Animal models of anti-HIV drugs exposure during pregnancy: effects on neurobehavioral development

Reproductive health decision-making in perinatally HIV-infected adolescents and young adults

With widespread access to antiretroviral therapy in the United States, many perinatally HIV-infected (PHIV+) children are surviving into adolescence and adulthood, becoming sexually active and making decisions about their reproductive health. The literature focusing on the reproductive decisions of individuals behaviorally infected with HIV can serve as a springboard for understanding the decision-making process of PHIV+ youth. Yet, there are many differences that critically distinguish reproductive health and related decision-making of PHIV+ youth. Given the potential public health implications of their reproductive decisions, better understanding of factors influencing the decision-making process is needed to help inform the development of salient treatment and prevention interventions. To begin addressing this understudied area, a "think tank" session, comprised of clinicians, medical providers, and researchers with expertise in the area of adolescent HIV, was held in Bethesda, MD, on September 21, 2011. The focus was to explore what is known about factors that influence the reproductive decision-making of PHIV+ adolescents and young adults, determine what important data are needed in order to develop appropriate intervention for PHIV+ youth having children, and to recommend future directions for the field in terms of designing and carrying out collaborative studies. In this report, we summarize the findings from this meeting. The paper is organized around the key themes that emerged, including utilizing a developmental perspective to create an operational definition of reproductive decision-making, integration of psychosocial services with medical management, and how to design future research studies. Case examples are presented and model program components proposed.

HIV treatment and associated mitochondrial pathology: review of 25 years of in vitro, animal, and human studies

Antiretroviral therapy has dramatically reduced mortality in human immunodeficiency virus (HIV) infection. In 1988, the suggestion that the first antiretroviral drug, zidovudine, was the potential cause of muscle pathology in HIV-infected persons resulted in structural and biochemical patient studies demonstrating acquired mitochondrial dysfunction. Assessment of subsequent nucleoside analog reverse transcriptase inhibitor (NRTI) antiretroviral drugs has indicated that mitochondria are a common target of NRTI toxicity in multiple tissues, leading to a wide variety of pathology ranging from lipodystrophy to neuropathy. Overwhelmingly, these complications have emerged during post-licensing human studies. Subsequent animal and in vitro studies have then elucidated the potential pathological mechanisms, suggesting that NRTI-associated mitochondrial toxicity arises principally from inhibition of the sole mitochondrial DNA (mtDNA) polymerase gamma, leading to a reduction in mtDNA content (depletion). Millions of patients have been treated with mitochondrially toxic NRTIs and these drugs remain the backbone of antiretroviral rollout in much of sub-Saharan Africa. Here we describe the 25-year history of antiretroviral associated mitochondrial pathology and critically review the strength of evidence linking clinical, histopathological, and molecular data. We discuss recently described novel mechanisms of NRTI-associated mitochondrial damage and whether or not recently licensed NRTIs may be considered free from mitochondrial toxicity.

Safety of perinatal exposure to antiretroviral medications: developmental outcomes in infants

BACKGROUND

This study evaluated effects of perinatal exposure to antiretroviral (ARV) medications on neurodevelopment of HIV-exposed, uninfected infants.

METHODS

HIV-exposed, uninfected infants (age 9-15 months) enrolled in Surveillance Monitoring for Antiretroviral Therapy Toxicities, a multisite prospective surveillance study, completed the Bayley Scales of Infant and Toddler Development-Third Edition (Bayley-III), assessing cognition, language, motor skills, social-emotional development and adaptive behavior. Linear regression models were used to evaluate associations between Bayley-III outcomes in infants with and without perinatal and neonatal ARV exposure, by regimen (combination ARV [cARV] versus non-cARV), type of regimen (defined by drug class) and individual ARVs (for infants with cARV exposure), adjusting for maternal and infant health and demographic covariates.

RESULTS

As of May 2010, 374 infants had valid Bayley-III evaluations. Median age at testing was 12.7 months; 49% male, 79% black and 16% Hispanic. Seventy-nine percent were exposed to regimens containing protease inhibitors (9% of protease inhibitor-containing regimens also included non-nucleoside reverse transcriptase inhibitors), 5% to regimens containing non-nucleoside reverse transcriptase inhibitors (without protease inhibitor) and 14% to regimens containing only nucleoside reverse transcriptase inhibitors. Overall, 83% were exposed to cARV. No Bayley-III outcome was significantly associated with overall exposure to cARV, ARV regimen or neonatal prophylaxis. For individual ARVs, following sensitivity analyses, the adjusted group mean on the Language domain was within age expectations but significantly lower for infants with perinatal exposure to atazanavir (P = 0.01).

CONCLUSIONS

These results support the safety of perinatal ARV use. Continued monitoring for adverse neurodevelopmental outcomes in older children is warranted, and the safety of atazanavir merits further study.

Oral uridine supplementation antagonizes the peripheral neuropathy and encephalopathy induced by antiretroviral nucleoside analogues

OBJECTIVE

Peripheral neuropathy and central nervous system neurodegeneration may result from the mitochondrial toxicity of some antiretroviral nucleoside analogues. We investigated whether this neuropathology may be antagonized by uridine supplementation in vivo.

DESIGN

Because of the obvious difficulties in obtaining human neural tissues, the mitochondrial neurotoxicity of the nucleoside analogues was studied in mice.

METHODS

BALB/C mice (7 weeks of age) were fed for 9 weeks with zalcitabine (13 mg/kg per day) or zidovudine (100 mg/kg per day) with or without mitocnol (340 mg/kg per day), a dietary supplement with high uridine bioavailability. Hippocampal and sciatic nerve mitochondria were analyzed.

RESULTS

Zalcitabine and to a lesser extent zidovudine induced a significant peripheral neuropathy and encephalopathy with disrupted mitochondrial ultrastructure, depleted mitochondrial DNA, reduced levels of cytochrome c oxidase activity and diminished expression of mitochondrial DNA-encoded cytochrome c oxidase subunit I. Mitocnol had no intrinsic effects but attenuated or fully normalized all measured disorder of the peripheral and central nervous system.

CONCLUSION

Zidovudine and zalcitabine induce a mitochondrial disorder in the peripheral and central nervous system, both of which are antagonized by uridine supplementation.

The use of second-generation antipsychotics and the changes in physical growth in children and adolescents with perinatally acquired HIV

Second-generation antipsychotics (SGAs) are increasingly prescribed to treat psychiatric symptoms in pediatric patients infected with HIV. We examined the relationship between prescribed SGAs and physical growth in a cohort of youth with perinatally acquired HIV-1 infection. Pediatric AIDS Clinical Trials Group (PACTG), Protocol 219C (P219C), a multicenter, longitudinal observational study of children and adolescents perinatally exposed to HIV, was conducted from September 2000 until May 2007. The analysis included P219C participants who were perinatally HIV-infected, 3-18 years old, prescribed first SGA for at least 1 month, and had available baseline data prior to starting first SGA. Each participant prescribed an SGA was matched (based on gender, age, Tanner stage, baseline body mass index [BMI] z score) with 1-3 controls without antipsychotic prescriptions. The main outcomes were short-term (approximately 6 months) and long-term (approximately 2 years) changes in BMI z scores from baseline. There were 236 participants in the short-term and 198 in the long-term analysis. In linear regression models, youth with SGA prescriptions had increased BMI z scores relative to youth without antipsychotic prescriptions, for all SGAs (short-term increase = 0.192, p = 0.003; long-term increase = 0.350, p < 0.001), and for risperidone alone (short-term = 0.239, p = 0.002; long-term = 0.360, p = 0.001). Participants receiving both protease inhibitors (PIs) and SGAs showed especially large increases. These findings suggest that growth should be carefully monitored in youth with perinatally acquired HIV who are prescribed SGAs. Future research should investigate the interaction between PIs and SGAs in children and adolescents with perinatally acquired HIV infection.

Mitochondrial disorders among infants exposed to HIV and antiretroviral therapy

Although antiretroviral therapy (ART) is critical for preventing mother-to-child transmission of HIV, concern has been raised about the possibility that it may cause mitochondrial dysfunction in infants. There is adequate evidence for a mechanism by which exposure to nucleoside reverse transcriptase inhibitors (NRTIs) could lead to mitochondrial dysfunction; animal studies have shown evidence of mitochondrial dysfunction in the offspring of animals treated with NRTIs and mitochondrial disorders occur in adults treated with NRTIs. This systematic review synthesises the published research on mitochondrial dysfunction and disorders in infants exposed to HIV and antiretrovirals. We found conflicting evidence regarding the possible association of in utero ART exposure with mortality and morbidity due to mitochondrial dysfunction. ART exposure in utero or postpartum was associated with persistent decreases in lymphocytes, neutrophils and platelets as well as an increased risk of transient lactic acidaemia, anaemia and mitochondrial DNA depletion, although these laboratory findings were generally not associated with clinical symptoms. We conclude that large, prospective studies of HIV-exposed infants are needed to resolve the discrepant results regarding morbidity and mortality related to mitochondrial disorders, to ascertain the clinical significance of effects on laboratory values, to determine whether or not the incidence of mitochondrial disorders differs by regimen and to develop predictive models that might identify which infants are at the greatest risk. The challenges that remain to be addressed include the development of a sensitive but affordable screening algorithm in combination with specific diagnostic criteria; consistent collection of data on ART exposure and other risk factors, long-term follow-up of HIV-exposed but uninfected children and implementation in resource-limited settings.

Perinatal AZT exposure alters the acoustic and tactile startle response to 8-OH-DPAT and apomorphine in adult rats

The present study was designed to assess the dopaminergic and serotonergic contributions of the acoustic startle response (ASR) and the tactile startle response (TSR) in adult rats that had been perinatally exposed to AZT (azidothymidine, zidovudine; an antiretroviral agent). Each dam was randomly assigned to a treatment group: non-treated, AZT0, 100 or 150 mg/kg. Once daily gastric intubation began prenatally on gestational day (G) 19 and continued to G22 and then the pups were intubated between postnatal day (PND) 2-20. On PND60, animals were tested for responses to both acoustic and tactile stimuli following a challenge of vehicle, 0.25 or 0.5 mg/kg 8-OH-DPAT, a 5-HT(1A) agonist, or 0.75 or 2.0 mg/kg apomorphine (APO, a dopaminergic agonist) IP. Both DPAT and APO increased startle magnitude as expected. Additionally, perinatal AZT exposure enhanced startle responses following both DPAT and APO, an effect not due to perinatal handling or intubation. Similarly, perinatal AZT increased tactile responses following drug challenge in a gender-specific manner. Perinatal AZT also prolonged startle latencies, a change which may indicate that perinatal AZT alters conduction velocity. Therefore, the administration of AZT during the perinatal period results in long-term functional alterations within the startle reflex pathways.

Polybrominated diphenyl ethers: neurobehavioral effects following developmental exposure

Polybrominated diphenyl ethers (PBDEs), a class of widely used flame retardants, are becoming widespread environmental pollutants, as indicated by studies on sentinel animal species, as well as humans. Of particular concern are the reported increasingly high levels of PBDEs in human milk, as should be given that almost no information is available on their potential effects on developing organisms. In order to address this issue, studies have been conducted in mice and rats to assess the potential neurotoxic effects of perinatal exposure to PBDEs (congeners 47, 99, 153 and the penta-BDE mixture DE-71). Characteristic endpoints of PBDE neurotoxicity are, among others, endocrine disruption (e.g. decreased thyroid hormone levels), alteration in cholinergic system activity (behavioral hyporesponsivity to nicotine challenge), as well as alterations of several behavioral parameters. In particular, the main hallmark of PBDE neurotoxicity is a marked hyperactivity at adulthood. Furthermore, a deficit in learning and memory processes has been found at adulthood in neonatally exposed animals. Some of neurotoxic effects of PBDEs are comparable to those of polychlorinated biphenyls (PCBs), though the latter class of compounds seems to exert a stronger toxic effect. Available information on PBDE neurotoxicity obtained from animal studies and the possibility of neonatal exposure to PBDEs via the mother's milk suggest that these compounds may represent a potential risk for neurobehavioral development in humans.