HIV infection: facts and hypotheses

Mechanisms of autoimmunity and AIDS: prospects for therapeutic intervention

The network theory of autoimmunity is presented with recent experimental data relevant to the understanding of the pathogenesis of AIDS. Schematically, effector T cells specific for self-antigens exist normally, but their activity is modulated and prevented by networks of regulatory T cells. As a result of mimicry between molecular components of microorganisms and self-antigens, autoimmune disease can be triggered by specific foreign pathogens which alter the state of activity of the network from suppression to activation. Conversely, by a procedure known as T-cell vaccination, autologous effector T cells re-injected after in vitro stimulation and attenuation may alter the state of the network from an activation to a suppression. Numerous observations are reviewed that support the concept of autoimmune activity in the destruction of non-infected T4 cells. Such activity is presumed to be triggered by an antigen of viral origin, the most likely, but not the only one, being the envelope protein gp 120. Based on this hypothesis, a T-cell vaccination procedure against effector T cells responsible for autoimmunopathic activity in HIV-seropositive patients is proposed, similar to the one known from experimental study of autoimmunity and presently being tested in human autoimmune diseases. Its purpose would be to prevent T-cell loss and the onset of immunodeficiency disease in HIV-seropositive patients. Apart from its potential therapeutic value, this procedure will have use as a therapeutic test from which insight will be gained about the immunopathogenesis of AIDS.

Can AIDS be prevented by T-cell vaccination?

T-cell vaccination as a specific prophylactic and therapeutic procedure has been shown to be effective in animal models of autoimmune disease. As autoimmunopathogenic components have been implicated in HIV infection, the authors propose a therapeutic test utilizing T-cell vaccination and suggest that AIDS could be prevented by such a procedure.

Derivatives of 4-amino-3,6-disulfonato-1,8-naphthalimide inhibit reverse transcriptase and suppress human and feline immunodeficiency virus expression in cultured cells

We have developed a series of 4-amino-3,6-disulfonato-1,8-naphthalimide (ADSN) derivatives in an attempt to create nontoxic compounds effective against lentivirus infections. The ADSN derivative Lucifer Yellow CH ([N-(hydra zinocarbonyl)amino]-4-amino-3,6-disulfonato-1,8-naphthalimid e) (LYCH) was chosen as a parent compound because of its low toxicity in vivo and in vitro and its tendency to accumulate in monocyte/macrophages, a major reservoir for lentiviruses in vivo. Several ADSN derivatives inhibited reverse transcriptases (RTs) from human immunodeficiency virus type 1 (HIV-1) and feline immunodeficiency virus (FIV). Viral expression in HIV-infected human peripheral blood mononuclear cells was inhibited by noncytotoxic concentrations of two ADSN derivatives, designated A4 (biphenyl-4,4'-dicarboxaldehyde, Lucifer Yellow CH monohydrazone; EC50 = 29 microM after 6 days) and H4 (biphenyl-4,4'-dicarboxaldehyde, Lucifer Yellow CH dihydrazone; EC50 = 5.61 microM). A4 effectively suppressed the expression of FIV in infected Crandall feline kidney fibroblasts (CRFK) at 46.2 microM, reducing the RT levels by 97% after 19 days under conditions allowing direct cell-to-cell transmission of the virus. The viability of drug-treated FIV-infected CRFK cells increased significantly in the presence of A4 relative to the viability of untreated virus-infected cells. In contrast to A4 and H4, LYCH (which lacks the appended aromatic rings characteristic of A4 and H4) had no inhibitory effects on either virus and did not inhibit RT ex vivo. However, flow cytometry studies showed that both A4 and LYCH accumulate in two cell types that can support lentiviral infections: U937 human monocytic leukemic cells that have been induced to differentiate by using tetradecanoyl phorbol acetate, and CRFK cells.

Regulation of cellular trans-activating activities in two different promonocytic leukemia cell lines

Trans-activating activities of certain cellular promoter/enhancer genes may reflect the underlying mechanism for cellular differentiation. We have used two promonocytic leukemia cell lines, U937 and HL-CZ, which differ in their differentiation antigen expression. While both cell lines express CD15 antigen, only the former expresses both CD4 and CD10 antigens. These phenotypes suggest that these two cell lines appear to be arrested at different stages of differentiation. Some regions of the long terminal repeat (LTR) of human immunodeficiency virus-1 (HIV-1) contain nucleotide sequences which bind cellular trans-activating factors such as NF-kappa B and Sp1. These sequences are also present in cellular regulatory gene sequences. The cell lines have been transfected by electroporation with a nested series of deletion mutants containing different lengths of the promoter/enhancer region for HIV-LTR. The promoter/enhancer region has been linked to a 'reporter' chloramphenicol acetyl transferase (CAT) gene. We have found that promoter/enhancer trans-activation is markedly enhanced by treating transfected cells with 12-O-tetradecanoylphorbol-13-acetate (TPA), while similar treatment with tumor necrosis factor-alpha (TNF alpha) slightly enhanced activation. U937 cells always showed much greater transactivating activities than did HL-CZ cells. Deletion of a negative regulatory element (NRE) from the LTR resulted in an enhanced transactivation, while deletions affecting NF-kappa B and/or Sp1 binding sites markedly reduced transactivation. Deletion of both NRE and NRF, a second negative regulatory factor binding site, from the LTR restored the transactivation. However, in the presence of TPA, deletion of NRE sequence without concomitant deletion of the downstream NRF binding sequence was sufficient for recovering transactivation. Since these two cell lines have shown subtle differences in these responses, it may be speculated that monocytes at different stages of differentiation may respond in different ways, qualitatively and/or quantitatively, to signal transduction factors involved in the transactivation of cellular genes.

N-Acetyl-beta-D-glucosaminyl-binding properties of the envelope glycoprotein of human immunodeficiency virus type 1

The effect of carbohydrate structures on the adsorption of HIV-1 or of recombinant envelope glycoprotein gp 160 (rgp 160) to cells of the CEM line was investigated with an indirect immunofluorescence assay using gp 120-specific mouse monoclonal antibodies (mAbs) directed to envelope gp 120. The beta-D-galactosyl, alpha-D-mannosyl, beta-D-glucosyl, N-acetyl-beta-D-glucosaminyl, sialosyl, and L-fucosyl derivatives tested had no effect on this binding. However, preincubation of HIV-1 (or rgp 160) with the neoglycoprotein, beta-D-GlcNAc47-BSA, specifically inhibited the labeling, by some of the mAb used, of HIV-1 (or rgp 160) bound at the cell membrane. This inhibition occurred only with mAbs that were specific for the immunodominant "neutralizing" third variable region (V3) of gp 120. Competition for the binding to rgp 160 between beta-D-GlcNAc47-BSA and mAb was further demonstrated by use of affinity matrices substituted with one of the relevant mAb (110-4), or with beta-D-GlcNAc47-BSA. Besides beta-D-GlcNAc47-BSA-Sepharose, rgp 160 also bound with low affinity, but high specificity, to two other N-acetyl-beta-D-glucosaminyl affinity matrices, beta-D-GlcNAc-divinylsulfone-agarose and asialoagalactothyroglobulin-agarose. Conversely, beta-D-[125I]GlcNAc47-BSA bound specifically to gp 160-Sepharose. These results indicated that rgp 160 behaves as a N-acetyl-beta-D-glucosaminyl-binding protein for GlcNAc residues presented at high density on a carrier, the carbohydrate-binding site of which is close to, or located on the V3 region of gp 120.

Detection of human immunodeficiency virus type 1 genomic RNA in plasma samples by reverse-transcription polymerase chain reaction

An application of the polymerase chain reaction (PCR) to the direct detection of human immunodeficiency virus type 1 (HIV-1) viremia is described. The amplification of specific HIV-1 sequences of gag and env viral genes was carried out after the reverse-transcription of plasma samples (plasma RT-PCR) from seropositive subjects. The assay is faster and cheaper than detection of specific HIV-1 transcripts from peripheral blood mononuclear cells by RT-PCR. The data suggest that HIV-1 viremia is detectable by plasma RT-PCR in a large proportion of seropositive individuals.

The endocytic pathway for human immunodeficiency virus infection

We have presented data supporting the view that HIV infection of T cells and monocytes proceeds via receptor-mediated endocytosis. Biochemical analysis of the pathway for internalization of 32P-labeled HIV revealed the presence of intact, intercellular virions and provided evidence for subsequent uncoating of these particles and release of viral RNA to the cytoplasm. Electron microscopy demonstrated virions within vesicles and documented fusion between viral and endosomal membranes. Others have provided evidence supporting the notion that endocytosis is not required for HIV infection. In consequence of this apparent paradox, it has been suggested that both mechanisms, i.e. direct fusion to the plasma membrane and endocytosis, are functional pathways for HIV entry. I do not favor this position. Examination of the biology of CD4, its role in lymphocyte activation, and its function as the receptor for HIV imply a more active role for this molecule in virus infection than simply as a transient anchor for fusion events. The principal experiment of concern is the report by Maddon, et al., that human CD4- expressing murine cell lines remain resistant to infection by VSV pseudotypes bearing the HIV envelope glycoprotein. This paper and a subsequent review of HIV entry by Marsh and Dalgleish comment on the possibility that endocytosis of human CD4 may not occur in murine cells hence, the block to infectious entry of these pseudotype virions. Resolution of the mechanism for HIV infection is more than rationalization or semantics. The pathway of endocytosis presents an unique feature of cell biology. Should HIV infection be proven to occur via this mechanism, then appropriate assays for novel classes of antiviral agents could be developed. Other features of the endosomal vesicle, such as the unique composition of its membrane or the possible presence of specific proteolytic activities might play important roles in HIV infection and thus, present new targets for the development of antiviral agents. Indeed, the synthetic liposome AL721 is an effective inhibitor of HIV infection in vitro. This antiviral agent probably acts by decreasing the cholesterol content of the virion envelope. It was shown previously that the envelope is specifically enriched in cholesterol, a property not associated with the plasma membrane but clearly involved in Semliki Forest virus fusion within the endosome.(ABSTRACT TRUNCATED AT 400 WORDS)

In situ immunophenotyping of lymphocytes/macrophages: grading of lymphadenopathy, staging and pathophysiology of HIV infection

Histological changes in lymph nodes in HIV1-related lymphadenopathy were analysed in 106 lymph node biopsies and in lymph nodes of 140 autopsy cases. A classification system of five stages was established on the basis of histological and immunohistochemical studies. The analysis confirmed a close correlation between the progression of HIV1-related disease and our staging system. Although the classification is chiefly based on histological and immunohistochemical changes of the follicles, other frequently seen findings are included. Alterations in the interfollicular tissue, e.g. vascular proliferation and lymphocyte depletion, correspond to an increasing concentration of macrophages within this tissue. In HIV1 infection, the macrophages appear to produce high concentrations of angiogenic factors responsible for the frequent and sometimes extreme lymph node vascularization. Since the vascular proliferation can be subject to regression and sclerosis as seen in autopsy cases, the macrophages may lose the ability to produce large amounts of angiogenic factors in the final stage of the disease.

Infected cells and immune cells in the gastrointestinal tract of AIDS patients. An immunohistochemical study of 127 cases

Human immunodeficiency virus (HIV) proteins were detected by immunohistochemistry in the duodenal and rectal mucosa of 30% of 127 AIDS patients studied. HIV-infected cells were present in the lamina propria in 95% of the positive biopsies. They were immune cells, either isolated lymphocytes and macrophages (1-4 per positive biopsy) or dendritic reticulum cells forming a network in the germinal centres of mucosal lymphoid follicles. HIV proteins were not found in the duodenal epithelium or in the superficial rectal epithelium. In two cases (5% of the positive biopsies), they were found in rectal glands: the HIV-infected cells could be either epithelial cells or immune cells. This study confirms that the gut can be a target organ for HIV and that HIV is mainly carried by gut immune cells. The phenotypic study of lymphoid populations and macrophages in the gut mucosa of AIDS patients showed an inverse CD4/CD8 ratio in the lamina propria, compared with normal controls. This was independent of the presence of HIV proteins and is probably responsible for the appearance of opportunistic infections in the mucosa. An increase in activated macrophages was also noted in the mucosa of AIDS patients.

Thalidomide--a therapy for the immunological consequences of HIV infection?

The beneficial effects of the teratogenic drug thalidomide on a variety of disorders involving the immune system have been established recently. Comparison of symptoms and immunologic abnormalities of such diseases with the acquired immunodeficiency syndrome, as well as experimentally obtained results suggest that thalidomide may be a useful agent suppressing autoaggressive reactions initiated by the human immunodeficiency virus.

Persistent human immunodeficiency virus type 1 infection of monoblastoid cells leads to accumulation of self-integrated viral DNA and to production of defective virions

Cell-free virus preparations from persistently infected monoblastoid cells (HU937) become progressively less infectious during long-term passage. This effect is specific for cell lines derived from U937 and is not observed in persistently infected T-cell lines. Reduced infectivity is correlated with accumulation of unusual, high-molecular-weight, extrachromosomal forms of the human immunodeficiency virus type 1 (HIV-1) DNA. These DNA molecules contain multiple copies of the viral genome, and their structures are highly variable. Of 17 subclones of the HU937 cell line, 15 unique restriction fragment patterns were observed for the HIV-1 viral DNA. Structural analysis of these viral DNA species indicated that they were formed by sequential rounds of long terminal repeat-mediated integration of one circular DNA form into preexisting monomeric or multimeric structures. These viral DNA structures are termed nested self-integrates. Once formed, self-integrates prove to be stable and can be maintained for several months in culture. The unusual structures of HIV-1 DNA in persistently infected monoblastoid cells attest to an alternative to the accepted retrovirus life cycle. The self-integrated viral DNA species reported here may explain some aspects of the mechanism controlling establishment and maintenance of persistent HIV-1 infection in cells of the monocyte/macrophage lineage.

Immunology of AIDS: approaches to understanding the immunopathogenesis of HIV infection

Infection with human immunodeficiency virus (HIV) causes an extensive array of immunologic abnormalities which ultimately lead to severe immunosuppression, opportunistic disease, and death. Many of the immunologic defects can be attributable to the quantitative and qualitative deficiencies of T4 lymphocytes caused by HIV. Other abnormalities may reflect chronic HIV exposure to or infection of other immunologic cells including B cells and monocyte/macrophages. A summary of the potential mechanisms of pathogenesis of HIV infection is shown in fig. 2. One of the most puzzling aspects of infection with HIV is the length and variability of time between initial infection and disease. It appears that activation of latent or chronic, smoldering infection into active disease may be the result of a variety of factors, including heterologous viruses and cytokines, whose common denominator is the ability to induce the production of DNA-binding proteins that interact with the HIV-LTR and induce transcription of virus.

Investigation of immunosuppressive properties of inactivated human immunodeficiency virus and possible neutralization of this effect by some patient sera

Retroviral infections are accompanied by immunosuppression in a variety of species. For feline leukemia virus, the immunosuppression has been ascribed to the transmembrane envelope protein, p15E, which suppresses the proliferative responses of cat, mouse, and human lymphocytes. A similar suppressive effect has been shown for a lysate of human immunodeficiency virus (HIV), strain HTLV-IIIB. Here we determined that detergent-disrupted HTLV-IIIB lystate exerted a strong suppressive effect on PHA-stimulated lymphocytes. Preparations of whole virions, a lysate of a local HIV isolate grown on MP-6 cells, and a commercially obtained UV and psoralene-inactivated lysate were examined and demonstrated to have a similar suppressive effect. The HIV lysate was not directly cytotoxic to lymphocytes and did not contain tumor necrosis factor or lymphotoxin. The HIV lysate specifically suppressed the proliferation of a range of hemopoietic cell lines from man and mouse including three EBV transformed CD4- and IL-2 receptor-negative B-cell lines. The lysate also suppressed the formation of human bone marrow colonies, whereas the lysate had only a slight or no effect on fibroblasts. The suppression of lymphocyte proliferation was not abrogated by addition of IL-2 or IL-1 and the HIV lysate inhibited the expression of IL-2 receptors on suboptimal PHA-stimulated mononuclear cells. The suppressive factor(s) has not been characterized in molecular terms, but suppressive activity was recovered in fractions with a molecular weight of about 67,000 and in both the glycoprotein fraction and in the glycoprotein-depleted fraction of the HIV lysate. Sera from one-third of a small series (N = 13) of individuals with antibodies to HIV seem to be able to neutralize the suppressive properties of HIV lysate in cultures.

Jejunal enteropathy associated with human immunodeficiency virus infection: quantitative histology

Jejunal biopsy specimens from 20 human immunodeficiency virus (HIV) positive male homosexual patients were analysed and compared with those of a control group to determine whether the abnormalities were caused by the virus or by opportunistic infection. The degree of villous atrophy was estimated with a Weibel eyepiece graticule, and this correlated strongly with the degree of crypt hyperplasia, which was assessed by deriving the mean number of enterocytes in the crypts. The density of villous intraepithelial lymphocytes fell largely within the normal range, either when expressed in relation to the number of villous enterocytes or in relation to the length of muscularis mucosae. Villous enterocytes showed mild non-specific abnormalities. Pathogens were sought in biopsy sections and in faeces. Crypt hyperplastic villous atrophy occurred at all clinical stages of HIV disease and in the absence of detectable enteropathogens. An analogy was drawn between HIV enteropathy and the small bowel changes seen in experimental graft-versus-host disease. It is suggested that the pathogenesis of villous atrophy is similar in the two states, the damage to the jejunal mucosa in HIV enteropathy being inflicted by an immune reaction mounted in the lamina propria against cells infected with HIV.

Autoantibodies to brain endothelial cells in the sera of patients with human T-lymphotropic virus type I associated myelopathy and other demyelinating disorders

We examined the sera of 21 cases of human T-lymphotropic virus type I (HTLV-1)-associated myelopathy (HAM), 30 cases of neuro-Behçet (N-B) syndrome, and 36 cases of multiple sclerosis (MS) for the presence of autoantibodies to brain endothelial cells by enzyme-linked immunosorbent assay (ELISA) using cultured brain endothelial cells. The concentrations of immunoglobulin G (IgG) which bound to brain endothelial cells were significantly increased in the sera of patients with HAM before (P less than 0.001) and after (P less than 0.01) blocking Fc receptors compared to those of controls. The levels of IgG binding to brain endothelial cells were also significantly increased in the sera of patients with N-B syndrome (P less than 0.01), and MS (P less than 0.001) especially those in an exacerbation compared to those of controls regardless of blocking Fc receptors. These results suggest that IgG binding to brain endothelial cells may be mediated via an immunologically specific antigen-antibody interaction as a result of the blood-brain barrier (BBB) damage in cases of HAM, N-B syndrome and MS.

Independent clinical significance of HIV antigen determination and CD4 counts in anti-HIV positive patients

HIV antigenemia was found in 52/243 HIV antibody positive individuals attending 2 AIDS-screening clinics, giving a prevalence of 13, 25 and 76% in CDC groups II, III and IV, respectively. No correlation was found to decreased CD4 lymphocyte values in the individual groups. HIV antigen therefore identified a separate subpopulation. For 138 asymptomatic patients followed prospectively both laboratory parameters predicted HIV-related events, the relative risk factor being 4 for low CD4 value and 6 for presence of HIV antigen. Individuals presenting with HIV antigen and decreased CD4 count all developed disease within 18 months, the relative risk factor being 24. Thus the 2 markers, when measured together, effectively separated asymptomatic HIV-infected patients into 1 of 3 risk categories.

Infection with human immunodeficiency virus in the Pittsburgh transplant population. A study of 583 donors and 1043 recipients, 1981-1986

We performed a retrospective serologic survey of 583 organ donors and 1043 transplant recipients for antibodies to human immunodeficiency virus type 1 (HIV-1). Two (0.34%) of the 583 donors and 18 (1.7%) of the 1043 recipients had HIV-1 antibodies by enzyme immunoassay and by Western blot. Two of 5 seropositive recipients tested also had blood cultures positive for HIV-1. Seven (0.7%) of the 1043 transplant recipients had antibodies to HIV-1 before transplantation; 2 of these had hemophilia A, and 5 had previous transfusions. Eleven (1.3%) of 860 recipients followed for 45 days or more seroconverted to HIV-1 a mean of 96 days after transplantation. Likely sources of HIV-1 infection for 3 of these 11 recipients included a seropositive organ donor in 1 patient and high-risk blood donors in 2 patients. A definite source of HIV-1 infection was not found for the other 8 recipients, 3 of whom seroconverted to HIV-1 after institution of blood donor screening for HIV-1 antibodies. Seroconversion to HIV-1 was less common in kidney recipients than in liver, heart, or multiple-organ recipients (P less than 0.02). Nine (50%) of the 18 HIV-1 seropositive transplant recipients died a mean of 6 months after transplant surgery, and 9 (50%) are still alive a mean of 43 months after transplantation. AIDS-like illnesses occurred in 3 of the dead and 1 of the living patients and included pneumocystis pneumonia (3 cases), miliary tuberculosis (1 case), and recurrent cytomegalovirus infection (1 case). These data suggest that the course of HIV-1 infection is not more severe in transplant recipients receiving cyclosporine than in other hosts and that, despite screening of blood and organ donors, a small number of transplant recipients will become infected with HIV-1.

Immunopathogenic mechanisms in human immunodeficiency virus (HIV) infections

Infection with HIV can result in a complex array of immunopathogenic effects. HIV infection involves both a direct quantitative depletion of T4 lymphocytes as well as an indirect qualitative effect on the function of several types of immune effector cells. The combination of T4-cell destruction and functional abnormalities contributes to the broad scope of immunologic aberrations and opportunistic diseases seen in HIV-infected individuals. In addition, HIV infection of monocyte/macrophages may play an important role as a reservoir or sanctuary of infection in the host and contribute to the characteristically long incubation period between HIV infection and disease. The activation of HIV from latent or chronically infected cells in vitro by mitogens, antigens, heterologous viruses, and cytokines represents a potential mechanism whereby HIV infection in individuals progresses from an asymptomatic carrier state to clinical AIDS. The release of virus from activated cells can lead to the spread of the virus to other target cells and result in both a qualitative or quantitative defect in immunocompetent cells and subsequent immunosuppression. It is also clear that HIV infection can result in the modulation of expression of certain cellular genes, thereby potentially compounding immunoregulatory abnormalities. Further knowledge of the complex relation between HIV and its target cells will be essential to our understanding of the myriad of potential pathogenic mechanisms of HIV infection and may lead to ways of interrupting the progression of HIV-induced disease.

A review of peripheral tuberculous arthritis

There is a clear difference between TB infection and TB. Transition from the former to the latter involves host factors and perhaps environmental elements. Currently, more individuals with immunosuppressive situations caused by aging, debilitating diseases, immunosuppressive therapies, and HIV-III infection are predisposed to secondary forms of TB. Different patterns of clinical presentation, at variance with those previously described, could result from these changes in the host. PTBA is a good example. In the present review of 52 patients, we found that patient age is rising, as has been reported in other western countries. We also found that oligoarthritis and involvement of non-weight-bearing joints is becoming more common. From the diagnostic point of view, histological studies and cultures of synovial tissue remain the most reliable tests. Awareness of these factors, recognition of changing patterns, proper use of diagnostic procedures, and early treatment should improve the outcome of patients.

Thymostimulin treatment in AIDS-related complex

Thirty-four patients with AIDS-related complex (ARC) were treated for 6 months with thymostimulin, a thymic hormone. Clinical and immunological findings after a 1-year follow-up were compared with those in 24 age- and sex-matched controls receiving no immunotherapy. Statistical evaluation after 6 and 12 months showed significant differences in the two groups. The thymostimulin-treated group had higher leukocyte and lymphocyte counts, more positivity in intradermal tests with multiple recall antigens, and less lymphadenopathy and weight loss. The number of OKT3+ and OKT4+ lymphocytes decreased significantly in the control group, but did not change in the thymostimulin-treated patients. Finally, after 18 months of follow-up, no progression to AIDS was seen among the treated subjects, whereas 3 of the controls developed the disease. We conclude that thymostimulin, alone or in combination with antiviral drugs, may be helpful in the management of ARC patients.

The human immunodeficiency virus: infectivity and mechanisms of pathogenesis

Infection with the human immunodeficiency virus (HIV) results in a profound immunosuppression due predominantly to a selective depletion of helper/inducer T lymphocytes that express the receptor for the virus (the CD4 molecule). HIV also has tropism for the brain leading to neuropsychiatric abnormalities. Besides inducing cell death, HIV can interfere with T4 cell function by various mechanisms. The monocyte serves as a reservoir for HIV and is relatively refractory to its cytopathic effects. HIV can exist in a latent or chronic form which can be converted to a productive infection by a variety of inductive signals.

Soluble CD4 molecules neutralize human immunodeficiency virus type 1

Human immunodeficiency virus (HIV) infection can bring about total collapse of the immune system by infecting helper T lymphocytes which express CD4, the molecule which mediates interaction between the cell surface and viral envelope glycoprotein gp120 (refs 3-10). HIV apparently escapes the effects of neutralizing antibodies in vivo by generating new variants which must still interact with CD4 to maintain a cycle of infection. One route to block HIV infection, therefore, could use solubilized CD4 protein to inhibit attachment of the virus to its target cell. We have used recombinant DNA techniques to generate soluble forms of CD4, and show here that these are potent inhibitors of HIV infection in vitro.

Acquired immune deficiency syndrome (AIDS) and autoimmunity--mutually exclusive entities?

Loss of normal immune homeostasis occurs in acquired immune deficiency syndrome (AIDS). We evaluated patients at the University of Cincinnati and New York University Medical Centers for serologic evidence of autoimmune changes. Specifically, tests for antinuclear and organ-specific antibodies by immunofluorescence, antisperm and anti-seminal plasma antibodies, rheumatoid factor by latex and sensitized sheep cell agglutination techniques, anti-polyadenosine (poly A), and single-stranded DNA antibodies were performed in human immunodeficiency virus (HIV) antibody-positive sera. A parallel study of mitogen responsiveness was performed and showed inhibition of response by AIDS and AIDS-related complex (ARC) sera. In spite of evidence of polyclonal B-cell activation, hyperglobulinemia, and the presence of antibodies to many infectious agents, as well as the known cellular immune abnormalities, the patients tested had a striking absence of these autoantibodies. The only major difference noted from normal controls, was a low but significant level of antibody binding to poly A. The autoimmune connective tissue diseases were not observed in this group of patients.

Ultrastructural and immunohistochemical findings in oral hairy leukoplakia

Three cases of HL from the lateral border of the tongue of male homosexual AIDS patients were investigated by thin section electron microscopy. Keratinocytes contained condensed chromatin in their pyknotic nuclei and a few organelles in the oedematous cytoplasm. Chromatin was in close association to the nuclear membrane and showed a punched-out appearance. Particles typical of the herpes virus group were abundant in the upper two thirds of the epithelium in all three cases. Virus particles were seen frequently in the nuclei of the ballooned keratinocytes, but rarely in cells containing Candida albicans. Viral nucleocapsids were observed budding at the inner nuclear membrane, thereby acquiring the prospective viral envelope. Complete, enveloped virions were found in the endoplasmic reticulum and in the extracellular space. These virions were identified immunohistochemically as Epstein-Barr virus (EBV) using two monoclonal antibodies directed against EBV capsid and membrane antigen, respectively. Candida albicans was observed in the stratum corneum and in the upper layer of the stratum spinosum. Special cytoplasmic tubular structures arranged in parallel bundles were found in koilocytotic cells in addition to characteristic membrane structures composed of undulating convoluted membranes. Epithelial basement membranes were always intact.

Replication and cytopathic effects of ovine lentivirus strains in alveolar macrophages correlate with in vivo pathogenicity

Ruminant lentiviruses share genomic sequences and biologic properties with human immunodeficiency viruses. Four ovine lentivirus strains were assessed for cytopathic effects and virus replication. Lentivirus isolate H/24 produced high virus titers and lysis of synovial cells but replicated slowly and caused no fusion of alveolar macrophages. Lentivirus isolates 84/28 and 85/14 produced low virus titers, less syncytia, and limited or no cell lysis in synovial cells and macrophages. In contrast, ovine lentivirus isolate 85/34 produced early peak virus titers and caused rapid fusion and lysis of both macrophages and synovial cells. Ovine lentivirus isolates which were cytopathic for macrophages induced lymphoproliferative disease when inoculated into lambs.

A calf thymus acid lysate improves clinical symptoms and T-cell defects in the early stages of HIV infection: second report

Thymomodulin is a calf thymus acid lysate capable of inducing T lymphocyte maturation. Fifteen patients with HIV infection at different stages according to the Walter Reed classification were treated with 60 mg/day of thymomodulin syrup for more than 50 days. Two WR6B subjects had clinical and immunological parameters unchanged and died, while the patient suffering from Kaposi's sarcoma presented an evident clinical and laboratory improvement with remission of the neoplasia. The other 12 patients ranging from WR2 to WR5B showed an improvement of clinical symptoms after thymomodulin therapy accompanied by the normalization of CD4/CD8 ratio (P less than 0.001). This helpers/suppressors increase was due to a significant increase of CD4 cells (P less than 0.01) and also to a decrease of the CD8 lymphocytes (P less than 0.05). Thymomodulin administration did not cause an enhancement of the urinary levels of neopterin, a marker of T-cell activation.

A histological and immunocytochemical study of lymphoid tissue in rectal biopsies from homosexual men

A histological study of the lymphoid tissue of the rectums of 323 homosexual and 30 heterosexual men (including five intravenous drug users seropositive for human immunodeficiency virus, HIV) was undertaken. Marked lymphoid hyperplasia (germinal centre greater than 680 microns in diameter) was found in 13 men, nine of whom had a sexually transmitted infection of the rectum. Immunocytochemical studies showed that the germinal centres contained B-cells and follicular dendritic cells, surrounded by CD4+ and CD8+ T-cells in a ratio of between 5:1 and 10:1. In HIV-infected men there were decreased numbers of CD4+ cells and increased numbers of CD8+ cells, resulting in a ratio of between 0.8:1 and 2:1. In biopsies from four of seven HIV-infected men the follicular dendritic cell processes appeared shorter and fragmented. The pathogenesis of HIV infection is discussed in the light of these findings.

Delineation of a region of the human immunodeficiency virus type 1 gp120 glycoprotein critical for interaction with the CD4 receptor

The primary event in the infection of cells by HIV is the interaction between the viral envelope glycoprotein, gp120, and its cellular receptor, CD4. A recombinant form of gp120 was found to bind to a recombinant CD4 antigen with high affinity. Two gp120-specific murine monoclonal antibodies were able to block the interaction between gp120 and CD4. The gp120 epitope of one of these antibodies was isolated by immunoaffinity chromatography of acid-cleaved gp120 and shown to be contained within amino acids 397-439. Using in vitro mutagenesis, we have found that deletion of 12 amino acids from this region of gp120 leads to a complete loss of binding. In addition, a single amino acid substitution in this region results in significantly decreased binding, suggesting that sequences within this region are directly involved in the binding of gp120 to the CD4 receptor.