Glycerol monolaurate prevents mucosal SIV transmission.

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.

Glycerol monolaurate does not alter rhesus macaque (Macaca mulatta) vaginal lactobacilli and is safe for chronic use.

Glycerol monolaurate (GML) is a fatty acid monoester that inhibits growth and exotoxin production of vaginal pathogens and cytokine production by vaginal epithelial cells. Because of these activities, and because of the importance of cytokine-mediated immune activation in human immunodeficiency virus type 1 (HIV-1) transmission to women, our laboratories are performing studies on the potential efficacy of GML as a topical microbicide to interfere with HIV-1 transmission in the simian immunodeficiency virus-rhesus macaque model. While GML is generally recognized as safe by the FDA for topical use, its safety for chronic use and effects on normal vaginal microflora in this animal model have not been evaluated. GML was therefore tested both in vitro for its effects on vaginal flora lactobacilli and in vivo as a 5% gel administered vaginally to monkeys. In vitro studies demonstrated that lactobacilli are not killed by GML; GML blocks the loss of their viability in stationary phase and does not interfere with lactic acid production. GML (5% gel) does not quantitatively alter monkey aerobic vaginal microflora compared to vehicle control gel. Lactobacilli and coagulase-negative staphylococci are the dominant vaginal aerobic microflora, with beta-hemolytic streptococci, Staphylococcus aureus, and yeasts sporadically present; gram-negative rods are not part of their vaginal flora. Colposcopy and biopsy studies indicate that GML does not alter normal mucosal integrity and does not induce inflammation; instead, GML reduces epithelial cell production of interleukin 8. The studies suggest that GML is safe for chronic use in monkeys when applied vaginally; it does not alter either mucosal microflora or integrity.

Evaluation of Vaginal Drug Levels and Safety of a Locally Administered Glycerol Monolaurate Cream in Rhesus Macaques.

The human immunodeficiency virus epidemic affects millions of people worldwide. As women are more vulnerable to infection, female-controlled interventions can help control the spread of the disease significantly. Glycerol monolaurate (GML), an inexpensive and safe compound, has been shown to protect against simian immunodeficiency virus infection when applied vaginally. However, on account of its low aqueous solubility, fabrication of high-dose formulations of GML has proven difficult. We describe the development of a vaginal cream that could be loaded with up to 35% GML. Vaginal drug levels and safety of 3 formulations containing increasing concentrations of GML (5%w/w, 15%w/w, and 35%w/w) were tested in rhesus macaques after vaginal administration. GML concentration in the vaginal tissue increased as the drug concentration in the cream increased, with 35% GML cream resulting in tissue concentration of ∼0.5 mg/g, albeit with high interindividual variability. Compared with the vehicle control, none of the GML creams had any significant effect on the vaginal flora and cytokine (macrophage inflammatory protein 3α and interleukin 8) levels, suggesting that high-dose GML formulations do not induce local adverse effects. In summary, we describe the development of a highly loaded vaginal cream of GML, and vaginal drug levels and safety after local administration in macaques.

Glycerol Monolaurate Microbicide Protection against Repeat High-Dose SIV Vaginal Challenge.

Measures to prevent sexual mucosal transmission are critically needed, particularly to prevent transmission to young women at high risk in the microepidemics in South Africa that disproportionally contribute to the continued pandemic. To that end, microbicides containing anti-retroviral (ARV) agents have been shown to prevent transmission, but with efficacy limited both by adherence and pre-existing innate immune and inflammatory conditions in the female reproductive tract (FRT). Glycerol monolaurate (GML) has been proposed as a microbicide component to enhance efficacy by blocking these transmission-facilitating innate immune response to vaginal exposure. We show here in an especially rigorous test of protection in the SIV-rhesus macaque model of HIV-1 transmission to women, that GML used daily and before vaginal challenge protects against repeat high doses of SIV by criteria that include virological and immunological assays to detect occult infection. We also provide evidence for indirect mechanisms of action in GML-mediated protection. Developing a sustained formulation for GML delivery could contribute an independent, complementary protective component to an ARV-containing microbicide.