Research Initiatives on AIDS and HIV in the Division of Translational Toxicology

National Institute Of Environmental Health Sciences

Investigators

Linked publications, trials & patents

Abstract

In the effective management of HIV infections and AIDS, antiretroviral therapies (ART) have significantly contributed to shift the disease from a fatal infection in the early 90s to current a chronically managed condition. Initial medicines used to treat HIV consisted of nucleotide reverse transcriptase inhibitors (NRTIs), which aimed at blocking viral replication. These drugs had severe side effects due to off-target mitochondrial toxicity and over the years have been replaced, to some extent, by administration of less toxic drugs that are now provided in combination (cART). Despite this, new generation NRTIs remain a staple of cART. These combination drug therapies are required to maintain low viremia in children and adult HIV-positive patients; they are also prescribed prophylactically to individuals at high risk of contracting the virus (e.g., spouse HIV positive). While beneficial, the various combination therapies are not without potential health-related concerns. Prominent issues have been raised with regards to lipid metabolism and increased body weight, cognitive and cardiac function, immune response, and bone growth. Because these drugs are now provided throughout life, the effects associated with chronic exposures, particularly of vulnerable populations such as pregnant women and their fetus, children and elderly patients, are of increased concern. It has therefore become imperative to understand the unintended long-term health effects associated with chronic cART exposure. Given the severity of HIV/AIDS, therapeutic intervention to regulate viral load is necessary. However, the ability to identify and characterize adverse effects of the drugs and potential interactions with viral load is limited when working in models that express the viral proteins. Thus, the DTT research initiative has focused on the effects of exposure to HIV therapeutics in the absence of the HIV virus. Using experimental rodent and in vitro models, effects on maternal health and their offspring exposed to the drugs via the dam during gestation and lactation as well as when animals aged were examined. Current efforts have included reproductive, developmental, cardiovascular, and nervous system outcomes of direct exposure of pregnant dams, and their indirectly exposed offspring, to the 3 active ingredients (abacavir, dolutegravir and lamivudine) of the drug commercially available as Triumeq. Triumeq was until June 2025 the guideline drug combination prescribed during pregnancy. Additionally, we are in the early stages of toxicokinetic studies of the drug combination that includes bictegravir/emtricitabine/tenofovir alafenamide (commercially available as Biktarvy), which since June 2025 is the guideline combination for pregnant women. It is also the most prescribed HIV medication in North America. Studies on Abacavir/dolutegravir/lamivudine 1) Developmental and Reproductive Studies The DTT program has a long-standing interest in evaluating the potential adverse effects on reproduction and development using experimental animal models, assessing potential liabilities associated with gestational and lactational exposures. In this effort, pregnant rats were treated from gestational day 6 (GD6) until postnatal day 28 (PND28), with pups indirectly exposed in utero and via lactation. After weaning, pups were evaluated over a 15-week period for clinical observations, body weight, food consumption, developmental and reproductive indices, and clinical- and histo-pathology parameters. In addition, maternal-fetal and offspring exposure levels were measured. Examination of the offspring showed no effects on general health up until ~5 months of age. Detailed evaluation of data collected from clinical and histopathological parameters representing a wide array of organ systems, in both dams and pups, are in process and a report expected to be written in the next year. 2) Cardiovascular Studies For the cardiovascular work, dams were treated continuously from GD6 until PND120, while pups were exposed until weaning, then aged to 4 and 12 months without additional drug exposure. Functional (electrocardiograms and echocardiograms), biochemical and genomics parameters were then assessed in the animals. Dams and pups were evaluated at PND21 and PND120, and a pup cohort aged to 12 months was evaluated then. A summary of the effects on dams and offspring is shown below. Dams: functional data suggest impact on pregnancy-associated reverse remodeling involving both direct cardiac effects of the drugs, including on mitochondrial DNA content, function and cardiomyocyte metabolism, as well as in the liver. Drugs were identified as accumulating in the heart and the liver, in addition to serum, with the liver showing transcriptional signs of mitochondrial toxicity. Notably, only the NRTIs were found to be abundant in the tissues, suggesting that they drive the effects observed. Weight gain was prominent in the treated animals despite no increase in food consumption, consistent with epidemiological data. The manuscript to report these findings is under preparation. Offspring: males and female offspring show decreased contractile and electrophysiological parameters at weaning. However, only males had significant cardiac dysfunction at one year of age, indicating sex differences in the long-term effects of perinatal exposure to abacavir, dolutegravir and lamivudine. RNA-seq identified a robust transcriptional response in females, but not males, at weaning. Conversely, significant gene expression changes were observed in the male, but not female, heart tissue at one year of age. In both cases, significant alteration on mitochondrial carbon metabolism (from fatty acid to glucose) was identified, but with different kinetics: at PND21 for females, at 12 months for males. Mitochondria content was changed in the heart of the pups, with effects more prominent in males. This suggests different responses based on sex. When compare to the effects of the dams, these results also suggest distinct effects based on the life-stage of exposure Additional in vitro experiments are underway to better understand the mechanisms associated with the protracted effects of the drugs in the heart of the developmentally-exposed animals. Feces and intestines of the animals at one year of age were collected to define if the drugs might affect the gut microbiome. Three manuscripts have been published on this subject; data have indicated significant changes in the gut microbiome that have the potential to influence the cardiac outcomes. Additional studies are underway to better understand this relationship. 3) Neurological Studies Our work has 4 main areas of emphasis: alterations in the early life neural network formation, manifestation of alterations in targeted behavioral functions as related to the human patient, unmasking underlying alterations by targeted pharmacological or environmental challenges including aging, and the dysregulation of yolk-sac derived tissue resident macrophages as a target for early developmental exposures. Using the same exposure regimen as that used for the developmental study, we showed no alterations in young adult offspring in various fear-based behavioral tests, motor function appeared normal. Upon pharmacological challenge of the dopaminergic and glutamatergic neurotransmitter systems, a subtle shift in sensitivity was observed in males but not in females. Developmentally related gene expression profiles suggested alteration in the pattern of axonal elongation and synapse formation. This was accompanied by a subtle morphological shift in microglia and astrocytes. Future experiments are planned to explore this developmental gene expression pattern in further depth with the assessment of age dependent shifts supported by anatomical evaluations. The role of neuro-immune cells across the life span is complex and directed towards regulating the cellular environment and allowing for successful development, maintenance, and aging. With dysregulation, a multitude of subtle effects can occur and alter each of these processes with long-lasting effects. Our research identified a shift in the response to a challenge of lipopolysaccharide in aged rats that had been developmentally exposed to the cART. The lower level of response was suggestive of a diminished ability to respond. This was reflected in a systemic response and in targeted brain regions raising questions regarding accelerated inflammaging. Future experiments are ongoing to examine this response in greater detail including assessment using rodent and human cell culture models. Studies on bictegravir/emtricitabine/tenofovir alafenamide 1) Toxicokinetics Studies Pre-test chemistry is underway with some challenges with the drug formulation being currently addressed. Upon completion of this phase, exposure to adult male and female animals will initiate. This is expected in late fall 2025.