Abigail Spinner

Biological Effects of Short-Term or Prolonged Administration of 9-[2-(Phosphonomethoxy)Propyl]Adenine (Tenofovir) to Newborn and Infant Rhesus Macaques

ABSTRACT The reverse transcriptase inhibitor 9-[2-(phosphonomethoxy)propyl]adenine (PMPA; tenofovir) was previously found to offer strong prophylactic and therapeutic benefits in an infant macaque model of pediatric human immunodeficiency virus (HIV) infection. We now summarize the toxicity and safety of PMPA in these studies. When a range of PMPA doses (4 to 30 mg/kg of body weight administered subcutaneously once daily) was administered to 39 infant macaques for a short period of time (range, 1 day to 12 weeks), no adverse effects on their health or growth were observed; this included a subset of 12 animals which were monitored for more than 2 years. In contrast, daily administration of a high dose of PMPA (30 mg/kg subcutaneously) for prolonged periods of time (>8 to 21 months) to 13 animals resulted in a Fanconi-like syndrome (proximal renal tubular disorder) with glucosuria, aminoaciduria, hypophosphatemia, growth restriction, bone pathology (osteomalacia), and reduced clearance of PMPA. The adverse effects were reversible or were alleviated following either complete withdrawal of PMPA treatment or reduction of the daily regimen from 30 mg/kg to 2.5 to 10 mg/kg subcutaneously. Finally, to evaluate the safety of a prolonged low-dose treatment regimen, two newborn macaques were started on a 10-mg/kg/day subcutaneous regimen; these animals are healthy and have normal bone density and growth after 5 years of daily treatment. In conclusion, our findings suggest that chronic daily administration of a high dose of PMPA results in adverse effects on kidney and bone, while short-term administration of relatively high doses and prolonged low-dose administration are safe.

Chronic Administration of Tenofovir to Rhesus Macaques from Infancy through Adulthood and Pregnancy: Summary of Pharmacokinetics and Biological and Virological Effects

ABSTRACT The reverse transcriptase (RT) inhibitor tenofovir (TFV) is highly effective in the simian immunodeficiency virus (SIV) macaque model of human immunodeficiency virus infection. The current report describes extended safety and efficacy data on 32 animals that received prolonged (≥1- to 13-year) daily subcutaneous TFV regimens. The likelihood of renal toxicity (proximal renal tubular dysfunction [PRTD]) correlated with plasma drug concentrations, which depended on the dosage regimen and age-related changes in drug clearance. Below a threshold area under the concentration-time curve for TFV in plasma of ∼10 μg·h/ml, an exposure severalfold higher than that observed in humans treated orally with 300 mg TFV disoproxil fumarate (TDF), prolonged TFV administration was not associated with PRTD based on urinalysis, serum chemistry analyses, bone mineral density, and clinical observations. At low-dose maintenance regimens, plasma TFV concentrations and intracellular TFV diphosphate concentrations were similar to or slightly higher than those observed in TDF-treated humans. No new toxicities were identified. The available evidence does not suggest teratogenic effects of prolonged low-dose TFV treatment; by the age of 10 years, one macaque, on TFV treatment since birth, had produced three offspring that were healthy by all criteria up to the age of 5 years. Despite the presence of viral variants with a lysine-to-arginine substitution at codon 65 (K65R) of RT in all 28 SIV-infected animals, 6 animals suppressed viremia to undetectable levels for as long as 12 years of TFV monotherapy. In conclusion, these findings illustrate the safety and sustained benefits of prolonged TFV-containing regimens throughout development from infancy to adulthood, including pregnancy.

Asymptomatic Infection of the Central Nervous System by the Macaque Immunosuppressive Type D Retrovirus, SRV-1

The aetiological agent of spontaneously occurring simian acquired immune deficiency syndrome (SAIDS) in rhesus monkeys (Macaca mulatta) at the California Primate Research Center is a type D retrovirus designated SAIDS retrovirus serotype 1 (SRV-1). SRV-1 DNA and RNA have previously been detected in the brains of rhesus monkeys with SAIDS in the absence of viral antigen or neuropathological lesions. In this study we further define the relationship between SRV-1 and the central nervous system (CNS) in rhesus monkeys by examining the CNS for infectious SRV-1, viral antigen and anti-SRV-1 antibodies. In addition, cerebrospinal fluid (CSF) was assayed for alterations in IgG and albumin levels, IgG/albumin ratios and cell count in comparison to uninfected control animals. No differences in CSF parameters were detected between infected and uninfected animals except for the presence of infectious SRV-1 which was isolated from the CSF from 13 out of 19 (68%) viraemic rhesus monkeys. The probable source of this virus was the choroid plexus, where approximately 1 in 1000 surface epithelial cells were found to contain viral antigen by immunohistochemistry. Antibodies against SRV-1 were not detected in the CSF even when present in the serum. Neither infectious virus nor viral antigen were found in the brain parenchyma of any animal examined. Thus infection of the CNS by SRV-1 appears to be subclinical without an intrathecal immune response. This may be related to the apparent restriction of productive infection in the CNS to cells of the choroid plexus.

Compared with cyclosporine, ISATX247 significantly prolongs renal-allograft survival in a nonhuman primate model

Background. ISATX247 is a novel calcineurin inhibitor that has shown more potency than cyclosporine in vitro. This is the first study to compare the survival times of renal allografts in nonhuman primates treated with either ISATX247 or cyclosporine. Methods. Adult, male cynomolgus monkeys were divided into blood-group compatible and mixed-lymphocyte, stimulation-mismatched, donor-recipient pairs. Heterotopic renal transplantation and bilateral native nephrectomies were performed. The monkeys were placed into either an ISATX247 or cyclosporine treatment group. Both groups were dosed twice daily to maintain a 12-hour drug-trough level of 150 ng/mL. Whole-blood concentrations of ISATX247 and cyclosporine, complete blood counts, and serum chemistry profiles were performed three times a week. Euthanasia was performed if the serum creatinine concentration became 7 or more mg/dL or a serious complication developed. Results. The group receiving ISATX247 (n=8) survived significantly (P=0.0036) longer than the group receiving cyclosporine (n=7). The mean trough blood concentration of ISATX247 was 120±32 ng/mL and cyclosporine was 189±130 ng/mL. The average area under the curve0–12 for ISATX247 was 6045±1679 ng/mL/hr and for cyclosporine was 4919±823 ng/mL/hr. The average calcineurin inhibition at trough blood concentrations was 80±11% for ISATX247 and 48±12% for cyclosporine. Conclusions. Allografts in monkeys treated with ISATX247 survived significantly longer than those treated with cyclosporine. On the basis of survival times and degree of calcineurin inhibition, ISATX247 is a more potent immunosuppressive agent than cyclosporine in this nonhuman primate model of renal-allograft transplantation.

Genomic Comparison of Campylobacter spp. and Their Potential for Zoonotic Transmission between Birds, Primates, and Livestock

ABSTRACT Campylobacter is the leading cause of human gastroenteritis worldwide. Wild birds, including American crows, are abundant in urban, suburban, and agricultural settings and are likely zoonotic vectors of Campylobacter. Their proximity to humans and livestock increases the potential spreading of Campylobacter via crows between the environment, livestock, and humans. However, no studies have definitively demonstrated that crows are a vector for pathogenic Campylobacter. We used genomics to evaluate the zoonotic and pathogenic potential of Campylobacter from crows to other animals with 184 isolates obtained from crows, chickens, cows, sheep, goats, humans, and nonhuman primates. Whole-genome analysis uncovered two distinct clades of Campylobacter jejuni genotypes; the first contained genotypes found only in crows, while a second genotype contained “generalist” genomes that were isolated from multiple host species, including isolates implicated in human disease, primate gastroenteritis, and livestock abortion. Two major β-lactamase genes were observed frequently in these genomes (oxa-184, 55%, and oxa-61, 29%), where oxa-184 was associated only with crows and oxa-61 was associated with generalists. Mutations in gyrA, indicative of fluoroquinolone resistance, were observed in 14% of the isolates. Tetracycline resistance (tetO) was present in 22% of the isolates, yet it occurred in 91% of the abortion isolates. Virulence genes were distributed throughout the genomes; however, cdtC alleles recapitulated the crow-only and generalist clades. A specific cdtC allele was associated with abortion in livestock and was concomitant with tetO. These findings indicate that crows harboring a generalist C. jejuni genotype may act as a vector for the zoonotic transmission of Campylobacter. IMPORTANCE This study examined the link between public health and the genomic variation of Campylobacter in relation to disease in humans, primates, and livestock. Use of large-scale whole-genome sequencing enabled population-level assessment to find new genes that are linked to livestock disease. With 184 Campylobacter genomes, we assessed virulence traits, antibiotic resistance susceptibility, and the potential for zoonotic transfer to observe that there is a “generalist” genotype that may move between host species.