Feasibility and Reaction Thresholds of Double-Blind, Placebo-Controlled Peanut and Nut Food Challenges Using Gingerbread Matrix.

INTRODUCTION: Double-blind, placebo-controlled food challenges are an important tool in diagnosing food allergies. PRACTALL recommends a dose-escalation schedule of 3-3,000 mg of food protein and a top dose of at least 2,000 mg to avoid false-negative results. This retrospective observational study tests the thresholds and feasibility using a previously published gingerbread matrix. METHODS: Data of food provocations with peanuts and nuts in children from 2015 to 2019 in the Reinier de Graaf Hospital were analyzed. We performed the food challenge following a schedule of 1, 3, 10, 30, 100, 300, 1,000, and 3,000 mg allergen protein. The feasibility of ingestion of the gingerbread matrix was determined by analyzing the amount of consumed gingerbread. RESULTS: 513 food challenges performed in 365 children (median age 6.9 years) were analyzed. Forty percent (204/513) of the food challenges were positive. Fifteen children already reacted at 1 mg protein (7%), 3 with a grade 3 reaction. The median cumulative amount of gingerbread matrix the children could eat on 1 day was 130.3 g. The median cumulative amount of allergen protein eaten was 2,585 mg; only 49% reached the minimum desired cumulative amount of 3,500 mg allergen protein. Despite that, there were no reported reactions at home in the 86% who introduced the allergen after a negative challenge. CONCLUSION: Seven percent of the children react on a starting dose of 1 mg of food protein. Therefore, when using the PRACTALL guidelines, early responders can be expected. Ingestion of a cumulative dose of 3,500 mg to reach a false-negative rate of maximum 5% is not feasible in most children using the gingerbread matrix. However, the cumulative dose may be reduced without increasing false-negative results, making challenges with the gingerbread matrix feasible for all age groups.

Reactions to peanut at first introduction in infancy are associated with age ≥8 months and severity of eczema.

BACKGROUND: Previous studies have shown the efficacy of the early introduction of peanut to prevent peanut allergy. Due to the exclusion of infants with sensitization to peanut, it remains unclear what the optimal timing of introduction is. METHODS: The PeanutNL study was performed in 6 pediatric allergology centers in the Netherlands. Infants referred for the clinical early introduction of peanut to prevent peanut allergy underwent skin prick tests for peanut and an oral peanut challenge at a median age of 6 months. RESULTS: One hundred sixty two of 707 infants (23%) who had never eaten peanut before were sensitized to peanut, of which 80 (49%) had wheals of >4 mm. Sixty seven of 707 infants (9.5%) had a positive oral challenge to peanut at first introduction. Multivariate analysis revealed that age (p < .001) and SCORAD eczema severity scores (p = .001) were significant risk factors. Introduction of peanut at ≥8 months in infants with moderate and severe eczema resulted in an increased risk (odds ratio 5.24 (p = .013) and 3.61 (p = .019), respectively) of having reactions to peanut as compared to introduction before 8 months. A family history of peanut allergy and previous reactions to egg were not identified as independent risk factors. CONCLUSION: These results suggest that peanut should be introduced before the age of 8 months to reduce the risk of reactions at first exposure in infants with moderate and severe eczema. Furthermore, since children with severe eczema have the highest risk of reactions, the clinical introduction of peanut should be considered, at the latest at the age of 7 months.

Successful introduction of peanut in sensitized infants with reported reactions at home.

BACKGROUND AND OBJECTIVE: Previous studies have shown efficacy of early introduction of peanut to prevent peanut allergy. It is currently unknown which diagnostic pathway is optimal after parental-reported reactions to peanut at home after early introduction. METHODS: The PeanutNL cohort study included high-risk infants that were referred for early introduction of peanut. A subgroup of 186 infants with reactions to peanut at home underwent peanut skin prick tests and a supervised open oral food challenge (OFC) at a median age of 8 months. After a negative OFC, peanut was introduced at home. RESULTS: Sensitization to peanut was detected in 69% of 186 infants, of which 80% had > 4mm wheals in skin prick tests. An OFC with a cumulative dose of 4.4 gr peanut protein was performed in 163 infants with Sampson severity score grade I-III reactions at home; 120 challenges were negative. Peanut was subsequently introduced at home in infants with a negative challenge outcome. After 6 months, 96% were still eating peanut and 81% ate single portions of 3.0 gr peanut protein. One patient was considered to be peanut allergic after reintroduction of peanut at home. CONCLUSION: These data show that 65% of infants with reported reactions to peanut at home have negative OFCs. In those children, peanut could be introduced safely and 96% were able to consume peanut regularly without reactions. Challenging infants under 12 months of age prevents the misdiagnosis of peanut allergy, and enables safe continued exposure to peanut and the induction of long-term tolerance.

[Prevention of food allergy: Shift from elimination to exposure of highly allergenic food]. / Preventie van voedselallergie.

Since 2015 the new insight has emerged that avoidance of food allergens increases the risk of food allergy, specifically in infants with atopic dermatitis through cutaneous sensitisation. The primary treatment of atopic dermatitis consists of treatment with topical steroids and emollients and not by dietary intervention. Today all children are advised to introduce peanut and egg before 8 months of age. Children with atopic dermatitis are advised to so between 4 and 6 months of age following weaning foods such as fruits and vegetables. Guidelines for early introduction of peanut and egg, including home introduction schedules are available use in primary and secondary care. Timely introduction of diverse and healthy complementary foods also seems to be preventive for the development of food allergy. Breastfeeding yields contradictory results on the prevention of allergic disease, but remains the preferred choice because of many other health benefits.

NK cells recognize and lyse Ewing sarcoma cells through NKG2D and DNAM-1 receptor dependent pathways.

INTRODUCTION: Ewing sarcoma (EWS) is a malignant bone-associated sarcoma, with poor prognosis in case of metastasis or relapse. To explore the feasibility of natural killer (NK) cell mediated immunotherapy and to identify molecular mechanisms involved, the susceptibility of EWS to NK cells was investigated. METHODS AND RESULTS: All EWS cell lines tested (n=7) were lysed by purified allogeneic NK cells from healthy donors, and the efficacy of lysis was increased by activating NK cells with interleukin-15 (IL-15). FACS analysis and immunohistochemistry revealed that EWS cell lines as well as primary tumor cells expressed ligands for the activating NK cell receptors NKG2D and DNAM-1. NK cell cytotoxicity to EWS cells critically depended on the combination of NKG2D and DNAM-1 signaling, since blocking either of these receptors abrogated lysis by resting NK cells. Cytokine-activated NK cells more efficiently recognized EWS cells, since only combined, but not single blockade of NKG2D and DNAM-1 by antibodies inhibited lysis of EWS cells. Induction or blockade of HLA class I on EWS cells did not significantly influence lysis. This suggests that predominantly activating, rather than inhibitory signals on EWS cells determined susceptibility to NK cell cytotoxicity. NK cell cytotoxicity to EWS cells and K562 was reduced in EWS patients at diagnosis (n=11) compared to age matched controls, despite normal NK cell numbers and increased expression of NKG2D. The impaired function of these NK cells was restored after activation with IL-15 in vitro. CONCLUSION: These results demonstrate that EWS cells are potentially susceptible to NK cell cytotoxicity due to the expression of activating NK cell receptor ligands. The use of cytokine-activated NK cells rather than resting NK cells in immunotherapy may be instrumental to optimize NK cell reactivity to EWS.

Reactivation of Human Herpes Virus-6 After Pediatric Stem Cell Transplantation: Risk Factors, Onset, Clinical Symptoms and Association With Severity of Acute Graft-Versus-Host Disease.

BACKGROUND AND METHODS: To study clinical symptoms, timing and consequences of human herpesvirus-6 (HHV-6) reactivation after pediatric allogeneic stem cell transplantation (SCT), HHV-6 was investigated by plasma polymerase chain reaction in a cohort of 106 pediatric SCT recipients. RESULTS: HHV-6 viremia was detected post-SCT in 48% of the patients with a median time of onset at 20 days after SCT. In week 3 and 4 post-SCT, HHV-6 is the most common infectious agent detected. In up to 30% of the patients with fever of unknown origin, HHV-6 was the only detected infectious agent to explain fever. Patients transplanted with an unrelated donor or receiving serotherapy were at increased risk of HHV-6 reactivation. The onset of HHV-6 reactivation coincided with the appearance of lymphocytes and monocytes in peripheral blood. Treatment with alemtuzumab (MabCampath) delayed both lymphocyte and monocyte engraftment and, concomitantly, onset of HHV-6 reactivation was delayed in those cases. HHV-6 reactivation was not associated with an increased incidence of acute graft-versus-host disease (GvHD). However, progression to grade II-IV GvHD was in 9 of 10 patients associated with HHV-6 reactivation before GvHD (P = 0.006) and HHV-6 was the only infection with such an association. CONCLUSIONS: HHV-6 frequently reactivates after pediatric SCT around the time of mononuclear cell engraftment and is associated with an increased severity of GvHD. HHV-6 may explain fever of unknown origin in 30% of the patients early after SCT. Assessment of HHV-6 reactivation in patients early after SCT can be instrumental for clinical decision making.

Adenovirus type 35, but not type 5, stimulates NK cell activation via plasmacytoid dendritic cells and TLR9 signaling.

In hematopoietic stem cell transplant (HSCT) recipients, disseminated adenoviral infections during the first two months after HSCT can lead to severe complications and fatal outcome. Since NK cells are usually the first lymphocytes to reconstitute after HSCT and have been implicated in the clearance of adenovirus-infected cells, it was investigated whether NK cells are activated by adenovirus in vitro. Exposure of PBMC to human adenovirus type 5 (HAdV5) or HAdV35 resulted in the up-regulation of the activation marker CD69 on NK cells and enhanced the cytolytic activity of NK cells. HAdV5-induced NK cell activation relied on the contribution of T cells as the depletion of T cells from PBMC abolished NK cell activation. In contrast, NK cell activation in response to HAdV35 occurred in the absence of T cells. Plasmacytoid dendritic cells (pDC) were necessary and sufficient to mediate NK cell activation. HAdV35 induced significantly more interferon-α (IFN-α) production by pDC than HAdV5. The increased IFN-α production and NK cell activation correlated with a higher infection efficiency of viruses with the type 35 fiber. The IFN-α response of pDC was enhanced by the presence of NK cells, suggesting a reciprocal interaction between pDC and NK cells. Incubation with a TLR9 antagonist impaired the IFN-α production by pDC as well as NK cell activation, implying that TLR9 signaling is critically involved in the IFN-α response of pDC and NK cell activation after HAdV35 exposure. In conclusion, two human adenovirus serotypes from two different species differ considerably in their capacity to stimulate pDC and NK cells.

Evidence for natural killer cell-mediated protection from metastasis formation in uveal melanoma patients.

PURPOSE: In uveal melanoma, low human leukocyte antigen (HLA) class I expression on primary tumors is associated with a decreased risk of metastasis. Consequently, it has been suggested that natural killer (NK) cells, which detect decreased expression of HLA class I, are involved in the immune control of metastases. In this study, three novel lines of evidence were identified that support a role for NK cells. METHODS: Uveal melanoma cell lines were used to determine the expression of NK cell receptor ligands (MICA, MICB, ULBP1-3, CD112, CD155, and HLA class I) and to examine sensitivity to lysis by human NK cell lines. Because interactions between polymorphic killer immunoglobulin receptors (KIRs) and HLA regulate NK cell function, KIR and HLA genotyping was performed on 154 patients with uveal melanoma and 222 healthy control subjects. RESULTS: First, all 11 uveal melanoma cell lines tested expressed ligands for activating as well as inhibitory NK cell receptors. Second, such cell lines were lysed efficiently by human NK cells in vitro. Finally, the HLA-C genotype was related to the risk of metastasis-related death in patients with uveal melanoma: The patients carrying HLA-C alleles encoding ligands for KIR2DL1 and KIR2DL2/3 (HLA-C group 1/group 2 heterozygous patients), both inhibitory NK receptors, had a longer metastasis-free survival than did those carrying HLA-C ligands for either KIR2DL1 (HLA-C group 2 homozygotes) or KIR2DL2/3 (HLA-C group 1 homozygotes). CONCLUSIONS: Together, the data support a role for NK cells in the prevention of uveal melanoma metastases.