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Open Access Research article

BLV-CoCoMo-qPCR: a useful tool for evaluating bovine leukemia virus infection status

Mayuko Jimba12, Shin-nosuke Takeshima12, Hironobu Murakami13, Junko Kohara4, Naohiko Kobayashi5, Tamako Matsuhashi5, Takashi Ohmori6, Tetsuo Nunoya6 and Yoko Aida12*

Author Affiliations

1 Viral Infectious Diseases Unit, RIKEN, 2–1 Hirosawa, Wako, Saitama 351-0198, Japan

2 Laboratory of Viral Infectious Diseases, Department of Medical Genome Sciences, Graduate School of Frontier Science, The University of Tokyo, Wako, Saitama 351-0198, Japan

3 Japan Foundation for AIDS Prevention, Chiyoda-ku, Tokyo, 101-0061, Japan

4 Animal Research Center, Hokkaido Research Organization, Shintoku, Hokkaido, 080-0038, Japan

5 Gifu Prefectural Livestock Research Institute, 4393–1 Makigahora, Kiyomi, Takayama, Gifu, 506-0101, Japan

6 Nippon Institute for Biological Science, 9-2221-1 Shinmachi Ome, Tokyo, 198-0024, Japan

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BMC Veterinary Research 2012, 8:167  doi:10.1186/1746-6148-8-167

Published: 21 September 2012

Abstract

Background

Bovine leukemia virus (BLV) is associated with enzootic bovine leukosis, which is the most common neoplastic disease of cattle. BLV infects cattle worldwide, imposing a severe economic impact on the dairy cattle industry. Recently, we developed a new quantitative real-time polymerase chain reaction (PCR) method using Coordination of Common Motifs (CoCoMo) primers to measure the proviral load of known and novel BLV variants in BLV-infected animals. Indeed, the assay was highly effective in detecting BLV in cattle from a range of international locations. This assay enabled us to demonstrate that proviral load correlates not only with BLV infection capacity as assessed by syncytium formation, but also with BLV disease progression. In this study, we compared the sensitivity of our BLV-CoCoMo-qPCR method for detecting BLV proviruses with the sensitivities of two real-time PCR systems, and also determined the differences of proviral load with serotests.

Results

BLV-CoCoMo-qPCR was found to be highly sensitive when compared with the real-time PCR-based TaqMan MGB assay developed by Lew et al. and the commercial TaKaRa cycleave PCR system. The BLV copy number determined by BLV-CoCoMo-qPCR was only partially correlated with the positive rate for anti-BLV antibody as determined by the enzyme-linked immunosorbent assay, passive hemagglutination reaction, or agar gel immunodiffusion. This result indicates that, although serotests are widely used for the diagnosis of BLV infection, it is difficult to detect BLV infection with confidence by using serological tests alone. Two cattle were experimentally infected with BLV. The kinetics of the provirus did not precisely correlate with the change in anti-BLV antibody production. Moreover, both reactions were different in cattle that carried different bovine leukocyte antigen (BoLA)-DRB3 genotypes.

Conclusions

Our results suggest that the quantitative measurement of proviral load by BLV-CoCoMo-qPCR is useful tool for evaluating the progression of BLV-induced disease. BLV-CoCoMo-qPCR allows us to monitor the spread of BLV infection in different viewpoint compared with classical serotest.

Keywords:
Bovine leukemia virus; Real-time PCR; Proviral load; Serological test; Experimental infection