Immunopathogenesis of human immunodeficiency virus

Human immunodeficiency virus (HIV) types 1 and 2 infect cells of the immune system and initiate a robust immune response which counteracts the viral spread but also accelerates the destruction of the immune system. Many pathogenic mechanisms have been proposed which include viral gene products, syncytium formation, direct virus killing of cells, apoptosis, autoimmunity, cytokine and chemokine expression, superantigens, virus directed cell-mediated cytolysis, and disruption of the lymphoid architecture. At present, there is no unifying theory or experimental proof of a single or a predominant mechanism for the pathogenesis of the HIV disease. This review is intended to highlight areas of HIV research relevant to the understanding of HIV immunopathogenesis.     

T lymphocytes and their cytokines in human immunodeficiency virus (HIV) infection: implications for associated neoplasias

Infection with the human immunodeficiency virus (HIV) results in gradual immunosuppression due to the loss of CD4+ T cells. In the wake of immune system breakdown, infected individuals may acquire multiple opportunistic infections and develop certain malignancies which ultimately account for the vast majority of deaths in these persons. A limited number of malignancies are directly associated with HIV infection and suggest a common tie between these tumors. Inappropriate immune surveillance resulting in insufficient inhibition of virus replication and inadequate control of the growth of transformed cells may contribute to the development of malignancies in HIV-infected individuals. Alternatively, malignancies in HIV infection may be the consequence of immune dysregulation. Cellular immune responses mediated by antigen-specific cytotoxic T lymphocytes (CTL) are of particular importance for immunologic control of viral infections and substantial information has been gathered about theses cells in HIV infection. The goal of this review is therefore to summarize recent findings regarding the cellular immune response to HIV with a particular focus on cytokines released by HIV-specific CTL.     

Cancer-related neuropathic pain

Infection by the human immunodeficiency virus (HIV) causes depletion of CD4-positive lymphocytes with consequent immunodeficiency. HIV infection also causes, by direct or indirect mechanisms, both reactive and neoplastic changes in lymphoid tissues. In primary infection reactive changes are a direct response to HIV. Later in the course of the disease there are reactive changes in lymph nodes and extranodal lymphoid tissues which are likely to be largely an indirect effect of HIV infection, being a response to opportunistic infection by other organisms. There is also an increased incidence of autoimmune phenomena in HIV-infected subjects which is likely to be consequent, at least in part, on impaired control of the proliferation of self-reactive B-cell clones. A second mechanism of immune damage of blood cells, probably operating in the case of HIV-related immune thrombocytopenic purpura, is that of cellular damage by immune complexes containing antiviral antibodies. Lymphoid neoplasms associated with HIV infection include non-Hodgkin's lymphoma, Hodgkin's disease and, uncommonly, plasma cell dyscrasias. HIV-associated lymphomas have distinct clinicopathological features and generally a poor prognosis. As for reactive lymphoid lesions, induction of neoplasia is likely, in the majority of cases, to be an indirect rather than a direct effect of the virus. The combination of chronic B-cell stimulation and impaired T-cell function is important, and interaction of lymphoid cells with virus-infected stromal cells may also play a role. Infection by oncogenic viruses such as the Epstein-Barr virus and human herpes virus 8 is also aetiologically important. In rare cases of T-cell lymphoma, HIV may be directly oncogenic.     

The importance of immunological markers in the diagnosis of central nervous system infections produced by mycobacteria

More than 40 different oral diseases and conditions have been described in patients infected with human immunodeficiency virus (HIV). The recognition of the oral manifestations of HIV disease is of great significance because they may represent the first signs of the disease and have been shown to be highly predictive markers of severe immune deterioration and disease progression. Although some oral diseases and conditions have a weak association with HIV disease, others are strongly linked with the disorder, and a few are acquired immune deficiency syndrome (AIDS)-defining in nature. The spectrum of oral manifestations of HIV disease is reviewed with emphasis on clinical recognition, diagnosis, and treatment.     

The efficiency of acute infection of CD4+ T cells is markedly enhanced in the setting of antigen-specific immune activation

Human immunodeficiency virus (HIV) disease in sub-Saharan Africa generally differs from that observed in the United States and other developed countries in that the risk of seroconversion after exposure is greater and the rate of disease progression to AIDS and death is faster. One theory that could in part explain this difference is the increased state of immune activation associated with a relatively high rate of parasite infestation and other infections among inhabitants of these regions. Using a model based on the cellular microenvironment of lymphoid organs, the role of exposure to HIV during a state of antigen-specific immune activation was investigated. Dendritic cells and CD4+ T cells are the major cellular components of the paracortical region of lymphoid tissue, the primary site of HIV replication. We analyzed cocultures of HIV-pulsed dendritic cells that had matured in the presence of tetanus toxoid and CD4+ T cells before and after inducing an antigen-specific response by in vivo immunization with tetanus toxoid. During antigen-specific immune activation, 100 times less HIV was needed to initiate a productive infection. These findings provide a model system to further delineate the relationship between immune activation and the propagation of HIV infection and suggest a mechanism for the epidemiologic observations of an increased ease of developing HIV infection and faster progression for HIV disease in geographic areas where immune activation is prevalent.     

Effect of dietary fat on lymphocyte proliferation and metabolism

Dendritic cells (DC) are bone marrow-derived leukocytes that act as powerful stimulators of primary and secondary immune responses. Langerhans cells (LC), which are immature DC in epidermis and genital mucosa, are generally believed to be the initial cells infected with HIV following mucosal exposure to virus. Interestingly, freshly isolated LC express the HIV coreceptor CCR5, but not CXCR4, on their cell surfaces. This expression pattern would theoretically allow only macrophage-tropic [and not T cell (TC)-tropic] HIV to be transmitted across intact mucosal epithelium. In vitro, it is known that HIV infects LC (and other DC) in a CD4- and HIV coreceptor-dependent manner. In addition, HIV can be captured by prominent stellate processes on the surface of LC/DC. HIV-infected DC, as well as DC that have captured HIV, efficiently transmit virus to TC during antigen-specific TC activation. Thus, DC may be involved in HIV plasma viremia increases observed following antigenic exposure, e.g. immunizations, in chronically HIV-infected individuals by (1) activating latently infected TC or (2) activating and transmitting virus to new target TC. In summary, DC most likely play a major role in primary HIV infection by allowing virus to breach mucosal surfaces, and can act during both initial and chronic phases of HIV disease by facilitating infection and depletion of TC.     

The course of preexistent immune abnormalities in HIV negative haemophiliacs treated for two years with a monoclonal purified factor VIII concentrate

The administration of factor VIII concentrates has been associated with immune abnormalities in patients with severe haemophilia A, even in the absence of HIV infection. The effects of a monoclonal purified factor VIII concentrate, Hemofil M (Baxter), on preexistent immune abnormalities were assessed over a 2 year period in 22 HIV negative haemophiliacs. They were treated previously with other concentrates, and received Hemofil T from 1983 to 1988. No HIV infection was demonstrated. No serologic evidence for other viral (re)-infections was seen. A decrease of HLA-DR expression on non-B lymphocytes in the first year (P = 0.026), and a decrease of T4-T8 ratio over the 2 years were found (P = 0.0016). Skin tests were non-contributive. The decrease in HLA-DR expression is suggestive for an improved immune function, possibly due to a reduced content of protein or virus in this concentrate.     

Optic neuropathy resembling normal-pressure glaucoma in a teenager with congenital macrodiscs

We report a unique case of a renal transplant patient with a long-term nonprogressive human immunodeficiency virus type-1 (HIV-1) infection and who is asymptomatic despite sustained immunosuppression. Renal function is normal, and HIV infection was probably acquired through blood transfusion before the transplant. Nonprogression may be due either to an effective immune control of HIV replication or to particular genetic aspects of the virus. Several virological investigations were carried out to verify if she is infected with an attenuated virus strain. Results show an unusual combination of high and stable CD4 count, ongoing viral replication and elevated viral loads. Attempts to isolate the virus from plasma were unsuccessful, but isolation was possible from peripheral blood mononuclear cells, and the virus was shown to be non-syncytium-inducing. Sequence analysis of the nef gene revealed no mutation. This exceptional lack of progression of HIV infection under immunosuppressive therapy requires further investigation.     

Accumulation of human immunodeficiency virus-specific cytotoxic T lymphocytes away from the predominant site of virus replication during primary infection

Down-regulation of the initial burst of viremia during primary human immunodeficiency virus (HIV) infection is thought to be mediated predominantly by HIV-specific CD8+ cytotoxic T lymphocytes (CTL). This response is associated with major perturbations in the T cell receptor (TCR) repertoire. To investigate the failure of the cellular immune response to adequately control viral spread and replication and to prevent establishment of HIV infection, changes in the TCR repertoire and in the distribution of virus-specific CTL between blood and lymph node were analyzed in three patients with primary infection. By the combined use of clonotype-specific polymerase chain reaction and analysis of the frequency of in vivo activated HIV-specific CTL, it was shown that HIV-specific CTL clones preferentially accumulated in blood as opposed to lymph node. Accumulation of HIV-specific CTL in blood occurred prior to effective down-regulation of virus replication in both blood and lymph node. These findings should provide new insights into how HIV, and possibly other viruses, elude the immune response of the host during primary infection.     

The tragus as a donor area of cartilage grafts: anatomic study

The American Dental Association (ADA) has developed many resources to address growing concerns regarding HIV (human immunodeficiency virus) issues in dental practice, including continuing education courses, workshops, journal articles, and monographs. In addition, the ADA Council on Dental Practice has established a network for dentists with HIV/AIDS (acquired immune deficiency syndrome). The network has been named PEERS, which stands for Prevention, Education, Ethics, Resources, and Support. This paper provides guidelines for developing programs in each state to address the needs of dentists with HIV/AIDS.     

What is required of an HIV vaccine?

Mounting evidence suggests that the early dissemination of HIV in human beings evokes an immune response that is responsible for containment of the infection during the long symptom-free period. Loss of this immune control coincides with a final escalation of the viraemia and the terminal failure of the immune system. Other studies imply that pre-emptive vaccination of monkeys with attenuated forms of simian immunodeficiency virus (SIV) produces a substantial degree of resistance to superinfection with fully virulent viruses. Here we consider how observations from natural and experimental systems might influence thought as to what is required to produce safe induced immunity against HIV. We concentrate on three questions: what is the nature of the immune response that contains the infection? How does this response fail? How could a vaccine enhance protective immunity so that it exceeds the efficacy of this natural response?     

AIDS, hemophilia, and prevention efforts within a comprehensive care program.

Approximately 92% of persons with severe hemophilia A in the United States have been exposed to the human immunodeficiency virus (HIV), the cause of acquired immune deficiency syndrome (AIDS), from contaminated blood products. This article describes HIV prevention efforts initiated by the federally funded comprehensive hemophilia program. Comprehensive care centers are useful for the delivery and evaluation of educational and preventative efforts. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Testing for HIV infection in time: scientific reasons

The author advocates testing, diagnosis and therapy of HIV infection as soon as possible after contracting the virus and whenever feasible. The arguments are deduced from the results of basic research. The following should be reduced, delayed or inhibited: (1) the viral load in blood plasma and semen; (2) rapid internal propagation of the virus, which is combined with integration of proviruses into cells of unknown life span and compartmentalisation (e.g. the brain may present a sanctuary site); (3) rapid individual formation of quasispecies out of initially homogeneous virus strains of suboptimal fitness, combined with the transition of NSI strains to the more aggressive SI strains and escape from the immune response and therapy; (4) irreversible damage to the immune system; later opportunistic infections; (5) unconscious transmission of possibly drug-resistant virus. Early diagnosis and therapy appear possible in many cases, involving major advantages for individuals and society.     

The virology of AIDS.

In the short time since the cause of AIDS was identified, a considerable amount of knowledge has been gathered. The responsible agent, human immunodeficiency virus (HIV), is a retrovirus that changes the genetic composition of the cells it enters and subsequently destroys. Current knowledge about the virus suggests that it invades cells of the central nervous system, thus contributing to AIDS dementia complex. Vaccines are at present ineffective against the virus, in part because the molecular structure of the protein envelope is so changeable. Psychologists need to understand the virology and immunology of AIDS because components of the virus can alter central nervous system function in ways that have an impact on high-risk behavior. This may be a direct consequence of the virus or an indirect consequence of the production of immune system products in response to the virus. This article discusses the current state of knowledge of HIV and offers ways in which this knowledge may be used by psychologists to formulate a psychosocial and behavioral research agenda and strategies for improved, more effective patient care. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neurophysiological parameters and CD4 lymphocyte count in patients infected by human immunodeficiency virus

INTRODUCTION AND OBJECTIVE: The human immunodeficiency virus (HIV) causes serious, irreversible, progressive deterioration of the immune and nervous systems. The main target cells are the 'helper' T lymphocytes and monocyte-macrophage cells with CD4 molecules on the surface acting as virus receptors. In this study we attempt to find whether the immune state and the nervous system are involved in parallel, or whether, on the contrary, HIV neurotropism is such that it leads to early nerve involvement, out of proportion to that of the immune system. PATIENTS AND METHODS: We studied a total of 66 persons, 30 seronegative and 36 seropositive, with different CD4 lymphocyte counts. In all cases motor and sensory conduction studies were done in the arms and legs, namely auditory, visual and somatosensory evoked potentials and also endogenous potentials (mainly P300). CONCLUSIONS: There are neurophysiological parameters which give pathological figures, even when immunity is maintained (figures of CD4 greater than 500/mm3) especially with regard to the figures for sensitivity of the legs, somatosensory evoked potentials and P300. Moreover, these are increased and others added at the same time as the CD4 count falls as the disease advances.