D.I. Ivanovsky ― A Pioneer Discover of Viruses, As A New Form of Biological Life

125 years ago, in 1992, a Russian scientist Dmitri Iosifovich Ivanovsky published first research data disclosing a unique form of filterable biological microlife. Further scientific progress in this discovery resulted in a new discipline of human knowledge, called «the Kingdom of viruses».A fundamental understanding of viral form of biological life was established not at once and was gradually formed under the accumulation of scientific facts. Only at the beginning of 50 years of the twentieth century, a basic understanding of viral Kingdom had been formed and 1992 year was recognized as the year of the birth of Virology. Virology, which started developing by the research of D.I. Ivanovsky, gave remarkable progress and prominent results: more than 20 scientists got Nobble Prize for the outstanding works in virology. There are all arguments and grounds to nominate the international scientific award in virology named of D.I. Ivanovsky.

Fisher Scientific Award Lecture — The capsular polysaccharides of Group BStreptococcusandStreptococcus suisdifferently modulate bacterial interactions with dendritic cells1This article is based on an Award Lecture by Dr. Mariela Segura at the 61st Annual Meeting of the Canadian Society of Microbiologists in St. John’s, Newfoundland, on 23 June 2011. Dr. Segura was the recipient of the 2011 Fisher Scientific Award, a national award sponsored by Fisher Scientific to recognize excellence in microbiology research.

Infections with encapsulated bacteria cause serious clinical problems. Besides being poorly immunogenic, the bacterial capsular polysaccharide (CPS) cloaks antigenic proteins, allowing bacterial evasion of the host immune system. Despite the clinical significance of bacterial CPS and its suggested role in the pathogenesis of the infection, the mechanisms underlying innate and, critically, adaptive immune responses to encapsulated bacteria have not been fully elucidated. As such, we became interested in studying the CPS of two similar, but unique, streptococcal species: Group B Streptococcus (GBS) and Streptococcus suis . Both streptococci are well encapsulated, some capsular types are more virulent than others, and they can cause severe meningitis and septicemia. For both pathogens, the CPS is considered the major virulence factor. Finally, these two streptococci are the sole Gram-positive bacteria possessing sialic acid in their capsules. GBS type III is a leading cause of neonatal invasive infections. Streptococcus suis type 2 is an important swine and emerging zoonotic pathogen in humans. We recently characterized the S. suis type 2 CPS. It shares common structural elements with GBS, but sialic acid is α2,6-linked to galactose rather than α2,3-linked. Differential sialic acid expression by pathogens might result in modulation of immune cell activation and, consequently, may affect the immuno-pathogenesis of these bacterial infections. Here, we review and compare the interactions of these two sialylated encapsulated bacteria with dendritic cells, known as the most potent antigen-presenting cells linking innate and adaptive immunity. We further address differences between dendritic cells and professional phagocytes, such as macrophages and neutrophils, in their interplay with these encapsulated pathogens. Elucidation of the molecular and cellular basis of the impact of CPS composition on bacterial interactions with immune cells is critical for mechanistic understanding of anti-CPS responses. Knowledge generated will help to advance the development of novel, more effective anti-CPS vaccines and improved immunotherapies.