Season of infectious mononucleosis and risk of multiple sclerosis at different latitudes; the EnvIMS Study

Vitamin D and viral infections: Infectious diseases, autoimmune diseases, and cancers

Viruses can cause many human diseases. Three types of human diseases caused by viruses are discussed in this chapter: infectious diseases, autoimmune diseases, and cancers. The infectious diseases included in this chapter include three respiratory tract diseases: influenza, COVID-19, and respiratory syncytial virus. In addition, the mosquito-borne dengue virus diseases are discussed. Vitamin D can reduce risk, severity, and mortality of the respiratory tract diseases and possibly for dengue virus. Many autoimmune diseases are initiated by the body's reaction to a viral infection. The protective role of vitamin D in Epstein-Barr virus-related diseases such as multiple sclerosis is discussed. There are a few cancers linked to viral infections. Such cancers include cervical cancer, head and neck cancers, Hodgkin's and non-Hodgkin's lymphoma, and liver cancer. Vitamin D plays an important role in reducing risk of cancer incidence and mortality, although not as strongly for viral-linked cancers as for other types of cancer.

Risk factors for multiple sclerosis in the context of Epstein-Barr virus infection

Compelling evidence indicates that Epstein Barr virus (EBV) infection is a prerequisite for multiple sclerosis (MS). The disease may arise from a complex interplay between latent EBV infection, genetic predisposition, and various environmental and lifestyle factors that negatively affect immune control of the infection. Evidence of gene-environment interactions and epigenetic modifications triggered by environmental factors in genetically susceptible individuals supports this view. This review gives a short introduction to EBV and host immunity and discusses evidence indicating EBV as a prerequisite for MS. The role of genetic and environmental risk factors, and their interactions, in MS pathogenesis is reviewed and put in the context of EBV infection. Finally, possible preventive measures are discussed based on the findings presented.

Seasonal Patterns of Vogt-Koyanagi-Harada Disease

PURPOSE

To identify the relationship between the incidence of Vogt-Koyanagi-Harada (VKH) disease and seasonality.

METHODS

A retrospective cohort study was performed, including patients with a confirmed diagnosis of VKH whose month of disease onset was available. Information on patients was entered retrospectively into a database and analyzed according to the month and season.

RESULTS

Twenty-four patients who met the inclusion criteria were included in the analysis. There was a statistically significant deviation from expected values in the incidences of VKH per season (P = .043). The most common season for the onset of VKH was fall, with 50% of the patients presenting in this season, while spring was the least common season for VKH presentation, with 12.5% of the patients presenting in this season.

CONCLUSION

Our study suggests that the onset of VKH in Puerto Rico follows a seasonal pattern, with most cases occurring during the fall.

Antibiotic Use and Risk of Multiple Sclerosis: A Nested Case-Control Study in Emilia-Romagna Region, Italy

INTRODUCTION

Known risk factors for multiple sclerosis (MS) include smoking, a low vitamin D status, obesity, and EBV, while the inflammatory feature of the disease strongly suggests the presence of additional infectious agents. The association between use of antibiotics and MS risk that could shed light on these factors is still undetermined. We aimed to evaluate the association between antibiotics and MS risk, in the Emilia-Romagna region (RER), Italy.

METHODS

All adult patients with MS seen at any RER MS center (2015-2017) were eligible. For each of the 877 patients included, clinical information was collected and matched to 5 controls (RER residents) (n = 4,205) based on age, sex, place of residence, and index year. Information on antibiotic prescription was obtained through the linkage with the RER drug prescription database.

RESULTS

Exposure to any antibiotic 3 years prior to the index year was associated with an increased MS risk (OR = 1.52; 95% CI = 1.29-1.79). Similar results were found for different classes. No dose-response effect was found.

DISCUSSION/CONCLUSIONS

Our results suggest an association between the use of antibiotics and MS risk in RER population. However, further epidemiological studies should be done with information on early life and lifestyle factors.

Breastfeeding is associated with reduced risk of multiple sclerosis in males, predominantly among HLA-DRB1*15:01 carriers

BACKGROUND

Breastfeeding as an infant appears protective against later development of some autoimmune diseases, but research into its influence on multiple sclerosis (MS) risk has yielded inconclusive results.

OBJECTIVE

We investigated the possible impact of breastfeeding on MS risk.

METHODS

We used two population-based case-control studies comprising 3670 cases and 6737 matched controls. Logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (CI) for association between MS and exposure to prolonged breastfeeding (4 months or longer) versus reduced breastfeeding (less than 4 months). A meta-analysis of case-control studies that assessed the impact of breastfeeding on MS risk among women and men was conducted.

RESULTS

Prolonged breastfeeding was associated with reduced MS risk among men (OR 0.7, 95% CI 0.5-0.9) but not among women (OR 0.9, 95% CI 0.8-1.1). Among men, a synergistic effect was observed between HLA-DRB1*15:01 carrier status and reduced breastfeeding.

CONCLUSIONS

Findings from the current study add to accumulating evidence that breastfeeding may be a modifiable protective factor for reducing the risk of MS in offspring. When possible, mothers should be supported to breastfeed their infants; however, the mechanism of a sex-specific biologic effect of breastfeeding on MS risk is unclear.

Dietary Supplements on Controlling Multiple Sclerosis Symptoms and Relapses: Current Clinical Evidence and Future Perspectives

Background: Multiple sclerosis (MS) constitutes a chronic progressive demyelinating disease which negatively affects the central nervous system. MS symptoms detrimentally affect the quality of life, as well as the life expectancy of MS patients. In this aspect, the present study aims to critically summarize and evaluate the currently available clinical studies focusing on the potential beneficial effects of dietary supplements on controlling MS symptomatology and relapse. Methods: PubMed database was comprehensively searched, using relative keywords to identify clinical trials that investigated the beneficial effects of dietary supplementation against MS symptomatology and progression. 40 clinical trials were found, which were divided into categories. Results: Nutritional status of MS patients, as well as supplementation have been suggested as potential factors affecting progression. Several substantial studies have documented a systematically high prevalence of vitamin A, B12 and D3 deficiency amongst MS patients. At present, clinical data have suggested that most of the dietary supplements under study may exert antioxidant and anti-inflammatory properties, improving depression symptomatology and quality of life overall. However, malnutrition risk in MS patients has not been adequately explored in order for more precise conclusions to be drawn. The supplements that may have a positive effect on MS are vitamins, fatty acids, antioxidants, phytochemicals and melatonin. Conclusions: Several dietary supplements may decrease inflammation and fatigue, also increasing also autoimmunity tolerance in MS patients, and thus improving quality of life and life expectancy. Currently, there is no effective clinical indication for applying dietary supplementation as complementary treatment against MS symptomatology.

Season of infectious mononucleosis as a risk factor for multiple sclerosis: A UK primary care case-control study

BACKGROUND

Infectious mononucleosis (IM) and vitamin D deficiency are both risk factors for multiple sclerosis (MS).

OBJECTIVE

We wished to establish if IM in the winter months when vitamin D levels are low may be a greater risk factor for MS than IM in the summer months.

METHODS

We identified all patients with MS diagnosed aged 16-60 in a large primary care database in the United Kingdom and matched each by age, sex, general practice and observation period with up to six controls. We identified a coded diagnosis of IM prior to the index date (date of diagnosis). Logistic regression was used to calculate the odds ratio for prior IM exposure in cases versus controls and for winter versus summer exposure in cases and controls with prior IM exposure.

RESULTS

Based on 9247 cases and 55,033 matched controls (246 and 846 with prior IM respectively), IM was associated with the development of MS (OR 1.77, 95%CI 1.53-2.05) but there was no evidence that IM in the winter as opposed to summer was associated with developing MS (OR 1.09, 95%CI 0.72-1.66).

CONCLUSION

We found no evidence that the season of IM influences the risk of subsequent MS.

Exposure to the Epstein-Barr Viral Antigen Latent Membrane Protein 1 Induces Myelin-Reactive Antibodies In Vivo

Multiple sclerosis (MS) is an autoimmune chronic inflammatory disease of the central nervous system (CNS). Cross-reactivity of neuronal proteins with exogenous antigens is considered one of the possible mechanisms of MS triggering. Previously, we showed that monoclonal myelin basic protein (MBP)-specific antibodies from MS patients cross-react with Epstein–Barr virus (EBV) latent membrane protein 1 (LMP1). In this study, we report that exposure of mice to LMP1 results in induction of myelin-reactive autoantibodies in vivo. We posit that chronic exposure or multiple acute exposures to viral antigen may redirect B cells from production of antiviral antibodies to antibodies, specific to myelin antigen. However, even in inbred animals, which are almost identical in terms of their genomes, such an effect is only observed in 20–50% of animals, indicating that this change occurs by chance, rather than systematically. Cross-immunoprecipitation analysis showed that only part of anti-MBP antibodies from LMP1-immunized mice might simultaneously bind LMP1. In contrast, the majority of anti-LMP1 antibodies from MBP-immunized mice bind MBP. De novo sequencing of anti-LMP1 and anti-MBP antibodies by mass spectrometry demonstrated enhanced clonal diversity in LMP1-immunized mice in comparison with MBP-immunized mice. We suggest that induction of MBP-reactive antibodies in LMP1-immunized mice may be caused by either Follicular dendritic cells (FDCs) or by T cells that are primed by myelin antigens directly in CNS. Our findings help to elucidate the still enigmatic link between EBV infection and MS development, suggesting that myelin-reactive antibodies raised as a response toward EBV protein LMP1 are not truly cross-reactive but are primarily caused by epitope spreading.

Physical activity is associated with a decreased multiple sclerosis risk: The EnvIMS study

Background:

The lifestyle factors smoking and obesity have been associated with the risk of multiple sclerosis (MS). Physical activity (PA) may also be of importance.

Objective:

To examine the association between PA and MS risk in Italy, Norway, and Sweden and to evaluate the possible influence by established risk factors.

Methods:

In this case–control study, 1904 cases and 3694 controls were asked to report their average weekly amounts of light and vigorous PA during adolescence on a scale ranging from none to more than 3 hours activity. We used logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (CIs) and adjusted for potential confounders.

Results:

Vigorous PA was inversely associated with MS risk in the pooled analysis ( p-trend < 0.001) with an age- and sex-adjusted OR of 0.74 (95% CI: 0.63–0.87) when comparing the highest and lowest levels. Adjusting for outdoor activity, infectious mononucleosis, body size, and smoking yielded similar results. The association was present in all countries and was not affected by exclusion of patients with early disease onset. Light PA was not associated with the risk of MS.

Conclusion:

Our findings suggest that vigorous PA can modify the risk of developing MS independent of established risk factors.

Negative interaction between smoking and EBV in the risk of multiple sclerosis: The EnvIMS study

Background:

Results from previous studies on a possible interaction between smoking and Epstein–Barr virus (EBV) in the risk of multiple sclerosis (MS) are conflicting.

Objectives:

To examine the interaction between smoking and infectious mononucleosis (IM) in the risk of MS.

Methods:

Within the case–control study on Environmental Factors In Multiple Sclerosis (EnvIMS), 1904 MS patients and 3694 population-based frequency-matched healthy controls from Norway, Italy, and Sweden reported on prior exposure to smoking and history of IM. We examined the interaction between the two exposures on the additive and multiplicative scale.

Results:

Smoking and IM were each found to be associated with an increased MS risk in all three countries, and there was a negative multiplicative interaction between the two exposures in each country separately as well as in the pooled analysis ( p = 0.001). Among those who reported IM, there was no increased risk associated with smoking (odds ratio (OR): 0.95, 95% confidence interval (CI): 0.66–1.37). The direction of the estimated interactions on the additive scale was consistent with a negative interaction in all three countries (relative excess risk due to interaction (RERI): −0.98, 95% CI: −2.05–0.15, p = 0.09).

Conclusion:

Our findings indicate competing antagonism, where the two exposures compete to affect the outcome.

Clinical Characteristics of Pediatric-Onset and Adult-Onset Multiple Sclerosis in Hispanic Americans

Multiple sclerosis can affect pediatric patients. Our aim was to compare characteristics between pediatric-onset multiple sclerosis and adult-onset multiple sclerosis in Hispanic Americans. This was a cross-sectional analysis of 363 Hispanic American multiple scleroses cases; demographic and clinical characteristics were analyzed. A total of 110 Hispanic patients presented with multiple sclerosis before age 18 and 253 as adult multiple sclerosis. The most common presenting symptoms for both was optic neuritis. Polyfocal symptoms, seizures, and cognitive symptoms at presentation were more prevalent in pediatric-onset multiple sclerosis (P ≤ .001). Transverse myelitis was more frequent in adult-onset multiple sclerosis (P ≤ .001). Using multivariable analysis, pediatric-onset multiple sclerosis (adjusted odds ratio, 0.3OR 95% confidence interval 0.16-0.71, P = .004) and being US born (adjusted odds ratio, 0.553, 95% confidence interval 0.3-1.03, P = .006) were less likely to have severe ambulatory disability. Results suggest that pediatric-onset multiple sclerosis and adult-onset multiple sclerosis in Hispanics have differences that could be important for treatment and prognosis.

Vitamin D, HLA-DRB1 and Epstein-Barr virus antibody levels in a prospective cohort of multiple sclerosis patients

BACKGROUND AND PURPOSE

Our objective was to study the association between serum levels of anti Epstein-Barr virus nuclear antigen 1 (EBNA-1) antibody and 25-hydroxyvitamin D (25(OH)D) in a prospective cohort of patients with relapsing-remitting multiple sclerosis.

METHOD

The study comprised 90 patients with relapsing-remitting multiple sclerosis, all participants in a randomized clinical trial of ω-3 fatty acids (the OFAMS study). Repeated, paired measurements of serum 25(OH)D and serum EBNA-1 immunoglobulin G (IgG) levels were obtained at baseline and every 6 months for 24 months. The association between serum EBNA-1 IgG and serum 25(OH)D levels was analysed using generalized linear models for hierarchical data.

RESULTS

There was a significant variation in EBNA-1 IgG antibody level between sampling months (Fdf 11 = 1.8, P = 0.043, one-way anova). There was a negative association between EBNA-1 IgG and 25(OH)D [B = -0.230, 95% confidence interval (CI) (-0.440, -0.023), P = 0.030] and a positive association between EBNA-1 IgG and HLA-DRB1*15 positive status [B = 94.7, 95% CI (2.423, 186.9), P = 0.044]. The association between 25(OH)D and EBNA-1 IgG remained significant after adjusting for the patient's age, gender, HLA-DRB1*15, retinol levels and interferon β-1a treatment.

CONCLUSION

Our study demonstrates monthly differences in EBNA-1 IgG levels and an association between EBNA-1 IgG, 25(OH)D levels and HLA-DRB1*15. These results indicate that EBNA-1 IgG serum levels are affected by genetic and environmental factors that also modulate multiple sclerosis risk.

Analysis of cellular and humoral immune responses against cytomegalovirus in patients with autoimmune Addison's disease

Background

Autoimmune Addison’s disease (AAD) is caused by multiple genetic and environmental factors. Variants of genes encoding immunologically important proteins such as the HLA molecules are strongly associated with AAD, but any environmental risk factors have yet to be defined. We hypothesized that primary or reactivating infections with cytomegalovirus (CMV) could represent an environmental risk factor in AAD, and that CMV specific CD8⁺ T cell responses may be dysregulated, possibly leading to a suboptimal control of CMV. In particular, the objective was to assess the HLA-B8 restricted CD8⁺ T cell response to CMV since this HLA class I variant is a genetic risk factor for AAD.

Methods

To examine the CD8⁺ T cell response in detail, we analyzed the HLA-A2 and HLA-B8 restricted responses in AAD patients and healthy controls seropositive for CMV antibodies using HLA multimer technology, IFN-γ ELISpot and a CD107a based degranulation assay.

Results

No differences between patients and controls were found in functions or frequencies of CMV-specific T cells, regardless if the analyses were performed ex vivo or after in vitro stimulation and expansion. However, individual patients showed signs of reactivating CMV infection correlating with poor CD8⁺ T cell responses to the virus, and a concomitant upregulation of interferon regulated genes in peripheral blood cells. Several recently diagnosed AAD patients also showed serological signs of ongoing primary CMV infection.

Conclusions

CMV infection does not appear to be a major environmental risk factor in AAD, but may represent a precipitating factor in individual patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-0822-z) contains supplementary material, which is available to authorized users.

The Norwegian Multiple Sclerosis Registry and Biobank

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system with unknown cause and various benefits from disease modifying therapies. Systematic recording of data into national MS registries is therefore needed to optimize treatment and define the pathogenesis of the disease. The Norwegian MS Registry and Biobank was established for systematic collection of clinical and epidemiological data, as well as biological samples. Data collection is based on informed consent from the individual patients and recordings by treating neurologists. All researchers have, by application, access to data and biological samples from the Norwegian Multiple Sclerosis Registry and Biobank. By this combined effort from both patients and healthcare personnel, the Registry and Biobank aims to facilitate research for improved understanding of disease mechanisms and improved health care in MS.

Multiple sclerosis and environmental factors: the role of vitamin D, parasites, and Epstein-Barr virus infection

Pathogenic mechanisms underlying multiple sclerosis development have yet to be clearly identified, but considerable evidence indicates that autoimmunity plays an important role in the etiology of the disease. It is generally accepted that autoimmune diseases like MS arise from complex interactions between genetic susceptibility and environmental factors. Although environmental factors unequivocally influencing MS development have yet to be established, accumulating evidence singles out several candidates, including sunlight-UV exposure or vitamin D deficiency, viral infections, hygiene, and cigarette smoking. Vitamin D deficiency has been associated with different autoimmune diseases. Several investigations indicate 125 (OH)2 vitamin D plays a critical role in shaping T-cell response and inducing T cells with immunosuppressive properties. Likewise, helminth infections represent another potential environmental factor exerting immunomodulatory properties. Both epidemiological and experimental data provide evidence to support autoimmune down-regulation secondary to parasite infections in patients with MS, through regulatory T- and B-cell action, with effects extending beyond simple response to an infectious agent. Finally, different epidemiological studies have demonstrated that Epstein-Barr virus infection confers added risk of developing MS. Proposed mechanisms responsible for this association include activation and expansion of self-reactive T and B cells, lower threshold for self-tolerance breakdown, and enhanced autoreactive B-cell survival, all to be discussed in this review. Understanding environmental factors influencing propensity to MS will lead to new and more effective approaches to prevent and treat the disease.

Level of education and multiple sclerosis risk after adjustment for known risk factors: The EnvIMS study

BACKGROUND

Several recent studies have found a higher risk of multiple sclerosis (MS) among people with a low level of education. This has been suggested to reflect an effect of smoking and lower vitamin D status in the social class associated with lower levels of education.

OBJECTIVE

The objective of this paper is to investigate the association between level of education and MS risk adjusting for the known risk factors smoking, infectious mononucleosis, indicators of vitamin D levels and body size.

METHODS

Within the case-control study on Environmental Factors In MS (EnvIMS), 953 MS patients and 1717 healthy controls from Norway reported educational level and history of exposure to putative environmental risk factors.

RESULTS

Higher level of education were associated with decreased MS risk (p trend = 0.001) with an OR of 0.53 (95% CI 0.41-0.68) when comparing those with the highest and lowest level of education. This association was only moderately reduced after adjusting for known risk factors (OR 0.61, 95% CI 0.44-0.83). The estimates remained similar when cases with disease onset before age 28 were excluded.

CONCLUSION

These findings suggest that factors related to lower socioeconomic status other than established risk factors are associated with MS risk.

The role of geographical ecological studies in identifying diseases linked to UVB exposure and/or vitamin D

Using a variety of approaches, researchers have studied the health effects of solar ultraviolet (UV) radiation exposure and vitamin D. This review compares the contributions from geographical ecological studies with those of observational studies and clinical trials. Health outcomes discussed were based on the author's knowledge and include anaphylaxis/food allergy, atopic dermatitis and eczema, attention deficit hyperactivity disorder, autism, back pain, cancer, dental caries, diabetes mellitus type 1, hypertension, inflammatory bowel disease, lupus, mononucleosis, multiple sclerosis, Parkinson disease, pneumonia, rheumatoid arthritis, and sepsis. Important interactions have taken place between study types; sometimes ecological studies were the first to report an inverse correlation between solar UVB doses and health outcomes such as for cancer, leading to both observational studies and clinical trials. In other cases, ecological studies added to the knowledge base. Many ecological studies include other important risk-modifying factors, thereby minimizing the chance of reporting the wrong link. Laboratory studies of mechanisms generally support the role of vitamin D in the outcomes discussed. Indications exist that for some outcomes, UVB effects may be independent of vitamin D. This paper discusses the concept of the ecological fallacy, noting that it applies to all epidemiological studies.

The Role of Environment and Lifestyle in Determining the Risk of Multiple Sclerosis

MS is a complex disease where both genetic and environmental factors contribute to disease susceptibility. The substantially increased risk of developing MS in relatives of affected individuals gives solid evidence for a genetic base for susceptibility, whereas the modest familial risk, most strikingly demonstrated in the twin studies, is a very strong argument for an important role of lifestyle/environmental factors in determining the risk of MS, sometimes interacting with MS risk genes. Lifestyle factors and environmental exposures are harder to accurately study and quantify than genetic factors. However, it is important to identify these factors since they, as opposed to risk genes, are potentially preventable. We have reviewed the evidence for environmental factors that have been repeatedly shown to influence the risk of MS: Epstein-Barr virus (EBV) infection, ultraviolet radiation (UVR) exposure habits /vitamin D status, and smoking. We have also reviewed a number of additional environmental factors, published in the past 5 years, that have been described to influence MS risk. Independent replication, preferably by a variety of methods, may give still more firm evidence for their involvement.

The EnvIMS Study: Design and Methodology of an International Case-Control Study of Environmental Risk Factors in Multiple Sclerosis

Background: Multiple sclerosis (MS) is a chronic disease of the central nervous system, often resulting in significant neurological disability. The causes of MS are not known; however, the incidence of MS is increasing, thereby suggesting that changes in lifestyle and/or environmental factors may be responsible. On this background, the Environmental Risk Factors in MS Study or EnvIMS study was designed to further explore the etiology of MS. The design and methodology are described, providing details to enable investigators to (i) use our experiences to design their own studies; (ii) take advantage of, and build on the methodological work completed for, the EnvIMS study; (iii) become aware of this data source that is available for use by the research community. Methods: EnvIMS is a multinational case-control study, enrolling 2,800 cases with MS and 5,012 population-based controls in Canada, Italy, Norway, Serbia and Sweden. The study was designed to investigate the most commonly implicated risk factors for MS etiology using a self-report questionnaire. Results/Conclusions: The use of a common methodology to study MS etiology across several countries enhances the comparability of results in different geographic regions and research settings, reduces the resources required for study design and enhances the opportunity for data harmonization.

Vitamin D Actions on CD4(+) T Cells in Autoimmune Disease

This review summarizes and integrates research on vitamin D and CD4⁺ T-lymphocyte biology to develop new mechanistic insights into the molecular etiology of autoimmune disease. A deep understanding of molecular mechanisms relevant to gene–environment interactions is needed to deliver etiology-based autoimmune disease prevention and treatment strategies. Evidence linking sunlight, vitamin D, and the risk of multiple sclerosis and type 1 diabetes is summarized to develop the thesis that vitamin D is the environmental factor that most strongly influences autoimmune disease development. Evidence for CD4⁺ T-cell involvement in autoimmune disease pathogenesis and for paracrine calcitriol signaling to CD4⁺ T lymphocytes is summarized to support the thesis that calcitriol is sunlight’s main protective signal transducer in autoimmune disease risk. Animal modeling and human mechanistic data are summarized to support the view that vitamin D probably influences thymic negative selection, effector Th1 and Th17 pathogenesis and responsiveness to extrinsic cell death signals, FoxP3⁺CD4⁺ T-regulatory cell and CD4⁺ T-regulatory cell type 1 (Tr1) cell functions, and a Th1–Tr1 switch. The proposed Th1–Tr1 switch appears to bridge two stable, self-reinforcing immune states, pro- and anti-inflammatory, each with a characteristic gene regulatory network. The bi-stable switch would enable T cells to integrate signals from pathogens, hormones, cell–cell interactions, and soluble mediators and respond in a biologically appropriate manner. Finally, unanswered questions and potentially informative future research directions are highlighted to speed delivery of etiology-based strategies to reduce autoimmune disease.

Detection of the Epstein-Barr virus, Human Bocavirus and novel KI and KU polyomaviruses in adenotonsillar tissues

OBJECTIVES

We aimed to investigate the seasonal disturbations and the rates of detection of Epstein-Barr virus (EBV), Human Bocavirus (HBoV), and polyomaviruses KI and WU (KIPyV and WUPyV) in adenoid and tonsil tissues during the absence of acute infection symptoms.

STUDY DESIGN

Cross-sectional prospective study.

SETTING

Tertiary hospital.

METHODS

DNA expressions of EBV, HBoV, polyomaviruses KIPyV and WUPyV were investigated in children with chronic tonsillar and adenoidal diseases using real-time polymerase chain reaction. The patients were grouped as follows: adenoid, recurrent tonsillitis and hypertrophic tonsillitis group. The relationships of the expressions of these viruses with age, gender, recurrent infection and airway obstruction were also analyzed. Seasonal variations in rates of detection of these viruses in adenoid and tonsil tissues were also investigated.

RESULTS

Considering adenoid specimens, HBoV was found to be the most frequent virus with the rate of 43.1%. In specimens of recurrent tonsillitis and hypertrophic tonsils, EBV was the most frequently encountered virus (53.8%, and 32.0%, respectively). In children with hypertrophic adenoids, while HBoV was detected to be positive throughout the year, EBV was present throughout the year in children with recurrent tonsillitis.

CONCLUSIONS

The detection of HBoV and EBV throughout the year in samples of children with asymptomatic chronic adenotonsillar diseases may indicate that these viruses may remain persistently in lymphoepithelial tissues of upper respiratory tract. Virus persistence may have a pathogenetic potential for development of lymphoid hypertrophy and a chronic stimulatory effect for inflammation.