Vasculitis induced by immunization with Bacillus Calmette-Guérin followed by atypical mycobacterium antigen: a new mouse model for Kawasaki disease

Emerging evidence of microbial infection in causing systematic immune vasculitis in Kawasaki disease

Kawasaki disease (KD) is a systematic vasculitis that is often complicated by coronary artery lesions and is a leading cause of acquired heart disease in developed countries. Previous studies have suggested that genetic susceptibility, together with an inducing infectious agent, could be involved in KD pathogenesis; however, the precise causative agent of this disease remains unknown. Moreover, there are still debates concerning whether KD is an infectious disease or an autoimmune disease, although many studies have begun to show that various pathogens functioning as critical inducers could activate different kinds of immune cells, consequently leading to the dysfunction of endothelial cells and systematic vasculitis. Here in this review, we attempt to summarize all the available evidence concerning pathogen infections associated with KD pathogenesis. We also discuss the related mechanisms, present a future perspective, and identify the open questions that remain to be investigated, thereby providing a comprehensive description of pathogen infections and their correlations with the host immune system in leading to KD.

Pathogens in Vasculitis: Is It Really Idiopathic?

Vasculitis is an autoimmune disease characterized by the infiltration of leukocytes in blood vessels. An increasing number of studies on human and animal models have implicated various microorganisms in the pathogenesis of vasculitis. Previous studies have shown the presence of infectious agents, including viruses, bacteria, and fungi, in diseased vessels. However, despite continued research, the link between infection and vasculitis is not fully understood, possibly owing to the lack of appropriate animal models that mirror human disease and the technical limitations of pathogen detection in blood vessels. Among the pathogen-induced animal models, Candida albicans water-soluble fraction (CAWS)-induced coronary arteritis is currently considered one of the representative models of Kawasaki (KD) disease. Advances in metagenomic next-generation sequencing have enabled the detection of all nucleic acids in tissue, which can help identify candidate pathogens, including previously unidentified viruses. In this review, we discuss the findings from reports on pathogen-associated vasculitis in animal models and humans, with a specific focus on the investigation of the pathogenesis of vasculitis. Further studies on animal models and microbes in diseased vessels may provide important insights into the pathogenesis of vasculitis, which is often considered an idiopathic disease.

Epidemiology of Kawasaki disease before and after universal Bacille Calmette-Guérin vaccination program was discontinued

AIM

Bacille Calmette-Guérin (BCG) vaccine (BCG) has been suggested to induce the primary immunity needed for the subsequent Kawasaki disease (KD). We studied the epidemiology of KD before and after the universal BCG vaccination ended in Finland in September 2006.

METHODS

Kawasaki disease cases were retrieved from national health registries from 1996 to 2016 for annual incidence rates. We then compared 612 433 children born in the BCG vaccination era, from 1 January 1996 to 30 August 2006, to 604 163 born after BCG era, from 1 September 2006 to 31 December 2016.

RESULTS

The annual incidence rates did not change after the BCG vaccination stopped. We found 370 first visits for KD by children born in the BCG era and 341 after universal BCG vaccination ended. The mean age at diagnosis increased from 2.6 years to 3.0 years (95% CI-0.64 to -0.012, P = .04) and the proportion of children with Kawasaki disease under 5 years decreased from 87% to 81% (95% CI 1%-12%, P = .02).

CONCLUSION

Discontinuing the universal BCG vaccination programme did not change the incidence rates of KD. The increased age at diagnosis could suggest that the pathogenesis of KD may be associated with the immunological pathways primed by BCG immunisation.

BCG: a vaccine with multiple faces

BCG has been recommended because of its efficacy against disseminated and meningeal tuberculosis. The BCG vaccine has other mechanisms of action besides tuberculosis protection, with immunomodulatory properties that are now being discovered. Reports have shown a significant protective effect against leprosy. Randomized controlled trials suggest that BCG vaccine has beneficial heterologous (nonspecific) effects on mortality in some developing countries. BCG immunotherapy is considered the gold standard adjuvant treatment for non-muscle-invasive bladder cancer. BCG vaccine has also been tested as treatment for diabetes and multiple sclerosis. Erythema of the BCG site is recognized as a clinical clue in Kawasaki disease. BCG administration in the immunodeficient patient is associated with local BCG disease (BCGitis) or disseminated BCG disease (BCGosis) with fatal consequences. BCG administration has been associated with the development of autoimmunity. We present a brief review of the diverse facets of the vaccine, with the discovery of its new modes of action providing new perspectives on this old, multifaceted and controversial vaccine.

BCG and Kawasaki disease in Mexico and Japan

Dr. Tomisaku Kawasaki was the first to describe BCG reactivation in Kawasaki Disease (K_D), and this sign is present in about 30-50% of K_D patients. It is a very specific early sign of the disease and although it has been recognized for decades, its pathophysiology continues to be an enigma. Recently, Yamada et al. reported a severe BCG reaction with tuberculid in 2 Japanese K_D patients. We present 2 cases with K_D and severe BCG reaction, one from Japan and the other from Mexico and review the policies of administration of BCG in both countries. The BCG vaccine has a worldwide coverage of 88%. Differences in BCG strains and methods of administration may influence BCG reactions in K_D. The BCG reaction in the inoculation site may represent the most useful sign in K_D.

Recent Advances in Kawasaki Disease

Kawasaki disease (KD) is characterized with acute systemic vasculitis, occurs predominantly in children between 6 months to 5 years of age. Patients with this disease recover well and the disease is self-limited in most cases. Since it can lead to devastating cardiovascular complications, KD needs special attention. Recent reports show steady increases in the prevalence of KD in both Japan and Korea. However, specific pathogens have yet to be found. Recent advances in research on KD include searches for genetic susceptibility related to KD and research on immunopathogenesis based on innate and acquired immunity. Also, search for etiopathogenesis and treatment of KD has been actively sought after using animal models. In this paper, the recent progress of research on KD was discussed.

Characterization of the gut microbiota of Kawasaki disease patients by metagenomic analysis

Kawasaki disease (KD) is an acute febrile illness of early childhood. Previous reports have suggested that genetic disease susceptibility factors, together with a triggering infectious agent, could be involved in KD pathogenesis; however, the precise etiology of this disease remains unknown. Additionally, previous culture-based studies have suggested a possible role of intestinal microbiota in KD pathogenesis. In this study, we performed metagenomic analysis to comprehensively assess the longitudinal variation in the intestinal microbiota of 28 KD patients. Several notable bacterial genera were commonly extracted during the acute phase, whereas a relative increase in the number of Ruminococcus bacteria was observed during the non-acute phase of KD. The metagenomic analysis results based on bacterial species classification suggested that the number of sequencing reads with similarity to five Streptococcus spp. (S. pneumonia, pseudopneumoniae, oralis, gordonii, and sanguinis), in addition to patient-derived Streptococcus isolates, markedly increased during the acute phase in most patients. Streptococci include a variety of pathogenic bacteria and probiotic bacteria that promote human health; therefore, this further species discrimination could comprehensively illuminate the KD-associated microbiota. The findings of this study suggest that KD-related Streptococci might be involved in the pathogenesis of this disease.

Immunization with vaccines and Sjögren's syndrome

Sjögren's syndrome (SjS) is a systemic autoimmune disease with complex pathogenesis and still unknown etiology. Infections are listed among the main environmental factors triggering the disease in genetically predisposed individuals. Among other environmental factors, the role of immunization with vaccines in the etiopathogenesis of SjS has not yet been elucidated. Although immunization with vaccines is safe for the majority of subjects, in rare cases it can trigger or exacerbate autoimmune and rheumatic inflammatory conditions. In this paper we investigate the possible links between immunization with vaccines and the pathogenesis of SjS. The current scientific evidence about safety and efficacy of vaccines in the course of SjS are also reviewed.

A combination of cross correlation and trend analyses reveals that Kawasaki disease is a pollen-induced delayed-type hyper-sensitivity disease

Based on ecological analyses we proposed in 2003 the relation of Kawasaki Disease (KD) onset causing acute febrile systemic vasculitis, and pollen exposure. This study was aimed at investigating the correlation between pollen release and the change in the numbers of KD patients from 1991 to 2002 in Kanagawa, Japan. Short-term changes in the number of KD patients and medium- to long-term trends were analyzed separately. Short-term changes in the number of KD patients showed a significant positive cross correlation (CC) with 9- to 10-month delay following pollen releases, and a smaller but significant CC with 3- to 4-month delay. Further, a temporal relationship revealed by positive CC distribution showed that pollen release preceded KD development, suggesting that pollen release leads to KD development. A trend in patient numbers was fitted by an exponential curve with the time constant of 0.005494. We hypothesized that the trend was caused by the cumulative effects of pollen exposure for elapsed months on patients who may develop KD. By comparing the time constants of fitted exponential curve for each pollen accumulation period with 0.005494, the exposure period was estimated to be 21.4 months, which explains why approximately 50% of patients developed KD within 24 months from birth.

Subclinical arterial stiffness in young children after Kawasaki disease

BACKGROUND

Recent studies have revealed that atherosclerosis progresses faster than expected in young adults with a history of Kawasaki disease. However, it is unclear as to when these arterial changes become measurable. In this study, we evaluated subclinical arterial stiffness in young children with a history of Kawasaki disease using two-dimensional ultrasound speckle tracking.

METHODS

A total of 75 children with a history of Kawasaki disease (mean age, 8.2 ± 2.8 years) and 50 healthy controls (mean age 8.3 ± 3.5 years) were included. The two regions of interest for speckle tracking were manually positioned at the anterior and posterior carotid arterial wall using a Philips iE33 (Philips Medical Systems, Bothell, WA, USA). The peak systolic strain, time to peak systolic strain, early systolic strain rate, and late systolic strain rate were continuously monitored between the two regions of interest. Furthermore, the intimal-medial thickness, stiffness β, and pressure-elastic modulus, as conventional measures of arterial stiffness, were concurrently obtained.

RESULTS

The peak systolic strain and late systolic strain rate differed significantly between the patients with Kawasaki disease and controls (6.69% versus 8.60%, p < 0.01, and -0.28/second versus -0.51/second, p < 0.0001, respectively). There was no difference in the time to peak systolic strain, early systolic strain rate, and conventional measures.

CONCLUSIONS

The arteries of patients with Kawasaki disease appear to develop mild sclerotic changes shortly after the onset of the disease.

BCG and BCG/DNAhsp65 vaccinations promote protective effects without deleterious consequences for experimental autoimmune encephalomyelitis

A prime-boost strategy conserving BCG is considered the most promising vaccine to control tuberculosis. A boost with a DNA vaccine containing the mycobacterial gene of a heat shock protein (pVAXhsp65) after BCG priming protected mice against experimental tuberculosis. However, anti-hsp65 immunity could worsen an autoimmune disease due to molecular mimicry. In this investigation, we evaluated the effect of a previous BCG or BCG/pVAXhsp65 immunization on experimental autoimmune encephalomyelitis (EAE) development. Female Lewis rats were immunized with BCG or BCG followed by pVAXhsp65 boosters. The animals underwent EAE induction and were daily evaluated for weight loss and clinical score. They were euthanized during recovery phase to assess immune response and inflammatory infiltration at the central nervous system. Previous immunization did not aggravate or accelerate clinical score or weight loss. In addition, this procedure clearly decreased inflammation in the brain. BCG immunization modulated the host immune response by triggering a significant reduction in IL-10 and IFN-γ levels induced by myelin basic protein. These data indicated that vaccination protocols with BCG or BCG followed by boosters with pVAXhsp65 did not trigger a deleterious effect on EAE evolution.

Pathogenic characterization of a cervical lymph node derived from a patient with Kawasaki disease

Kawasaki disease (KD) is the most common cause of multisystem vasculitis in childhood. Although cervical lymphadenitis is one of the major symptoms in KD, lymph node biopsy is rarely performed, because KD is usually diagnosed by clinical symptoms. A cervical lymph node biopsy was taken from a girl aged 1 year and 8 months who had suspected lymphoma, but she was diagnosed with KD after the biopsy. The cervical lymph node specimen was analyzed with multivirus real-time PCR that can detect >160 viruses, and unbiased direct sequencing with a next-generation DNA sequencer to detect potential pathogens in the lymph node. Histologically, focal necrosis with inflammatory cell infiltration, including neutrophils and macrophages, was observed in the marginal zone of the cervical lymph node, which was compatible with the acute phase of KD. Multivirus real-time PCR detected a low copy number of torque teno virus in the sample. Comprehensive direct sequencing of the cervical lymph node biopsy sample sequenced more than 8 million and 3 million reads from DNA and RNA samples, respectively. Bacterial genomes were detected in 0.03% and 1.79% of all reads in DNA and RNA samples, respectively. Although many reads corresponded to genomes of bacterial environmental microorganisms, Streptococcus spp. genome was detected in both DNA (77 reads) and RNA (2,925 reads) samples. Further studies are required to reveal any association of microbial or viral infection with the pathogenesis of KD.

A novel anti-peroxiredoxin autoantibody in patients with Kawasaki disease

Antibodies to the anti-oxidative peroxiredoxin (Prx) enzymes occur in both systemic autoimmune disease and vasculitis in adulthood. Because increased oxidative stress induces vasculitis in Kawasaki disease (KD), autoimmunity to Prxs in patients with KD was investigated. The presence of antibodies to Prx 1, 2 and 4 was analyzed by ELISA and Western blot. Of 30 patients with KD, 13 (43.3%) possessed antibodies to Prx 2, whereas these antibodies were present in only 1 of 10 patients (10.0%) with sepsis (4 with purulent meningitis and 6 with septicemia). In contrast, antibodies to Prx 1 and 4 were not detected in either group. There was no significant correlation among the titers of the three antibodies. Clinical parameters were compared between anti-Prx 2-positive and -negative patients. The presence of anti-Prx 2 antibodies correlated with a longer period of fever and poor response to high-dose γ-globulin therapy in patients with KD. Anti-Prx 2-positive patients had significantly greater excretion of urinary 8-isoprostaglandin than did anti-Prx 2-negative patients. These results provide the first evidence for an antibody to Prx 2 in patients with KD. They also suggest that this antibody might serve as a marker of disease severity and be involved in the pathophysiology of vasculitis in some patients with KD.

Ischaemic colitis during interferon treatment for chronic hepatitis C: report of two cases and literature review

Ischaemic colitis is known to be a severe emergency complication of interferon (IFN) therapy. However, as ischaemic colitis is an infrequent complication of IFN therapy, limited information is available regarding the safety of resuming IFN therapy after resolution of ischaemic colitis and subsequent recurrence. Here, we report two cases of ischaemic colitis during IFN therapy for chronic hepatitis C. Ischaemic colitis was fully healed within 1 week after its onset and IFN withdrawal, and IFN therapy was resumed following patients' wishes to do so. Ischaemic colitis did not recur after the resumption of IFN therapy, and sustained virological response was achieved in both patients. In this report, we also summarize the findings of 11 cases of IFN-associated ischaemic colitis (nine previously published cases plus our two cases) and review the clinical characteristics of ischaemic colitis during IFN therapy in patients with chronic hepatitis C.