SUMMARY Tick-borne viral infections have emerged as a significant and growing public health concern. In East Asia, severe fever with thrombocytopenia syndrome (SFTS) has served as a prototypical disease in which pathological analyses have substantially advanced the understanding of disease pathogenesis. SFTS is characterized by profound immune dysregulation driven by viral tropism for plasmablast-lineage B cells, leading to cytokine storm and hemophagocytic syndrome. Complementary analyses of human clinical specimens and experimental animal models, including cats and ferrets, have provided critical insights into the immunopathogenesis of SFTS. The recent identification of additional tick-borne viruses, including Oz virus (OZV), Yezo virus (YEZV), and Alongshan virus (ALSV), has further expanded the spectrum of emerging infections in this region. Notably, pathological investigation of a fatal human case of OZV infection demonstrated direct viral localization within cardiomyocytes, establishing a causal link between infection and fulminant myocarditis and highlighting a distinct organ-specific pathogenic mechanism. Despite the advances in genomic technologies that enable rapid detection of novel viruses, establishing causal relationships between viral presence and disease remains a major challenge. Tissue-based pathological approaches, particularly in situ localization of viral components, are, therefore, essential for defining disease mechanisms and confirming etiological roles. This review provides a comprehensive synthesis of tick-borne viral infections in East Asia, with particular emphasis on Japan, integrating pathological, virological, and clinical perspectives. It also identifies key knowledge gaps and underscores the importance of a synergistic One Health framework that incorporates both human and veterinary pathology to advance the understanding and control of these emerging diseases.
SARS-CoV-2 vaccination and infection generate diverse immune histories, but antibody waning beyond 1 year remains insufficiently characterized. We estimated 2-year antibody trajectories and antibody-associated protection across different combinations of vaccination and infection history. We conducted a repeated cross-sectional study using four nationwide seroepidemiological surveys of 25,800 adults in Japan between December 2021 and March 2023. We measured total antibodies against the ancestral spike receptor-binding domain and neutralizing antibody titers against Omicron BA.5. Bayesian hierarchical models estimated antibody waning according to vaccine dose number, infection history, Omicron-adapted bivalent vaccination, age, sex, and vaccine product. Antibody trajectories were linked to an antibody-risk model to estimate protection against symptomatic infection. Here we show that, among uninfected individuals, three to five vaccine doses produce higher anti-spike antibody titers than two doses, while antibody kinetics after the third or later doses are broadly similar. Relative to titers 30 days after the third dose, titers in the three-, four-, or five-dose groups decline to 0.18-fold (95% credible interval [CredI], 0.16–0.19), 0.19-fold (95% CredI, 0.13–0.26), or 0.21-fold (95% CredI, 0.13–0.33) at 1 year and 0.10-fold (95% CredI, 0.07–0.14), 0.14-fold (95% CredI, 0.06–0.24), or 0.14-fold (95% CredI, 0.05–0.29) at 2 years. Omicron breakthrough infection is associated with higher and more durable anti-spike and BA.5 neutralizing antibody titers than vaccination alone. Based on anti-spike antibody trajectories, estimated 90% protection against symptomatic BA.5 infection lasts 99 days (95% CredI, 89–108) after three doses and 116 days (95% CredI, 111–121) after four or five doses in uninfected individuals, but 276 days (95% CredI, 245–319) to 450 days (95% CredI, 343 to >730) in Omicron-infected individuals. Hypothetical neutralization-escape scenarios substantially shorten estimated protection. These findings provide a quantitative framework for evaluating long-term antibody waning and booster timing across populations with diverse immune histories, and may inform the development of next-generation vaccination strategies that induce broader, more durable antibody responses against circulating SARS-CoV-2 variants.
K. Numakura, Sho Miyamoto, A. Sataka et al.· Communications Health· 0 citations
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