Potent Human Immunodeficiency Virus-Neutralizing and Complement Lysis Activities of Antibodies Are Not Obligatorily Linked

Abstract

To evaluate the contribution of complement-mediated lysis to the in vivo activities of neutralizing antibodies, we analyzed the influence of complement activation on treatment success in a recent passive immunization trial with the neutralizing monoclonal antibodies 2G12, 2F5, and 4E10. Administration of monoclonal antibodies led to an immediate, high activation of the complement system even in the absence of viremia in the 14 participating human immunodeficiency virus-infected individuals. Lysis activity measured in patient plasma increased during passive immunization; however, the increases were modest and only partially attributable to the administration of antibodies. We found that unlike neutralization activity, lysis activity was not associated with treatment success in this trial. Compared to complement lysis mounted by the polyclonal antibody response in vivo, monoclonal antibodies were weak inducers of this activity, suggesting that polyclonal responses are more effective in reaching the required threshold of complement activation. Importantly, strong neutralization activity of the monoclonal antibodies did not predict complement lysis activity against patient and reference viruses, suggesting that these activities are not linked. In summary, our data support the notion that the in vivo activities of 2G12, 2F5, and 4E10 are likely due to direct neutralization or Fc receptor-mediated mechanisms such as phagocytosis and antibody-dependent cellular cytotoxicity.

Variation in innate immunity in relation to ectoparasite load, age and season: a field experiment in great tits (Parus major)

“…Since we measured NAb-mediated complement activation, which is one of the pathways for the activation of complement, cell lysis by the complement system may be necessarily delayed compared with upregulation of NAb production. Despite concerns that lysis titres might not always reflect complement activity in plasma, but rather result from antibody-mediated cytotoxicity (Huber et al, 2008), the nonsignificant correlation between agglutination and lysis titres suggests the opposite. Additionally, even if lysis titres would not accurately reflect complement activity, associations between lysis titres and the annual cycle (Buehler et al, 2008), body mass differences among nestlings (Parejo et al, 2007) and parasite abundance (Parejo and Silva, 2009) suggest that lysis titres are biologically relevant.…”

Complement, Fc receptors and antibodies: a Trojan horse in HIV infection?

“…Evidence is provided that CoML contributes mainly at early stages of HIV infection to control viremia in vivo [4,6]. However, even in optimized experimental settings, HIV is only partially lyzed [22,23,24 ]. What are responsible for this intrinsic resistance to CoML are host cell-derived proteins that HIV acquires during the budding process [25].…”

HIV-Specific Antibody Responses in HIV-Infected Patients: From a Monoclonal to a Polyclonal View

“…Calcein release-based antibody-dependent complement-mediated lysis assay Complement-dependent microtoxicity assay [28][29][30] ADCC ADCC-GranToxiLux assay; rapid fluorometric ADCC assay [31,32] Ab-dependent NK cell activation Intracellular cytokine staining; NK cell degranulation [33] Ab-dependent cellular phagocytosis THP-1 phagocytosis assay [34] Ab = Antibody; ADCC = antibody-dependent cellular cytotoxicity; Ag = antigen; Env = envelope; NK = natural killer. 1 Performed with single proteins and peptides (√) or overlapping peptide panels (√√).…”

“…Virus neutralization Neutralization assay (reduction in luciferase reporter gene expression after single-round infection of reporter cell lines) [35] Virus capture Virus capture assay; infectious virus capture assay [28,29,42,43] Ab-dependent complement-dependent cytotoxicity…”

“…In fact, besides techniques that can be applied for the study of antibody responses in terms of simple binding to the antigen/epitope, there are also techniques that allow studying certain functions of the antibodies, such as neutralization, complement activation and antibody-dependent cellular cytotoxicity [14, [28][29][30][31][32][33][34] . In addition, several techniques were developed to generate monoclonal antibodies and to study immune complexes (e.g.…”