The HIV Nef protein mediates endocytosis of surface receptors that correlates with disease progression, but the link between this Nef function and HIV pathogenesis is not clear. Here, we report that Nef-mediated activation of membrane trafficking is bidirectional, connecting endocytosis with exocytosis as occurs in activated T cells. Nef expression induced an extensive secretory activity in infected and, surprisingly, also in noninfected T cells, leading to the massive release of microvesicle clusters, a phenotype observed in vitro and in 36%-87% of primary CD4 T cells from HIV-infected individuals. Consistent with exocytosis in noninfected cells, Nef is transferred to bystander cells upon cell-to-cell contact and subsequently induces secretion in an Erk1/2-dependent manner. Thus, HIV Nef alters membrane dynamics, mimicking those of activated T cells and causing a transfer of infected cell signaling (TOS) to bystander cells. This mechanism may help explain the detrimental effect on bystander cells seen in HIV infection.

Pseudomonas aeruginosa and Burkholderia cenocepacia are predominant opportunistic pathogens in cystic fibrosis (CF) patients. In healthy humans the lower respiratory tract as well as all mucosa, contains a very low free iron concentration (10-18 M), while in CF patients' sputum iron concentration is very high, showing a median value of 63x10-6 M. Accumulation of catalytic reactive iron heavily contributes to subsequent clinical complications in the lung disorders by the production of reactive oxygen species and increases bacterial growth and virulence. The data reported in this study indicate that low iron concentration (Fe 3 + 1 JA.M) induced free-living forms and motility both in P. aeruginosa and B. cenocepacia, while high iron concentrations (Fe 3 + 10 and 100 tJ.M) stimulated aggregation and biofilm formation already in the fluid phases, so demonstrating that aggregation and biofllm formation are positively iron-modulated in these bacteria. Moreover, the different morphological forms (free-living, aggregates and biofllm) showed different capabilities of adhering and invading the bronchial cell line A549. P. aeruginosa PA01 aggregates, and mostly biofllm, exerted the highest adhesion efficiency, while B. cenocepacia PV1 aggregates or biofilm the lowest. A significant reduction in invasion efficiency by P. aeruginosa biofilm and a significant increase in cell internalization by B. cenocepacia biofllm has been reported. Therefore, the iron availability is an important signal to which P. aeruginosa and B. cenocepacia counteract by leaving the motile free-living forms and entering into a new lifestyle, i.e, biofllm. These data could contribute to explain that the ironoverload of the sputum of CF patients, inducing nonmotile forms, aggregates and biofllm, may facilitate penetration of host epithelial barriers contributing to the establishment of infection, colonization, persistence and systemic spread of these opportunistic pathogens.Pseudomonas aeruginosa is a ubiquitous Gramnegative motile bacterium found in different environments such as soil, freshwater and marine habitat. Moreover, P. aeruginosa is the predominant opportunistic pathogen in cystic fibrosis (CF) patients, as the lungs of >90% of all CF patients are colonized by this bacterium (1). Chronic colonization of P. aeruginosa in CF patient airways is a major source of morbidity and mortality (2) leading to epithelial surface damage and airway plugging which results in a decrease of pulmonary function (3).Although not as prevalent as P. aeruginosa, Burkholderia cepacia is another important opportunistic respiratory pathogen in CF patients (2),

Different milk proteins were analyzed for their inhibitory effect on either rotavirus-mediated agglutination of human erythrocytes or rotavirus infection of the human enterocyte-like cell line HT-29. Proteins investigated were alpha-lactalbumin, beta-lactoglobulin, apo-lactoferrin, and Fe(3+)-lactoferrin, and their antiviral action was compared with the activity of mucin, a milk glycoprotein known to affect rotavirus infection. Results obtained demonstrated that beta-lactoglobulin, apo- and Fe(3+)-lactoferrin are able to inhibit the replication of rotavirus in a dose-dependent manner, apo-lactoferrin being the most active. It was shown that apo-lactoferrin hinders virus attachment to cell receptors since it is able to bind the viral particles and to prevent both rotavirus haemagglutination and viral binding to susceptible cells. Moreover, this protein markedly inhibited rotavirus antigen synthesis and yield in HT-29 cells when added during the viral adsorption step or when it was present in the first hours of infection, suggesting that this protein interferes with the early phases of rotavirus infection.

SummaryGametogenesis is the earliest event after uptake of malaria parasites by the mosquito vector, with a decisive impact on colonization of the mosquito midgut. This process is triggered by a drop in temperature and contact with mosquito molecules. In a few minutes, male and female gametocytes escape from the host erythrocyte by rupturing the parasitophorous vacuole and the erythrocyte membranes. Electron-dense, oval-shaped organelles, the osmiophilic bodies (OB), have been implicated in the egress of female gametocytes. By comparative electron microscopy and electron tomography analyses combined with immunolocalization experiments, we here define the morphological features distinctive of male secretory organelles, hereafter named MOB (male osmiophilic bodies). These organelles appear as club-shaped, electron-dense vesicles, smaller than female OB. We found that a drop in temperature triggers MOB clustering, independently of exposure to other stimuli. MDV1/PEG3, a protein associated with OB in Plasmodium berghei females, localizes to both non-clustered and clustered MOB, suggesting that clustering precedes vesicle discharge. A P. berghei mutant lacking the OB-resident female-specific protein Pbg377 displays a dramatic reduction in size of the OB, accompanied by a delay in female gamete egress efficiency, while female gamete fertility is not affected. Immunolocalization experiments indicated that MDV1/PEG3 is still recruited to OB-remnant structures.

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