The role of the immune response as a marker as well as a therapeutic tool for the diagnosis, treatment and prophylaxis of infectious diseases, is well ascertained and described, however, these concepts are continually evolving. In the diagnostic field, the research of a specific humoral immune response has been used for a long time. In fact, the seroconversion is considered as an important key for the determination of an occurred infection and vaccine efficacy. Recently, in addition to the classical investigation on the presence or absence of antibodies directed against specific antigens, the titer of specific antibodies, defined as an index, is gaining importance as a prognostic marker for certain infectious diseases. As an example, the introduction of the JCPyV-seropositivity, defined as the presence of specific anti-JCPyV antibodies, in the stratification of multiple sclerosis patients at the risk to develop progressive multifocal leukoencephalopathy.

The immune response is the key element to resolve an infection. For this reason, a therapeutic and prophylactic strategy for infectious diseases is usually based on immune-based approaches. In particular, prophylactic strategies are principally focused on the stimulation of a specific immune response against the pathogen, i.e., active immunization. On the other hand, immunotherapeutic strategies are based on the concept of passive immunization. In this case, immunoglobulins, obtained from sera of immune individuals or by the cloning of recombinant antibodies (usually antigen-specific monoclonal antibodies [mAbs]), are administered to protect a susceptible or infected host. In this regard, very recently, a cocktail of mAbs is being considered as a possible treatment of Ebola virus infections.

Recently, in the context of passive immunization, also the infusions of antigen-specific or engineered T-cells, as an alternative treatment for infectious diseases, are being considered. As an example, chimeric antigen receptor (CAR)-engineered T cells are increasingly gaining potential application also for the elimination of difficult-to-eradicate pathogens. In this regard, in the last few years, several CARs directed against different infectious agents, such as HIV, CMV, HBV, HCV, and A. fumigatus, have been described.

The aim of this Special Issue is to collate original research papers and review articles that underline the use of immune-based approaches for the diagnosis and therapy of infectious diseases as well as for the development of future and next generation prophylactic strategies.

Potential topics include but are not limited to the following:

• Immune-based diagnostic tools for infectious diseases
• New immune-based approaches as prognostic markers for infectious diseases
• Immunotherapeutic approaches against infectious diseases
• Anti-infective monoclonal antibodies and their engineering
• New prophylactic approaches against infectious diseases
• Adoptive T-cell therapy for infectious diseases
• Engineered and redirected T-cells for the treatment of infectious diseases