Early Activation of Immune Response Could Lead to Better Vaccines

Researchers at Albert Einstein College of Medicine of Yeshiva University have discovered a new first response mechanism that the immune system uses to respond to infection. The findings challenge the current understanding of immunity and could lead to new strategies for boosting effectiveness of all vaccines. The study, conducted in mice, was published online in the journal Immunity.

One way the immune system protects the body against microbes like bacteria and viruses is with memory CD8+ T cells, so named because they can remember the invading organisms. If someone is later infected by that same microbe, memory CD8+ T cells recognize the invaders and multiply rapidly, forming an army of cytotoxic T cells to hunt down and destroy the microbes and the cells theyve infected. This highly specific immune response forms the basis for most vaccinesbut it can take several weeks for them to prime the immune system to respond to real infections.

This new study shows that the immune system has another, faster method for responding to infections that could be exploited to produce faster-acting vaccines.

Our research has revealed that pathogen-specific memory CD8+ T cells are reactivated even before they recognize the antigen they previously encountered, says study leader Grégoire Lauvau, PhD, associate professor of microbiology and immunology at Einstein.

Lauvau and his colleagues found that this fast-acting immune response is orchestrated by a type of white cell called inflammatory monocytes. After the immune system detects an infection, it recruits monocytes to the affected tissues, where they release inflammatory signals called cytokines. Those inflammatory signals not only activate every memory CD8+ T cell that has previously encountered a pathogen but also stimulate the activation of natural killer cells, another type of white blood cell.

The result is a protective immunologic environment capable of defending against microbes of any kindviruses, bacteria or parasites. Only later do memory CD8+ T cells specific for that microbes antigen begin to multiply, enabling the immune system to launch its focused attack on that particular microbe.

Were not saying that recognizing the antigen is unimportant in the immune response, says Lauvau. You do need the antigen later on, to cause memory CD8+ T cells to multiply and to get full pathogen-specific protection. But it doesnt seem to be needed during the days immediately following re-infection, when this early form of immunity is operating.

Its too early to apply these findings clinically, Lauvau adds. For example, we still need to identify all of the cells and signaling molecules that are involved, and learn how and when the immune system switches from the first phase of protection to the second phase, where you have the antigen. But the important concept to take from this study is that it may be possible to improve vaccines by making this early, generalized immune response persist for a longer time until the later, targeted immune response kicks in.

The lead author of the paper, titled Inflammatory monocytes activate memory CD8+ T and innate NK lymphocytes independent of cognate antigen during microbial pathogen invasion is Saïdi MHoma Soudja, PhD, a postdoc in Lauvaus lab. Other contributors are Anne Ruiz, M.Sc. and Julien Marie, PhD at INSERM and Université de Lyon, Lyon, France.

The study was largely supported by grants from the National Institute of Allergy and Infectious Diseases (AI095835), part of the National Institutes of Health, and Einstein funds.

Source: Albert Einstein College of Medicine of Yeshiva University