Immunological and virological markers in individuals progressing from seroconversion to AIDS

Lack of correlation between phenotype activation markers of CD8 lymphocytes and cytotoxic T lymphocyte (CTL) function in HIV-1 infection: evidence for rescue with rIL-2

CTL activity against HIV-1 antigens expressed on HLA-A-matched EBV-transformed B target cells was detected in 33% (6/18) of freshly isolated PBMC (FPBMC) from patients in the early stages of HIV-1 infection (CDCII). No CTL activity was detected in FPMBC in patients with AIDS (CDCIV). However, the presence of CTL activity did not correlate with the expression of CTL activation markers. A dual-color flow cytometric examination revealed that the CD8+ lymphocytes bearing the memory (CD29) and activation (S6F1) surface molecules increased in number as the HIV-1 infection progressed. This functional and phenotypic discrepancy in memory CD8+ lymphocytes suggests that the memory CD8+ lymphocytes have lost cytotoxic function and become "paralyzed" as the HIV disease progresses. Incubation of PBMC of HIV(+) patients with rIL-2 reactivated predominantly HIV-specific CTL. However, rIL-2 stimulation also activated a "polyclonal or polyreactive" cytotoxic function. The reactivation of CTL function is rIL-2 dosage dependent and the amount of rIL-2 required for reactivation is associated with the severity of the disease. HIV antigen specific CTL in HIV(+) patients can be selectively expanded by HIV antigen stimulation in the presence of rIL-2. These results suggest that the in vivo IL-2 deficiency occurring in HIV-1 infection may be responsible in part for the "paralysis" of HIV specific CTL activity. Such activity can be rescued nonspecifically by exogenous rIL-2 stimulation and expanded specifically by HIV-1 antigen stimulation.

Loss of mucosal CD4 lymphocytes is an early feature of HIV infection

T cell subsets in the gut mucosa are distinct populations and their imbalance in HIV has specific implications in infection. Alterations in T cell subsets in duodenal biopsies were investigated in 17 asymptomatic HIV patients, 24 AIDS patients and 10 controls with non-ulcer dyspepsia. Immunohistochemistry and immunofluorescence using MoAbs to CD3, CD4, CD8, CD68, CD45RA, CD45RO and gp120 were performed on frozen sections. In the lamina propria, there was a significant depletion of CD4+ cells at all stages of HIV, but the density of CD8 lamina propria cells was increased. Intraepithelial lymphocytes were decreased in AIDS patients. There was a significant correlation between cellular density and mucosal CD3+ lymphocytes, and between mucosal CD3+ and CD8+ lymphocytes. Although mucosal CD4,CD45RO+ 'memory' cells were decreased, CD8,CD45RO+ 'memory' cells were increased. Mucosal CD4+ lymphocyte depletion occurred early in HIV, and thus their role in mucosal protection against opportunistic infection should be revised. Mucosal CD8+ lymphocytes initially increased, but decreased when CD4 blood counts were depleted, perhaps contributing to loss of host protection against infection. Intraepithelial lymphocyte depletion may also contribute to opportunistic infection.

Possible supplemental mechanisms in the pathogenesis of AIDS

Multiple and diverse mechanisms have been proposed as supplements to the HIV-1 virus in the destruction of CD4+ cells and the pathogenesis of AIDS. But it is now realized that 100 times more CD4+ cells are infected with HIV-1 than was originally thought to be the case, and many antigen-presenting cells are infected as well. In addition to the direct cytopathic effect of the virus, one or a few supplemental mechanisms may well suffice to explain the progressive loss of CD4+ cells, e.g., the considerable variation in the virus and/or the destruction of uninfected CD4+ cells by one immunological mechanism or another. However, it is not yet possible to state confidently which additional mechanism(s) is important. Identification of the nature of this supplemental process has become essential for successful, nonharmful intervention.

Prognostic value of kinetic parameters of HIV isolation from peripheral blood mononuclear cells

To assess the correlations between clinical and biological stages of HIV infection and HIV isolation, peripheral blood mononuclear cells from 389 HIV-infected patients were studied by 30-day cocultures with normal lymphocytes. HIV isolation was successful in 279/389 patients (71.7%). Positive isolation was more frequent in CDC IV cases (82%) than in CDC II and III cases (63.6% and 78.4% respectively). There was a close correlation between culture positivity and serum beta 2-microglobulin, CD4+ cell counts and serum p24 antigen. The day of peak detection of reverse transcriptase activity or peak p24 antigen in coculture supernatants was selected as a coculture kinetic parameter. The day of peak detection of HIV in culture occurred earlier in CDC IV cases than in CDC II and III cases, and was a prognostic factor in AIDS progression at 2 years. These data suggest that in vitro parameters related to both viral burden and replicative capacity of HIV isolates are relevant indicators of disease progression.

Evaluation of prognosis and survival of the HIV-infected patient

HIV disease, once considered an acute disease with a 100% mortality rate but a very short symptomatic stage, has begun to emerge as a preventable, treatable, chronic disease. Interactions between patients, dentists, and physicians are essential to gain the information necessary to provide appropriate dental care for both short-term and long-term survivors. The prognosis and survival time of the dental patient may influence treatment protocols and necessitate modified dental procedures. Certain clinical and laboratory parameters, which may be useful indicators of disease progression, need to be recognized by the dental clinician. These parameters include systemic signs, symptoms, and serologic data as well as intraoral manifestations associated with HIV disease. Although a perfect classification system for progression of HIV disease does not exist, trends among larger cohorts may enable health care providers to estimate the prognosis and survival of HIV-infected patients on an individual basis. This article presents clinical and laboratory parameters that indicate HIV disease progression. Providers who care for HIV-infected patients need to consider these parameters to establish an appropriate and flexible treatment plan based on changes in the patient's medical status.

Programmed death of T cells in HIV-1 infection

In human immunodeficiency virus (HIV) infection, functional defects and deletion of antigen-reactive T cells are more frequent than can be explained by direct viral infection. On culturing, both CD4+ and CD8+ T cells from asymptomatic HIV-infected individuals died as a result of programmed cell death (apoptosis). Apoptosis was enhanced by activation with CD3 antibodies. Programmed cell death, associated with impaired T cell reactivity, may thus be responsible for the deletion of reactive T cells that contributes to HIV-induced immunodeficiency.

Humoral immune responses in human HIV-1 infection clearance of initial burst of virus replication and protection against disease progression

An attempt is made to summarize the evidence that humoral immune responses in natural HIV-1 infection play a role in clearance of the initial burst of replication as well as in protection against rapid disease progression. Therefore, the so-called "asymptomatic carrier state" was defined on the basis of immunological characteristics, such as CD4+ cell number, CD45RA-CD29+ cell number, CD4+ proliferative responses to anti-CD3 mAbs and soluble activation markers, as well as virological characteristics such as the state of the viral genome in the cell, levels of genomic RNA production, antigenemia, viremia and virus phenotype. During natural infection two major classes HIV-1 neutralizing and cell-fusion inhibiting antibodies are elicited. One population directed against mostly continuous epitopes localized in the third variable domain (V3) of the envelope and one against discontinuous epitopes of the envelope. The last population blocks gp120-CD4 attachment, the first does not. The role of each of these populations of functional antibodies, in the clearance of viremia and the maintenance of the asymptomatic carrier state is discussed.

Molecular insights into human immunodeficiency virus type 1 pathogenesis

Infection with human immunodeficiency virus type 1 leads to a persistent but progressive cytopathic process that culminates in the near complete destruction of the CD4+ subset of T cells. The levels of human immunodeficiency virus type 1 replication and virus burden increase throughout the clinical course of disease reflecting a balance between the viral and cellular regulatory influences as well as the ability of the host immune system to eliminate infected T cells. Human immunodeficiency virus type 1 replication is dependent on the state of cellular activation and involves both inducible host cell derived transcription factors and at least three virus-derived gene products. Further study of the mechanism of action of these factors, particularly those encoded by the virus, may facilitate the future development of highly specific and effective therapies for human immunodeficiency virus type 1.