Lucía Angélica García-Camacho

PPV5 NS1 is a nonstructural and multifunctional protein comprising helicase and nuclease domains. The helicase domain contains conserved motifs from superfamily 3 helicases, including Walker A, Walker B, Motif B’, Motif C, and Box VII, whereas the nuclease domain consists of glutamate, a HUH motif, lysine, and tyrosine. In Mexico, the reported prevalence of PPV5 is higher than in other countries, with notable amino acid differences compared with pathogenic PPVs. This study compares the helicase and nuclease domains from a full-length PPV5 NS1 sequence with porcine parvovirus 1 (PPV1) and canine parvovirus (CPV) to characterize the protein further and perform three-dimensional (3D) modeling using bioinformatic tools, including solvent-accessible surface area (SASA) and electrostatic potential assessments. The main findings highlight the ATP-binding pocket, showing electrostatic values in PPV5 that contrast with PPV1 and CPV. The electrostatic potential 3D models suggest those differences involve non-conserved regions. In particular, the PPV5 Box VII surface is predominantly negative due to a glutamate substitution at position 7. In the nuclease domain, the interaction with Mg²⁺ differs between PPV5 and pathogenic PPV. The electrostatic findings suggest that these differences may have functional implications for both domains, but confirmation must be completed with functional assays.

Las especies de Circovirus porcinos (Porcine circovirus, PCV por sus siglas en inglés) son ubicuos en la población porcina doméstica y silvestre. Hasta el momento, se han descrito cuatro especies (PCV1 al PCV4), siendo el PCV2 la especie más documentada por su participación en la Enfermedad Asociada a Circovirus Porcino cuya patología compleja conduce al desarrollo de diferentes presentaciones clínicas que causan pérdidas económicas importantes en la industria porcina. En el presente trabajo, se revisan los conceptos recabados con relación en los PCVs, incluyendo genotipos, interacción y replicación en las células del huésped, patogenia e inmunidad, así como la posible asociación del PCV3 y PCV4 con la enfermedad, enfatizando sobre la problemática de establecer dicho potencial debido a la alta tasa de coinfección entre los PCVs y otros virus patógenos y emergentes.

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.

Bovine leukemia virus (BLV) subclinical infection promotes persistent lymphocytosis (PL), which is related to susceptibility and progression to lymphoma. Moreover, lymphocyte counts directly correlate with BLV antibody titers and proviral load, and cell immune responses are considered atypical due to immune suppression. In order to determine the relationship of PL, antibody titers, and proviral load with interleukin (IL)-12, interferon (IFN)-gamma, IL-2, IL-4, IL-10, and transforming growth factor (TGF)-beta expression in a 3- month interval, 58 cows were selected (30 BLV1 and 28 BLV2) from a high-prevalence dairy herd to complete 3 monthly blood samplings for the assessment of PL, BLV antibody titers, BLV proviral load, and IL-12, IFN-gamma, IL-2, IL-4, IL-10, and TGF-b expression. At sampling conclusion, the BLV- infected cows were grouped according to PL, BLV proviral load, and BLV antibody titers as follows: BLV1PL1 (n = 16) and BLV1PL2 (n = 14); high proviral load (HPL) (n = 18) and low proviral load (LPL) (n = 13); high antibody titers (HAT) (n = 17) and low antibody titers (LAT) (n = 14). The BLV1PL1 cows showed significantly higher proviral load and antibody titers than the BLV1PL2 group; however, the former suggested spread presumably unrelated to lymphoma outcome, because HPL was observed in PL2 cows in the last sampling. Consistent with the data, a higher antibody response strongly indicated BLV susceptibility since it was linked to PL1 occurrence and a cytokine profile compatible with immune suppression. Furthermore, a reversion to lower antibody titers was observed in cows with HPL far ahead of time, most likely due to long-term immune suppression. In addition, high expression of IL-10 and TGF-beta was associated with reduced IL-12, IFN-gamma, IL-2, and IL-4 expression alongside PL, HAT, and HPL in BLV-infected cows, suggesting an IL-10- and TGF-beta-induced immune suppression. The IL-10 expression was increasing throughout, implying disease progression, as described. In conclusion, the proliferative expansion of lymphocytes known as PL might enhance a regulatory-rich cell population ( Bregs and/or Tregs) that secretes IL-10 and TGF-beta, leading to immune suppression. Further studies must be conducted regarding the types of regulatory cells involved in BLV-induced immune suppression.

Worldwide, many emerging porcine parvoviruses (PPVs) have been linked to porcine circovirus‐2 (PCV2) associated disease (PCVAD), which includes post‐weaning multi‐systemic wasting syndrome (PMWS), PCV2‐related reproductive failure (PCV2‐RF), as well as other syndromes. To determine the DNA prevalence of PPVs and their relationship with PMWS and PCV2‐RF in Mexico, 170 formalin‐fixed paraffin‐embedded tissues were selected from archival collections to detect PPVs using a nested polymerase chain reaction. The tissues were composed of 50 PMWS cases, 20 age‐matched tissues from healthy pigs, 56 PCV2‐related reproductive failure (PCV2⁺‐RF) cases, and 44 PCV2^‐‐RF cases. Overall, PPV2 and PPV6 were the most prevalent species (90.0% and 74.7%, respectively). In 8–11 week old pigs, the highest prevalence was for PPV6 and PPV3. Concerning reproductive failure, the PCV2‐affected farms had a significantly higher prevalence for PPV6 (61.6%) and PPV5 (36.4%) than the PCV2‐unaffected farms (35.0% and 5.0%, respectively). The concurrent infection rate was high, being significant for PPV2/PPV4 and PPV1/PPV5 within the PMWS cases and for PPV6/PPV5 among the PCV2⁺‐RF tissues. PPV5 showed a significant relationship with PMWS, whereas PPV5 and PPV6 were significant for PCVAD. The prevalence and coinfection rate of PPVs in Mexico were markedly higher than that described in other countries, denoting that PPV5 and PPV6 might have a potential role in PCVAD in Mexico. It is concluded that it is likely that the density population of pigs in Mexico is contributing to high PPV inter‐species and PCV2 coinfections which might lead to a different pathogenic outcome.

Genus Iotatorquevirus consists of 2 species, Torque teno sus virus 1a and Torque teno sus virus 1b, which are ubiquitous in swine populations, and are widely reported in association with porcine circovirus associated disease (PCVAD). To evaluate the relationship with PCVAD, 100 formalin-fixed paraffin-embedded tissue samples were used to detect both Iotatorquevirus species by nested PCR and sequencing. Sixty-eight PCVAD cases were selected as well as 32 porcine circovirus type 2 (PCV2) non-affected cases. Overall, 33 of the 100 cases were positive for Torque teno sus virus 1a and 8 of 100 were positive for Torque teno sus virus 1b. Only 24 of 68 (35%) PCVAD cases were positive for Torque teno sus virus 1a; 39% (9/23) of post-weaning multisystemic wasting syndrome, and 33% (15/45) of PCV2-associated reproductive failure cases. Among PCV2 non-affected cases, 28% were positive for Torque teno sus virus 1a and 6% were positive for Torque teno sus virus 1b. Torque teno sus virus 1b was not detected in PCV2-associated reproductive failure cases. Regardless of the PCV2-status, a lower frequency of both Iotatorquevirus species was found than depicted in other reports and there was no statistical relationship with PCVAD (χ 2 < 0.01). Given the worldwide genomic variability of Iotatorquevirus species, it is feasible that species prevalent in Mexico share a lower nucleotide sequence identity, leading to different pathogenic potential.