Possible role of natural cytotoxic activity in the pathogenesis of AIDS

Asymptomatic anorectal Chlamydia trachomatis and Neisseria gonorrhoeae infections are associated with systemic CD8+ T-cell activation

BACKGROUND

Oral preexposure prophylaxis (PrEP) has been established as a pivotal strategy in HIV prevention. However, bacterial sexually transmitted infections (STIs), such as Chlamydia trachomatis and Neisseria gonorrhoeae, are also highly prevalent. Although the presence of STI-related mucosal lesions is a known risk factor for HIV acquisition, the potential increase in risk associated with asymptomatic STIs is not completely understood. Recent data demonstrated higher T-cell activation is a risk factor for sexually acquired HIV-1 infection. We examined the effect of asymptomatic C. trachomatis and N. gonorrhoeae anorectal infection on systemic immune activation, potentially increasing the risk of HIV acquisition.

METHODS

We analyzed samples from participants of PrEP Brasil, a demonstration study of daily oral emtricitabine/tenofovir disoproxil fumarate HIV PrEP among healthy MSM, for T-cell activation by flow cytometry. We included 34 asymptomatic participants with anorectal swab for C. trachomatis and/or N. gonorrhoeae infection, whereas negative for other STIs, and 35 controls.

RESULTS

We found a higher frequency of human leukocyte antigen DRCD38 CD8 T cells (1.5 vs. 0.9%, P < 0.005) and with memory phenotype in the group with asymptomatic C. trachomatis and/or N. gonorrhoeae infection. Exhaustion and senescence markers were also significant higher in this group. No difference was observed in the soluble CD14 levels.

CONCLUSION

Our findings suggest asymptomatic anorectal C. trachomatis and/or N. gonorrhoeae increase systemic immune activation, potentially increasing the risk of HIV acquisition. Regular screening and treatment of asymptomatic STIs should be explored as adjuvant tools for HIV prevention.

Kaposi's sarcoma: a result of the interplay among inflammatory cytokines, angiogenic factors and viral agents

Kaposi's sarcoma (KS) is an angioproliferative disease occurring in 4 clinic-epidemiologic forms. Although the AIDS-associated KS (AIDS-KS) is the most aggressive, all forms of KS share the same immunological and histopathological features suggesting common etiological and pathogenic factors. Recent data indicate that at least in early stage KS is not a real sarcoma but an angiohyperplastic-inflammatory lesion mediated by inflammatory cytokines and angiogenic factors, that is triggered or amplified by infection with human herpesvirus-8. In addition, the human immunodeficiency virus type-1 Tat protein appears to be responsible for the higher grade of aggressiveness of AIDS-KS as compared to the other forms of KS. However, given time, reactive KS may progress to a sarcoma as suggested by evidence of monoclonality in late-nodular lesions.

Can we find a solution to the human immunodeficiency virus/acquired immune deficiency syndrome controversy? Is acquired immune deficiency syndrome the consequence of continuous excessive stressing of the body?

The time of re-evaluation of the role of human immunodeficiency viruses in the pathogenesis of acquired immune deficiency syndrome has now come, now that methods are available for the direct detection of human immunodeficiency viruses and for the detection of cellular anti-human immunodeficiency virus immune reactions. It has been shown that human immunodeficiency virus infections are common among anti-human immunodeficiency virus antibody negative high-risk individuals. The disease is brought under control by cellular immune reactions and the anti-human immunodeficiency virus antibody test remains negative. Apart from proof that infection with human immunodeficiency viruses has occurred, a positive result in an anti-human immunodeficiency virus-antibody test is also an indication of an independent immunosuppression state. According to the definition of the Centers of Disease Control classical acquired immune deficiency syndrome is the consequence of infection with human immunodeficiency virus in association with continuous excessive stress, such as observed in the known risk groups. At the center of the pathogenetic process is hypercortisolism-determined damage of T lymphocytes, in which insufficiency of thymus is prominent. For this reason, in our view, there are indications for shifting efforts from the prophylaxis of infection with human immunodeficiency viruses to the prophylaxis of acquired immune deficiency syndrome by reducing stress factors.

Natural killer (NK) cell activity during HIV infection: a decrease in NK activity is observed at the clonal level and is not restored after in vitro long-term culture of NK cells

NK cell activity is impaired in HIV-infected patients. The mechanisms behind the altered NK functions are not clear, and conflicting data concerning NK and antibody-dependent cellular cytotoxicity (ADCC) activity have been reported. In order to investigate whether this impairment is also observed at the clonal level and whether it is related to a defect at the target cell binding and/or the post-binding level, we evaluated highly purified NK cell lines and cloned NK cells obtained from 22 HIV-infected patients at different stages of disease and compared them with normal controls for their ability to: (i) kill K-562 and U-937 cell lines using a 51Cr release assay; (ii) bind and kill K-562 and U-937 cells at the single cell binding level; (iii) release NK cytotoxic factor (NKCF), tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma); (iv) kill anti-IgM preincubated Daudi cell line (ADCC activity). This study with cloned NK cells or NK cell lines from HIV-infected individuals showed: (i) a decrease in their lytic capability against target cell lines; (ii) a low ability to form conjugates with K-562 and U-937 cell lines with respect to controls; (iii) a decreased ability to kill bound target cells; (iv) low levels of released NKCF, TNF-alpha and IFN-gamma after incubation with U-937 cells. Taken together, these findings suggest that the impaired NK cell function during HIV infection is also observed at the clonal level and is related to defects both at the target and post-binding levels. However, the precise mechanisms remain to be determined. The inability to restore normal NK activity after long-term culture in the presence of high levels of recombinant IL-2 is in agreement with the hypothesis of a 'general anergic process' during HIV infection.

Elevated serum levels of soluble tumour necrosis factor receptors (sTNF-R) in patients with HIV infection

Serum levels of the soluble form of tumour necrosis factor receptor type II (p75) (sTNF-R) were determined in HIV-infected individuals and risk groups and were then correlated with the course of infection and prognosis. sTNF-R levels were determined by an ELISA with MoAbs and polyclonal antibodies to urine-derived sTNF-R proteins. The mean +/- s.e. levels of sTNF-R in the sera of 49 HIV+ male homosexuals, 34 HIV- male homosexuals and 44 matched controls were 6.1 +/- 0.3 ng/ml, 4.4 +/- 0.3 ng/ml and 3.4 +/- 0.2 ng/ml, respectively. All these values were significantly different between each of the groups (P less than 0.001-0.05). Sequential studies of sTNF-R revealed higher levels following seroconversion in 5/8 individuals, remained persistently high during the asymptomatic phase of the infection and became even more elevated in some ARC and AIDS patients. At the same time TNF-alpha was undetectable in sera obtained from HIV+ male homosexuals and from healthy controls. This was independent of stage of HIV infection, serum sTNF-R level and type of ELISA kit used. These findings suggest that TNF-alpha/TNF-R system is turned on before and during HIV infection and raise the possibility that sTNF-R, the natural inhibitor of TNF, may be of importance in determining the course and probably prognosis of the disease.

Tumor necrosis factor-alpha and anorexia--cause or effect?

Tumor necrosis factor-alpha (TNF-alpha) is a principal cytokine that may induce weight loss in malignancies and certain chronic infections. Short-term caloric deprivation has been found to facilitate in vitro TNF-alpha production, while increased spontaneous production of TNF-alpha has been found in patients with anorexia nervosa (AN). In the present work, we studied in vitro TNF-alpha production in other types of chronic undernutrition and the changes in TNF-alpha production during the refeeding of patients with AN. Undernutrition was evaluated by calculating fat body mass (FBM) from skinfold measurements and lean body mass (LBM) by total body potassium (TBK) counting. Spontaneous and induced TNF-alpha production by peripheral blood mononuclear cells (PBMC) was studied in six chronically malnourished patients with no intercurrent infections, seven patients with AN, and 16 age-matched normal healthy subjects. Spontaneous TNF-alpha production was in the normal range in the chronically undernourished subjects (4.3 +/- 1.5 v 5.0 +/- 1.9 U/mL), but significantly increased in the seven patients with AN (221 +/- 327 v 5.0 +/- 1.9 U/mL, P less than .0006). During refeeding of patients with AN, TNF-alpha production decreased to the normal range concomitantly with weight gain. We concluded that chronic undernutrition, in general, is not always associated with increased TNF-alpha production and that it still remains to be determined whether TNF-alpha plays a primary role in the pathogenesis of AN.

Identification of a low-affinity subset of protamine-reactive IgM antibodies present in normal, deficient in AIDS, sera: implications for HIV latency

We demonstrate here that the protamine-reactive IgM antibodies previously shown to be present in normal adult sera include two subsets differing in binding affinity. The principal, high-affinity subset was detected in AIDS and ARC as well as normal sera. The secondary, low-affinity subset, however, was absent or markedly deficient in AIDS or ARC sera. Protamine-reactive IgM antibodies were also detected in normal pediatric sera, suggesting that one subset of that class of antibodies may be "natural," i.e., not antigenically induced. The proportionate titer of the low-affinity protamine-reactive IgM antibodies was determined for HIV-positive males who were asymptomatic or mildly immune deficient at specimen collection. Of those who subsequently remained AIDS free for 18 months to 7 years, more than 90% had titers in the range established for the normal sera, while of those diagnosed with AIDS or ARC within 12 months, more than 80% had titers below the normal range. We propose that the low-affinity subset of adult sera corresponds to the natural antibodies of pediatric sera and that a relationship of those natural antibodies to resistance to progression of HIV pathogenesis is suggested.

Cytotoxic events taking place in the lung of patients with HIV-1 infection. Evidence of an intrinsic defect of the major histocompatibility complex-unrestricted killing partially restored by the incubation with rIL-2

To characterize the cytotoxic events taking place in the lung of patients with HIV-1 infection, we studied the cells recovered from the bronchoalveolar lavage (BAL) of nine patients with AIDS, seven patients with AIDS-related complex, and two patients with lymphadenopathy. Phenotypic analysis was coupled to a series of functional evaluations of nonspecific cytotoxic abilities performed on lung effectors, including their property to bind K-562 targets, to release natural killer cytotoxic factor (NKCF), and to become cytotoxic following in vitro activation with rIL-2. Our results demonstrated that lung cells bearing the NK-related CD16, CD56, and CD57 antigens were quantitatively increased, irrespective of the disease stage. The majority of the cells also coexpressed the CD3 molecule and the alpha/beta T cell receptor (TCR), notably the phenotype characterizing MHC-unrestricted cytotoxic T cells. From a functional point of view, a severe impairment of the spontaneous cytotoxic ability was demonstrated in most patients. Evaluation at the single cell level showed a normal percentage of the effector/target conjugates formed by HIV-1 lymphocytes. The release of NKCF was undetectable in patients with AIDS even following lectin stimulation, whereas BAL cells from patients with earlier infection produced and/or could be triggered to release discrete amounts of NKCF by incubation with PHA. Studies designed to activate lung cytotoxic cells with rIL-2 showed that in most patients the stimulation of effector cells with rIL-2 enhanced the spontaneous killing and elicited a lymphokine-activated killer (LAK) phenomenon.(ABSTRACT TRUNCATED AT 250 WORDS)

T activation marker evaluation in ARC patients treated with AZT. Comparison with CD4+ lymphocyte count in non-progressors and progressors towards AIDS

Reductions in the percentage and absolute number of CD4+ lymphocytes, as well as abnormally high levels of activated peripheral T lymphocytes (CD3+ HLA-DR+ phenotype) and an increased proportion of CD8+ cells coexpressing the CD57 surface antigen (involved in natural killer activity) have been reported in HIV infection and associated with disease progression. We prospectively measured these subsets of lymphocytes in 34 patients with advanced AIDS-related complex (ARC) treated with azidothymidine (AZT). Peripheral blood lymphocyte phenotyping was performed before treatment, then at weeks 12 and 24. A striking fall in the proportion of activated T lymphocytes from baseline was observed (P less than 0.001) at week 24. In contrast, the percentage of CD4+ cells showed a slight and transient rise at week 12 (P less than 0.05). No modification in levels of CD8+ or CD8+ CD57+ cells was detected during the study. Of the 34 patients, 11 developed AIDS, and 23 remained AIDS-free during 51 weeks of follow-up. Similar patterns of change in CD4+ and HLA-DR+ CD3+ lymphocytes were found in the AIDS progressors and nonprogressors. Likewise, HIV p24 antigenaemia showed parallel decreases in both groups of patients. Although changes in CD4+ cells, p24 antigenaemia and HLA-DR-reactive T lymphocytes were not predictive of clinical outcome, large differences existed between the two groups prior to the initiation of therapy. The short-term onset of AIDS was associated with lower CD4+ cell numbers, higher levels of serum p24 antigen and a greater proportion of activated T lymphocytes. Our results suggest that the possible interest of T lymphocyte activation markers, in conjunction with conventional phenotyping, should be investigated further.

The effect of different nutritional states on cell-mediated cytotoxicity

We have studied the effect of acute short-term starvation (in 9 patients) and of prolonged caloric deprivation (in 10 patients with anorexia nervosa), on cell-mediated cytotoxicity (CMC). CMC became severely depressed after six days on a very low caloric diet (1.2 +/- 1.4 vs. 7.0 +/- 2.9 lytic units/10(6) cells; P less than 0.01). CMC was also low in our patients with anorexia nervosa compared to a matched control group (3.3 +/- 1.7 vs. 10.0 +/- 3.0 lytic units/10(6) cells; P less than 0.01) and increased in most of the patients studied (five cases) after the first 3-4 weeks of refeeding in correlation with weight gain. Dietary deprivation may lead to a significant impairment in cell-mediated cytotoxicity, which appears to be reversible after refeeding.

Tumour necrosis factor production and cell-mediated immunity in anorexia nervosa

Fourteen patients with anorexia nervosa (AN) were studied for the production of tumour necrosis factor (TNF), the activation of the interferon (IFN) system and cell-mediated cytotoxicity (CMC) and the results were compared with 16 age-matched healthy women. AN patients had significantly increased spontaneous TNF production by peripheral blood mononuclear cells (PBMC) in vitro (16 +/- 5 U/ml versus 4 +/- 3 U/ml in the control group; P less than 0.05), although no TNF was detectable in the plasma from either group. TNF production in vitro, following stimulation of PBMC by phytohaemagglutinin (PHA) or tumour cells, was similar in AN patients and controls; however, lipopolysaccharide (LPS) induced TNF production was found to be lower in AN (P less than 0.1). CMC was significantly lower in AN patients (4 +/- 2 versus 10 +/- 3 in controls, expressed as lytic units/10(6) cells; P less than 0.05), but no difference could be found between AN and controls in IFN activity as reflected by the level of the IFN-induced enzyme 2'-5' oligoadenylate synthetase (2-5A) in PBMC. Beta-endorphins in the plasma were higher in the AN group (P less than 0.05) but these levels could not be correlated to those of IFN, CMC or TNF. Defective CMC and increased TNF production by PBMC in patients with anorexia nervosa may possibly result from the nutritional deficiencies and neuroendocrine abnormalities associated with the disease, and may contribute to the pathophysiology of AN.

Immunological features of human immunodeficiency virus disease

Infection with the human immunodeficiency viruses results in a profound immunosuppression responsible for most of the clinical features of AIDS. The virus devastates the immune system because its main target is the T4 lymphocyte, which is the key component for generating and regulating the immune response. The cellular receptor for HIV, the membrane glycoprotein CD4, is found mainly on the surface of this major subpopulation of T lymphocytes and also on many other cell types such as those of the monocyte/macrophage series. HIV can destroy CD4 cells by direct virus cytotoxicity and indirectly through the host response against HIV-infected cells or gp120-targeted cells. Cells of the macrophage lineage are generally not destroyed but serve as a reservoir of virus. HIV also causes functional impairment in T cells, B cells and monocytes. The virus can exist in latent or chronic form. The mechanisms of cellular destruction, viral persistence and conversion to a productive infection are being studied vigorously. Host factors that may affect clinical outcome and immunological markers that may predict progression of HIV disease are presently delineated. Prolonged serological latency may follow infection with HIV. Protective humoral and cell-mediated immune responses to HIV are either poor or not sustained. Recent results on HIV-specific cytotoxic T lymphocytes are of great interest. These cytotoxic cells, particularly those directed to gp120 targets, probably contribute to cellular damage. A central question regarding immunity to HIV is its beneficial versus deleterious effects, particularly in regard to the eventual development of an AIDS vaccine.