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Despite effective suppressive antiretroviral therapy, central nervous system (CNS) complications related to human immunodeficiency virus (HIV) remain a significant problem for people with HIV (PWH). Numerous studies have contributed data to define the mechanisms underlying HIV-associated CNS pathophysiology, but causality remains elusive, with no effective therapies to prevent, reduce, or reverse HIV-associated CNS complications. Multiple physiological, clinical, cognitive, behavioral, social, and environmental factors contribute to the observed heterogeneity of adverse CNS outcomes among PWH. The National Institute of Mental Health in collaboration with investigators engaged in research related to HIV associated CNS complications organized a series of meetings to review the state of the science and facilitate the development of biologically based measures to identify the phenotypic heterogeneity of CNS outcomes linked to pathophysiology (biotypes). In this article, we summarize the proceedings of these meetings and explore the precision medicine framework to identify critical factors linked to the etiopathogenesis of CNS outcomes in PWH.

Macrophages play a significant role in HIV infection and contribute to pathogenesis of comorbidities as well as establishment of the viral reservoir in people living with HIV. While CD4+ T cells are considered the main targets of HIV infection, infected macrophages resist the cytopathic effects of infection, contributing to the persistent HIV reservoir. Furthermore, activated macrophages drive inflammation and contribute to the development of comorbidities, including HIV-associated CNS dysfunction. Better understanding the role of macrophages in HIV infection, persistence, and comorbidities can lead to development of innovative therapeutic strategies to address HIV-related outcomes in people living with HIV. In October 2021, the National Institute of Mental Health and the Ragon Institute of MGH, MIT, and Harvard conducted a virtual meeting on role of macrophages in HIV infection, pathogenesis, and cure. This review article captures the key highlights from this meeting and provides an overview of interests and activities of various NIH institutes involved in supporting research on macrophages and HIV.

This a summary of a National Institute of Mental Health (NIMH) sponsored symposium that was focused on the role of astrocytes as a reservoir of the human immunodeficiency virus in the brain. The talks were grouped into four themes. The first theme reviewed the evidence for HIV infection of astrocytes and discussed the challenges in the use of traditional methods of immunostaining and in situ hybridization for detection of infected astrocytes. The second theme focused on mechanisms of HIV entry into astrocytes and discussed CD4 independent mechanisms, such as receptor-mediated endocytosis and transmission of HIV by cell-to-cell contact with infected lymphocytes. The third theme focused on epigenetic regulation of HIV latency in astrocytes and other factors, such as cytokines and transcriptional factors regulating HIV replication in astrocytes. The fourth theme focused on therapeutic approaches, such as gene editing to block persistently infected astrocytes. A discussion that followed was focused on major unanswered questions in the field and future directions for research.

On 18 July 2014, the National Institute of Mental Health in collaboration with ViiV Health Care and Boehringer Ingelheim supported a symposium on HIV eradication and what it meant for the brain. The symposium was an affiliated event to the 20th International AIDS Conference. The meeting was held in Melbourne, Australia, and brought together investigators currently working on HIV eradication together with investigators who are working on the neurological complications of HIV. The purpose of the meeting was to bring the two fields of HIV eradication and HIV neurology together to foster dialogue and cross talk to move the eradication field forward in the context of issues relating to the brain as a potential reservoir of HIV. The outcomes of the symposium were that there was substantive but not definitive evidence for the brain as an HIV reservoir that will provide a challenge to HIV eradication. Secondly, the brain as a clinically significant reservoir for HIV is not necessarily present in all patients. Consequently, there is an urgent need for the development of biomarkers to identify and quantify the HIV reservoir in the brain. Lastly, when designing and developing eradication strategies, it is critical that approaches to target the brain reservoir be included.

In the original article the name of author Lena Al-Harthi was misspelled. It is correct here.

In May 2012, the Division of AIDS Research at the National Institute of Mental Health (NIMH) organized the "Global NeuroAIDS Roundtable" in conjunction with the 11th International Symposium on Neurovirology and the 2012 Conference on HIV in the Nervous System. The meeting was held in New York, NY, USA and brought together NIMH-funded investigators who are currently working on projects related to the neurological complications of AIDS (NeuroAIDS) in Africa, Asia, Eastern Europe, and Latin America in order to provide an opportunity to share their recent findings and discuss the challenges encountered within each country. The major goals of the roundtable were to evaluate HIV-associated neurocognitive impairment and determine if it may be directly attributable to distinct HIV subtypes or clades and to discuss the future priorities for global NeuroAIDS research. At the "Global NeuroAIDS Roundtable", presentations of preliminary research indicated that HIV-associated neurocognitive impairment is prevalent in all countries examined regardless of which HIV clade is present in the region. The only clear-cut difference between HIV-1 clades was in relation to subtypes A and D in Uganda. However, a key point that emerged from the discussions was that there is an urgent need to standardize neurocognitive assessment methodologies across the globe before definitive conclusions can be drawn regarding the relationship between HIV clade diversity and neuropathogenesis. Future research directions were also discussed at the roundtable with particular emphasis on the potential of viral and host factor molecular interactions to impact the pathophysiology of HIV-associated neurocognitive disorders (HAND) from a global perspective. © 2013 Journal of NeuroVirology, Inc. (outside the USA).

Despite major advances in HIV-1 treatment, the prevalence of HIV-associated neurocognitive disorders (HAND) remains a problem, particularly as individuals on suppressive treatment continue to live longer. To facilitate discussion on emerging and future directions in HAND research, a meeting was held in Durban, South Africa in March 2015 as part of the Society of Neuroscientists of Africa (SONA) conference. The objective of the meeting was to assess the impact of HIV subtype diversity on HAND and immunological dysfunction. The meeting brought together international leaders in the area of neurological complications of HIV-1 infection with special focus on the African population. Research presentations indicated that HAND was highly prevalent and that inflammatory cytokines and immune-activation played important roles in progression of neurocognitive impairment. Furthermore, children on antiretroviral therapy were also at risk for developing neurocognitive impairment. With respect to the effect of HIV-1 subtype diversity, analyses of HIV-1 clade C infection among South Africans revealed that clade C infection induced cognitive impairment that was independent of the substitution in HIV-1 Trans-Activator of Transcription (Tat; C31S). At the cellular level, a Zambian study showed that clade C infection resulted in reduced brain cell death compared with clade B infection suggesting clade specific variations in mediating brain cell injury. Furthermore, ex vivo Tat protein from clade CRF02_AG, prevalent in West/ Central Africa, exhibited reduced disruption of brain endothelium compared with clade B Tat protein. Discussions shed light on future research directions aimed at understanding biomarkers and disease mechanisms critical for HAND.

CSF HIV escape is a recently recognised phenomenon that suggests that despite suppressive treatment, HIV RNA may be detected in the CNS compartment in some individuals. In rare cases this is associated with clinical neurological disease, while in most cases, neurological consequences are not apparent. Attempts at characterising the biological substrates of CSF escape and further investigating the neurological consequences need to be made to better understand the implications of this condition for the HIV cure agenda as well as for clinical outcomes. The Global CSF HIV-1 Escape Consortium meeting, convened by the US National Institute of Mental Health, was a first step to gather investigators from diverse sites to discuss opportunities for future collaborative work on this emerging issue. To better understand CSF HIV escape and allow cross-site data reconciliation, it will be useful to reach a consensus set of definitions of the distinct forms of CSF escape, without which concerted cross-site efforts are difficult.

Over 8.3 million people living in the Asia Pacific region are human immunodeficiency virus (HIV) positive and up to 40% of these individuals have had prior acquired immunodeficiency syndrome (AIDS) illnesses. Recently endeavors have been made to better characterize the burden of HIV-related neurological disease within the Asia Pacific region and, with this in mind, the NeuroAIDS in Asia and the Pacific Rim workshop was held in Sydney, Australia, as an affiliated event of the 4th IAS Conference on HIV Pathogenesis, Treatment and Prevention. The workshop was supported by the National Institute of Neurological Disorders and Stroke (NINDS) and the National Institute of Mental Health (NIMH) of the United States National Institutes of Health and the Australian Government overseas AID program, AusAID. HIV neurologists, infectious disease physicians, pediatricians, psychiatrists, immunologists, virologists, and researchers from 12 countries of the Asia Pacific region (including Australia), the United States, and the United Kingdom attended the meeting. A broad range of topics were addressed, including common HIV neurological disorders, the lack of diagnostic, management, and research infrastructure, central nervous system (CNS) immune restoration disease, pediatric neuroAIDS, and current clinical and laboratory research projects being undertaken within the Asia Pacific region.

In 1991, the AIDS Task Force of the American Academy of Neurology published nomenclature and research case definitions to guide the diagnosis of neurologic manifestations of HIV-1 infection. Now, 16 years later, the National Institute of Mental Health and the National Institute of Neurological Diseases and Stroke have charged a working group to critically review the adequacy and utility of these definitional criteria and to identify aspects that require updating. This report represents a majority view, and unanimity was not reached on all points. It reviews our collective experience with HIV-associated neurocognitive disorders (HAND), particularly since the advent of highly active antiretroviral treatment, and their definitional criteria; discusses the impact of comorbidities; and suggests inclusion of the term asymptomatic neurocognitive impairment to categorize individuals with subclinical impairment. An algorithm is proposed to assist in standardized diagnostic classification of HAND.

Eradication of HIV-1 and achieving a sterilizing or functional cure has become a priority area in the AIDS field. Large investments have been made by funding agencies, particularly NIH, in understanding the mechanisms of HIV persistence and approaches to target and eradicate latent reservoirs. The majority of the work that is ongoing has focused on studying resting CD4+ T cell reservoirs and developing strategies for reactivation and purging HIV from this cell type. However, it is becoming increasingly clear that other sites of HIV persistence exist including anatomic reservoirs such as the brain and gut. Also, myeloid cells residing in these anatomic compartments may harbor persistent HIV-1 that could potentially be a source of rebounding virus upon cessation of therapy. The brain is unique in terms of its immune privileged status and the presence of the blood-brain barrier which restricts entry of anti-retrovirals. HIV-1 seeds the brain early in infection and may reside in long-lived cells such as microglia and astrocytes and thus serve as a site of viral persistence. At an NIMH-sponsored meeting entitled “Eradication of HIV-CNS Reservoirs—Current and Future Strategies” held in Washington DC in conjunction with the 12th International Symposium on NeuroVirology (October 2013), many of the challenges in targeting brain HIV-1 reservoirs and the need to better understand the mechanisms of establishment of latency in this unique anatomic compartment were discussed. At that meeting, it was felt that the field would greatly benefit by the publication of a special issue of the Journal of NeuroVirology devoted to HIV-1 CNS reservoirs that would address the challenges and current knowledge in this area. This special issue represents work presented by many of the speakers at the NIMH-sponsored symposium. In addition, several other authors have contributed in order to provide a comprehensive review of the state of the field. The articles presented discuss current challenges in targeting CNS reservoirs as well as mechanisms of establishing persistence in CNS-derived cell populations such as microglia, macrophages, and astrocytes. Current approaches to target myeloid reservoirs as well as some novel gene editing strategies that may aid in HIV-1 eradication strategies are also discussed. I have provided below, for the reader of this special issue, a brief summary of each of the papers published in order to capture the flavor of the topic area covered. The summaries are by no means comprehensive but are illustrative of the research areas that these papers represent. An overview of the translational challenges in targeting latent HIV infection and the CNS reservoir problem was highlighted by Dr. David Margolis. Some of the challenges include the need for reliable, validated cell-based and animal model systems to test latency-reversing agents. He cautions that of several potential anatomic reservoirs, the central J. Joseph (*) Division of AIDS Research, National Institute of Mental Health, Room 9G20, MSC 9831 5601 Fishers Lane, Bethesda, MD 20892-9830, USA e-mail: jjeymoha@mail.nih.gov

The regulation of gamma-interferon-induced major histocompatibility complex (MHC) class II antigen expression on mouse cerebral endothelial cells by the neurotropic mouse hepatitis virus (MHV-4, JHM) was studied in vitro. The results presented demonstrate that MHV-4 can selectively block gamma-interferon-induced class II antigen expression on cerebral endothelial cells. The blocking effect of class II expression occurs in a strain-dependent manner, and is limited to virus-susceptible mouse strains. Virus replication is not required to obtain the blocking effect since UV-inactivated MHV-4 produces the same result. MHV-4 blocking of gamma-interferon-induced class II antigen expression is observed at both the cell surface (flow cytometry) and transcriptional level (Northern analysis).

Interleukin-6 (IL-6) induction, as detected by bioassay and Northern analysis, was examined in vitro in endothelial cells or astrocytes derived from BALB/c (susceptible) or SJL (resistant) mice following exposure to mouse hepatitis virus (MHV-4) or UV inactivated MHV-4 (UV-MHV-4). In BALB/c endothelial cells, up to 16-fold more IL-6 (> 640 U/ml) was induced, compared to SJL cells which showed a minimal response (40 U/ml), relative to basal levels (< 20 U/ml). In contrast, both BALB/c and SJL astrocytes showed a substantial IL-6 response to MHV-4 and UV-MHV-4 exposure, although a strain difference persisted. Despite strain and cell specific differences in released IL-6, equivalent levels of IL-6 mRNA were induced in all cell types following exposure to MHV-4 or UV-MHV-4.

In July 2009, the Center for Mental Health Research on AIDS at the National Institute of Mental Health organized and supported the meeting “NeuroAIDS in Africa.” This meeting was held in Cape Town, South Africa, and was affiliated with the 5th IAS Conference on HIV Pathogenesis, Treatment and Prevention. Presentations began with an overview of the epidemiology of HIV in sub-Saharan Africa, the molecular epidemiology of HIV, HIV-associated neurocognitive disorders (HANDs), and HAND treatment. These introductory talks were followed by presentations on HAND research and clinical care in Botswana, Cameroon, Ethiopia, The Gambia, Kenya, Malawi, Nigeria, Senegal, South Africa, Uganda, and Zambia. Topics discussed included best practices for assessing neurocognitive disorders, patterns of central nervous system (CNS) involvement in the region, subtype-associated risk for HAND, pediatric HIV assessments and neurodevelopment, HIV-associated CNS opportunistic infections and immune reconstitution syndrome, the evolving changes in treatment implementation, and various opportunities and strategies for NeuroAIDS research and capacity building in the region.

Brazil has the largest number of HIV cases of any single country in Latin America - over 600,000. Recently, investigators have begun to characterize the extent of neurological morbidity due to HIV in this country. During 2005 and 2006, the U.S. National Institute of Mental Health cosponsored two meetings of experts aimed at summarizing existing knowledge of HIV and its neurological complications in Brazil. Topics addressed ranged from clinical neurobehavioral aspects to molecular biology. Experts attending the meeting considered fruitful directions for future research.

The Neurologic AIDS Research Consortium (NARC) with support from the National Institute of Neurologic Disorders and Stroke (NINDS) organized the first major meeting on the biology of JC virus and progressive multifocal leukoencephalopthy (PML) in Chicago (February 2001). In recognition of the fact that the incidence of PML has increased in the AIDS (acquired immune deficiency syndrome) era, the key goal of this meeting was the integration of current basic and clinical knowledge to facilitate rapid development of therapeutic options. This meeting proved to be enormously successful in updating the basic and clinical scientists on the major issues and challenges of understanding and treating JC virus–induced demyelinating disease. The advent of highly active antiretroviral therapy (HAART) has had significant benefits for AIDS patients due to reduced viral load and increased numbers of CD4 T cells. However, successful treatment of human immunodeficiency virus (HIV) infection is not always associated with an improved outcome for PML patients. Therefore, it is widely believed that an urgent need exists to develop and test additional therapeutic modalities that directly target JC virus. It is this realization that led the National Institute of Mental Health (NIMH), the Office of Rare Diseases (ORD), and the NINDS to convene a second meeting in July 2002 in Portland, Maine, to reassess the current state of basic, clinical, and epidemiologic knowledge in the field. Another important goal of the meeting was

The National Institute of Mental Health in cooperation with the National Institute on Drug Abuse and the National Institute of Neurological Disorders and Stroke organized a meeting on July 24–25, 2008 to develop novel research directions for neuroAIDS research. The deliberations of this meeting are outlined in this brief report. Several critical research areas in neuroAIDS were identified as areas of emphasis. Opportunities for collaborations between large NIH-funded projects were also discussed.

Virus-induced modulation of mouse cerebral endothelial cell class I and class II antigens by the neurotropic coronavirus, MHV-4 (JHM), was examined by flow cytometry. In susceptible BALB/c, H-2Kd was downregulated, while H-2Dd was upregulated following infection by MHV-4. In contrast, H-2K and H-2D antigens were both upregulated in either MHV-4-susceptible B10.S and (BALB/c x SJL) F1, or MHV-4-resistant SJL-derived cerebral endothelial cells following infection with this virus. Class II antigen expression was unchanged following MHV-4 infection. Virus-induced MHC class I modulation is genetically regulated, and may influence virus clearance by class I-dependent CTL.