Skin prick testing a better predictor than blood testing for the diagnosis of peanut allergy in Chinese children.

BACKGROUND: Peanut allergy is common in Chinese children, yet the most predictive diagnostic cut-offs for skin prick test (SPT) and blood testing in this population are unclear. OBJECTIVES: We aimed to determine the optimal cut-off values for whole-peanut SPT, specific IgE (sIgE) and component-resolved diagnostics (CRD) for Chinese children based on outcomes of open oral food challenges (OFC) to peanut. METHODS: We recruited ethnic-Chinese patients 1-18 years old who were suspected of having peanut allergy based on a history of reactions after exposure or sensitization although peanut naïve. Considering the AUC value of 0.8, 80% power and 5% level of significance with two tails, 26 patients were needed. Sensitivities, specificities, positive and negative predictive values, and receiver operating characteristic curves (ROCs) and their area-under-curves (AUCs) for SPT, peanut sIgE, and CRD were compared. RESULTS: Thirty-one subjects participated. Only SPT reached statistical significance (AUC 0.91, p = 0.0001), but not the other tests. Seven retrospective data were added to optimize the power. SPT remained to be the best predictor, followed by Ara h 2 sIgE (AUC 0.72, p = 0.02). An SPT wheal size of 3 mm and Ara h 2 sIgE of 0.14 kU(A)/L yielded the highest Youden's index. The specificity of SPT and Ara h 2 sIgE reached 94% at 6 mm and 0.74 kU(A)/L, respectively. Comparisons of ROCs revealed that SPT was significantly better than Ara h 2 sIgE (p = 0.03) and whole-peanut sIgE (AUC 0.61, p = 0.26). CONCLUSION: In Chinese children, SPT appeared to be the best predictor for peanut allergy, followed by Ara h 2 sIgE.

Loop-mediated isothermal amplification (LAMP): a versatile technique for detection of micro-organisms.

Loop-mediated isothermal amplification (LAMP) amplifies DNA with high specificity, efficiency and rapidity under isothermal conditions by using a DNA polymerase with high displacement strand activity and a set of specifically designed primers to amplify targeted DNA strands. Following its first discovery by Notomi et al. ( Nucleic Acids Res 28: E63), LAMP was further developed over the years which involved the combination of this technique with other molecular approaches, such as reverse transcription and multiplex amplification for the detection of infectious diseases caused by micro-organisms in humans, livestock and plants. In this review, available types of LAMP techniques will be discussed together with their applications in detection of various micro-organisms. Up to date, there are varieties of LAMP detection methods available including colorimetric and fluorescent detection, real-time monitoring using turbidity metre and detection using lateral flow device which will also be highlighted in this review. Apart from that, commercialization of LAMP technique had also been reported such as lyophilized form of LAMP reagents kit and LAMP primer sets for detection of pathogenic micro-organisms. On top of that, advantages and limitations of this molecular detection method are also described together with its future potential as a diagnostic method for infectious disease.

Paediatric case series of drug reaction with eosinophilia and systemic symptoms (DRESS): 12-year experience at a single referral centre in Hong Kong and the first reported use of infliximab.

Summary: DRESS (drug reaction with eosinophilia and systemic symptoms) is a rare but potentially life-threatening disorder characterized by fever, skin eruption, haematological abnormalities and multi-organ dysfunction after drug exposure. The pathophysiology is thought to be related to interactions between culprit drugs, viral reactivation and T-lymphocytes activation. We report 4 paediatric patients with DRESS who were treated at our centre over the past 12 years. Most cases improved after corticosteroids. Other immunosuppressive medications were attempted in refractory cases with varied outcomes. Patient 3 was the first reported case that involved the use of infliximab, a TNF-α inhibitor, for DRESS. Although clinical efficacy was not observed for this one patient, a previous study demonstrated that patients with DRESS, disease progression and HHV-6 reactivation had elevated pre-treatment TNF- α and IL-6 levels. Further research is needed to explore the role of these cytokines in DRESS.

Compound heterozygous mutations in TTC7A cause familial multiple intestinal atresias and severe combined immunodeficiency.

Familial multiple intestinal atresias is an autosomal recessive disease with or without combined immunodeficiency. In the last year, several reports have described mutations in the gene TTC7A as causal to the disease in different populations. However, exact correlation between different genotypes and various phenotypes are not clear. In this study, we report identification of novel compound heterozygous mutations in TTC7A gene in a Malay girl with familial multiple intestinal atresias and severe combined immunodeficiency (MIA-SCID) by whole exome sequencing. We found two mutations in TTC7A: one that destroyed a putative splicing acceptor at the junction of intron 17/exon 18 and one that introduced a stop codon that would truncate the last two amino acids of the encoded protein. Reviewing the recent reports on TTC7A mutations reveals correlation between the position and nature of the mutations with patient survival and clinical manifestations. Examination of public databases also suggests carrier status for healthy individuals, making a case for population screening on this gene, especially in populations with suspected frequent founder mutations.

Allergy in Hong Kong: an unmet need in service provision and training.

Many children in Hong Kong have allergic diseases and epidemiological data support a rising trend. Only a minority of children will grow out of their allergic diseases, so the heavy clinical burden will persist into adulthood. In an otherwise high-quality health care landscape in Hong Kong, allergy services and training are a seriously unmet need. There is one allergy specialist for 1.5 million people, which is low not only compared with international figures, but also compared with most other specialties in Hong Kong. The ratio of paediatric and adult allergists per person is around 1:460 000 and 1:2.8 million, respectively, so there is a severe lack of adult allergists, while the paediatric allergists only spend a fraction of their time working with allergy. There are no allergists and no dedicated allergy services in adult medicine in public hospitals. Laboratory support for allergy and immunology is not comprehensive and there is only one laboratory in the public sector supervised by accredited immunologists. These findings clearly have profound implications for the profession and the community of Hong Kong and should be remedied without delay. Key recommendations are proposed that could help bridge the gaps, including the creation of two new pilot allergy centres in a hub-and-spoke model in the public sector. This could require recruitment of specialists from overseas to develop the process if there are no accredited allergy specialists in Hong Kong who could fulfil this role.

Sequence analysis of the PIP5K locus in Eimeria maxima provides further evidence for eimerian genome plasticity and segmental organization.

Commercial flocks infected by Eimeria species parasites, including Eimeria maxima, have an increased risk of developing clinical or subclinical coccidiosis; an intestinal enteritis associated with increased mortality rates in poultry. Currently, infection control is largely based on chemotherapy or live vaccines; however, drug resistance is common and vaccines are relatively expensive. The development of new cost-effective intervention measures will benefit from unraveling the complex genetic mechanisms that underlie host-parasite interactions, including the identification and characterization of genes encoding proteins such as phosphatidylinositol 4-phosphate 5-kinase (PIP5K). We previously identified a PIP5K coding sequence within the E. maxima genome. In this study, we analyzed two bacterial artificial chromosome clones presenting a ~145-kb E. maxima (Weybridge strain) genomic region spanning the PIP5K gene locus. Sequence analysis revealed that ~95% of the simple sequence repeats detected were located within regions comparable to the previously described feature-rich segments of the Eimeria tenella genome. Comparative sequence analysis with the orthologous E. maxima (Houghton strain) region revealed a moderate level of conserved synteny. Unique segmental organizations and telomere-like repeats were also observed in both genomes. A number of incomplete transposable elements were detected and further scrutiny of these elements in both orthologous segments revealed interesting nesting events, which may play a role in facilitating genome plasticity in E. maxima. The current analysis provides more detailed information about the genome organization of E. maxima and may help to reveal genotypic differences that are important for expression of traits related to pathogenicity and virulence.

Effectiveness of inactivated COVID-19 vaccine CoronaVac in children aged less than 3 years old during Omicron wave in Hong Kong.

The COVID-19 pandemic has affected people of all ages worldwide. However, there is still no information on the vaccine effectiveness (VE) of inactivated COVID-19 vaccines in children aged less than 3 years old. This study highlighted that 2 doses of CoronaVac were effective in preventing COVID-19, with a VE of 83.1 %.

Field-based flow cytometry for ex vivo characterization of Plasmodium vivax and P. falciparum antimalarial sensitivity.

Ex vivo antimalarial sensitivity testing in human malaria parasites has largely depended on microscopic determination of schizont maturation. While this microscopic method is sensitive, it suffers from poor precision and is laborious. The recent development of portable, low-cost cytometers has allowed us to develop and validate a simple, field-optimized protocol using SYBR green and dihydroethidium for the accurate and objective determination of antimalarial drug sensitivity in freshly isolated Plasmodium vivax and Plasmodium falciparum.

Reliability of acute illness dihydrorhodamine-123 testing for chronic granulomatous disease.

BACKGROUND: Dihydrorhodamine (DHR) flow cytometric analysis is used to evaluate granulocyte oxidative bursts and is the test of choice for the diagnosis of chronic granulomatous disease (CGD). We present the clinical and DHR test profiles of five subjects assessed during and after acute illness. METHODS: This was a retrospective report of the findings of five out of a total of one hundred and seventeen patients, whose blood was sent to the laboratory for dihydrorhodamine-123 flow cytometry testing between January 2005 and December 2010. Using whole blood technique and stimulation using phorbol myristate acetate, the results of DHR were expressed as stimulation index and coefficient of variation of histograms of stimulated cells and compared with healthy controls. DHR tests were repeated when the patients had recovered and were clinically well. RESULTS: These five patients showed abnormal DHR test results during their acute illness, with a stimulation index (SI) lower (p = 0.009) and coefficient of variation (CV) higher (p = 0.009) than controls. The DHR profiles repeated when patients had recovered showed normalization of tests with no significant difference for SI (p = 0.602) and CV (p = 0.917) compared to controls. Wilcoxon Signed Rank tests showed a significant improvement in SI (p = 0.043) and CV (p = 0.043) upon recovery. On follow up, all five patients were well, with no further severe or atypical infections. CONCLUSIONS: DHR may be transiently abnormal during acute illness, and may therefore not be reliable when assessed during an acute illness. If these subjects had CGD, it would be of a hypomorphic variant that has not previously been described.

Plasmodium knowlesi circumsporozoite protein: genetic characterisation and predicted antigenicity of the central repeat region.

Circumsporozoite protein (CSP) central repeat region is one of the main target regions of the RTS,S/AS01 vaccine for falciparum infection as it consists of immunodominant B cell epitopes. However, there is a lack of study for P. knowlesi CSP central repeat region. This study aims to characterise the CSP repeat motifs of P. knowlesi isolates in Peninsular Malaysia. CSP repeat motifs of 64 P. knowlesi isolates were identified using Rapid Automatic Detection and Alignment of Repeats (RADAR). Antigenicity of the repeat motifs and linear B cell epitopes were predicted using VaxiJen 2.0, BepiPred-2.0 and BCPred, respectively. A total of 35 dominant repeat motifs were identified. The repeat motif "AGQPQAQGDGANAGQPQAQGDGAN" has the highest repeat frequency (n=15) and antigenicity index of 1.7986. All the repeat regions were predicted as B cell epitopes. In silico approaches revealed that all repeat motifs were antigenic and consisted of B cell epitopes which could be designed as knowlesi malaria vaccine.

Multiplicity of infection of Plasmodium knowlesi in Malaysia: an application of Pkmsp-1 block IV.

In Malaysia presently, the main cause of human malaria is by the zoonotic monkey parasite Plasmodium knowlesi. A previous study has suggested that the P. knowlesi merozoite surface protein 1 (Pkmsp-1) block IV to be a suitable multiplicity of infection (MOI) genotyping marker for knowlesimalaria. This study therefore aimed to investigate the usefulness of Pkmsp-1 block IV in assessing the MOI of P. knowlesi in clinical isolates from Malaysia. Two allele-specific PCR primer pairs targeting the two allelic families of block IV (T1 and T2) were designed, and used to genotype P. knowlesi in 200 blood samples (100 from Peninsular Malaysia and 100 from Malaysian Borneo). Results showed that the mean MOI in Malaysian Borneo was slightly higher as compared to Peninsular Malaysia (1.58 and 1.40, respectively). Almost half of the total blood samples from Malaysian Borneo (52%) had polyclonal infections (i.e., more than one allele of any family type) as compared to Peninsular Malaysia (33%) samples. The T1 allelic family was more prevalent in Peninsular Malaysia (n=75) than in Malaysian Borneo (n=60). The T2 allelic family, however, was more prevalent in the Malaysian Borneo (n=87 vs n=53 respectively). This study shows that the single locus Pkmsp-1 block IV can serve as a simple alternative genetic marker for estimating knowlesi malaria MOI in a population. Future MOI studies should focus on macaque populations as macaques are the natural host of P. knowlesi.

Exome sequencing identifies novel compound heterozygous mutations of IL-10 receptor 1 in neonatal-onset Crohn's disease.

Inflammatory bowel disease is well recognized for a strong genetic involvement in its pathogenesis. Homozygous mutations in interleukin-10 receptor 1 (IL-10R1) identified by linkage analysis were shown to be involved in this disorder. However, the underlying molecular mechanism and the causal nature of the mutations in the disease process remain to be clarified. In this study, using whole exome sequencing, we identified novel compound heterozygous missense mutations in the extracellular domain of IL-10R1 in a Crohn's disease patient from a non-consanguineous family. These mutations did not affect IL-10R1 expression, nor IL-10 binding. However, they abrogated IL-10R1 phosphorylation induced by IL-10, therefore leading to impaired STAT3 activation and suppression of inflammatory responses. After reconstitution with wild-type IL-10R1, the patient cells showed fully restored IL-10R function including IL-10-induced STAT3 activation and expression of suppressor of cytokine signaling 3. Thus, our results demonstrated that the mutations in IL-10R1 extracellular domain impair IL-10R1 activation rather than IL-10 binding, indicating these residues are important in IL-10 signal transduction through IL-10R1. The reconstitution data also confirmed the causality of the IL-10R1 mutations.

Association of CD247 with systemic lupus erythematosus in Asian populations.

OBJECTIVE: Systemic lupus erythematosus (SLE) is a prototypic autoimmune disease with complex genetic inheritance. CD247 (CD3Z, TCRZ) plays a vital role in antigen recognition and signal transduction in antigen-specific immune responses, and is known to be involved in SLE pathogenesis. Weak disease association was reported for genetic variants in this gene in Caucasian studies for SLE, Crohn's disease and systemic sclerosis, but its role as a genetic risk factor was never firmly established. METHODS: In this study, using a collection of 612 SLE patients and 2193 controls of Chinese ethnicity living in Hong Kong in a genome-wide study, single nucleotide polymorphisms (SNPs) in and around CD247 were identified as being associated with SLE. The two most significant SNPs in this locus were selected for further replication using TaqMan genotyping assay in 3339 Asian patients from Hong Kong, Mainland China, and Thailand, as well as 4737 ethnically and geographically matched controls. RESULTS: The association of CD247 with SLE in Asian populations was confirmed (rs704853: odds ratio [OR] = 0. 81, p = 2.47 × 10(-7); rs858543: OR = 1.10, p = 0.0048). Patient-only analysis suggested that rs704853 is also linked to oral ulcers, hematologic disorders and anti-double-stranded DNA (dsDNA) antibody production. CONCLUSION: A significant association between variants in CD247 and SLE was demonstrated in Asian populations. Understanding the involvement of CD247 in SLE may shed new light on disease mechanisms and development of new treatment paradigms.

Autonomic dysfunction in ischemic stroke with carotid stenosis.

OBJECTIVES: Impaired autonomic function is common in acute ischemic stroke. Previous limited studies have suggested that atherosclerosis may affect the distensibility of the carotid sinus and then impair the cardiovascular autonomic function. This study sought to investigate cardiovascular autonomic function in patients with ischemic stroke with carotid stenosis. METHODS: Eighty-five patients with ischemic stroke (58 ones without carotid stenosis and 27 ones with carotid stenosis, average 6 months after stroke onset) and 37 elderly controls were recruited. All performed Ewing's battery autonomic function tests. RESULTS: From Ewing's battery of autonomic function tests, atypical, definite, or severe autonomic dysfunction was identified in 69.0% patients without carotid stenosis and 88.9% with carotid stenosis, with significant difference between the two groups, and the prevalence of autonomic dysfunction in both groups was higher than that in controls (21.6%). Patients with carotid stenosis showed impairment of all parasympathetic tests (all P < 0.05) and one of the sympathetic tests [Mean fall in systolic blood pressure (BP) on standing: P = 0.051], and those without carotid stenosis only showed impairment in two parasympathetic tests (Valsalva ratio: P = 0.014; heart rate response to deep breathing: P < 0.001) in comparison with controls. Patients with carotid stenosis had significantly more impairment than those without carotid stenosis in some autonomic parameters (Valsalva ratio: P < 0.05; mean fall in systolic BP on standing: P < 0.05). CONCLUSIONS: Cardiovascular autonomic function is impaired in patients with ischemic stroke, but patients with carotid stenosis show more severely impaired parasympathetic and sympathetic functions.