The Kynurenine Pathway is Differentially Activated in Children with Lyme Disease and Tick-Borne Encephalitis

Kynurenine Metabolites in CSF and Plasma in Healthy Males

In recent years, kynurenine metabolites generated by tryptophan catabolism have gained increasing attention in the context of brain diseases. The question of importance is whether there is a relationship between peripheral and central levels of these metabolites. Some of these compounds do not cross the blood-brain barrier; in particular, kynurenic acid, and most analyses of kynurenines from psychiatric patients have been performed using plasma samples. In the present study, we recruited 30 healthy volunteers with no history of psychiatric or neurological diagnosis, to analyze tryptophan, kynurenine, kynurenic acid, and quinolinic acid levels in CSF and plasma. In addition, kynurenic acid was analyzed in urine. The most important finding of this study is that CSF kynurenic acid levels do not correlate with those in plasma or urine. However, we found a correlation between plasma kynurenine and CSF kynurenic acid. Further, plasma kynurenine and plasma quinolinic acid were correlated. Our findings clarify the distribution of tryptophan and its metabolites in various body compartments and may serve as a guide for the analysis of these metabolites in humans. The most significant finding of the present study is that a prediction of brain kynurenic acid by of the analysis of the compound in plasma cannot be made.

Tick-borne encephalitis in pediatrics: An often overlooked diagnosis

Tick-borne encephalitis (TBE) is a vector-borne disease caused by a flavivirus, the tick-borne encephalitis virus (TBEV), and transmitted by the bite of infected Ixodes ricinus ticks. The European subtype (TBEV-Eu) is endemic in 27 European countries. During the last decade, increased TBE incidence was observed in many countries, including some of those believed to be of low endemicity/devoid of TBEV circulation. However, data dealing with TBE in children are far less profuse than with adults. Historically, children are known to have mild TBEV infection with favorable outcomes. That said, recent case reports and observational studies on pediatric cohorts have challenged this point of view. Like adults, children may present severe forms and fail to completely recover following TBE infection, at times leading to long-term cognitive impairment. In this review, we comprehensively describe the incidence, exposure factors, and transmission routes of TBEV in children, as well as the clinical and biological manifestations of TBE and imaging findings in this population. We also harness new data on long-term outcomes and sequelae in pediatric cohorts. Finally, we provide an overview of vaccination recommendations for children in European countries.

Tick-borne encephalitis epidemic in Hungary 1951-2021: The story and lessons learned

The authors analysed epidemiological data of the Hungarian tick-borne encephalitis epidemic from the past seven decades. A total of 911 meningitis serosa cases were described from 1930-1950 s by local hospital physicians, indicating that the virus had been present in the country decades before its official identification in 1952. The virus spread freely in the 1950s-1960s, occupying almost all habitats where ticks occurred in large numbers. The increasing number of cases drove authorities to classify this illness as a notifiable disease in 1977 and to organize the first measures to stop the epidemic. Statistical analysis revealed that the large-scale vaccination launched from the 1990s was responsible for the sharp decrease in the number of human cases from 1997. A significant negative correlation was found between the number of vaccine doses sold and human cases 6 years later. The TBEV endemic area covers 16.57% of the territory and 16.65% of the population of the country. In the last 10 years, 186,000 vaccine doses/year in average were enough to keep the incidence of human TBEV infections between 0.45 and 0.06/100,000 persons. A 20-year-long study found evidence for easing clinical signs in TBEV-infected hospitalized patients. Statistics found a sharp decrease in the number of samples sent for TBEV diagnosis after 1989. Male dominance of patients was characteristic of the epidemics since the 1940s, but now analysis of detailed data from the 1981-2021 period (60.5%-87.5%) proved the statistical significance of this dominance. Obviously, the voluntary vaccination programme was the tool which broke the spread of the epidemic. Widespread public awareness of the disease and the tick vector, probable evolutionary spread of less pathogenic virus strains supplemented with the vaccination campaign led to a negligible level of human TBE cases in Hungary in the last years.