Infection-Enhancing and -Neutralizing Activities of Mouse Monoclonal Antibodies against Dengue Type 2 and 4 Viruses Are Controlled by Complement Levels

Abstract

Dengue viruses are distributed widely in the tropical and subtropical areas of the world and cause dengue fever and its severer form, dengue hemorrhagic fever. While neutralizing antibodies are considered to play a major role in protection from these diseases, antibody-dependent enhancement (ADE) of infection is an important mechanism involved in disease severity, in addition to the involvement of T lymphocytes. Here, we analyzed relationships between neutralizing and enhancing activities at a clonal level using models of dengue type 2 virus (DENV2) and dengue type 4 virus (DENV4). Totals of 33 monoclonal antibodies (MAbs) against DENV2 and 43 against DENV4 were generated, all directed to the envelope protein. In these MAbs, enhancing activities were shown at subneutralizing doses under normal ADE assay conditions where test samples were heat inactivated. However, the inclusion of commercial rabbit complement or fresh sera from healthy humans in the ADE assay system abolished the enhancing activities of all these MAbs. The reductive effect of fresh sera on enhancing activities was significantly reduced by their heat inactivation or the use of C1q-or C3-depleted sera. In some fresh sera, enhancing activities were shown within a range of 20 to 80% of normal complement levels in a dose-dependent fashion. These results indicate that a single antibody species possesses two distinct activities (neutralizing/enhancing), which are controlled by the level of complement, suggesting the involvement of complement in dengue disease severity. Fresh human sera also tended to reduce enhancing activities more effectively in homologous than heterologous combinations of viruses (DENV2/DENV4) and MAbs (against DENV2/DENV4).

Functional Analysis of Antibodies against Dengue Virus Type 4 Reveals Strain-Dependent Epitope Exposure That Impacts Neutralization and Protection

“…A study by Morens et al (40) produced 19 mouse MAbs against DENV-4 (strain 4328-S): only one (UH-6C3) was serotype specific and strongly neutralizing (PRNT 50 of ϳ50 ng/ ml), and no additional functional testing was performed with different DENV-4 strains. Forty-three MAbs against DENV-4 (strain H-241) were generated by Yamanaka et al (41): only two were serotype specific (D4-II-12B2 and D4-I-11D11) and neutralizing, and no strain dependence or mapping was performed. Two typespecific anti-DENV-4 chimpanzee MAbs (5D9 and 5H2) were generated after immunization with DENV-4 (strain 814669; Caribbean); these MAbs inhibited infection of the homologous strain (PRNT 50 of 580 and 240 ng/ml, respectively) (42).…”

“…While our laboratory and others have generated panels of inhibitory monoclonal antibodies (MAbs) that react specifically with DENV-1, DENV-2, or DENV-3, to date, remarkably few strongly neutralizing type-specific anti-DENV-4 MAbs have been reported: these include three unmapped mouse MAbs (UH-6C3, D4-II-12B2, and D4-I-11D11) (40,41), two chimpanzee MAbs (5D9 and 5H2), one of which is localized to an epitope in domain I of the E protein (42,43), and one human MAb DV22.3, which recognizes an epitope in DI-DII (44). In the current study, we developed a panel of 81 new DENV-4 mouse MAbs and examined their neutralization potentials initially against a genotype II strain (DENV-4 1036; Indonesia 1976) that was used for immunization.…”

Correlation between Complement Component Levels and Disease Severity in Dengue Patients in Indonesia

“…The results of a previous in vivo study sug-gested that the C1q level is correlated with disease severity in dengue patients (40). Recent in vitro studies have demonstrated that the presence of C1q in the assay system affects the ADE activities of anti-dengue antibodies (16,17), suggesting an important role of C1q in the ADE phenomenon. In addition, increased levels of immune complexes have been reported in dengue patients (41), and these result in the activation of C1q.…”

“…Mehlhop et al demonstrated that levels of the complement component C1q were correlated with enhancing activities in in vitro models of dengue type 1 virus and West Nile virus (WNV), depending on the IgG subclass of antibody (16). Moreover, our previous study revealed that monoclonal antibodies against dengue type 2 and type 4 viruses possess both enhancing and neutralizing activities, depending on the complement activity levels in the assay system (17).…”

COBRA-Based Dengue Tetravalent Vaccine Elicits Neutralizing Antibodies Against All Four Dengue Serotypes

“…Antibodies of the IgG2a/c and IgG2b subclass fix complement proteins C1q and C3 and can opsonize and inhibit dengue virus infection [47][48][49]. However, IgG2a/c binds FcgRI with high avidity, facilitating enhanced uptake of virus-antibody complexes by macrophages via antibody dependent enhancement (ADE).…”