Glycerol monolaurate prevents mucosal SIV transmission

Abstract

Although there has been great progress in treating human immunodeficiency virus 1 (HIV-1) infection, preventing transmission has thus far proven an elusive goal. Indeed, recent trials of a candidate vaccine and microbicide have been disappointing, both for want of efficacy and concerns about increased rates of transmission. Nonetheless, studies of vaginal transmission in the simian immunodeficiency virus (SIV)-rhesus macaque (Macacca mulatta) model point to opportunities at the earliest stages of infection in which a vaccine or microbicide might be protective, by limiting the expansion of infected founder populations at the portal of entry. Here we show in this SIV-macaque model, that an outside-in endocervical mucosal signalling system, involving MIP-3alpha (also known as CCL20), plasmacytoid dendritic cells and CCR5(+ )cell-attracting chemokines produced by these cells, in combination with the innate immune and inflammatory responses to infection in both cervix and vagina, recruits CD4(+) T cells to fuel this obligate expansion. We then show that glycerol monolaurate-a widely used antimicrobial compound with inhibitory activity against the production of MIP-3alpha and other proinflammatory cytokines-can inhibit mucosal signalling and the innate and inflammatory response to HIV-1 and SIV in vitro, and in vivo it can protect rhesus macaques from acute infection despite repeated intra-vaginal exposure to high doses of SIV. This new approach, plausibly linked to interfering with innate host responses that recruit the target cells necessary to establish systemic infection, opens a promising new avenue for the development of effective interventions to block HIV-1 mucosal transmission.

Figure 1

Mapping early expansion of infection in endocervix. SIV RNA+ cells appear black in transmitted light, green in reflected light and in maps. a–c. The arrow from thumbnail montage images (bottom of 1a) of cervix and vagina, 4–10dpi, points to an enlarged image and map of a single focus (box) of SIV RNA+ cells in endocervix, 4dpi. Counter clockwise-rotated image of focus (box) and map of X, Y coordinates (μm) of cell centroids to the right. d–e. Endocervical focus and map, 7dpi. f. Endocervical focus, 6dpi, SIV RNA+ cells (green) are concentrated in an inflammatory infiltrate (cells with dark staining nuclei).

Figure 2

Influx and infection of CD4+ T cells in cervix in early infection. a–c. Sections stained with anti-CD4. Note relative paucity of CD4+ cells in SIV-(negative animal) (a), or SIV inoculated animal 1 dpi (b), compared to increased numbers of CD4+ cells seen in infected animal at 4 dpi (c). d. SIV RNA+ cells in infiltrates are CD3+ T cells. Encircled SIV RNA+ cells (overlying black silver grains) are stained brown with anti-CD3.

Figure 3

pDCs, cytokines and chemokines associated with endocervical epithelium following exposure to SIV. a. Uninfected animal. b–c. Rapid accumulation of pDCs beneath endocervical epithelium at 1 dpi shown at 10X (b) and 40X (c) original magnifications. pDCs stained brown with anti-CD123. Arrow in c points to the location of pDCs beneath the epithelium. d–e. Arrows point to subepithelial pDCs stained red with anti-interferon-α at 1 dpi (d) or anti-MIP-1β (e). f. Arrow points to MIP-3α+ endocervical epithelium (red) at 1 dpi.

Figure 4

GML inhibits HIV-1 induced expression of MIP-3α and IL-8 in HVECs and in cervical vaginal fluids. a–b. R5 isolate of HIV-1 added to HVECs in the amounts indicated± GML. c–d. At the end of a six-month safety study, cervical vaginal fluids were collected with a swab that reproducibly adsorbed 0.1 ml of fluid from animals that received GML or K-Y warming gel in the am and pm on two successive days. MIP-3α and IL-8 measured by ELISA. Bars indicate standard errors of the mean.

Figure 5

GML prevents mucosal transmission and acute infection. a. Pilot experiment continuation of daily dosing safety study. Two animals treated with GML in K-Y warming gel (circles) and two treated with gel only (squares) were challenged twice (two arrows), 1-hour after treatment, with 10⁵ TCID₅₀ of SIV. Colors indicate individual animals. SIV RNA in plasma was measured to peak viremia, 14 dpi. b. Three animals treated with GML and three given K-Y warming gel were challenged as described in a. The animals that were not infected were treated and challenged again 4 weeks later, shown at the right.