Identification of an idiotypic peptide recognized by autoantibodies in human immunodeficiency virus-1-infected individuals

The Question of HIV Vaccine: Why Is a Solution Not Yet Available?

Ever since its discovery, human immunodeficiency virus type 1 (HIV-1) infection has remained a significant public health concern. The number of HIV-1 seropositive individuals currently stands at 40.1 million, yet definitive treatment for the virus is still unavailable on the market. Vaccination has proven to be a potent tool in combating infectious diseases, as evidenced by its success against other pathogens. However, despite ongoing efforts and research, the unique viral characteristics have prevented the development of an effective anti-HIV-1 vaccine. In this review, we aim to provide an historical overview of the various approaches attempted to create an effective anti-HIV-1 vaccine. Our objective is to explore the reasons why specific methods have failed to induce a protective immune response and to analyze the different modalities of immunogen presentation. This trial is registered with NCT05414786, NCT05471076, NCT04224701, and NCT01937455.

What Can We Learn from Research with Monoclonal Antibody 1F7?

1F7 is a monoclonal antibody that recognizes an idiotypic determinant expressed on primate antibodies binding to HIV-1 and hepatitis C proteins. This monoclonal antibody was used as a tool to dissect the immune response in humans infected with HIV-1 and hepatitis B. Furthermore, 1F7 was also used to manipulate the immune response against HIV-1 in macaques. The generation of a monoclonal antibody describing a network suggests similar antibodies could be developed as tools to dissect entangled networks in autoimmune diseases and allergic reactions. This review discusses the body of work done with 1F7 in the light of contemporary immunology.

A Novel Hypothesis for Original Antigenic Sin in the Severe Disease of SARS-CoV-2 Infection

In this hypothesis, we address the biological/immunological pathway leading to severe disease or death after infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The underlying immune response is described with "original antigenic sin" (OAS) whereby previous infections influence the response to future virus encounters. We cite evidence for OAS-induced immunopathology in HIV-1 disease. We hypothesize that similar immune abnormalities can occur after infection with SARS-CoV-2. This hypothesis is supported by recent analysis of the antibodies in infected patients demonstrating serological and B cell abnormalities. The concept of symmetrical clonal regulation developed earlier for the immune network illustrates the pathway suggested by our hypothesis and may be helpful to develop strategies avoiding severe coronavirus disease 2019.

The Homophilic Domain - An Immunological Archetype

The homophilic potential emerges as an important biological principle to boost the potency of immunoglobulins. Since homophilic antibodies in human and mouse sera exist prior environmental exposure, they are part of the natural antibody repertoire. Nevertheless, hemophilic properties are also identified in induced antibody repertoire. The use of homophilicity of antibodies in the adaptive immunity signifies an archetypic antibody structure. The unique feature of homophilicity in the antibody repertoire also highlights an important mechanism to boost the antibody potency to protect against infection and atherosclerosis as well to treat cancer patients.

The Significance of a Common Idiotype (1F7) on Antibodies against Human Immune Deficiency Virus Type 1 and Hepatitis C Virus

In this review, we trace the concept and potential functional role of regulatory idiotypes in the immune response to human immunodeficiency virus type 1 (HIV-1), simian immunodeficiency virus, and hepatitis C virus (HCV). A major idiotype involved in these viral infections is recognized and defined by a murine monoclonal antibody (1F7). Antibodies expressing the idiotype defined by 1F7 are dominant in HIV-1 infection and are also found on many broadly neutralizing antibodies against HIV-1. This regulatory idiotypic axis offers opportunities for exploitation in vaccine development for HIV-1, HCV, and other chronic viral infections.

Novel vaccine concept based on back-boost effect in viral infection

A novel vaccine concept is discussed based on recent evidence of a "back-boost" effect in Influenza infection. The initial immune response to the infection is imprinted through an immune memory pathway. The immune memory in the back-boost mechanism could be used in reversed order as a "forward-boost" in the proposed vaccine concept.

The anti-idiotypic antibody 1F7 stimulates monocyte interleukin-10 production and induces endotoxin tolerance

BACKGROUND

Pathogens that establish chronic infection elicit immune responses with suppressive cytokines dominating over pro-inflammatory cytokines. Chronic hepatitis C virus (HCV) infection, human immunodeficiency virus (HIV) infection and simian immunodeficiency virus (SIV) infection are associated with high levels of antiviral antibodies expressing a common idiotype specifically recognized by the 1F7 monoclonal antibody (mAb). The 1F7 mAb is a murine IgMκ antibody raised against immunoglobulin pooled from the plasma of multiple HIV-infected individuals. In this study, we investigated direct effects of the 1F7 mAb itself on peripheral blood mononuclear cells (PBMC).

METHODS

Isolated monocytes or PBMC from healthy controls were incubated with the 1F7 mAb or IgMκ mAb control. Cytokine production was measured in cell culture supernatants by ELISA and cells producing interleukin-10 (IL-10) were identified by subset depletion and intracellular flow cytometry. Endotoxin tolerance was assessed by exposing monocytes to lipopolysaccharide (LPS) following 1F7 mAb or IgMκ mAb control pre-treatment and comparing tumor necrosis factor (TNF)-α levels in cell culture supernatants.

RESULTS

The 1F7 mAb stimulated monocytes and CD36+ lymphocytes to produce IL-10 in a time and dose-dependent manner. Treatment of monocytes with 1F7 mAb also reduced their subsequent responsiveness to LPS stimulation.

CONCLUSIONS

Induction of antibodies expressing the 1F7 idiotype by chronic pathogens may facilitate IL-10 production and progression to chronic infection. Direct effects of IL-10 from human monocytes stimulated by 1F7-like antibodies, followed by monocyte transition to an alternatively activated phenotype illustrated by endotoxin tolerance, are two complementary features favouring a tolerogenic or non-responsive immunological environment.

The promise of the anti-idiotype concept

A basic tenet of antibody-based immunity is their specificity to antigenic determinates from foreign pathogen products to abnormal cellular components such as in cancer. However, an antibody has the potential to bind to more than one determinate, be it an antigen or another antibody. These observations led to the idiotype network theory (INT) to explain immune regulation, which has wax and waned in enthusiasm over the years. A truer measure of the impact of the INT is in terms of the ideas that now form the mainstay of immunological research and whose roots are spawned from the promise of the anti-idiotype concept. Among the applications of the INT is understanding the structural implications of the antibody-mediated network that has the potential for innovation in terms of rational design of reagents with biological, chemical, and pharmaceutical applications that underlies concepts of reverse immunology which is highlighted herein.

Stimulation of antiviral antibody response in SHIV-IIIB-infected macaques

Three macaques infected with SHIV-IIIB and expressing the shared 1F7-idiotypic marker on antibodies against HIV-1 gp120, were injected intravenously with 1F7 monoclonal antibodies (MoAb). As controls, a SHIV-IIIB-infected macaque was injected with a HIV-unrelated mouse monoclonal isotype antibody (TEPC-183) and two healthy, noninfected macaques were injected with MoAb 1F7. 1F7-id-expressing antibodies against gp120-IIIB decreased in two of the three MoAb 1F7-treated macaques and then rebounded. Importantly, antibodies binding to envelope proteins of heterologous HIV-1 strains MN, CM, and SF2, which were low or not detectable before the MoAb 1F7 treatment, increased rapidly following MoAb inoculations in all three 1F7 MoAb treated macaques, but not in the macaque injected with control MoAb TEPC-183. Newly arising antibodies reacting with heterologous virus, i.e. HIV-1 gp120-MN, SF2, and CM did not express 1F7-id. Surprisingly, significant increases of antibodies were also observed in the 1F7-inoculated macaques' antibodies directed to non-HIV antigens (DNP, peptides and BSA). The noninfected control animals did not produce antibodies to these antigens despite MoAb 1F7 treatment. These data show that the MoAb 1F7 injections of chronically SHIV-IIIB-infected macaques resulted in idiotype-specific clonal suppression with broadening the antibody response to HIV envelope proteins.

AIDS epidemic at the beginning of the third millennium: time for a new AIDS vaccine strategy

Current expansion of AIDS pandemic significantly accelerates AIDS vaccine research resulting in development and clinical testing of several AIDS vaccine candidates. At the same time, available experimental and clinical data demonstrate that current AIDS vaccine strategy is unsuccessful resulting in development of inefficient and harmful vaccines. This overview briefly summarizes reported results which point out the requirement for moratorium on the current clinical trials of HIV-1 gp120/160 vaccines and urgent need for development of a new, efficient and safe AIDS vaccine strategy.

Dissection of an antibody paratope into peptides discloses the idiotope recognized by the cognate anti-idiotypic antibody

Using methods of parallel synthesis, the complete amino acid sequence of an Ab 1 antibody (Tg 10, an anti-human thyroglobulin monoclonal antibody) was made in the form of a set of 100 synthetic overlapping peptides. This set of immobilized peptides was allowed to react with the cognate Ab2 (AI 10, a highly purified rabbit anti-idiotypic polyclonal antibody to Tg 10). A dominant peptide idiotope, INTFSGVPTYA, was thus mapped, which corresponds mainly to the CDR2 region from the V(H) domain of the Tg 10 mAb. A synthetic peptide replica of this idiotope was found to bind to AI 10 with an affinity (K(D) in the 10(-8) M range, as measured using BIACORE technology) which represents a significant part of the affinity of the complete Tg 10 antibody (K(D) in the 10(-9) M range). The synthetic peptide also elicited anti-idiotypic antibodies in rabbits that recognized specifically the Ab1 antibody in an Ab1- and antigen-inhibitable manner. The peptide idiotope was further characterized chemically by the identification of residues important for binding to the Ab2 and by modelization of its structure. Our approach makes it readily possible to map and characterize functional, continuous-type idiotopes that could be further used to manipulate the immune response by peptide technologies.

Anti-V3 and anti-IgG antibodies of healthy individuals share complementarity structures

It was recently shown that antibodies reactive with a peptide from the tip of the HIV-1NY5 gp120 V3 loop (V3 peptide) are present not only in sera of HIV-positive patients but also in sera of healthy HIV-negative individuals. In the present study, we show that V3 peptide reactive antibodies are predominantly IgM in sera of HIV negative individuals and that a fraction of the IgG anti-V3 antibodies exhibit features of autoantibodies. These antibodies were purified by chromatography on IgG-sepharose columns from sera as well as from purified IgG anti-V3 antibodies. A higher IgG anti-V3 reactivity was detected in autoantibody preparations from HIV-positive sera as compared with the reactivity of sera and purified antibodies from HIV-negative individuals. This was confirmed by solid phase binding of IgG anti-V3 antibodies both to V3 and to human IgG F(ab')2 antigens. The autoantibodies did not bind to peptides that share sequence similarity with V3 peptide indicating a high epitope specificity. The detection of antibodies against HIV epitopes in HIV-negative individuals may suggest that anti-V3 antibodies after HIV infection represent at least in part a secondary immune response.

Anti-F(ab')2 antibody in HIV type 1 infection: relationship to hypergammaglobulinemia and to antibody specific to the V3 loop region of glycoprotein 120

As HIV infection and autoimmune disease share certain similarities, it has been suggested that HIV may disrupt control of humoral immunity by the antiidiotype network, and that this may be evident as increased IgG antibody to F(ab')2. When anti-F(ab')2 was quantified by ELISA in sera of randomly chosen HIV-infected versus uninfected donors, some HIV-infected sera did contain increased anti-F(ab')2, resulting in a median amount twofold higher than in uninfected sera. Moreover, when data were grouped by blood CD4 lymphocyte count, anti-F(ab')2 in HIV+ groups appeared to rise as CD4 lymphocytes declined. However, increased anti-F(ab')2 mirrored the elevation in serum IgG closely, and normalization of anti-F(ab')2 to serum IgG concentration equalized the groups so that no relationship to CD4 lymphocytes remained. Hypergammaglobulinemia is therefore strongly implicated as a cause of variation in anti-F(ab')2. After dissociation of immune complexes, anti-F(ab')2 activity per microgram of monomeric IgG was slightly increased over normal only in the HIV-infected group with fewest CD4 lymphocytes, without statistical significance. In contrast, the proportion of IgG antibody to the V3-neutralizing determinant in HIV-1 decreased significantly as disease advanced. The same was true for 12 HIV+ individuals studied longitudinally for 500-1300 days. The data suggest that measuring serum anti-F(ab')2 is misleading when immune complexes are present: apparent increases as disease progresses are due to increased IgG and, possibly, to related technical artifacts. During HIV infection, the proportion of antiidiotypic IgG in fact remains unaltered or falls, making this an unlikely cause of suppressed humoral immunity to HIV-1.

Affinity columns containing anti-DNA Id+ human myeloma proteins adsorb human epibodies from intravenous gamma globulin

OBJECTIVE

To study eluates of intravenous gamma globulin (IVGG) prepared from affinity columns of human cationic IgG myeloma proteins bearing anti-DNA idiotype (Id) markers 16/6, F4, 3I, and 8.12 for possible anti-Id (combining site) blocking activity.

METHODS

Anti-DNA idiotypic antibody activity was studied in 3 preparations of IVGG containing high, medium, and low levels of IgG anti-F(ab')2, and in 4 other commercial IVGG preparations. Affinity-purified IgG anti-DNA (APAD) from systemic lupus erythematosus (SLE) patients was biotinylated, and binding to DNA coated on enzyme-linked immunosorbent assay plates was used to measure anti-DNA antibody activity. IVGG was adsorbed to Sepharose 4B affinity columns linked to a panel of cationic human IgG myeloma proteins positive for anti-DNA Id markers 16/6, F4, 3I, and 8.12. Material adsorbing to such columns was eluted at low pH (2.5) and after neutralization, tested for its ability to inhibit biotinylated APAD reacting with DNA.

RESULTS

Only 0.05-0.9% of IVGGs bound firmly to Id affinity columns. These IVGGs were then eluted, using pH 2.5 glycine-saline and eluates neutralized to pH 7.4. Column flowthrough and eluate fractions were compared for their ability to block SLE APAD reacting with DNA. Significant inhibition of SLE APAD combining sites was observed with eluates from anti-DNA Id affinity columns; however, no correlation between IVGG anti-F(ab')2 activity and true anti-Id blocking of APAD was apparent. No residual anti-Id activity remained in column flowthrough fractions. No anti-Id blocking activity was recorded for IVGG eluates from human cationic myeloma columns devoid of the 4 anti-DNA Id markers. DNase treatment of IVGG or Id column eluates did not affect anti-Id blocking activity. Thus, all detectable anti-DNA idiotypic antibody capable of blocking SLE anti-DNA combining sites bound to Id+ affinity columns. Column eluates also showed some relative concentration of IgG anti-DNA activity, which was of lower affinity for DNA than antibodies also present in eluates which blocked anti-DNA combining sites.

CONCLUSION

The presence of both anti-DNA and antiidiotypic (anti-combining site) activity in human anti-DNA Id column eluates indicates that epibodies from IVGG are relatively concentrated when this strategy is used. This approach may lead to a new strategy for treatment of SLE nephritis.

B cell superantigens in HIV-1 infection

HIV-I infection affects many of the cellular components vital for the maintenance of immune homeostasis. Similar to the T cell superantigen effect on T cell expansion and depletion in AIDS. HIV components with B cell superantigenic properties could be responsible for the observed B cell activation and skewing of VH family usage. Current data on possible B cell superantigen properties of HIV proteins (gp120) are mostly based on studies describing the clonality and VH family usage of immunoglobulins in HIV infection. Various laboratories reported independently an unusual skewing of the VH-repertoire of antibodies that appears not to be random. According to these observations, an enrichment of VH1 and VH4 family-paralleled a depletion of VH3 family-utilizing anti-HIV-1 gp120 and p24 antibodies in HIV-1 infected individuals and a loss of total VH3+ Ig in patients with late stages of AIDS. Polyclonal and monoclonal (VH1, VH4, and VH5) anti-p24 and gp120 antibodies share a crossreactive idiotype (IF7). IF7 like antibodies were found in the serum of HIV-1 infected individuals, persisting in the course of infection, perhaps contributing to the depletion of VH3 Ig. Furthermore a restriction of clonal heterogeneity of anti-p24 and anti-gp120 antibodies was detected by isoelectric focusing and indicated by skewed kappa/lambda light chain isotype ratios, indicating clonal dominance of certain sets of anti-HIV-1 antibodies during infection. Taken these findings together, a strong case for the involvement of a B cell superantigen can be made, although the mechanism of B cell depletion is not fully understood.