Prevention Measures for COVID-19 and Changes in Kawasaki Disease Incidence.

BACKGROUND: Kawasaki disease is suspected to be triggered by previous infection. The prevention measures for coronavirus disease 2019 (COVID-19) have reportedly reduced transmission of certain infectious diseases. Under these circumstances, the prevention measures for COVID-19 may reduce the incidence of Kawasaki disease. METHODS: We conducted a retrospective study using registration datasets of patients with Kawasaki disease who were diagnosed in all 11 inpatient pediatric facilities in Yamanashi Prefecture. The eligible cases were 595 cases that were diagnosed before the COVID-19 pandemic (from January 2015 through February 2020) and 38 cases that were diagnosed during the COVID-19 pandemic (from March through November 2020). Incidence of several infectious disease were evaluated using data from the Infectious Disease Weekly Report conducted by the National Institute of Infectious Diseases. RESULTS: Epidemics of various infectious diseases generally remained at low levels during the first 9 months (March through November 2020) of the COVID-19 pandemic. Moreover, the incidence of COVID-19 was 50-80 times lower than the incidence in European countries and the United States. The total number of 38 cases with Kawasaki disease for the 9 months during the COVID-19 pandemic was 46.3% (-3.5 standard deviations [SDs] of the average [82.0; SD, 12.7 cases] for the corresponding 9 months of the previous 5 years. None of the 38 cases was determined to be triggered by COVID-19 based on their medical histories and negative results of severe acute respiratory syndrome coronavirus 2 testing at admission. CONCLUSION: These observations provide a new epidemiological evidence for the notion that Kawasaki disease is triggered by major infectious diseases in children.

Markedly elevated CD64 expression on neutrophils and monocytes as a biomarker for diagnosis and therapy assessment in Kawasaki disease.

OBJECTIVE: Kawasaki disease (KD) is the most commonly encountered inflammatory disease in children. However, its pathogenesis and diagnostic biomarkers have not been fully investigated. We examined the activation of neutrophils and monocytes in KD. METHODS: We studied the expression of the Fcγ-receptors CD64 and CD16 on neutrophils and monocytes in KD before and after the treatment with intravenous infusion of high dose immunoglobulin (IVIG). Bacterial infections were addressed as well. RESULTS: CD64 expression on neutrophils and monocytes was dramatically increased at the onset of KD flare-ups, but later decreased just after IVIG. Similarly, CD16-positive monocytes were observed at the onset and were less apparent after therapy. The addition of immunoglobulin did not block the expression of CD64 or CD16 in vitro. Serum G-CSF in the majority of patients, and IFN-γ in some patients, were elevated during flares but decreased after treatment. CONCLUSION: Our findings demonstrate that remarkable CD64 expression during KD flare-ups may serve as a biomarker for diagnosis. Evaluation of CD64 is also potentially useful for the determination of treatment efficacy in KD.

Markedly elevated CD64 expressions on neutrophils and monocytes are useful for diagnosis of periodic fever, aphthous stomatitis, pharyngitis, and cervical adenitis (PFAPA) syndrome during flares.

Periodic fever, aphthous stomatitis, pharyngitis, and cervical adenitis (PFAPA) syndrome is the most commonly encountered autoinflammatory disease in children, but its pathogenesis and diagnostic biomarkers are unknown. In this study, we examined the utility of CD64, a member of the Fcγ receptors, expressions on neutrophils and monocytes in diagnosing patients with PFAPA, along with other autoinflammatory diseases exhibiting periodic fever, and bacterial infections. Although CD64 was expressed at a similar level in the attack-free period of PFAPA and in controls, CD64 expressions on both neutrophils and monocytes were dramatically increased during attacks. Serum IFN-γ also increased in some PFAPA patients during flares, suggesting the involvement of T cell activation. Our findings demonstrate that remarkable CD64 expression during PFAPA flares serves as a potential biomarker for the diagnosis. We also suspect that IFN-γ, possibly from retention of activated T cells in peripheral tissues, increases CD64 synthesis in such cases.

Increased CD45RO+ CD62L+ CD4+ T-cell subpopulation responsible for Th2 response in Kimura's disease.

Kimura's disease is characterized by subcutaneous masses, eosinophilia, and markedly elevated serum immunoglobulin E, suggesting that T helper (Th)2 cells may play a role in the pathogenesis. We investigated Th2 cytokine synthesis by mononuclear cells and possible Th1/Th2 subpopulations in Kimura's disease. Peripheral blood samples were obtained from seven patients with Kimura's disease and CD4(+) T-cell subpopulations separated by CD45RO and CD62L were isolated. Purified cells were stimulated with PHA or anti-CD3 mAb, and the cytokine levels were measured by Cytometric Bead Array kit. Peripheral blood mononuclear cells in the majority of the patients produced Th2 cytokines such as interleukin (IL)-3, IL-4, IL-5, IL-13 or GM-CSF higher than those of controls. The ratio of CD45RO(+) CD62L(+) cells in CD4(+) T cells was increased in six out of seven patients compared to age-matched controls. Especially, patient 1 had remarkably increased levels of CD45RO(+) CD62L(+) population in CD4(+) T cells. In addition, IL-4 production levels by CD45RO(+) CD62L(+) CD4(+) T cells of patients 1 and 2 were higher than those of their CD45RO(+) CD62L(-) CD4(+) T cells, in the same manner as those by a normal control. Taken together, the synthesis of Th2 cytokines and CD62L-positive subpopulation in CD45RO(+) CD4(+) T cells, which may represent characteristics of Th2, are increased in patients with Kimura's disease, suggesting that deviation to Th2 may involve in pathogenesis of the disease.

Absence of memory B cells in patients with common variable immunodeficiency.

The molecular basis of common variable immunodeficiency (CVID) is unknown. To assess humoral immunity in CVID, we selected 24 patients with early or late onset of disease. X-linked agammaglobulinemia (XLA), X-linked hyper-IgM syndrome (XHIM), and non-XHIM were excluded based on clinical phenotype, assessment of the immune response, presence of Bruton's tyrosine kinase (Btk) in monocytes or platelets, and normal expression of CD40 ligand by activated T cells. The number of circulating B cells was within the normal range or reduced. IgD(-) CD27(+) memory B cells were markedly reduced or absent in all 24 patients and IgD(+) CD27(+) B cells were diminished in 8 patients. Circulating B cells from all 6 patients examined, including CVID patients with IgD(+) CD27(+) cells, failed to undergo somatic hypermutation in immunoglobulin-variable (V)-region genes, similar to cord blood B cells. B cells from CVID patients produced IgM and IgG, but not IgA upon the engagement of Ig receptor and CD40 in the presence of IL-2 and IL-10. B cells from all but 5 patients secreted IgE when stimulated by CD40 crosslinking in the presence of IL-4. The observation of defective memory B cells with abnormal cell marker expression and function demonstrates that naive CVID B cells including those expressing IgD(+) CD27(+), in analogy to cord blood and hyper-IgM syndrome B cells, may be responsible for their failure to differentiate into plasma cells and to produce high-affinity antibodies of different isotypes.

The different process of class switching and somatic hypermutation; a novel analysis by CD27(-) naive B cells.

The relationship between class switch recombination (CSR) and somatic hypermutation has been unclear. By using human CD27(-) naive B cells, we investigated the somatic hypermutation and producibility of immunoglobulins (Igs) that occur after CSR. Although neither adult CD27(-) nor cord blood B cells, which showed the unmutated Ig V-region genes, produced IgG, IgM, or IgA in response to conventional stimuli, they produced IgG and IgM but not IgA in the presence of Staphylococcus aureus Cowan strain (SAC) + interleukin-2 (IL-2) + IL-10 + anti-CD40 mAb + CD32 transfectants (CD40/CD32T). The naive B cells also produced IgE when combined with IL-4 + CD40/CD32T. In parallel with IgG production, the expression of mature gamma1 and gamma 2 transcripts was induced from naive B cells by the stimuli. The CD27 expression on human naive B cells was induced remarkably by CD40 signaling or B-cell receptor engagement, but somatic hypermutation could not be induced. The proliferation and differentiation into plasma cells were induced from naive B cells, whereas most of the plasma cells displayed very low levels of mutations in Ig V-region genes. CD27(-) naive B cells expressed activation-induced cytidine deaminase messenger RNA by the stimuli later than CD27(+) memory B cells. Our results demonstrate that CSR, but not noticeable somatic hypermutation, can be induced from CD27(-) naive B cells upon B-cell receptor engagement and CD40 signaling in cooperation with cytokines, suggesting that CSR and somatic hypermutation processes can occur independently, and the antibodies produced in this in vitro system are low-affinity antibodies.