Increased Expression on Innate Immune Factors in Placentas From HIV-Infected Mothers Concurs With Dampened Systemic Immune Activation

Abstract

Innate immunity is one of the main protection mechanisms against viral infections, but how this system works at the maternal-fetal interface, especially during HIV infection, is still poorly known. In this study, we investigated the relationship between pregnancy and innate mechanisms associated with HIV immunity by evaluating the expression of DAMPs, inflammasome components and type I/III IFNs in placenta and serum samples from HIV-infected mothers and exposed newborns. Our results showed that most of these factors, including HMGB1, IL-1, and IFN, were increased in placental villi from HIV-infected mothers. Curiously, however, these factors were simultaneously repressed in serum from HIV-infected mothers and their exposed newborns, suggesting that pregnancy could restrict HIV immune activation systemically but preserve the immune response at the placental level. An effective local antiviral status associated with a suppressed inflammatory environment can balance the maternal immune response, promoting homeostasis for fetal development and protection against HIV infection in neonates.

Keywords: DAMPs; HIV-infection; cord blood; inflammation; newborns; placental tissue.

Figure 1

DAMPs are up-regulated in placental chorionic villi but HMGB1 serum levels are decreased in HIV-infected mothers and CB. (A) mRNA expression levels of S100A8, S100A9, HMGB1, RAGE, TLR4, and TLR9 in decidua and chorionic villi from HIV-infected (gray bar, n = 7–10) and uninfected mothers (white bar, n = 5–10) was evaluated by RT qPCR. (B) HMGB1 expression was analyzed by immunohistochemistry in decidua and villi from HIV-infected (gray bar, n = 5) and uninfected mothers (white bar, n = 3). (C) HMGB1 levels in serum from HIV-infected (gray bar, n = 5–8) and uninfected mothers/newborns pair (white bar, n = 6–7) evaluated by ELISA. The detection limit for HMGB1 was 2.5 ng/mL. Data represent median values. Mann-Whitney U or Wilcoxon signed-rank test: *p < 0.05, **p < 0.01.

Figure 2

Differential expression of IL1B transcripts in placental chorionic villi. (A) mRNA expression levels of NLRP1, NLRP3, AIM-2, Caspase1, ASC, Pro-IL-1β, and Pro-IL-18 in decidua and placental chorionic villi from HIV-infected mothers (gray bar, n = 5–9) and control uninfected mothers (white bar, n = 5–8) was evaluated by RT qPCR. (B) NLRP1, NLRP3, AIM-2, caspase-1, IL-18, and IL-1β protein levels were analyzed by immunohistochemistry in decidua and placental chorionic villi from HIV-infected mothers (gray bar, n = 4–6) and uninfected mothers (white bar, n = 4–5). (C) Secretion levels of IL-1β and TNF in supernatants from placental explants from HIV-infected (gray bar, n = 4) and control uninfected mothers (white bar, n = 5) stimulated with TL4 agonist was evaluated by cytometric bead array. UNS = unstimulated. The detection limits were: IL-1β = 2.3 fg/mL; TNF = 0.7 pg/mL. Expression values are represented as median. Mann-Whitney U or Wilcoxon signed-rank test: *p < 0.05, **p < 0.01, ***p < 0.001.

Figure 3

Decreased serum levels of pro-inflammatory cytokines in HIV-infected mothers and exposed newborns. Serum samples from HIV-infected mothers and cord blood (CB) (gray bar, n = 18–23) and control uninfected mothers and CB (white bar, n = 18–29) was assessed for presence of IL-1β, IL-6, and IL-10 by cytometric bead array. Data represent median values. The detection limits were: IL-10 = 13.7 fg/mL; IL-6 = 68.4 fg/mL; IL-1β = 48.4 fg/mL. Mann-Whitney U or Wilcoxon signed-rank test: *p < 0.05, **p < 0.01, ***p < 0.001.

Figure 4

Upregulation of type I and III IFN molecules in placental tissue of HIV-infected mothers. (A) mRNA expression levels of IRF3, IRF7, IFNα, and IFN-λ in decidua and placental chorionic villi from HIV-infected mothers (gray bar, n = 6–11) and UN mothers (white bar, n = 3–9) were evaluated by RT qPCR. (B) IFN-β and STING proteins levels were analyzed by immunohistochemistry in decidua and placental chorionic villi from HIV-infected mothers (gray bar, n = 7–8) and UN mothers (white bar, n = 5). Expression levels are represented as median. Mann-Whitney U or Wilcoxon signed-rank test: *p < 0.05, **p < 0.01.

Figure 5

Decrease of tolerogenic factors in placental tissue from HIV-infected mothers. (A) Secretion levels of TGF-β and IL-10 in supernatant from placental explants from HIV-infected (gray bar, n = 4) and control uninfected mothers (white bar, n = 5) stimulated with TL4 agonist was evaluated by cytometric bead array. UNS, unstimulated. The detection limits were: IL-10, 0.13 pg/mL; TGF-β, 14.9 pg/mL. (B) mRNA expression levels of B7-H3 and HLA-G in decidua and placental chorionic villi from HIV-infected (gray bar, n = 9–11) and control uninfected mothers (white bar, n = 5–8) was evaluated by RT qPCR. (C) HLA-G protein levels were analyzed by immunohistochemistry in decidua and placental chorionic villi from HIV-infected (gray bar, n = 6) and uninfected mothers (white bar, n = 5). Expression values are represented as median. Mann-Whitney U or Wilcoxon signed-rank test: *p < 0.05, **p < 0.01, ***p < 0.001.