Heart disease among Greenlandic children and young adults: a nationwide cohort study.

BACKGROUND: The incidences of heart disease (HD) and congenital heart disease (CHD) among Inuit in Greenland (GL) and Denmark (DK) are unknown. This study aims to estimate incidence rates (IRs) of HD and CHD among the young Inuit populations in Greenland and Denmark compared with rates among young non-Inuit populations in the same countries. METHODS: A register-based nationwide cohort including all individuals living in Greenland and Denmark from birth to age <40 years through 1989-2014 was formed. Ethnicity was considered Inuit/mixed if at least one parent was registered as being born in Greenland. Information on HD and CHD hospitalization was obtained from national inpatient registers using ICD-8 and ICD-10 codes. RESULTS: HD IR was lower among individuals living in Greenland compared with those living in Denmark, [73.35GL (95% confidence interval (CI) 68.07 to 79.03)] vs [88.07DK (95% CI 87.38 to 88.76)], whereas CHD IRs were almost similar in the two countries [IR 34.44GL (95% CI 30.89 to 38.40) vs IR 34.67DK (95% CI 34.24 to 35.10)]. Being of Inuit/mixed ethnicity was associated with an increased risk of both HD and CHD compared with non-Inuit in Greenland and Denmark [adjusted hazard ratio HD 2.07GL (95% CI 1.25 to 3.42)] and CHD [2.92GL (95% CI 1.34 to 6.38)]. CONCLUSION: HD IR was lower in individuals living in Greenland compared with individuals living in Denmark, whereas the CHD IRs were almost the same for both countries. However, the risk of HD including CHD was higher among individuals of Inuit/mixed ethnicity compared with non-Inuit in both countries, suggesting a role of ethnicity among children and younger adults.

Study of correlation between the NAT2 phenotype and genotype status among Greenlandic Inuit.

N-acetyltransferase 2 (NAT2) is the main enzyme metabolizing isoniazid and genotype-based treatment has been studied for years without becoming common practice. To investigate whether genotype-based isoniazid treatment is feasible in Greenland, we sequenced the coding sequence of NAT2 and determined the NAT2 enzyme-activity by caffeine test. No additional genetic variants were identified in the coding sequence of NAT2, so that genotype status in 260 study participants could be assessed by a well-established 7-SNP panel. Studying the enzyme activity by the ratio of the two caffeine metabolites AFMU and 1X in 260 participants showed a high rate of slow phenotypes with intermediate or rapid genotype. These misclassifications were mainly observed in urine samples with pH<3, a deviation from the standard protocol due to the field work character of the study, where immediate pH adjustment to pH=3.5 was not possible. We excluded these samples. For the remaining 143 individuals with pH>3, we observed a moderate level of discrepancies (19 of the 116 individuals with intermediate or rapid genotype status having a slow phenotype). Further investigation showed that drinking coffee and not tea or cola was the most important factor for high levels of both metabolites. The concordance between phenotype and genotype status with regard to slow metabolism supported the recommendation of lower isoniazid doses in individuals with slow genotype status in order to avoid liver injury, a frequent side effect. The phenotypical variation observed for individuals with intermediate or rapid genotype status warrants further research before increased dosing of isoniazid can be recommended.

Determinants of tuberculosis trends in six Indigenous populations of the USA, Canada, and Greenland from 1960 to 2014: a population-based study.

BACKGROUND: Tuberculosis continues to disproportionately affect many Indigenous populations in the USA, Canada, and Greenland. We aimed to investigate whether population-based tuberculosis-specific interventions or changes in general health and socioeconomic indicators, or a combination of these factors, were associated with changes in tuberculosis incidence in these Indigenous populations. METHODS: For this population-based study we examined annual tuberculosis notification rates between 1960 and 2014 in six Indigenous populations of the USA, Canada, and Greenland (Inuit [Greenland], American Indian and Alaska Native [Alaska, USA], First Nations [Alberta, Canada], Cree of Eeyou Istchee [Quebec, Canada], Inuit of Nunavik [Quebec, Canada], and Inuit of Nunavut [Canada]), as well as the general population of Canada. We used mixed-model linear regression to estimate the association of these rates with population-wide interventions of bacillus Calmette-Guérin (BCG) vaccination of infants, radiographic screening, or testing and treatment for latent tuberculosis infection (LTBI), and with other health and socioeconomic indicators including life expectancy, infant mortality, diabetes, obesity, smoking, alcohol use, crowded housing, employment, education, and health expenditures. FINDINGS: Tuberculosis notification rates declined rapidly in all six Indigenous populations between 1960 and 1980, with continued decline in Indigenous populations in Alberta, Alaska, and Eeyou Istchee thereafter but recrudescence in Inuit populations of Nunavut, Nunavik, and Greenland. Annual percentage reductions in tuberculosis incidence were significantly associated with two tuberculosis control interventions, relative to no intervention, and after adjustment for infant mortality and smoking: BCG vaccination (-11%, 95% CI -6 to -17) and LTBI screening and treatment (-10%, -3 to -18). Adjusted associations were not significant for chest radiographic screening (-1%, 95% CI -7 to 5). Declining tuberculosis notification rates were significantly associated with increased life expectancy (-37·8 [95% CI -41·7 to -33·9] fewer cases per 100 000 for each 1-year increase) and decreased infant mortality (-9·0 [-9·5 to -8·6] fewer cases per 100 000 for each death averted per 1000 livebirths) in all six Indigenous populations, but no significant associations were observed for other health and socioeconomic indicators examined. INTERPRETATION: Population-based BCG vaccination of infants and LTBI screening and treatment were associated with significant decreases in tuberculosis notification rates in these Indigenous populations. These interventions should be reinforced in populations still affected by tuberculosis, while also addressing the persistent health and socioeconomic disparities. FUNDING: Public Health Department of the Cree Board of Health and Social Services of James Bay.

The dynamics of immune responses to Mycobacterium tuberculosis during different stages of natural infection: A longitudinal study among Greenlanders.

OBJECTIVE: Understanding human immunity to Mycobacterium tuberculosis (Mtb) during different stages of infection is important for development of an effective tuberculosis (TB) vaccine. We aimed to evaluate immunity to Mtb infection by measuring immune responses to selected Mtb antigens expressed during different stages of infection over time and to observe sustainability of immunity. METHODS: In a cohort study comprising East Greenlanders aged 17-22 years (2012 to 2014) who had either; undetectable Mtb infection, ongoing or prior Mtb infection at enrolment, we measured immunity to 15 antigens over a one-year period. Quantiferon-TB Gold testing (QFT) defined Mtb infection status (undetected/detected). The eligible study population of East Greenlanders aged 17-22 years was identified from the entire population using the Civil Registration System. From the source population 65 participants were selected by stratified random sampling according to information on Mtb infection stage. Retrospective and prospective information on notified TB (including treatment) was obtained through the mandatory TB notification system and was used to characterise Mtb infection stage (ongoing/prior). Immunity to 15 antigens including two QFT antigens, PPD and 12 non-QFT antigens (representing early, constitutive and latent Mtb infection) was assessed by measuring immune responses using whole-blood antigen stimulation and interferon gamma measurement. RESULTS: Of 65 participants, 54 were considered Mtb-infected. Immunity to Mtb infection fluctuated with high annual risk of conversion (range: 6-69%) and reversion (range: 5-95%). During follow-up, five (8%) participants were notified with TB; neither conversion nor reversion was associated with an increased risk of progressing to TB. CONCLUSIONS: Our findings suggest that human immunity to natural Mtb infection over time is versatile with fluctuations, resulting in high levels of conversion and reversion of immunity, thus human immunity to Mtb is much more dynamic than anticipated. The study findings suggest future use of longitudinal assessment of immune responses when searching for TB vaccine candidate antigens.

Introducing the ESAT-6 free IGRA, a companion diagnostic for TB vaccines based on ESAT-6.

There is a need for an improved vaccine for tuberculosis. ESAT-6 is a cardinal vaccine antigen with unique properties and is included in several vaccine candidates in development. ESAT-6 is also the core antigen in the IFN-γ release assays (IGRA) used to diagnose latent infection, rendering IGRA tests unspecific after vaccination. This challenge has prompted the development of a companion diagnostic for ESAT-6 based vaccines, an ESAT-6 free IGRA. We screened a panel of seven potential new diagnostic antigens not recognized in BCG vaccinated individuals. Three highly recognized antigens EspC, EspF and Rv2348c were identified and combined with CFP10 in an ESAT-6 free antigen cocktail. The cocktail was prepared in a field-friendly format, lyophilized with heparin in ready-to-use vacutainer tubes. The diagnostic performance of the ESAT-6 free IGRA was determined in a cross-validation study. Compared IGRA, the ESAT-6 free IGRA induced a comparable magnitude of IFN-γ release, and the diagnostic performance was on par with Quantiferon (sensitivity 84% vs 79%; specificity 99% vs 97%). The comparable performance of the ESAT-6 free IGRA to IGRA suggests potential as companion diagnostic for ESAT-6 containing vaccines and as adjunct test for latent infection.

Host immunity to Mycobacterium tuberculosis and risk of tuberculosis: A longitudinal study among Greenlanders.

BACKGROUND: Human immune responses to latent Mycobacterium tuberculosis (Mtb) infection (LTBI) may enable individuals to control Mtb infection and halt progression to tuberculosis (TB), a hypothesis applied in several novel TB vaccines. We aimed to evaluate whether immune responses to selected LTBI antigens were associated with subsequent reduced risk of progression to TB. METHODS: We conducted a population-based cohort study in East Greenland (2012-2014) including individuals aged 5-31years. A personal identifier allowed follow-up in national registers including the TB notification register. Mtb infection was defined by a positive Quantiferon test. Immune responses to LTBI antigens were assessed by whole blood antigen stimulation and interferon gamma measurement. RESULTS: Among 978 participants, 67 previously had TB. LTBI antigen (Rv1284, Rv2659, Rv2660c) immune response prevalence was 18%, 50%, 2% among Mtb-infected and 7%, 40%, 4% among non-infected (Quantiferon negative) participants. Among 911 participants without prior notified TB, 31 were notified with TB during study follow-up. Immune responses to LTBI antigens were not associated with reduced risk of subsequent TB; Rv1284 HR 0.92 (95%CI 0.28-3.04), Rv2659 HR 1.05 (95%CI 0.51-2.13), Rv2660c HR 3.06 (95%CI 0.70-13.37). CONCLUSION: In this large population-based study, human immune responses to selected LTBI antigens were not found to be strongly associated with reduced risk of subsequent TB.

Determination of NAT2 acetylation status in the Greenlandic population.

N-acetyltransferase 2 (NAT2) is a well-studied phase II xenobiotic metabolizing enzyme relevant in drug metabolism and cancerogenesis. NAT2 activity is largely determined by genetic polymorphisms in the coding region of the corresponding gene. We investigated NAT2 acetylation status in 1556 individuals from Greenland based on four different single nucleotide polymorphism (SNP) panels and the tagging SNP rs1495741. There was good concordance between the NAT2 status inferred by the different SNP combinations. Overall, the fraction of slow acetylators was low with 17.5 % and varied depending on the degree of Inuit ancestry; in individuals with <50 % Inuit ancestry, we observed more than 25 % slow acetylators reflecting European ancestry. Greenland has a high incidence of tuberculosis, and individual dosing of isoniazid according to NAT2 status has been shown to improve treatment and reduce side effects. Our findings could be a first step in pharmacogenetics-based tuberculosis therapy in Greenland.