A groundbreaking study led by Brazilian researchers has unveiled a startling discovery: individuals previously infected with the Zika virus are more susceptible to severe dengue symptoms upon subsequent infection with dengue. This susceptibility heightens the risk of hospitalization, shedding light on a pathogenic immune response known as "original antigenic sin." This revelation is crucial in shaping the development of a Zika vaccine.
Unraveling the Intricate Relationship between Zika and Dengue
The study, published in PLOS Neglected Tropical Diseases, reveals a unique mechanism behind the increased severity of dengue following a Zika infection. This mechanism contrasts from the one observed in consecutive dengue infections. It has been found that individuals with a prior Zika infection exhibit higher viral loads and inflammatory cytokine levels during a subsequent dengue infection. These signs point towards an excessive inflammatory response, potentially leading to tissue damage and hemorrhage.
The Role of Original Antigenic Sin
Original antigenic sin characterizes this type of immune response. It is a phenomenon where T-cells from a previous infection produce an excessive inflammatory response. The research, analyzing samples from 1,043 dengue patients in São José do Rio Preto, Brazil, found that previous dengue infection did not increase severity. This lack of increased severity is possibly due to the patients experiencing multiple infections. However, a prior Zika infection emerged as a significant aggravating factor.
The study's findings corroborate previous research conducted on children in Nicaragua, providing valuable insights for the development of a Zika vaccine. The type and timing of the Zika vaccine, possibly in conjunction with a dengue vaccine, need to be carefully considered to prevent exacerbation of diseases. Brazil's dengue caseload surpassed the total for 2022 by November 2023, with over 1.37 million cases. Zika cases numbered 4,773 probable and 1,725 confirmed during the same period. Both dengue and Zika are flaviviruses transmitted by Aedes aegypti mosquitoes, often difficult to diagnose due to their similar symptoms. Dengue poses a more severe threat, potentially causing hemorrhage and death, whereas Zika, although milder, poses significant risks to pregnant women and infants. This discovery underscores the importance of ongoing research and development of vaccines for both diseases.