Increased levels of antibodies against interferon-alpha in HIV-1 positive individuals may be explained by a common immunological epitope on the human interferon-alpha and HIV-1 gp41

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.

Chemiluminescent imaging analysis of interferon alpha in serum samples

Enzyme-linked immunosorbent assay (ELISA), horseradish peroxidase (HRP)-catalyzed fluorescent reaction, and oxalate chemiluminescence imaging analysis have been combined to develop a sensitive, simple, and rapid method for analysis of interferon alpha (alpha-IFN) in human serum samples. A typical "sandwich type" immunoassay was used. Reaction of o-phenylenediamine (OPD) with hydrogen peroxide (H(2)O(2)), catalyzed by HRP, produced 2,3-diaminophenazine (PDA), which was detected by chemiluminescence imaging analysis with the bis(2,4,6-trichlorophenyl)oxalate (TCPO)-H(2)O(2)-glyoxaline-PDA chemiluminescent system. The TCPO chemiluminescent imaging system is more sensitive and the chemiluminescence quantum yield is at least five times higher than for the luminol-H(2)O(2)-HRP-PIP (p-iodophenol) chemiluminescent imaging system. The results showed there was a very good linear correlation between response and amount of alpha-IFN in the range 1.3-156.0 pg mL(-1) (R = 0.9991) and the detection limit was 0.8 pg mL(-1) (S/N=3). The relative standard deviation (n = 9) was 4.7%. The proposed method has been used for successful analysis of the amount of alpha-IFN in human serum. The results obtained compared well with those obtained by conventional colorimetric ELISA and luminol chemiluminescent ELISA.

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.

The genetic basis for the association of the 8.1 ancestral haplotype (A1, B8, DR3) with multiple immunopathological diseases

An individual's major histocompatibility complex (MHC) ancestral haplotype (AH) is the clearest single determinant of susceptibility to MHC associated immunopathological disease, as it defines the alleles carried at all loci in the MHC. However, the direct effects of any of the 150-200 genes that constitute the MHC are difficult to determine since recombination only occurs at defined hotspots. This review concerns the 8.1 AH (HLA-A1, C7, B8, C4AQ0, C4B1, DR3, DQ2), which is carried by most Caucasians with HLA-B8. It is associated with accelerated human immunodeficiency virus (HIV) disease, and susceptibility to insulin-dependent diabetes mellitus (IDDM), systemic lupus erythematosus, dermatitis herpetiformis, common variable immunodeficiency and IgA deficiency, myasthenia gravis and several other conditions. We have mapped susceptibility genes for HIV, IDDM and myasthenia gravis to the central MHC between HLA-B and the tumour necrosis factor or complement genes. Here we consider which of the remaining 8.1-associated diseases are more closely associated with HLA-DR3 and/or DQ2. Several candidate genes in the central MHC have the potential to modulate immune or inflammatory responses in an antigen-independent manner, as is seen in studies of cultured cells from healthy carriers of the 8.1 AH. Hence these genes may act as a common co-factor in the diverse immunopathological conditions associated with the 8.1 AH.

The immunosuppressive peptide of HIV-1 gp41 like human type I interferons up-regulates MHC class I expression on H9 and U937 cells

Based on our findings that the immunosuppressive peptide (ISP, amino acids (aa) 583-599) of human immunodeficiency virus type 1 (HIV-1) gp41 shows sequence-similarity with human type I interferons (IFN-alpha and IFN-beta) and HIV-1 soluble gp41 (sgp41, aa 539-684) enhanced cell surface expression of major histocompatibility complex (MHC) class I molecule on human H9 (T cells), Raji (B cells) and U937 (monocytic cells) cells, we examined the effect of HIV-1 immunosuppressive peptide on the surface expression of MHC class I molecules on H9 and U937 cells. Flow cytometry analysis demonstrated that ISP-BSA (conjugate) could enhance MHC class I expression by about 40% on H9 cells and by about 45% on U937 cells, while monomer ISP (not conjugated) and EDCI-treated carrier protein (BSA-EDCI) did not increase the expression. By comparison, human type I interferons, IFN-alpha and IFN-beta, showed similar effects (enhanced the expression by about 40-60%) to ISP-BSA on the MHC class I expression on H9 and U937 cells. The results suggest that HIV-1 gp41 in a polymerized form by its immunosuppressive domain upregulates human MHC class I expression. The basis for this similar effect of HIV-1 gp41 and IFN-alpha and -beta, i.e. upregulation of MHC class I molecule expression, may be based on the sequence-similarity between these otherwise different molecules.