A mosquito’s saliva contains hundreds of proteins that can cause disruption of the human immune system that can be detected for days after the immune response, according to findings published this week in PLOS Neglected Tropical Diseases.
Previous research has shown that properties of a mosquito bite can exacerbate some diseases. Studies in mice have revealed infections caused by a mosquito bite are often more severe than those caused by needle injection.
In the current study, a humanized mouse model was created by engrafting mice with human hematopoietic stem cells. The mice were bitten by four mosquitos uninfected with any pathogen on their footpads. A combined approach of flow cytometry and multiplex cytokine bead array assays, with detailed statistical analyses, were used to detect small, but significant variations in immune cell functions.
After getting bitten, the humanized mice showed multiple types of human immune response, with altered Th1 and Th2 helper cells and an increased cytokine level. Elevated levels of natural killer T cells, natural killer cells, CD8+ T cells, monocytes, and macrophages were also observed. The changes in immune response lasted up to 7 days post-bite and could be seen in multiple tissue types.
According to the authors, this is the first study to measure human immune responses in whole animals bitten by living mosquitos, rather than incomplete models and salivary glands extracted from mosquitos. These results could have implications for study of the effect of insect saliva on the human immune system, with or without pathogen transmission and could inform future vaccination programs.
Image: Mosquito spit may affect your immune system for days. Image courtesy of Rico-Hesse et al, 2018.