Epitope dynamics and antigenic shifts in dengue virus serotype 2 cosmopolitan genotype with structural changes in Bangladesh from 2017 to 2023

Why dengue’s changing face matters

Dengue fever, once seen mainly as a seasonal tropical illness, has become a year‑round threat in many parts of the world. Bangladesh experienced its worst dengue outbreak in 2023, with hundreds of thousands of infections and thousands of deaths. This study looks under the viral “hood” to see how one major form of dengue—called dengue virus serotype 2, cosmopolitan genotype—is changing in ways that may help it spread, dodge the immune system, and complicate vaccine efforts.

Tracking a fast‑moving virus

The researchers gathered over two thousand genetic sequences of this dengue strain from Bangladesh and other countries between 2017 and 2023. They focused on pieces of the virus that our immune system is most likely to recognize, known as epitopes—short stretches of protein that antibodies and immune cells latch onto. By comparing recent Bangladeshi viruses with earlier and global samples, they mapped exactly where the virus has changed over time and how common each change has become.

What changed during Bangladesh’s big outbreak

The team found striking shifts in 2023, the year of Bangladesh’s record outbreak. Certain mutations in the outer and inner structural proteins of the virus surged in frequency. For example, a change called K9R in the capsid protein and I164V in the envelope protein were rare or moderate in earlier years but became almost universal in 2023 Bangladeshi samples. Other mutations appeared or disappeared in non‑structural proteins that help the virus replicate and interact with host cells. Some of these changes were common both in Bangladesh and worldwide, while others—such as newly seen changes in NS4A, NS4B, and NS5 proteins—looked more like local adaptations specific to Bangladesh.

How shape‑shifting may fool the immune system

Beyond listing mutations, the study asked what these changes might mean for immune defense. Using computer tools, the authors predicted which viral segments are likely to be recognized by B cells (which make antibodies) and T cells (which coordinate and kill infected cells). They then modeled the three‑dimensional structures of these epitopes before and after mutation. Some mutations subtly tweaked the proteins, but others caused larger shifts in shape or altered a predicted “antigenicity” score, a proxy for how visible a region may be to the immune system. In several cases, an epitope that was previously scored as likely to trigger a response became less visible, while others became more noticeable, suggesting the virus is constantly adjusting how it is seen—or not seen—by our defenses.

Hidden weak spots that stay the same

Despite the virus’s rapid evolution, the analysis also uncovered a silver lining: several epitopes remained both structurally stable and consistently antigenic across years and locations. These conserved segments appeared in different viral proteins and were predicted to be recognized by multiple arms of the immune system. Because they changed little even as other regions mutated, they may represent “hard‑to‑escape” weak spots that future vaccines or therapies could safely target. The authors argue that focusing on such sites could help build vaccines that remain effective even as the virus continues to mutate.

What this means for future dengue control

For non‑specialists, the message is that the dengue virus in Bangladesh—and worldwide—is not standing still. Specific genetic tweaks in the dominant dengue type 2 strain may be helping it spread more efficiently and slip past existing immune protections, potentially reducing the impact of current or future vaccines designed against older versions of the virus. At the same time, the discovery of conserved, stable target regions offers a roadmap for designing more robust vaccines and diagnostics. Continued genetic surveillance and structural analysis of the virus can guide public health decisions and help anticipate, rather than merely react to, the next wave of dengue.

Citation: Alam, S., Tony, S.R., Khair, S. et al. Epitope dynamics and antigenic shifts in dengue virus serotype 2 cosmopolitan genotype with structural changes in Bangladesh from 2017 to 2023. Sci Rep 16, 11428 (2026). https://doi.org/10.1038/s41598-026-38446-2

Keywords: dengue virus evolution, DENV-2 cosmopolitan genotype, epitope mutations, immune evasion, vaccine design