Immune response to human immunodeficiency virus (HIV) in healthcare workers occupationally exposed to HIV-contaminated blood

Exposure to human immunodeficiency virus (HIV) does not necessarily induce infection or seroconversion defined by standard criteria based on enzyme-linked immunosorbent assay (ELISA), Western Blot, or polymerase chain reaction (PCR) techniques, but it can induce HIV-specific cell-mediated immune responses. Healthcare workers (HCWs) occupationally exposed to HIV represent a unique population with low-level exposure to HIV for whom time and type of exposure are specifically recorded. Although the frequency of seroconversion in HCWs occupationally exposed to HIV contaminated body fluids is relatively low, a higher proportion of HIV-exposed HCWs seem to exhibit in vitro cellular responses to HIV envelope peptides. Our findings indicate that parenteral exposure to HIV can induce cell-mediated immune responses in the absence of seroconversion. The significance of these responses is not known, but it is possible that the low incidence of HIV infection after exposure might be due, in part, to a protective cellular immune response to low HIV inocula.

In vitro immunologic and virologic effects of interleukin 15 on peripheral blood mononuclear cells from normal donors and human immunodeficiency virus type 1-infected patients

Interleukin 15 (IL-15) is a cytokine that shares receptor subunits and functional activity, such as T-cell and B-cell stimulation, with IL-2. The effect of IL-2 on immune function and human immunodeficiency virus (HIV) viral load in HIV-infected patients is being actively studied. Thus, we examined how IL-15 compares with IL-2 in several in vitro immunologic and virologic assays in order to explore whether a rationale exists for pursuing initial clinical therapeutic trials with IL-15. The effects of IL-15 on induction of lymphokine-activated killer (LAK) cells, gamma interferon (IFN-gamma) production from HIV-positive peripheral blood mononuclear cells (PBMCs), and HIV production from PBMCs were studied. Induction of LAK cells by IL-15 was found in eight of eight HIV-positive donors. Incubation of PBMCs from some donors with IL-15 (1, 10, 50, and 100 ng/ml) induced production of IFN-gamma. The effect of IL-15 was compared with that of IL-2 on HIV replication in PBMCs from five HIV-positive patients and four HIV-negative donors whose PBMCs were infected in vitro with HIV. Levels of HIV p24 antigen were moderately lower in the presence of 10 ng of IL-15 per ml than with 10 ng of IL-2 per ml, but they were similar for 100 and 500 ng of each cytokine per ml. In summary, IL-15 can induce LAK cell activity in HIV-seropositive patients and can stimulate IFN-gamma production from PBMCs of some donors. IL-15 stimulates levels of HIV production from PBMCs which are similar to or moderately lower than those obtained with IL-2, depending on cytokine concentration.

Effects of substance P on human T cell function and the modulatory role of peptidase inhibitors

Evidence has been presented for a modulatory role of surface peptidases on substance P-mediated immune responses. In this study, we first characterized the effects of substance P and its carboxy- and amino-terminal fragments on human lymphocyte proliferative responses to investigate whether peptidase inhibitors influence the effects of the neuropeptide. Substance P at 10(-7) M and the carboxy-terminal fragment SP(4-11) slightly enhanced the lymphocyte responses to phytohemagglutinin and concanavalin A. In contrast, the amino-terminal fragment SP(1-4) failed to have any positive effect. However, in the presence of dipeptidylpeptidase IV/CD26 and neutral endopeptidase/CD10 inhibitors (diprotin A and thiorphan, respectively), the effect of substance P on mitogen-induced proliferation was significantly increased. These data support the hypothesis that lymphocyte surface peptidases play a modulatory role in the effects of substance P on T cell function.

Effects of the neuropeptide, substance P, on lymphocyte proliferation in rheumatoid arthritis

There is evidence supporting the involvement of the neuropeptide, substance P, in the pathogenesis of rheumatoid arthritis. In view of the suggested role of T-cells in this disease, we have investigated the effects of substance P on mitogen-induced lymphocyte proliferation in rheumatoid arthritis patients. The peripheral blood mononuclear cells from 20 patients with rheumatoid arthritis and 25 controls were cultured in the presence or absence of substance P (10(-10) M to 10(-6) M) and stimulated with phytohaemagglutinin or concanavalin A. After 3 days of culture the proliferative responses were determined by measuring [3H]thymidine incorporation into the cells. Substance P enhanced, in a dose-dependent manner, the lymphocyte proliferative responses both in rheumatoid arthritis patients and in controls. Although there was a trend towards a greater enhancing effect in the rheumatoid arthritis patients, this was not statistically significant. Some individual patients with rheumatoid arthritis showed enhancements of lymphocyte proliferation with substance P that were clearly outside the range seen in healthy controls. The possibility that substance P has a role in the pathogenesis of rheumatoid arthritis through the up-regulation of lymphocyte activation should be considered in further studies of the immunomodulatory properties of substance P in arthritis.

T-helper reactivity to simian immunodeficiency virus gag synthetic peptides in human immunodeficiency virus type 2 infected individuals

West African populations are infected with divergent strains of human immunodeficiency virus type 2 (HIV2), some of which are closely related to simian immunodeficiency virus (SIV) and it has been postulated that the HIV2 epidemic might have arisen by cross-species spread of SIV into the human population in West Africa. To gain some insight into the possible basis for cross protection between these two closely related viruses, the T-helper responses to 15 synthetic peptides from SIV gag synthetic peptides were investigated in seven HIV2-infected subjects and in seven healthy controls. Significant reactivity to at least one of the synthetic peptides tested was found in all patients and a statistically significant correlation between CD4+ lymphocyte absolute numbers and the number of reacting peptides was observed. A marginal lymphocyte reactivity was found in two of the healthy controls studied. In conclusion, this preliminary evidence that HIV2-infected patients exhibit T-cell responses to SIV gag peptides suggests that both viruses share t-helper epitopes in the gag viral region and raises the possibility of cross protection between SIV and HIV2 which may be relevant for HIV2 vaccine research based on closely related retroviruses.

ENV-specific cytotoxic T lymphocyte responses in HIV seronegative health care workers occupationally exposed to HIV-contaminated body fluids

Identification of the components of protective immunity are crucial for the development of effective prophylactic and therapeutic vaccine strategies. Analysis of HIV-specific responses in exposed but uninfected individuals might thus provide a unique resource to elucidate the components and correlates of protective immunity to HIV. In the present study we analyzed HIV-specific cytotoxic and helper T lymphocyte responses in health care workers (HCW) exposed to body fluids from HIV-positive individuals. HCW exposed to blood from HIV-negative individuals as well as healthy donors served as controls. Cytotoxic T lymphocyte (CTL) responses to HIV envelope (env) peptides were detected in 7/20 (35%) HCW exposed to HIV-positive blood and in none of the 20 health care workers exposed to uninfected blood or the seven healthy blood donors studied. HIV-specific CTL responses were detected only after in vitro stimulation, and were MHC class I restricted. No MHC class I restriction elements were uniformly identified among the different responders. 21/28 (75%) HCW exposed to contaminated blood responded to env as measured by IL-2 production to the peptides, in contrast to only 9/38 (24%) HCW exposed to HIV seronegative blood and 3/35 (9%) healthy blood donors. All the HIV exposed individuals were seronegative on repeated ELISA tests, and no evidence of infection was obtained by PCR analysis. These findings indicate that a single exposure to HIV can induce CTL immunity to HIV antigens, in the absence of other evidence of infection.

Distinct alterations in the distribution of CD45RO+ T-cell subsets in HIV-2 compared with HIV-1 infection

OBJECTIVE AND DESIGN

Some clinical studies indicate that disease progression in HIV-2-infected subjects may be slower than in HIV-1. We investigated whether there were differences in the distribution of CD45RO+ (memory) and CD45RA+ (naive) T-cell subsets between HIV-1 and HIV-2 infection.

METHODS

Analysis of lymphocyte subsets was performed by flow cytometry in peripheral blood mononuclear cells from healthy controls, HIV-1-(n = 49) and HIV-2-infected (n = 47) individuals divided into two groups: asymptomatic (ASY)/persistent generalized lymphadenopathy (PGL) and AIDS-related complex (ARC)/AIDS.

RESULTS

Both HIV-1- and HIV-2-infected patients had significant reductions in the absolute number and percentage of CD4+ lymphocytes compared with seronegative individuals. No significant differences were found between HIV-2- and HIV-1-infected subjects in the same clinical stage. CD4+CD45RA+ cells were significantly reduced in HIV-1 and HIV-2 ARC/AIDS patients and mildly reduced in ASY/PGL HIV-1 and HIV-2 patients. There were no differences in the degree of reduction of CD4+CD45RO+ cells in ASY/PGL HIV-1 versus HIV-2 patients. However, in HIV-1-infected ARC/AIDS individuals the reduction in the percentage of this subset was more pronounced than in HIV-2 infection and this difference reached statistical significance. The increase in CD8+ lymphocytes (percentage and absolute number) was more pronounced in HIV-1 and the differences between HIV-1- and HIV-2-infected patients were statistically significant. CD8+CD45RO+ cells were significantly increased both in ASY/PGL and ARC/AIDS HIV-1-infected patients, whereas HIV-2-infected ASY/PGL patients had normal levels of these cells and HIV-2-infected ARC/AIDS patients had increases that were much less pronounced than that observed in HIV-1-infected ARC/AIDS patients. Significant differences in the absolute number and percentage of this subset between HIV-1- and HIV-2-infected individuals in similar clinical stages were found.

CONCLUSIONS

HIV-2-infected individuals exhibit a lesser degree of depletion of memory CD4+ cells and a more limited expansion of CD8+CD45RO+ subset, which could be related to the putative lower immunopathogenicity of HIV-2.

Panel of anti-gp120 monoclonal antibodies reacts with same nuclear proteins in uninfected cells as those recognized by autoantibodies from patients with systemic lupus erythematosus

Mouse monoclonal antibodies (MAbs) directed against the HIV-1 gp120 envelope protein were screened for their reactivity with intracellular antigens expressed in normal uninfected monocytes by indirect immunofluorescence and immunoblotting. Some of these MAbs reacted with the nuclei of normal uninfected cells, producing three main staining patterns by indirect immunofluorescence. Western blot analysis showed that these monoclonal antibodies recognize peptides of various molecular weights present in nuclei preparations of normal monocytes. Reactivity with peptides of similar molecular weight was also detected in sera from both HIV-infected individuals and patients with systemic lupus erythematosus. This evidence for antigenic similarities between HIV-1 gp120 and nuclear antigens represents a novel example of molecular mimicry of self-antigens by HIV envelope proteins, which supports the involvement of mechanisms of autoimmunity in HIV disease pathogenesis through recruitment of autoimmune responses to self-structures by HIV antigens.

Disturbed immunoregulatory properties of the neuropeptide substance P on lymphocyte proliferation in HIV infection

The neuropeptide substance P (SP) is known to increase cell-mediated immune responses in animal models and healthy subjects. Several studies have suggested an involvement of neuropeptides in the immunopathogenesis of some diseases. The study of the immunomodulatory effects of neuropeptides, namely SP, may represent a model for the analysis of immunoregulatory defects in HIV infection at the level of the interaction between the immune and nervous systems, both of which are known to be affected by the virus. In the present study, we investigate the possibility of a disturbance in the immunomodulatory properties of SP in HIV infection by analysing the effects of SP (10(-10)-10(-6) M) on the lymphocyte proliferative responses to concanavalin A (Con A) and phytohaemagglutinin (PHA) assessed by 3H-thymidine incorporation in peripheral blood lymphocytes from 34 HIV-infected patients (16 asymptomatic (ASY)/persistent generalized lymphadenopathy (PGL); 18 ARC/AIDS) and in 37 healthy subjects. In ASY/PGL HIV-infected patients, SP 10(-7) M was identified as the concentration inducing the maximal increase in the lymphocyte responses to Con A and PHA, similarly to what was observed in healthy subjects. In ARC/AIDS patients, SP appeared to inhibit the mitogenic responses, particularly those induced by Con A, in contrast to the effects found either in healthy subjects or in ASY/PGL patients. These results suggest the existence of an alteration in the in vitro immunomodulatory properties of SP in ARC/AIDS patients compared with healthy subjects and ASY/PGL patients. In conclusion, the unexpected finding of an inhibitory effect of SP on lymphocyte proliferation from ARC/AIDS patients justifies further investigation of the neuropeptide-dependent immunoregulatory systems in HIV infection.

Restoration of HIV-specific cell-mediated immune responses by interleukin-12 in vitro

Peripheral blood mononuclear cells (PBMCs) from many asymptomatic individuals infected with human immunodeficiency virus-type 1 (HIV) are unresponsive as measured by in vitro T cell proliferation and interleukin-2 (IL-2) production to influenza virus and synthetic peptides of HIV envelope (Env). Strong influenza virus- and Env-stimulated IL-2 responses and T cell proliferation were restored when cultures were stimulated in the presence of IL-12. Interferon-gamma production by PBMCs from HIV seropositive (HIV+) patients was also restored with IL-12. Furthermore, in vitro antigen-specific production of IL-2 and proliferation of PBMCs from HIV- donors were suppressed by antibody to IL-12, but were not enhanced by addition of exogenous IL-12. Thus, IL-12 may be limiting in PBMCs from HIV+ but not HIV- individuals. These findings demonstrate that IL-12 can restore HIV-specific cell-mediated immunity in vitro in HIV-infected individuals and suggest a potential use of IL-12 in augmenting the diminished immunologic functions associated with HIV infection.

Evidence for prostaglandin-producing suppressor cells in drug-induced liver injury and implications in the diagnosis of drug sensitization

Lymphocyte reactivity to drugs is present in a minority [corrected] of cases of drug-induced liver injury when in vitro proliferation assays to the suspected drugs are used. One possible explanation to this could be that adherent suppressor cells mediating their action through the production of prostaglandin E2 would suppress the lymphocyte proliferation to drugs in vitro. We studied 42 patients with a clinical diagnosis of drug-induced liver injury by comparing lymphocyte proliferation observed in cultures with five different concentrations of the suspected drug with the lymphocyte proliferation observed in cultures with drug and a prostaglandin inhibitor (indomethacin). Forty-four healthy subjects and 15 individuals with a recent exposure to the suspected drug without development of adverse drug reactions were also studied as controls. In nine (21%) out of 42 patients with drug-induced liver injury a significant lymphocyte reactivity to drugs was detected. When a prostaglandin inhibitor was added to the cultures, the detection of lymphocyte reactivity increased from 21% to 57%. No cases of lymphocyte reactivity to drugs or drugs with prostaglandin inhibitor were found in the control groups. The phenomenon of increase of lymphocyte proliferation with the addition of a prostaglandin inhibitor was more frequent in patients whose hepatitis was cured in less than 2 months, was more frequently found in certain pharmacological groups and was significantly associated to a latency period to development of hepatitis of less than 8 days. In conclusion, the in vitro phenomenon described here may be used to improve the ability to demonstrate lymphocyte sensitization in drug-induced liver injury and the clinical correlations found are consistent with the possibility of its relevance in vivo.

Inhibition of lymphocyte proliferation induced in vitro by microbial antigens in HIV-infected subjects

In the course of a study of lymphocyte responses to microbial antigens in HIV-infected patients, we detected a previously unrecognized phenomenon of inhibition of lymphocyte baseline proliferation, induced by the presence of tetanus toxoid and Escherichia coli in the cultures. The effects of tetanus toxoid and Escherichia coli on lymphocyte proliferation in vitro were assessed by comparing the 3H-thymidine uptake by lymphocytes cultured without stimulant with the uptake of lymphocytes cultured in the presence of the antigens. Twenty-six patients with HIV infection (20 asymptomatic/persistent generalized lymphadenopathy, 2 AIDS-related complex, 4 AIDS) were investigated and the controls were 33 healthy individuals without evidence of HIV infection. Eight out of 22 asymptomatic/PGL and ARC patients progressed to full-blown AIDS in the mean follow-up of 26 months. The inhibition of proliferation was considered to be significant when the uptake of 3H-thymidine was reduced by 20% in the presence of the antigens. Using these criteria, 50% of the patients studied with tetanus toxoid and 36% of those studied with E. coli had evidence of the inhibitory phenomenon. Seven of the eight patients who developed AIDS during the observation period had the inhibitory phenomenon. In the group of patients without the inhibitory signs only one evolved to AIDS during the follow-up. The possibility of this phenomenon being related to an induction of suppressor cell activity by the antigens is discussed.