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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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Effect of SE on HIV infection. (A) Schema describing the experimental procedure. (B) Effect of treatment of virus stocks with 90% (v/v) of SE on R5 HIV-1 infection. TZM-bl cells were infected with the indicated dilutions of SE- or PBS-treated virus stocks. The inoculum was either removed after 2 hours of exposure (wash) or left on the cells. Shown are average β-galactosidase activities (n = 3) measured 2 days after virus exposure. RLU/s: relative light units per second. The numbers above the upper curve give n-fold enhancement of HIV infection by SE relative to that measured for the corresponding PBS control. (C) Metabolic activities of cells analysed in B. (D) Effect of low concentrations of SE on HIV infection. R5 HIV-1 stocks were treated with the indicated concentrations of SE, diluted and used to infect TZM-bl cells. The Y-axis gives average values of triplicate infections, and the X-axis gives the final dilution of the virus stocks. The infection levels were determined as described above. Percentages refer to the SE concentrations during virion treatment. The final concentrations in the cell culture are 15-fold lower.
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Figure 1: Effect of SE on HIV infection. (A) Schema describing the experimental procedure. (B) Effect of treatment of virus stocks with 90% (v/v) of SE on R5 HIV-1 infection. TZM-bl cells were infected with the indicated dilutions of SE- or PBS-treated virus stocks. The inoculum was either removed after 2 hours of exposure (wash) or left on the cells. Shown are average β-galactosidase activities (n = 3) measured 2 days after virus exposure. RLU/s: relative light units per second. The numbers above the upper curve give n-fold enhancement of HIV infection by SE relative to that measured for the corresponding PBS control. (C) Metabolic activities of cells analysed in B. (D) Effect of low concentrations of SE on HIV infection. R5 HIV-1 stocks were treated with the indicated concentrations of SE, diluted and used to infect TZM-bl cells. The Y-axis gives average values of triplicate infections, and the X-axis gives the final dilution of the virus stocks. The infection levels were determined as described above. Percentages refer to the SE concentrations during virion treatment. The final concentrations in the cell culture are 15-fold lower.

Mentions: It is long known that the intrinsic cytotoxicity of SE complicates its meaningful analysis in cell culture [17,26]. Thus, we first established experimental conditions circumventing this problem. Specifically, we reduced the final concentrations of SE in cell culture by pre-incubating SE with the HIV-1 virions (rather than the target cells) and adding small volumes (usually 20 μl) of these HIV/SE mixtures and serial dilutions thereof, to comparatively large (typically 280 μl) TZM-bl cell cultures (Figure 1A). In some aspects this approach resembles sexual transmission of HIV, where virus-containing SE is diluted by the female genital fluid present in the vaginal tract, which has a relatively large surface area of about 100 cm2 [27]. To further reduce cytotoxicity we removed the SE containing medium after 2 hours and cultured the cells in fresh medium containing gentamicin (to prevent bacterial outgrowth) until HIV-1 infection was assessed 2 to 3 days later. Under these conditions pre-treatment of virions with 90% (v/v) SE enhanced HIV-1 infection up to 40-fold compared to the untreated control (Figure 1B). In contrast, PBS-treated HIV-1 was more infectious than SE-treated virus when the inoculum was left on the target cells (Figure 1B) because final concentrations of SE as low as 1% were cytotoxic (Figure 1C). Thus, the cytotoxicity of SE may mask enhancing effects and produce misleading results, but can be overcome by reducing the concentration of SE and exposure time.


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)

Effect of SE on HIV infection. (A) Schema describing the experimental procedure. (B) Effect of treatment of virus stocks with 90% (v/v) of SE on R5 HIV-1 infection. TZM-bl cells were infected with the indicated dilutions of SE- or PBS-treated virus stocks. The inoculum was either removed after 2 hours of exposure (wash) or left on the cells. Shown are average β-galactosidase activities (n = 3) measured 2 days after virus exposure. RLU/s: relative light units per second. The numbers above the upper curve give n-fold enhancement of HIV infection by SE relative to that measured for the corresponding PBS control. (C) Metabolic activities of cells analysed in B. (D) Effect of low concentrations of SE on HIV infection. R5 HIV-1 stocks were treated with the indicated concentrations of SE, diluted and used to infect TZM-bl cells. The Y-axis gives average values of triplicate infections, and the X-axis gives the final dilution of the virus stocks. The infection levels were determined as described above. Percentages refer to the SE concentrations during virion treatment. The final concentrations in the cell culture are 15-fold lower.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 1: Effect of SE on HIV infection. (A) Schema describing the experimental procedure. (B) Effect of treatment of virus stocks with 90% (v/v) of SE on R5 HIV-1 infection. TZM-bl cells were infected with the indicated dilutions of SE- or PBS-treated virus stocks. The inoculum was either removed after 2 hours of exposure (wash) or left on the cells. Shown are average β-galactosidase activities (n = 3) measured 2 days after virus exposure. RLU/s: relative light units per second. The numbers above the upper curve give n-fold enhancement of HIV infection by SE relative to that measured for the corresponding PBS control. (C) Metabolic activities of cells analysed in B. (D) Effect of low concentrations of SE on HIV infection. R5 HIV-1 stocks were treated with the indicated concentrations of SE, diluted and used to infect TZM-bl cells. The Y-axis gives average values of triplicate infections, and the X-axis gives the final dilution of the virus stocks. The infection levels were determined as described above. Percentages refer to the SE concentrations during virion treatment. The final concentrations in the cell culture are 15-fold lower.
Mentions: It is long known that the intrinsic cytotoxicity of SE complicates its meaningful analysis in cell culture [17,26]. Thus, we first established experimental conditions circumventing this problem. Specifically, we reduced the final concentrations of SE in cell culture by pre-incubating SE with the HIV-1 virions (rather than the target cells) and adding small volumes (usually 20 μl) of these HIV/SE mixtures and serial dilutions thereof, to comparatively large (typically 280 μl) TZM-bl cell cultures (Figure 1A). In some aspects this approach resembles sexual transmission of HIV, where virus-containing SE is diluted by the female genital fluid present in the vaginal tract, which has a relatively large surface area of about 100 cm2 [27]. To further reduce cytotoxicity we removed the SE containing medium after 2 hours and cultured the cells in fresh medium containing gentamicin (to prevent bacterial outgrowth) until HIV-1 infection was assessed 2 to 3 days later. Under these conditions pre-treatment of virions with 90% (v/v) SE enhanced HIV-1 infection up to 40-fold compared to the untreated control (Figure 1B). In contrast, PBS-treated HIV-1 was more infectious than SE-treated virus when the inoculum was left on the target cells (Figure 1B) because final concentrations of SE as low as 1% were cytotoxic (Figure 1C). Thus, the cytotoxicity of SE may mask enhancing effects and produce misleading results, but can be overcome by reducing the concentration of SE and exposure time.

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