Perinatal genotoxicity and carcinogenicity of anti-retroviral nucleoside analog drugs

Comparison of the Effects of Three Dual-Nucleos(t)ide Reverse Transcriptase Inhibitor Backbones on Placenta Mitochondria Toxicity and Oxidative Stress Using a Mouse Pregnancy Model

Nucleos(t)ide reverse transcriptase inhibitors (NRTIs) are the backbone of HIV antiretroviral therapy (ART). ART use in pregnancy has been associated with adverse birth outcomes, in part due to NRTI-induced mitochondrial toxicity. Direct comparison on the effects of commonly used dual-NRTI regimens on placental mitochondria toxicity in pregnancy is lacking. We compared zidovudine/lamivudine, abacavir/lamivudine, and tenofovir/emtricitabine using a mouse model and examined markers of placental mitochondrial function and oxidative stress. Zidovudine/lamivudine and abacavir/lamivudine were associated with lower fetal and placental weights compared to controls, whereas tenofovir/emtricitabine was associated with the least fetal and placental weight reduction, as well as lower resorption rates. Placental mitochondrial DNA content, as well as placental expression of cytochrome c-oxidase subunit-II, DNA polymerase gamma, and citrate synthase, was higher in tenofovir/emtricitabine-treated mice compared to other groups. Zidovudine/lamivudine-treated mice had elevated malondialdehyde levels (oxidative stress marker) compared to other groups and lower mRNA levels of manganese superoxide dismutase and peroxisome proliferator-activated receptor gamma coactivator 1-alpha in the placenta compared to tenofovir/emtricitabine-treated mice. We observed differences in effects between NRTI regimens on placental mitochondrial function and birth outcomes. Tenofovir/emtricitabine was associated with larger fetuses, increased mtDNA content, and higher expression of mitochondrial-specific antioxidant enzymes and mitochondrial biogenesis enzymes, whereas zidovudine/lamivudine was associated with markers of placental oxidative stress.

No Difference in Growth Outcomes up to 24 Months of Age by Duration of Exposure to Maternal Antiretroviral Therapy Among Children Who Are HIV-Exposed and Uninfected in Malawi

BACKGROUND

With the implementation of lifelong antiretroviral therapy (ART) for HIV treatment and prevention, the proportion of children exposed to ART in utero from conception is increasing. We estimated the effect of timing of ART exposure on growth of children HIV-exposed and uninfected (CHEU) up to Up to 24 months of age in Malawi.

METHODS

Data were collected from a prospective cohort of infants HIV-exposed aged 1-6 months (enrollment) and their mothers with HIV enrolled in the National Evaluation of Malawi's Prevention of Mother-to-Child Transmission of HIV Programme (2014-2018). Anthropometry was measured at enrollment, visit 1 (approximately 12 months), and visit 2 (approximately 24 months). Weight-for-age (WAZ) and length-for-age (LAZ) were calculated using the WHO Growth Standards. Multivariable mixed-effects models with linear splines for age were used to examine differences in growth by timing of ART exposure (from conception, first/second trimester, or third trimester/postpartum). Models were adjusted for confounders selected a priori guided by a conceptual framework. Hypothesized interactions and potential mediators were explored, and interactions with splines were included in final models if P < 0.1.

RESULTS

A total of 1,206 singleton CHEU and their mothers were enrolled and 563 completed the follow-up through 24 months of age. Moreover, 48% of CHEU were exposed to ART from conception, 40% from first/second trimester, and 12% from third trimester/postpartum. At enrollment, 12% of infants had low birthweight (LBW), 98% had been breastfed in past 7 days, and 57% were enrolled in an HIV care clinic. CHEU growth trajectories demonstrated cohort-wide growth faltering after the age of 12 months. Of 788 and 780 CHEU contributing to WAZ and LAZ multivariable models, respectively, there was no evidence of differences in mean WAZ or LAZ among those exposed from conception or first/second trimester vs. third trimester/postpartum and no evidence of a difference in WAZ or LAZ rate of change by timing of ART exposure (all interactions P > 1.0).

CONCLUSION

Reassuringly, ART exposure from conception was not associated with decreased WAZ or LAZ in CHEU Up 24 months of age. Overall growth trajectories suggest CHEU experience growth faltering after 12 months of age and may need support through and beyond the first 2 years of life.

Human genetic risk of treatment with antiviral nucleoside analog drugs that induce lethal mutagenesis: The special case of molnupiravir

This review considers antiviral nucleoside analog drugs, including ribavirin, favipiravir, and molnupiravir, which induce genome error catastrophe in SARS-CoV or SARS-CoV-2 via lethal mutagenesis as a mode of action. In vitro data indicate that molnupiravir may be 100 times more potent as an antiviral agent than ribavirin or favipiravir. Molnupiravir has recently demonstrated efficacy in a phase 3 clinical trial. Because of its anticipated global use, its relative potency, and the reported in vitro "host" cell mutagenicity of its active principle, β-d-N4-hydroxycytidine, we have reviewed the development of molnupiravir and its genotoxicity safety evaluation, as well as the genotoxicity profiles of three congeners, that is, ribavirin, favipiravir, and 5-(2-chloroethyl)-2'-deoxyuridine. We consider the potential genetic risks of molnupiravir on the basis of all available information and focus on the need for additional human genotoxicity data and follow-up in patients treated with molnupiravir and similar drugs. Such human data are especially relevant for antiviral NAs that have the potential of permanently modifying the genomes of treated patients and/or causing human teratogenicity or embryotoxicity. We conclude that the results of preclinical genotoxicity studies and phase 1 human clinical safety, tolerability, and pharmacokinetics are critical components of drug safety assessments and sentinels of unanticipated adverse health effects. We provide our rationale for performing more thorough genotoxicity testing prior to and within phase 1 clinical trials, including human PIG-A and error corrected next generation sequencing (duplex sequencing) studies in DNA and mitochondrial DNA of patients treated with antiviral NAs that induce genome error catastrophe via lethal mutagenesis.

In-utero exposure to zidovudine-containing antiretroviral therapy and clonal hematopoiesis in HIV-exposed uninfected newborns

OBJECTIVE

Zidovudine (ZDV) has been extensively used in pregnant women to prevent vertical transmission of HIV but few studies have evaluated potential mutagenic effects of ZDV during fetal development.

DESIGN

Our study investigated clonal hematopoiesis in HIV-exposed uninfected (HEU) newborns, 94 of whom were ZDV-exposed and 91 antiretroviral therapy (ART)-unexposed and matched for potential confounding factors.

METHODS

Utilizing high depth sequencing and genotyping arrays, we comprehensively examined blood samples collected during the first week after birth for potential clonal hematopoiesis associated with fetal ZDV exposure, including clonal single nucleotide variants (SNVs), small insertions and deletions (indels), and large structural copy number or copy neutral alterations.

RESULTS

We observed no statistically significant difference in the number of SNVs and indels per person in ZDV-exposed children (adjusted ratio [95% confidence interval, CI] for expected number of mutations = 0.79 [0.50--1.22], P = 0.3), and no difference in the number of large structural alterations. Mutations in common clonal hematopoiesis driver genes were not found in the study population. Mutational signature analyses on SNVs detected no novel signatures unique to the ZDV-exposed children and the mutational profiles were similar between the two groups.

CONCLUSION

Our results suggest that clonal hematopoiesis at levels detectable in our study is not strongly influenced by in-utero ZDV exposure; however, additional follow-up studies are needed to further evaluate the safety and potential long-term impacts of in-utero ZDV exposure in HEU children as well as better investigate genomic aberrations occurring late in pregnancy.

Nevirapine Pharmacokinetics in Neonates Between 25 and 32 Weeks Gestational Age for the Prevention of Mother-to-Child Transmission of HIV

Eleven newborns from 25 to 32 weeks of gestational age, weighting from 0.66 to 1.60 kg received 2 mg/kg doses of nevirapine syrup. In 15 samples, collected 8.75-89 hours after drug intake, concentrations ranged from 0.65 to 16.68 mg/L. Three nevirapine dose of 2 mg/kg at day 0, 2 and 6 days of life achieved nevirapine concentrations above the proposed nevirapine target for HIV prophylaxis for at least 11 days.

In utero exposure to protease inhibitor-based antiretroviral regimens delays growth and developmental milestones in mice

Antiretroviral therapy (ART) in pregnancy has dramatically reduced HIV vertical transmission rates. Consequently, there is a growing number of children that are HIV exposed uninfected (CHEUs). Studies suggest that CHEUs exposed in utero to ART may experience developmental delays compared to their peers. We investigated the effects of in utero ART exposure on perinatal neurodevelopment in mice, through assessment of developmental milestones. Developmental milestone tests (parallel to reflex testing in human infants) are reflective of brain maturity and useful in predicting later behavioral outcomes. We hypothesized that ART in pregnancy alters the in utero environment and thereby alters developmental milestone outcomes in pups. Throughout pregnancy, dams were treated with boosted-atazanavir combined with either abacavir/lamivudine (ATV/r/ABC/3TC), or tenofovir/emtricitabine (ATV/r/TDF/FTC), or water as control. Pups were assessed daily for general somatic growth and on a battery of tests for primitive reflexes including surface-righting, negative-geotaxis, cliff-aversion, rooting, ear-twitch, auditory-reflex, forelimb-grasp, air-righting, behaviors in the neonatal open field, and olfactory test. In utero exposure to either ART regimen delayed somatic growth in offspring and evoked significant delays in the development of negative geotaxis, cliff-aversion, and ear-twitch reflexes. Exposure to ATV/r/ABC/3TC was also associated with olfactory deficits in male and forelimb grasp deficits in female pups. To explore whether delays persisted into adulthood we assessed performance in the open field test. We observed no significant differences between treatment arm for males. In females, ATV/r/TDF/FTC exposure was associated with lower total distance travelled and less ambulatory time in the centre, while ATV/r/ABC/3TC exposure was associated with higher resting times compared to controls. In utero PI-based ART exposure delays the appearance of primitive reflexes that involve vestibular and sensory-motor pathways in a mouse model. Our findings suggest that ART could be disrupting the normal progress/maturation of the underlying neurocircuits and encourage further investigation for underlying mechanisms.

Serum Vitamin D is Differentially Associated with Socioemotional Adjustment in Early School-Aged Ugandan Children According to Perinatal HIV Status and In Utero/Peripartum Antiretroviral Exposure History

An impact of vitamin D in neurocognitive function has been theorized but it remains unknown whether vitamin-D insufficiency (VDI) is associated with worse socio-emotional adjustment (SEA) in vulnerable early school-aged children. This study examines the thesis that deficits in SEA are related to VDI using longitudinal data from 254 children that are perinatally HIV-infected (PHIV), exposed-uninfected (HEU), or unexposed-uninfected (HUU). In utero/peripartum antiretroviral (IPA) exposure was established per medical record documentation of biological mother’s ART regimen in pregnancy. Four caregiver-reported age- and sex-standardized measures of SEA were obtained at months 0, 6, and 12 for dependent children aged 6–10 years: externalizing problems (EPC), internalizing problems (IPC), behavioral symptoms index (BSI), and adaptive skills index (ASI). VDI was highly prevalent (74%, n = 188), and its association with change in SEA measures over 12 months varied by HIV-status (VDI*HIV, all p-values < 0.03). There was further variation in relationship of vitamin-D to SEA by IPA among PHIV (for ASI, BSI, and EPC, vitamin-D*IPA, p-value ≤ 0.01) and HEU (for BSI and EPC, vitamin-D*IPA, p-value ≤ 0.04). Among HUU, BSI (β = −0.32, 95% CI: −0.50, −0.13), IPC (β = −0.28, 95% CI: −0.47, −0.09), and EPC (β = −0.20, 95% CI: −0.37, −0.02) all declined moderately per quartile increment in VD. Among PHIV, on the one hand higher vitamin D predicted ASI gains (moderate vs. low VD, β = 0.52, p = 0.002), but this protective association was absent for BSI, EPC, and IPC (β = 0.36–0.77, p < 0.05). In absence of IPA-exposure, increasing vitamin-D predicted declines in BSI and EPC (moderate vs. low Vitamin D, β = −0.56 to −0.71, p ≤ 0.02) among HEU. However, given IPA exposure among HEU, higher VDI predicted moderate elevation in BSI (β = 0.39, 95% CI: 0.00, 0.78) and IPC (β = 0.48, 95% CI: 0.05, 0.92). Interaction between VD and IPA exposure for SEA outcomes among HEU and PHIV children warrants further investigation. The vitamin-D associated SEA improvement among HUU and HEU without IPA exposure suggests vitamin-D supplementation may remediate behavioral and adaptive deficits in this groups.

Dynamics of leukocyte telomere length in pregnant women living with HIV, and HIV-negative pregnant women: A longitudinal observational study

Background

HIV-mediated inflammation and immune activation can accelerate telomere attrition. In addition, antiretrovirals can inhibit telomerase, possibly shortening telomeres. We examined the longitudinal dynamics of leukocyte telomere length (LTL) during pregnancy in a unique cohort of women living with HIV (WLWH) treated with combination antiretroviral therapy (cART), and HIV-negative control women.

Methods

Blood was collected at three visits during pregnancy, at 13–23, >23–30, and >30–40 weeks of gestation, and for WLWH only, at 6 weeks post-partum. LTL was measured by qPCR and both cross-sectional and longitudinal (MANOVA) models were used to examine possible predictors of LTL among participants who attended all three visits during pregnancy.

Results

Among WLWH (n = 64) and HIV-negative women (n = 41), within participant LTL were correlated throughout pregnancy (p<0.001). LTL was shorter among WLWH at first visit, but this difference waned by the second visit. WLWH who discontinued cART post-partum experienced a decrease in LTL. Longitudinally, LTL was similar in both groups and increased as gestation progressed, a change that was more pronounced among women under 35 years. Among WLWH, both smoking throughout pregnancy (p = 0.04) and receiving a ritonavir-boosted protease inhibitor-based regimen (p = 0.03) were independently associated with shorter LTL.

Conclusions

LTL increases as pregnancy progresses; the reasons for this are unknown but may relate to changes in blood volume, hormones, and/or cell subset distribution. While our observations need confirmation in an independent cohort, our data suggest that although some cART regimens may influence LTL, being on cART appears overall protective and that stopping cART post-partum may negatively impact LTL. The effect of smoking on LTL is clearly negative, stressing the importance of smoking cessation.

The Base Pairing Partner Modulates Alkylguanine Alkyltransferase

O⁶-Alkylguanine DNA adducts are repaired by the suicide enzyme alkylguanine alkyltransferase (AGT). AGT facilitates repair by binding DNA in the minor groove, flipping out the damaged base, and transferring the O⁶-alkyl group to a cysteine residue in the enzyme's active site. Despite there being significant knowledge concerning the mechanism of AGT repair, there is limited insight regarding how altered interactions of the adduct with its complementary base in the DNA duplex influence its recognition and repair. In this study, the relationship of base pairing interactions and repair by human AGT (hAGT) was tested in the frequently mutated codon 12 of the KRAS gene with complementary sequences containing each canonical DNA base. The rate of O⁶-MeG repair decreased 2-fold when O⁶-MeG was paired with G, whereas all other canonical bases had no impact on the repair rate. We used a combination of biochemical studies, molecular modeling, and artificial nucleobases to elucidate the mechanism accounting for the 2-fold decrease. Our results suggest that the reduced rate of repair is due to O⁶-MeG adopting a syn conformation about the glycosidic bond precluding the formation of a repair-active complex. These data provide a novel chemical basis for how direct reversion repair may be impeded through modification of the base pair partner and support the use of artificial nucleobases as tools to probe the biochemistry of damage repair processes.

Paediatric HIV-1 infection: updated strategies of prevention mother-to-child transmission

INTRODUCTION

HIV-1 epidemiology is changing and prevention of mother-to-child transmission (PMTCT) strategies have been continuously optimized over time. However, the correct management of infected women during pregnancy is crucial for PMTCT and cases of vertical transmission continue to occur.

OBJECTIVE

To review the most recent evidence regarding the prevention of MTCT in resource-rich and resource-limited settings, focalizing on new possible approaches.

RESULTS

New issues regard the optimal antiretroviral therapy regimen for pregnant women with good immunological control, the use of intrapartum zidovudine (ZDV) in pregnant women with low viral load, the optimization of prophylaxis in the settings where breastfeeding is recommended and use of combined neonatal prophylaxis (CNP) in infants at high-risk for MTCT. Complete viral control, in recent years, has been achieved in most infected pregnant women, has led to change the recommended mode of delivery, since vaginal birth has become a safe option and is now largely recommended. Recent data reported a large use of CNP in preterm infants: this practice may be dangerous, due to the lack of safety data, and its efficacy and effectiveness is unproven.

CONCLUSION

Data are accumulating on efficacy, effectiveness and safety of different PMTCT strategies in various possible clinical scenarios, however further researches are needed in order to optimize the management of infants at extremely low risk for MTCT as well as in those presenting with high risk for infection.

Evaluation of motor and cognitive development among infants exposed to HIV

This study of a prospective and cross-sectional nature compared the motor and cognitive development of HIV-exposed and unexposed infants in their first 18months of age. 40 infants exposed to HIV and antiretroviral therapy (Experimental Group - EG) and 40 unexposed infants (Control Group - CG) participated in the study. They were divided into four age groups of 4, 8, 12 and 18months old, with 10 infants from EG and 10 from CG in each group. The infants were evaluated once on motor and cognitive development by the Bayley Scale of Infant and Toddler Development. Performance category grading and comparisons among scaled score, composite score and percentile rank were held. There was significant group effect for scores in motor and cognitive domains showing lower scores for EG regardless of age. In comparison to the CG, the EG presented lower scores for cognitive domain at 8 and 18months. In the performance categories, all infants were classified at or above the average for motor and cognitive development, except of one EG-18month old infant classified as borderline for motor development. Infants exposed to HIV and antiretroviral therapy own adequate cognitive and motor development in the first 18months. However, the lower scores found, particularly on the 8th and 18th month for cognitive development, may indicate future problems, highlighting the need for systematic follow-up of this population.

Evaluation of the PIGRET assay in rats by single oral dosing with azidothymidine

In vivo phosphatidylinositol glycan, class A (Pig-a) gene mutation assay using peripheral blood is known to be a novel and useful tool to evaluate the mutagenicity of compounds. Recently, the rat PIGRET assay which is an improved method for measuring Pig-a mutant cells in reticulocytes with magnetic enrichment of CD71 positive cells has been developed. Several reports showed that the PIGRET assay could detect the increase of Pig-a mutant frequency earlier than the Pig-a assay in total red blood cells (RBC Pig-a assay). Therefore, as part of a collaborative study by the Mammalian Mutagenicity Study (MMS) Group of the Japanese Environmental Mutagen Society, the usefulness of the PIGRET assay in comparison to the RBC Pig-a assay has been assessed for 24 compounds with various mechanisms of action. In the present study, we performed the PIGRET assay and RBC Pig-a assay with a nucleoside analogue, azidothymidine (AZT), and compared the results in these assays. We administered a single dose of AZT to rats by oral gavage up to 2000mg/kg and examined Pig-a mutant frequencies at days 7, 14 and 28 by PIGRET and RBC Pig-a assays. No significant increases in mutant frequency were observed after administration of AZT in both the RBC Pig-a and PIGRET assays and comparable to the previous results of the International Workshop on Genotoxicity Testing (IWGT) workgroup. AZT has been thought to induce not only DNA chain termination as a pharmacological effect but also a large deletion on the genome DNA. The Pig-a assays may be less sensitive to compounds such as AZT which induce large deletions on the genome DNA.

Mitochondrial compromise in 3-year old patas monkeys exposed in utero to human-equivalent antiretroviral therapies

Antiretroviral (ARV) drug therapy, given during pregnancy for prevention of mother-to-child transmission of human immunodeficiency virus 1 (HIV-1), induces fetal mitochondrial dysfunction in some children. However, the persistence/reversibility of that dysfunction is unclear. Here we have followed Erythrocebus patas (patas) monkey offspring for up to 3 years of age (similar in development to a 15-year old human) after exposure of the dams to human-equivalent in utero ARV exposure protocols. Pregnant patas dams (3-5/exposure group) were given ARV drug combinations that included zidovudine (AZT)/lamivudine (3TC)/abacavir (ABC), or AZT/3TC/nevirapine (NVP), for the last 10 weeks (50%) of gestation. Infants kept for 1 and 3 years also received drug for the first 6 weeks of life. In offpsring at birth, 1 and 3 years of age mitochondrial morphology, examined by electron microscopy (EM), was compromised compared to the unexposed controls. Mitochondrial DNA (mtDNA), measured by hybrid capture chemiluminescence assay (HCCA) was depleted in hearts of patas exposed to AZT/3TC/NVP at all ages (P < 0.05), but not in those exposed to AZT/3TC/ABC at any age. Compared to unexposed controls, mitochondrial reserve capacity oxygen consumption rate (OCR by Seahorse) in cultured bone marrow mesenchymal fibroblasts from 3-year-old patas offspring was ∼50% reduced in AZT/3TC/ABC-exposed patas (P < 0.01), but not in AZT/3TC/NVP-exposed patas. Overall the data show that 3-year-old patas sustain persistent mitochondrial dysfunction as a result of perinatal ARV drug exposure. Environ. Mol. Mutagen. 57:526-534, 2016. © 2016 Wiley Periodicals, Inc.

The PHACS SMARTT Study: Assessment of the Safety of In Utero Exposure to Antiretroviral Drugs

The Surveillance Monitoring for ART Toxicities (SMARTT) cohort of the Pediatric HIV/AIDS Cohort Study includes over 3,500 HIV-exposed but uninfected infants and children at 22 sites in the US, including Puerto Rico. The goal of the study is to determine the safety of in utero exposure to antiretrovirals (ARVs) and to estimate the incidence of adverse events. Domains being assessed include metabolic, growth and development, cardiac, neurological, neurodevelopmental (ND), behavior, language, and hearing. SMARTT employs an innovative trigger-based design as an efficient means to identify and evaluate adverse events. Participants who met a predefined clinical or laboratory threshold (trigger) undergo additional evaluations to define their case status. After adjusting for birth cohort and other factors, there was no significant increase in the likelihood of meeting overall case status (case in any domain) with exposure to combination ARVs (cARVs), any ARV class, or any specific ARV. However, several individual ARVs were significantly associated with case status in individual domains, including zidovudine for a metabolic case, first trimester stavudine for a language case, and didanosine plus stavudine for a ND case. We found an increased rate of preterm birth with first trimester exposure to protease inhibitor-based cARV. Although there was no overall increase in congenital anomalies with first trimester cARV, a significant increase was seen with exposure to atazanavir, ritonavir, and didanosine plus stavudine. Tenofovir exposure was associated with significantly lower mean whole-body bone mineral content in the newborn period and a lower length and head circumference at 1 year of age. With ND testing at 1 year of age, specific ARVs (atazanavir, ritonavir-boosted lopinavir, nelfinavir, and tenofovir) were associated with lower performance, although all groups were within the normal range. No ARVs or classes were associated with lower performance between 5 and 13 years of age. Atazanavir and saquinavir exposure were associated with late language emergence at 1 year, but not at 2 years of age. The results of the SMARTT study are generally reassuring, with little evidence for serious adverse events resulting from in utero ARV exposure. However, several findings of concern warrant further evaluation, and new ARVs used in pregnancy need to be evaluated.

Lung Malignancies in HIV Infection

Pulmonary malignancies are a major source of morbidity and mortality in HIV-infected persons. Non-AIDS-defining lung cancers (mostly non-small cell lung cancers) are now a leading cause of cancer death among HIV-infected persons. HIV-associated factors appear to affect the risk of lung cancer and may adversely impact cancer treatment and outcomes. HIV infection also may modify the potential harms and benefits of lung cancer screening with computed tomography. AIDS-defining lung malignancies include pulmonary Kaposi sarcoma and pulmonary lymphoma, both of which are less prevalent with widespread adoption of antiretroviral therapy.

Strategies for the prevention of mother to child transmission in Western countries: an update

BACKGROUND

During the last decades remarkable scientific advances have been made toward the prevention of HIV mother-to-child transmission, in particular in developed nations. The aim of this review was to analyze the latest findings and available international recommendations on the prevention of HIV mother-to-child transmission in high-income countries.

METHODS

We performed a literature search of the Cochrane Library, MEDLINE by PubMed and EMBASE from database inception through June 2014, using the following terms: HIV, mother-to-child transmission and mother-to-child-transmission prevention. All types of articles in the English language were included. US and available European guidelines were searched and included in the analysis.

RESULTS

One hundred fifty articles were selected for inclusion in this review.

CONCLUSIONS

Global epidemiology of HIV infection is rapidly evolving, in particular in high-resource countries. The interpretation of clinical and epidemiological studies is crucial for the development of evidence-based recommendations to guide the management of HIV mother-to-child transmission. Although significant progress has been made, heterogeneity between countries in specific interventions still exists, which may address future research.

Fetal consequences of maternal antiretroviral nucleoside reverse transcriptase inhibitor use in human and nonhuman primate pregnancy

PURPOSE OF REVIEW

Here we present fetal genotoxicity and mitochondrial toxicity, induced by nucleoside reverse transcriptase inhibitors (NRTIs), in HIV-1-infected pregnant women treated to prevent mother-to-child HIV-1 transmission, and in virus-free pregnant patas monkeys.

RECENT FINDINGS

In the offspring of pregnant patas monkeys given human-equivalent NRTI protocols, aneuploidy was found in cultured bone marrow cells taken at birth, 1, and 3 years of age. In some newborn human infants, the offspring of HIV-1-infected mothers given zidovudine (AZT) therapy, aneuploidy, mitochondrial DNA (mtDNA) depletion, morphologically damaged mitochondria, and reduction in cardiac left ventricular muscle were observed. NRTI-exposed human and patas umbilical cords had similar levels of mtDNA depletion and mitochondrial morphological damage. NRTI-exposed patas offspring showed a compensatory increase in heart mtDNA, and a 50% loss of brain mtDNA at 1 year of age. Mitochondrial morphological damage and mtDNA loss were persistent in blood cells of NRTI-exposed infants up to 2 years of age, and in heart and brain from NRTI-exposed patas up to 3 years of age (human equivalent of 15 years).

SUMMARY

Whereas use of NRTIs in human pregnancy protects many thousands of children worldwide, some HIV-1-uninfected infants born to HIV-1-infected mothers receiving antiretroviral drug therapy sustain toxicities that may have adverse consequences later in life.

Role of nucleotide excision repair and p53 in zidovudine (AZT)-induced centrosomal deregulation

The nucleoside reverse transcriptase inhibitor zidovudine (AZT) induces genotoxic damage that includes centrosomal amplification (CA > 2 centrosomes/cell) and micronucleus (MN) formation. Here we explored these end points in mice deficient in DNA repair and tumor suppressor function to evaluate their effect on AZT-induced DNA damage. We used mesenchymal-derived fibroblasts cultured from C57BL/6J mice that were null and wild type (WT) for Xpa, and WT, haploinsufficient and null for p53 (6 different genotypes). Dose-responses for CA formation, in cells exposed to 0, 10, and 100 μM AZT for 24 hr, were observed in all genotypes except the Xpa((+/+)) p53((+/-)) cells, which had very low levels of CA, and the Xpa((-/-)) p53((-/-)) cells, which had very high levels of CA. For CA there was a significant three-way interaction between Xpa, p53, and AZT concentration, and Xpa((-/-)) cells had significantly higher levels of CA than Xpa((+/+)) cells, only for p53((+/-)) cells. In contrast, the MN and MN + chromosomes (MN + C) data showed a lack of AZT dose response. The Xpa((-/-)) cells, with p53((+/+)) or ((+/-)) genotypes, had levels of MN and MN + C higher than the corresponding Xpa((+/+)) cells. The data show that CA is a major event induced by exposure to AZT in these cells, and that there is a complicated relationship between AZT and CA formation with respect to gene dosage of Xpa and p53. The loss of both genes resulted in high levels of damage, and p53 haploinsufficicency strongly protected Xpa((+/+)) cells from AZT-induced CA damage.

Safety of in utero and neonatal antiretroviral exposure: cognitive and academic outcomes in HIV-exposed, uninfected children 5-13 years of age

BACKGROUND

Long-term effects of in utero and neonatal antiretroviral (ARV) exposure on cognitive and academic development in HIV-exposed, uninfected school-age children are unknown.

METHODS

HIV-exposed, uninfected children, ages 5-13 years, in Pediatric HIV/AIDS Cohort Study Surveillance Monitoring for Antiretroviral Treatment Toxicities, a US-based multisite cohort study, completed age-appropriate Wechsler intelligence and academic scales (WPPSI-III, WASI, WIAT-II-A). Associations between cognitive and academic outcomes and in utero ARV exposure by regimen, class and individual ARVs were evaluated, adjusting for potential confounders.

RESULTS

Children completing WPPSI-IIIs (n = 350) were 49% male, 74% Black, 25% Hispanic; WASI (n = 337) and WIAT-II-A (n = 415) cohorts were similar. The percentage exposed to combination ARV (cARV) was 84% (WPPSI-III), 64% (WASI) and 67% (WIAT-II-A). Among ARV-exposed children, there were no significant associations between any ARV regimen or class and any cognitive or academic outcome. In addition, in both unadjusted models and after adjustment for caregiver IQ, sociodemographic factors and maternal health and substance use during pregnancy, no individual ARV drug was associated with significantly lower cognitive or academic scores. Factors typically associated with lower cognitive and academic scores in the general population, such as prematurity, small for gestational age, maternal alcohol use and lower maternal cognitive status, were also associated with lower scores in this study.

CONCLUSIONS

Overall, the safety of prenatal and neonatal ARV use was supported.

Selective protection of zidovudine-induced DNA-damage by the antioxidants WR-1065 and tempol

The cytokinesis-block micronucleus cytome (CBMN) assay, introduced by Fenech, was used to demonstrate different types of DNA damage in MOLT-3 human lymphoblastoid cells exposed to 10 μM zidovudine (AZT). In addition, we explored the cytoprotective potential of two antioxidants, WR-1065 and Tempol, to decrease AZT-induced genotoxicity. Binucleated cells, arrested by Cytochalasin B (Cyt B), were evaluated for micronuclei (MN), caused by DNA damage or chromosomal loss, and chromatin nucleoplasmic bridges (NPBs), caused by telomere attrition. Additionally, nuclear buds (NBUDs), caused by amplified DNA, and apoptotic and necrotic (A/N) cells were scored. We hypothesized that AZT exposure would increase the frequency of genotoxic end points, and that the antioxidants Tempol and WR-1065 would protect against AZT-induced genotoxicity. MOLT-3 cells were exposed to 0 or 10 µM AZT for a total of 76 hr. After the first 24 hr, 0 or 5 µM WR-1065 and/or 0 or 200 µM Tempol were added for the remainder of the experiment. For the last 28 hr (of 76 hr), Cyt B was added to arrest replication after one cell division, leaving a predominance of binucleated cells. The nuclear division index (NDI) was similar for all treatment groups, indicating that the exposures did not alter cell viability. MOLT-3 cells exposed to AZT alone had significant (P < 0.05) increases in MN and NBs, compared to unexposed cells. Both Tempol and WR-1065 protected against AZT-induced MN formation (P < 0.003 for both), and WR-1065, but not Tempol, reduced the levels of A/N (P = 0.041). In cells exposed to AZT/Tempol there were significantly reduced levels of NBUDs, compared to cells exposed to AZT alone (P = 0.015). Cells exposed to AZT/WR-1065 showed reduced levels of NPBs, compared to cells exposed to AZT alone (P = 0.037). Thus WR-1065 and Tempol protected MOLT-3 cells against specific types of AZT-induced DNA damage.

Perinatally acquired HIV infection: long-term neuropsychological consequences and challenges ahead

Over the past three decades, perinatal HIV infection in the United States has evolved from a fatal disease to a manageable chronic illness. As the majority of youth with perinatal HIV infection age into adolescence and adulthood, management of this stigmatizing, transmittable disease in the backdrop of a cadre of environmental stressors presents challenges beyond those of other chronic illnesses. The neurologic and neuropsychological consequences of this neurotropic virus have important implications for the successful navigation of responsibilities related to increasingly independent living of this aging population. This article will review the neurologic and neuropsychological consequences of perinatal HIV infection and concomitant factors in the era of highly active antiretroviral therapy and will provide an overview of the neuropathology, pathogenesis, neuroimaging findings, and treatment of perinatal HIV infection, as well as recommendations for service provision and future research.

Nutritional status and metabolic disorders in HIV-exposed uninfected prepubertal children

OBJECTIVE

The objective of the study was to assess the nutritional status and metabolic alterations in HIV-exposed uninfected (HIVe) children compared with HIV-unexposed (HIVn) children.

METHODS

A cross-sectional study was carried out with 76 children distributed into two groups: HIVe (n = 31) and HIVn (n = 45). Biochemical data (hematologic test, lipid profile, insulin resistance, hepatic profile, and C-reactive protein) were evaluated. Anthropometric parameters and body composition analyses were performed.

RESULTS

The groups were similar regarding body mass index-for-age z-scores (P = 0.297) and height-for-age z-scores (P = 0.666). HIVe had a higher dyslipidemia prevalence (38.7% versus 11.1%; P = 0.010), altered total cholesterol (TC) values (19.4% versus 2.2%; P = 0.016) higher LDL-C mean levels (97.8 mg/dl versus 86 mg/dl; P = 0.028), borderline low-density lipoprotein cholesterol (LDL-C) (40% versus 14%; P = 0.011) and TC (41.9% versus 20%; P = 0.038) compared with HIVn.

CONCLUSION

Despite the similar nutritional status between groups, our data clearly demonstrated a higher prevalence of dyslipidemia, altered TC, higher LDL-C levels and also LDL-C and TC borderline values in HIVe children.

Short communication: The relationship between mitochondrial dysfunction and insulin resistance in HIV-infected children receiving antiretroviral therapy

Mitochondrial abnormalities may lead to metabolic complications in HIV-infected children who have been receiving long-term antiretroviral treatment. We conducted a matched, case-control study comparing 21 HIV-infected children with insulin resistance (cases) to 21 HIV-infected children without insulin resistance (controls) to assess differences in mitochondrial DNA (mtDNA) copies/cell and oxidative phosphorylation NADH dehydrogenase (C1) and cytochrome c oxidase (C4) enzyme activities in peripheral blood mononuclear cells. MtDNA copies/cell tended to be lower in cases, and fasting serum glucose levels were inversely and significantly correlated with C1 enzyme activity, more so in cases. Larger pediatric studies should evaluate mitochondrial etiologies of insulin resistance and determine the role of antiretroviral therapies or HIV infection on mitochondrial dysfunction.

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.

The stress response resolution assay. I. Quantitative assessment of environmental agent/condition effects on cellular stress resolution outcomes in epithelium

The events or factors that lead from normal cell function to conditions and diseases such as aging or cancer reflect complex interactions between cells and their environment. Cellular stress responses, a group of processes involved in homeostasis and adaptation to environmental change, contribute to cell survival under stress and can be resolved with damage avoidance or damage tolerance outcomes. To investigate the impact of environmental agents/conditions upon cellular stress response outcomes in epithelium, a novel quantitative assay, the "stress response resolution" (SRR) assay, was developed. The SRR assay consists of pretreatment with a test agent or vehicle followed later by a calibrated stress conditions exposure step (here, using 6-thioguanine). Pilot studies conducted with a spontaneously-immortalized murine mammary epithelial cell line pretreated with vehicle or 20 µg N-ethyl-N-nitrososurea/ml medium for 1 hr, or two hTERT-immortalized human bronchial epithelial cell lines pretreated with vehicle or 100 µM zidovudine/lamivudine for 12 days, found minimal alterations in cell morphology, survival, or cell function through 2 weeks post-exposure. However, when these pretreatments were followed 2 weeks later by exposure to calibrated stress conditions of limited duration (for 4 days), significant alterations in stress resolution were observed in pretreated cells compared with vehicle-treated control cells, with decreased damage avoidance survival outcomes in all cell lines and increased damage tolerance outcomes in two of three cell lines. These pilot study results suggest that sub-cytotoxic pretreatments with chemical mutagens have long-term adverse impact upon the ability of cells to resolve subsequent exposure to environmental stressors.

Perinatal exposure of patas monkeys to antiretroviral nucleoside reverse-transcriptase inhibitors induces genotoxicity persistent for up to 3 years of age

BACKGROUND

Erythrocebus patas (patas) monkeys were used to model antiretroviral (ARV) drug in human immunodeficiency virus type 1-infected pregnant women.

METHODS

Pregnant patas dams were given human-equivalent doses of ARVs daily during 50% of gestation. Mesenchymal cells, cultured from bone marrow of patas offspring obtained at birth and at 1 and 3 years of age, were examined for genotoxicity, including centrosomal amplification, micronuclei, and micronuclei containing whole chromosomes.

RESULTS

Compared with controls, statistically significant increases (P < .05) in centrosomal amplification, micronuclei, and micronuclei containing whole chromosomes were found in mesenchymal cells from most groups of offspring at the 3 time points.

CONCLUSIONS

Transplacental nucleoside reverse-transcriptase inhibitor exposures induced fetal genotoxicity that was persistent for 3 years.

Safety of tenofovir use during pregnancy: early growth outcomes in HIV-exposed uninfected infants

OBJECTIVE

To evaluate the association of tenofovir disoproxil fumarate (TDF) use during pregnancy with early growth parameters in HIV-exposed, uninfected (HEU) infants.

DESIGN

US-based prospective cohort study of HEU children to examine potential adverse effects of prenatal TDF exposure.

METHODS

We evaluated the association of maternal TDF use during pregnancy with small for gestational age (SGA); low birth weight (LBW, <2.5 kg); weight-for-age z-scores (WAZ), length-for-age z-scores (LAZ), and head circumference-for-age (HCAZ) z-scores at newborn visit; and LAZ, HCAZ, and WAZ at age 1 year. Logistic regression models for LBW and SGA were fit, adjusting for maternal and sociodemographic factors. Adjusted linear regression models were used to evaluate LAZ, WAZ, and HCAZ by TDF exposure.

RESULTS

Of 2029 enrolled children with maternal antiretroviral information, TDF was used by 449 (21%) HIV-infected mothers, increasing from 14% in 2003 to 43% in 2010. There was no difference between those exposed to combination regimens with vs. without TDF for SGA, LBW, and newborn LAZ and HCAZ. However, at age 1 year, infants exposed to combination regimens with TDF had significantly lower adjusted mean LAZ and HCAZ than those without TDF (LAZ: -0.17 vs. -0.03, P=0.04; HCAZ: 0.17 vs. 0.42, P=0.02).

CONCLUSION

TDF use during pregnancy was not associated with increased risk for LBW or SGA. The slightly lower mean LAZ and HCAZ observed at age 1 year in TDF-exposed infants are of uncertain significance but underscore the need for additional studies of growth outcomes after TDF use during pregnancy.

Transplacental carcinogenesis with dibenzo[def,p]chrysene (DBC): timing of maternal exposures determines target tissue response in offspring

Dibenzo[def,p]chrysene (DBC) is a transplacental carcinogen in mice (15mg/kg; gestation day (GD) 17). To mimic residual exposure throughout pregnancy, dams received four smaller doses of DBC (3.75mg/kg) on GD 5, 9, 13 and 17. This regimen alleviated the previously established carcinogenic responses in the thymus, lung, and liver. However, there was a marked increase in ovarian tumors (females) and hyperplastic testes (males). [(14)C]-DBC (GD 17) dosing revealed transplacental distribution to fetal tissues at 10-fold lower concentrations than in paired maternal tissue and residual [(14)C] 3weeks post-dose. This study highlights the importance of developmental stage in susceptibility to environmental carcinogens.

Effects of in utero antiretroviral exposure on mitochondrial DNA levels, mitochondrial function and oxidative stress

OBJECTIVES

HIV and antiretroviral (ART) exposure in utero may have deleterious effects on the infant, but uncertainty still exists. The objective of this study was to evaluate aspects of mitochondrial DNA (mtDNA) content, mitochondrial function and oxidative stress simultaneously in placenta, umbilical cord blood and infant blood in HIV/ART-exposed infants compared with uninfected controls.

METHODS

HIV-1-infected pregnant women and HIV-1-uninfected healthy pregnant controls were enrolled in the study prospectively. Placenta and umbilical cord blood were obtained at delivery and infant blood was obtained within 48 h of delivery. mtDNA content was determined for each specimen. Nuclear [subunit IV of cytochrome c-oxidase (COX IV)]- and mitochondrial (COX II)-encoded polypeptides of the oxidative phosphorylation enzyme cytochrome c-oxidase were quantified in cord and infant blood. Placental mitochondria malondialdehyde (MDA) concentrations were measured as a marker of oxidative stress.

RESULTS

Twenty HIV-positive/HIV-exposed and 26 control mother-infant pairs were enrolled in the study. All HIV-infected women and their infants received ART. Placental MDA concentration and mtDNA content in placenta and cord blood were similar between groups. The cord blood COX II:IV ratio was lower in the HIV-positive group than in the controls, whereas the infant peripheral blood mtDNA content was higher in the HIV-exposed infants, but the infant peripheral blood COX II:IV ratio was similar. No infant had clinical evidence of mitochondrial disease or acquired HIV infection. In multivariable regression analyses, the significant findings in cord and infant blood were both most associated with HIV/ART exposure.

CONCLUSIONS

HIV-exposed infants showed reduced umbilical cord blood mitochondrial enzyme expression with increased infant peripheral blood mitochondrial DNA levels, the latter possibly reflecting a compensatory mechanism to overcome HIV/ART-associated mitochondrial toxicity.

Antiretroviral drugs for preventing mother-to-child transmission of HIV: a review of potential effects on HIV-exposed but uninfected children

The provision of antiretroviral drugs for the prevention of mother-to-child HIV transmission has been rising sharply in low- and middle-income countries. Changes to the World Health Organization guidelines support further extension of these programs. The result will be a greatly expanded population of HIV-exposed but uninfected children with substantial exposure to antiretroviral drugs, both in utero and while breastfeeding. There are limited data on possible toxicities in this burgeoning population, and the large number of confounding factors limits any conclusions. Although the evidence on birth defects and mitochondrial toxicity remains equivocal, considerable data link protease inhibitors to preterm delivery and low birth-weight. Transient hematologic toxicities are also likely. The drug impact later in life is an open question. Larger and longer cohort studies are necessary to properly balance the risks and benefits of large-scale infant exposure to antiretroviral agents.

The genetic toxicity effects of lamivudine and stavudine antiretroviral agents

IMPORTANCE OF THE FIELD

The nucleoside reverse transcriptase inhibitors (NRTIs) are used in antiretroviral therapy worldwide for the treatment of HIV infections. These drugs act by blocking reverse transcriptase enzyme activity, causing pro-viral DNA chain termination. As a consequence, NRTIs could cause genomic instability and loss of heterozygosity.

AREAS COVERED IN THIS REVIEW

This review highlights the toxic and genotoxic effects of NRTIs, particularly lamivudine (3TC) and stavudine (d4T) analogues. In addition, a battery of short-term in vitro and in vivo systems are described to explain the potential genotoxic effects of these NRTIs as a single drug or a complexity of highly active antiretroviral therapy.

WHAT THE READER WILL GAIN

The readers will gain an understanding of a secondary effect that could be induced by 3TC and d4T treatments.

TAKE HOME MESSAGE

Considering that AIDS has become a chronic disease, more comprehensive toxic genetic studies are needed, with particular attention to the genetic alterations induced by NRTIs. These alterations play a primary role in carcinogenesis and are also involved in secondary and subsequent steps of carcinogenesis.

Progressive mitochondrial compromise in brains and livers of primates exposed in utero to nucleoside reverse transcriptase inhibitors (NRTIs)

Mitochondrial compromise has been documented in infants born to women infected with the human immunodeficiency virus (HIV-1) who received nucleoside reverse transcriptase inhibitor (NRTI) therapy during pregnancy. To model these human exposures, we examined mitochondrial integrity at birth and 1 year in brain cortex and liver from offspring of retroviral-free Erythrocebus patas dams-administered human-equivalent NRTI doses for the last half (10 weeks) of gestation. Additional infants, followed for 1 year, were given the same drugs as their mothers for the first 6 weeks of life. Exposures included: no drug, Zidovudine (AZT), Lamivudine (3TC), AZT/3TC, AZT/Didanosine (ddI), and Stavudine (d4T)/3TC. In brain and liver, oxidative phosphorylation (OXPHOS) enzyme activities (complexes I, II, and IV) showed minimal differences between unexposed and NRTI-exposed offspring at both times. Brain and liver mitochondria from most NRTI-exposed patas, both at birth and 1 year of age, contained significant (p < 0.05) morphological damage observed by electron microscopy (EM), based on scoring of coded photomicrographs. Brain and liver mitochondrial DNA (mtDNA) levels in NRTI-exposed patas were depleted significantly in the 3TC and d4T/3TC groups at birth and were depleted significantly (p < 0.05) at 1 year in all NRTI-exposed groups. In 1-year-old infants exposed in utero to NRTIs, mtDNA depletion was 28.8-51.8% in brain and 37.4-56.5% in liver. These investigations suggest that some NRTI-exposed human infants may sustain similar mitochondrial compromise in brain and liver and should be followed long term for cognitive integrity and liver function.

Inhibition of NF-κB activation sensitizes U937 cells to 3'-azido-3'-deoxythymidine induced apoptosis

In this study, we investigated molecular mechanisms underlying low susceptibility to apoptosis induced by the nucleoside analog azidothymidine (AZT) and the role of nuclear factor-κB (NF-κB) activation in these phenomena. A preliminary screening in different cell lines indicated U937 monocytic cell line as suitable to this purpose. Treatment of U937 cells even with suprapharmacological concentrations of AZT induced only moderate levels of apoptosis. Surprisingly, SuperArray analysis showed that AZT induced the transcriptional activity of both pro- and anti-apoptotic genes. Interestingly, moreover, several genes upregulated by AZT were NF-κB related. In fact, AZT, after an initial inhibition of NF-κB activation with respect to control, induced a transient, but consistent, increase in NF-κB-binding activity. Inhibition of NF-κB activation in U937 cells, stably transfected with a dominant-negative IκBα or by pharmacological treatment, sensitized them to apoptosis induced by AZT and impaired the upregulation of anti-apoptotic genes in response to AZT treatment, with respect to control cells. These results indicate that NF-κB activation by AZT has a role in protecting target cells from apoptotic cell death, improving our understanding of the toxicology and the therapeutic usage of this drug.

Modifying a displacement pump for oral gavage dosing of solution and suspension preparations to adult and neonatal mice

To assess a drug's toxic or carcinogenic effects on neonatal and adult mice and rats, researchers often carry out oral gavage studies. Whether dosed singly or in various combinations, provided as soluble solutions or as colloidal suspensions, the drug must be delivered in accurate and precise doses. For studies that require newborn mice to receive multiple daily doses, delicately handling neonates to increase their chances of surviving is just as critical as the ability to accurately dose small volumes. To help ensure accurate and precise delivery of drug doses ranging from 5 microl for neonatal mice to 400 microl for adults, the authors adapted an automated pipetting system. By slightly modifying standard gavage needles, the authors delivered, on average, 98-99% of targeted dose volumes to neonatal mice.

In utero exposure of female CD-1 Mice to AZT and/or 3TC: I. Persistence of microscopic lesions in cardiac tissue

The current study was designed to delineate temporal changes in cardiomyocytes and mitochondria at the light and electron microscopic levels in hearts of mice exposed transplacentally to commonly used nucleoside analogs (NRTIs). Pregnant CD-1 mice were given 80 mg AZT/kg, 40 mg 3TC/kg, 80 mg AZT/kg plus 40 mg 3TC/kg, or vehicle alone during the last 7 days of gestation, and hearts from female mouse pups were examined at 13 and 26 weeks postpartum for histopathological or ultrastructural changes in cross-sections of both the ventricles and the interventricular septum. Using light microscopy and special staining techniques, transplacental exposure to AZT, 3TC, or AZT/3TC was shown to induce significant histopathological changes in myofibrils; these changes were more widespread at 13 weeks than at 26 weeks postpartum. While most light microscopic lesions resolved, some became more severe between 13 and 26 weeks postpartum. Transplacental NRTI exposure also resulted in progressive drug-specific changes in the number and ultrastructural integrity of cardiac mitochondria. These light and electron microscopic findings show that a subset of changes in cardiac mitochondria and myofibrils persisted and progressed months after transplacental exposure of an animal model to NRTIs, with combined AZT/3TC exposure yielding additive effects compared with either drug alone.

A review of nucleoside reverse transcriptase inhibitor use to prevent perinatal transmission of HIV

Worldwide, women comprise > 50% of all people living with HIV and the vast majority of these women are of childbearing age. In fact, a significant proportion of these women are identified as HIV-infected during pregnancy. Preventing perinatal transmission has been one of the greatest prevention successes of the HIV epidemic with < 2% of live births resulting in an HIV-infected infant. The strategic use of combination antiretroviral therapy has been a critical component of this reduction. With more antiretroviral agents available for HIV, the appropriate selection of therapy is often based on provider familiarity with the various agents. Although benefits of antiretroviral use in pregnancy tremendously outweigh the risks, concerns regarding short- and long-term toxicity in mothers and their children, in addition to the risk of the development of HIV resistance, remain subjects of discussion. The choice of antiretroviral 'backbone' is supported by extensive data showing efficacy in the prevention of HIV vertical transmission. Co-formulated zidovudine/lamivudine is the most commonly used combination in pregnancy. Long-term consequences of in utero exposure to antiretroviral agents are not fully understood. In this article, we review the data regarding nucleoside reverse transcriptase inhibitors with a focus on tenofovir.

Neurodevelopment and in utero antiretroviral exposure of HIV-exposed uninfected infants

OBJECTIVE

Antiretroviral (ARV) drugs are routinely provided to HIV-infected pregnant women to prevent HIV mother-to-child transmission. Although ARV use has significantly reduced mother-to-child transmission to <2% in the United States, it remains crucial to monitor uninfected infants and children for adverse consequences of in utero ARV exposure.

METHODS

We studied neurodevelopmental function in HIV-exposed uninfected children who were enrolled in Pediatric AIDS Clinical Trials Group 219/219C, a multisite, prospective, cohort study. Mental and motor functioning were assessed with the Bayley Scales of Infant Development (BSID), first and second editions. ARV exposure information was collected during pregnancy or within the first years of life. Linear regression methods were used to evaluate the association of in utero ARV exposure on Mental Developmental Index and Psychomotor Developmental Index at 2 years of age, controlling for demographic factors (age, gender, and race/ethnicity) and potential confounders: test version, primary language, primary caregiver, caregiver education level, low birth weight, geographic and urban/rural location, birth year, and maternal illicit drug use.

RESULTS

Among 1840 infants who were born between 1993 and 2006, 1694 (92%) were exposed to ARV in utero and 146 (8%) were not exposed. After controlling for confounders, children who were exposed in utero to any ARV did not have lower Mental Developmental Index and Psychomotor Developmental Index scores than unexposed children. Among low birth weight infants, significantly higher BSID scores were observed for prenatally ARV-exposed than unexposed children. Maternal illicit drug use was reported for 17% of mothers but was not associated with BSID scores.

CONCLUSIONS

Mental and motor functioning scores were not lower for infants with in utero ARV exposure compared with no exposure. Although these results are reassuring, continued evaluation of uninfected children with in utero ARV exposure for long-term adverse outcomes is important.

Mechanisms of antiretroviral therapy-induced mitochondrial dysfunction

PURPOSE OF REVIEW

To discuss novel developments related to the mechanisms of antiretroviral therapy-related mitochondrial toxicity, describe some apparent paradoxes in the current understanding of this field, and present questions that should be addressed by future research.

RECENT FINDINGS

The early polymerase gamma hypothesis states that nucleoside reverse transcriptase inhibitors can inhibit mitochondrial DNA replication and cause mitochondrial toxicity through mtDNA depletion. This mechanism is supported by a large body of evidence. Clinical manifestations of mitochondrial dysfunction are not always associated with mtDNA depletion. Increased mtDNA levels after nucleoside reverse transcriptase inhibitor exposure, as well as seemingly severe mtDNA depletion in individuals who show no clinical toxicity, have been reported. These and other observations suggest that additional mechanisms are involved in antiretroviral therapy toxicity, a notion supported by recent studies. Individuals given the same antiretroviral regimen can differ vastly with respect to the development of mitochondrial toxicity symptoms, reflecting interindividual variability. Some factors that may modulate this variability will be discussed.

SUMMARY

Mitochondrial toxicity induced by nucleoside reverse transcriptase inhibitors and their metabolic intermediates is probably mediated through many direct and indirect mechanisms. Depending on the mechanisms at play, the long-term health consequences of this toxicity may vary.

German-Austrian recommendations for HIV1-therapy in pregnancy and in HIV1-exposed newborn, update 2008

In Germany during the last years about 200-250 HIV1-infected pregnant women delivered a baby each year, a number that is currently increasing. To determine the HIV-status early in pregnancy voluntary HIV-testing of all pregnant women is recommended in Germany and Austria as part of prenatal care. In those cases, where HIV1-infection was known during pregnancy, since 1995 the rate of vertical transmission of HIV1 was reduced to 1-2%. - This low transmission rate has been achieved by the combination of anti-retroviral therapy of pregnant women, caesarean section scheduled before onset of labour, anti-retroviral post exposition prophylaxis in the newborn and refraining from breast-feeding by the HIV1-infected mother. To keep pace with new results in research, approval of new anti-retroviral drugs and changes in the general treatment recommendations for HIV1-infected adults, in 1998, 2001, 2003 and 2005 an interdisciplinary consensus meeting was held. Gynaecologists, infectious disease specialists, paediatricians, pharmacologists, virologists and members of the German AIDS Hilfe (NGO) were participating in this conference to update the prevention strategies. A fifth update became necessary in 2008. The updating process was started in January 2008 and was terminated in September 2008. The guidelines provide new recommendations on the indication and the starting point for HIV-therapy in pregnancies without complications, drugs and drug combinations to be used preferably in these pregnancies and updated information on adverse effects of anti-retroviral drugs. Also the procedures for different scenarios and risk constellations in pregnancy have been specified again. - With these current guidelines in Germany and Austria the low rate of vertical HIV1-transmission should be further maintained.

WR1065 mitigates AZT-ddI-induced mutagenesis and inhibits viral replication

The success of nucleoside reverse transcriptase inhibitors (NRTIs) in treating HIV-1 infection and reducing mother-to-child transmission of the virus during pregnancy is accompanied by evidence that NRTIs cause long-term health risks for cancer and mitochondrial disease. Thus, agents that mitigate toxicities of the current combination drug therapies are needed. Previous work had shown that the NRTI-drug pair zidovudine (AZT)-didanosine (ddI) was highly cytotoxic and mutagenic; thus, we conducted preliminary studies to investigate the ability of the active moiety of amifostine, WR1065, to protect against the deleterious effects of this NRTI-drug pair. In TK6 cells exposed to 100 muM AZT-ddI (equimolar) for 3 days with or without 150 muM WR1065, WR1065 enhanced long-term cell survival and significantly reduced AZT-ddI-induced mutations. Follow-up studies were conducted to determine if coexposure to AZT and WR1065 abrogated the antiretroviral efficacy of AZT. In human T-cell blasts infected with HIV-1 in culture, inhibition of p24 protein production was observed in cells treated with 10 muM AZT in the absence or presence of 5-1,000 muM WR1065. Surprisingly, WR1065 alone exhibited dose-related inhibition of HIV-1 p24 protein production. WR1065 also had antiviral efficacy against three species of adenovirus and influenza A and B. Intracellular levels of unbound WR1065 were measured following in vitro/in vivo drug exposure. These pilot study results indicate that WR1065, at low intracellular levels, has cytoprotective and antimutagenic activities against the most mutagenic pair of NRTIs and has broad spectrum antiviral effects. These findings suggest that the activities have a possible common mode of action that merits further investigation.

Mother to child transmission of HIV-1 in a Thai population: role of virus characteristics and maternal humoral immune response

The objective of this study was to investigate factors influencing mother to child transmission of HIV-1 in Thailand, where HIV-1 CRF01_AE, the major subtype in Southeast Asia, predominates. Samples from 84 HIV-1 infected, anti-retroviral treatment-naïve, non-breast feeding mothers, 28 who transmitted HIV-1 to their babies (transmitters) and 56 who did not (non-transmitters), were studied for maternal humoral immune response and virus characteristics. Maternal humoral immune response was measured by lymphocyte phenotyping; neutralizing antibodies to laboratory HIV-1 MN strain and two clinical isolates; peptide binding antibody to gp41 and V3 from strains CRF01_AE, B, and MN; autologous antibodies; and quasispecies diversity. Virus characteristics studied were viral load, co-receptor usage, and viral replication capacity. No significant difference between transmitters and non-transmitters was found for any parameter of maternal humoral immune response. However, viral load and viral replication capacity were significantly higher in transmitters versus non-transmitters and were not correlated with each other. This suggests that viral replication capacity may be a transmission factor independent of viral load, which is already well established as a risk factor for transmission of HIV-1. All except four viral isolates used the CCR5 co-receptor. This is one of few studies of vertical transmission in a population where HIV-1 CRF01_AE predominates. The data suggest that in this population the maternal humoral immune response was not important in preventing transmission at parturition, but that virus characteristics were key factors, and that viral replication capacity may contribute to birth-associated mother to child transmission of HIV-1.

Mutational analysis of the mitochondrial tRNA genes and flanking regions in umbilical cord tissue from uninfected infants receiving AZT-based therapies for prophylaxis of HIV-1

A sensitive vertical denaturing gradient gel electrophoresis (DGGE) method, using 13 unipolar psoralen-clamped PCR primer pairs, was developed for detecting sequence variants in the 22 tRNA genes and flanking regions (together spanning approximately 21%) of the human mitochondrial genome. A study was conducted to determine (i) if mitochondrial DNA (mtDNA) polymorphisms and/or mutations were detectable in healthy newborns and (ii) if prepartum 3'-azido-2',3'-dideoxythymidine (AZT) based HIV-1 prophylaxis was associated with significant increases in mtDNA mutations and changes in the degree of heteroplasmy of sequence variants in uninfected infants born to HIV-1-infected mothers. DGGE analysis of umbilical cord tissue (where vascular endothelium and smooth muscle cells are the major source of mtDNA) showed that mtDNA sequence variants were significantly elevated by threefold in AZT-treated infants compared with unexposed controls (P < 0.001), with 24 changes observed in 19/52 (37%) treated newborns (averaging 0.46 changes/subject) versus only eight changes found in 7/55 (13%) unexposed newborns (averaging 0.15 changes/subject). Six distinct sequence variants occurring in unexposed controls were predominately synonymous and homoplasmic, representing previously reported polymorphisms. Uninfected infants exposed to a combination of AZT and 2',3'-dideoxy-3'-thiacytidine and "maternal HIV-1" had a significant shift in the spectrum of mutations (P = 0.04) driven by increases in nonsynonymous heteroplasmic sequence variants at polymorphic sites (10 distinct variants) and novel sites (four distinct variants). While the weight of evidence suggests that prepartum AZT-based prophylaxis produces mtDNA mutations, additional research is needed to determine the degree to which fetal responses to maternal HIV-1 infection, in the absence of antiretroviral treatment, contribute to prenatal mtDNA mutagenesis.

K-ras cancer gene mutations in lung tumors from female Swiss (CD-1) mice exposed transplacentally to 3'-azido-3'-deoxythymidine

A transplacental carcinogenicity study was conducted by exposing pregnant Swiss (CD-1) mice to 0, 50, 100, 200, or 300 mg 3'-azido-3'-deoxythymidine (AZT)/kg body weight (BW) daily for the duration of gestation (18-19 days) [National Toxicology Program,2006]. The incidence of alveolar/bronchiolar adenomas and carcinomas in the 200 and 300 mg/kg groups was significantly higher (P = 0.027 and 0.007, respectively) in male offspring, but not in females (P = 0.338 and 0.315, respectively). The purpose of the present study was to evaluate K-ras mutation status in lung tumors from the female offspring in AZT exposed groups and to determine whether at the molecular level there were signature K-ras mutations in lung tumors that were different from spontaneous tumors. K-ras mutation was detected by cycle sequencing of polymerase chain reaction (PCR)-amplified DNA, isolated from formalin-fixed, paraffin-embedded lung tumors. K-ras mutations were detected in 17 of 28 (61%) lung tumors from the female offspring in AZT exposed groups. No K-ras mutations were detected in the 8 tumors examined from the female control group. The predominant mutations were Codon 12 G-->T transversions in the 50, 100, and 300 mg/kg groups, and Codon 12 G-->C transversions in the 200 and 300 mg/kg groups. K-ras Codon 12 G-->T transversions (TGT mutations) may be induced by oxidative DNA damage and 8-oxoguanine (8-oxoG), while K-ras Codon 12 G-->C transversions (CGT mutations) may be due to further oxidative lesions of guanine and 8-oxoG.