Hypersensitivity to mosquito bites: A unique pathogenic mechanism linking Epstein-Barr virus infection, allergy and oncogenesis

A Case of severe mosquito bite allergy complicated by fatal hemophagocytic lymphohistiocytosis

Severe mosquito bite allergy (SMBA) is characterized by necrotic skin lesions and systemic symptoms. Chronic active Epstein-Barr virus (EBV) infection, when superimposed with SMBA, is a key driver for catastrophic clinical consequences, such as uncontrolled lymphoproliferation. This interplay is of clinical significance due to its association with hemophagocytic lymphohistiocytosis (HLH) and/or EBV-driven malignancies. Here, we report a case of SMBA that developed in a 14-year-old Hispanic boy that led to fatal secondary HLH.

Primary cutaneous anaplastic large-cell lymphoma with DUSP22-IRF4 rearrangement following insect bites

Primary cutaneous anaplastic large‐cell lymphoma (pC‐ALCL) is distinguished from systemic anaplastic large‐cell lymphoma (S‐ALCL) with cutaneous involvement. Although pC‐ALCL is a unique entity with different genetics, clinical characteristics, and prognosis, its causes are unknown. Herein, we report the case of a Chinese woman with a 4‐month history of a gradually enlarged ulcerative mass in her right forearm following an unidentified insect bite. Biopsy revealed an extensive infiltrate with patches of large anaplastic lymphoid cells. These cells were immunohistochemically positive for CD45, CD30, and TIA‐1 and negative for CD2, CD3, CD4, CD5, CD20, CD7, CD8, and ALK‐1. DUSP22‐IRF4 rearrangement was detected; on the other hand, TP63 rearrangement was not observed by fluorescence in situ hybridization (FISH). No Epstein‐Barr virus‐encoded small RNAs (EBERs) were detected by ISH. Rearrangement of monoclonal TCR gene was found using BIOMED‐2 polymerase chain reaction. No abnormality was found on the subsequent positron emission tomography‐computed tomography (PET‐CT) scan. After five cycles of cyclophosphamide + doxorubicin + vincristine + prednisolone (CHOP) chemotherapy, the patient achieved complete remission. This is the first report of a unique pC‐ALCL with DUSP22‐IRF4 rearrangement following an insect bite other than S‐ALCL involving the skin.

Hypersensitivity to mosquito bites: A versatile Epstein-Barr virus disease with allergy, inflammation, and malignancy

Hypersensitivity to mosquito bites (HMB) is a rare disease characterized by transient intense skin reaction and systemic inflammation. Clinical presentation of HMB resembles other mosquito allergic responses, and it can also be difficult to clinically distinguish HMB from other severe allergic reactions. However, a distinctive pathophysiology underlies HMB. HMB belongs to a category of Epstein-Barr virus (EBV)-associated natural killer (NK) cell lymphoproliferative disorders (LPD). Hence, HMB may progress to systemic diseases, such as hemophagocytic lymphohistiocytosis, chronic active EBV disease, and EBV-associated malignancies. A triad of elevated serum IgE, NK lymphocytosis, and detection of EBV DNA in peripheral blood is commonly observed, and identification of EBV-infected NK cells usually facilitates the diagnosis. However, the effective treatment is limited, and its precise etiology remains unknown. Local CD4+ T cell proliferation triggered by mosquito bites appears to help induce EBV reactivation and EBV-infected NK-cell proliferation. These immunological interactions may explain the transient HMB signs and symptoms and the disease progression toward malignant LPD. Further research to elucidate the mechanism of HMB is warranted for better diagnosis and treatment of HMB and other forms of EBV-associated LPD.

Epstein-Barr Virus-Associated T- and NK-Cell Lymphoproliferative Diseases: A Review of Clinical and Pathological Features

Simple Summary

In most Epstein–Barr virus (EBV)-infected individuals, the virus establishes a lifelong latent infection with no specific clinical manifestation. However, EBV primary infection and secondary reactivation may cause various EBV-associated lymphoproliferative disorders (LPD), including hematologic malignancies. Among them, EBV-positive T/NK LPD are uncommon diseases defined by the proliferation of T- or NK-cells infected by EBV, more commonly encountered in Asians and Latin Americans. They encompass a spectrum of disorders ranging from indolent reactive lesions to malignant and aggressive diseases. Despite novel insights from high-throughput molecular studies, the pathogenesis of these disorders is not well understood, and EBV-positive T/NK LPD diagnoses remain challenging due to their rarity and considerable overlap. Indeed, this article discusses new insights into EBV-positive T/NK LPD and focuses on diagnosis challenges, describing the difficulties to clarify the borders between overlapping LPD subtypes.

Abstract

Epstein–Barr virus (EBV) is a ubiquitous virus detected in up to 95% of the general population. Most people are asymptomatic, while some may develop a wide range of EBV-associated lymphoproliferative disorders (LPD). Among them, EBV-positive T/NK LPD are uncommon diseases defined by the proliferation of T- or NK-cells infected by EBV. The 2017 World Health Organization (WHO) classification recognizes the following entities characterized by different outcomes: chronic active EBV infection of T- or NK-cell types (cutaneous and systemic forms), systemic EBV-positive T-cell lymphoma of childhood, EBV-positive aggressive NK-cell leukemia, extra nodal NK/T-cell lymphoma nasal type, and the new provisional entity known as primary EBV-positive nodal T/NK-cell lymphoma. In addition, EBV associated-hemophagocytic lymphohistiocytosis is part of EBV-positive T/NK LPD, but has not been included in the WHO classification due to its reactive nature. Despite novel insights from high-throughput molecular studies, EBV-positive NK/T-cell LPD diagnoses remain challenging, especially because of their rarity and overlap. Until now, an accurate EBV-positive NK/T LPD diagnosis has been based on its clinical presentation and course correlated with its histological features. This review aims to summarize clinical, pathological and molecular features of EBV-positive T/NK LPD subtypes and to provide an overview of new understandings regarding these rare disorders.

Insect hypersensitivity beyond bee and wasp venom allergy

The bites of blood-feeding insects regularly induce sensitization to salivary proteins and cause local hypersensitivity reactions in over 90% of the population, representing either an IgE-mediated immediate wheal and flare reaction or a T cell-driven delayed papule. Long-lasting large local reactions and bullous reactions may cause significant discomfort and reduction in quality-of-life. Anaphylaxis is rarely reported though proven for several insects, above all mosquitoes, horse flies, and kissing bugs. Recently, salivary gland proteins have been thoroughly studied in some blood-feeding insect species, and several allergens have been identified. Interestingly, many of them belong to the same protein families as the well-known honeybee and wasp venom allergens (phospholipases, hyaluronidases, antigens 5, serine proteases) though sequence identities are mostly low. There is still insufficient evidence for the proposed cross-reactivity between salivary proteins from blood-feeding insects and Hymenoptera venom allergens.

The aim of the measurement of Epstein-Barr virus DNA in hydroa vacciniforme and hypersensitivity to mosquito bites

Epstein-Barr virus (EBV) DNA load in the blood increases in posttransplant lymphoproliferative disorders and chronic active EBV infection. In this report, we analyzed the EBV DNA load in the peripheral blood mononuclear cells (PBMCs) and plasma of patients with hydroa vacciniforme (HV) and/or hypersensitivity to mosquito bites (HMB) to understand the clinical significance of EBV DNA load. All 30 patients showed high DNA loads in the PBMCs over the cut-off level. Of 16 plasma samples, extremely high in two samples obtained from patients with hemophagocytic lymphohistiocytosis (HLH). The amount of cell-free DNA in plasma was correlated to the serum levels of lactate dehydrogenase and inversely correlated to platelet counts. These results indicate that the EBV DNA load in PBMCs can provide one of the diagnostic indicators for HV and HMB and marked elevation of cell-free EBV DNA in plasma might be related to cytolysis such as that observed in HLH.

Epstein - Barr virus positive T and NK-cell lymphoproliferations: Morphological features and differential diagnosis

The spectrum of Epstein-Barr virus (EBV)-positive T and NK-cell lymphoproliferations is broad and ranges from reactive self-limited disorders to neoplastic processes with a fulminant clinical course. EBV plays an important role promoting lymphomagenesis, although the precise mechanisms remain elusive. EBV-positive lymphoproliferative disorders (LPD) are more common in East Asia (China, Japan, Korea and Taiwan), and Latin America suggesting a strong genetic predisposition. The revised 2016 World Health Organization (WHO) lymphoma classification recognizes the following malignant NK- and T-cell lymphomas; extranodal NK/T-cell lymphoma, nasal type (ENKTCL), aggressive NK-cell leukemia (ANKL), and the provisional entity within the group of peripheral T-cell lymphoma, not otherwise specified (PTCL, NOS) "primary EBV-positive nodal T or NK cell lymphoma". Disorders presenting mainly in children and young adults include chronic active EBV infection (CAEBV) - systemic and cutaneous forms - which are not considered malignant disorders but were included in the WHO classification for the first time because of the differential diagnosis with other T- or NK-cell lymphomas. CAEBV, cutaneous form, includes hydroa vacciniforme-like LPD (HV-LPD) and severe mosquito bite allergy (SMBA). Finally, systemic EBV-positive T-cell lymphoma of childhood was recognized as lymphoma because of its fulminant clinical course. Given the shared pathogenesis of these disorders, overlapping features are common demanding a close clinical, morphological and molecular correlation for an accurate diagnosis. This review summarizes the clinical, histopathological and molecular features of EBV-associated T and NK-cell LPD, highlighting the main features that might aid in the differential diagnosis.

Mosquitoes, Infectious Diseases, and Cancer: A Connection to Study?

Mosquitoes (Diptera: Culicidae) are vectors of pathogens and parasites of great medical and veterinary relevance. The possible association between mosquitoes, infectious diseases, and cancer has been investigated. Despite its potential importance, there is a severe lack of research data on the topic. Herein, current knowledge, tenuous links, and related challenges on the topic were examined, grouping information under four major hypotheses. The first hypothesis is that the infection of mosquito-vectored parasites, with special reference to Plasmodium spp., may lead to cancer. The International Agency for Research on Cancer stated that being infected by Plasmodium falciparum malaria in holoendemic areas is probably carcinogenic to humans (group 2A), considering that P. falciparum infection is able to reactivate the Epstein–Barr virus, leading to endemic Burkitt lymphoma. Also, malaria was recently associated with a cancer incidence increase in the United States. The second hypothesis is that cancer may be spread directly through mosquito bites: Aedes mosquitoes transfer viable tumor cells among vertebrate hosts, even if no plausible mechanisms for these cells to develop cancer into the new host are known. As the third hypothesis, mosquito bites may lead to hypersensitivity, resulting in cancer. Hypersensitivity stimulated by mosquito bites links allergy, oncogenesis, and the Epstein–Barr virus, causing Burkitt lymphoma. One may argue that pathogens transmitted by mosquitoes, such as viruses, may be carcinogenic. However, no detailed research evidences are available to substantiate this last hypothesis. However, despite the intriguing hypotheses outlined above, there is a severe lack of data showing cancer development in organisms exposed to mosquitoes transmitting parasites or pathogens. According to One Health criteria, this benchmark is aimed to outline major questions on this public health issue, stressing the need of multidisciplinary research and discussion.

Epstein-Barr virus-associated T- and NK-cell lymphoproliferative diseases: an update and diagnostic approach

Epstein-Barr virus (EBV)-positive T-cell and natural killer (NK)-cell lymphoproliferative diseases (EBV-TNKLPD) are a group of uncommon disorders characterised by EBV infection of T- and NK-cells. As a group, EBV-TNKLPD are more commonly encountered in Asians and Native Americans from Central and South America compared to Western populations. They encompass a spectrum of entities that range from non-neoplastic lesions such as EBV-associated haemophagocytic lymphohistiocytosis (EBV-HLH) to more chronic conditions with variable outcomes such as chronic active EBV infections (CAEBV) of T- and NK-cell type (cutaneous and systemic forms) and malignant diseases such as systemic EBV-positive T-cell lymphoma of childhood, aggressive NK-cell leukaemia, extranodal NK/T-cell lymphoma, nasal-type, and primary EBV-positive nodal T/NK-cell lymphoma. Due to their rarity, broad clinicopathological spectrum and significant morphological and immunophenotypic overlap, the diagnosis and precise classification of EBV-TNKLPD often pose a challenge to clinicians and pathologists. Correct classification of this group of rare diseases relies heavily on the age of onset, disease presentation, duration of symptoms and cell of origin (T- vs NK-cell lineage). In this review, we provide an update on the clinicopathological and molecular features of the various EBV-TNKLPD entities occurring in non-immunocompromised patients and present a practical algorithmic approach for the general pathologist who is confronted with these disorders in routine clinical practice.

Acute kidney injury in an adult patient with IgA nephropathy and chronic replicative Epstein-Barr virus infection

Most of the adult population are infected with Epstein-Barr virus (EBV), but as EBV replication is usually under immune system control, the majority of individuals remain asymptomatic. On the other hand, some individuals continuously retain a high EBV antibody titer and a high EBV DNA load in their blood, suggesting a defect of EBV replication control. To date, only a limited number of reports have addressed the relationship between this chronic form of EBV infection and renal involvement. Here, we describe an 80-year-old woman who developed acute kidney injury shortly after an episode of mosquito bites, accompanied by a severe skin rash, which raised a suspicion of chronic EBV infection. She was subsequently diagnosed as having chronic replicative EBV infection. Renal biopsy revealed a diagnosis of IgA nephropathy with crescent formation. Although the relationship between IgA nephropathy and EBV infection has been discussed, no substantial understanding has yet emerged. The patient's characteristic clinical course suggested that the renal failure may have been partly attributable to chronic EBV infection. This case suggests that physicians may need to consider the possibility that chronic EBV infection may affect the clinical course of IgA nephropathy, or exacerbate the disease.

Mantle cell lymphoma presenting with exaggerated skin reaction to insect bites

We present the case of a 62-year-old African-American woman with medical history of hypertension and hyperlipidaemia who presented to dermatology clinic for 'bug bites'. Skin examination showed resolving bullae on the shins and postinflammatory pigment changes. Histopathology showed eosinophilic spongiosis and direct immunofluorescence (DIF) was negative for IgG, IgM, IgA and C3. After returning to clinic with recurrent severe bullous eruptions, the patient presented with anaemia, lymphocytosis, posterior cervical lymphadenopathy and weight loss. An exuberant bite reaction in the setting of lymphoma was suspected. Further workup with haematology revealed elevated IgG level and total protein levels. Flow cytometry showed a B cell lymphoma subtype. Extensive imaging was positive for diffuse lymphadenopathy, with accompanying evidence of Ebstein-Barr virus infection. Our case highlights the importance of considering exuberant arthropod bite reaction in the setting of undiagnosed lymphoma in a patient with bullous eruption and negative DIF.

EBV-Positive Lymphoproliferations of B- T- and NK-Cell Derivation in Non-Immunocompromised Hosts

The contribution of Epstein-Barr virus (EBV) to the development of specific types of benign lymphoproliferations and malignant lymphomas has been extensively studied since the discovery of the virus over the last 50 years. The importance and better understanding of the EBV-associated lymphoproliferative disorders (LPD) of B, T or natural killer (NK) cell type has resulted in the recognition of new entities like EBV+ mucocutaneous ulcer or the addition of chronic active EBV (CAEBV) infection in the revised 2016 World Health Organization (WHO) lymphoma classification. In this article, we review the definitions, morphology, pathogenesis, and evolving concepts of the various EBV-associated disorders including EBV+ diffuse large B-cell lymphoma, not otherwise specified (DLBCL, NOS), EBV+ mucocutaneous ulcer, DLBCL associated with chronic inflammation, fibrin-associated DLBCL, lymphomatoid granulomatosis, the EBV+ T and NK-cell LPD of childhood, aggressive NK leukaemia, extranodal NK/T-cell lymphoma, nasal type, and the new provisional entity of primary EBV+ nodal T- or NK-cell lymphoma. The current knowledge regarding the pathogenesis of B-cell lymphomas that can be EBV-associated including Burkitt lymphoma, plasmablastic lymphoma and classic Hodgkin lymphoma will be also explored.

Characterization of skin blister fluids from children with Epstein-Barr virus-associated lymphoproliferative disease

Epstein-Barr virus (EBV)-associated T- or natural killer (NK)-cell lymphoproliferative disease (LPD) is a heterogeneous group of disorders characterized by chronic proliferation of EBV-infected lymphocytes. Patients may present with severe skin manifestations, including hypersensitivity to mosquito bites (HMB) and hydroa vacciniforme (HV)-like eruption, which are characterized by blister formation and necrotic ulceration. Skin biopsy specimens show inflammatory reactions comprising EBV-infected lymphocytes. However, blister fluids have not been fully assessed in patients with this disease. Blister fluids were collected from three patients with EBV-associated LPD: two with HMB and one with HV. Immunophenotyping of blister lymphocytes and measurement of tumor necrosis factor (TNF)-α in blister fluids were performed. The patients with HMB and HV exhibited markedly increased percentages of NK and γδ T cells, respectively, in both peripheral blood and blister fluids. These NK and γδ T cells strongly expressed the activation marker human leukocyte antigen-DR and were considered to be cellular targets of EBV infections. TNF-α was highly elevated in all blister fluids. Severe local skin reactions of EBV-associated LPD may be associated with infiltrating EBV-infected lymphocytes and a high TNF-α concentration in blister fluids.

Cytologic Analysis of Epstein-Barr Virus-Associated T/Natural Killer-Cell Lymphoproliferative Diseases

Rapid, precise diagnosis of Epstein-Barr virus-associated T lymphocyte or natural killer cell lymphoproliferative diseases is clinically important to prevent disease progression and avoid fatal outcomes for patients. In addition to detecting increased copy numbers of Epstein-Barr virus, identification of the lymphocyte subpopulation targeted by the virus infection is crucial to reaching the final diagnosis. However, these procedures are laborious and require large amounts of sample. In contrast, flowcytometric analysis may provide crucial information for initial screening of diseases using only small amounts of sample and involves little labor. In addition to the increase of a particular subpopulation, selective HLA-DR expression indicates selective activation and expansion of a virus-infected clone. Presence of a characteristic HLA-DR^high CD5^dim/negative fraction within CD8⁺ T lymphocytes indicates a possible diagnosis of Epstein-Barr virus-associateds hemophagocytic lymphohistiocytosis. One should note, however, that cases with familial hemophagocytic lymphohistiocytosis may exhibit a similar abnormal fraction within CD8⁺ T lymphocytes. These T cells are oligoclonally expanded reactive T cells expanding in response to B cells infected with Epstein-Barr virus.

Gene expression analysis of hypersensitivity to mosquito bite, chronic active EBV infection and NK/T-lymphoma/leukemia

The human herpes virus, Epstein-Barr virus (EBV), is a known oncogenic virus and plays important roles in life-threatening T/NK-cell lymphoproliferative disorders (T/NK-cell LPD) such as hypersensitivity to mosquito bite (HMB), chronic active EBV infection (CAEBV), and NK/T-cell lymphoma/leukemia. During the clinical courses of HMB and CAEBV, patients frequently develop malignant lymphomas and the diseases passively progress sequentially. In the present study, gene expression of CD16^(-)CD56⁽⁺⁾-, EBV⁽⁺⁾ HMB, CAEBV, NK-lymphoma, and NK-leukemia cell lines, which were established from patients, was analyzed using oligonucleotide microarrays and compared to that of CD56^brightCD16^dim/- NK cells from healthy donors. Principal components analysis showed that CAEBV and NK-lymphoma cells were relatively closely located, indicating that they had similar expression profiles. Unsupervised hierarchal clustering analyses of microarray data and gene ontology analysis revealed specific gene clusters and identified several candidate genes responsible for disease that can be used to discriminate each category of NK-LPD and NK-cell lymphoma/leukemia.

Green synthesized nanoparticles in the fight against mosquito-borne diseases and cancer-a brief review

Nanobiomedicine and parasitology are facing a number of key challenges, which mostly deal with the paucity of effective preventive and curative tools against mosquito-borne diseases and cancer. In this scenario, the employ of botanical and invertebrate extracts as reducing, stabilizing and capping agents for the synthesis of nanoparticles is advantageous over chemical and physical methods, since it is one-pot, cheap, and does not require high pressure, energy, temperature, or the use of highly toxic chemicals. Considering the overlooked connection between mosquito vector activity and the spread of cancer in USA, this review focused on the current knowledge available about green synthesized nanoparticles with efficacy against mosquito-borne diseases and cancer. Green fabricated metal nanoparticles showed antiplasmodial activity that often encompasses the efficacy of currently marked drugs for malaria treatment. They have been also reported as growth inhibitors against dengue virus (serotype DEN-2), with moderate cytotoxicity on mammalian cells. However, this feature is strongly dependent to the botanical agents employed during nanosynthesis. In addition, green nanoparticles have been successfully used to reduce mosquito young instar populations in the field. The final section focuses on some issues for future research, with special reference to the chemical standardization of the botanical extracts used for nanosynthesis and the potential effects on green fabricated nanoparticles on non-target organisms.

Atypical manifestations of Epstein-Barr virus in children: a diagnostic challenge

OBJECTIVE

Clarify the frequency and the pathophysiological mechanisms of the rare manifestations of Epstein-Barr virus infection.

SOURCES

Original research studies published in English between 1985 and 2015 were selected through a computer-assisted literature search (PubMed and Scopus). Computer searches used combinations of key words relating to "EBV infections" and "atypical manifestation."

SUMMARY OF THE FINDINGS

Epstein-Barr virus is a herpes virus responsible for a lifelong latent infection in almost every adult. The primary infection concerns mostly children and presents with the clinical syndrome of infectious mononucleosis. However, Epstein-Barr virus infection may exhibit numerous rare, atypical and threatening manifestations. It may cause secondary infections and various complications of the respiratory, cardiovascular, genitourinary, gastrointestinal, and nervous systems. Epstein-Barr virus also plays a significant role in pathogenesis of autoimmune diseases, allergies, and neoplasms, with Burkitt lymphoma as the main representative of the latter. The mechanisms of these manifestations are still unresolved. Therefore, the main suggestions are direct viral invasion and chronic immune response due to the reactivation of the latent state of the virus, or even various DNA mutations.

CONCLUSIONS

Physicians should be cautious about uncommon presentations of the viral infection and consider EBV as a causative agent when they encounter similar clinical pictures.

Epstein-Barr virus: dermatologic associations and implications: part I. Mucocutaneous manifestations of Epstein-Barr virus and nonmalignant disorders

Epstein-Barr virus (EBV) is a ubiquitous virus that has been implicated in a wide range of human diseases, many of which have mucocutaneous manifestations. As a member of the herpesviridae family, EBV causes lifelong infection by establishing latency in B lymphocytes. An intact immune response is critical in preventing progression of EBV disease, and the clinical manifestations of infection are dependent on the intricate relationship between virus and host immune system. This review provides a comprehensive overview of the epidemiology, pathophysiology, and diagnostic testing in EBV infection. In part I of this continuing medical education article, the mucocutaneous manifestations of EBV infection are reviewed with an emphasis on pathophysiology and management.

Hypersensitivity to mosquito bites as the primary clinical manifestation of an Epstein-Barr virus infection

Hypersensitivity to mosquito bites (HMB) is a rare disease characterized by intense local skin reactions with general symptoms, such as high fever and regional lymphadenopathy after mosquito bites. Epstein-Barr virus (EBV) chronic infection and NK cell lymphoproliferative disease have been reported first in diagnosed HMB patients. Here, we present the case of a 6-year-old girl with 2 months' history of bullae and necrotic skin lesions, accompanied by a high temperature, visual hallucinations, and liver dysfunction after mosquito bites. A histopathologic examination of the skin lesion showed vasculitis and EBV infection. We could not detect any findings of hematologic malignancies or NK cell proliferative disease in the patient. Clinicians should closely evaluate HMB patients for possible development of lymphoproliferative status or hematologic malignant disorders.

Immunologic difference between hypersensitivity to mosquito bite and hemophagocytic lymphohistiocytosis associated with Epstein-Barr virus infection

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening, virus-triggered immune disease. Hypersensitivity to mosquito bite (HMB), a presentation of Chronic Active Epstein-Barr Virus infection (CAEBV), may progress to HLH. This study aimed to investigate the immunologic difference between the HMB episodes and the HLH episodes associated with EBV infection. Immunologic changes of immunoglobulins, lymphocyte subsets, cytotoxicity, intracellular perforin and granzyme expressions, EBV virus load and known candidate genes for hereditary HLH were evaluated and compared. In 12 HLH episodes (12 patients) and 14 HMB episodes (4 patients), there were both decreased percentages of CD4+ and CD8+ and increased memory CD4+ and activated (CD2+HLADR+) lymphocytes. In contrast to HMB episodes that had higher IgE levels and EBV virus load predominantly in NK cells, those HLH episodes with virus load predominantly in CD3+ lymphocyte had decreased perforin expression and cytotoxicity that were recovered in the convalescence period. However, there was neither significant difference of total virus load in these episodes nor candidate genetic mutations responsible for hereditary HLH. In conclusion, decreased perforin expression in the HLH episodes with predominant-CD3+ EBV virus load is distinct from those HMB episodes with predominant-NK EBV virus load. Whether the presence of non-elevated memory CD4+ cells or activated lymphocytes (CD2+HLADR+) increases the mortality rate in the HLH episodes remains to be further warranted through larger-scale studies.

How I treat NK/T-cell lymphomas

Natural killer (NK)/T-cell lymphomas and NK-cell leukemias are aggressive malignancies. Occurring worldwide, they show a predilection for Asian and South American populations. Neoplastic cells are surface CD3-, cytoplasmic CD3ε+, CD56+, cytotoxic-molecule positive, Epstein-Barr virus (EBV) positive, with germline T-cell receptor gene. Lymphomas occur commonly in the nasal and upper aerodigestive region. Occasional cases present in the skin, salivary gland, testis, and gastrointestinal tract. Rare cases are disseminated with lymphadenopathy, hepatosplenomegaly, and a leukemic phase. Positron emission tomography computed tomography is useful in staging, as lymphomas are 18-fluorodeoxyglucose avid. Quantification of circulating EBV DNA is an accurate biomarker of tumor load. Nasal NK/T-cell lymphomas present mostly with stage I/II disease. Concomitant/sequential chemotherapy and radiotherapy is standard treatment. Radiotherapy alone is inadequate because of high systemic failure rate. For stage III/IV nasal, nonnasal, and disseminated lymphomas, systemic chemotherapy is indicated. Regimens containing l-asparaginase and drugs unaffected by P-glycoprotein are most effective. Hematopoietic stem cell transplantation (HSCT) is not indicated for early-stage nasal lymphomas. HSCT for lymphomas not in remission has poor results. In advanced-stage nasal, nonnasal, disseminated, or relapsed lymphomas, HSCT may be considered when remission is achieved. Prognostic modeling and EBV DNA monitoring may be useful in risk stratification for HSCT.

A case of hypersensitivity to mosquito bites without peripheral natural killer cell lymphocytosis in a 6-year-old Korean boy

Hypersensitivity to mosquito bites (HMB) is a rare disease characterized by intense skin reactions such as bulla and necrotic ulcerations at bite sites, accompanied by general symptoms such as high-grade fever and malaise occurred after mosquito bites. It has been suggested that HMB is associated with chronic Epstein-Barr virus (EBV) infection and natural killer (NK) cell leukemia/lymphoma. We describe here a Korean child who presented with 3-yr history of HMB without natural killer cell lymphocytosis. He has been ill for 6 yr with HMB. Close observation and examination for the development of lymphoproliferative status or hematologic malignant disorders is needed.

Insect stings: clinical features and management

BACKGROUND

In human beings, local and systemic reactions can be caused both by blood-sucking insects and by venomous insect stings. In Central Europe, the insects that most commonly cause such reactions are honeybees, certain social wasps, mosquitoes, and flies.

METHODS

This article is based on a selective literature review, including guidelines from Germany and abroad.

RESULTS

Insect venom induces a toxic reaction at the site of the sting. Large local reactions are due to allergy and occur in up to 25% of the population; as many as 3.5% develop IgE-mediated, potentially life-threatening anaphylaxis, of which about 20 people die in Germany each year. Mastocytosis is found in 3% to 5% of patients with sting anaphylaxis, rendering these patients prone to very severe reactions. Blood-sucking by hematophagous insects can elicit a local allergic reaction, presenting as a wheal or papule, in at least 75% of the population. Large local reactions may ensue, but other diseases are rare. The acute symptoms of an insect sting are treated symptomatically. Patients who have had a systemic reaction or a large local reaction due to insect allergy must take permanent measures to avoid further allergen contact, and to make sure they can treat themselves adequately if stung again. Most patients with systemic anaphylactic reactions to bee or wasp stings need specific immunotherapy.

CONCLUSION

Insect stings can cause severe disease. Anaphylaxis due to bee or wasp stings is not a rare event; specific immunotherapy protects susceptible persons from further, potentially life-threatening reactions.

Cutaneous presentation of ALK-positive anaplastic large cell lymphoma following insect bites: evidence for an association in five cases

BACKGROUND

Skin involvement is frequent in ALK-positive anaplastic large cell lymphomas. The role of an insect bite as a triggering event has been postulated but not well documented.

DESIGN AND METHODS

We retrospectively investigated five cases of ALK-positive anaplastic large cell lymphoma who presented with skin lesions occurring after an insect bite. Biopsies were immunostained with antibodies against CD30, ALK, T- and B-cell antigens.

RESULTS

Persistent skin lesions developed after solitary insect bites in three patients and after multiple bites in two. Regional lymphadenopathy developed within weeks after the bite in three cases. In four cases the correct diagnosis was delayed due to misinterpretation of the findings as a reactive infiltrate in the skin (n=2) or lymph nodes (n=2); all cases subsequently showed small numbers of cells with nuclear and cytoplasmic staining for ALK. The final diagnoses were lymphohistiocytic variant (n=3) and composite common/small cell type (n=2) anaplastic large cell lymphoma. The patients were treated and three were alive at the last follow-up. Two patients died, one of pneumonia and the other of disseminated disease.

CONCLUSIONS

In these cases the sequence of events between the insect bites and the occurrence of both skin lesions and satellite lymphadenopathy suggest a direct relationship between the bite and the presentation with anaplastic large cell lymphoma. We postulate that insect bite-associated antigens could result in an influx of T lymphocytes, some bearing the t(2;5). The subsequent release of cytokines at the site of the bite could act as a 'second hit', eliciting activation of the latter cells, which would then express the oncogenic NPM-ALK protein and undergo uncontrolled proliferation.

NK/T-cell lymphoma in a child with hypersensitivity to mosquito bites

Hypersensitivity to mosquito bite (HMB) is defined as intense skin reactive lesion after mosquito bite. However, some kind of malignant tumor is closely associated with HMB, especially natural killer (NK)/T-cell lymphoma. We described a nasal-type NK/T-cell lymphoma in a 9-year-old girl after a history of 2 years earlier of HMB. Pathologic evaluation revealed the typical histologic features of NK/T-cell lymphoma, and the dermal and subcutaneous inflammatory reaction of HMB lesions. HMB is rarely reported and should be kept in mind as a clinical sign of subsequent NK/T-cell lymphoma in Asian country where HMB is relatively frequently encountered.

Distribution of 'promoter' sandflies associated with incidence of classic Kaposi's sarcoma

The patchy geographical distributions of classic Kaposi's sarcoma (KS) and human herpesvirus type 8 (HHV-8), better known as Kaposi's sarcoma-associated herpesvirus (KSHV) remain unexplained. It has been proposed that certain species of bloodsucking insects ('promoter arthropods') promote the reactivation of HHV-8/KSHV and facilitate both HHV-8/KSHV transmission and KS development. This hypothesis was tested by sampling the presence and density of human-biting Diptera with CDC light traps in two areas of Sardinia with contrasting incidence rates of classic KS. In total, 11,030 specimens (99.9% sandflies and 0.1% mosquitoes) belonging to 10 species were collected from 40 rural sites. Five of these species are considered to be possible promoter arthropods because of the irritation their bites cause: Phlebotomus perniciosus Newstead; Phlebotomus perfiliewi Parrot (Diptera: Psychodidae); Aedes berlandi Seguy; Culiseta annulata (Schrank) and Culex theileri Theobald (Diptera: Culicidae). Five species are probable 'non-promoters' because their bites are not particularly irritating: Culiseta longiareolata (Macquart); Culex pipiens s.l.; Anopheles algeriensis Theobald; Anopheles maculipennis s.l., and Anopheles plumbeus Stephens. A significant correlation was found between the geographical distribution of promoter arthropods and incidence rates of KS (Spearman's r = 0.59,P < 0.01). Promoter arthropods were more likely to be caught in areas with cutaneous leishmaniasis and a past high prevalence of malaria, and in areas of limestone, acid volcanic soil and cereal cultivation. The study supports the association between promoter arthropods and classic KS, which may explain the geographic variability of KS and HHV-8/KSHV, and highlights the links with a number of variables previously associated with the incidence of KS.

Mucocutaneous manifestations of Epstein-Barr virus infection

This review focuses on Epstein-Barr virus (EBV) infection, diagnosis, and current treatment, with emphasis on EBV-associated mucocutaneous manifestations in primary infections, acute EBV-associated syndromes, chronic infections, lymphoproliferative disorders, and lymphomas. In primary infection, EBV infects B cells and can cause mucocutaneous manifestations in infectious mononucleosis or acute EBV-associated syndromes such as Gianotti-Crosti syndrome and hemophagocytic syndrome. EBV then persists in the majority of humans generally without causing disease. In some cases, however, latent EBV infection may result in diseases such as hydroa vacciniforme, hypersensitivity to mosquito bites, and lymphoproliferative disorders such as plasmablastic lymphoma, oral hairy leukoplakia, and post-transplant lymphoproliferative disorders, particularly in immunocompromised patients. Latent EBV infection has also been implicated in a variety of malignant conditions such as Burkitt lymphoma, Hodgkin lymphoma, nasopharyngeal carcinoma, and Kikuchi histocytic necrotizing lymphadenitis. Since the immune system is critical in preventing the progression of EBV disease, the immunologic status of the patient plays a crucial role in the subsequent development of pathologies.

Coadaptation and malaria control

Malaria emerges from a disequilibrium of the system 'human-plasmodium-mosquito' (HPM). If the equilibrium is maintained, malaria does not ensue and the result is asymptomatic plasmodium infection. The relationships among the components of the system involve coadaptive linkages that lead to equilibrium. A vast body of evidence supports this assumption, including the strategies involved in the relationships between plasmodium and human and mosquito immune systems, and the emergence of resistance of plasmodia to antimalarial drugs and of mosquitoes to insecticides. Coadaptive strategies for malaria control are based on the following principles: (1) the system HPM is composed of three highly complex and dynamic components, whose interplay involves coadaptive linkages that tend to maintain the equilibrium of the system; (2) human and mosquito immune systems play a central role in the coadaptive interplay with plasmodium, and hence, in the maintenance of the system's equilibrium; the under- or overfunction of human immune system may result in malaria and influence its severity; (3) coadaptation depends on genetic and epigenetic phenomena occurring at the interfaces of the components of the system, and may involve exchange of infectrons (genes or gene fragments) between the partners; (4) plasmodia and mosquitoes have been submitted to selective pressures, leading to adaptation, for an extremely long while and are, therefore, endowed with the capacity to circumvent both natural (immunity) and artificial (drugs, insecticides, vaccines) measures aiming at destroying them; (5) since malaria represents disequilibrium of the system HPM, its control should aim at maintaining or restoring this equilibrium; (6) the disequilibrium of integrated systems involves the disequilibrium of their components, therefore the maintenance or restoration of the system's equilibrium depend on the adoption of integrated and coordinated measures acting on all components, that means, panadaptive strategies. Coadaptive strategies for malaria control should consider that: (1) host immune response has to be induced, since without it, no coadaptation is attained; (2) the immune response has to be sustained and efficient enough to avoid plasmodium overgrowth; (3) the immune response should not destroy all parasites; (4) the immune response has to be well controlled in order to not harm the host. These conditions are mostly influenced by antimalarial drugs, and should also be taken into account for the development of coadaptive malaria vaccines.

Advances in mosquito allergy

PURPOSE OF REVIEW

Allergic reactions, including severe local and systemic reactions to mosquito bites, are immunological in nature, and involve immunoglobulin E, immunoglobulin G, and T-lymphocyte-mediated hypersensitivities in response to allergens in mosquito saliva. Naturally acquired desensitization to mosquito saliva may occur during childhood or during long-term exposure to mosquitoes. Due to the lack of availability of mosquito salivary preparations for use in skin tests and in-vitro tests, allergic reactions to mosquito bites are under diagnosed and under treated.

RECENT FINDINGS

Recombinant saliva allergens with biological activity are being developed. Recombinant Aedes aegypti salivary allergen rAed a 2 has been expressed, purified, characterized and used in in-vitro diagnosis of mosquito allergy. Mosquito saliva-induced non-immunoglobulin E-mediated skin mast cell degranulation was found to induce macrophage-inflammatory protein 2 in the skin and interleukin-10 in draining lymph nodes.

SUMMARY

In this review, we discuss the allergic reactions to mosquito salivary allergens, the immune mechanisms involved, natural desensitization and immunotherapy with mosquito extracts, characteristics of salivary allergens and their recombinant forms, and prevention and treatment of allergic reactions to mosquito bites. Eventually, recombinant salivary allergens will significantly improve the diagnosis of mosquito allergy, and will also improve specific immunotherapy for patients with systemic reactions to mosquito bites.