Nodular and neoplastic skin lesions in an aquarium-managed group of Sabana Surinam toads Pipa parva.

Although skin disease is a common cause of morbidity and mortality in amphibians, published reports of integumentary conditions affecting skin-brooding anurans are extremely limited. This case series describes the clinical, macroscopic, and histopathologic features of nodular skin lesions in an aquarium-managed population of Sabana Surinam toads Pipa parva, a fully aquatic, skin-brooding species native to South America. The skin lesions represented an ongoing clinical concern in this group, affecting approximately 10-20% of animals throughout the study period, and were observed exclusively in females, suggesting an association with the females' specialized cutaneous reproductive anatomy. Multiple animals died or were euthanized due to skin lesions, which were histologically complex and encompassed a range of hyperplastic, cystic, and neoplastic changes (with internal metastases in one animal). Cultures and special stains showed evidence of mixed polymicrobial infection, including occasional fungal hyphae and acid-fast organisms, but were predominated by Gram-negative bacteria. Lack of a significant response to various environmental modulations and therapeutic interventions indicates that the pathogenesis of the skin lesions is multifactorial. Additional research into the reproductive physiology and ideal environmental conditions (both social and physical) for this species will likely help identify new strategies for prevention and treatment of skin disease.

SPINAL NEMATODIASIS IN A LINED FLAT-TAIL GECKO (UROPLATUS LINEATUS).

A 5-y-old female lined flat-tail gecko (Uroplatus lineatus) presented for acute onset of lethargy and paraplegia and was subsequently euthanized. Histologic examination of the spinal cord revealed a verminous myelitis comprising moderate, multifocal, necrotizing myelitis with intramedullary adult and larval nematodes. Molecular data and morphology indicate a cosmocercid nematode, most likely of the genus Raillietnema, a diverse taxon reported to parasitize reptiles, amphibians, and teleost fish. To the authors' knowledge this is the first report of spinal nematodiasis in a reptile species, and the first report of spinal parasitism causing hind-limb paraplegia in a reptile.

A RETROSPECTIVE SURVEY OF NEOPLASIA IN MANAGED GIRAFFES (GIRAFFA CAMELOPARDALIS).

Giraffes (Giraffa camelopardalis) are commonly managed in zoos and conservation programs worldwide, but the current understanding of the occurrence and progression of neoplastic disease in this species is limited by the scarcity of published reports. This study collated documented cases of neoplasia on the basis of gross and histologic evaluation of ante- and postmortem samples. In total, 30 giraffes from 22 institutions across the United States were included. Subspecies was not reported in all cases, but those identified included Masai (Giraffa camelopardalis tippelskirchi), Rothschild (Giraffa camelopardalis rothschildi), and reticulated subspecies (Giraffe camelopardalis reticulata). Thirteen animals died natural deaths, 15 were euthanized, and 2 were alive at the time of this article. A total of 38 tumors were reported and classified as 18 different diagnoses, including leiomyoma (7), adenoma (4), luteoma (4), lymphoma (4), pheochromocytoma (3), squamous cell carcinoma (3), adenocarcinoma (2), ameloblastic fibroma (1), carcinomatosis of undetermined cell lineage (1), cavernous hemangioma (1), cystic granulosa cell tumor (1), dysgerminoma (1), fibrosarcoma (1), leukemia (1), lipoma (1), pituitary nerve sheath tumor (1), rhabdomyosarcoma (1), and teratoma (1). Multiple concurrent neoplastic lesions were documented in six cases. Mesenchymal tumors (18) were the majority of neoplasms. The most prevalent location, regardless of tumor type, was the female reproductive tract (14). Twenty-four neoplastic lesions were incidental findings at necropsy, whereas eight neoplasms were considered to be the primary cause of death. The findings reported here identify multiple neoplastic lesions in giraffes and could provide insight to the future management of this species.

Research-Relevant Background Lesions and Conditions in Common Avian and Aquatic Species.

Non-mammalian vertebrates including birds, fish, and amphibians have a long history of contributing to ground-breaking scientific discoveries. Because these species offer several experimental advantages over higher vertebrates and share extensive anatomic and genetic homology with their mammalian counterparts, they remain popular animal models in a variety of fields such as developmental biology, physiology, toxicology, drug discovery, immunology, toxicology, and infectious disease. As with all animal models, familiarity with the anatomy, physiology, and spontaneous diseases of these species is necessary for ensuring animal welfare, as well as accurate interpretation and reporting of study findings. Working with avian and aquatic species can be especially challenging in this respect due to their rich diversity and array of unique adaptations. Here, we provide an overview of the research-relevant anatomic features, non-infectious conditions, and infectious diseases that impact research colonies of birds and aquatic animals, including fish and Xenopus species.

Upregulation of Superoxide Dismutase 2 by Astrocytes in the SIV/Macaque Model of HIV-Associated Neurologic Disease.

HIV-associated neurocognitive disorders (HAND) remain prevalent despite implementation of antiretroviral therapy (ART). Development of HAND is linked to mitochondrial dysfunction and oxidative stress in the brain; therefore, upregulation of antioxidant defenses is critical to curtail neuronal damage. Superoxide dismutase 2 (SOD2) is a mitochondrial antioxidant enzyme essential for maintaining cellular viability. We hypothesized that SOD2 was upregulated during retroviral infection. Using a simian immunodeficiency virus (SIV)-infected macaque model of HIV, quantitative PCR showed elevated SOD2 mRNA in cortical gray ([GM], 7.6-fold for SIV vs uninfected) and white matter ([WM], 77-fold for SIV vs uninfected) during SIV infection. Further, SOD2 immunostaining was enhanced in GM and WM from SIV-infected animals. Double immunofluorescence labeling illustrated that SOD2 primarily colocalized with astrocyte marker glial fibrillary acidic protein (GFAP) in SIV-infected animals. Interestingly, in ART-treated SIV-infected animals, brain SOD2 RNA levels were similar to uninfected animals. Additionally, using principal component analysis in a transcriptomic approach, SOD2 and GFAP expression separated SIV-infected from uninfected brain tissue. Projection of these data into a HIV dataset revealed similar expression changes, thereby validating the clinical relevance. Together, our findings suggest that novel SOD2-enhancing therapies may reduce neuroinflammation in ART-treated HIV-infected patients.

Association of persistent wild-type measles virus RNA with long-term humoral immunity in rhesus macaques.

Recovery from measles results in life-long protective immunity. To understand induction of long-term immunity, rhesus macaques were studied for 6 months after infection with wild-type measles virus (MeV). Infection caused viremia and rash, with clearance of infectious virus by day 14. MeV RNA persisted in PBMCs for 30-90 days and in lymphoid tissue for 6 months most often in B cells but was rarely detected in BM. Antibody with neutralizing activity and binding specificity for MeV nucleocapsid (N), hemagglutinin (H), and fusion proteins appeared with the rash and avidity matured over 3-4 months. Lymph nodes had increasing numbers of MeV-specific antibody-secreting cells (ASCs) and germinal centers with late hyalinization. ASCs appeared in circulation with the rash and continued to appear along with peripheral T follicular helper cells for the study duration. ASCs in lymph nodes and PBMCs produced antibody against both H and N, with more H-specific ASCs in BM. During days 14-21, 20- to 100-fold more total ASCs than MeV-specific ASCs appeared in circulation, suggesting mobilization of preexisting ASCs. Therefore, persistence of MeV RNA in lymphoid tissue was accompanied by continued germinal center formation, ASC production, avidity maturation, and accumulation of H-specific ASCs in BM to sustain neutralizing antibody and protective immunity.

Intraepidermal Nerve Fiber Analysis in Human Patients and Animal Models of Peripheral Neuropathy: A Comparative Review.

Analysis of intraepidermal nerve fibers (IENFs) in skin biopsy samples has become a standard clinical tool for diagnosing peripheral neuropathies in human patients. Compared to sural nerve biopsy, skin biopsy is safer, less invasive, and can be performed repeatedly to facilitate longitudinal assessment. Intraepidermal nerve fiber analysis is also more sensitive than conventional nerve histology or electrophysiological tests for detecting damage to small-diameter sensory nerve fibers. The techniques used for IENF analysis in humans have been adapted for large and small animal models and successfully used in studies of diabetic neuropathy, chemotherapy-induced peripheral neuropathy, HIV-associated sensory neuropathy, among others. Although IENF analysis has yet to become a routine end point in nonclinical safety testing, it has the potential to serve as a highly relevant indicator of sensory nerve fiber status in neurotoxicity studies, as well as development of neuroprotective and neuroregenerative therapies. Recently, there is also interest in the evaluation of IENF via skin biopsy as a biomarker of small fiber neuropathy in the regulatory setting. This article provides an overview of the anatomic and pathophysiologic principles behind IENF analysis, its use as a diagnostic tool in humans, and applications in animal models with focus on comparative methodology and considerations for study design.

Amphibian Renal Disease.

Amphibians are a remarkably diverse group of vertebrates with lifestyles ranging from fully aquatic to entirely terrestrial. Although some aspects of renal anatomy and physiology are similar among all amphibians, species differences in nitrogenous waste production and broad normal variation in plasma osmolality and composition make definitive antemortem diagnosis of renal disease challenging. Treatment is often empirical and aimed at addressing possible underlying infection, reducing abnormal fluid accumulation, and optimizing husbandry practices to support metabolic and fluid homeostasis. This article reviews amphibian renal anatomy and physiology, provides recommendations for diagnostic and therapeutic options, and discusses etiologies of renal disease.

Brain macrophages harbor latent, infectious simian immunodeficiency virus.

: The current review examines the role of brain macrophages, that is perivascular macrophages and microglia, as a potential viral reservoir in antiretroviral therapy (ART) treated, simian immunodeficiency virus (SIV)-infected macaques. The role, if any, of latent viral reservoirs of HIV and SIV in the central nervous system during ART suppression is an unresolved issue. HIV and SIV infect both CD4 lymphocytes and myeloid cells in blood and tissues during acute and chronic infection. HIV spread to the brain occurs during acute infection by the infiltration of activated CD4 lymphocytes and monocytes from blood and is established in both embryonically derived resident microglia and monocyte-derived perivascular macrophages. ART controls viral replication in peripheral blood and cerebrospinal fluid in HIV-infected individuals but does not directly eliminate infected cells in blood, tissues or brain. Latently infected resting CD4 lymphocytes in blood and lymphoid tissues are a well recognized viral reservoir that can rebound once ART is withdrawn. In contrast, central nervous system resident microglia and perivascular macrophages in brain have not been examined as potential reservoirs for HIV during suppressive ART. Macrophages in tissues are long-lived cells that are HIV and SIV infected in tissues such as gut, lung, spleen, lymph node and brain and contribute to ongoing inflammation in tissues. However, their potential role in viral persistence and latency or their potential to rebound in the absence ART has not been examined. It has been shown that measurement of HIV latency by HIV DNA PCR in CD4 lymphocytes overestimates the size of the latent reservoirs of HIV that contribute to rebound that is cells containing the genomes of replicative viruses. Thus, the quantitative viral outgrowth assay has been used as a reliable measure of the number of latent cells that harbor infectious viral DNA and, may constitute a functional latent reservoir. Using quantitative viral outgrowth assays specifically designed to quantitate latently infected CD4 lymphocytes and myeloid cells in an SIV macaque model, we demonstrated that macrophages in brain harbor SIV genomes that reactivate and produce infectious virus in this assay, demonstrating that these cells have the potential to be a reservoir.

Myeloid and CD4 T Cells Comprise the Latent Reservoir in Antiretroviral Therapy-Suppressed SIVmac251-Infected Macaques.

Human immunodeficiency virus (HIV) eradication or long-term suppression in the absence of antiretroviral therapy (ART) requires an understanding of all viral reservoirs that could contribute to viral rebound after ART interruption. CD4 T cells (CD4s) are recognized as the predominant reservoir in HIV type 1 (HIV-1)-infected individuals. However, macrophages are also infected by HIV-1 and simian immunodeficiency virus (SIV) during acute infection and may persist throughout ART, contributing to the size of the latent reservoir. We sought to determine whether tissue macrophages contribute to the SIVmac251 reservoir in suppressed macaques. Using cell-specific quantitative viral outgrowth assays (CD4-QVOA and MΦ-QVOA), we measured functional latent reservoirs in CD4s and macrophages in ART-suppressed SIVmac251-infected macaques. Spleen, lung, and brain in all suppressed animals contained latently infected macrophages, undetectable or low-level SIV RNA, and detectable SIV DNA. Silent viral genomes with potential for reactivation and viral spread were also identified in blood monocytes, although these cells might not be considered reservoirs due to their short life span. Additionally, virus produced in the MΦ-QVOA was capable of infecting healthy activated CD4s. Our results strongly suggest that functional latent reservoirs in CD4s and macrophages can contribute to viral rebound and reestablishment of productive infection after ART interruption. These findings should be considered in the design and implementation of future HIV cure strategies.IMPORTANCE This study provides further evidence that the latent reservoir is comprised of both CD4+ T cells and myeloid cells. The data presented here suggest that CD4+ T cells and macrophages found throughout tissues in the body can contain replication-competent SIV and contribute to rebound of the virus after treatment interruption. Additionally, we have shown that monocytes in blood contain latent virus and, though not considered a reservoir themselves due to their short life span, could contribute to the size of the latent reservoir upon entering the tissue and differentiating into long-lived macrophages. These new insights into the size and location of the SIV reservoir using a model that is heavily studied in the HIV field could have great implications for HIV-infected individuals and should be taken into consideration with the development of future HIV cure strategies.

Histologic Findings in Captive American Horseshoe Crabs (Limulus polyphemus).

Histopathology of 61 captive American horseshoe crabs (HSCs; Limulus polyphemus) is reviewed. HSC organs evaluated histologically included body wall (chitin, epidermis, dermis, and skeletal muscle), hepatopancreas, gut, gonads, book gills, eyes, heart, brain, and coxal gland. In descending order, lesions were most frequently identified in compound eye, body wall, book gills, hepatopancreas, chitinous gut, nonchitinous gut, heart, and brain; lesions were not observed in coxal gland or gonads. Hemocytes (also called amoebocytes) surrounded infectious agents and occluded ulcers. Large hemocyte aggregates had a central eosinophilic coagulum (ie, hemocyte coagulum). Cutaneous ulceration (34/60 cases), branchitis (29/48 cases), and ophthalmitis (17/20 cases) were common lesions and consistently associated with fungi, which were invasive into subjacent tissues, and/or bacteria, which were usually superficial. Fungal culture was performed in 3 cases and isolated Fusarium spp., although fungal morphology varied and multiple fungal species may have been present. Presumptive green algae were associated with ulceration in 1 case with minimal to no inflammation. Presumptive cyanobacteria were identified within a biofilm overlying the gills in 4 of 48 cases and were not invasive. Multifocal, random hepatopancreatitis was identified in 16 of 57 cases, 10 of which were associated with bacteria. Metacercarial cysts were identified in 25 of 61 cases and associated with minimal to no inflammation. Depleted eosinophilic globules in hepatopancreatic interstitial cells were interpreted as decreased nutritional status in 12 of 57 cases.

Infectious Virus Persists in CD4+ T Cells and Macrophages in Antiretroviral Therapy-Suppressed Simian Immunodeficiency Virus-Infected Macaques.

Understanding the cellular and anatomical sites of latent virus that contribute to human immunodeficiency virus (HIV) rebound is essential for eradication. In HIV-positive patients, CD4+ T lymphocytes comprise a well-defined functional latent reservoir, defined as cells containing transcriptionally silent genomes able to produce infectious virus once reactivated. However, the persistence of infectious latent virus in CD4+ T cells in compartments other than blood and lymph nodes is unclear. Macrophages (Mϕ) are infected by HIV/simian immunodeficiency virus (SIV) and are likely to carry latent viral genomes during antiretroviral therapy (ART), contributing to the reservoir. Currently, the gold standard assay used to measure reservoirs containing replication-competent virus is the quantitative viral outgrowth assay (QVOA). Using an SIV-macaque model, the CD4+ T cell and Mϕ functional latent reservoirs were measured in various tissues using cell-specific QVOAs. Our results showed that blood, spleen, and lung in the majority of suppressed animals contain latently infected Mϕs. Surprisingly, the numbers of CD4+ T cells, monocytes, and Mϕs carrying infectious genomes in blood and spleen were at comparable frequencies (∼1 infected cell per million). We also demonstrate that ex vivo viruses produced in the Mϕ QVOA are capable of infecting activated CD4+ T cells. These results strongly suggest that latently infected tissue Mϕs can reestablish productive infection upon treatment interruption. This study provides the first comparison of CD4+ T cell and Mϕ functional reservoirs in a macaque model. It is the first confirmation of the persistence of latent genomes in monocytes in blood and Mϕs in the spleen and lung of SIV-infected ART-suppressed macaques. Our results demonstrate that transcriptionally silent genomes in Mϕs can contribute to viral rebound after ART interruption and should be considered in future HIV cure strategies.IMPORTANCE This study suggests that CD4+ T cells found throughout tissues in the body can contain replication-competent SIV and contribute to rebound of the virus after treatment interruption. In addition, this study demonstrates that macrophages in tissues are another cellular reservoir for SIV and may contribute to viral rebound after treatment interruption. This new insight into the size and location of the SIV reservoir could have great implications for HIV-infected individuals and should be taken into consideration for the development of future HIV cure strategies.

SIV-Induced Immune Activation and Metabolic Alterations in the Dorsal Root Ganglia During Acute Infection.

Human immunodeficiency virus-associated sensory neuropathy (HIV-SN) remains a frequent neurologic complication of HIV infection. Little is known about alterations in the peripheral nervous system during the early stages of HIV, a time when neuroprotective interventions may be most beneficial. We performed Nanostring gene expression analysis on lumbar dorsal root ganglia (DRG) from 6 simian immunodeficiency virus (SIV)-infected pigtailed macaques killed at 7 days post-inoculation and 8 uninfected controls. We found significant upregulation of many genes involved in immune signaling and activation in the DRG. Among genes related to glutamate metabolism, there was significant upregulation of glutamine synthetase (GS), while glutaminase (GLS) was downregulated. Several genes involved in the oxidative stress response also showed significant differential regulation in the DRG of 7d SIV-infected animals, with superoxide dismutase-2 (SOD2) showing the greatest median fold change compared to controls. Novel findings in the DRG were compared to corresponding brain data and further investigated at the protein level by Western blotting and immunohistochemistry. Together with our previous finding of significant epidermal nerve fiber loss at 14 days post-SIV infection, results of this study demonstrate that immune activation and altered cellular metabolism at in the DRG precede and likely contribute to early sensory nerve injury in HIV-SN.

FATAL RANAVIRUS INFECTION IN A GROUP OF ZOO-HOUSED MELLER'S CHAMELEONS (TRIOCEROS MELLERI).

A group of five juvenile Meller's chameleons (Trioceros melleri) experienced 100% mortality over a period of 1 mo due to ranavirus infection. The index case was found dead without premonitory signs. The three subsequent cases presented with nonspecific clinical signs (lethargy, decreased appetite, ocular discharge) and were ultimately euthanatized. The final case died after initially presenting with skin lesions. Postmortem examination revealed thin body condition in all five animals and mild coelomic effusion and petechiae affecting the tongue and kidneys of one animal. Microscopically, all animals had multifocal necrosis of the spleen, liver, and kidney; four of five animals had necrosis of the nasal cavity; and two of five had necrosis of adrenal tissue, bone marrow, and skin. Numerous basophilic intracytoplasmic inclusions were present in the liver of all animals and nasal mucosa of three of the five animals. Consensus polymerase chain reaction for herpesvirus and adenovirus were negative, whereas ranavirus quantitative polymerase chain reaction was positive. Virus isolation followed by whole genome sequencing and Bayesian phylogenetic analysis classified the isolates as a strain of frog virus 3 (FV3) most closely related to an FV3 isolate responsible for a previous outbreak in the zoo's eastern box turtle (Terrapene carolina carolina) group. This case series documents the first known occurrence of ranavirus-associated disease in chameleons and demonstrates the potential for interspecies transmission between chelonian and squamate reptiles.

Characterization of an Unusual Mesenchymal Tumor in the Proventriculus of a Free-ranging Red-tailed Hawk (Buteo jamaicensis).

An adult, female red-tailed hawk (Buteo jamaicensis) was presented for examination after being found unable to fly on a private citizen's property. Further diagnostic testing revealed a vascular, soft tissue mass arising from the serosal surface of the proximal proventriculus. Postmortem histological and immunohistochemical examination of the mass revealed an unusual mesenchymal tumor with features consistent with a leiomyoma or low-grade gastrointestinal stromal tumor.

CAUSES OF MORTALITY IN CAPTIVE PANAMANIAN GOLDEN FROGS ( ATELOPUS ZETEKI) AT THE MARYLAND ZOO IN BALTIMORE, 2001-2013.

The Maryland Zoo in Baltimore is home to the largest captive assurance population of the critically endangered Panamanian golden frog ( Atelopus zeteki). With the ongoing extinction that is occurring worldwide in amphibians, the need for amphibian captive assurance populations is growing, and few mortality reviews on amphibian species exist. Necropsy and histopathologic examination of animals that die in captivity can help identify population-level disease problems, direct research needs in amphibian medicine and husbandry, and improve the success of captive breeding programs. This study reviews postmortem findings from 406 frogs, greater than 1 yr of age, which died in this population from 2001 to 2013. Frogs were categorized by age and sex, and the cause of mortality was determined. Dermatitis associated with filamentous-type fungal organisms was the most common cause of mortality in both age and sex categories and accounted for one-third of frog deaths in this study (36.0%; n = 146 out of 406 frogs). Other major causes of mortality included renal disease, gastrointestinal disease, septicemia, and a previously undescribed myopathy condition associated with a tetany syndrome. Increased mortality of frogs occurred during the breeding season, highlighting the need for further research into methods to minimize mortality during this time.

CLINICAL EFFECT OF HEMOPARASITE INFECTIONS IN SNOWY OWLS ( BUBO SCANDIACUS).

Vector-borne hemoparasites are commonly found in avian species. Plasmodium spp., the causative agent of avian malaria, are intraerythrocytic parasites that can cause signs ranging from subclinical infection to severe acute disease. In raptor species, most hemoparasites are associated with subclinical infection and are generally not treated when seen on blood evaluation. This case series reviews five cases of hemoparasite infection in snowy owls ( Bubo scandiacus). These animals were infected with a variety of hemoparasites, including Plasmodium, Haemoproteus, and Leukocytozoon spp. Death of one of these birds due to hemoparasite burden led to a change in the monitoring for and treatment of subclinical hemoparasitic infections in this species. Three subsequently infected snowy owls have been treated with primaquine and chloroquine. The birds that were treated survived infection, and parasite burdens in peripheral blood diminished. Postulated reasons for increased morbidity and mortality associated with hemoparasitic infections in captive snowy owls, as opposed to other raptor species, include stress, concurrent disease, novel pathogen exposure, and elevated environmental temperatures.

Lymphocyte-Dominant Encephalitis and Meningitis in Simian Immunodeficiency Virus-Infected Macaques Receiving Antiretroviral Therapy.

A retrospective neuropathologic review of 30 SIV-infected pigtailed macaques receiving combination antiretroviral therapy (cART) was conducted. Seventeen animals with lymphocyte-dominant inflammation in the brain and/or meninges that clearly was morphologically distinct from prototypic SIV encephalitis and human immunodeficiency virus encephalitis were identified. Central nervous system (CNS) infiltrates in cART-treated macaques primarily comprised CD20+ B cells and CD3+ T cells with fewer CD68+ macrophages. Inflammation was associated with low levels of SIV RNA in the brain as shown by in situ hybridization, and generally was observed in animals with episodes of cerebrospinal fluid (CSF) viral rebound or sustained plasma and CSF viremia during treatment. Although the lymphocytic CNS inflammation in these macaques shared morphologic characteristics with uncommon immune-mediated neurologic disorders reported in treated HIV patients, including CNS immune reconstitution inflammatory syndrome and neurosymptomatic CSF escape, the high prevalence of CNS lesions in macaques suggests that persistent adaptive immune responses in the CNS also may develop in neuroasymptomatic or mildly impaired HIV patients yet remain unrecognized given the lack of access to CNS tissue for histopathologic evaluation. Continued investigation into the mechanisms and outcomes of CNS inflammation in cART-treated, SIV-infected macaques will advance our understanding of the consequences of residual CNS HIV replication in patients on cART, including the possible contribution of adaptive immune responses to HIV-associated neurocognitive disorders.

An SIV/macaque model targeted to study HIV-associated neurocognitive disorders.

Simian immunodeficiency virus (SIV) infection of pigtailed macaques is a highly representative and well-characterized animal model for HIV neuropathogenesis studies that provides an excellent opportunity to study and develop prognostic markers of HIV-associated neurocognitive disorders (HAND) for HIV-infected individuals. SIV studies can be performed in a controlled setting that enhances reproducibility and offers high-translational value. Similar to observations in HIV-infected patients receiving antiretroviral therapy (ART), ongoing neurodegeneration and inflammation are present in SIV-infected pigtailed macaques treated with suppressive ART. By developing quantitative viral outgrowth assays that measure both CD4+ T cells and macrophages harboring replication competent SIV as well as a highly sensitive mouse-based viral outgrowth assay, we have positioned the SIV/pigtailed macaque model to advance our understanding of latent cellular reservoirs, including potential CNS reservoirs, to promote HIV cure. In addition to contributing to our understanding of the pathogenesis of HAND, the SIV/pigtailed macaque model also provides an excellent opportunity to test innovative approaches to eliminate the latent HIV reservoir in the brain.