Antibody Cell Quality Separates Mild from Severe Dengue in Children

Dengue virus infects tens of millions of people each year, yet the course of illness remains strikingly unpredictable. Some children carry the virus with barely a symptom, while others with the same infection progress to hospitalization with severe plasma leakage and shock. A new study of Cambodian children infected with dengue virus suggests that part of the answer lies not in how much antibody the immune system produces, but in the quality and specificity of the antibody-secreting cells mobilized during the acute phase of infection.

The research, published in PLOS Pathogens, was led by Amandine Trouchet and colleagues working across institutes in France and Cambodia, including teams at the Institut Pasteur and the Institut Pasteur du Cambodge. The investigators set out to examine a question that has long frustrated dengue immunologists: which antibody features actually mediate protection in humans? Although dengue vaccines and monoclonal antibody therapies have been developed, the correlates of protection against severe disease remain poorly defined, in large part because the human antibody response to dengue is exceptionally complex.

That complexity stems from the structure of the virus itself. Dengue virus is coated with 180 copies of the envelope protein, known simply as E, which is the principal target of neutralizing antibodies. On the mature virion surface, E proteins are arranged as 90 homodimers, and this dimeric arrangement creates quaternary epitopes—antigenic surfaces that exist only when two E proteins are paired together. Antibodies that recognize these quaternary epitopes tend to be highly neutralizing and broadly reactive across the four dengue virus serotypes, whereas antibodies that bind only to isolated E monomers are frequently weakly neutralizing or even non-neutralizing, and in some contexts can contribute to antibody-dependent enhancement, the phenomenon in which pre-existing antibodies facilitate infection of cells by a different serotype.

To dissect the antibody response at the level of individual cells, the team turned to droplet-based microfluidics, a technology that allows thousands of single antibody-secreting cells to be captured and analyzed in parallel. Each cell is enclosed in its own microscopic droplet together with fluorescently labeled viral antigens, so that the antibodies secreted by that single cell can be imaged as they bind to the antigen in real time. Using this approach, the researchers profiled more than 3,300 individual IgG-secreting cells from pediatric patients enrolled in a Cambodian cohort, comparing children with subclinical dengue infections against those who were hospitalized with symptomatic disease.

The cohort was carefully structured to allow meaningful comparisons. The children had experienced either acute DENV1 or DENV2 infection, and the analysis focused on post-primary infections, meaning the patients were responding to dengue for at least the second time. This distinction matters because primary and secondary dengue infections generate qualitatively different antibody repertoires, and secondary infections carry a substantially higher risk of severe outcomes, a pattern thought to be driven in part by cross-reactive but poorly neutralizing antibodies generated during the first encounter with the virus.

The first major finding was quantitative. Hospitalized patients had significantly fewer IgG-secreting cells in their circulation than children with subclinical infections, despite the fact that the cells they did possess secreted IgG at comparable rates. Moreover, when the researchers calculated the frequency of dengue E-specific antibody-secreting cells as a proportion of the total IgG-secreting population, they found no significant difference between the two groups. In other words, the immune systems of hospitalized children were not failing to target dengue specifically; they were simply mounting a smaller overall antibody-secreting response, leaving fewer antigen-specific cells available to fight the infection.

The second finding concerned antibody affinity, a measure of how tightly an antibody binds its target. When the secreted antibodies from single cells were tested against the DENV1 envelope dimer, the antibodies from hospitalized patients showed a threefold lower average affinity than those from subclinical cases. Affinity matters enormously in antiviral defense: high-affinity antibodies neutralize virus more efficiently, persist longer in memory, and are more likely to mediate protective Fc-dependent functions. A threefold reduction across a population of antibody-secreting cells suggests that the germinal center reaction—the specialized structure in lymphoid tissue where B cells refine their antibodies through mutation and selection—was less effective in the children who went on to develop severe disease.

The most striking qualitative difference emerged when the researchers probed the specificity of the antibodies for quaternary epitopes. Because quaternary epitopes depend on the dimeric arrangement of E on the virion, antibodies that bind the E dimer but not the E monomer are considered quaternary-epitope-specific. When the team compared binding to dimeric versus monomeric E protein, they found that antibodies recognizing quaternary epitopes were detected exclusively in the subclinical group. Hospitalized patients, by contrast, predominantly produced monomer-reactive antibodies—antibodies that bind the envelope protein in isolation and therefore, by inference, are less likely to recognize the authentic viral surface with the precision required for potent neutralization.

Taken together, these results sketch a coherent picture of what distinguishes a protective dengue antibody response from a failing one. Children who weathered infection without hospitalization generated larger numbers of antibody-secreting cells, with higher average affinity for the envelope dimer and a clear representation of quaternary-epitope-specific clones. Hospitalized children produced fewer cells, of lower affinity, skewed toward monomer reactivity. The authors propose that dengue severity may be linked to the inefficient generation of sufficient numbers of high-affinity, broadly reactive antigen-specific IgG-secreting cells during post-primary infection, rather than to any single deficit in antibody quantity alone.

The study carries implications for vaccine design and for the long-standing effort to define immune correlates of protection against dengue. Vaccines that reliably elicit quaternary-epitope-specific, high-affinity antibodies—rather than merely high titers of cross-reactive monomer-binding antibodies—may better recapitulate the response pattern associated with subclinical outcomes. The single-cell microfluidic approach also offers a template for future studies, since it captures the true diversity of the antibody-secreting cell population rather than averaging signals across bulk serum. As the authors note, the antibody features that mediate protection in humans remain poorly defined, and this work in a well-characterized Cambodian pediatric cohort provides some of the clearest evidence yet that the monoclonal composition of the early antibody response, not just its magnitude, shapes the clinical trajectory of dengue virus infection.

Subject of Research: Anti-envelope IgG-secreting cell responses in subclinical versus hospitalized pediatric dengue virus infection

Article Title: Quantitative and qualitative differences in anti-Envelope IgG-secreting cells distinguish subclinical and hospitalized dengue in a Cambodian pediatric cohort

Article References: Trouchet, A., Lay, S., Broketa, M., Canales-Herrerias, P., Perima, A., Iannascoli, B., Sann, S., Heng, B., Ly, S., Duong, V., Millot, G. A., Walker, L., England, P., Barba-Spaeth, G., Cantaert, T., & Bruhns, P. (2026). Quantitative and qualitative differences in anti-Envelope IgG-secreting cells distinguish subclinical and hospitalized dengue in a Cambodian pediatric cohort. PLOS Pathogens, 22(10), e1014552. https://doi.org/10.1371/journal.ppat.1014552

Image Credits: AI Generated

DOI: 10.1371/journal.ppat.1014552

Keywords: dengue virus, IgG-secreting cells, envelope protein, quaternary epitopes, antibody affinity, microfluidics, Cambodia, pediatric cohort, PLOS Pathogens, antibody-dependent enhancement, DENV1, DENV2