About

James A. Hoxie, M.D., is an Emeritus Professor of Medicine (Hematology-Oncology) at the Perelman School of Medicine at the University of Pennsylvania. He serves as Co-Director of the Penn Center for AIDS Research, specifically overseeing the Nonhuman Primate Core, and is a member of the Department of Medicine's Committee on Appointments and Promotions. Dr. Hoxie's research focuses on the viral and cellular aspects of HIV and SIV entry into cells, HIV and SIV pathogenesis, mechanisms of viral resistance to the host immune response, neutralizing antibodies, and gene therapy of HIV infection. His work includes identifying viral and cellular determinants relevant to HIV and SIV infection and immune evasion, with specific emphasis on the role of the HIV/SIV cytoplasmic tail in pathogenesis, studies of CD4-independent isolates of HIV, and the development of modified HIV envelope glycoproteins for vaccine research. Dr. Hoxie has contributed to understanding how mutations in viral proteins affect infectivity and immune response, and he has been involved in gene therapy approaches using fusion inhibitory peptides. His research aims to inform vaccine design and therapeutic strategies against HIV/AIDS.

Research topics

• Biology
• Virology
• Immunology
• Cell biology
• Molecular biology

Selected publications

• Dynamics of natural and pharmacologic control of an SIV variant with an envelope trafficking defect

  The Journal of Experimental Medicine · 2025-11-04

  articleOpen access

  Insights into HIV-1 pathogenesis have come from studies of viral dynamics. However, there is little information on viral dynamics in lentiviral infections in which viral replication is naturally controlled in a subset of infected individuals. We evaluated the decay of simian immunodeficiency virus (SIV) RNA and cell-associated SIV genomes in a nonhuman primate (NHP) model in which replication of an engineered SIV variant is naturally controlled by cellular immune responses in most infected animals. This variant lacks a trafficking motif in the gp41 cytoplasmic tail. A trajectory of control was evident by 21 days after infection. In animals with natural control, we observed similar biphasic decay of intact proviruses in blood and lymph nodes, at rates close to those in animals that failed to control the virus and were put on antiretroviral therapy (ART). Both natural control and ART effectively blocked viral evolution, but not persistence. Thus, in this NHP model, natural control can be nearly as effective as ART in controlling viral replication.

  PublisherDOI

• Depletion and recovery of IgG following treatment with Rozanoliximab and Imlifidase in pigtail macaques

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-11-13

  preprintOpen access

  Abstract Antibodies are central players in adaptive immunity, providing protection against a wide array of pathogens through mechanisms such as neutralization, opsonization, recruitment of effector immune cells, complement activation and engagement. However, in other contexts, these same effector functions can contribute to immunopathology, particularly when antibodies are developed against self-antigens, resulting in autoimmunity. Understanding the role antibodies play in preventing or causing disease is often supported by studies in model systems wherein manipulation of IgG levels can be used as an experimental tool. Here, we report in simian immunodeficiency virus (SIV) infected pigtail macaques ( Macaca nemestrina ) the capacity of two orthogonal strategies to systemically deplete IgG – treatment with a neonatal Fc receptor blocking antibody (Rozanolixizumab) that restricts IgG rescue and recycling, and administration of the IgG protease Imlifidase (IdeS) that cleaves the Fc domain. Under the conditions evaluated, we observed more rapid and effective, although not necessarily more durable, IgG depletion mediated by IdeS, reducing levels by 74.1-95.1%, compared to a lesser reduction of 31.3-66.9% with anti-FcRn treatment. We observed a similar degree of depletion, comparable kinetics of rebound among SIV antigen-specific fractions as total IgG, but differential balance among IgG subclasses following treatment in some cases. In sum, this study in a nonhuman primate model describes the efficacy and downstream impacts of new tools to modify humoral immune states providing insight into the balance between protective and pathological effects of IgG antibodies.

  PublisherOA PDFDOI

• The Impact of SIV-Induced Immunodeficiency on SARS-CoV-2 Disease, Viral Dynamics, and Antiviral Immune Response in a Nonhuman Primate Model of Coinfection

  Viruses · 2024-07-21 · 1 citations

  articleOpen access

  The effects of immunodeficiency associated with chronic HIV infection on COVID-19 disease and viral persistence have not been directly addressed in a controlled setting. In this pilot study, we exposed two pigtail macaques (PTMs) chronically infected with SIVmac239, exhibiting from very low to no CD4 T cells across all compartments, to SARS-CoV-2. We monitored the disease progression, viral replication, and evolution, and compared these outcomes with SIV-naïve PTMs infected with SARS-CoV-2. No overt signs of COVID-19 disease were observed in either animal, and the SARS-CoV-2 viral kinetics and evolution in the SIVmac239 PTMs were indistinguishable from those in the SIV-naïve PTMs in all sampled mucosal sites. However, the single-cell RNA sequencing of bronchoalveolar lavage cells revealed an infiltration of functionally inert monocytes after SARS-CoV-2 infection. Critically, neither of the SIV-infected PTMs mounted detectable anti-SARS-CoV-2 T-cell responses nor anti-SARS-CoV-2 binding or neutralizing antibodies. Thus, HIV-induced immunodeficiency alone may not be sufficient to drive the emergence of novel viral variants but may remove the ability of infected individuals to mount adaptive immune responses against SARS-CoV-2.

  PublisherOA PDFDOI

• The Impact of SIV-Induced Immunodeficiency on Clinical Manifestation, Immune Response, and Viral Dynamics in SARS-CoV-2 Coinfection

  bioRxiv (Cold Spring Harbor Laboratory) · 2023-11-16

  preprintOpen access

  Persistent and uncontrolled SARS-CoV-2 replication in immunocompromised individuals has been observed and may be a contributing source of novel viral variants that continue to drive the pandemic. Importantly, the effects of immunodeficiency associated with chronic HIV infection on COVID-19 disease and viral persistence have not been directly addressed in a controlled setting. Here we conducted a pilot study wherein two pigtail macaques (PTM) chronically infected with SIVmac239 were exposed to SARS-CoV-2 and monitored for six weeks for clinical disease, viral replication, and viral evolution, and compared to our previously published cohort of SIV-naïve PTM infected with SARS-CoV-2. At the time of SARS-CoV-2 infection, one PTM had minimal to no detectable CD4+ T cells in gut, blood, or bronchoalveolar lavage (BAL), while the other PTM harbored a small population of CD4+ T cells in all compartments. Clinical signs were not observed in either PTM; however, the more immunocompromised PTM exhibited a progressive increase in pulmonary infiltrating monocytes throughout SARS-CoV-2 infection. Single-cell RNA sequencing (scRNAseq) of the infiltrating monocytes revealed a less activated/inert phenotype. Neither SIV-infected PTM mounted detectable anti-SARS-CoV-2 T cell responses in blood or BAL, nor anti-SARS-CoV-2 neutralizing antibodies. Interestingly, despite the diminished cellular and humoral immune responses, SARS-CoV-2 viral kinetics and evolution were indistinguishable from SIV-naïve PTM in all sampled mucosal sites (nasal, oral, and rectal), with clearance of virus by 3-4 weeks post infection. SIV-induced immunodeficiency significantly impacted immune responses to SARS-CoV-2 but did not alter disease progression, viral kinetics or evolution in the PTM model. SIV-induced immunodeficiency alone may not be sufficient to drive the emergence of novel viral variants.

  PublisherOA PDFDOI

• A cellular trafficking signal in the SIV envelope protein cytoplasmic domain is strongly selected for in pathogenic infection

  PLoS Pathogens · 2022-06-17 · 6 citations

  articleOpen accessSenior authorCorresponding

  The HIV/SIV envelope glycoprotein (Env) cytoplasmic domain contains a highly conserved Tyr-based trafficking signal that mediates both clathrin-dependent endocytosis and polarized sorting. Despite extensive analysis, the role of these functions in viral infection and pathogenesis is unclear. An SIV molecular clone (SIVmac239) in which this signal is inactivated by deletion of Gly-720 and Tyr-721 (SIVmac239ΔGY), replicates acutely to high levels in pigtail macaques (PTM) but is rapidly controlled. However, we previously reported that rhesus macaques and PTM can progress to AIDS following SIVmac239ΔGY infection in association with novel amino acid changes in the Env cytoplasmic domain. These included an R722G flanking the ΔGY deletion and a nine nucleotide deletion encoding amino acids 734-736 (ΔQTH) that overlaps the rev and tat open reading frames. We show that molecular clones containing these mutations reconstitute signals for both endocytosis and polarized sorting. In one PTM, a novel genotype was selected that generated a new signal for polarized sorting but not endocytosis. This genotype, together with the ΔGY mutation, was conserved in association with high viral loads for several months when introduced into naïve PTMs. For the first time, our findings reveal strong selection pressure for Env endocytosis and particularly for polarized sorting during pathogenic SIV infection in vivo.

  PublisherDOI

• Broad coverage of neutralization-resistant SIV strains by second-generation SIV-specific antibodies targeting the region involved in binding CD4

  PLoS Pathogens · 2022-06-16 · 17 citations

  articleOpen access

  Both SIV and SHIV are powerful tools for evaluating antibody-mediated prevention and treatment of HIV-1. However, owing to a lack of rhesus-derived SIV broadly neutralizing antibodies (bnAbs), testing of bnAbs for HIV-1 prevention or treatment has thus far been performed exclusively in the SHIV NHP model using bnAbs from HIV-1-infected individuals. Here we describe the isolation and characterization of multiple rhesus-derived SIV bnAbs capable of neutralizing most isolates of SIV. Eight antibodies belonging to two clonal families, ITS102 and ITS103, which target unique epitopes in the CD4 binding site (CD4bs) region, were found to be broadly neutralizing and together neutralized all SIV strains tested. A rare feature of these bnAbs and two additional antibody families, ITS92 and ITS101, which mediate strain-specific neutralizing activity against SIV from sooty mangabeys (SIVsm), was their ability to achieve near complete (i.e. 100%) neutralization of moderately and highly neutralization-resistant SIV. Overall, these newly identified SIV bnAbs highlight the potential for evaluating HIV-1 prophylactic and therapeutic interventions using fully simian, rhesus-derived bnAbs in the SIV NHP model, thereby circumventing issues related to rapid antibody clearance of human-derived antibodies, Fc mismatch and limited genetic diversity of SHIV compared to SIV.

  PublisherOA PDFDOI

• HIV-1–Infected CD4+ T Cells Present MHC Class II–Restricted Epitope via Endogenous Processing

  The Journal of Immunology · 2022-09-01 · 7 citations

  articleOpen access

  Abstract HIV-1–specific CD4+ T cells (TCD4+s) play a critical role in controlling HIV-1 infection. Canonically, TCD4+s are activated by peptides derived from extracellular (“exogenous”) Ags displayed in complex with MHC class II (MHC II) molecules on the surfaces of “professional” APCs such as dendritic cells (DCs). In contrast, activated human TCD4+s, which express MHC II, are not typically considered for their APC potential because of their low endocytic capacity and the exogenous Ag systems historically used for assessment. Using primary TCD4+s and monocyte-derived DCs from healthy donors, we show that activated human TCD4+s are highly effective at MHC II–restricted presentation of an immunodominant HIV-1–derived epitope postinfection and subsequent noncanonical processing and presentation of endogenously produced Ag. Our results indicate that, in addition to marshalling HIV-1–specific immune responses during infection, TCD4+s also act as APCs, leading to the activation of HIV-1–specific TCD4+s.

  PublisherOA PDFDOI

• The pigtail macaque ( <i>Macaca nemestrina</i> ) model of COVID-19 reproduces diverse clinical outcomes and reveals new and complex signatures of disease

  bioRxiv (Cold Spring Harbor Laboratory) · 2021-08-30 · 4 citations

  preprintOpen access

  Abstract The novel coronavirus SARS-CoV-2, the causative agent of COVID-19 disease, has killed over four million people worldwide as of July 2021 with infections rising again due to the emergence of highly transmissible variants. Animal models that faithfully recapitulate human disease are critical for assessing SARS-CoV-2 viral and immune dynamics, for understanding mechanisms of disease, and for testing vaccines and therapeutics. Pigtail macaques (PTM, Macaca nemestrina ) demonstrate a rapid and severe disease course when infected with simian immunodeficiency virus (SIV), including the development of severe cardiovascular symptoms that are pertinent to COVID-19 manifestations in humans. We thus proposed this species may likewise exhibit severe COVID-19 disease upon infection with SARS-CoV-2. Here, we extensively studied a cohort of SARS-CoV-2-infected PTM euthanized either 6- or 21-days after respiratory viral challenge. We show that PTM demonstrate largely mild-to-moderate COVID-19 disease. Pulmonary infiltrates were dominated by T cells, including CD4+ T cells that upregulate CD8 and express cytotoxic molecules, as well as virus-targeting T cells that were predominantly CD4+. We also noted increases in inflammatory and coagulation markers in blood, pulmonary pathologic lesions, and the development of neutralizing antibodies. Together, our data demonstrate that SARS-CoV-2 infection of PTM recapitulates important features of COVID-19 and reveals new immune and viral dynamics and thus may serve as a useful animal model for studying pathogenesis and testing vaccines and therapeutics.

  PublisherOA PDFDOI

• The pigtail macaque (Macaca nemestrina) model of COVID-19 reproduces diverse clinical outcomes and reveals new and complex signatures of disease

  PLoS Pathogens · 2021-12-20 · 19 citations

  articleOpen accessCorresponding

  The novel coronavirus SARS-CoV-2, the causative agent of COVID-19 disease, has killed over five million people worldwide as of December 2021 with infections rising again due to the emergence of highly transmissible variants. Animal models that faithfully recapitulate human disease are critical for assessing SARS-CoV-2 viral and immune dynamics, for understanding mechanisms of disease, and for testing vaccines and therapeutics. Pigtail macaques (PTM, Macaca nemestrina) demonstrate a rapid and severe disease course when infected with simian immunodeficiency virus (SIV), including the development of severe cardiovascular symptoms that are pertinent to COVID-19 manifestations in humans. We thus proposed this species may likewise exhibit severe COVID-19 disease upon infection with SARS-CoV-2. Here, we extensively studied a cohort of SARS-CoV-2-infected PTM euthanized either 6- or 21-days after respiratory viral challenge. We show that PTM demonstrate largely mild-to-moderate COVID-19 disease. Pulmonary infiltrates were dominated by T cells, including CD4+ T cells that upregulate CD8 and express cytotoxic molecules, as well as virus-targeting T cells that were predominantly CD4+. We also noted increases in inflammatory and coagulation markers in blood, pulmonary pathologic lesions, and the development of neutralizing antibodies. Together, our data demonstrate that SARS-CoV-2 infection of PTM recapitulates important features of COVID-19 and reveals new immune and viral dynamics and thus may serve as a useful animal model for studying pathogenesis and testing vaccines and therapeutics.

  PublisherDOI

• A tyrosine-based trafficking signal in the simian immunodeficiency virus envelope cytoplasmic domain is strongly selected for in pathogenic SIV infection

  bioRxiv (Cold Spring Harbor Laboratory) · 2021-03-31 · 1 citations

  preprintOpen accessSenior authorCorresponding

  SUMMARY The HIV/SIV envelope glycoprotein (Env) cytoplasmic domain contains a highly conserved Tyr-dependent trafficking signal that mediates both clathrin-dependent endocytosis and polarized sorting of Env. Despite extensive characterization, the role of these functions in viral infection and pathogenesis is unclear. An SIV molecular clone (SIVmac239) in which the Tyr-based signal is inactivated by deletion of Gly-720 and Tyr-721 (SIVmac239ΔGY) replicates to high levels acutely in pigtail macaques (PTM) but is rapidly controlled. We previously reported that rhesus macaques and PTM can progress to AIDS following SIVmac239ΔGY infection in association with novel amino acid changes in the Env cytoplasmic domain. These included an R722G flanking the ΔGY deletion and a nine nucleotide deletion that encodes amino acids 734-736 (ΔQTH) and overlaps with the rev and tat open reading frames. We show that molecular clones containing these mutations reconstitute signals for both endocytosis and polarized sorting. In one PTM, a novel genotype was selected, which generated a new signal for polarized sorting but not endocytosis. This mutation by itself was sufficient to maintain high viral loads for several months when introduced into naïve PTMs. These findings reveal, for the first time, strong selection pressure for Env endocytosis and, in particular, for polarized sorting during pathogenic SIV infection in vivo .

  PublisherOA PDFDOI

Recent grants

• NIH Grant U01AI023630

  NIH · $385k · 1989

• NIH Grant R01AI033854

  NIH · $2.9M · 2001

• Pathogenic determinants of the SIV envelope transmembrane cytoplasmic domain

  NIH · $6.4M · 2008–2017

• NIH Grant P51RR000164

  NIH · $54.5M · 2013

• NIH Grant R01AI038225

  NIH · $1.3M · 1999

Frequent coauthors

• W R Benjamin

  81 shared

• Randall M. Rossi

  Pennsylvania State University

  81 shared

• Steven Fischkoff

  81 shared

• Linda A. Anderson

  81 shared

• Kenji Kishi

  Tsurumi University

  81 shared

• J Hakimi

  81 shared

• Michel C. Hoessly

  University of Pennsylvania

  81 shared

• Teruko Ishizaka

  81 shared

Labs

• Hoxie LabPI

Education

• MD, Medicine

  University of Pennsylvania

  1976