Zheng Quan Toh

Probiotic Therapy as a Novel Approach for Allergic Disease

The prevalence of allergic disease has increased dramatically in Western countries over the past few decades. The hygiene hypothesis, whereby reduced exposure to microbial stimuli in early life programs the immune system toward a Th2-type allergic response, is suggested to be a major mechanism to explain this phenomenon in developed populations. Such microbial exposures are recognized to be critical regulators of intestinal microbiota development. Furthermore, intestinal microbiota has an important role in signaling to the developing mucosal immune system. Intestinal dysbiosis has been shown to precede the onset of clinical allergy, possibly through altered immune regulation. Existing treatments for allergic diseases such as eczema, asthma, and food allergy are limited and so the focus has been to identify alternative treatment or preventive strategies. Over the past 10 years, a number of clinical studies have investigated the potential of probiotic bacteria to ameliorate the pathological features of allergic disease. This novel approach has stemmed from numerous data reporting the pleiotropic effects of probiotics that include immunomodulation, restoration of intestinal dysbiosis as well as maintaining epithelial barrier integrity. In this mini-review, the emerging role of probiotics in the prevention and/or treatment of allergic disease are discussed with a focus on the evidence from animal and human studies.

Protecting against Pneumococcal Disease: Critical Interactions between Probiotics and the Airway Microbiome

Streptococcus pneumoniae (the pneumococcus) is a predominant cause of pneumonia, meningitis, and bacteremia. It is a leading killer of children under 5 years of age, responsible for the deaths of up to 2 million children annually [1]. Most deaths occur in African and Asian developing countries; however, pneumococcal disease is also a significant problem in particular populations of developed countries, such as the North American Indians, and indigenous Alaskans and Australians [1]–[3]. Although vaccination is the most cost-effective method of protection against pneumococcal disease, cost remains a barrier, as does vaccine delivery and efficacy. In this opinion piece, we discuss the potential complementary role of probiotics to vaccines in preventing pneumococcal disease through targeting the microbiome of the upper respiratory tract.

Inhibition of Streptococcus pneumoniae adherence to human epithelial cells in vitro by the probiotic Lactobacillus rhamnosus GG

BackgroundColonization of the nasopharynx by Streptococcus pneumoniae is considered a prerequisite for pneumococcal infections such as pneumonia and otitis media. Probiotic bacteria can influence disease outcomes through various mechanisms, including inhibition of pathogen colonization. Here, we examine the effect of the probiotic Lactobacillus rhamnosus GG (LGG) on S. pneumoniae colonization of human epithelial cells using an in vitro model. We investigated the effects of LGG administered before, at the same time as, or after the addition of S. pneumoniae on the adherence of four pneumococcal isolates.ResultsLGG significantly inhibited the adherence of all the pneumococcal isolates tested. The magnitude of inhibition varied with LGG dose, time of administration, and the pneumococcal isolate used. Inhibition was most effective when a higher dose of LGG was administered prior to establishment of pneumococcal colonization. Mechanistic studies showed that LGG binds to epithelial cells but does not affect pneumococcal growth or viability. Administration of LGG did not lead to any significant changes in host cytokine responses.ConclusionsThese findings demonstrate that LGG can inhibit pneumococcal colonization of human epithelial cells in vitro and suggest that probiotics could be used clinically to prevent the establishment of pneumococcal carriage.

Anti-Inflammatory Effects of Vitamin D on Human Immune Cells in the Context of Bacterial Infection

Vitamin D induces a diverse range of biological effects, including important functions in bone health, calcium homeostasis and, more recently, on immune function. The role of vitamin D during infection is of particular interest given data from epidemiological studies suggesting that vitamin D deficiency is associated with an increased risk of infection. Vitamin D has diverse immunomodulatory functions, although its role during bacterial infection remains unclear. In this study, we examined the effects of 1,25(OH)2D3, the active metabolite of vitamin D, on peripheral blood mononuclear cells (PBMCs) and purified immune cell subsets isolated from healthy adults following stimulation with the bacterial ligands heat-killed pneumococcal serotype 19F (HK19F) and lipopolysaccharide (LPS). We found that 1,25(OH)2D3 significantly reduced pro-inflammatory cytokines TNF-α, IFN-γ, and IL-1β as well as the chemokine IL-8 for both ligands (three- to 53-fold), while anti-inflammatory IL-10 was increased (two-fold, p = 0.016) in HK19F-stimulated monocytes. Levels of HK19F-specific IFN-γ were significantly higher (11.7-fold, p = 0.038) in vitamin D-insufficient adults (<50 nmol/L) compared to sufficient adults (>50 nmol/L). Vitamin D also shifted the pro-inflammatory/anti-inflammatory balance towards an anti-inflammatory phenotype and increased the CD14 expression on monocytes (p = 0.008) in response to LPS but not HK19F stimulation. These results suggest that 1,25(OH)2D3 may be an important regulator of the inflammatory response and supports further in vivo and clinical studies to confirm the potential benefits of vitamin D in this context.

The contrasting roles of Th17 immunity in human health and disease

The human immune system is a tightly regulated network that protects the host from disease. An important aspect of this is the balance between pro‐inflammatory Th17 cells and anti‐inflammatory T regulatory (Treg) cells in maintaining immune homeostasis. Foxp3+ Treg are critical for sustaining immune tolerance through IL‐10 and transforming growth factor‐β while related orphan receptor‐γt+ Th17 cells promote immunopathology and auto‐inflammatory diseases through the actions of IL‐17A, IL‐21 and IL‐22. Therefore, imbalance between Treg and Th17 cells can result in serious pathology in many organs and tissues. Recently, certain IL‐17‐producing cells have been found to be protective against infectious disease, particularly in relation to extracellular bacteria such Streptococcus pneumoniae; a number of other novel IL‐17‐secreting cell populations have also been reported to protect against a variety of other pathogens. In this mini‐review, the dual roles of Treg and Th17 cells are discussed in the context of autoimmunity and infections, highlighting recent advances in the field. Development of novel strategies specifically designed to target these critical immune response pathways will become increasingly important in maintenance of human health.

Reduced dose human papillomavirus vaccination: An update of the current state-of-the-art

Human papillomavirus (HPV) infection is the primary cause of genital warts, some oropharyngeal cancers and anogenital cancers, including cervical, vagina, vulvar, anal and penile cancers. Primary prevention of cervical cancer requires the prevention of high-risk HPV infections, particularly HPV genotypes 16 and 18. Both Gardasil® and Cervarix® vaccines when administered by a three-dose schedule have been demonstrated to be effective against cervical, vulva, and vaginal cancer precursors from vaccine genotypes in phase III clinical trials, and post-marketing studies; Gardasil® vaccine also offers additional protection against anal cancer precursors. However, high costs of HPV vaccines and the logistics of delivering a three-dose schedule over 6 months are challenging in countries with limited resources. Several studies have demonstrated non-inferiority in antibody response between adolescents (9-15 years old) who received two doses (6 months apart) and women (>15 years old) who received the standard three-dose schedule. These studies provided evidence for the World Health Organization and European Medical Association to revise its recommendation to give two instead of three doses of HPV vaccine to adolescents below 15 years of age, provided the 2nd dose is given 6 months apart. Although reduced dose schedules can alleviate costs and logistics associated with HPV vaccination, especially in resource-poor countries, there are still gaps in this area of research, particularly regarding long-term protection. This review discusses the findings on antibody response and clinical outcomes in studies evaluating reduced dose HPV schedules, and highlights the important considerations of its implementation. In addition, other important immunological biomarkers that may be associated with long-term protection are highlighted and discussed.

Reduced IL-17A Secretion Is Associated with High Levels of Pneumococcal Nasopharyngeal Carriage in Fijian Children

Streptococcus pneumonia (the pneumococcus) is the leading vaccine preventable cause of serious infections in infants under 5 years of age. The major correlate of protection for pneumococcal infections is serotype-specific IgG antibody. More recently, antibody-independent mechanisms of protection have also been identified. Preclinical studies have found that IL-17 secreting CD4+ Th17 cells in reducing pneumococcal colonisation. This study assessed IL-17A levels in children from Fiji with high and low pneumococcal carriage density, as measured by quantitative real-time PCR (qPCR). We studied Th17 responses in 54 children who were designated as high density carriers (N=27, >8.21x105 CFU/ml) or low density carriers (N=27, <1.67x105 CFU/ml). Blood samples were collected, and isolated peripheral blood mononuclear cells (PBMCs) were stimulated for 6 days. Supernatants were harvested for cytokine analysis by multiplex bead array and/or ELISA. Th17 cytokines assayed included IL-17A, IL-21, IL-22 as well as TNF-α, IL-10, TGF-β, IL-6, IL-23 and IFNγ. Cytokine levels were significantly lower in children with high density pneumococcal carriage compared with children with low density carriage for IL-17A (p=0.002) and IL-23 (p=0.04). There was a trend towards significance for IL-22 (p=0.057) while no difference was observed for the other cytokines. These data provide further support for the role of Th17-mediated protection in humans and suggest that these cytokines may be important in the defence against pneumococcal carriage.

Sustained antibody responses 6 years following 1, 2, or 3 doses of quadrivalent Human Papillomavirus (HPV) vaccine in adolescent Fijian girls, and subsequent responses to a single dose of bivalent HPV vaccine: a prospective cohort study

Background The duration of antibody response following reduced human papillomavirus (HPV) vaccine doses has not been determined. We compared the antibody responses in girls previously vaccinated with zero, 1, 2, or 3 doses of quadrivalent HPV vaccine (4vHPV; Gardasil, Merck) 6 years previously. Methods A prospective cohort study was undertaken in 200 Fijian girls 15-19 years of age. Approximately equal numbers of girls from 2 main ethnic groups (Fijians of Indian descent [FID] and Indigenous Fijians [iTaukei]) in Fiji were recruited for each dosage groups. Blood was drawn before and 28 days following a single dose of bivalent HPV vaccine (2vHPV; Cervarix, GlaxoSmithKline). We measured neutralizing antibodies (NAb) against HPV-6, -11, -16, and -18 using the pseudovirion-based neutralization assay. Results After 6 years (before a dose of 2vHPV was given), the geometric mean NAb titers for all 4 HPV types were not statistically different between 2-dose (2D) and 3-dose (3D) recipients: HPV-6 (3D: 2216 [95% confidence interval {CI},1695-2896]; 2D: 1476 [95% CI, 1019-2137]; P = .07), HPV-11 (3D: 4431 [95% CI, 3396-5783]; 2D: 2951 [95% CI, 1984-4390]; P = .09), HPV-16 (3D: 3373 [95% CI, 2511-4530]; 2D: 3275 [95% CI, 2452-4373]; P = .89); HPV-18 (3D: 628 [95% CI: 445-888]; 2D: 606 [95% CI, 462-862]; P = .89), and were higher in FID than iTaukei girls. Although 1-dose recipients had significantly lower NAb titers than 2-/3-dose recipients, their NAb titers were 5- to 30-fold higher than unvaccinated girls. Post-2vHPV NAb titers against HPV-16 and -18 were not statistically different between girls who received 1, 2, or 3 doses of 4vHPV previously. Conclusions Two doses of 4vHPV provide similar NAb titers as 3 doses for 6 years, although the clinical significance is unknown. A single dose of 4vHPV elicits antibodies that persisted for at least 6 years, and induced immune memory, suggesting possible protection against HPV vaccine types after a single dose of 4vHPV.

Cervical Cancer Prevention Through HPV Vaccination in Low- and Middle-Income Countries in Asia

Cervical cancer is ranked the first or second most common cancer in women of low- and middle-income countries (LMICs) in Asia. Cervical cancer is almost exclusively caused by human papillomavirus (HPV), and majority of the cases can be prevented with the use of HPV vaccines. The HPV vaccines have demonstrated high vaccine efficacies against HPV infection and cervical cancer precursors in clinical and post-marketing studies, and are in use in most high-income countries. However, their use in LMICs are limited mainly due to the high costs and logistics in delivering multiple doses of the vaccine. Other issues such as the safety of the vaccines, social and cultural factors, as well as poor knowledge and awareness of the virus have also contributed to the low uptake of the vaccine. This mini-review focuses on the need for HPV vaccine implementation in Asia given the substantial disease burden and underuse of HPV vaccines in LMICs in this region. In addition, the progress towards HPV vaccine introduction, and barriers preventing further rollout of these essential, life-saving vaccines are also discussed in this article.

Anti-inflammatory Effects of Probiotics and Their Metabolites: Possible Role for Epigenetic Effects

It may well be the case that an important part of future medicine is directed not only in the development of novel therapies which restore gut microbiota but also in the administration of preventative strategies through dietary intervention. Dietary changes contribute to 57 % of the total structural variation in gut microbiota, whereas genetic differences attribute no more than 12 %. As such a diet that is rich in complex carbohydrates not only promotes a healthy gut microbiota but also boosts the production of immunomodulatory short chain fatty acids (SCFA) which have HDAC inhibitory properties. Histone deacetylase inhibitors (HDACi) have been observed across a wide range of naturally derived compounds which include sulforaphane from broccoli, diallyl disulfide from garlic, and curcumin from turmeric. Identification of potent anti-inflammatory effects of dietary compounds is worth investigating, particularly due to wide accessibility by the general public. Although our current knowledge of restoring gut microbiota through administration of probiotics and their metabolites and naturally derived HDACi is not complete. Future research is required to understand the mechanistic actions and pharmacokinetics involved in dietary HDACi and probiotics to aid in future developments of therapeutic modalities for the treatment of chronic inflammatory diseases. In this chapter we discuss the inflammasomes related in health and disease and outline current and novel therapies for the treatment of chronic inflammatory diseases including allergies, inflammatory bowel diseases, metabolic syndromes, and autism spectrum disorders.