Anti-leukocyte antibodies as a consequence of HIV infection in HIV+ individuals

Anti-human leukocyte antigen antibodies are present in blood of blood donors: is therapy with blood preparations safe for graft recipients?

BACKGROUND

Blood products infusions are often administrated to graft recipients. Post-transfusion reactions of anti-human leukocyte antigen antibodies (anti-HLA) are responsible for transfusion-related acute lung injury, but cases of graft rejection after blood product infusions were recently also proven.

METHODS

The aim of this study was to assess, with the use of the very sensitive Luminex technology and traditional lymphocytotoxic test, the prevalence and cytotoxic activity of anti-HLA in blood donors with different medical histories to evaluate a potential risk of post-transfusion immune complications. Data were analyzed according to different normalized background cutoffs (1.5, 2.2; and the high cutoffs-10.8 for I class and 6.9 for II class anti-HLA).

RESULTS

We observed that anti-HLA may be present in 36% of donors, and even in up to 73.6% of risk groups. Significant risk factors included female sex (23.9% to 64.2% for different cutoffs) and pregnancy history (30% to 72.5%), regardless of the cutoff used in analysis, whereas sera from female donors showed lower cytotoxicity (panel reactive antibodies). Anti-HLA were also detected in men (3.7% to 37%), in donors after a transfusion (0% to 62.5%), and even with no known risk factors (3.8% to 26.9%).

CONCLUSIONS

Luminex technology is a sensitive tool in anti-HLA detection, but consensus in measurement interpretation for blood donors is needed. Selection of blood products on the basis of medical history can be a useful alternative for routine testing of blood donors. The clinical significance of treatment of graft recipients with blood products requires further study; until then, more attention should be paid to possible complications.

Infection of macaques with simian immunodeficiency virus induces a species-specific antibody response to major histocompatibility complex class I and class II molecules

Envelopes of retroviruses, including human immunodeficiency virus and simian immunodeficiency virus (SIV), contain host cell proteins that potentially represent novel targets for vaccine development. We show here that sera from rhesus macaques recognized simian major histocompatibility complex (MHC) molecules in response to infection with SIV. Antibodies from these animals did not cross-react with human MHC antigens on mitogen-activated peripheral blood mononuclear cells. The development of antibodies to MHC class I alpha-chain did not correlate with anti-SIV envelope antibody responses, suggesting that these antibodies did not arise through molecular mimicry. In contrast to the species-specific response in infected animals, sera from animals vaccinated with inactivated human cell-grown SIV reacted to both human and rhesus MHC class I and class II molecules.

Improbability of harmful autoimmune responses resulting from immunization with HIV-1 envelope glycoproteins

Autoimmunity mediated by cross-reactive antibodies, elicited by HIV-1 envelope glycoproteins gp120/gp160, has been postulated to contribute to the pathogenesis of AIDS. Partial amino acid sequence homology between gp120/gp160 and several human host proteins, including MHC antigens and immunoglobulins, has been perceived as the basis for immunological cross-reactivity. Binding of antibodies from sera of HIV-1-infected individuals to selected host proteins and/or to synthetic peptides derived from them and the inhibitory activity of such sera in assays measuring the functional activity of T cells provided apparent support for the autoimmunity hypothesis, which is also relevant to the issue of safety of anti-HIV-1 vaccines. Considering the possibility that the detected autoantibodies may arise for reasons other than antibody responses to gp120/gp160, the immunological cross-reactivity between gp120/gp160 and the relevant host proteins was investigated using hyperimmune rabbit anti-gp120/gp160 and monoclonal antibodies. As determined from dilution end-point comparisons for polyclonal anti-gp120, the cross-reactivity of anti-gp120 with CD4 was undetectable (< 10(-5)%). The cross-reactivity of anti-gp120/gp160 with HLA-I and HLA-II antigens was also undetectable (< 4 x 10(-4)%) and that with other human proteins reported to have partial sequence homology with gp120/gp41 was < or = 0.013%. Anti-gp120/gp160 did not have detectable inhibitory effects in functional assays measuring proliferative T cell responses. Therefore, immunization with gp120/gp160 is unlikely to elicit harmful autoimmune responses.

Inhibition of normal natural killer cytotoxicity by sera from hemophilic patients

In this study we searched for circulating antibodies or other serum factors that could account for the natural killer (NK) defect observed in hemophiliacs (He) infected with the human immunodeficiency virus (HIV). We analyzed the effect of negative or positive sera for HIV from He on normal NK activity. We showed that sera from He interfered with normal NK cytotoxicity. The inhibitory activity was higher in HIV+ sera and increased as the HIV disease progressed. HIV- sera also inhibited NK function, although to a lesser extent than HIV+, and it was probably due to isoimmunization through replacement treatment with plasma-derived concentrates. For each individual, no direct correlation was found between NK inhibition (NK-INH) of sera and the NK activity of He peripheral blood mononuclear cells (PBMC). Furthermore, He serum was poorly inhibitory on autologous PBMC. Preincubation of allogenic effector or target cells with He sera revealed that the inhibitory effect was the result of the reaction with these cells. A positive correlation was found by comparing NK-INH of whole He sera with the serum levels of circulating immune complexes. When the NK-INH assay was performed using the same concentration of DEAE-purified IgG from N, HIV- or HIV+, we found that HIV+ AIDS IgG was more inhibitory than the others.