This study shows a high prevalence of viruses in the lower respiratory tract samples of hospitalized adults, mostly HRV and FLU-A. It is not possible to establish the role of viruses detected at low frequency, but our findings suggest the necessity to consider them as potential causes or precursors of lower respiratory tract infections (LRTIs).
Antibody avidity maturation takes place only in the presence of ongoing viral replication. These results may have relevant implications in understanding the complex mechanism of maturation of the immune response to HIV.
Our data suggest that the genital and plasma quasi species represent distinct subpopulations, which possibly reflects compartmentalized viral replication. Alternatively, cell carriers harboring viral quasi species in the genital tract that are distinct from those in plasma could transfer the virus through the barrier separating the 2 body sites.
As observed by others, HCoV-NL63 is often associated with another virus. Phylogenetic characterization of HCoV-NL63 circulating in Italy indicates that this virus circulates as a mixture of variant strains, as observed in other countries.
RT-PCR is the most sensitive assay for diagnosis of influenza, due to enhanced rapidity and sensitivity as compared to classical methods. Hemi-nested RT-PCR was developed, targeting NP gene for influenza A and NS gene for influenza B, based on a previous single round RT-PCR method. The new method was compared with the previous technique for analytical sensitivity and specificity, and was applied to clinical samples from the lower and upper respiratory tract. The analytical sensitivity of hemi-nested RT-PCR was 10 (influenza A) and 4 times (influenza B) higher than the previous method. A high specificity of the new hemi-nested RT-PCR assay was observed by using whole respiratory viruses. When applied to lower respiratory tract specimens, the new method showed an increased rate of positivity as compared to the previous technique (9.3% versus 0.7% for influenza A, and 0.9% versus 0.2% for influenza B). Screening of upper respiratory tract samples collected during the seasonal 2005-2006 outbreak indicated 26.4% and 5.8% positivity for influenza A and B, respectively. The results were confirmed by sequence analysis: apart from influenza B, both influenza A subtypes H3N2 and H1N1, associated with the seasonal outbreak, were detected.
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