Improving the clinical relevance of a mouse pregnancy model of antiretroviral toxicity; a pharmacokinetic dosing-optimization study of current HIV antiretroviral regimens

Animal models can be useful tools for the study of HIV antiretroviral (ARV) safety/toxicity in pregnancy and the mechanisms that underlie ARV-associated adverse events. The utility and translatability of animal model-based ARV safety/toxicity data is improved if ARVs are tested in clinically relevant concentrations. The objective of this work was to improve the clinical relevance of our mouse pregnancy model of ARV toxicity, by determining the doses of currently prescribed ARV regimens that would yield human therapeutic plasma concentrations. Pregnant mice were administered increasing doses of ARV combinations by oral gavage, followed by measurement of drug concentrations in the maternal plasma and amniotic fluid. Concentrations of ten different ARVs in maternal plasma and amniotic fluid samples of pregnant mice are presented, with dosing optimization to yield human pregnancy-relevant plasma drug concentrations. We have proposed optimal dosing for different regimen component drugs to achieve human therapeutic plasma levels, so that a clinically relevant standard dosing is established. A review of related ARV pharmacokinetic studies in (pregnant/non-pregnant) rodents and human pregnancy is also shown. We hope these data will inform and encourage the use of mouse pregnancy models in the study of ARV safety/toxicity.

Factors Associated with Lower Respiratory Tract Infections in HIV-Exposed Uninfected Infants

To identify factors that predispose human immunodeficiency virus (HIV)-exposed uninfected infants (HEUs) to higher incidence of severe infections, hospitalization, and death in the first 6-24 months of life compared with HEUs with and without lower respiratory tract infection (LRTI) in the first 6 months of life. Nested case-control study of 107 LRTI+ infants enrolled in the International Site Development Initiative (NISDI) Perinatal and Longitudinal Study in Latin American Countries (LILAC) studies with and 140 LRTI- in the first 6 months, matched by date and place of birth. Infants and mothers had plasma antibodies measured against respiratory syncytial virus (RSV), parainfluenza (PIV) 1, 2, 3, influenza, and pneumococcus 1, 5, 6B, and 14. Compared with LRTI-, mothers of LRTI+ HEUs had lower years of education, lower CD4⁺ cells, and higher HIV plasma viral load at delivery, but similar use of antiretrovirals and cotrimoxazole and other sociodemographic characteristics. LRTI+ and LRTI- HEUs had similar demographic and hematological characteristics and antibody concentrations against respiratory pathogens at birth. At 6 months, the rates of seroconversions to respiratory pathogens and antibody responses to tetanus vaccine were also similar. However, antibody concentrations to RSV were significantly higher in LRTI+ compared with LRTI- HEUs and marginally higher to PIV1. Maternal factors associated with advanced HIV disease, but unrelated to the use of antiretrovirals, cotrimoxazole, or the level of maternal antibodies against respiratory pathogens, contribute to the increased risk of LRTI in HEUs. In HEUs, antiretroviral and cotrimoxazole use, exposure to respiratory pathogens and humoral immune responses were not associated with the incidence of LRTI.

Acute nutritional stress during pregnancy affects placental efficiency, fetal growth and adult glucose homeostasis

Exposure to maternal malnutrition impairs postnatal health. Acute nutritional stress is less clearly implicated in intrauterine programming. We studied the effects of stressing pregnant mothers on perinatal growth and adult glucose homeostasis. We compared one group ("stressed", mothers fasted for 16 hours) with controls ("unstressed"). We found that fasting stress had adverse effects on the weight of the fetuses conceived (p<0.005) and the placental efficiency (p<0.001) in stressed compared to unstressed offspring. Placental weight was increased (p<0.001) presumably in compensation. Stress affected the glucose homeostasis of the offspring when they became adults (p<0.005) when analysed as individuals. We previously linked nutritional stress throughout pregnancy with a mitochondrial stress response. We modelled placenta with cultured human trophoblast cells (BeWos) and fetal tissues with mouse embryonic fibroblasts (MEFs). High throughput imaging showed that the mitochondria of both cell types underwent a similar sequence of changes in morphology, induced by nutritional stresses. The contrasting stress responses on fetal and placental weight were not captured by the cellular models. The stress of maternal fasting may be an important determinant of perinatal outcome in the mouse and might be relevant to nutritional stress in human pregnancy.

Maternal and fetal zidovudine pharmacokinetics during pregnancy and labour: too high dose infused at labour?

AIMS

The main goal of the study was to describe the pharmacokinetics of maternal zidovudine (ZDV) administration during pregnancy and labour and to evaluate their impact on fetal concentrations and exposures.

METHODS

A total of 195 HIV-infected pregnant and non-pregnant women aged 16-59 years were included and 273 maternal and 79 cord blood ZDV concentrations were collected. A population pharmacokinetic model was developed to describe ZDV concentrations as a function of time in the mother and the fetus. Fetal exposures resulting from maternal oral administration and infusion were estimated and compared with therapeutic exposures (3-5 mg l(-1)  h) and to exposure providing higher risk of toxicity (>8.4 mg l(-1)  h). Different protocols for ZDV administration during labour were simulated.

RESULTS

The median fetal exposure and the percentage of children with values above 8.4 mg l(-1)  h were 3.20 mg l(-1)  h and 0% after maternal oral administration, respectively, and 9.71 mg l(-1)  h and 51% after maternal infusion during labour. Two options were considered to reduce fetal exposure during labour: (i) maternal infusion rates could be 1 mg kg(-1)  h(-1) during 1 h followed by 0.5 mg kg(-1)  h(-1) and (ii) the mother could only take oral ZDV every 5 h from start of labour until delivery with her neonate having their first ZDV dose as soon as possible after birth.

CONCLUSIONS

Zidovudine exposures are very important during labour and during the first days of a neonate's life. Maternal ZDV dose should be reduced in addition to the neonate doses reduction already proposed.

Antiretroviral bioanalysis methods of tissues and body biofluids

Research in the many areas of HIV treatment, eradication and prevention has necessitated measurement of antiretroviral (ARV) concentrations in nontraditional specimen types. To determine the knowledgebase of critical details for accurate bioanalysis, a review of the literature was performed and summarized. Bioanalytical assays for 31 ARVs, including metabolites, were identified in 205 publications measuring various tissues and biofluids. 18 and 30% of tissue or biofluid methods, respectively, analyzed more than one specimen type; 35-37% of the tissue or biofluid methods quantitated more than one ARV. 20 and 76% of tissue or biofluid methods, respectively, were used for the analysis of human specimens. HPLC methods with UV detection predominated, but chronologically MS detection began to surpass. 40% of the assays provided complete intra- and inter-assay validation data, but only 9% of publications provided any stability data with even less for the prevalent ARV in treatments.

Coverage of the prevention of mother-to-child transmission program in the Western Cape, South Africa using cord blood surveillance

BACKGROUND

The effectiveness of prevention of mother-to-child transmission of HIV (PMTCT) programs depends on the successful coverage of a series of interventions through pregnancy, intrapartum, and postpartum. Routine monitoring systems based on service data and limited to women on the PMTCT program may overestimate intervention coverage at multiple points along this cascade.

METHODS

Cord blood specimens with individually linked anonymous demographic and pregnancy data were collected from 3 delivery services in the Western Cape Province, South Africa, and screened for HIV. Seropositive specimens were tested for the presence of antiretrovirals. Comparisons were drawn between documented service data and cord blood findings for HIV seroprevalence and antenatal antiretroviral coverage.

RESULTS

A total of 3034 specimens were tested for HIV, 507 (16.7%) of which were HIV seropositive. Of these, 470 (92.7%) were tested for the presence of antiretrovirals, of whom 58.1% had evidence of a standard of care maternal antiretroviral regimen and 73.6% some form of antenatal antiretroviral prophylaxis. Cord blood antiretroviral coverage was lower than that reported by service data. Incomplete antenatal HIV testing accounted for an estimated 46.2% of missed opportunities for transmission reduction.

DISCUSSION

Even in this well-resourced setting, HIV screening and ensuring antenatal compliance with prescribed regimens were the most immediate priorities for reducing vertical transmission. Cord blood surveillance offers a unique opportunity to explore missed opportunities using methods not currently possible from routine antenatal and PMTCT program reporting.

Pharmacokinetics of antiretroviral drugs in anatomical sanctuary sites: the fetal compartment (placenta and amniotic fluid)

HIV resides within anatomical 'sanctuary sites' where local drug exposure and viral dynamics may differ significantly from the systemic compartment. Widespread implementation of antiretroviral therapy has seen a significant decline in the incidence of mother-to-child transmission (MTCT) of HIV. In addition to suppression of maternal plasma/genital viral loads, antiretroviral agents that cross the placenta and achieve adequate concentrations in the fetal compartment may exert a greater prophylactic effect. Penetration of antiretrovirals in the fetal compartment is expressed by accumulation ratios derived from the measurement of drug concentrations in paired maternal plasma and umbilical cord samples. The nucleoside analogues and nevirapine accumulate extensively in cord blood and in the surrounding amniotic fluid, whereas the protease inhibitors (PIs) exhibit low-to-moderate placental accumulation. Early data suggest that high placental/neonatal concentrations are achieved with raltegravir, but to a lesser extent with etravirine and maraviroc (rank order of accumulation: raltegravir/nucleoside reverse transcriptase inhibitor [tenofovir > zidovudine/lamivudine/emtricitabine/stavudine/abacavir] > non-nucleoside reverse transcriptase inhibitor [nevirapine > etravirine] > PI > maraviroc/enfuvirtide). More comprehensive in vivo pharmacokinetic data are required to justify the potential use of these agents as safe and effective options during pregnancy.

Hepatitis B in pregnancy: challenges and treatment

Hepatitis B virus (HBV) during pregnancy presents unique management challenges. Varying aspects of care must be considered, including the effects of HBV on maternal and fetal health, effects of pregnancy on the course of HBV infection, treatment of HBV during and after pregnancy, and prevention of perinatal infection. Antiretroviral therapy has not been associated with increased risk of birth defects or toxicity, but despite studies designed to elucidate the drug efficacy and safety in affected individuals and the developing fetus, recommendations are inconclusive. Clinicians and patients must make individualized decisions after carefully evaluating the risks and benefits summarized in this article.

Prevention of vertical transmission of HIV-1 in resource-limited settings

One of the most exciting areas of HIV research is that of prevention of vertical transmission from mother to child, since it accounts for 90% of childhood HIV infections, and therefore prevention in this context has an enormous potential impact on the spread of HIV among children. Focused research has yielded highly successful strategies for reducing infant infection rates, particularly in the developed world, and much work is underway to implement appropriate strategies in resource-limited settings, although this is not without challenges. Although transmission rates in some settings have been reduced to approximately 1%, scale-up and widespread implementation and application of strategic interventions for prevention of mother-to-child transmission of HIV during pregnancy, delivery and breastfeeding are needed in the developing world.

Nanotechnology-based systems for the treatment and prevention of HIV/AIDS

The HIV/AIDS pandemic is an increasing global burden with devastating health-related and socioeconomic effects. The widespread use of antiretroviral therapy has dramatically improved life quality and expectancy of infected individuals, but limitations of currently available drug regimens and dosage forms, alongside with the extraordinary adapting capacity of the virus, have impaired further success. Alongside, circumventing the escalating number of new infections can only be attained with effective and practical preventative strategies. Recent advances in the field of drug delivery are providing evidence that engineered nanosystems may contribute importantly for the enhancement of current antiretroviral therapy. Additionally, groundwork is also being carried out in the field nanotechnology-based systems for developing preventative solutions for HIV transmission. This manuscript reviews recent advances in the field of nanotechnology-based systems for the treatment and prevention of HIV/AIDS. Particular attention is given to antiretroviral drug targeting to HIV reservoirs and the usefulness of nanosystems for developing topical microbicides and vaccines.