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TLR2 and TLR4 triggering exerts contrasting effects with regard to HIV-1 infection of human dendritic cells and subsequent virus transfer to CD4+ T cells.

Thibault S, Fromentin R, Tardif MR, Tremblay MJ - Retrovirology (2009)

Bottom Line: Recognition of microbial products through Toll-like receptors (TLRs) initiates inflammatory responses orchestrated by innate immune cells such as dendritic cells (DCs).No noticeable and consistent effect was observed following engagement of TLR5, 7 and 9.Additional studies indicated that both HIV-1 infection of DCs and DC-mediated virus transmission to CD4+ T cells were reduced upon TLR4 triggering due to secretion of type-I interferons.

View Article: PubMed Central - HTML - PubMed

Affiliation: Faculté de Médecine, Université Laval, Québec, Canada. sandra.thibault@crchul.ulaval.ca

ABSTRACT

Background: Recognition of microbial products through Toll-like receptors (TLRs) initiates inflammatory responses orchestrated by innate immune cells such as dendritic cells (DCs). As these cells are patrolling mucosal surfaces, a portal of entry for various pathogens including human immunodeficiency virus type-1 (HIV-1), we investigated the impact of TLR stimulation on productive HIV-1 infection of DCs and viral spreading to CD4+ T cells.

Results: We report here that engagement of TLR2 on DCs increases HIV-1 transmission toward CD4+ T cells by primarily affecting de novo virus production by DCs. No noticeable and consistent effect was observed following engagement of TLR5, 7 and 9. Additional studies indicated that both HIV-1 infection of DCs and DC-mediated virus transmission to CD4+ T cells were reduced upon TLR4 triggering due to secretion of type-I interferons.

Conclusion: It can thus be proposed that exposure of DCs to TLR2-binding bacterial constituents derived, for example, from pathogens causing sexually transmissible infections, might influence the process of DC-mediated viral dissemination, a phenomenon that might contribute to a more rapid disease progression.

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Related in: MedlinePlus

TLR2 and 4 triggering increases viral entry in IM-MDDCs. A) IM-MDDCs were either left untreated (mock) or treated with TLR2 and 4 ligands for 2 hours and washed twice. Then, cells were pulsed with NL4-3/Balenv for 15, 30 and 60 min at 37°C. Next, the virus-cell mixture was washed extensively with PBS and trypsinized to remove uninternalized virus. Finally, cells were lysed and the p24 contents were measured by ELISA. Numbers depicted above bars represent fold increase relative to p24 levels in untreated control cells (considered as 1). The data shown represent the mean ± standard deviations of triplicate samples from 3 different donors.
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Figure 6: TLR2 and 4 triggering increases viral entry in IM-MDDCs. A) IM-MDDCs were either left untreated (mock) or treated with TLR2 and 4 ligands for 2 hours and washed twice. Then, cells were pulsed with NL4-3/Balenv for 15, 30 and 60 min at 37°C. Next, the virus-cell mixture was washed extensively with PBS and trypsinized to remove uninternalized virus. Finally, cells were lysed and the p24 contents were measured by ELISA. Numbers depicted above bars represent fold increase relative to p24 levels in untreated control cells (considered as 1). The data shown represent the mean ± standard deviations of triplicate samples from 3 different donors.

Mentions: To shed light on the mechanism(s) by which TLR2 and 4 triggering can affect de novo virus production, the extent of virus entry was quantified in IM-MDDCs. Data displayed in Fig. 6 indicate that virus internalization was increased at a comparable level by TLR2 and 4 agonists as compared to untreated cells. Since there is no linear relationship between internalization of viral particles in IM-MDDCs and productive infection, we investigated whether reverse transcription and integration processes are affected by a treatment with Pam3Csk4 and LPS. This issue was addressed through the use of a quantitative real-time PCR assay that has been described previously by Zack and colleagues [39]. Results displayed in Fig. 7A indicate that the amounts of early reverse transcripts were increased by a treatment with the TLR2 agonist while a diminution was seen with LPS. A similar trend was made when measuring the levels of late reverse transcripts (Fig. 7B). Integration of viral DNA was also promoted by the TLR2 agonist (Fig. 7C), whereas this process was significantly reduced upon a treatment with the TLR4 ligand LPS.


TLR2 and TLR4 triggering exerts contrasting effects with regard to HIV-1 infection of human dendritic cells and subsequent virus transfer to CD4+ T cells.

Thibault S, Fromentin R, Tardif MR, Tremblay MJ - Retrovirology (2009)

TLR2 and 4 triggering increases viral entry in IM-MDDCs. A) IM-MDDCs were either left untreated (mock) or treated with TLR2 and 4 ligands for 2 hours and washed twice. Then, cells were pulsed with NL4-3/Balenv for 15, 30 and 60 min at 37°C. Next, the virus-cell mixture was washed extensively with PBS and trypsinized to remove uninternalized virus. Finally, cells were lysed and the p24 contents were measured by ELISA. Numbers depicted above bars represent fold increase relative to p24 levels in untreated control cells (considered as 1). The data shown represent the mean ± standard deviations of triplicate samples from 3 different donors.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2691729&req=5

Figure 6: TLR2 and 4 triggering increases viral entry in IM-MDDCs. A) IM-MDDCs were either left untreated (mock) or treated with TLR2 and 4 ligands for 2 hours and washed twice. Then, cells were pulsed with NL4-3/Balenv for 15, 30 and 60 min at 37°C. Next, the virus-cell mixture was washed extensively with PBS and trypsinized to remove uninternalized virus. Finally, cells were lysed and the p24 contents were measured by ELISA. Numbers depicted above bars represent fold increase relative to p24 levels in untreated control cells (considered as 1). The data shown represent the mean ± standard deviations of triplicate samples from 3 different donors.
Mentions: To shed light on the mechanism(s) by which TLR2 and 4 triggering can affect de novo virus production, the extent of virus entry was quantified in IM-MDDCs. Data displayed in Fig. 6 indicate that virus internalization was increased at a comparable level by TLR2 and 4 agonists as compared to untreated cells. Since there is no linear relationship between internalization of viral particles in IM-MDDCs and productive infection, we investigated whether reverse transcription and integration processes are affected by a treatment with Pam3Csk4 and LPS. This issue was addressed through the use of a quantitative real-time PCR assay that has been described previously by Zack and colleagues [39]. Results displayed in Fig. 7A indicate that the amounts of early reverse transcripts were increased by a treatment with the TLR2 agonist while a diminution was seen with LPS. A similar trend was made when measuring the levels of late reverse transcripts (Fig. 7B). Integration of viral DNA was also promoted by the TLR2 agonist (Fig. 7C), whereas this process was significantly reduced upon a treatment with the TLR4 ligand LPS.

Bottom Line: Recognition of microbial products through Toll-like receptors (TLRs) initiates inflammatory responses orchestrated by innate immune cells such as dendritic cells (DCs).No noticeable and consistent effect was observed following engagement of TLR5, 7 and 9.Additional studies indicated that both HIV-1 infection of DCs and DC-mediated virus transmission to CD4+ T cells were reduced upon TLR4 triggering due to secretion of type-I interferons.

View Article: PubMed Central - HTML - PubMed

Affiliation: Faculté de Médecine, Université Laval, Québec, Canada. sandra.thibault@crchul.ulaval.ca

ABSTRACT

Background: Recognition of microbial products through Toll-like receptors (TLRs) initiates inflammatory responses orchestrated by innate immune cells such as dendritic cells (DCs). As these cells are patrolling mucosal surfaces, a portal of entry for various pathogens including human immunodeficiency virus type-1 (HIV-1), we investigated the impact of TLR stimulation on productive HIV-1 infection of DCs and viral spreading to CD4+ T cells.

Results: We report here that engagement of TLR2 on DCs increases HIV-1 transmission toward CD4+ T cells by primarily affecting de novo virus production by DCs. No noticeable and consistent effect was observed following engagement of TLR5, 7 and 9. Additional studies indicated that both HIV-1 infection of DCs and DC-mediated virus transmission to CD4+ T cells were reduced upon TLR4 triggering due to secretion of type-I interferons.

Conclusion: It can thus be proposed that exposure of DCs to TLR2-binding bacterial constituents derived, for example, from pathogens causing sexually transmissible infections, might influence the process of DC-mediated viral dissemination, a phenomenon that might contribute to a more rapid disease progression.

Show MeSH
Related in: MedlinePlus