Colorectal Mucus Binds DC-SIGN and Inhibits HIV-1 Trans-Infection of CD4+ T-Lymphocytes

Abstract

Bodily secretions, including breast milk and semen, contain factors that modulate HIV-1 infection. Since anal intercourse caries one of the highest risks for HIV-1 transmission, our aim was to determine whether colorectal mucus (CM) also contains factors interfering with HIV-1 infection and replication. CM from a number of individuals was collected and tested for the capacity to bind DC-SIGN and inhibit HIV-1 cis- or trans-infection of CD4+ T-lymphocytes. To this end, a DC-SIGN binding ELISA, a gp140 trimer competition ELISA and HIV-1 capture/ transfer assays were utilized. Subsequently we aimed to identify the DC-SIGN binding component through biochemical characterization and mass spectrometry analysis. CM was shown to bind DC-SIGN and competes with HIV-1 gp140 trimer for binding. Pre-incubation of Raji-DC-SIGN cells or immature dendritic cells (iDCs) with CM potently inhibits DC-SIGN mediated trans-infection of CD4+ T-lymphocytes with CCR5 and CXCR4 using HIV-1 strains, while no effect on direct infection is observed. Preliminary biochemical characterization demonstrates that the component seems to be large (>100kDa), heat and proteinase K resistant, binds in a α1–3 mannose independent manner and is highly variant between individuals. Immunoprecipitation using DC-SIGN-Fc coated agarose beads followed by mass spectrometry indicated lactoferrin (fragments) and its receptor (intelectin-1) as candidates. Using ELISA we showed that lactoferrin levels within CM correlate with DC-SIGN binding capacity. In conclusion, CM can bind the C-type lectin DC-SIGN and block HIV-1 trans-infection of both CCR5 and CXCR4 using HIV-1 strains. Furthermore, our data indicate that lactoferrin is a DC-SIGN binding component of CM. These results indicate that CM has the potential to interfere with pathogen transmission and modulate immune responses at the colorectal mucosa.

Human Semen or Seminal Plasma Does Not Enhance HIV-1BaL Ex Vivo Infection of Human Colonic Explants

“…These results using freshly acquired human colorectal tissue and fresh as well as frozen/thawed semen showing lack of seminal enhancement of HIV-1 are similar to others utilizing cell lines, explants, and animal models. [6][7][8][9][10]17,34,35 In human colonic explants, these findings are similar to those by Dezzutti et al, 34 which showed no enhanced infection. Interestingly, rectosigmoid tissue is more prone than tonsillar and cervical tissue to R5 HIV-1 infection due to the high prevalence of available R5 cell targets and reduced chemokine blockade, 36,37 However, despite this increased gut lymphoid tissue infectibility, we did not see enhancement of viral replication early after HIV-1 exposure in fresh WS/SP (or frozen/thawed) conditions.…”

Cocaine Enhances DC to T-cell HIV-1 Transmission by Activating DC-SIGN/LARG/LSP1 Complex and Facilitating Infectious Synapse Formation

“…Furthermore, DC-SIGN mediated capture and internalization of HIV-1 particles by immature DCs alters the intracellular trafficking machinery, evades lysosomal degradation pathways and subsequently transfers virus to T-cells through infectious synapse283539484950. Several studies demonstrated that blocking of DC-SIGN significantly inhibited HIV-1 transmission from DC to T-cells5152. However, studies have also shown that DC-SIGN mediated internalized HIV-1 particles undergo degradation and subsequent presentation of HIV-1 antigen to T-cells535455.…”

Non-SMC Element 2 (NSMCE2) of the SMC5/6 Complex Helps to Resolve Topological Stress

“…Protein bands of interest were excised, alkylated and subjected to tryptic digestion according to standard protocols. Further mass spectrometry analysis was performed as described previously [64]. …”