The Tulane National Primate Research Center is involved in a variety of important multidisciplinary projects focusing on areas of biomedical research with high priority concerns for human health. This section, which is intended for the interested researcher, scientist or investigator, provides information on those research programs and projects. The following research program summaries are selected from a number of programs at the Center and are not meant to be inclusive of all research efforts at the Center.
Advances in HIV transmission
In the last funding period, we have made several key discoveries in the prevention, pathogenesis and treatment of SIV/SHIV in macaques as a model for HIV prevention and treatment strategies. Recently, working with collaborators at Northwestern University we discovered that Th17 cells in the female reproductive tract are among the first cells infected after vaginal exposure to SIV/SHIV. In addition, we have also been examining the cellular and molecular mechanisms of penile, vaginal, and rectal transmission and are testing new methods for prevention of infection through modulating the mucosal immune environment. Specifically we showed that topical vaginal treatment with IFN-b could induce innate immune responses to prevent infection.
Advances in HIV Treatment and Prevention
In 2012, working with the Barouch lab we demonstrated that vaccines and microbicides could be used together to provide reinforced protection to rhesus macaques. In other microbicide studies, we tested various microbicide ring and gel formulations that confer sustained protection against SHIV.
Novel HIV treatment and cure strategies
Currently we have multiple novel vaccine and treatment studies in progress designed to reduce or eliminate persistent viral reservoirs in SIV-infected macaques, and preserve or improve the immunologic responses to HIV infection. We are testing host virus-specific tailored vaccines, novel mediators of inflammation, and novel methods of HIV prevention using NHP models of mucosal transmission.
HIV Vaccine Development
Prospects for an effective AIDS vaccine could be enhanced if relevant models for protection and control can be developed that enable robust immunological correlates of protection. In pigtailed macaques, a mutant of SIVmac239 lacking two amino acids in the cytoplasmic tail of Env, replicates to wild type levels acutely while sparing gut mucosal CD4 T cells and macrophages and, with the onset of host immune responses, is profoundly suppressed chronically. Remarkably, delta GY (dGY) vaccination induces broad protection from heterologous SIV challenges, as well as a pathogenic SHIV encoding an HIV-1 Env. This breadth of protection is unparalleled in other SIV vaccine models.
HIV Immunology and Pathogenesis
Recent studies have focused on microRNAs and epigenetic effects of SIV infection on intestinal epithelial cells, and lamina propria cells. We areinvestigating the molecular pathogenesis of the intestinal barrier damage and mucosal inflammation characteristic of SIV and HIV infection, and have shown that microRNAs and TGF-alpha, which are key players in the control of intestinal immune activation and regulation, are both dysregulated in SIV infection.
We have made substantial progress in assessing the neuropathogenesis of SIV infection and AIDS. Multiple papers have been published on characterizing the type of inflammation in SIV encephalitic lesions, and identified several cellular and soluble inflammatory markers that can predict SIV encephalitis in macaques, that may eventually translate into prognostic indicators of HIV encephalitis.
After helping to establish the rhesus macaque and African green monkey as models of SARS-CoV-2 infection early in the pandemic, researchers at the TNPRC have been heavily involved in evaluating the safety and effectiveness of various COVID-19 vaccines and treatments, including the development of future “second-generation vaccines.” Early COVID-19 pathogenesis studies contributed to our understanding of how the innate immune response may predict disease severity, and ongoing studies into “long-haul COVID” investigate how infection with the virus may lead to long term inflammation and damage to numerous organ systems.
An important previous achievement of the Philipp lab, the C6 test for the serological diagnosis of Lyme disease, continues to increase in notoriety, especially with the recent resurgence of interest in Lyme disease research. Progress in understanding the etiology of Lyme neuroborreliosis was achieved through findings that incriminate inflammation as a cause of glial cell and neuronal apoptosis induced by Borrelia burgdorferi.The persistence of symptoms in Lyme disease patients following antibiotic therapy, and their causes, continues to be a matter of intense controversy. The Ember’s lab demonstrated that despite inability to detect organisms in treated NHP by PCR or culture, xenodiagnosis (feeding ticks on the treated animals) revealed intact spirochetes in the ticks fed on treated, putatively “cured” monkeys. These results demonstrate that B. burgdorferi can withstand antibiotic treatment, administered post-dissemination, in a highly relevant NHP host.
One key discovery wasthat the hypoxia responsive DosR regulon is essential for Mtb persistence in the NHP granuloma via modulation of Th1 responses. DosR is an Mtb transcription factor that is induced by hypoxia and other stress conditions. DosR members down-regulate adaptive immune responses and thus enable Mtb to survive in the hypoxic granuloma. Another significant finding was that mucosal vaccination with attenuated Mtb induces central memory responses and, importantly, protects against pathogenic TB challenge. Vaccination with delta-sigH mutant resulted in the accumulation of significantly higher levels of T cells in the lung relative to levels in BCG vaccinated animals and controls. The recruited cells were mostly central memory CD4 and CD8 T cells that were highly proliferative. There were also increases in effector memory T cells of both types. After challenge with a lethal dose of Mtb, unvaccinated and most BCG vaccinated animals succumbed to disease, but the delta-sigH-vaccinated animals were protected.These animals also had significantly lower lung pathology and Mtb burdens in the lung were also significantly lower.
Gluten-sensitive enteropathy (GSE)
Celiac Disease (CD) is an autoimmune disorder marked by gluten sensitivity that affects approximately three million people in the United States, and an identical syndrome has been described in a subset of macaques here at the TNPRC which are now used as a model for the disease. We evaluated the efficacy of using oral prolyl endopeptidase (PE) to reduce the inflammatory effects of the residual gluten in lys3a mutant barley grain. PE supplementation of reduced gluten (RG) barley diet induces more complete immunological, histopathological, and clinical remission than RG barley diet alone. This occurred through decrease of inflammatory mediators IFN-γ and TNF secretion by peripheral lymphocytes, as well as decreased plasma anti-gliadin and anti-intestinal tissue transglutaminase (TG2) antibodies, and diminished active caspase production in small intestinal mucosa. Notably this also eliminated clinical diarrhea, which are all indicators that this experimental gluten-free barley diet induced complete remission of the symptoms and pathology.
Simian varicella virus (SVV)
SVV in NHP is a useful model for varicella zoster virus (VZV) since SVV pathogenesis parallels the pathogenesis of VZV in humans. We have used a reactivation model to study reactivated SVV. Reactivation was studied using a variety of complementary approaches includingquantitative PCR, immunohistochemistry, in situanalysis, and confocal assays which revealed SVV antigens in macrophages and dendritic cells from a variety of tissues. The resulting data suggest that macrophages and dendritic cells in lymph nodes serve the role of antigen-presenting cells to activate T cell responses against SVV after reactivation.
Vertical transmission of Zika virus (ZIKV)
A large collaborative group including multiple investigators from the TNPRC and in collaboration with David Watkins at the University of Miami, established a ZIKV model with pregnant rhesus macaques (Macaca mulatta). Inoculation with a primary ZIKV isolate from Rio de Janeiro resulted in acute viremia in 11/12 animals, and virus in the amniotic fluid (AF) in 4 of 12 infected macaques. Two fetuses died in uteroand one newborn was unresponsive at time of delivery. Moreover, in one of these, ZIKV was present at high levels at the time of fetal demise. Viral sequences from the AF were identical to the virus inoculated, the dam’s replicating virus and the original human isolate. These data demonstrate that ZIKV causes fetal demise in NHPs without any mutation or confounding co-factors, fulfilling Koch’s third postulate, and Shepard’s fifth criterion. The model is useful for evaluation of strategies for abrogating ZIKV infection and for studying the facets of virus-induced maternal and fetal pathology.
Vaccines and treatment strategies against air-borne toxins
Ricin toxin (RT) is a highly lethal toxin and a CDC select agent. RT binds to all mammalian cells and once internalized a single molecule catalytically inactivates all the ribosomes in a cell. We are pursuing alternative strategies for abrogating the toxic effect of ricin. Monoclonal antibodies (mAbs), when administered at the appropriate time, can neutralize the toxin and provide protection. Preliminary pharmacokinetic studies in NHPs for two variants of the mAb have been completed. Both were safely tolerated upon administration, and will soon be tested in challenge studies for evaluation of protection against ricin in vivo.
Aging and the immune response
A resource at the TNPRC is a cohort of aging rhesus macaques supported by the National Institute of Aging (NIA). Work verified that rhesus macaques exhibit immune correlates of aging that are similar to those in humans, such as declining numbers of naïve CD4 T cells and B cells, coincident with increasing numbers of effector memory CD8+ T cells and higher levels of pro-inflammatory cytokines. We also demonstrated that monocytes turnover more quickly, and that this was a predictor of the onset of terminal AIDS in younger adult rhesus macaques. Since HIV-infected individuals given ART exhibit accelerated aging, our future directions are to develop a model of accelerated aging in SIV-infected rhesus macaques and address mechanisms by which macrophages promote inflammation during aging.
Gene Therapy Research
Research was recently initiated to identify novel adeno-associated virus (AAV) vectors that mediate efficient transgene delivery and expression across the entire central nervous system (CNS), which would be significantly beneficial for the treatment of monogenic based neurological disorders. This will be accomplished using directed evolution, which is a powerful and proven method to develop novel AAV vector capsids that have properties distinct from naturally occurring serotypes. This study will capitalize on AAV capsid DNA shuffling directed evolution to develop gene delivery vectors that will function with high efficiency in the CNS of both mice and NHP. The research plan is to generate vectors that exhibit selective tropism for neurons, astrocytes, and/or oligodendrocytes, which would be invaluable gene therapy reagents.
Stem Cell Research
We have initiated studies to determine whether the administration of mesenchymal stem cells (MSCs) from bone marrow or adipose tissue can combat age-associated inflammation or “inflamm-aging”. Macrophages are key regulators of inflammation. The long-term goal for these studies is to capitalize on the innate ability of MSCs to squelch inflammation by infusing them as a strategy to alleviate chronic inflammation in aging individuals, or in those experiencing accelerated aging (e.g. people with HIV infection), by modulating the biology of macrophages