PCR and sequencing of three Mexican PPV5-positive samples. Subsequently, a phylogenetic tree, identity matrices of nucleotide and amino acid sequences, and a three-dimensional model of NS1 were constructed. The amplified sequences, which represented 96.9% of the PPV5 ORF1, occupied the same branch in the phylogenetic tree and exhibited the most nucleotide sequence similarity to the corresponding region of PPV4 and the most amino acid sequence similarity to the NS1 proteins of PPV4 and PPV6. A three-dimensional model of NS1 displayed a C-motif characteristic of superfamily 3 (SF3) helicases. The phylogenetic proximity of PPV5 to PPV4 and PPV6 suggests that it may belong to the genus Copiparvovirus. Further studies on helicases from viruses infecting domestic animals may be useful in developing antiviral drugs for both human and veterinary medicine.

The interaction between probiotic bacteria and the innate immune system is of increasing interest due to its capacity to modulate inflammatory and antimicrobial responses. The murine macrophage cell line RAW 264.7 is widely used to investigate the immunomodulatory effects of probiotic bacteria and their cell-free derivatives, such as membrane vesicles (MVs). In this study, we evaluated whether MVs derived from Lactobacillus acidophilus promote superior modulation of cytokine production and antimicrobial signaling in RAW 264.7 macrophages compared with whole cells (WCs). Our results show that L. acidophilus MVs exhibited direct bactericidal activity against Escherichia coli and induced a more selective and balanced cytokine profile than whole cells. These findings highlight the potential of probiotic-derived membrane vesicles as acellular immunomodulatory effectors for the development of novel cell-free biotherapeutic strategies.