Altered apoptosis and proliferation in milk cells and PBMc from BLV-infected bovines with different proviral loads: Possible role of the BCL-2 family proteins, TNF-alpha, and receptors

Bovines infected by bovine leukemia virus (BLV) are characterized by presenting low proviral load (LPL) or high proviral load (HPL). It is reported that animals with HPL in peripheral blood mononuclear cells (PBMCs) present a decrease in apoptosis, an increase in viability and the proliferation rate, while animals that maintain an LPL have an intrinsic ability to control the infection, presenting an increased apoptosis rate of their PBMCs. However, there is little information on the effect of BLV on these mechanisms when the virus infects somatic milk cells (SC). This study investigates the mechanisms underlying apoptosis in milk and blood from BLV-infected animals with HPL and LPL. Relative levels of mRNA of tumor necrosis factor-α (TNF-α), TNF receptor 1 (TNF-RI), TNF receptor 2 (TNF-RII), anti-apoptotic B-cell lymphoma 2 protein (Bcl-2), and pro-apoptotic Bcl-2-like protein 4 (Bax) were measured in SC and PBMCs using quantitative reverse transcription-polymerase chain reaction (RT-qPCR) assay. A significant decrease in the expression of TNF-α in SC from HPL animals vs non-infected bovines was observed, but the infection in SC with BLV did not show a modulation on the expression of TNF receptors. A significant increase in TNF-RI expression in PBMCs from HPL bovines compared to LPL bovines was observed. No significant differences in PBMCs between HPL and LPL compared to non-infected animals concerning TNF-α, TNF-RI, and TNF-RII expression were found. There was a significant increase of both Bcl-2 and Bax in SC from LPL compared to non-infected bovines, but the Bcl-2/Bax ratio showed an anti-apoptotic profile in LPL and HPL bovines compared to non-infected ones. Reduced mRNA expression levels of Bax were determined in the PBMCs from HPL compared to LPL subjects. In contrast, BLV-infected bovines did not differ significantly in the mRNA expression of Bax compared to non-infected bovines. Our data suggest that the increased mRNA expression of Bax corresponds to the late lactation state of bovine evaluated and the exacerbated increase of mRNA expression of Bcl-2 may be one of the mechanisms for the negative apoptosis regulation in the mammary gland induced by BLV infection. These results provide new insights into the mechanism of mammary cell death in HPL and LPL BLV-infected bovine mammary gland cells during lactation.

Two immunomodulators, curcumin and sulfasalazine, enhance IDV antiretroviral activity in HIV-1 persistently infected cells

Since the appearance of resistance to antiretroviral treatment is unavoidable, the host cell's transcription factor NF-kappaB is a novel HIV target. The goal of this study was to characterize the effect of two immunomodulators, curcumin (Cur) and sulfasalazine (Sul), with a protease inhibitor, indinavir (IDV), on HIV-1 persistently infected CD4+ T-cells. Viral p24 antigen production, viral infectivity (tested on MAGI cells) and viral relative infectivity (viral infectivity/p24) were analysed. When used alone, both immunomodulators were able to reduce viral infectivity. When in combination, both 10 microM IDV plus 10 microM Cur and 10 microM IDV plus 250 microM Sul showed a significant reduction in viral infectivity and viral relative infectivity when compared to the reduction produced by IDV alone. Thus, the use of immunomodulators with IDV could help to reduce HIV-1 production in persistently infected cells.

Development and evaluation of a highly sensitive and specific blocking enzyme-linked immunosorbent assay and polymerase chain reaction assay for diagnosis of bovine leukemia virus infection in cattle

OBJECTIVE

To develop a blocking ELISA for detection of bovine leukemia virus (BLV) antibodies that is comparable to a radioimmunoprecipitation (RIP) assay, to evaluate use of this ELISA for identification of BLV-infected herds, and to develop a polymerase chain reaction (PCR) assay for direct diagnosis of infection with BLV.

SAMPLE POPULATION

Serum samples and pooled bulk-tank milk samples from cattle.

PROCEDURE

The blocking ELISA was developed, using BLV gp51 as antigen, captured by a selected bovine polyclonal serum. A nested PCR was conducted with primers specific for a segment of the pol region of the BLV genome.

RESULTS

Sensitivity and specificity of the ELISA were comparable to those of the RIP assay. Use of the ELISA on pooled milk samples allowed identification of herds in which prevalence of BLV infection among lactating cows was as low as 2.5%. Pooled milk samples from BLV-free herds did not react in the ELISA. All cattle that had positive results for the nested PCR had BLV antibodies, but cattle with consistantly low antibody titers required examination of sequential DNA samples to detect viral sequences. None of the 63 antibody-negative cattle had positive results for the PCR.

CONCLUSIONS AND CLINICAL RELEVANCE

This ELISA is a highly specific and sensitive assay for the detection of BLV antibodies in serum and milk samples of cattle. Examination of pooled milk samples with the ELISA provides a reliable, practical, and economic procedure for identification of BLV-infected herds. The nested PCR also constitutes a specific procedure for direct diagnosis of infection with BLV.

[Bovine leukemia virus (BLV): prevalence in the Cuenca Lechera Mar y Sierras from 1994 to 1995]

The Cuenca Lechera Mar y Sierras (CLMS) includes about 300 dairy farms located in the counties of Tandil, Balcarce, Juarez, Ayacucho, General Pueyrredón, Gonzalez Chavez and Necochea, in the province of Buenos Aires. The purpose of this investigation was to determine the prevalence of infection caused by Bovine Leukemia Virus (BLV) in the CLMS. We investigated the presence of anti-BLV antibodies in 4,203 milk samples taken from 73 dairy farms belonging to the CLMS. An indirect ELISA, which is described and evaluated in this paper, was used to test the antibodies in milk. We classified the dairy farms according to their rate of infection. The percentage of dairy farms free of infection resulted in 31.50. On the other hand, 49.40% of the dairy farms showed a figure between 1% and 15% of infected cattle; 17.80% between 16% and 30%, and the remaining 1.30% turned out more than 30% of infected cattle. If compared with data obtained in the 1979-1981 period, which showed that 95.65% of the dairy farms was BLV-free, it is clear that a dramatic progress of the BLV infection has occurred for the last 15 years. Nevertheless, the CLMS is in a privileged position so as to incorporate an inexpensive control plan to eradicate the BLV infection, as almost 1/3 of its dairy farms is still BLV-free and 49.40% still has a low rate of BLV infection. Only about 20% of the dairy farms would require costly strategies of control.