Thermoreversible gel formulations containing sodium lauryl sulfate or n-Lauroylsarcosine as potential topical microbicides against sexually transmitted diseases

Abstract

The microbicidal efficacies of two anionic surfactants, sodium lauryl sulfate (SLS) and n-lauroylsarcosine (LS), were evaluated in cultured cells and in a murine model of herpes simplex type 2 (HSV-2) intravaginal infection. In vitro studies showed that SLS and LS were potent inhibitors of the infectivity of HSV-2 strain 333. The concentrations of SLS which inhibit viral infectivity by 50% (50% inhibitory dose) and 90% (90% inhibitory dose) were 32.67 and 46.53 microM, respectively, whereas the corresponding values for LS were 141.76 and 225.30 microM. In addition, intravaginal pretreatment of mice with thermoreversible gel formulations containing 2.5% SLS or 2.5% LS prior to the inoculation of HSV-2 strain 333 completely prevented the development of genital herpetic lesions and the lethality associated with infection. Of prime interest, no infectious virus could be detected in mouse vaginal mucosa. Both formulations still provided significant protection when viral challenge was delayed until 1 h after pretreatment. Finally, intravaginal application of gel formulations containing 2.5% SLS or 2.5% LS once daily for 14 days to rabbits did not induce significant irritations to the genital mucosa, as demonstrated from macroscopic and histopathologic examinations. These results suggest that thermoreversible gel formulations containing SLS or LS could represent potent and safe topical microbicides for the prevention of HSV-2 and possibly other sexually transmitted pathogens, including human immunodeficiency virus.

FIG. 1

Infectivity of HSV-2 strain 333 to Vero cells following pretreatment of the virus with different concentrations of SLS (A) or LS (B) for 1 h at 37°C. Results are expressed as a percentage of the value for the control and are the mean ± standard deviation for three independent experiments.

FIG. 2

Time evolutions of the mean lesion score associated with redness (A and D) and swelling (B and E) in the perineal region and of survival rates (C and F) of mice pretreated at 5 min prior to HSV-2 infection with citrate buffer (○), gel alone (17% [wt/wt]) (×), 1% SLS or 1% LS in buffer (●), or gel formulations containing 1% SLS or 1% LS (▵) or 2.5% SLS or 2.5% LS (✴). Untreated infected mice were used as controls (■). (A, B, and C) Data for SLS; (D, E, and F) data for LS. The results are the means for 10 mice per group.

FIG. 3

Viral titers in the genital mucosae of mice pretreated intravaginally with citrate buffer, gel alone (17% [wt/wt]), 2.5% SLS or 2.5% LS in the buffer, or gel containing 2.5% SLS or 2.5% LS and infected 5 min later with HSV-2 strain 333. Untreated infected mice were used as controls. Viral titers are expressed as the log number of PFU per gram of tissue. The results are the means for 10 mice per group. The broken line shows the limit of detection of the assay. The numbers in parentheses represent the numbers of mice without infectious virus in the vaginal mucosa.

FIG. 4

Time evolutions of the mean lesion score associated with redness (A) and swelling (B) and of survival rates (C) of mice infected intravaginally with HSV-2 strain 333 5 min (○), 30 min (✴), 1 h (●), 2 h (□), 4 h (◊), and 6 h (×) after pretreatment with a gel formulation containing 2.5% SLS. Untreated infected mice were used as controls (■). The results are the means for 10 mice per group.

FIG. 5

Vaginal and cervical mucosae of New Zealand rabbits following intravaginal application of buffer (A), gel alone (30% [wt/wt]) (B), 2.5% SLS in buffer (C), or 2.5% SLS incorporated into the gel (D) once daily for 14 days. Photographs are representative of three animals per treatment. C, cervix; V, vagina.

FIG. 6

Vaginal mucosae of New Zealand rabbits following intravaginal application of citrate buffer (A), gel alone (30% [wt/wt]) (B), 2.5% SLS in buffer (C), or 2.5% SLS incorporated into the gel (D) once daily for 14 days Photographs are representative of three regions of the vagina (cervical end, middle, and vulvar end) and three animals per treatment. E, epithelium; SM, submucosa; ➞, epithelial exfoliation; ➤, inflammatory cell infiltrate. Magnification, ×100.