Genetic variation in Japanese Holstein cattle for EBL development.

BACKGROUND: Infection with bovine leukemia virus (BLV), the causative agent for enzootic bovine leukosis (EBL), is increasing in dairy farms of Japan. The tendency of tumor development following BLV infection in certain cow families and bull lines has previously been described. We therefore hypothesized the existence of a genetic component which differentiates cattle susceptibility to the disease. RESULTS: We analyzed routinely collected large-scale data including postmortem inspection data, which were combined with pedigree information and epidemiological data of BLV infection. A total of 6,022 postmortem inspection records of Holstein cattle, raised on 226 farms served by a regional abattoir over 10 years from 2004 to 2015, were analyzed for associations between sire information and EBL development. We then identified statistically the relative susceptibility to EBL development for the progeny of specific sires and paternal grandsires (PGSs). The heritability of EBL development was calculated as 0.19. Similarly, proviral loads (PVLs) of progeny from identified sires and PGSs were analyzed, but no significant differences were found. CONCLUSIONS: These observations suggest that because EBL development in our Holstein population is, at least in part, influenced by genetic factors independent of PVL levels, genetic improvement for lower incidence of EBL development in cattle notwithstanding BLV infection is possible.

A target enrichment high throughput sequencing system for characterization of BLV whole genome sequence, integration sites, clonality and host SNP.

Bovine leukemia virus (BLV) is an oncogenic retrovirus which induces malignant lymphoma termed enzootic bovine leukosis (EBL) after a long incubation period. Insertion sites of the BLV proviral genome as well as the associations between disease progression and polymorphisms of the virus and host genome are not fully understood. To characterize the biological coherence between virus and host, we developed a DNA-capture-seq approach, in which DNA probes were used to efficiently enrich target sequence reads from the next-generation sequencing (NGS) library. In addition, enriched reads can also be analyzed for detection of proviral integration sites and clonal expansion of infected cells since the reads include chimeric reads of the host and proviral genomes. To validate this DNA-capture-seq approach, a persistently BLV-infected fetal lamb kidney cell line (FLK-BLV), four EBL tumor samples and four non-EBL blood samples were analyzed to identify BLV integration sites. The results showed efficient enrichment of target sequence reads and oligoclonal integrations of the BLV proviral genome in the FLK-BLV cell line. Moreover, three out of four EBL tumor samples displayed multiple integration sites of the BLV proviral genome, while one sample displayed a single integration site. In this study, we found the evidence for the first time that the integrated provirus defective at the 5' end was present in the persistent lymphocytosis cattle. The efficient and sensitive identification of BLV variability, integration sites and clonal expansion described in this study provide support for use of this innovative tool for understanding the detailed mechanisms of BLV infection during the course of disease progression.

Increasing Bovine leukemia virus (BLV) proviral load is a risk factor for progression of Enzootic bovine leucosis: A prospective study in Japan.

Bovine leukemia virus (BLV) belongs to the genus Deltaretrovirus in the family Retroviridae, and is etiologically associated with Enzootic Bovine Leukosis (EBL). The majority of BLV-infected cattle remain asymptomatic throughout their productive lives, whereas approximately 5%-10% of infected cattle develop EBL. Data accumulated recently indicate that whole blood proviral load (PVL) levels of BLV-infected cattle could be an indicator of disease progression in the field. However, a few cross-sectional studies have been reported. Here, we prospectively evaluated 866 cattle enrolled between August 2015 and December 2015, and followed until November 2018, identifying 407 asymptomatic BLV-infected cattle. There were no significant differences in the median PVL level among the category of herd seroprevalence (p = 0.57), herd size (p = 0.19), nor among the category of past EBL history in the herd (p = 0.31). During the study period, 12 cattle developed EBL. The PVL levels of EBL cattle at the time of enrollment were significantly higher than that of cattle that did not progress to EBL (median, 90,695 vs 39,139 copies/105 cells, p = 0.0005). Moreover, the adjusted hazard ratio for the increase in PVL was 2.61 (95% CI, 1.51-4.53) as estimated by the Cox proportional hazards frailty model. These results indicate that a high PVL level is a significant risk factor for progression to EBL, and could potentially be used as an indicator for the identification of cattle to be culled from the herd long before the progression of EBL. This knowledge might be useful to design a strategy for decreasing economic loss from EBL or even eradicating it from herds.

Contrast visual acuity with bifocal contact lenses.

PURPOSE: To compare the quality of vision of a bifocal rigid gas-permeable contact lens versus a bifocal soft contact lens in subjects with presbyopia. METHODS: Sixteen healthy presbyopic subjects with no ocular disease but experienced with contact lens wear were enrolled in the study. Subjects randomly wore both types of bifocal lenses for 30 minutes with a washout period of 30 minutes each in a crossover manner. The primary outcome measure was the difference in contrast visual acuity. Distance and near contrast visual acuities with the two bifocal lens types were measured in different lighting environments and at multiple contrast levels. After the measurement, subjects were asked to rate their subjective vision by using the four categories with both lens types throughout the study. At the end of the study, subjects were also asked which of the two lens types they preferred. RESULTS: Under photopic conditions, distance and near visual acuities decreased at the 25% and 10% contrast levels, respectively, in subjects wearing bifocal soft contact lenses (P<0.05). Under scotopic conditions, distance visual acuity decreased at the 5% contrast level with the bifocal rigid gas-permeable contact lenses (P<0.05). For subjective responses of clarity, there were no differences between lens types for distance vision (P>0.05), but bifocal rigid gas-permeable lenses were clearer than bifocal soft contact lenses for near vision (P<0.05). CONCLUSIONS: Bifocal rigid gas-permeable contact lenses showed better visual performance than bifocal soft contact lenses did.

Comparison of corneal endothelial bleb formation and disappearance processes between rigid gas-permeable and soft contact lenses in three classes of dk/l.

PURPOSE: To compare corneal endothelial bleb formation and disappearance processes between rigid gas-permeable (RGP) contact lenses and soft contact lenses (SCL) in the same class of oxygen transmissibility (Dk/L). METHODS: Experiments were conducted on 20 eyes of 10 nonwearers of contact lenses using six kinds of RGP lenses or soft lenses with hyper (A), high (B), and medium (C) classes of Dk/L. Each subject kept their eyes closed for 20 minutes after putting on each test lens. Starting just after eye opening, the subjects' eyes were examined for blebs every 5 minutes by specular microscopy, and percentage area of the blebs were calculated. For control, the same eyes were also examined without contact lens wear. RESULTS: The percentage area of the blebs just after eye opening was 1.2% for RGP-A, 1.7% for SCL-A, 5.1% for RGP-B, 4.7% for SCL-B, 6.9% for RGP-C, 8.6% for SCL-C, and 0.4% for the control. The difference from the control became insignificant in the bleb disappearance process just after eye opening for RGP-A and SCL-A, after 5 minutes for RGP-B and SCL-B, after 10 minutes for RGP-C, and after 30 minutes for SCL-C. CONCLUSIONS: Regarding bleb formation and disappearance, there was no difference in influence on the corneal endothelium between RGP lenses and soft lenses with similar Dk/L in the high and hyper classes. In the medium class, however, it was suggested that RGP lenses may have less of an impact on the corneal endothelium than soft lenses do.