Monitoring genetic diversity of influenza A(H1N1)pdm09 virus circulating during the post-pandemic period in Turkey.

The aimes of the present study were to monitor genetic alterations in the hemagglutin (HA) gene and oseltamivir resistance-related alterations in the neuraminidase (NA) gene of influenza A(H1N1)pdm09 viral isolates detected during the post-pandemic period in Turkey. A total of 2601 clinical specimens obtained from suspected cases of influenza A(H1N1)pdm09 viral infections were analyzed by real-time reverse transcription polymerase chain reaction. Viral RNA was detected in 233 (9%) clinical specimens. Sequence analysis of the HA gene in 16 random isolates showed >98.7% homology among each other and with the A/California/07/2009 vaccine strain. These 16 isolates had common (75%-100%) amino acid substitiutions at positions P83S, D97N, S203T, R205K, I216V, V249L, I321V, and E374K in the HA gene. In addition, two additional rare mutations were also observed at positions S162N (addition of a glycosylation site, 6.25%) and A186T (receptor binding region, 6.25%). On the basis of amino acid substitutions in the HA1 domain, majority of the Turkish isolates were classified in the genetic group v and others in the genetic groups ii, iii, and vi. In the present study, we observed an increase in the variety and ratio of mutations detected in the HA1 and HA2 domains of the HA gene; however, these alterations have not yet resulted in vaccine escape mutants in Turkey. In addition, analysis of the NA regions of the isolates revealed that oseltamivir resistance was not an issue in Turkey.

Antibody response after single H1N1 influenza vaccine in chronic dialysis patients.

The first influenza pandemic of this century happened through a rapid spread of a novel swine-derived H1N1 influenza virus. Vaccines are produced in order to avoid the infection. Children and other high risk groups are highly recommended for vaccination due to the high probability of contracting the virus. Chronic kidney disease patients were also accepted as a risk group and vaccination of all patients undergoing hemodialysis or peritoneal dialysis was recommended. The results of H1N1 influenza virus vaccine on patients receiving hemodialysis and peritoneal dialysis are analyzed. Antibody titers of both hemodialysis and peritoneal dialysis patients were elevated after vaccination. Peritoneal dialysis patients responded better.

Epidemiological, demographic, and molecular characteristics of laboratory-confirmed pandemic influenza A (H1N1) virus infection in Turkey, May 15-November 30, 2009.

A total of 19,973 clinical specimens obtained from suspected cases of pandemic influenza A virus infection were analyzed by real-time reverse transcription-polymerase chain reaction. Mutations in hemagglutinin (HA) gene and alteration at position 275 in neuraminidase (NA) gene of the randomly selected 29 isolates were detected by sequencing analysis. The virus RNA was detected in 47.3% of the clinical specimens. The pandemic flu cases increased from the 42nd week and peaked in the 46th week of 2009. This intensity continued to the end of the study period. Pandemic flu mainly affected children in the 5-14 year age group, without any gender predominance. The analyzed strains had >98.9% homology with vaccine strains and with each other. More than 37% of the isolates had mutation at position D222E/N on HA gene. There was no isolate harbored mutation at the position H275Y of the NA gene, indicating that the virus isolates currently circulating in Turkey are sensitive to oseltamivir.

Serological response to influenza vaccine after hematopoetic stem cell transplantation.

Vaccination is the best strategy to prevent influenza infection that is a potential cause of morbidity and mortality in immunosuppressed patients. Here, we evaluated the factors that may affect serological response to influenza vaccine in patients who have undergone hematopoetic stem cell transplantation (HSCT). Sixty-one HSCT recipients were included in the study during the 2007-2008 influenza season. Serum samples prior to vaccination and 6-10 weeks after vaccination were collected. Samples were assayed for antibodies to influenza virus A/H1N1, A/H3N2, and B strains by hemagglutination-inhibition assay. The patients were followed in terms of clinical symptoms up to the next influenza season and for adverse effects within a month after vaccination. Overall, pre-vaccine seroprotection rate against all vaccine antigens (A/H1N1, A/H3N2, and B antigens) was 45.1%, post-vaccine seroprotection rate 91% and seroconversion rate was 28.3%. Seroconversion rates were found to be low against B in patients who were vaccinated in the late influenza season (p = 0.018; respectively). Five patients (10.9%) had no immune response against H1N1. Adverse events were reported in 19.6% (n = 9/46) of the patients. In conclusion, the patients should be vaccinated as early as possible in the influenza season, before they are exposed to the virus.