Haplotype of IL-8 -251T and 781C is associated with the susceptibility to respiratory syncytial virus

Impact of genetic polymorphisms related to innate immune response on respiratory syncytial virus infection in children

Respiratory syncytial virus (RSV) causes lower respiratory tract infections and bronchiolitis, mainly affecting children under 2 years of age and immunocompromised patients. Currently, there are no available vaccines or efficient pharmacological treatments against RSV. In recent years, tremendous efforts have been directed to understand the pathological mechanisms of the disease and generate a vaccine against RSV. Although RSV is highly infectious, not all the patients who get infected develop bronchiolitis and severe disease. Through various sequencing studies, single nucleotide polymorphisms (SNPs) have been discovered in diverse receptors, cytokines, and transcriptional regulators with crucial role in the activation of the innate immune response, which is implicated in the susceptibility to develop or protect from severe forms of the infection. In this review, we highlighted how variations in the key genes affect the development of innate immune response against RSV. This data would provide crucial information about the mechanisms of viral infection, and in the future, could help in generation of new strategies for vaccine development or generation of the pharmacological treatments.

Impact of IL-8-251A/T gene polymorphism on severity of disease caused by enterovirus 71 infection

The study was performed in EV71-infected patients, with 97 mild cases and 80 severe cases. IL-8251A/T genotypes were determined by the polymerase chain reaction restriction fragment length polymorphism technique. Severe cases had a significantly higher frequency of the IL8-251 AT and TT genotypes than mild cases (52.5 % vs. 49.5 % and 42.5 % vs. 30.9 %, respectively; p = 0.024). The frequency of IL-8-251T alleles among the severe cases was also significantly higher than that of mild cases (68.7 % vs. 55.7 %, OR = 1.8, 95 % CI = 1.1-2.7, p = 0.012). There were significant differences in gender, age, fever days, WBC, CRP and BG concentration, and IL-8 levels among genotypes of IL-8251A/T in EV71-infected patients, but there were no significant differences in ALT, AST, CK-MB and EV71 loads. These findings suggested that the IL-8-251T allele is associated with susceptibility to severe disease in Chinese patients infected with EV71.

Association of Enterovirus 71 encephalitis with the interleukin-8 gene region in Chinese children

The study was performed in 36 Chinese patients with Enterovirus 71 (EV71) encephalitis and 141 patients with EV71-related hand, foot and mouth disease (HFMD) without encephalitis. Genotyping was determined by polymerase chain reaction- restriction fragment length polymorphism. Patients with EV71 encephalitis had a significantly higher frequency of interleukin-8 (IL-8)-251TT genotype than patients with EV71-related HFMD without encephalitis (55.6% vs 31.2%, p = 0.023). The frequency of IL-8-251T alleles was significantly higher among patients with EV71 encephalitis than in patients with EV71-related HFMD without encephalitis (72.2% vs 58.9%, odds ratio 1.8, 95% confidence interval 1.0-3.2, p = 0.038). There were significant differences in gender, age, fever days, white blood cell count, C-reactive protein and blood glucose concentration and IL-8 levels among genotypes of IL-8-251A/T in EV71-infected patients, but no significant differences in alanine or aspartate aminotransferase, creatine kinase-myocardial isozyme and cerebrospinal fluid in patients with EV71 encephalitis. These findings suggest that the IL-8-251T allele is associated with susceptibility to EV71 encephalitis in Chinese patients.

Genetic polymorphism of CCL2-2518, CXCL10-201, IL8+781 and susceptibility to severity of Enterovirus-71 infection in a Chinese population

OBJECTIVE

The goal of this study was to examine the relationship between CCL2-2518A/G, CXCL10-201A/G, and IL8+781C/T gene polymorphism and severity of Enterovirus 71 (EV71) infection in a Chinese population.

METHODS

A case-control study was conducted to compare the distribution of genotype and genetic frequency of the CCL2-2518A/G, CXCL10-201A/G, and IL8+781C/T gene polymorphisms among EV71-infected patients (n = 186), including mild cases (n = 103), severe cases (n = 83) and healthy control subjects (n = 233) with polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and analyzed the relationship between the CCL2-2518A/G, CXCL10-201A/G, and IL8+781C/T gene polymorphism and the susceptibility to EV71 infection.

RESULTS

No significant differences were found in the distribution of genotype CCL2-2518A/G, CXCL10-201A/G, and IL8+781C/T between the healthy control group and EV71-infected patients. However, three SNPs were associated with severity of EV71 infection: the G allele (genotypes AG or GG) in the CCL2-2518A/G (OR 2.34, 95 % CI 1.50-3.65, P < 0.001), the A allele (genotypes AA or AG) in the CXCL10-201A/G (OR 3.60, 95 % CI 1.73-7.47, P < 0.001), and the C allele (genotypes CC or CT) in the IL8+781C/T (OR 2.63, 95 % CI 1.67-4.13, P < 0.001) were more frequent in patients with severe EV71 infection. No significant difference was observed between EV71 encephalitis and severe cases. At the same time, there were significant differences in fever days, WBC, CRP and BG concentration, and CCL2, CXCL10 and IL-8 levels according to the three SNPs among 186 EV71-infected patients, but no significant differences were observed in gender, age, ALT, AST, CK-MB, and CSF evaluations.

CONCLUSION

The G carrier of the CCL2-2518A/G, the A carrier of the CXCL10-201A/G, and the C carrier of the IL8+781C/T were found to be associated with severity of EV71 infection, and could be susceptibility factors in the development of EV71 infection in the Chinese population.

Respiratory syncytial virus--a comprehensive review

Respiratory syncytial virus (RSV) is amongst the most important pathogenic infections of childhood and is associated with significant morbidity and mortality. Although there have been extensive studies of epidemiology, clinical manifestations, diagnostic techniques, animal models and the immunobiology of infection, there is not yet a convincing and safe vaccine available. The major histopathologic characteristics of RSV infection are acute bronchiolitis, mucosal and submucosal edema, and luminal occlusion by cellular debris of sloughed epithelial cells mixed with macrophages, strands of fibrin, and some mucin. There is a single RSV serotype with two major antigenic subgroups, A and B. Strains of both subtypes often co-circulate, but usually one subtype predominates. In temperate climates, RSV infections reflect a distinct seasonality with onset in late fall or early winter. It is believed that most children will experience at least one RSV infection by the age of 2 years. There are several key animal models of RSV. These include a model in mice and, more importantly, a bovine model; the latter reflects distinct similarity to the human disease. Importantly, the prevalence of asthma is significantly higher amongst children who are hospitalized with RSV in infancy or early childhood. However, there have been only limited investigations of candidate genes that have the potential to explain this increase in susceptibility. An atopic predisposition appears to predispose to subsequent development of asthma and it is likely that subsequent development of asthma is secondary to the pathogenic inflammatory response involving cytokines, chemokines and their cognate receptors. Numerous approaches to the development of RSV vaccines are being evaluated, as are the use of newer antiviral agents to mitigate disease. There is also significant attention being placed on the potential impact of co-infection and defining the natural history of RSV. Clearly, more research is required to define the relationships between RSV bronchiolitis, other viral induced inflammatory responses, and asthma.

Characterization of the resistance of SJL/J mice to pneumonia virus of mice, a model for infantile bronchiolitis due to a respiratory syncytial virus

Respiratory syncytial virus (RSV), a prominent cause of airway morbidity in children, maintains an excessive hospitalization rate despite decades of research. Host factors are assumed to influence the disease severity. As a first step toward identifying the underlying resistance mechanisms, we recently showed that inbred mouse strains differ dramatically as regards their susceptibility to pneumonia virus of mice (PVM), the murine counterpart of RSV. PVM infection in mice has been shown to faithfully mimic the severe RSV disease in human infants. This study aimed at dissecting the remarkable PVM-resistance shown by the SJL/J strain. To characterize its genetic component, we assessed clinical, physiopathological, and virological resistance/susceptibility traits in large first (F1) and second (F2) generations obtained by crossing the SJL/J (resistant) and 129/Sv (susceptible) strains. Then, to acquire conclusive in vivo evidence in support of the hypothesis that certain radiosensitive hematopoietic cells might play a significant role in PVM-resistance, we monitored the same resistance/susceptibility traits in mock- and γ-irradiated SJL/J mice. Segregation analysis showed that (i) PVM-resistance is polygenic, (ii) the resistance alleles are recessive, and (iii) all resistance-encoding alleles are concentrated in SJL/J. Furthermore, there was no alteration of SJL/J PVM-resistance after immunosuppression by γ-irradiation, which suggests that adaptive immunity is not involved. We conclude that host resistance to pneumoviruses should be amenable to genetic dissection in this mouse model and that radioresistant lung epithelial cells and/or alveolar macrophages may control the clinical severity of pneumovirus-associated lung disease.

Pattern recognition receptors and genetic risk for rsv infection: value for clinical decision-making?

Respiratory syncytial virus (RSV) causes respiratory tract infections, especially among young infants. Practically, all infants are infected during epidemics and the clinical presentation ranges from subclinical to fatal infection. Known risk factors for severe RSV infection include prematurity, age of <2 months, underlying chronic lung or heart diseases, serious neurological or metabolic disorders, immune deficiency (especially a disorder of cellular immunity), crowded living conditions, and indoor smoke pollution. Twin studies indicate that host genetic factors affect susceptibility to severe RSV infection. Pattern recognition receptors (PRRs) are the key mediators of the innate immune response to RSV. In the distal respiratory tract, RSV is recognized by the transmembrane Toll-like receptor 4 (TLR4) and adapter proteins, which lead to production of proinflammatory cytokines and subsequent activation of the adaptive immune response. Surfactant proteins A and D are able to bind both RSV and TLR4, modulating the inflammatory response. Genetic variations in TLR4, SP-A, and SP-D have been associated with the risk of severe RSV bronchiolitis, but the results have varied between studies. Both the homozygous hyporesponsive 299Gly genotype of TLR4 and the non-synonymous SP-A and SP-D polymorphism influence the presentation of RSV infection. The reported relative risks associated with these markers are not robust enough to justify clinical use. However, current evidence indicates that innate immune responses including pattern recognition receptors (PRRs) and other components in the distal airways and airspaces profoundly influence the innate immune responses, playing a key role in host resistance to RSV in young infants. This information is useful in guiding efforts to develop better means to identify the high-risk infants and to treat this potentially fatal infection effectively.

The role of cytokines and chemokines in severe respiratory syncytial virus infection and subsequent asthma

Respiratory syncytial virus (RSV) is the primary cause of serious lower respiratory tract illness in infants and young children worldwide. The mechanism is largely unknown. RSV stimulates airway epithelial cells and resident leukocytes to release cytokines. Cytokines and chemokines involved in host response to RSV infection are thought to play a central role in the pathogenesis. In addition, RSV infection early in life has been associated with the development of asthma in later childhood. It is likely that the persistence of cytokines and chemokines in fully recovered patients with RSV in the long term can provide a substratum for the development of subsequent asthma. This review describes the genetic factors in cytokines and chemokines associated with severity of RSV disease, cytokines and chemokines synthesis in RSV infection, and the role of these innate immune components in RSV-associated asthma.