Impact of recently discovered viruses on epidemiology of acute respiratory tract infections (ARTI) is still unclear. We studied the impact of recently discovered human metapneumovirus (hMPV), human bocavirus (HBoV), and new coronaviruses (HCoV-NL63 and HKU1) on the global epidemiology of ARTI. From October 2006 to April 2007, 237 pediatric patients affected by ARTI were enrolled in our study. Specimens were tested for respiratory viruses by polymerase chain reaction. One hundred twenty-four out of 237 samples (52.3%) were positive for one or more viruses. Picornaviruses were the most prevalent viruses (n = 61, 43.6%), followed by respiratory syncytial virus (n = 34, 24.3%) and Adenovirus (n = 25, 17.9%); hMPV (n = 9, 6.4%) was the fourth most common virus detected. HBoV and HCoV showed a low prevalence (respectively 2.9% and 2.1%). RSV was the prevalent agent of LRTI (38%). Viruses were identified in more than 50% of the studied ARTI, providing useful information on clinical features and epidemiology of specific agents affecting children in cold months. Although routine surveillance of respiratory viruses does not seem cost-effective, continuous monitoring of ARTI etiology could be a useful tool for planning resources for the development of new vaccines and antiviral agents.

Toscana virus (TOSV) is a phlebotomus-transmitted virus that belongs to the family Bunyaviridae and causes widespread infections in humans; about 30 % of these cases result in aseptic meninigitis. In the present study, it was shown that TOSV is an inducer of beta interferon (IFN-b), although its non-structural protein (NSs) could inhibit the induction of IFN-b if expressed in a heterologous context. A recombinant Rift Valley fever virus expressing the TOSV NSs could suppress IFN-b expression in infected cells. Moreover, in cells expressing NSs protein from a cDNA plasmid, IFN-b transcripts were not inducible by poly(I : C). Unlike other members of the family Bunyaviridae, TOSV appears to express an NSs protein that is a weak antagonist of IFN induction. Characterization of the interaction of TOSV with the IFN system will help our understanding of virus-host cell interactions and may explain why the pathogenesis of this disease is mostly mild in humans.

Respiratory syncytial virus (RSV) is the major pathogen causing respiratory disease in young infants and it is an important cause of serious illness in the elderly since the infection provides limited immune protection against reinfection. In order to explain this phenomenon, we investigated whether healthy adults of different age (20-40; 41-60 and > 60 years), have differences in central and effector memory, RSV-specific CD8+ T cell memory immune response and regulatory T cell expression status. In the peripheral blood of these donors, we were unable to detect any age related difference in term of central (CD45RA-CCR7+) and effector (CD45RA-CCR7-) memory T cell frequency. On the contrary, we found a significant increase in immunosuppressive regulatory (CD4+25+FoxP3+) T cells (Treg) in the elderly. An immunocytofluorimetric RSV pentamer analysis performed on these donors' peripheral blood mononuclear cells (PBMCs), in vitro sensitized against RSV antigen, revealed a marked decline in long-lasting RSV specific CD8+ memory T cell precursors expressing interleukin 7 receptor α (IL-7Rα), in the elderly. This effect was paralleled by a progressive switch from a Th1 (IFN-γ and TNF-α) to a Th2 (IL-10) functional phenotype. On the contrary, an increase in Treg was observed with aging. The finding of Treg over-expression status, a prominent Th2 response and an inefficient RSV-specific effector memory CD8+ T cell expansion in older donors could explain the poor protection against RSV reinfection and the increased risk to develop an RSV-related severe illness in this population. Our finding also lays the basis for new therapeutic perspectives that could limit or prevent severe RSV infection in elderly.

Respiratory syncytial virus (RSV) has been demonstrated to cause substantial disease in elderly and immunocompromised subjects. The relationship of serum antibody to RSV infection and the risk of infection in elderly subjects is controversial, thus we evaluated the presence of neutralizing antibodies to RSV in healthy people of different age groups and the correlation with viral protection. Baseline blood samples from 197 subjects aged 20-80 years were analysed for the presence of anti-RSV antibodies either by indirect immunofluorescence and microneutralization test. The percentage of people who had neutralizing antibodies to RSV was significantly higher (P=0.001) in the youngest group (92.51%) compared to the frail group (36.21%). The RSV antibody level tends to wane in some older people; this factor could determine proneness to RSV re-infections in the elderly who are at a greater risk of developing severe respiratory disease.

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