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Semen-mediated enhancement of HIV infection is donor-dependent and correlates with the levels of SEVI.

Kim KA, Yolamanova M, Zirafi O, Roan NR, Staendker L, Forssmann WG, Burgener A, Dejucq-Rainsford N, Hahn BH, Shaw GM, Greene WC, Kirchhoff F, Münch J - Retrovirology (2010)

Bottom Line: Despite its importance for the global spread of HIV-1, however, the effect of semen on virus infection is controversial.We show that semen rapidly and effectively enhances the infectivity of HIV-1, HIV-2, and SIV.Our results show that semen strongly enhances the infectivity of HIV-1 and other primate lentiviruses and that SEVI contributes to this effect.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Molecular Virology, University Hospital Ulm, 89081 Ulm, Germany.

ABSTRACT

Background: HIV-1 is usually transmitted in the presence of semen. We have shown that semen boosts HIV-1 infection and contains fragments of prostatic acid phosphatase (PAP) forming amyloid aggregates termed SEVI (semen-derived enhancer of viral infection) that promote virion attachment to target cells. Despite its importance for the global spread of HIV-1, however, the effect of semen on virus infection is controversial.

Results: Here, we established methods allowing the meaningful analysis of semen by minimizing its cytotoxic effects and partly recapitulating the conditions encountered during sexual HIV-1 transmission. We show that semen rapidly and effectively enhances the infectivity of HIV-1, HIV-2, and SIV. This enhancement occurs independently of the viral genotype and coreceptor tropism as well as the virus producer and target cell type. Semen-mediated enhancement of HIV-1 infection was also observed under acidic pH conditions and in the presence of vaginal fluid. We further show that the potency of semen in boosting HIV-1 infection is donor dependent and correlates with the levels of SEVI.

Conclusions: Our results show that semen strongly enhances the infectivity of HIV-1 and other primate lentiviruses and that SEVI contributes to this effect. Thus, SEVI may play an important role in the sexual transmission of HIV-1 and addition of SEVI inhibitors to microbicides may improve their efficacy.

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Adding SE or SE-P directly to target cells results in reduced metabolic activity and HIV infection rates. (A) Schematic outline of the experiment. TZM-bl cells were incubated with different dilutions of SE or SE-P and subsequently infected with HIV-1. (B) Infection rates and (C) metabolic activities were determined after 1 (upper panel) or 3 days (lower panel). (D) Correlation between Tat-driven reporter activities ("infection") and the metabolic activities of the target cells. Values were derived from the experiments shown in panels B and C, and are shown relative to those obtained in the absence of SE or SE-P (100%).
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Figure 6: Adding SE or SE-P directly to target cells results in reduced metabolic activity and HIV infection rates. (A) Schematic outline of the experiment. TZM-bl cells were incubated with different dilutions of SE or SE-P and subsequently infected with HIV-1. (B) Infection rates and (C) metabolic activities were determined after 1 (upper panel) or 3 days (lower panel). (D) Correlation between Tat-driven reporter activities ("infection") and the metabolic activities of the target cells. Values were derived from the experiments shown in panels B and C, and are shown relative to those obtained in the absence of SE or SE-P (100%).

Mentions: Next, we evaluated results of Martellini and coworkers suggesting that SE-P may inhibit HIV-1 [15]. In this study, the target cells and not the HIV-1 virions were treated with SE-P. To assess the effect of SE on the susceptibility of target cells to HIV-1 infection, we used a flow cytometry-based HIV-1 virion-fusion assay [35]. This system allows to directly measure virion fusion with the target cells and minimizes cytotoxic effects because the cells are only exposed to SE for short time periods. Primary endometrial CD4+ T cells were either PBS-treated or treated with SE, washed, exposed to HIV-1 NL4-3 BlaM-Vpr virions for 4 hours and loaded with CCF2/AM dye. In agreement with published data [20,24], treatment with 10% SE enhanced the susceptibility of the cells to HIV-1 infection by 5-fold (Additional file 1 Figure S7). This effect is lower than that observed in HIV-1 infection assays because the fusion assay requires higher viral doses. Nonetheless, our data show that treatment with SE enhances rather than reduces the susceptibility of cells to HIV-1 infection. To elucidate why Martellini and coworkers obtained different results, we repeated the experiments following their protocols (Figure 6A). In agreement with their findings, treatment of the TZM-bl indicator cells with SE-P and SE and subsequent infection with HIV-1 resulted in reduced levels of Tat-driven reporter gene activity suggesting inhibition of virus infection (Figure 6B). At one day post-infection (the time point examined in the previous study) cytotoxic effects were observed at about 4-fold higher concentrations of SE-P and SE compared to those required to inhibit virus infection (Figure 6C, upper). At 3 days post-infection cytotoxic effects become more apparent (Figure 6C, lower) and the metabolic activity of the cells correlated significantly with the Tat-driven reporter gene activities (Figure 6D). Thus, a decreased metabolic activity of the target cells rather than a specific anti-HIV activity of SE-P or SE may account for the reduced levels of Tat-driven reporter gene activity in this assay. Efficient viral gene expression is dependent on the "fitness" of the cells and is highly sensitive to cytotoxic or cytostatic effects and experimental conditions just at the threshold of cytotoxicity may yield misleading results.


Semen-mediated enhancement of HIV infection is donor-dependent and correlates with the levels of SEVI.

Kim KA, Yolamanova M, Zirafi O, Roan NR, Staendker L, Forssmann WG, Burgener A, Dejucq-Rainsford N, Hahn BH, Shaw GM, Greene WC, Kirchhoff F, Münch J - Retrovirology (2010)

Adding SE or SE-P directly to target cells results in reduced metabolic activity and HIV infection rates. (A) Schematic outline of the experiment. TZM-bl cells were incubated with different dilutions of SE or SE-P and subsequently infected with HIV-1. (B) Infection rates and (C) metabolic activities were determined after 1 (upper panel) or 3 days (lower panel). (D) Correlation between Tat-driven reporter activities ("infection") and the metabolic activities of the target cells. Values were derived from the experiments shown in panels B and C, and are shown relative to those obtained in the absence of SE or SE-P (100%).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2914040&req=5

Figure 6: Adding SE or SE-P directly to target cells results in reduced metabolic activity and HIV infection rates. (A) Schematic outline of the experiment. TZM-bl cells were incubated with different dilutions of SE or SE-P and subsequently infected with HIV-1. (B) Infection rates and (C) metabolic activities were determined after 1 (upper panel) or 3 days (lower panel). (D) Correlation between Tat-driven reporter activities ("infection") and the metabolic activities of the target cells. Values were derived from the experiments shown in panels B and C, and are shown relative to those obtained in the absence of SE or SE-P (100%).
Mentions: Next, we evaluated results of Martellini and coworkers suggesting that SE-P may inhibit HIV-1 [15]. In this study, the target cells and not the HIV-1 virions were treated with SE-P. To assess the effect of SE on the susceptibility of target cells to HIV-1 infection, we used a flow cytometry-based HIV-1 virion-fusion assay [35]. This system allows to directly measure virion fusion with the target cells and minimizes cytotoxic effects because the cells are only exposed to SE for short time periods. Primary endometrial CD4+ T cells were either PBS-treated or treated with SE, washed, exposed to HIV-1 NL4-3 BlaM-Vpr virions for 4 hours and loaded with CCF2/AM dye. In agreement with published data [20,24], treatment with 10% SE enhanced the susceptibility of the cells to HIV-1 infection by 5-fold (Additional file 1 Figure S7). This effect is lower than that observed in HIV-1 infection assays because the fusion assay requires higher viral doses. Nonetheless, our data show that treatment with SE enhances rather than reduces the susceptibility of cells to HIV-1 infection. To elucidate why Martellini and coworkers obtained different results, we repeated the experiments following their protocols (Figure 6A). In agreement with their findings, treatment of the TZM-bl indicator cells with SE-P and SE and subsequent infection with HIV-1 resulted in reduced levels of Tat-driven reporter gene activity suggesting inhibition of virus infection (Figure 6B). At one day post-infection (the time point examined in the previous study) cytotoxic effects were observed at about 4-fold higher concentrations of SE-P and SE compared to those required to inhibit virus infection (Figure 6C, upper). At 3 days post-infection cytotoxic effects become more apparent (Figure 6C, lower) and the metabolic activity of the cells correlated significantly with the Tat-driven reporter gene activities (Figure 6D). Thus, a decreased metabolic activity of the target cells rather than a specific anti-HIV activity of SE-P or SE may account for the reduced levels of Tat-driven reporter gene activity in this assay. Efficient viral gene expression is dependent on the "fitness" of the cells and is highly sensitive to cytotoxic or cytostatic effects and experimental conditions just at the threshold of cytotoxicity may yield misleading results.

Bottom Line: Despite its importance for the global spread of HIV-1, however, the effect of semen on virus infection is controversial.We show that semen rapidly and effectively enhances the infectivity of HIV-1, HIV-2, and SIV.Our results show that semen strongly enhances the infectivity of HIV-1 and other primate lentiviruses and that SEVI contributes to this effect.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Molecular Virology, University Hospital Ulm, 89081 Ulm, Germany.

ABSTRACT

Background: HIV-1 is usually transmitted in the presence of semen. We have shown that semen boosts HIV-1 infection and contains fragments of prostatic acid phosphatase (PAP) forming amyloid aggregates termed SEVI (semen-derived enhancer of viral infection) that promote virion attachment to target cells. Despite its importance for the global spread of HIV-1, however, the effect of semen on virus infection is controversial.

Results: Here, we established methods allowing the meaningful analysis of semen by minimizing its cytotoxic effects and partly recapitulating the conditions encountered during sexual HIV-1 transmission. We show that semen rapidly and effectively enhances the infectivity of HIV-1, HIV-2, and SIV. This enhancement occurs independently of the viral genotype and coreceptor tropism as well as the virus producer and target cell type. Semen-mediated enhancement of HIV-1 infection was also observed under acidic pH conditions and in the presence of vaginal fluid. We further show that the potency of semen in boosting HIV-1 infection is donor dependent and correlates with the levels of SEVI.

Conclusions: Our results show that semen strongly enhances the infectivity of HIV-1 and other primate lentiviruses and that SEVI contributes to this effect. Thus, SEVI may play an important role in the sexual transmission of HIV-1 and addition of SEVI inhibitors to microbicides may improve their efficacy.

Show MeSH
Related in: MedlinePlus