Distinct Antiviral Properties of Two Different Bacterial Lysates

Short-term administration of Qipian®, a mixed bacterial lysate, inhibits airway inflammation in ovalbumin-induced mouse asthma by modulating cellular, humoral and neurogenic immune responses

AIMS

Qipian® is a commercialized agent composed of extracts of three genera of commensal bacteria, and its mechanism of action on asthma is unclear. This study aimed to examine the impact of Qipian® on airway inflammation and investigate the underlying mechanisms.

MATERIALS AND METHODS

Qipian® or dexamethasone (DEX) was administered before OVA challenge in an ovalbumin-induced asthma mouse model, and then asthmatic symptoms were observed and scored. Samples of lung tissues, blood, and bronchoalveolar lavage fluid (BALF) were collected, and eosinophils (Eos), immunoglobins (Igs), and type 1 T helper (Th1)/Th2 cell cytokines were measured. Mucus production in the lung was assessed by periodic acid-Schiff (PAS) staining. The effects of Qipian® on dendritic and T regulatory (Treg) cells were investigated using flow cytometry.

KEY FINDINGS

The short-term administration of Qipian® significantly inhibited the cardinal features of allergic asthma, including an elevated asthmatic behaviour score, airway inflammation and immune response. Histological analysis of the lungs showed that Qipian® attenuated airway inflammatory cell infiltration and mucus hyperproduction. Qipian® restored Th1/Th2 imbalance by decreasing interleukin (IL)-4, IL-5, and IL-13 while increasing interferon (IFN)-γ and IL-10. Further investigation revealed that Qipian® treatment induced the upregulation of CD4+CD25+Foxp3+ Treg cells and CD103+ DCs and downregulation of tachykinins neurokinin A (NKA) and NKB in the lung.

SIGNIFICANCE

Our findings suggested that short-term treatment with Qipian® could alleviate inflammation in allergic asthma through restoring the Th1/Th2 balance by recruiting Treg cells to airways and inducing the proliferation of CD103+ DCs, which actually provides a new treatment option for asthma.

The return of the mixed respiratory bacterial vaccine

Background: Orally or sublingually administered lysates of mixed respiratory pathogenic bacteria have been used in Europe, Asia, and other parts of the world, but not the United States, since the mid 1950s, first to prevent recurrent respiratory tract infections, later to prevent wheezing and asthma exacerbations associated with respiratory infections, and, more recently, for the treatment of allergic rhinitis. The apparent success of this treatment contrasts with the negative experience of treating with injections of similar mixed respiratory bacterial vaccines (MRBV or BV) to prevent asthma exacerbations associated with respiratory infections that was once common practice but abandoned ∼50 years ago. Methods: Textbooks and articles on the use of injected BVs to prevent asthma exacerbations associated with respiratory infections were reviewed, including a number of, randomized, double-blind, placebo controlled (RDBPC) studies the results of which were predominantly negative that contributed to the abandonment of this treatment. Also reviewed were more recent articles from Europe and China, which report both clinical and immunologic support for the use of the orally and sublingually administered mixed respiratory bacterial lysates (MRBL or BL). Results: A review of five RDBPC studies of the parenteral use of BVs for prevention of asthma exacerbations conducted by leading international allergists in the 1950s and 1960s showed, in a combined 532 patients, an overall reduction of asthma attacks by 4.9% over placebo. However, in five studies in 1126 patients of oral or sublingual treatment with BLs, the reduction in respiratory infections, wheezing episodes, and asthma exacerbations was 42.6% over placebo. Conclusion: Reported results with oral and sublingual BLs are far superior to the historical performance of injected BVs. Possible reasons for this difference are discussed, but none is clearly responsible for the difference in clinical results.

Promising Immunomodulatory Effects of Bacterial Lysates in Allergic Diseases

In light of an escalating prevalence of allergic disorders, it is crucial to fully comprehend their pathophysiology and etiology. Such knowledge would play a pivotal role in the search for new therapeutic approaches concerning not only diseases’ symptoms, but also their underlying causes. The hygiene hypothesis indicates a high correlation between limited exposure to pathogens in early childhood and the risk of developing allergic disorders. Bearing in mind the significance of respiratory and digestive systems’ mucous membrane’s first-line exposure to pathogens as well as its implications on the host’s immune response, a therapy targeted at aforesaid membranes could guarantee promising and extensive treatment outcomes. Recent years yielded valuable information about bacterial lysates (BLs) known for having immunomodulatory properties. They consist of antigen mixtures obtained through lysis of bacteria which are the most common etiologic agents of respiratory tract infections. They interact with dendritic cells located in the mucous membranes of the upper respiratory tract and the gastrointestinal tract by toll-like receptors. The dendritic cells present acquired antigens resulting in innate immune response development on the release of chemokines, both stimulating monocytes and NK cells maturation and promoting polymorphonuclear neutrophil migration. Moreover, they influence the adaptive immune system by stimulating an increase of specific antibodies against administered bacterial antigens. The significance of BLs includes not only an anti-inflammatory effect on local infections but also restoration of Th1/Th2 balance, as demonstrated mainly in animal models. They decrease Th2-related cytokine levels (IL-4, IL-13) and increase Th1-related cytokine levels (IFN-γ). The reestablishment of the balance of the immune response leads to lowering atopic reactions incidence which, in addition to reduced risk of inflammation, provides the alleviation and improvement of clinical manifestations of allergic disorders. In this review, we hereby describe mechanisms of BLs action, considering their significant immunomodulatory role in innate immunity. The correlation between local, innate, and adaptive immune responses and their impact on the clinical course of allergic disorders are discussed as well. To conclude our review, we present up-to-date literature regarding the outcomes of BLs implemented in atopic dermatitis, allergic rhinitis, and asthma prevention and treatment, especially in children.