Anti-infective vaccination in the 21st century—new horizons for personal and public health

Molecular Mechanisms Influencing Bacterial Conjugation in the Intestinal Microbiota

Bacterial conjugation is a widespread and particularly efficient strategy to horizontally disseminate genes in microbial populations. With a rich and dense population of microorganisms, the intestinal microbiota is often considered a fertile environment for conjugative transfer and a major reservoir of antibiotic resistance genes. In this mini-review, we summarize recent findings suggesting that few conjugative plasmid families present in Enterobacteriaceae transfer at high rates in the gut microbiota. We discuss the importance of mating pair stabilization as well as additional factors influencing DNA transfer efficiency and conjugative host range in this environment. Finally, we examine the potential repurposing of bacterial conjugation for microbiome editing.

Streptococcus pneumoniae as a Cause of Community-Acquired Pneumonia in Indian Adolescents and Adults: A Systematic Review and Meta-Analysis

BACKGROUND

Streptococcus pneumoniae is one of the primary cause of community-acquired pneumonia (CAP) worldwide. However, scant data are available on the prevalence of etiological organisms for CAP in adolescent and adult Indian population.

OBJECTIVE

We performed a systematic review and meta-analysis to determine the contribution of S. pneumoniae in the causation of CAP in Indian patients aged 12 years or above.

METHODOLOGY

We performed a systematic search of both indexed and non-indexed publications using PubMed, databases of National Institute of Science Communication and Information Resources (NISCAIR), Annotated Bibliography of Indian Medicine (ABIM), Google Scholar, and hand search including cross-references using key terms 'community acquired pneumonia AND India'. All studies, published between January 1990 and January 2017, that evaluated Indian patients aged above 12 years with a confirmed diagnosis of CAP were eligible for inclusion. Our search retrieved a total of 182 studies, of which only 17 and 12 qualified for inclusion in the systematic review of all etiological organisms, and meta-analysis of S. pneumonia, respectively.

RESULTS

A total of 1435 patients met the inclusion criteria. The pooled proportion of patients with S. pneumoniae infection was 19% (95% confidence interval [CI]: 12%-26%; I2 = 94.5% where I2 represents heterogeneity, P < .01). Other major etiological agents are Mycoplasma pneumoniae (15.5% [1.1%-35.5%]), Klebsiella pneumoniae (10.5% [1.6%-24.0%]), and Legionella pneumophila (7.3% [2.5%-23.8%]).

CONCLUSIONS

Analysis found approximately a one-fifth proportion of adult Indian patients of CAP with S. pneumoniae infection, suggesting it as a leading organism for causing CAP compared with other etiological organisms.

Revisiting Bacterial Ubiquitin Ligase Effectors: Weapons for Host Exploitation

Protein ubiquitylation plays a central role in eukaryotic cell physiology. It is involved in several regulatory processes, ranging from protein folding or degradation, subcellular localization of proteins, vesicular trafficking and endocytosis to DNA repair, cell cycle, innate immunity, autophagy, and apoptosis. As such, it is reasonable that pathogens have developed a way to exploit such a crucial system to enhance their virulence against the host. Hence, bacteria have evolved a wide range of effectors capable of mimicking the main players of the eukaryotic ubiquitin system, in particular ubiquitin ligases, by interfering with host physiology. Here, we give an overview of this topic and, in particular, we detail and discuss the mechanisms developed by pathogenic bacteria to hijack the host ubiquitination system for their own benefit.

Intranasal administration of cationic liposomes enhanced granulocyte-macrophage colony-stimulating factor expression and this expression is dispensable for mucosal adjuvant activity

Objective

Infectious diseases remain a threat to human life. Vaccination against pathogenic microbes is a primary method of treatment as well as prevention of infectious diseases. Particularly mucosal vaccination is a promising approach to fight against most infectious diseases, because mucosal surfaces are a major point of entry for most pathogens. We recently developed an effective mucosal adjuvant of cationic liposomes composed of 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) and 3β-[N-(N′,N′-dimethylaminoethane)-carbamoyl] (DC-chol) (DOTAP/DC-chol liposomes). However, the mechanism(s) underlying the mucosal adjuvant effects exerted by the cationic liposomes have been unclear. In this study, we investigated the role of granulocyte–macrophage colony-stimulating factor (GM-CSF), which was reported to act as a mucosal adjuvant, on the mucosal adjuvant activities of DOTAP/DC-chol liposomes when administered intranasally to mice.

Results

Here, we show that, although intranasal vaccination with cationic liposomes in combination with antigenic protein elicited GM-CSF expression at the site of administration, blocking GM-CSF function by using an anti-GM-CSF neutralizing antibody did not alter antigen-specific antibody production induced by DOTAP/DC-chol liposomes, indicating that GM-CSF may not contribute to the mucosal adjuvant activity of the cationic liposomes when administered intranasally.

Electronic supplementary material

The online version of this article (10.1186/s13104-018-3591-3) contains supplementary material, which is available to authorized users.

Natural and Artificial Strategies To Control the Conjugative Transmission of Plasmids

Conjugative plasmids are the main carriers of transmissible antibiotic resistance (AbR) genes. For that reason, strategies to control plasmid transmission have been proposed as potential solutions to prevent AbR dissemination. Natural mechanisms that bacteria employ as defense barriers against invading genomes, such as restriction-modification or CRISPR-Cas systems, could be exploited to control conjugation. Besides, conjugative plasmids themselves display mechanisms to minimize their associated burden or to compete with related or unrelated plasmids. Thus, FinOP systems, composed of FinO repressor protein and FinP antisense RNA, aid plasmids to regulate their own transfer; exclusion systems avoid conjugative transfer of related plasmids to the same recipient bacteria; and fertility inhibition systems block transmission of unrelated plasmids from the same donor cell. Artificial strategies have also been designed to control bacterial conjugation. For instance, intrabodies against R388 relaxase expressed in recipient cells inhibit plasmid R388 conjugative transfer; pIII protein of bacteriophage M13 inhibits plasmid F transmission by obstructing conjugative pili; and unsaturated fatty acids prevent transfer of clinically relevant plasmids in different hosts, promoting plasmid extinction in bacterial populations. Overall, a number of exogenous and endogenous factors have an effect on the sophisticated process of bacterial conjugation. This review puts them together in an effort to offer a wide picture and inform research to control plasmid transmission, focusing on Gram-negative bacteria.

Targeting Type IV Secretion System Proteins to Combat Multidrug-Resistant Gram-positive Pathogens

For many gram-positive pathogens, conjugative plasmid transfer is an important means of spreading antibiotic resistance . Therefore, the search for alternative treatments to fight and prevent infections caused by these bacteria has become of major interest. In the present study, we evaluated the protein TraM, from the conjugative plasmid pIP501, as a potential vaccine candidate. Anti-TraM antiserum mediated in vitro opsonophagocytic killing of the strain harboring the pIP501 plasmid and also proved to be cross-reactive against other clinically relevant enterococcal and staphylococcal strains. Specificity of antibodies toward TraM was confirmed by results of an opsonophagocytic inhibition assay and Western blot. In addition, conjugative transfer experiments proved that TraM is essential for the transfer of pIP501. Finally, immunization with either TraM or anti-TraM antiserum reduced significantly the colony counts in mice livers, demonstrating that TraM is a promising vaccine candidate against enterococci and other gram-positive pathogens.

Introduction to RNA Vaccines

RNA vaccines are attractive, because they exhibit characteristics of subunit vaccines and live-attenuated vectors, including flexible production and induction of both humoral and cellular immunity. While human proof-of-concept for RNA vaccines is still pending, the nascent field of RNA therapeutics has already attracted substantial industry and government funding as well as record investments of private venture capital. Most recently, the WHO acknowledged messenger RNA (mRNA) as a new therapeutic class. In this chapter, we briefly review key developments in RNA vaccines and outline the contents of this volume of Methods in Molecular Biology.

Strategies to develop vaccines of pediatric interest

INTRODUCTION

The success of the vaccines available on the market has significantly increased interest in vaccine development. Areas covered: The main aim of this paper is to discuss the most important vaccines of pediatric interest that are currently being developed. New pneumococcal vaccines and vaccines against group B Streptococcus, Staphylococcus aureus and respiratory syncytial virus are analyzed in detail. Expert commentary: Advances in understanding human immunology, including human monoclonal antibody identification, sequencing technology, and the ability to solve atomic level structures of vaccine targets have provided tools to guide the rational design of future vaccines. It is likely that some of these vaccines will reach the market in the future and will thus partially contribute to the prevention of very severe diseases that significantly affect the morbidity and mortality of children. However, further studies in animals and several clinical trials in children must be performed before new vaccines become licensed.