BK virus (BKV) plasma dynamics in patients with BKV-associated hemorrhagic cystitis following allogeneic stem cell transplantation.

INTRODUCTION: The use of real-time polymerase chain reaction testing in the investigation of BK virus (BKV)-associated disease has been widely studied in renal transplant recipients; however, far less research has been done in this area with respect to the plasma BK viral load dynamics of BKV hemorrhagic cystitis (BKV-HC) in hematopoietic stem cell transplant recipients. AIM: The aim of this study was to examine the BK viral load dynamics in plasma samples collected from patients post transplant who had laboratory-confirmed BKV-HC. METHODS: Patients who developed BK viremia were compared with patients who did not develop viremia, and a statistical comparison of risk factors for viremia was performed. Seventeen patients were included in this study. Urine samples from the day of BKV diagnosis were available in 13 of the 17 cases. In total, 154 archived plasma samples from around the time of the BKV-HC event were also included in the study from these 17 patients. RESULTS: The median time from transplantation to the onset of detectable viremia was 68 days. The median viral load in the 13 urine samples was 1.8 × 10(8) copies/mL, which was significantly higher than the median viral load in the 38 positive plasma samples of 6.6 × 10(2) copies/mL (Mann-Whitney test, U = 16, P < 0.001). CONCLUSION: The lymphocyte count on the day of the positive BKV test was significantly lower in patients with BKV viremia than in patients with no viremia (P = 0.02) and also the white cell and platelet counts were lower on the day of the first positive BKV test. Although there is not inter-patient consistency as regards correlation between urinary BK viral loads and severity of clinical BKV-HC, in individual patients the decline in viral load in plasma did correlate with clinical recovery.

Emergence and phylogenetic analysis of amantadine-resistant influenza a subtype H3N2 viruses in Dublin, Ireland, over Six Seasons from 2003/2004 to 2008/2009.

OBJECTIVES: To determine the prevalence of amantadine-resistant influenza A viruses and perform genetic analysis of isolates collected in Dublin during six seasons (2003/2004 to 2008/2009). METHODS: Known mutations in the matrix 2 gene (M2) conferring amantadine resistance were screened and phylogenetic analysis of the haemagglutinin gene (HA) performed. RESULTS: Of 1,180 samples, 67 influenza A viruses were isolated, 88% of which were subtype H3N2. Amantadine resistance was only found in subtype H3N2 and increased dramatically from 7% in 2003/2004 to 90% in 2008/2009. A maximum likelihood tree of the HA gene of influenza A H3N2 isolates differentiated them into two distinct clades, clade N and clade S, where the majority of isolates were amantadine-resistant and amantadine-sensitive, respectively. The clades were distinguished by amino acid substitutions, S193F and D225N, which probably conferred a selective advantage for the spread of such viruses. Phylogenetic analysis showed some degree of antigenic drift when compared with the vaccine strain of the corresponding season. CONCLUSIONS: This study showed that circulation in Ireland of a distinct lineage, clade N, among H3N2 viruses favoured emergence of amantadine resistance. Furthermore, comparison of circulating Irish viruses and vaccine strains used in the northern hemisphere showed high similarity.