Co-circulation of the two influenza B lineages during 13 consecutive influenza surveillance seasons in Italy, 2004-2017.

BACKGROUND: Since 1985, two antigenically distinct lineages of influenza B viruses (Victoria-like and Yamagata-like) have circulated globally. Trivalent seasonal influenza vaccines contain two circulating influenza A strains but a single B strain and thus provide limited immunity against circulating B strains of the lineage not included in the vaccine. In this study, we describe the characteristics of influenza B viruses that caused respiratory illness in the population in Italy over 13 consecutive seasons of virological surveillance, and the match between the predominant influenza B lineage and the vaccine B lineage, in each season. METHODS: From 2004 to 2017, 26,886 laboratory-confirmed influenza cases were registered in Italy, of which 18.7% were type B. Among them, the lineage of 2465 strains (49%) was retrieved or characterized in this study by a real-time RT-PCR assay and/or sequencing of the hemagglutinin (HA) gene. RESULTS: Co-circulation of both B lineages was observed each season, although in different proportions every year. Overall, viruses of B/Victoria and B/Yamagata lineages caused 53.3 and 46.7% of influenza B infections, respectively. A higher proportion of infections with both lineages was detected in children, and there was a declining frequency of B/Victoria detections with age. A mismatch between the vaccine and the predominant influenza B lineage occurred in eight out of thirteen influenza seasons under study. Considering the seasons when B accounted for > 20% of all laboratory-confirmed influenza cases, a mismatch was observed in four out of six seasons. Phylogenetic analysis of the HA1 domain confirmed the co-circulation of both lineages and revealed a mixed circulation of distinct evolutionary viral variants, with different levels of match to the vaccine strains. CONCLUSIONS: This study contributes to the understanding of the circulation of influenza B viruses in Italy. We found a continuous co-circulation of both B lineages in the period 2004-2017, and determined that children were particularly vulnerable to Victoria-lineage influenza B virus infections. An influenza B lineage mismatch with the trivalent vaccine occurred in about two-thirds of cases.

Human-Animal Interface: The Case for Influenza Interspecies Transmission.

Since the 1990s, the threat of influenza viruses to veterinary and human public health has increased. This coincides with the larger global populations of poultry, pigs, and people and with changing ecological factors. These factors include the redistribution of the human population to cities, rapid mass transportation of people and infectious agents, increased global land use, climate change, and possible changes in viral ecology that perpetuate highly pathogenic influenza viruses in the aquatic bird reservoir. The emergence of H5N1, H7N9, and H9N2 subtypes of influenza A virus and the increased genetic exchange among influenza viruses in wild aquatic birds, domestic poultry, swine, and humans pose a continuing threat to humanity. Here we consider the fundamental and practical knowledge of influenza A viruses at the human-animal interfaces to facilitate the development of novel control strategies and modified agricultural practices that will reduce or prevent interspecies transmission.

A heat-inactivated H7N3 vaccine induces cross-reactive cellular immunity in HLA-A2.1 transgenic mice.

BACKGROUND: Cross-reactive immunity against heterologous strains of influenza virus has the potential to provide partial protection in individuals that lack the proper neutralizing antibodies. In particular, the boosting of memory CD8+ T cell responses to conserved viral proteins can attenuate disease severity caused by influenza virus antigenic variants or pandemic strains. However, little is yet known about which of these conserved internal antigens would better induce and/or recall memory CD8+ T cells after in vivo administration of an inactivated whole virus vaccine. METHODS: We explored the CD8 + T cell responses to selected epitopes of the internal proteins of an H7N3 influenza virus that were cross-reactive with A/PR/8/34 virus in HLA-A2.1 transgenic (AAD) mice. RESULTS: CD8+ T cells against dominant and subdominant epitopes were detected upon infection of mice with live H7N3 virus, whereas immunization with non-replicating virus elicited CD8+ T cell responses against mostly immunodominant epitopes, which were rapidly recalled following infection with A/PR/8/34 virus. These vaccine-induced T cell responses were able to reduce the lung viral load in mice challenged intranasally with the heterologous influenza virus. CONCLUSIONS: A single immunization with non-replicating influenza virus vaccines may be able to elicit or recall cross-reactive CD8+ T cell responses to conserved immunodominant epitopes and, to some extent, counteract an infection by heterologous virus.

Human infection with highly pathogenic A(H7N7) avian influenza virus, Italy, 2013.

During an influenza A(H7N7) virus outbreak among poultry in Italy during August-September 2013, infection with a highly pathogenic A(H7N7) avian influenza virus was diagnosed for 3 poultry workers with conjunctivitis. Genetic analyses revealed that the viruses from the humans were closely related to those from chickens on affected farms.

Antibody responses to intradermal or intramuscular MF59-adjuvanted influenza vaccines as evaluated in elderly institutionalized volunteers during a season of partial mismatching between vaccine and circulating A(H3N2) strains.

BACKGROUND: The age-related weakening of the immune system makes elderly subjects less responsive to influenza vaccination. In the last years, two "enhanced vaccines" were licensed for individuals aged ≥65 years, one being a subunit vaccine (Fluad®) containing the MF59 adjuvant administered intramuscularly (IM-MF59) and the other one a split non-adjuvanted vaccine administered intradermally (Intanza® 15mcg) (ID). In the present study, we evaluated and compared the antibody responses against the three vaccine antigens and heterovariant A(H3N2) circulating viruses induced by IM-MF59 and ID influenza vaccines in 80 elderly institutionalized volunteers (40 per group) during the Winter season 2011-2012. RESULTS: Hemagglutination inhibiting (HI) antibody titers were assessed in blood samples collected before, 1 and 6 months after vaccination. One month after vaccination both the IM-MF59 and ID vaccines induced increases in HI titers against all the three vaccine strains. The results in the two groups were similar against the A(H3N2) and A(H1N1) strains. Responses against the B strain typically tended to be higher after ID than IM-MF59, yet both vaccines stimulated lower responses against the B strain than against the two A strains. The two vaccines induced favorable results also against four epidemic drifted A(H3N2) viruses circulating in Winter 2011-2012. Six months after vaccination, the HI titers decreased in both groups. CONCLUSION: The responses induced by IM-MF59 and ID vaccines in institutionalized elderly people were similar against the A(H3N2) and A(H1N1) strains but frequently higher, for the ID, against the B strain. The two vaccines induced positive responses against drifted A(H3N2) circulating viruses.

Report of two cases of influenza virus A/H1N1v and B co-infection during the 2010/2011 epidemics in the Italian Veneto Region.

From October 2010 to April 2011, in the Italian Veneto Region, 1403 hospitalized patients were tested for influenza virus infection by specific real time RT-PCR. Overall, 327 samples were positive for either influenza A (75%) or B (25%) viruses. Among these positive patients two resulted co-infected by A/H1N1v and B viruses. Even though co-infection with both influenza A and B viruses appears to be a rare event, it occurs naturally and may play a role in epidemiology and pathogenicity. In the present study the two co-infected patients were a transplant recipient immunocompromised adult and a child displaying a severe respiratory illness. The co-infection was confirmed by inoculation of the nasopharyngeal swabs in MDCK.2 cells, followed by immunofluorescence and real time RT-PCR assays. Moreover, in the case of the adult patient, the immune system response against both viruses was assayed by hemoagglutination inhibition test against reference influenza virus strains. Both patients fully recovered from infection, without significant differences with mono-infected patients.

Immunogenicity of Viral Vaccines in the Italian Military.

Military personnel of all armed forces receive multiple vaccinations and have been doing so since long ago, but relatively few studies have investigated the possible negative or positive interference of simultaneous vaccinations. As a contribution to fill this gap, we analyzed the response to the live trivalent measles/mumps/rubella (MMR), the inactivated hepatitis A virus (HAV), the inactivated trivalent polio, and the trivalent subunits influenza vaccines in two cohorts of Italian military personnel. The first cohort was represented by 108 students from military schools and the second by 72 soldiers engaged in a nine-month mission abroad. MMR and HAV vaccines had never been administered before, whereas inactivated polio was administered to adults primed at infancy with a live trivalent oral polio vaccine. Accordingly, nearly all subjects had baseline antibodies to polio types 1 and 3, but unexpectedly, anti-measles/-mumps/-rubella antibodies were present in 82%, 82%, and 73.5% of subjects, respectively (43% for all of the antigens). Finally, anti-HAV antibodies were detectable in 14% and anti-influenza (H1/H3/B) in 18% of the study population. At mine months post-vaccination, 92% of subjects had protective antibody levels for all MMR antigens, 96% for HAV, 69% for the three influenza antigens, and 100% for polio types 1 and 3. An inverse relationship between baseline and post-vaccination antibody levels was noticed with all the vaccines. An excellent vaccine immunogenicity, a calculated long antibody persistence, and apparent lack of vaccine interference were observed.

Transmission of hemagglutinin D222G mutant strain of pandemic (H1N1) 2009 virus.

A pandemic (H1N1) 2009 virus strain carrying the D222G mutation was identified in a severely ill man and was transmitted to a household contact. Only mild illness developed in the contact, despite his obesity and diabetes. The isolated virus reacted fully with an antiserum against the pandemic vaccine strain.

Cardiac tamponade and heart failure due to myopericarditis as a presentation of infection with the pandemic H1N1 2009 influenza A virus.

We describe a fatal case of myopericarditis presenting with cardiac tamponade in a previously healthy 11-year-old child. Pandemic H1N1 2009 influenza A virus sequences were identified in throat and myocardial tissues and pericardial fluid, suggesting damage of myocardial cells directly caused by the virus.

Bovine lactoferrin inhibits influenza A virus induced programmed cell death in vitro.

Influenza is one of the main plagues worldwide. The statistical likelihood of a new pandemic outbreak, together with the alarming emergence of influenza virus strains that are resistant to available antiviral medications, highlights the need for new antiviral drugs. Lactoferrin, a 80 kDa bi-globular iron-binding glycoprotein, is a pleiotropic factor with potent antimicrobial and immunomodulatory activities. Although the antiviral effect of lactoferrin is one of its major biological functions, the mechanism of action is still under debate. In this research, we have analyzed the effect of bovine lactoferrin (bLf) on Influenza A virus infection in vitro. Our results showed that (i) Influenza virus infected cells died as a result of apoptosis, (ii) bLf treatment inhibited programmed cell death by interfering with function of caspase 3, a major virus-induced apoptosis effector, and (iii) bLf efficiently blocked nuclear export of viral ribonucleoproteins so preventing viral assembly. These results provide further insights on the antiviral activity of bLf and suggest novel strategies for treatment of Influenza virus infection.

Viral causes of influenza-like illness: Insight from a study during the winters 2004-2007.

Limited information is available on the viral etiology of influenza-like illness in southern European countries, and it is still a matter of debate whether certain symptoms can be used to distinguish among the specific viruses that cause influenza-like illness. The main objective of the present study was to identify the demographic and clinical predictors of influenza-like illness due to specific viral agents. The study, which was observational in design, was conducted in Rome and Naples, Italy. Cases of influenza-like illness were defined as individuals with fever >37.5 degrees C and at least one systemic and one respiratory symptom, recruited during the winters of 2004-2005, 2005-2006, and 2006-2007. Influenza and other respiratory viruses were identified using the polymerase chain reaction (PCR), performed on throat swabs. Basic individual information was collected using a standard form. A total of 580 persons were included in the analysis. Viral pathogens were identified in fewer than 50% of the cases. Overall, 240 viral agents were detected: 22.8% were positive for influenza viruses, 10.9% for adenoviruses, 6.0% for parainfluenza viruses, and 1.7% for respiratory syncytial virus. The month of diagnosis, and muscle and joint pain were associated with influenza virus, though the positive predictive value (PPV) was low. Abdominal pain was associated with adenovirus infection. Although the PPV of symptoms for influenza virus infection was low, especially in low activity periods, these findings may help clinicians to improve their ability to perform diagnoses.

Strategies to obtain multiple recombinant modified vaccinia Ankara vectors. Applications to influenza vaccines.

As a vaccination vector, MVA has been widely investigated both in animal models and humans. The construction of recombinant MVA (rMVA) relies on homologous recombination between an acceptor virus and a donor plasmid in infected/transfected permissive cells. Our construction strategy "Red-to-Green gene swapping" - based on the exchange of two fluorescent markers within the flanking regions of MVA deletion ΔIII, coupled to fluorescence activated cell sorting - is here extended to a second insertion site, within the flanking regions of MVA deletion ΔVI. Exploiting this strategy, both double and triple rMVA were constructed, expressing as transgenes the influenza A proteins HA, NP, M1, and PB1. Upon validation of the harbored transgenes co-expression, double and triple recombinants rMVA(ΔIII)-NP-P2A-M1 and rMVA(ΔIII)-NP-P2A-M1-(ΔVI)-PB1 were assayed for in vivo immunogenicity and protection against lethal challenge. In vivo responses were identical to those obtained with the reported combinations of single recombinants, supporting the feasibility and reliability of the present improvement and the extension of Red-to-Green gene swapping to insertion sites other than ΔIII.

Characterization of human H1N1 influenza virus variants selected in vitro with zanamivir in the presence of sialic acid-containing molecules.

Understanding the molecular mechanisms of influenza virus resistance to neuraminidase inhibitors is a main concern for their clinical use. In an attempt to reproduce in vivo selective conditions where influenza virus resistance to neuraminidase inhibitors can occur the zanamivir selection of an A/H1N1 influenza virus strain was carried out in Madin-Darby canine kidney cells performed in the presence or absence of sialic acid-containing inhibitor analogues that act as virus decoy receptors. The zanamivir-selected variants passaged in the presence of sialic acid-containing molecules resembling the human-like virus receptor lost the ability to bind red blood cells. Furthermore, whereas all zanamivir-selected variants exhibited a robust reduction in susceptibility to zanamivir in plaque assays only those obtained after extensive passages acquired a powerful neuraminidase enzyme resistance to zanamivir and oseltamivir. Evidence that balanced neuraminidase and hemagglutinin activities mediated by mutations induced during selection could play a role in the decrease of virus replication susceptibility to zanamivir is reported.

Different pH requirements are associated with divergent inhibitory effects of chloroquine on human and avian influenza A viruses.

Chloroquine is a 4-aminoquinoline previously used in malaria therapy and now becoming an emerging investigational antiviral drug due to its broad spectrum of antiviral activities. To explore whether the low pH-dependency of influenza A viruses might affect the antiviral effects of chloroquine at clinically achievable concentrations, we tested the antiviral effects of this drug on selected human and avian viruses belonging to different subtypes and displaying different pH requirements. Results showed a correlation between the responses to chloroquine and NH4Cl, a lysosomotropic agent known to increase the pH of intracellular vesicles. Time-of-addition experiments showed that the inhibitory effect of chloroquine was maximal when the drug had been added at the time of infection and was lost after 2 h post-infection. This timing approximately corresponds to that of virus/cell fusion. Moreover, there was a clear correlation between the EC50 of chloroquine in vitro and the electrostatic potential of the HA subunit (HA2) mediating the virus/cell fusion process. Overall, the present study highlights the critical importance of a host cell factor such as intravesicular pH in determining the anti-influenza activity of chloroquine and other lysosomotropic agents.

Evolutionary analysis of HA and NS1 genes of H5N1 influenza viruses in 2004-2005 epidemics.

H5N1 avian influenza viruses circulating in early 2004 in eastern Asia appeared to be under strong purifying selection, except for the hemagglutinin (HA) and nonstructural 1 (NS1) genes, where few amino acid positions were found under positive selection pressure. To evaluate whether the widespread circulation of the H5N1 viruses in the following years was accompanied by a change in the evolution of the HA and NS1, phylogenetic and positive selection analyses were performed on 89 HA and 57 NS1 sequences. Results showed that the number of HA positively selected sites decreased compared to 2004; no selection pressure for NS1 was found. These findings suggest a possible change in the adaptation of the H5N1 virus to birds.

Immunogenicity of modified vaccinia virus Ankara expressing the hemagglutinin stalk domain of pandemic (H1N1) 2009 influenza virus.

BACKGROUND: Vaccination offers protection against influenza, although current vaccines need to be reformulated each year. The development of a broadly protective influenza vaccine would guarantee the induction of heterosubtypic immunity also against emerging influenza viruses of a novel subtype. Vaccine candidates based on the stalk region of the hemagglutinin (HA) have the potential to induce broad and persistent protection against diverse influenza A viruses. METHODS: Modified vaccinia virus Ankara (MVA) expressing a headless HA (hlHA) of A/California/4/09 (CA/09) virus was used as a vaccine to immunize C57BL/6 mice. Specific antibody and cell-mediated immune responses were determined, and challenge experiments were performed by infecting vaccinated mice with CA/09 virus. RESULTS: Immunization of mice with CA/09-derived hlHA, vectored by MVA, was able to elicit influenza-specific broad cross-reactive antibodies and cell-mediated immune responses, but failed to induce neutralizing antibodies and did not protect mice against virus challenge. CONCLUSION: Although highly immunogenic, our vaccine was unable to induce a protective immunity against influenza. A misfolded and unstable conformation of the hlHA molecule may have affected its capacity of inducing neutralizing antiviral, conformational antibodies. Design of stable hlHA-based immunogens and their delivery by recombinant MVA-based vectors has the potential of improving this promising approach for a universal influenza vaccine.

Protective immunity against influenza in HLA-A2 transgenic mice by modified vaccinia virus Ankara vectored vaccines containing internal influenza proteins.

BACKGROUND: The emergence of novel strains of influenza A viruses with hemagglutinins (HAs) that are antigenically distinct from those circulating in humans, and thus have pandemic potential, pose concerns and call for the development of more broadly protective influenza vaccines. In the present study, modified vaccinia virus Ankara (MVA) encoding internal influenza antigens were evaluated for their immunogenicity and ability to protect HLA-A2.1 transgenic (AAD) mice from infection with influenza viruses. METHODS: MVAs expressing NP (MVA-NP), M1 (MVA-M1) or polymerase PB1 (MVA-PB1) of A/California/4/09 (CA/09) virus were generated and used to immunize AAD mice. Antibodies and CD8+T cell responses were assessed by ELISA and ELISPOT, respectively, and challenge experiments were performed by infecting vaccinated mice with CA/09 virus. RESULTS: CD8+T cells specific to immunodominant and subdominant epitopes on the internal influenza proteins were elicited by MVA-based vectors in AAD mice, whereas influenza-specific antibodies were detected only in MVA-NP-immunized mice. Both M1- and NP-based MVA vaccines, regardless of whether they were applied individually or in combination, conferred protection against lethal influenza virus challenge. CONCLUSION: Our data further emphasize the promising potential of MVA vector expressing internal antigens toward the development of a universal influenza vaccine.

A sensitive one-step real-time PCR for detection of avian influenza viruses using a MGB probe and an internal positive control.

BACKGROUND: Avian influenza viruses (AIVs) are endemic in wild birds and their introduction and conversion to highly pathogenic avian influenza virus in domestic poultry is a cause of serious economic losses as well as a risk for potential transmission to humans. The ability to rapidly recognise AIVs in biological specimens is critical for limiting further spread of the disease in poultry. The advent of molecular methods such as real time polymerase chain reaction has allowed improvement of detection methods currently used in laboratories, although not all of these methods include an Internal Positive Control (IPC) to monitor for false negative results. Therefore we developed a one-step reverse transcription real time PCR (RRT-PCR) with a Minor Groove Binder (MGB) probe for the detection of different subtypes of AIVs. This technique also includes an IPC. METHODS: RRT-PCR was developed using an improved TaqMan technology with a MGB probe to detect AI from reference viruses. Primers and probe were designed based on the matrix gene sequences from most animal and human A influenza virus subtypes. The specificity of RRT-PCR was assessed by detecting influenza A virus isolates belonging to subtypes from H1-H13 isolated in avian, human, swine and equine hosts. The analytical sensitivity of the RRT-PCR assay was determined using serial dilutions of in vitro transcribed matrix gene RNA. The use of a rodent RNA as an IPC in order not to reduce the efficiency of the assay was adopted. RESULTS: The RRT-PCR assay is capable to detect all tested influenza A viruses. The detection limit of the assay was shown to be between 5 and 50 RNA copies per reaction and the standard curve demonstrated a linear range from 5 to 5 x 108 copies as well as excellent reproducibility. The analytical sensitivity of the assay is 10-100 times higher than conventional RT-PCR. CONCLUSION: The high sensitivity, rapidity, reproducibility and specificity of the AIV RRT-PCR with the use of IPC to monitor for false negative results can make this method suitable for diagnosis and for the evaluation of viral load in field specimens.