Deletion of gene OV132 attenuates Orf virus more effectively than gene OV112.

Orf virus (ORFV), a Parapoxvirus in Poxviridae, infects sheep and goats resulting in contagious pustular dermatitis. ORFV is regarded as a promising viral vector candidate for vaccine development and oncolytic virotherapy. Owing to their potential clinical application, safety concerns have become increasingly important. Deletion of either the OV132 (encoding vascular endothelial growth factor, VEGF) or OV112 (encoding the chemokine binding protein, CBP) genes reduced ORFV infectivity, which has been independently demonstrated in the NZ2 and NZ7 strains, respectively. This study revealed that the VEGF and CBP gene sequences of the local strain (TW/Hoping) shared a similarity of 47.01% with NZ2 and 90.56% with NZ7. Due to the high sequence divergence of these two immunoregulatory genes among orf viral strains, their contribution to the pathogenicity of Taiwanese ORFV isolates was comparatively characterized. Initially, two ORFV recombinants were generated, in which either the VEGF or CBP gene was deleted and replaced with the reporter gene EGFP. In vitro assays indicated that both the VEGF-deletion mutant ORFV-VEGFΔ-EGFP and the CBP deletion mutant ORFV-CBPΔ-EGFP were attenuated in cells. In particular, ORFV-VEGFΔ-EGFP significantly reduced plaque size and virus yield compared to ORFV-CBPΔ-EGFP and the wild-type control. Similarly, in vivo analysis revealed no virus yield in the goat skin biopsy infected by ORFV-VEGFΔ-EGFP, and significantly reduced the virus yield of ORFV-CBPΔ-EGFP relative to the wild-type control. These results confirmed the loss of virulence of both deletion mutants in the Hoping strain, whereas the VEGF-deletion mutant was more attenuated than the CBP deletion strain in both cell and goat models. KEY POINTS: • VEGF and CBP genes are crucial in ORFV pathogenesis in the TW/Hoping strain • The VEGF-deletion mutant virus was severely attenuated in both cell culture and animal models • Deletion mutant viruses are advantageous vectors for the development of vaccines and therapeutic regimens.

Potential Risk Factors Associated with Infection with Bovine Leukaemia Virus in Dairy and Beef Cattle in Taiwan.

Bovine leukaemia virus (BLV), which is classified as a Deltaretrovirus, is the aetiologic agent of enzootic bovine leukosis (EBL), a chronic lymphoproliferative disorder with a worldwide distribution. EBL is widespread in dairy herds and causes a direct economic impact due to reduced milk production and the early culling of BLV-infected cattle. The BLV infection status in Taiwan remains largely unknown; a high prevalence of BLV in dairy cows was recently revealed. The present study further investigated BLV infections in beef cattle. Surprisingly, the prevalence of BLV proviral DNA was as low as 11.8% (23/195), which is significantly lower than that noted in dairy cows, which was 42.5% (102/240) (p < 0.001). Factors associated with BLV infections were subsequently investigated. Due to the differences in herd management, an analysis of risk factors for a BLV infection was independently conducted in these two sectors. Several factors associated with a BLV infection were identified. Age was significantly associated with BLV infection status in dairy cows (p < 0.001) but not in beef cattle. A high prevalence of BLV was observed in cattle >15.5 months old (57.8%) compared with those ≤15.5 months old (11.4%). Moreover, after stratification analysis, based on the critical age of 15.5 months, as determined by the receiver operating characteristic (ROC) curve, a significantly higher BLV prevalence was demonstrated in lactating dairy cows, cattle undergoing bull breeding, heifers at older ages, and those undergoing routine rectal palpation. Due to the high prevalence of BLV in Taiwan, the development of an effective control program, based on the identified risk factors, is important for interrupting the routes of BLV transmission within herds.

Molecular Epidemiological and Serological Studies of Bovine Leukemia Virus in Taiwan Dairy Cattle.

Bovine leukemia virus (BLV) infection results in a decrease in milk yield and quality, a compromise in immunity, and shortening in the longevity of cows. The current status of BLV infection of dairy cattle in Taiwan remains unclear. To evaluate BLV infection, anti-BLV gp51 antibody and proviral DNA were detected. Surprisingly, the seroprevalence of BLV at the animal and herd level was as high as 81.8% (540/660 cattle) and 99.1% (109/110 herds), respectively. Among 152 blood samples analyzed, 132 (86.8%) were detected as positive for BLV-proviral DNA. When the complete blood count (CBC) was taken into account, the white blood cell (WBC) number appears to be the factor with the highest predicted potential for BLV infection. Moreover, based on receiver operating characteristic (ROC) curve analysis, the sensitivity and specificity are 72.0 and 75.0%, respectively, when the cut-off value of the WBC was set at 10.215 K/µL. Despite the co-circulation of genotype 1 and 3 in Taiwan, genotype 1 was much more prevalent (29/30). Taken together, due to the high prevalence of BLV, the identification of risk factors for interrupting the routes of transmission of BLV are critical for the control and prevention of further BLV infection.

Bartonella species in small mammals and their ectoparasites in Taiwan.

Bartonella spp. prevalence in small mammals and their ectoparasites was investigated in Taiwan. Blood samples were obtained from 66 rats, 20 shrews, 276 mites (Laelaps spp.), 74 fleas (Xenopsylla cheopis), 81 lice (Polyplax spp.), and 47 ticks (41 Dermacentor spp. and 6 Ixodes spp.). Bartonellae were isolated or detected in 27 (31.4%) animals. Bartonella DNA was detected in 48 (64.9%) fleas and 11 (64.7%) pooled lice samples, but not in mite and tick samples. Bartonella phoceensis, B. queenslandensis, B. tribocorum, B. elizabethae, and B. rattimassiliensis were isolated or detected in bacteremic mammals. For the first time in Taiwan, B. tribocorum, B. elizabethae, B. queenslandensis, and a B. rochalimae-like strain were detected in fleas, and B. tribocorum, B. phoceensis, and B. rattimassiliensis were detected in lice obtained from small mammals. A broader range of Bartonella species was identified in the ectoparasites than in the small mammals.