Research on vaccines against trypanosomatids, a family of protozoa that cause neglected tropical diseases, such as Chagas disease, leishmaniasis, and sleeping sickness, is a current need. Today, according to modern vaccinology, virus-like particle (VLP) technology is involved in many vaccines, including those undergoing studies related to COVID-19. The potential use of VLPs as vaccine adjuvants opens an opportunity for the use of protozoan antigens for the development of vaccines against diseases caused by Trypanosoma cruzi, Leishmania spp., and Trypanosoma brucei. In this context, it is important to consider the evasion mechanisms of these protozoa in the host and the antigens involved in the mechanisms of the parasite–host interaction. Thus, the immunostimulatory properties of VLPs can be part of an important strategy for the development and evaluation of new vaccines. This work aims to highlight the potential of VLPs as vaccine adjuvants for the development of immunity in complex diseases, specifically in the context of tropical diseases caused by trypanosomatids.

This chapter aims to present and discuss the main cell culture techniques used for the growth and maintenance of the different evolutionary forms of the protozoan Trypanosoma cruzi, the etiologic agent of the Chagas disease. Chagas disease is a neglected tropical disease endemic in several Latin American countries. Here, we intend to present the main difficulties, advantages, and disadvantages of using Trypanosoma cruzi cell culture in parasitic biology. Finally, we present the main research opportunities in the context of Trypanosoma cruzi parasitic biology using cell culture techniques, such as drug development, characterization of pharmacological targets, molecular markers for diagnosis, structural biology, and many other biomedical applications.

The cGAS-STING (cyclic GMP-AMP synthase-Stimulator of Interferon Genes) pathway is a central axis of innate immunity, sensing cytosolic double-stranded DNA of microbial or endogenous origin. Upon DNA recognition, cGAS synthesizes cyclic GMP-AMP (cGAMP), which binds STING at the endoplasmic reticulum and drives its translocation to the Golgi, where TBK1 recruitment and IRF3 phosphorylation induce type I interferons (IFN-I) and NF-ĸB-dependent pro-inflammatory cytokines. Aberrant activation by endogenous nucleic acids, arising from DNA damage, mitochondrial dysfunction, retrotransposable elements, or defective cytosolic nucleases, underlies an expanding group of monogenic type I interferonopathies. Gain-of-function STING1 variants cause STING-associated vasculopathy with onset in infancy (SAVI); TREX1, RNASEH2A/B/C, and SAMHD1 variants cause Aicardi-Goutières syndrome; and COPA, ATAD3A, and USP18 variants have emerged as causes of other rare systemic interferonopathies. This chapter examines the molecular mechanisms of pathological cGAS-STING activation in Mendelian disease, including defects in nucleic acid sensing, mitochondrial homeostasis, DNA repair, and immune regulation. We discuss genotype-phenotype correlations, diagnostic biomarkers such as the interferon-stimulated gene (ISG) signature and circulating IFN-α, diagnostic challenges, and therapeutic advances, particularly JAK inhibitors (baricitinib, ruxolitinib) and emerging STING-targeted strategies. Integrating molecular biology with clinical perspectives, the chapter highlights cGAS-STING as a major advance in translational medicine for rare diseases.