In a study published in the journal Blood, Dr Ofer Levy and colleagues show that the newborn immune system functions differently than that of adults, but that one portion of the immune response is fully functional and can be harnessed to boost immunity in these tiny infants, possibly making infections like respiratory syncytial virus, pneumococcus, pertussis, HIV and rotavirus much less of a threat.
For about a decade it’s been known that people’s first line of defense against infection is a group of receptors known as Toll-like receptors (TLRs) on the surface of certain white blood cells. Functioning like an early radar system, TLRs detect the presence of invading bacteria and viruses and trigger production of “danger signals” – proteins known as cytokines that trigger other immune cells to mount a defense against the infection. People have 10 different kinds of TLRs, and Dr Levy’s team decided to examine how well they function in newborns by studying white blood cells from their cord blood.
The team found that one TLR, known as TLR8, triggered a robust immune response in a group of white blood cells (called antigen-presenting cells) that is crucial for vaccine responses. When TLR8 was stimulated by various agents that mimic viral antigens, the cells produced normal, adult levels of two key cytokines – TNF-alpha and IL-12 – and another immune-system stimulant, CD40.
“These findings suggest that agents that stimulate TLR8 could be used to enhance immune responses in newborns, perhaps as adjuvants given along with vaccines,” Dr Levy said. “We plan to test this approach in animals, and eventually in human babies.”
Dr Levy noted that the ability to vaccinate newborns – rather than wait until they reach two months of age – would provide important global health benefits. “From a global health perspective, if you can give a vaccine at birth, a much higher percentage of the population can be covered.”
Conceivably, TLR8 stimulators could also be given alone in special circumstances – to help a baby fight off an infection in progress, or as a preventive measure in the event of a disease outbreak or bio-terrorist threat.