New approaches to control plant parasitic nematodes

Plant parasitic nematodes are a serious threat for crop production worldwide. This review summarizes our understanding of plant nematode interactions and presents new alternatives for nematode control in the field. Breeding for resistance has been a major goal for many important crop species like soybean, potato, tomato and sugar-beet. As a result numerous nematode-resistance genes have been identified, two of which have been cloned recently, Hs1 ^pro-1 from sugar-beet, giving resistance to the beet cyst nematode Heterodera schachtii, and Mi from tomato, giving resistance to the root-knot nematode Meloidogyne incognita. Also artificial resistance genes, coding for nematotoxic proteins or causing rapid death of feeding cells, have been elucidated. In the future, genetic engineering of nematode resistance will become more and more important for plant breeding. Transformation techniques will allow genes to be quickly introduced into susceptible breeding lines and then combined with each other to produce plant varieties with durable resistance. Received: 26 August 1998 / Received revision: 16 December 1998 / Accepted: 21 December 1998     

New technologies for vaccine development

Despite important success of preventive vaccination in eradication of smallpox and in reduction in incidence of poliomyelitis and measles, infectious diseases remain the principal cause of mortality in the world. Technologies used in the development of vaccines used so far, mostly based on empirical approaches, are limited and insufficient to fight diseases like malaria, acquired immunodeficiency syndrome (AIDS) or adult tuberculosis. Until recently, technologies for making vaccines were based on live attenuated microorganisms, whole killed microorganisms and subunit vaccines such as purified toxoids. Fortunately, the recent advances in the understanding of host-pathogen interaction as well as our increasing knowledge of how immune responses are triggered and regulated have opened almost unlimited possibilities of developing new immunization strategies based on recombinant microorganisms or recombinant polypeptides or bacterial or viral vectors, synthetic peptides, natural or synthetic polysaccharides or plasmid DNA. Thus, considering the expending number of technologies available for making vaccines, it becomes possible for the first time in the history of vaccinology to design vaccines based on a rational approach and leading to increased efficacy and safety.     

New approaches for Helicobacter vaccine development--difficulties and progress.

Despite the enormous progress in understanding the process of bacterial pathogenesis and interactions of pathogens with eucaryotic cells the infectious diseases still remain the main cause of human premature deaths. It is now recognized that Helicobacter pylori infects about half of the world's population. Based on results of clinical studies the World Health Organization has assigned H. pylori as a class I carcinogen. The review presents new achievements aimed at construction efficient and safe anti-Helicobacter vaccine. We discuss the new global technologies such as immunoproteomics employed for selecting new candidates for vaccine construction as well as new vaccine delivery systems. The review presents also our knowledge concerning H. pylori interaction with immune system which might facilitate modulation of the host immune system by specific adjuvant included into vaccine.     

New approaches in the treatment of bacterial infections

Recently, several new drugs for the treatment of bacterial infections have been developed. Quinupristin/dalfopristin, moxifloxacin and gatifloxacin have been approved throughout the world for clinical use. Levofloxacin has been approved for the treatment of community-acquired pneumonia caused by penicillin-resistant Streptococcus pnuemoniae. The Food and Drug Administration has approved linezolid for clinical use, and new drug applications for gemifloxacin and telithromycin were filed. Other new targets have surfaced in the quest for novel antibacterial agents.     

Pneumococcal surface protein A and new approaches for pneumococcal vaccine development

The problem of pneumococcal infections is pressing for the whole world. Existing vaccines based only on pneumococci polysaccharide antigens or polysaccharide antigens and diphtherial anatoxin are not capable of protecting from all serotypes of the microorganism. Reasonability of creation of pneumococcal vaccine based on surface proteins of Streptococcus pneumoniae is discussed in the literature. One of such key pneumococcal proteins is pneumococcal surface protein A (PSPA), because it is detected in all the S. pneumoniae strains, has cross activity and switches B-cell immune response to T-cell. Currently the development of conjugated vaccine based on surface proteins and capsule polysaccharides of pneumococcus seems promising.     

New knowledge on pathogenesis of bacterial enteric infections as applied to vaccine development.

This review attempts to synthesize the new knowledge of pathogenesis of bacterial enteric infections and relate this information to vaccine development. Discussion focuses on human infections and to those in which significant strides have been made. As a general theme in the pathogenesis of bacterial enteric infections, pathogens can be characterized into 5 groups on the basis of their degree of ultimate invasiveness after ingestion by a susceptible hose: mucosal adherence and enterotoxin production; mucosal adherence and brush border dissolution -- enteropathogenic E. coli (EPEC) of "classical" serotypes; mucosal invasion and intraepithelial cell proliferation; mucosal translocation followed by bacterial proliferation in the lamina propria and mesenteric lymph nodes; and mucosal translocation followed by generalized infection. The review covers cholera (motility and chemotaxis, mucosal adhesion, flagellar sheath protein, hemagglutinins, outer membrane proteins, enterotoxin production, quality and duration of infection derived immunity, immune response in humans, LPS, flagellar sheath protein, cholera lectin, other cholera hemagglutinins, outer membrane protein, previous cholera vaccines, killer whole cell vaccines, toxoids, combination vaccines, attenuated versus cholerae vaccines): enterotoxigenic Escherichia coli (ETEC) (entertoxins, O:H serotypes and enterotoxin phenotypes, colonization factors, immune response in humans, vaccines against ETEC, and toxiods); EPEC (vaccines against EPEC); Shigella (smooth LPS O antigen, epithelial cell invasiveness, Shigella toxin, and Shigella vaccines); and typhoid fever (caccines against typhoid fever). The major attraction of a nonliving oral cholera vaccine is its safety. A review of available information leads to the conclusion that an oral vaccine consisting of a combination of antigens, intending to stimulate both antibacterial and antitoxic immunity, would be most likely to succeed. Current approaches to immunoprophylaxis of ETEC infection involve vaccines that stimulate antitoxic or antiadhesion immunity or both by means of killed antigens or attenuated strains. It is likely that the most effective vaccines will contain appropriate antigens intended to simultaneously stimulate both antibacterial and antitoxic immunity, thereby leading to a synergistic protective effect. Now that the speical enteroadhesive properties of EPEC have been characterized and shown to be associated with a plasmid, it should be possible to identify the phenotypic gene products responsible for this phenomenon. It is likely that fimbriae or outer membrane proteins will prove to be the organelle of adhesion. When such information becomes available, it should be possible to prepare oral vaccines consisting of the purified antigen. Efficacy has been shown for attenuated Shigella strains utilized as oral vaccines. The major thrust in the development of new immunization agensts against typhoid fever is to identify immunizing agents at least equal in efficacy to the parenteral acetone killed vaccine but which cause no adverse reactions.     

SCID mice as models for parasitic infections

Mice with severe combined immunodeficiency (SCID mice) have become a favored model system for the study of many parasitic diseases. In this review, Samuel Stanley Jr and Herbert Virgin IV provide a brief overview of the biology of the SCID mouse, and review some examples of how the SCID mouse model has been applied to the study of the immunology of a number of different parasitic diseases.