Recognition of defined epitopes by affinity-purified anti-immunoglobulin Fab autoantibodies isolated from HIV-infected humans

Abstract

Infection of humans with HIV-1 has previously been independently shown to result in the generation of autoantibodies (AAbs) reactive with immunoglobulin Fab fragments (Heidelberg), and with autoantibodies to T-cell receptors (TCRs) (Tucson). Here, we carry out epitope mapping studies of affinity-purified AAbs to Fab fragments prepared from individual HIV-positive patients for their capacity to bind recombinant constructs and peptide-defined epitopes modeling TCR and Ig light chains. Some affinity-purified autoantibodies reacted strongly with TCRs expressed by intact T-cells, and recombinant Valpha/Vbeta constructs as well as with certain synthetic peptide epitopes. The binding reactions of affinity-purified AAbs of individual patients were distinct, and the AAb preparations consisted of populations of polyclonal lgs as reflected in specificity and isotype. AAb pools from individual patients all bound particular regions of TCR and Ig chains defined by comprehensive peptide synthesis including the CDR1 and Fr3 segments of the variable domains and the joining segment/switch peptide. In addition, other reactivities to restricted regions of alpha, beta and lambda light chains were documented. These results substantiate the cross-reactivity of TCR and Ig-Fab determinants, and are consistent with the hypothesis that autoantibodies arising as a consequence of HIV infection can have an immunomodulatory role.

Exquisite specificity and peptide epitope recognition promiscuity, properties shared by antibodies from sharks to humans

“…Sera of healthy humans and mice contain low levels of naturally occurring autoantibodies to T-cell receptor Vb epitopes, and the levels and isotypes vary with normal physiological processes such as aging, as well as with autoimmune diseases, and retroviral infections (Marchalonis et al, 1994(Marchalonis et al, , 1999. Figure 2 illustrates the Vb peptide epitopes recognized by human IgG and sandbar shark IgM naturally occurring antibodies that were affinity purified on the recombinant T cell receptor single chain construct.…”

Exclusion of HIV epitopes shared with human proteins is prerequisite for designing safer AIDS vaccines

“…It is suggested, in particular, that gp120 inhibits the biological activity of IL-2 in vitro, possibly, due to competition for the IL-2 binding to its cellular receptor (Evans and Levy, 1989). The Gag similarity (478-488) to chain of immunoglobulins (51-58) as well as local similarity between Pol (240-248), Rev (37-44), and Env (799-813), on the one hand, and the complement components C2 (415-424), C4 (1443-1450), and C6 (378-392), on the other (Table 2), correlate with the hypothesis that auto-antibodies to immunoglobulins and proteins of the complement system, emerging during HIV infection, may disturb normal regulation of immune processes (Cavacini et al, 1999;Marchalonis et al, 1999).…”