Infection-induced trained immunity: a twist in paradigm of innate host defense and generation of immunological memory

In contrast to adaptive immunity, which relies on memory T and B cells for long-term pathogen-specific responses, trained immunity involves the enhancement of innate immune responses through cellular reprogramming. Experimental evidence from animal models and human studies supports the concept of trained immunity and its potential therapeutic applications in the development of personalized medicine. However, there remains a huge gap in understanding the mechanisms, identifying specific microbial triggers responsible for the induction of trained immunity. This underscores the importance of investigating the potential role of trained immunity in redefining host defense and highlights future research directions. This minireview will provide a comprehensive summary of the new paradigm of trained immunity or innate memory pathways. It will shed light on infection-induced pathways through non-specific stimulation within macrophages and natural killer cells, which will be further elaborated in multiple disease perspectives caused by infectious agents such as bacteria, fungi, and viruses. The article further elaborates on the biochemical and cellular basis of trained immunity and its impact on disease status during recurrent exposures. The review concludes with a perspective segment discussing potential therapeutic benefits, limitations, and future challenges in this area of study. The review also sheds light upon potential risks involved in the induction of trained immunity.