The 1F7 idiotype is selectively expressed on CD5+ B cells and elevated in chronic hepatitis C virus infection

Characteristics of Vaccine- and Infection-Induced Systemic IgA Anti-SARS-CoV-2 Spike Responses

Mucosal IgA is widely accepted as providing protection against respiratory infections, but stimulation of mucosal immunity, collection of mucosal samples and measurement of mucosal IgA can be problematic. The relationship between mucosal and circulating IgA responses is unclear, however, whole blood is readily collected and circulating antigen-specific IgA easily measured. We measured circulating IgA against SARS-CoV-2 spike (S) to investigate vaccine- and infection-induced production and correlation with protection. Circulating IgA against ancestral (Wuhan-Hu-1) and Omicron (BA.1) S proteins was measured at different time points in a total of 143 subjects with varied backgrounds of vaccination and infection. Intramuscular vaccination induced circulating anti-SARS-CoV-2 S IgA. Subjects with higher levels of vaccine-induced IgA against SARS-CoV-2 S (p = 0.0333) or receptor binding domain (RBD) (p = 0.0266) were less likely to experience an Omicron breakthrough infection. The same associations did not hold for circulating IgG anti-SARS-CoV-2 S levels. Breakthrough infection following two vaccinations generated stronger IgA anti-SARS-CoV-2 S responses (p = 0.0002) than third vaccinations but did not selectively increase circulating IgA against Omicron over ancestral S, indicating immune imprinting of circulating IgA responses. Circulating IgA against SARS-CoV-2 S following breakthrough infection remained higher than vaccine-induced levels for over 150 days. In conclusion, intramuscular mRNA vaccination induces circulating IgA against SARS-CoV-2 S, and higher levels are associated with protection from breakthrough infection. Vaccination with ancestral S enacts imprinting within circulating IgA responses that become apparent after breakthrough infection with Omicron. Breakthrough infection generates stronger and more durable circulating IgA responses against SARS-CoV-2 S than vaccination alone.

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.

Selection of human anti-HIV broadly neutralizing antibodies occurs within the context of frozen 1F7-idiotypic repertoire

OBJECTIVE

Most HIV-infected individuals develop HIV-specific antibodies (Abs) exhibiting a common idiotype designated as 1F7. Expression of this idiotype establishes idiotypic-driven repertoire freeze, maintaining antibody responses ineffective at controlling autologous contemporaneous viruses. As such, this study investigated the temporal dynamics of 1F7-idiotype expression, as well as the role of this idiotype in the selection of HIV-specific broadly neutralizing antibodies (BnAbs).

DESIGN

This study investigated the timing of appearance and persistence of 1F7-idiotypic HIV-specific Abs by screening plasma samples from individuals followed longitudinally starting in primary HIV infection. The expression of 1F7 on HIV-specific BnAbs was also investigated to determine whether their development occurs within the context of 1F7-idiotypic repertoire freeze.

METHODS

The 1F7 idiotype was detected on gp120, gp41 and membrane proximal external region (MPER) peptide-specific Abs using an enzyme-linked immunosorbent assay (ELISA). HIV-specific Abs in longitudinal plasma samples from six patients and six BnAbs were tested for the presence of the 1F7 idiotype.

RESULTS

The idiotype was expressed on HIV-specific Abs within 3 months of infection, with the magnitude of 1F7 detection increasing with time from infection. The 1F7 idiotype was also expressed on all BnAbs tested.

CONCLUSION

These results demonstrate that HIV-specific antibody responses are restricted within the 1F7 idiotype from early infection onwards, and that six well characterized BnAbs developed within the context of 1F7-idiotypic repertoire freeze. Future research should evaluate the necessity of the 1F7 idiotype for broad neutralization, and determine if vaccines should target Abs within or outside this idiotypic space.