Antibody response against three widespread bovine viruses is not impaired in Holstein cattle carrying bovine leukocyte antigen DRB3.2 alleles associated with bovine leukemia virus resistance.

Due to the wide dissemination of bovine leukemia virus (BLV) infection among dairy cattle, control and eradication programs based on serological detection of infected cattle and subsequent culling face a major economic task. In Argentina, genetic selection of cattle carrying alleles of the bovine leukocyte antigen (BoLA) DRB3.2 gene associated with BLV-infection resistance, like *0902, emerges as the best additional tool toward controlling virus spread. A potential risk in expanding or segregating BoLA selected populations of cattle is that it might increase susceptibility to other common viruses. Special concern raises the strong association found between low proviral load and low antibody titer against major BLV structural proteins. This phenomenon might depend on host genetic factors influencing other viruses requiring, unlike BLV, strong and long-lasting humoral immune response to prevent infection. In this study, we demonstrate that there is no association among neutralizing antibody titers against foot and mouth disease virus, bovine viral diarrhea virus, or bovine herpesvirus type 1 and polymorphism of the BoLA DRB3.2 gene. Conversely, there is strong association between BoLA DRB3.2*0902 and low antibody titers against 2 BLV structural proteins--env gp51 and gag p24--to date, the best BLV resistance marker. There is also significant association between low antibody titers against gp51 and p24 and BoLA DRB3.2*1701 and low antibody titers against p24 and BoLA DRB3.2*1101 or 02. Our data suggest that increasing BoLA-selected BLV-resistant cattle or segregating BoLA-associated alleles to BLV susceptibility would not affect the resistance or the predisposition to bovine viral diarrhea virus, bovine herpesvirus type 1, or foot and mouth disease virus infection.

Juliarena MA ，Poli M ，Ceriani C ，Sala L ，Rodríguez E ，Gutierrez S ，Dolcini G ，Odeon A ，Esteban EN ... -  《-》

Identification of bovine leukocyte antigen class II haplotypes associated with variations in bovine leukemia virus proviral load in Japanese Black cattle.

Bovine leukemia virus (BLV) is the etiological agent of enzootic bovine leukosis, which is the most common neoplastic disease of cattle. Bovine leukocyte antigen (BoLA) is strongly involved in the subclinical progression of BLV infections. Recent studies show that the BoLA-DRB3 gene might play a direct role in controlling the number of BLV-infected peripheral B lymphocytes in vivo in Holstein cattle. However, the specific BoLA class II allele and DRB3-DQA1 haplotypes determining the BLV proviral load in Japanese Black cattle are yet to be identified. In this study, we focused on the association of BLV proviral load and polymorphism of BoLA class II in Japanese Black cattle. We genotyped 186 BLV-infected, clinically normal cattle for BoLA-DRB3 and BoLA-DQA1 using a polymerase chain reaction-sequence-based typing method. BoLA-DRB3*0902 and BoLA-DRB3*1101 were associated with a low proviral load (LPVL), and BoLA-DRB3*1601 was associated with a high proviral load (HPVL). Furthermore, BoLA-DQA1*0204 and BoLA-DQA1*10012 were related to LPVL and HPVL, respectively. Furthermore, we confirmed the correlation between the DRB3-DQA1 haplotype and BLV proviral load. Two haplotypes, namely 0902B or C (DRB3*0902-DQA1*0204) and 1101A (DRB3*1101-DQA1*10011), were associated with a low BLV proviral load, whereas one haplotype 1601B (DRB3*1601-DQA1*10012) was associated with a high BLV proviral load. We conclude that resistance is a dominant trait and susceptibility is a recessive trait. Additionally, resistant alleles were common between Japanese Black and Holstein cattle, and susceptible alleles differed. This is the first report to identify an association between the DRB3-DQA1 haplotype and variations in BLV proviral load.

Miyasaka T ，Takeshima SN ，Jimba M ，Matsumoto Y ，Kobayashi N ，Matsuhashi T ，Sentsui H ，Aida Y ... -  《-》

Association of BLV infection profiles with alleles of the BoLA-DRB3.2 gene.

Bovine leukaemia virus (BLV) causes lymphosarcoma and persistent lymphocytosis (PL). Some MHC class II gene polymorphisms have been associated with resistance and susceptibility to the development of lymphosarcoma and PL, as well as with a reduced number of circulating BLV-infected lymphocytes. Previously, 230 BLV-infected Holstein cattle were classified into two infection profiles characterized by low and high proviral loads (LPL and HPL respectively). Here, the influence of the polymorphism at the BoLA-DRB3.2* gene of these animals was examined. After genotyping, the association between the BoLA-DRB3.2* alleles and the BLV infection profile was determined as the odds ratio (OR). Two subtypes of allele *11 were identified (ISAG*0901 and *0902). Allele ISAG*0902 showed a stronger association with the LPL profile (OR = 8.24; P < 0.0001) than allele *11 itself (OR = 5.82; P < 0.0001). Allele ISAG*1701 (*12) also showed significant association with the LPL profile (OR = 3.46; P < 0.0055). Only one allele, ISAG*1501 or 03 (*16), showed significant association with HPL (OR = 0.36; P < 0.0005). The DRB3.2* alleles were assigned to three categories: resistant (R), susceptible (S) and neutral (N). Based on their DRB3 genotypes, cattle were classified as homozygous or heterozygous. The RR and RN genotypes were associated with the LPL profile, while the SS and NS genotypes were associated with the HPL profile. The RS genotype could not be associated with any particular profile. Our results show that allele ISAG*0902 appears to be the best BLV resistance marker in Holstein cattle.

Juliarena MA ，Poli M ，Sala L ，Ceriani C ，Gutierrez S ，Dolcini G ，Rodríguez EM ，Mariño B ，Rodríguez-Dubra C ，Esteban EN ... -  《-》

Co-infection with Mycobacterium bovis does not alter the response to bovine leukemia virus in BoLA DRB3*0902, genetically resistant cattle.

High proviral load (HPL) profile in bovine leukemia virus infected animals poses increased risk of transmission, and development of HPL or low proviral load (LPL) profile may be attributed to host genetics. Genetic resistance and susceptibility has been mapped to the Major Histocompatibility Complex class II DRB3 gene (BoLA DRB3). The aim of this work was to determine the effect of Mycobacterium bovis infection on certain virological and host immunological parameters of BLV experimental infection. Twenty-six Argentinian Holstein calves carrying the resistance-associated marker allele BoLA DRB3*0902, susceptibility-associated marker allele BoLA DRB3*1501, or neutral BoLA DRB3 alleles, exposed to M. bovis were used. Twenty calves were inoculated with BLV, three were naturally infected and other three were BLV-negative. Seven from twenty six (27%) of the animals resulted positive to the PPD test. The proviral load, absolute leukocyte and lymphocyte counts, time to seroconversion, antibody titer against BLV, and viral antigen expression in vitro at various times post inoculation were determined and compared between PPD+ and PPD- animals. From a total of 23 BLV positive animals (naturally and experimentally infected), 13 (56.5%) developed HPL, and 10 (43.5%) developed LPL. None of the investigated parameters were affected by infection with M. bovis. We concluded that the ability of cattle carrying resistance-associated marker to control BLV and to progress towards a LPL phenotype was not altered by M. bovis co-infection.

Lützelschwab CM ，Forletti A ，Cepeda R ，Esteban EN ，Confalonieri O ，Gutiérrez SE ... -  《-》

Bovine leukemia virus proviral load is more strongly associated with bovine major histocompatibility complex class II DRB3 polymorphism than with DQA1 polymorphism in Holstein cow in Japan.

Bovine leukemia virus (BLV) causes enzootic bovine leukosis and is closely related to the human T-lymphotropic virus. Bovine major histocompatibility complex (BoLAs) are used extensively as markers of disease and immunological traits in cattle. For BLV diagnosis, proviral load is a major diagnosis index for the determination of disease progression and transmission risk. Therefore, we investigated the frequency of BoLA-DRB3 alleles, BoLA-DQA1 alleles, and haplotypes of BoLA class II isolated from the heads of 910 BLV-infected cows out of 1290 cows assessed from BLV-positive farms, in a nationwide survey from 2011 to 2014 in Japan. Our aim was to identify BoLA class II polymorphisms associated with the BLV proviral load in the Holstein cow. The study examined 569 cows with a high proviral load and 341 cows with a low proviral load. Using the highest odds ratio (OR) as a comparison index, we confirmed that BoLA-DRB3 was the best marker for determining which cow spread the BLV (OR 13.9 for BoLA-DRB3, OR 11.5 for BoLA-DQA1, and OR 6.2 for BoLA class II haplotype). In addition, DRB3*002:01, *009:02, *012:01, *014:01, and *015:01 were determined as BLV provirus associated alleles. BoLA-DRB3*002:01, *009:02, and *014:01 were determined as resistant alleles (OR > 1), and BoLA-DRB3*012:01 and *015:01 were determined as susceptible alleles (OR < 1). In this study, we showed that BoLA-DRB3 was a good marker for determining which cow spread BLV, and we found not only one resistant allele (BoLA-DRB3*009:02), but also two other disease-resistant alleles and two disease-susceptible alleles. This designation of major alleles as markers of susceptibility or resistance can allow the determination of the susceptibility or resistance of most cows to disease. Overall, the results of this study may be useful in eliminating BLV from farms without having to separate cows into several cowsheds.

Takeshima SN ，Ohno A ，Aida Y 《Retrovirology》