HIV-1 gp41 by a common immunological epitope induces increased levels of antibodies against human interferon-beta in HIV-1 positive individuals

Lack of Evidence for Molecular Mimicry in HIV-Infected Subjects

Previous studies in HIV patients have reported autoantibodies to several human proteins, including erythropoietin (EPO), interferon-α (IFN-α), interleukin-2 (IL-2), and HLA-DR, as potential mediators of anemia or immunosuppression. The etiology of these autoantibodies has been attributed to molecular mimicry between HIV epitopes and self-proteins. Here, the Luciferase Immunoprecipitation System (LIPS) was used to investigate the presence of such autoantibodies in HIV-infected adults. High levels of antibodies to HIV proteins such as capsid (p24), matrix (p17), envelope (gp41), and reverse transcriptase (RT) were detected using LIPS in both untreated and anti-retroviral-treated HIV-infected individuals but not in uninfected controls. LIPS readily detected anti-EPO autoantibodies in serum samples from subjects with presumptive pure red cell aplasia but not in any of the samples from HIV-infected or uninfected individuals. Similarly, subjects with HIV lacked autoantibodies to IFN-α, IL-2, HLA-DR and the immunoglobulin lambda light chain; all purported targets of molecular mimicry. While molecular mimicry between pathogen proteins and self-proteins is a commonly proposed mechanism for autoantibody production, the findings presented here indicate such a process is not common in HIV disease.

HIV-1 gp41 and type I interferon: sequence homology and biological as well as clinical implications

HIV-1 gp41-like human type I interferon (IFN) could inhibit lymphocyte proliferation and up-modulate MHC class I and II and ICAM-1 molecule expression. Sequence comparison indicates that a similar epitope RILAV-YLKD exists between N-domain of gp41 and two regions in IFN-alpha(aa29-35 and 113-129), IFN-beta (aa31-37 and 125-138) and IFN-omega (aa29-35 and 123-136), which was shown to form IFN-alpha/beta-receptor binding site. Weak sequence similarity was also found to exist in both regions on gp41 and type I IFN of murine and bovine. Experimental studies indicated that a common immunological epitope exists between gp41 and IFN-alpha and -beta. Antibodies against human IFN-alpha and -beta recognized the common immunological epitope and inhibited gp41-binding to the potential cellular receptor protein p45. Moreover, the polyclonal antibody to IFN-beta completely inhibited gp41-binding to human T, B cells and monocytic cells, while IFN-alpha could only inhibit this binding incompletely. It was interestingly observed that human IFN-beta after preincubating with cells could incompletely inhibit the binding of gp41 to human B cells and monocytic cells, and very weakly inhibit the binding to human T cells, indicating that the receptor for IFN-beta-binding may be involved in gp41 binding. This potential relationship may be based on the amino acid sequence homology in the receptor binding region between gp41 and IFN-beta. It was observed that the increased levels of antibodies against human IFN-alpha and -beta exist in HIV-1-infected individuals and are associated with the common epitope on gp41. Besides, several studies provided experimental evidence that the common immunological epitope could induce protective activity against HIV-1. The IFN-alpha-based vaccine has showed a significant reduction of disease progression in IFN-alpha-vaccine-treated HIV-infected patients. Recent experimental evidence indicates that gp41 and IFN-beta were involved in downregulation of CCR5 expression and induction of cell activation or signal transduction. Whether it may be performed by a similar mechanism is still to be investigated.

Human interferon-beta inhibits binding of HIV-1 gp41 to lymphocyte and monocyte cells and binds the potential receptor protein P50 for HIV-1 gp41

Previous findings have indicated that HIV-1 gp41 like human type I interferon (IFN) could inhibit lymphocyte proliferation and up-modulate MHC class I, II and ICAM-1 molecule expression, and a common epitope exists between gp41 and type I interferon (IFN-alpha and -beta) in the receptor binding regions. To clarify the relationship between human type I interferon and HIV-1 gp41, we tried to inhibit recombinant soluble gp41-binding to human T, B and monocyte cell lines by human IFN-alpha, -beta and -gamma. It was interestingly observed that IFN-beta after preincubating with cells could inhibit the binding of rsgp41 to H9, Raji and U937 cells (T, B and monocyte cell lines), while this binding could not be inhibited by another type I interferon (IFN-alpha) and a type II interferon (IFN-gamma). It was further examined whether human IFN-alpha and -beta bind to the gp41 binding protein P50. In ELISA-assay, the human IFN-beta, but not IFN-alpha, could bind to P50 which was identified as a potential cellular receptor protein for gp41-binding. By the affinity capillary electrophoresis (ACE) analysis, formation of stable IFN-beta-P50 complex was observed. These results indicate that IFN-beta binds the potential receptor protein P50. Based on these experimental evidences and previous studies, it was presumed that the potential cellular receptor protein P50 may be the 51 kDa subunit of human IFN-alpha/beta receptor, which needs to be verified in the future.