Amino acid changes in the attachment G glycoprotein of human respiratory syncytial viruses (subgroup A) isolated in Italy over several epidemics (1997-2006).

The human respiratory syncytial virus (HRSV) is the most important cause of admission to hospital for acute lower respiratory tract infections in infants and young children worldwide. Only few studies have investigated the molecular evolution of HRSV, and none has been conduct ed in Italy. The genetic diversity of the G glycoprotein of 59 subgroup A strains obtained from two clinical centers located in Northern and Central Italy was studied, during seven nonconsecutive epidemic seasons (1997-2006). The nucleotide sequences encompassing 624 bp, at the carboxy terminus of the G glycoprotein gene, were compared to sequences representative of previously defined HRSV genotypes. Phylogenetic analysis indicated that most Italian group A isolates clustered into two different lineages (GA2 and GA5), whereas only few isolates grouped into the other known lineages. Eight positively selected sites were found and it was predicted that serine and threonine of positively selected sites 117 and 262 (respectively) are O-glycosilated. The presence of multiple identical sequences in three lineages (GA1, GA5, and BE/A1) suggests that certain strains are predominant in a given epidemic season. Although most of the sites of the G glycoprotein gene of HRSV-A strains seem invariable because of strong purifying selection, some evolutionary "hot spots" may be present. Since the G glycoprotein is a major target (together with the F glycoprotein) of the HRSV humoral immune response, it is important to provide information about its genetic heterogeneity in order to address better both therapeutic and vaccine strategy.

Respiratory viruses and influenza-like illness: a survey in the area of Rome, winter 2004-2005.

Limited information is available on the viral aetiology of influenza-like illness (ILI) in Southern European countries. Hereby we report the main findings of a survey conducted in the area of Rome during the 2004-2005 winter season.ILI cases were defined as individuals with fever >37.5 degrees C and at least one constitutional symptom and one respiratory symptom, recruited during the survey period. Influenza and other respiratory viruses were identified using polymerase chain reaction (PCR) on throat swabs. Basic individual information was collected through a standard form. Of 173 ILI cases enrolled, 74 tested positive for one virus, and two tested positive for two viruses. Overall, 33.5% of the cases were positive for influenza viruses, 5.2% for adenoviruses, 3.5% for parainfluenza viruses, 1.7% for coronaviruses, and 1.2% for the respiratory syncitial virus. The proportion of influenza virus detection was higher in the 'high influenza activity' period. The distribution of viral agents varied across age groups, influenza viruses being more likely to be detected in younger patients. Viral pathogens were identified in less than 50% of ILI cases occurred during a high activity influenza season. The detection of other than influenza viruses was sporadic, without evidence of large outbreaks due to specific agents.

An influenza A/H3 outbreak during the 2004/2005 winter in elderly vaccinated people living in a nursing home.

This study examined the antibody response against the three vaccine antigens and the epidemic A/H3N2 drift variant (A/California) and the prevention of laboratory diagnosed influenza infections in a group of elderly institutionalized people vaccinated with the 2004/2005 influenza vaccine. Antibody titres were measured by hemagglutination inhibition (HI) in sera collected before and 1 month after vaccination. Laboratory diagnosis was done examining throat swabs (RT-PCR or MDCK cell culture) or by serology (seroconversion comparing HI titres in sera collected 1 and 5 months after vaccination). Results obtained showed that influenza vaccination induced an adequate immune response against the three vaccine antigens and the epidemic A/H3N2 variant, however it was not capable of preventing an influenza outbreak due to the new A/H3N2 (A/California) variant.

Respiratory viruses and influenza-like illness: a survey in the area of Rome, winter 2004-2005.

Limited information is available on the viral aetiology of influenza-like illness (ILI) in Southern European countries. Hereby we report the main findings of a survey conducted in the area of Rome during the 2004-2005 winter season. ILI cases were defined as individuals with fever >37.5°C and at least one constitutional symptom and one respiratory symptom, recruited during the survey period. Influenza and other respiratory viruses were identified using polymerase chain reaction (PCR) on throat swabs. Basic individual information was collected through a standard form. Of 173 ILI cases enrolled, 74 tested positive for one virus, and two tested positive for two viruses. Overall, 33.5% of the cases were positive for influenza viruses, 5.2% for adenoviruses, 3.5% for parainfluenza viruses, 1.7% for coronaviruses, and 1.2% for the respiratory syncitial virus. The proportion of influenza virus detection was higher in the 'high influenza activity' period. The distribution of viral agents varied across age groups, influenza viruses being more likely to be detected in younger patients. Viral pathogens were identified in less than 50% of ILI cases occurred during a high activity influenza season. The detection of other than influenza viruses was sporadic, without evidence of large outbreaks due to specific agents.

The cysteine residues of the M2 protein are not required for influenza A virus replication.

The M2 protein of influenza A virus functions as an ion channel. It contains three cysteine residues: cysteines 17 and 19, which form disulfide bonds in the ectodomain, and cysteine 50 which is acylated. To understand the role of these cysteine residues in virus replication, we used reverse genetics to create influenza viruses in which the individual cysteines were mutated and a virus in which all three cysteines were changed to serine. The M2 cysteine mutants that lacked either of the cysteine residues in the ectodomain and the mutant that lacked all three residues had appreciably lower amounts of M2 oligomers than did the wild-type virus when examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. None of the mutants, however, were defective in replication, either in vitro or in ferrets and mice. These findings demonstrate that noncovalent interactions are sufficient for the M2 protein to form functional oligomers for virus replication and that its cysteine residues are dispensable for influenza virus replication in vitro and in vivo.

Concurrent antigenic analysis of recent epidemic influenza A and B viruses and quantitation of antibodies in population serosurveys in Italy.

Laboratory investigations of virus isolation and serum antibodies in a Mediterranean country (Italy) demonstrated that influenza A and B viruses, and often both, circulated every winter in Italy. The winter 1987/88 was characterized by a low level of influenza activity, as shown by the limited number (47) of influenza virus isolates, the majority of which (61%) belonged to the influenza B type. In contrast, the 1988/89 influenza season was exclusively associated with the circulation of influenza type A viruses. The A(H1H1) subtype was largely predominant (97%), as compared to the low incidence of the A(H3N2) subtype (3%). During the 1989/90 winter a co-circulation of A and B influenza viruses was observed, A(H3N2) strains being responsible for 96% of the virologically confirmed cases. Antigenic analysis of the virus isolates showed some antigenic variation in influenza A viruses of both H1N1 and H3N2 subtypes, whilst antigenic stability was found among the influenza B virus isolates. Overall, the above virological findings correlate with the data concerning the pattern of influenza virus circulation in Northern Europe and the UK during the three years surveyed. The results of serum antibody surveys conducted in each post-epidemic period are also reported.