Lymphocytotoxic antibodies against peripheral blood B and T lymphocytes in homosexuals with AIDS and ARC

Identification of potential antibody markers in HIV-associated dementia

Markers for HIV-associated dementia (HAD) are needed for diagnosis and management. Specific antibodies to brain and immune complexes (IC) in the cerebrospinal fluid (CSF) are potential markers. CSF IC were found in 4 of 4 HAD patients, 2 of 2 AIDS-central nervous system (CNS) lymphoma patients with dementia, 0 of 1 AIDS-CNS lymphoma patient without dementia, 0 of 1 AIDS-CNS toxoplasmosis patient without dementia, and 0 of 10 neurologic disease controls. By blinded immunoblots, antibrain antibodies in serum and CSF were found in 11 of 12 HAD cases and 7 of 19 HIV-1 patients without HAD. All 11 non-HIV-1 controls were negative. These and published data suggest antibrain antibodies and IC may serve as markers of HAD.

Autoimmune markers in HIV-associated dementia

The etiology of HIV-associated dementia (HAD) is still unknown although direct viral effects have not been supported. Although evidence supports a role for products of activated macrophages, other evidence suggested the possibility of associated autoimmune phenomena at least as a marker. In a blinded analysis, non-HIV-infected whole brain material was immunoblotted with samples of serum, and in certain cases cerebrospinal fluid (CSF), from HAD patients and controls. Distinct antibrain antibodies were detected in 11/12 of HIV+ HAD patients, 7/19 of HIV+ patients without HAD, and 0/11 HIV seronegative controls who were either healthy or had other neurologic diseases. Reactivity against control tissue was negative. Though the etiopathogenetic relation of these antibrain antibodies remains to be delineated, the data suggest that they may be a marker of HAD.

Evidence that immunoglobulin specificities of AIDS-related lymphoma are not directed to HIV-related antigens

Chronic B-cell stimulation may be a predisposing event in the early pathogenesis of the acquired immunodeficiency syndrome (AIDS)-related lymphoma (ARL). ARL-derived immunoglobulin (Ig) genes are significantly diversified from germline, suggesting that antigenic stimulation via Ig receptors may occur prior to malignant transformation. We have evaluated 6 ARL-derived antibodies for binding to human immunodeficiency virus (HIV) and cell surface epitopes. Five cases expressed IgM, and 1 case expressed IgG. Expressed V genes were significantly diversified (3%-15%) from known germline V genes. A non-Ig producing mouse myeloma cell line was transfected with expression vectors containing the lymphoma-derived V genes. By enzyme-linked immunosorbent assay and Western blot assay, the lymphoma-derived Ig's showed no reactivity against HIV recombinant proteins. Also, no specific HIV reactivity was observed by flow cytometry with lymphoma-derived Ig's against the T-cell line infected with T-tropic HIV-1 or peripheral blood mononuclear cells infected with M-tropic HIV strains, indicating lack of binding to native HIV epitopes. However, 2 of the lymphoma-derived Ig's (ARL-7 and ARL-14) bound strongly to non–HIV-infected cells of various tissue origins. Thus, these findings suggest that the transformed B cells of AIDS-associated lymphomas may not arise from the pool of anti-HIV specific B cells but, rather, may develop from B cells responding to other antigens, including self-antigens.

Sequential occurrence of IgM, IgM/IgG, and gp120-IgM/IgG complement complexes on CD4+ lymphocytes in relation to CD4+ blood lymphocyte depletion in HIV+ hemophilia patients: results of a 10-year study

The concept of autoimmune mechanisms playing an integral role in the pathogenesis of HIV disease is rapidly gaining ground. In this study, we determined IgM and IgG antibodies, complement fragments and gp120 on the surface of CD4+ lymphocytes using double-fluorescence flow cytometry. Sequential analysis demonstrated an inverse relationship of autoantibodies and CD4+ lymphocyte counts in the peripheral blood. HIV+ patients without autoantibodies (16/104 = 15%) had the highest CD4+ blood cell counts (324 +/- 264/microliters; mean +/- SD). CD4+ counts were successively lower in patients with complement-fixing IgM (243 +/- 240/microliter), complement-fixing IgG and IgM (139 +/- 138/microliter), or gp120-IgM/IgG complement complexes on the surface of CD4+ cells (38 +/- 45/microliter, P = 0.03). Individual patient profiles show that IgM autoantibodies typically are formed early after HIV infection and appear to deplete CD4+ lymphocytes very slowly, whereas complement-fixing IgG autoantibodies are generated at a later stage and deplete CD4+ lymphocytes more efficiently. The presence of both soluble gp120 and complement-fixing autoantibodies on CD4+ lymphocytes is associated with very low CD4+ cell counts and coincides with progression to terminal disease. Early during HIV infection autoantibody production is rather unstable, but it becomes more stable with disease progression and persists in advanced stages of the disease. These data suggest that autoantibody formation against CD4+ lymphocytes is a pathogenic mechanism for CD4+ cell depletion.

Semen alloantigens and lymphocytotoxic antibodies in AIDS and ICL

More than 90% of people with AIDS develop circulating immune complexes (CICs) and lymphocytotoxic antibodies (LCTAs). Animals infected with HIV, however, never display CICs or LCTAs, and remain healthy. Similarly, HIV-infected people who do not develop CICs or LCTAs also do not progress to AIDS. The appearance of CICs and LCTAs is, however, highly prognostic for AIDS and death. Since HIV infection does not, per se, lead to the development of CICs and LCTAs, other causes are likely. One such cause, for which both epidemiologic and experimental evidence exists, is semen. Semen components include sperm, seminal fluid, lymphocytes, and sometimes infectious agents, including HIV, mycoplasmas, and herpes and hepatitis viruses, all of which independently cause immune suppression. Extensive evidence demonstrates sperm (and various viruses) contains many proteins mimicking the CD4 protein of T-helper cells, while HIV, mycoplasmas, and seminal fluid mimic class II MHC proteins of other lymphocytes. We identify a large number of protein sequences that display such mimicry using computer homology searching, and demonstrate experimentally that sperm antibodies specifically precipitate antibodies against class II MHC mimics such as mycoplasmas, which in turn precipitate antibodies to lymphocyte antigens. These data prove that immunologic exposure to sperm and lymphocytes (as may occur in receptive anal intercourse, needle sharing, or blood transfusions) is theoretically capable of initiating lymphocytotoxic autoimmunity. Such autoimmunity may play a significant role in the pathogenesis of AIDS, and will need to be addressed clinically in high risk individuals regardless of HIV status and regardless of the success of anti-HIV prophylaxis and treatment.

The epidemiology and transmission of AIDS: a hypothesis linking behavioural and biological determinants to time, person and place

Epidemiologically, the Acquired Immune Deficiency Syndrome, AIDS, is transmitted and distributed in the USA and Europe almost entirely in well-defined subsets of populations engaging in, or subjected to, the effects of behaviours which carry high risks of genital and systemic infections. The persons predominantly affected are those engaging in promiscuous homosexual and bisexual activity, regular use of addictive drugs, and their sexual and recreational partners. In such persons and in subsets of populations with corresponding life-styles, the risk of AIDS increases by orders of magnitude. Because of continuity of risk behaviour and of associated indicator infections, the incidence of AIDS over 3-5 year periods is predictable to within 10% of actual totals of registered cases in the USA and UK. Secondary transmission of AIDS beyond these groups is minimal or, in many locations, absent. There is no indication of appreciable spread by heterosexual transmission to the general population. The Human Immunodeficiency Virus, HIV, is transmissible to some extent in general populations, and more so among promiscuous persons. It may cause viraemia, lymphadenopathy and latent infection (HIV disease) in anyone. In persons engaging in risk behaviours which themselves alter or suppress immune responses, it can interact with MHC, antibodies to other organisms and to semen, and other allogenic antigens to initiate a programmed death of CD4 lymphocytes and other defensive cells, as in graft-host rejections. This occurs also in haemophiliacs receiving transfusions of blood products, and is more pronounced in persons with reactive HLA haplotypes. The susceptibility of particular subsets of populations to AIDS is thereby largely explained. But these changes occur in the absence of HIV, and so do Kaposi's sarcoma, lymphadenopathies and opportunistic infections which are regarded as main indicators of AIDS. The hypothesis that HIV-1 can do all this by itself and thereby cause AIDS is falsifiable on biological as well as epidemiological grounds. An alternative hypothesis is proposed, linking the incidence of AIDS to the evolution of contemporary risk behaviour in particular communities and locations in the USA, UK and probably in most of Europe. It does not pretend to explain the reported incidence of AIDS in Africa and other developing regions where data are insufficient to provide validation of the pattern of disease and contributory variables. The immediate, practical implication of this alternative hypothesis is that existing programmes for the control of AIDS are wrongly orientated, extremely wasteful of effort and expenditure, and in some respects harmful.

CD4 similarity to proteins of infectious agents in AIDS and their role in autoimmunity

Lymphocytotoxic autoimmunity (LA) is ubiquitous in AIDS. Its causes are unknown. We report that significant amino acid sequence similarities exist between the proteins of infectious organisms associated with AIDS and the CD4 protein of T-helper lymphocytes. These included: HIV, cytomegalovirus (CMV), Epstein-Barr virus (EBV), herpes simplex viruses (HSV), Varicella Zoster virus (VZV), Escherichia coli, Mycobacteria, Mycoplasmas, Plasmodium, and Staphylococcus. It has been reported previously that HIV proteins have significant similarities with human class II MHC (HLA class II) proteins. Since CD4 and HLA class II proteins are chemically complementary, pairs of homologous antigens will also be complementary. It follows that concurrent infections with CD4 and HLA class II-homologous antigens will result in idiotype-antiidiotype antibody pairs that cannot distinguish 'self' from 'nonself', that acts as lymphocytotoxins, and form circulating immune complexes. Thus, combined HIV-CMV, HIV-EBV, HIV-HBV, HIV-mycoplasma, or other appropriate infectious pairs may suffice to trigger LA in AIDS.

CD4+ lymphocyte depletion in HIV-infected patients is associated with gp120-immunoglobulin-complement attachment to CD4+ cells

The mechanism of CD4+ lymphocyte depletion, which is the main immunological feature in HIV-infected patients, is unclear. We investigated whether gp120-immunoglobulin-complement complexes on the surface of CD4+ cells might be involved in the elimination of CD4+ lymphocytes. The results obtained in 63 HIV-infected patients show that gp120 is attached to a variable degree to CD4+ cells. Importantly, the percentage of CD4+gp120+ lymphocytes is inversely associated with CD4+ lymphocyte counts in the peripheral blood (p = 0.0004). CD4+gp120+ blood lymphocytes bind IgM (p = 0.0027) and IgG antibodies (p = 0.0001) and complement (p = 0.0005). These results suggest that immune complex-mediated cell elimination is an important mechanism of CD4+ cell depletion in patients with AIDS.

Differential isotype expression and binding properties of T cell-reactive antibodies in human immunodeficiency virus (HIV) infection

Isotype and binding characteristics of T cell-reactive antilymphocyte antibodies (ALA) were investigated in 287 human immunodeficiency virus (HIV)+ sera from patients with CDC II to IVC clinical disease. Using purified soluble T-lymphoblast (CEM cell line) membranes and an ELISA method, 29 HIV+ sera showed significant reactions with this substrate and a selective expression of IgG-ALA was detected in 7 HIV+ sera. Subsequent microcytotoxicity assays, utilizing peripheral T lymphocytes and CEM cells as targets, demonstrated no significant cytotoxic capability in such sera, whereas 12 of 17 HIV+ serum samples with IgM-ALA ELISA reactivities showed a significant degree of killing in the Terasaki test. Further experiments of saturation of CD4 molecules on CEM extract by OKT4 monoclonal antibody (MoAb) induced a high inhibition of IgG-ALA binding to the T-cell membranes in only two IgG-ALA+ sera (No. 93, CDC III; No. 179, CDC II stage). Conversely, treatment of CEM membrane lysate with Leu3a MoAb, specific for the gp120 reactive domain of the HIV receptor, failed to prevent membrane binding in all seven of the IgG-ALA+ sera. Following the adsorption of serum 93 on a T-cell membrane antigen affinity column, SDS-PAGE analysis demonstrated that the predominant ALA material reacting with T-cell membranes was IgG with no detectable traces of IgM. These data provide evidence that ALA in HIV+ patients may be simultaneously or selectively expressed as IgG and/or IgM with different properties.(ABSTRACT TRUNCATED AT 250 WORDS)

Autoantibodies in HIV-infected hemophilia patients against different epitopes on CD4+ lymphocytes and recombinant CD4

We studied 684 sera obtained from 20 hemophilia patients with AIDS/AIDS-related complex (ARC), 89 asymptomatic HIV+, 76 HIV- hemophilia patients and 151 healthy controls for antibodies against recombinant CD4 (rCD4). Twenty-two percent of AIDS/ARC patients, 10% of asymptomatic HIV+ patients, 17% of HIV-patients, and 1% of healthy controls had anti-rCD4 antibodies. Purified anti-rCD4 antibodies did not react with human CD4+ lymphocytes. This may explain why formation of anti-rCD4 antibodies correlated neither with the occurrence of autoantibodies against CD4+ lymphocytes nor with a decrease in CD4+ cell counts. Antibodies that were eluted from CD4+ lymphocytes after sequential adsorption and elution with separated CD8+ and CD4+ cells reacted with CD4+ lymphocytes of only some healthy individuals, suggesting diversity of CD4 expression.

Human immunodeficiency virus infection induces both polyclonal and virus-specific B cell activation

Peripheral blood lymphocytes (PBL) were obtained from HIV-1-infected patients at different stages of disease. The absolute number of IgM-, IgG-, and IgA-producing lymphocytes per 10(6) PBL was increased 2.8-, 3.4-, and 1.9-fold, respectively, compared with normal controls. 2-17% of IgG-secreting patient cells reacted with the gp160 envelope glycoprotein of HIV-1 (a 737-fold increase over background), while 1-9% reacted with p24 (140-fold over background). In addition to this HIV-specific B cell activation, the number of lymphocytes reactive with nonviral antigens such as DNA, myosin, actin, trinitrophenylated keyhole limpet hemocyanin, and ovalbumin was increased by a mean of 17.9-fold. Evidence suggests that the latter changes reflect an HIV-induced polyclonal B cell activation unrelated to the production of anti-HIV antibodies. For example, the proportion of IgG anti-gp160- and anti-p24-secreting lymphocytes declined in patients with advanced disease, whereas the number of B cells producing antibodies to non-HIV antigens rose. Moreover, CD4 cell count and T4/T8 ratio showed a significant inverse correlation with the degree of polyclonal activation but not with anti-HIV responsiveness. These observations demonstrate that both quantitative and qualitative changes in B cell activation accompany (and may be predictive of) disease progression in HIV-infected individuals.

Surface immunoglobulin-positive T lymphocytes in HIV-1 infection: relationship to CD4+ lymphocyte depletion

T lymphocytes bound to autologous immunoglobulin (surface Ig + T cells) and serum antibodies that bind to allogeneic lymphocytes have been detected in HIV-1-infected individuals, but their significance in the immunopathogenesis of HIV-1 infection is uncertain. We tested peripheral blood from HIV-1-infected individuals to determine if surface Ig+ T cells are specific for HIV-1 infection and are associated with CD4+ lymphocyte depletion. The majority of HIV-1-infected individuals contained substantial numbers of circulating surface Ig+ T cells. The presence of such cells was restricted to seropositive individuals and not related to risk factors associated with the acquisition of HIV-1 infection. Autologous immunoglobulin was detected on both CD4+ and CD8+ cells in all patients tested. Most individuals with surface Ig+ T lymphocytes also had serum anti-T-lymphocyte antibodies. The presence of surface Ig+ T lymphocytes correlated significantly with lower absolute CD4+ lymphocyte counts only in asymptomatic, HIV-1-infected individuals.

Isotype, distribution and target analysis of lymphocyte reactive antibodies in patients with human immunodeficiency virus infection

Anti-lymphocyte (ALA) antibodies were investigated by using both microcytotoxicity and immunofluorescence analyses in 87 subjects with different clinical features of human immunodeficiency virus (HIV) infection. A similar mean percentage of killing in microcytotoxicity assays using heterologous lymphocytes as cellular target was recorded in four groups of patients, including 36 HIV-seropositive asymptomatic subjects, 34 patients with HIV-induced lymphadenopathy syndrome (LAS), 13 with acquired immunodeficiency syndrome (AIDS)-related complex (ARC), and 4 patients with the full-blown AIDS. Conversely, an increasing percentage of ALA-positive subjects paralleled the evolution of the HIV infection. The majority of ALA were IgM isotype with a significant reactivity against T cells. This specificity was indifferently directed to CD3+, CD4+, and CD8+ lymphocytes. In additional experiments employing enzymatic digestion of lymphocyte membrane antigens, we demonstrated that CD4 and CD8 receptors were digested by the pronase, whereas CD3 molecules were highly resistant. Subsequent flow cytometry analyses using these pronase-digested T cells showed that reactivity of ALA for their target was unchanged. Our data suggest that antigenic specificities of ALA in HIV infection are resistant to pronase treatment and are not related to CD4 and CD8 molecules.

Autoantibodies against CD4- and CD8-positive T lymphocytes in HIV-infected hemophilia patients

The presence of IgG, IgM, C3d, or gp120 on the surface of T lymphocytes was analyzed by flow cytometry in blood samples from 73 hemophilia patients and 56 healthy controls. IgG and IgM autoantibodies against CD4+ lymphocytes were found in HIV + patients but not in HIV-patients or healthy controls (p less than 0.001). IgM autoantibodies were more frequent than IgG autoantibodies. Autoantibody formation increased with disease progression. However, within the same disease risk category, patients with autoantibodies were not "more immunologically abnormal' than patients without autoantibodies. HIV + patients who possessed autoantibodies had similar CD4+ and CD8+ lymphocyte counts as HIV + patients without autoantibodies. There was no significant difference in the number of patients with abnormal CD4/CD8 ratios, serum neopterin levels, or in vitro responses to allogeneic stimulator cells or mitogens between autoantibody-positive or -negative patients of the same risk category. Our data suggest that autoantibodies against CD4+ lymphocytes may be helpful as indicators of disease progression, however, their immunopathogenetic role remains unclear.

Rheumatoid factor and Fc signaling: a tale of two Cinderellas

Signaling to lymphocytes depends not only upon the interaction of receptors with specific antigen, but also upon antigen nonspecific receptors which receive input from two classes of molecules, immunologically specific end products and lymphokines. These represent the central elements in the physiologic stimulation of immune responses to both self and foreign antigens. This review is dedicated primarily to describing the function of physiologically active receptors for end product which are central to end product feedback in normal immune responses. The emergence of autoimmunity as a pathologic process resultant from a defective end product signaling mechanism is described.

An AIDS-related cytotoxic autoantibody reacts with a specific antigen on stimulated CD4+ T cells

Patients with the acquired immune deficiency syndrome (AIDS) and AIDS-related conditions are known to have abnormalities of T cell subpopulations, including a decreased helper/inducer (bearing the CD4 antigen) to suppressor/cytotoxic (bearing the CD8 antigen) T cell ratio and decreased absolute numbers of T cells with the CD4+ phenotype. Infection of T cells with a retrovirus, termed human immunodeficiency virus (HIV), is thought to be important in these abnormalities. HIV infection alone does not adequately explain the CD4+ T-cell abnormalities seen in AIDS, however, and the nature of T-cell destruction in this disease remains poorly characterized. Here we describe an AIDS-related serum autoantibody that reacts with an antigen of relative molecular mass 18,000 (Mr 18K) restricted to lectin-stimulated or HIV-infected CD4+ T cells. The antibody also suppresses proliferation of CD4+ T cells in vitro and induces cytotoxicity of these cells in the presence of complement. Its role in the development of AIDS merits attention.

Cellular targets of antilymphocyte antibodies in AIDS and LAS

Many patients with acquired immune deficiency syndrome (AIDS) and lymphadenopathy syndrome (LAS) have serum antilymphocyte antibodies. The targets of these antibodies are neither sex nor HLA directed. There is disagreement about the cell subset at risk. We examined the cellular specificity of antilymphocyte antibodies from AIDS and LAS patients by microcytotoxicity on positively selected lymphocytes, by using double-labeling immunofluorescence, and by using well-characterized continuous cell lines as targets. We find that most AIDS/LAS patients have antibodies to T and B cells, that immunofluorescence is somewhat more sensitive than microcytotoxicity, and that the antibodies are directed to both T4+ and T4- lymphoid cells.