Measles, mumps and rubella (MMR) used to be common childhood diseases until the advent of the MMR vaccine, which significantly reduced MMR cases worldwide. According to CDC, a single dose of the MMR vaccine is 93% effective against measles, 78% effective against mumps and 97% against rubella. However, in unprotected individuals, either due to vaccine non-responders or those with poor immunological memory over time, can still be at risk of MMR virus infection.
In this report, E Bartholomeus et al. attempts to study the transcriptomic signatures underlying differences in vaccine responses between individuals. 40 healthy individuals (between 20 and 30 years) whom have received at least one MMR vaccine dose earlier in life, were recruited. Whole blood was collected at days 0, 3 and 7 for whole blood transcriptomic analysis. Later time points of days 21, 150 and 365 was used to evaluate humoral responses to the vaccines (See schematic at top).
Subjects were categorised as: (a) High Ab: individuals with a relatively high Ab titer before vaccination that remained stable or further increased after vaccination (b) Low Ab: individuals with a relatively low Ab titer before vaccination that remained low after vaccination (c) Long response: individuals with a relatively low Ab titer before vaccination that increased after vaccination and stayed stable within the first year (d) Peak response: individuals with a relatively low Ab titer before vaccination that increased at day 21, and then decreased by day 150 and 365. Since 3 live-attenuated viruses are administered together, the analysis was stratified according to responses to each viruses as well.
Comparisons between categories yielded few differentially expressed genes (DEGs). Interestingly, the time comparisons per response group analysis showed that that individuals under the long response group had the most DEGs, as compared to the other categories, especially at day 7 post-vaccination. Pathway analyses reveal that most of these upregulated genes are related to the innate and humoral immune responses.