Cytokine and cytokine receptor concentrations in bone marrow supernatant from patients with HIV: correlation with hematologic parameters

BACKGROUND

To determine the concentrations of tumor necrosis factor (TNF) alpha, soluble TNF receptors (sTNFR), interleukin (IL)-1 beta, gamma-interferon (IFN), macrophage inflammatory protein (MIP)-1 alpha, MIP-1 beta, and RANTES to which hematopoietic progenitors are exposed in vivo in HIV patients and the correlation of these concentrations with hematologic parameters, cytokine and cytokine receptor concentrations were measured by ELISA in bone marrow aspirate supernatants from 19 HIV patients undergoing diagnostic evaluation and 14 healthy paid volunteer controls. IL-1 beta and gamma-IFN were rarely detectable. All cytokines/receptors detectable in marrow supernatant, except RANTES, showed mean concentrations 1.6- to 6.2-fold higher in patients with HIV compared to healthy controls.

METHODS

Elevated TNF-alpha and MIP-1 beta were associated with marrow involvement by lymphoma, Hodgkin disease, or mycobacterial infection. Concentrations of all cytokines/receptors measured correlated with the severity of anemia. CD8+ lymphocytes were inversely correlated with concentrations of all cytokines measured other than MIP-1 alpha. To identify differences specific to HIV infection, marrow supernatant cytokine concentrations were also evaluated in 9 non-HIV patients undergoing diagnostic marrow examination. Significant differences were observed in TNF alpha, MIP-1 alpha, and IL-1 beta concentrations.

RESULTS

These studies demonstrate that concentrations of these cytokines and receptors are elevated in bone marrow supernatant of HIV-infected patients with hematologic abnormalities, and that these concentrations correlate with clinical parameters in these patients.

CONCLUSIONS

Evaluation of local concentrations of cytokines may be relevant to understanding tissue-specific pathology in HIV-infected individuals.

Inhibition of human erythroid colony formation by ceramide

In previous studies, we have demonstrated that the inhibitory effects of tumor necrosis factor (TNF) and interleukin (IL)-1 on human erythroid colony formation are indirect and mediated by beta and gamma interferon (IFN), respectively, which act directly upon erythroid colony forming units (CFU-E). The in vitro inhibitory effect of gammaIFN but not betaIFN is reversed by exposure to high concentrations of recombinant human (rh) erythropoietin (EPO). Ceramide, a product of sphingomyelin hydrolysis, is a known mediator of apoptotic effects of TNF, IL-1, and gammaIFN. In this report, the effects of ceramide on CFU-E colony formation and its implication in the model described above are evaluated. Endogenous ceramide produced by exposure to bacterial sphingomyelinase (0.2-2.0 U/mL) and exogenous cell-permeable ceramide (C2-ceramide; 5 and 10 mM) significantly inhibited bone marrow CFU-E colony formation. This effect was reversed by the ceramide antagonist sphingosine-1-phosphate (S-1-P). Inhibition of CFU-E by rhgammaIFN, but not rhbetaIFN, was significantly reversed by S-1-P. rhEPO 10 U/mL reversed CFU-E inhibition by C2-ceramide 10 mM. Exposure of marrow cells to rhgammaIFN led to a 57% increase in ceramide content. The present study demonstrates that colony formation by human CFU-E is inhibited by endogenous and exogenous ceramide, and that inhibition by rhgammaIFN can be reversed by the ceramide antagonist S-1-P. Inhibition of CFU-E colony formation by ceramide and by are both reversed by high concentrations of rhEPO. These findings strongly suggest that ceramide mediates inhibition of human CFU-E colony formation by gammaIFN.

Serum transferrin receptor levels in patients undergoing evaluation of iron stores: correlation with other parameters and observed versus predicted results

Serum transferrin receptor (sTfR) concentrations were measured in specimens from 77 patients undergoing serum ferritin determination, and the results correlated with serum ferritin, serum iron, serum total iron-binding capacity (TIBC) saturation, erythrocyte mean corpuscular volume (MCV), and mean corpuscular haemoglobin (MCH). All parameters exhibited the expected inverse correlation with sTfR; this correlation was statistically significant for all parameters except serum iron concentration. The frequency with which iron deficiency (defined as absence of stainable marrow iron) is observed in patients with particular ferritin values in this centre was determined and used to estimate the expected number of iron deficient patients in the present study. In no setting were significantly fewer sTfR levels > 3.05 micrograms/ml observed than expected. However, significantly greater than expected numbers of elevated sTfR values were observed in patients with serum ferritin > 220 micrograms/l (P = 0.002). The results suggest that the sTfR level is probably not useful as a single test for identification of iron deficiency in unselected patients.

Inhibition of marrow CFU-E colony formation from human immunodeficiency virus-infected patients by beta- and gamma-interferon

Increased production of cytokines such as beta-interferon (IFN) and gamma-IFN may contribute to the anemia frequently observed in patients with human immunodeficiency virus (HIV) infection. The hypothesis that HIV infection might enhance the susceptibility of erythroid progenitors to cytokine-mediated inhibition was evaluated by comparing the effects of beta- and gamma-IFN on in vitro colony formation by marrow erythroid colony-forming units (CFU-E) from HIV patients, normal volunteers, and anemic non-HIV-infected individuals. CFU-E colony formation from HIV patients was not significantly different from controls, and the degree of inhibition by IFN did not differ among patient subsets. HIV infection does not appear to impair baseline CFU-E colony formation, nor does it appear to enhance the susceptibility of CFU-E to suppression by cytokines.

Serum chemokine levels in patients with non-progressing HIV infection

OBJECTIVE

To evaluate serum chemokines, macrophage inflammatory protein (MIP)-1 alpha, MIP-1 beta and RANTES, concentrations in non-progressing HIV-infected patients and AIDS patients.

SETTING

University Hospital-based AIDS Clinical Trials Unit.

DESIGN/METHODS

Serum MIP-1 alpha, MIP-1 beta and RANTES levels were determined by enzyme-linked immunosorbent assay using archived serum specimens obtained on two occasions at least 1.8 years apart.

PATIENT SELECTION

Long-term non-progressing HIV-infected adult patients were identified from clinic records. For each non-progressing patient two adult AIDS patients with initial documentation of seropositivity the same year and the same length of follow-up were selected.

RESULTS

Four long-term non-progressing patients and eight AIDS patients were studied. Neither the duration of known HIV positivity at the time of specimen collection nor the length of time between specimen collections differed significantly between non-progressing patients and AIDS patients. Serum levels of MIP-1 alpha, MIP-1 beta and RANTES in specimens obtained either early or later in the course of HIV infection did not differ significantly between non-progressing patients and AIDS patients. In the two patient subsets, significant differences in serum chemokine levels over time were not observed. The rate of change of serum chemokine concentration over time also did not differ between non-progressing patients and AIDS patients. Serum MIP-1 alpha and MIP-1 beta levels did not reach levels reported to suppress HIV proliferation in vitro. When expressed as a quantity per peripheral blood CD8+ lymphocyte, AIDS patients exhibited significantly greater levels of MIP-1 alpha, MIP-1 beta and RANTES than non-progressing HIV patients (P < 0.05). These values did not exhibit a significant variation over time.

CONCLUSIONS

Serum MIP-1 alpha, MIP-1 beta and RANTES levels do not distinguish patients with AIDS from patients with non-progressing HIV infection. Variations in levels of these chemokines do not explain individual variation in the natural history of HIV infection.