The effect of nonoxynol-9 and chlorhexidine on HIV and sperm in vitro

Metabolic Rewiring of Mycobacterium tuberculosis upon Drug Treatment and Antibiotics Resistance

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), remains a significant global health challenge, further compounded by the issue of antimicrobial resistance (AMR). AMR is a result of several system-level molecular rearrangements enabling bacteria to evolve with better survival capacities: metabolic rewiring is one of them. In this review, we present a detailed analysis of the metabolic rewiring of Mtb in response to anti-TB drugs and elucidate the dynamic mechanisms of bacterial metabolism contributing to drug efficacy and resistance. We have discussed the current state of AMR, its role in the prevalence of the disease, and the limitations of current anti-TB drug regimens. Further, the concept of metabolic rewiring is defined, underscoring its relevance in understanding drug resistance and the biotransformation of drugs by Mtb. The review proceeds to discuss the metabolic adaptations of Mtb to drug treatment, and the pleiotropic effects of anti-TB drugs on Mtb metabolism. Next, the association between metabolic changes and antimycobacterial resistance, including intrinsic and acquired drug resistance, is discussed. The review concludes by summarizing the challenges of anti-TB treatment from a metabolic viewpoint, justifying the need for this discussion in the context of novel drug discovery, repositioning, and repurposing to control AMR in TB.

Biguanides: Species with versatile therapeutic applications

Biguanides are compounds in which two guanidine moieties are fused to form a highly conjugated system. Biguanides are highly basic and hence they are available as salts mostly hydrochloride salts, these cationic species have been found to exhibit many therapeutic properties. This review covers the research and development carried out on biguanides and accounts the various therapeutic applications of drugs containing biguanide group-such as antimalarial, antidiabetic, antiviral, anticancer, antibacterial, antifungal, anti-tubercular, antifilarial, anti-HIV, as well as other biological activities. The aim of this review is to compile all the medicinal chemistry applications of this class of compounds so as to pave way for the accelerated efforts in finding the drug action mechanisms associated with this class of compounds. Importance has been given to the organic chemistry of these biguanide derivatives also.

Multipurpose prevention technologies: biomedical tools to prevent HIV-1, HSV-2, and unintended pregnancies

Statistics clearly show an unmet need for highly effective contraception, especially in less developed countries. Many of these countries are at the core of the HIV/AIDS epidemic and show very high prevalence rates for other sexually transmitted infections (STIs) such as that caused by HSV-2. A woman at risk of unintended pregnancy due to unprotected intercourse is also at risk for HIV/STI. Owing to their causative interrelationship, combining protection against these conditions will result in enhanced prevention and health benefits. Existing multipurpose prevention modalities such as condoms and physical barriers, albeit efficacious, face cultural hurdles that have so far hindered their widespread use. Success has recently been demonstrated in large clinical trials, demonstrating proof of concept of microbicides in reducing the incidence of HIV-1 and HSV-2 among at-risk populations. The challenge heretofore is to refine these products to make them more potent, convenient, accessible, and acceptable. Potent antiviral drugs released topically in the female reproductive tract by innovative delivered systems and formulations will provide safe, effective, and acceptable multipurpose prevention tools. This paper provides an overview of existing and novel approaches to multipurpose prevention strategies.

3-hydroxyphthalic anhydride-modified chicken ovalbumin exhibits potent and broad anti-HIV-1 activity: a potential microbicide for preventing sexual transmission of HIV-1

Heterosexual transmission is the primary route by which women acquire human immunodeficiency virus (HIV)/AIDS. Thus, development of woman-controlled topical microbicides for prevention of sexual transmission of HIV is urgently needed. Here we report that 3-hydroxyphthalic anhydride-modified chicken ovalbumin (HP-OVA) exhibits potent antiviral activity against a broad spectrum of human immunodeficiency virus type 1 (HIV-1) isolates with different genotypes and biotypes. Its antiviral activity is correlated with the percentages of the chemically modified and unmodified lysines and arginines in OVA. HP-OVA inhibits HIV-1 fusion and entry through multiple mechanisms of action, including (i) blocking gp120 binding to CD4 and (ii) interfering with gp41 six-helix bundle formation. Because of the widespread availability and established safety profile of OVA, HP-OVA has good potential to be developed as an effective, safe, and affordable microbicide for prevention of HIV sexual transmission.

Microbicides: a new frontier in HIV prevention

Microbicides are products that can be applied to vaginal or rectal mucosal surfaces with the goal of preventing, or at least significantly reducing, the transmission of sexually transmitted infections (STIs) including HIV-1. Despite more than two decades of HIV-1 vaccine research, there is still no efficacious HIV-1 vaccine, and the scientific community appears skeptical about the short or long-term feasibility of developing a vaccine that has the ability to induce sterilizing immunity against HIV-1. In this setting, microbicide research has gathered momentum. Currently, 16 candidate microbicides are in clinical development and five products are being evaluated in large-scale Phase 2B/3 effectiveness studies. Initial data from these trials will be available within the next 2-3 years, and it is feasible that there could be one or more licensed microbicides by the end of the decade. The first generation of surfactant microbicides had a non-specific mechanism of action. However, subsequent candidate microbicides have been developed to target specific steps in the process of viral transmission. The purpose of this article is to provide an overview of microbicide development and an update on the candidate pipeline.

Polybiguanides, particularly polyethylene hexamethylene biguanide, have activity against human immunodeficiency virus type 1

Polyhexamethylene biguanide (PHMB) is a polybiguanide (PBG) oligomer with antimicrobial activity that is used extensively and safely as a disinfectant. The reported mechanism of PHMB antimicrobial activity, which involves interactions with cell membrane components, suggested that PHMB or other PBG-based compounds might also have antiviral or virucidal activity against the human immunodeficiency virus type 1 (HIV-1). PHMB had modest in vitro activity against both cell-free and cell-associated HIV-1, as well as the ability to interfere with viral binding and entry. However, PHMB was comparable in cytotoxicity to the spermicidal agent nonoxynol-9 (N-9), a compound that has been characterized in previous studies as generally cytotoxic and detrimental to cervicovaginal epithelial integrity. To identify structural variants of PHMB with greater anti-HIV-1 activity and/or less cytotoxicity, modified versions of PHMB incorporating length changes in the hydrocarbon linker units were synthesized and evaluated for in vitro cytotoxicity and inhibition of HIV-1 infectivity. These experiments demonstrated that the PHMB variant polyethylene hexamethylene biguanide (PEHMB) was just as active against HIV-1 as PHMB, yet was much less cytotoxic than either N-9 or PHMB, resulting in an in vitro therapeutic index (TI) approximately 114-fold greater than the TI of N-9. PEHMB, which has been identified in these studies as a promising microbicidal candidate in this family of compounds, will be the focus of further in vitro and in vivo evaluations of anti-HIV-1 activity, toxicity, and mechanisms of action.

In vitro and in vivo: the story of nonoxynol 9

There is an urgent need to expand the range of interventions to prevent HIV transmission and acquisition, especially those that can be controlled by women. Microbicides, defined as antimicrobial products that can be applied topically for the prevention of HIV and other sexually transmitted infections, may offer one of the most promising preventive interventions, because they could be inexpensive, readily available, and widely acceptable. The first microbial product to be clinically evaluated contained Nonoxynol-9 (nonylpenoxypolyethoxyethanol [N-9]), a nonionic surfactant, as the active agent. This article presents a review of the in vitro, ex vivo, and animal model data on the safety of N-9 and a critical analysis of their predictive power based on the results of multiple safety and efficacy trials.

Clinical microbicide research: an overview

At the end of 2003, 42 million people were HIV infected and the epidemic continues to spread, despite the availability and effectiveness of male condoms. For many women negotiating condom use is not feasible. Therefore there is an urgent need for a female controlled method for HIV prevention. This article gives an overview of the clinical research done with microbicides, chemicals with the potential to prevent an HIV infection. In the 1990s most research was done with spermicides, mainly nonoxynol-9. Since the results of the COL-1492 trial became available, new products were evaluated and some of them are now in phase III trials.

The Evaluation of the Local Tolerance of Vaginal Formulations, With or Without Nonoxynol-9, Using the Slug Mucosal Irritation Test

BACKGROUND

Frequent use of some vaginal formulations can induce mucosal irritation. Therefore, it is important to evaluate their vaginal tolerance.

GOAL

The goal of this study was to optimize the mucosal irritation test using slugs for the evaluation of the local tolerance of vaginal gels and investigate the relevance of the test.

STUDY DESIGN

The irritation potential of the gels was assessed by the amount of mucus produced during a repeated 30-minute contact period. Membrane damage was estimated from the release of proteins and enzymes. After optimization of the procedure, the local tolerance of several vaginal gels was evaluated.

RESULTS

Hydroxyethyl cellulose gel induced no irritation, because the mucus production and the protein release were low and no enzyme release was detected. Replens and K-Y jelly resulted in an increased mucus production; however, no increased protein and no enzyme release were detected. The nonoxynol-9-containing gels Protectaid, Advantage S, and Conceptrol caused a higher mucus production and an increased protein release and/or enzyme release, indicating severe irritation.

CONCLUSION

The mucosal irritation test using slugs can be used for local tolerance testing of vaginal formulations.

Tolerance and Safety of Different Concentrations of Chlorhexidine for Peripartum Vaginal and Infant Washes: HIVNET 025

BACKGROUND

There is a continuing need to evaluate sustainable interventions for prevention of mother-to-child transmission (MTCT) of HIV type 1. We evaluated different concentrations (0.25%, 1%, and 2%) of chlorhexidine (CHX) for perinatal maternal and infant washes to identify the maximum tolerable concentration of CHX for such an intervention.

METHODS

Women were enrolled during their third trimester at the maternity unit of the Chris Hani Baragwanath Hospital in Soweto, South Africa, and perinatal maternal and infant washes were completed. Subjective maternal symptoms as well as infant examinations were used to assess tolerability of the washes.

RESULTS

The 0.25% concentration of CHX was well tolerated by the mothers (n = 29). Ten of 79 women (13%) with 1% CHX washes complained of mild vaginal area burning or itching, and washes were stopped in 5 (6%). Twenty-three of 75 women (31%) in the 2% CHX wash group had subjective complaints, and the washes were stopped in 12 (16%). There were no clinical indications of toxicity of the CHX washes among infants.

CONCLUSION

A 1% solution of CHX appears to be a safe and tolerable concentration of CHX for consideration in an MTCT prevention trial.

Synthesis of novel iodinated derivatives of nonoxynol-9 and their bioavailability in rats

The absorption and distribution of iodinated derivatives of nonoxynol-9, after vaginal administration in rats, were compared with results reported for [14C] nonoxynol-9. Mono-iodinated nonoxynol-9 was synthesized in addition to the radiolabeled derivative incorporating iodide-125 ([125I]). Six hours after dosing, test rats were euthanized and selected tissues were excised and assessed for radioactivity. Levels of radioactive markers in the reproductive system were substantial for both [14C] and [125I]. It was concluded that [125I] mono-iodinated nonoxynol-9 and [14C] nonoxynol-9 possessed similar bioavailability.

Transmission of HIV-1 from mother to infant

In the developed world, antiretroviral therapy (ART) administered to the mother during pregnancy and intrapartum and to the infant in the neonatal period has resulted in a reduction of the overall risk of vertical transmission of HIV-1 to approximately 8%. In some settings, ART combined with cesarean section and a reduction in duration of ruptured membranes has resulted in a further lessening of risk to levels < or = 2 percent. A number of less expensive and greatly abbreviated ART regimens, useful for application in resource poor settings, also have resulted in reductions of mother-to-infant transmission of HIV-1 by 33 to 50% compared to baseline. A multitude of studies have shown these drugs to be safe for mothers, fetuses, and newborns. Breastfeeding seems to represent a risk factor that adds to the risk of vertical transmission, especially in infants who are fed a combination of breastmilk and other liquids and solids. Studies designed to assess the possible benefits of treating genital ulcer disease, chorioamnionitis, mastitis, and malnutrition in HIV-infected women, and of applying antiseptic washes to the cervix and vagina during labor, are in progress.

Sodium dodecyl sulfate and C31G as microbicidal alternatives to nonoxynol 9: comparative sensitivity of primary human vaginal keratinocytes

A broad-spectrum vaginal microbicide must be effective against a variety of sexually transmitted disease pathogens and be minimally toxic to the cell types found within the vaginal epithelium, including vaginal keratinocytes. We assessed the sensitivity of primary human vaginal keratinocytes to potential topical vaginal microbicides nonoxynol-9 (N-9), C31G, and sodium dodecyl sulfate (SDS). Direct immunofluorescence and fluorescence-activated cell sorting analyses demonstrated that primary vaginal keratinocytes expressed epithelial cell-specific keratin proteins. Experiments that compared vaginal keratinocyte sensitivity to each agent during a continuous, 48-h exposure demonstrated that primary vaginal keratinocytes were almost five times more sensitive to N-9 than to either C31G or SDS. To evaluate the effect of multiple microbicide exposures on cell viability, primary vaginal keratinocytes were exposed to N-9, C31G, or SDS three times during a 78-h period. In these experiments, cells were considerably more sensitive to C31G than to N-9 or SDS at lower concentrations within the range tested. When agent concentrations were chosen to result in an endpoint of 25% viability after three daily exposures, each exposure decreased cell viability at the same constant rate. When time-dependent sensitivity during a continuous 48-h exposure was examined, exposure to C31G for 18 h resulted in losses in cell viability not caused by either N-9 or SDS until at least 24 to 48 h. Cumulatively, these results reveal important variations in time- and concentration-dependent sensitivity to N-9, C31G, or SDS within populations of primary human vaginal keratinocytes cultured in vitro. These investigations represent initial steps toward both in vitro modeling of the vaginal microenvironment and studies of factors that impact the in vivo efficacy of vaginal topical microbicides.

A phase I study of a novel potential intravaginal microbicide, PRO 2000, in healthy sexually inactive women

BACKGROUND

Although the male condom provides a reliable means of preventing HIV transmission, a broader choice of methods is required particularly in circumstances where the negotiation of condom use is difficult. Development of new products that may be effective as topical vaginal microbicides is the focus of a great deal of research activity currently. The novel agent PRO 2000, a naphthalene sulphonate derivative with in vitro activity against HIV and other sexually transmissible pathogens, is one such compound. We have studied the local and systemic safety and tolerance of a vaginal gel formulation of this agent at two concentrations (0.5% and 4%) over a 2 week period of daily exposure in two cohorts of healthy sexually abstinent women (one in London, UK, and the other in Antwerp, Belgium).

METHODS

This was a randomised, placebo controlled, double blind, three arm clinical trial conducted on two sites. Macroscopic evidence of genital epithelial changes was sought using colposcopy and evidence of microscopic inflammation was acquired using high vaginal biopsy from predetermined sites (UK cohort only). Blood levels of PRO 2000 were measured and laboratory safety tests, including coagulation screens, were performed. The impact on vaginal ecology was also assessed.

RESULTS

73 women were enrolled across both sites (36 UK, 37 Belgium); 24, 24, 25 in the 4%, 0.5%, and placebo groups respectively. Of these, 70 completed 2 weeks' exposure to the study gel. Three (all in the 4% group) withdrew owing to adverse events which were possibly or probably gel related. Cervicovaginal abrasion was seen colposcopically in three subjects after 14 days of gel use (two in the 4% group and one in the placebo group). Genital ulceration was not seen during gel use in any of the subjects who completed the study. Histological evaluation of vaginal biopsy samples (36 women only) showed evidence of increased inflammatory signs in one participant of the 4.0% group. One volunteer in the placebo group had moderate inflammation at screening and at follow up. Severe inflammation was not seen among any of the subjects tested. Plasma levels of PRO 2000 and laboratory safety tests showed no evidence of systemic absorption. No impact was seen on normal vaginal ecology in the UK cohort where samples were taken 12 hours after the last gel application.

CONCLUSION

In this phase I study PRO 2000 gel was found to be generally well tolerated with promising local and systemic safety profiles. The 0.5% gel was better tolerated than the 4% gel as fewer genital epithelial adverse events were seen in the former. Phase II studies are about to begin in sexually active women.

Prevention of mother-to-child transmission of HIV-1

Several recently published randomized trials have demonstrated that a substantial proportion of the mother-to-child transmission of HIV-1 can be prevented by antiretroviral therapy late in gestation and at delivery to mother and infant. The cost implications of these findings are considerable for resource-poor settings. Preliminary data also suggest very low rates of transmission among mothers receiving maximally suppressive combination drug regimens. Prophylactic cesarean delivery has also been shown to reduce transmission in women not receiving antiretroviral agents, and may play a role in selected patients. The avoidance of breast feeding with infant formula supplementation is clearly protective against HIV-1 transmission, but may not improve infant survival in some poorer settings because of associated increases in other infectious diseases and malnutrition.