Non-aqueous silicone elastomer gels as a vaginal microbicide delivery system for the HIV-1 entry inhibitor maraviroc

Aqueous semi-solid polymeric gels, such as those based on hydroxyethylcellulose (HEC) and polyacrylic acid (e.g. Carbopol®), have a long history of use in vaginal drug delivery. However, despite their ubiquity, they often provide sub-optimal clinical performance, due to poor mucosal retention and limited solubility for poorly water-soluble actives. These issues are particularly pertinent for vaginal HIV microbicides, since many lead candidates are poorly water-soluble and where a major goal is the development of a coitally independent, once daily gel product. In this study, we report the use of a non-aqueous silicone elastomer gel for vaginal delivery of the HIV-1 entry inhibitor maraviroc. In vitro rheological, syringeability and retention studies demonstrated enhanced performance for silicone gels compared with a conventional aqueous HEC gel, while testing of the gels in the slug model confirmed a lack of mucosal irritancy. Pharmacokinetic studies following single dose vaginal administration of a maraviroc silicone gel in rhesus macaques showed higher and sustained MVC levels in vaginal fluid, vaginal tissue and plasma compared with a HEC gel containing the same maraviroc loading. The results demonstrate that non-aqueous silicone gels have potential as a formulation platform for coitally independent vaginal HIV microbicides.

Postcesarean pelvic floor dysfunction contributes to undisclosed psychosocial morbidity

OBJECTIVE: To estimate the prevalence and severity of postcesarean pelvic dysfunction. STUDY DESIGN: Using biopsychosocial interviewing at home, 184 postcesarean primiparas were compared to 100 vaginally delivered women regarding symptoms of stress incontinence, anal incontinence and dyspareunia. Delivery details were confirmed from medical records. RESULTS: Comparison of postcesarean vs. vaginally delivered women revealed stress incontinence in 33% vs. 54% and dyspareunia in 27% vs. 46%, both differences reaching statistical significance, unlike anal incontinence, which was manifest in 51% vs. 44%. When compared to emergency cesarean the relative risk of stress incontinence following an elective cesarean was 0.99 (0.71, 1.39), of dyspareunia 1.02 and of anal incontinence 1.05, indicating no statistically significant difference. Thirty (22%) stress incontinent and 4 (3%) fecally incontinent mothers used pads continuously, suggesting severe physical morbidity. Severe dysphoria (depression) was expressed by 41 (35%) stress incontinent mothers, 38 (30%) with dyspareunia and 34 (26%) with anal incontinence; the association of severe dysphoria with dyspareunia was statistically significant (OR = 2.504 [1.362, 4.602]). Few women came forward to seek help. CONCLUSION: Pelvic dysfunction was similar after elective or emergency cesarean. Compared to vaginal delivery, postcesarean stress incontinence and dyspareunia were less frequent but biopsychosocial morbidity could be severe.

Characterisation of protein stability in rod-insert vaginal rings

A major goal in vaccine development is elimination of the 'cold chain', the transport and storage system for maintenance and distribution of the vaccine product. This is particularly pertinent to liquid formulation of vaccines. We have previously described the rod-insert vaginal ring (RiR) device, comprising an elastomeric body into which are inserted lyophilised, rod-shaped, solid drug dosage forms, and having potential for sustained mucosal delivery of biomacromolecules, such as HIV envelope protein-based vaccine candidates. Given the solid, lyophilised nature of these insert dosage forms, we hypothesised that antigen stability may be significantly increased compared with more conventional solubilised vaginal gel format. In this study, we prepared and tested vaginal ring devices fitted with lyophilised rod inserts containing the model antigen bovine serum albumin (BSA). Both the RiRs and the gels that were freeze-dried to prepare the inserts were evaluated for BSA stability using PAGE, turbidimetry, microbial load, MALDI-TOF and qualitative precipitate solubility measurements. When stored at 4°C, but not when stored at 40°C/75% RH, the RiR formulation offered protection against structural and conformational changes to BSA. The insert also retained matrix integrity and release characteristics. The results demonstrate that lypophilised gels can provide relative protection against degradation at lower temperatures compared to semi-solid gels. The major mechanism of degradation at 40°C/75% RH was shown to be protein aggregation. Finally, in a preliminary study, we found that addition of trehalose to the formulation significantly reduces the rate of BSA degradation compared to the original formulation when stored at 40°C/75% RH. Establishing the mechanism of degradation, and finding that degradation is decelerated in the presence of trehalose, will help inform further development of RiRs specifically and polymer based freeze-dried systems in general.

Influence of microbial antigen formulation and delivery route on the immune response

Recent technological advances have resulted in the production of safe subunit and synthetic small peptide vaccines. Unfortunately, these vaccines are weakly or non-immunogenic in the absence of an immunological adjuvant (agents that can induce strong immunity to antigens). In addition, in order to prevent and/or control infection at the mucosal surface, stimulation of the mucosal immune system is essential. This may be achieved via the common mucosal immune system by exposure to antigen at a mucosal surface remote from the area of infection. Initial studies investigated the potential of multiple emulsions in effecting oral absorption and the subsequent immune responses to a lipopolysaccharide vaccine (LPS) after immunisation. Nasal delivery of LPS was carried out in parallel work using either aqueous solution or gel formulations. Tetanus toxoid vaccine in simple solution was delivered to guinea pigs as free antigen or entrapped in DSPC liposomes. In addition, adsorbed tetanus toxoid vaccine was delivered nasally free or in an aerosil gel formulation. This work was extended to investigate guinea pigs immunised by various mucosal routes with a herpes simplex virus subunit vaccine prepared from virus infected cells and delivered in gels, multiple emulsions and liposomes. Comparable serum antibody responses resulted but failed to produce enhanced protection against vaginal challenge when compared to subcutaneous immunisation with alhydrogel adjuvanted vaccine. Thus, immunisation of the mucosal surface by these methods may have been inadequate. These studies were extended in an attempt to protect against HSV genital challenge by construction of an attenuated Salmonella typhimurium HWSH aroA mutant expressing a cloned glycoprotein D-l gene fused to the Es-cherichia coli lac z promoter. Preliminary work on the colonisation of guinea pigs with S. typhimurium HWSH aroA mutants were carried out, with the aim of using the guinea pig HSV vaginal model to investigate protection.