Strategies to define a regulatory network distance function.

Complex biological systems are suitably represented as interaction networks. Such networks have been studied either by their general topology, modular composition or enrichment in particular network motifs. In our work, we propose additional procedures to examine biological networks by evaluating the composition of the neighbourhood of each node spanning variable scales. The definition of neighbourhoods requires the ability to quantify distances between nodes in the network. In this presentation I will discuss the strategies that we have followed in the attempt to define a network distance function.

"Modeling Pertussis epidemiology - New perspectives."

Whooping cough (Pertussis) is a highly infectious bacterial disease caused by Bordetella pertussis. This is a small Gram negative rod capable of colonizing the cilia of the respiratory epithelium. Pertussis is 1 of the 10 most common causes of death from infectious disease worldwide. The introduction of child vaccination in the early-mid 20th century decreased the incidence of pertussis so enormously as to make it an uncommon disease, altough it is still endemic, with epidemic periods of 3-5 years. In fact, immunization is yet to reach the 100% effectiveness limit at the time of vaccination and it becomes less effective over the years. Since the 1980s there as been an increase in the occurrence of pertussis cases, as well as a shift of the average age of infection towards the higher age classes. This may be atributed to: 1) the far more effective recognition and diagnosis of the illness among older age groups (sub-clinical); 2) the waning of induced immunity due to the low circulation of the bacteria; 3) the development of new strains of B. pertussis that are not affected by the existing vaccines (allowing them to remain endemic). Over the years mathematical models attempted to reproduce the epidemiology of the disease and to some extent find out which of the hypothesis (or which combination) is more plausible, if any of these. This study, based on recent and more frequent genetic studies of the B. pertussis populations, considers immunity to pertussis to be a mixture of temporary and partial immunity. This approach has proven to be substantially different from others in terms of the epidemiological patterns it produces, mainly because of the existence of a reinfection threshold associated to a certain value of a transmission coefficient. Results have shown that it is possible to reproduce the general trend of incidence that is seen in epidemiological data, as well as the increase in clinical infections that has been reported in recent years, without implementing variability in vaccine efficacy. Thus we can propose that the increasing incidence of pertussis is attributable to a decrease in the transmission coefficient in developed countries, based on the assumption that there is a progressive loss of immunity linked to a transmission reduction mechanism