Polymerase activity of hybrid ribonucleoprotein complexes generated from reassortment between 2009 pandemic H1N1 and seasonal H3N2 influenza A viruses.

BACKGROUND: A novel influenza virus (2009 pdmH1N1) was identified in early 2009 and progressed to a pandemic in mid-2009. This study compared the polymerase activity of recombinant viral ribonucleoprotein (vRNP) complexes derived from 2009 pdmH1N1 and the co-circulating seasonal H3N2, and their possible reassortants. RESULTS: The 2009 pdmH1N1 vRNP showed a lower level of polymerase activity at 33°C compared to 37°C, a property remenisence of avian viruses. The 2009 pdmH1N1 vRNP was found to be more cold-sensitive than the WSN or H3N2 vRNP. Substituion of 2009 pdmH1N1 vRNP with H3N2-derived-subunits, and vice versa, still retained a substantial level of polymerase activity, which is probably compartable with survival. When the 2009 pdmH1N1 vRNP was substituted with H3N2 PA, a significant increase in activity was observed; whereas when H3N2 vRNP was substituted with 2009 pdmH1N1 PA, a significant decrease in activity occurred. Although, the polymerase basic protein 2 (PB2) of 2009 pdmH1N1 was originated from an avian virus, substitution of this subunit with H3N2 PB2 did not change its polymerase activity in human cells. CONCLUSIONS: In conclusion, our data suggest that hybrid vRNPs resulted from reassortment between 2009 pdmH1N1 and H3N2 viruses could still retain a substantial level of polymerase activity. Substituion of the subunit PA confers the most prominent effect on polymerase activity. Further studies to explore the determinants for polymerase activity of influenza viruses in associate with other factors that limit host specificity are warrant.

Clinical spectrum of human rhinovirus infections in hospitalized Hong Kong children.

BACKGROUND: Human rhinovirus (HRV) is classified into A, B, and C genogroups. HRVs cause mild upper respiratory infections, but HRV-C was recently found to be a major cause of asthma exacerbation in whites. This study elucidated disease spectrum of HRV infections among Hong Kong children hospitalized with respiratory illnesses. METHODS: This retrospective study recruited 128 children with asthma exacerbations and 192 inpatient controls without allergy and hospitalized for respiratory illnesses within the same week. Their clinical information was retrieved from case records. HRVs in nasopharyngeal aspirates were detected by molecular assays using primers targeting consensus VP4/VP2 coding regions, and their genogroups identified by sequencing. RESULTS: The mean (standard deviation) age of cases and controls was 5.6 (3.6) years and 5.4 (3.8) years, respectively (P = 0.601). HRV was detected in 107 (84.9%) cases and 63 (33.0%) controls (P < 0.0001), and HRV-C in 69.8% and 18.8% of these groups, respectively (P < 0.0001). Detection of HRV-A and -B was similar between these groups (P > 0.15). More subjects with HRV-C needed oxygen supplementation (11.1% vs. 2.6%; P = 0.043). Among controls, HRV infection was associated with acute bronchiolitis (P < 0.001) and bronchitis (P = 0.04), which paralleled those of HRV-C. HRV-A was associated with acute bronchiolitis (P = 0.005). Phylogenetic analysis revealed a diverse group of HRV serotypes (21 for HRV-A, 2 for HRV-B, and 32 for HRV-C). CONCLUSIONS: HRV-C is associated with asthma exacerbation, whereas the presence of all HRVs, or either HRV-A or HRV-C alone, is associated with wheezing respiratory infections in nonasthmatic children. HRV is an important respiratory virus responsible for childhood wheezing illnesses.

Hepatitis B virus reactivation in lymphoma patients with prior resolved hepatitis B undergoing anticancer therapy with or without rituximab.

PURPOSE: Reactivation of hepatitis B virus (HBV) infection is a well-recognized complication in cancer patients with chronic HBV (hepatitis B surface antigen [HBsAg] positive) undergoing cytotoxic chemotherapy. In patients who have resolved HBV (HBsAg negative and antibody to hepatitis B core antigen [anti-HBc] +/- antibody to hepatitis B surface antigen [anti-HBs] positive), such incidence has been much less common until recent use of rituximab. In this study on HBsAg-negative/anti-HBc-positive lymphoma patients, the objectives were to determine the HBV reactivation rate in patients treated with rituximab-containing chemotherapy and to compare it with the rate in patients treated without rituximab. PATIENTS AND METHODS: Between January 2003 and December 2006, all patients diagnosed with CD20(+) diffuse large B-cell lymphoma (DLBCL) had HBsAg determined before anticancer therapy. They were treated with either cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) alone or rituximab plus CHOP (R-CHOP). HBsAg-negative patients had anti-HBc determined; serum was stored for anti-HBs and HBV DNA. All patients were observed for HBV reactivation, which was defined as detectable HBV DNA with ALT elevation during and for 6 months after anticancer therapy. RESULTS: Among 104 CD20(+) DLBCL patients, 80 were HBsAg negative. Of the latter, 46 patients (44.2%) were HBsAg negative/anti-HBc positive; 25 of these patients were treated with CHOP, and none had HBV reactivation. In contrast, among the 21 patients treated with R-CHOP, five developed HBV reactivation, including one patient who died of hepatic failure (P = .0148). Exploratory analysis identified male sex, absence of anti-HBs, and use of rituximab to be predictive of HBV reactivation. CONCLUSION: Among HBsAg-negative/anti-HBc-positive DLBCL patients treated with R-CHOP, 25% developed HBV reactivation. Close monitoring until at least 6 months after anticancer therapy is required, with an alternative approach of prophylactic antiviral therapy to prevent this potentially fatal condition.

A wide spectrum of dengue IgM and PCR positivity post-onset of illness found in a large dengue 3 outbreak in Pakistan.

During a large outbreak of dengue serotype 3 in Pakistan in 2006, multiple serum samples were routinely collected for laboratory testing. Two hundred ninety-seven samples were collected between August and November 2006. Serological testing for dengue IgM was performed in Pakistan and polymerase chain reaction (PCR) testing for dengue RNA detection and serotyping were performed in Hong Kong. Dengue-specific IgM was detectable as early as 1 day, and dengue RNA remained detectable for up to 14 days, post-onset of illness. Further statistical analysis found that IgM status (positive, negative, or equivocal) was significantly correlated to clinical (duration of illness, severity of patient-reported arthralgia pain, the presence of any evidence of bleeding, a positive tourniquet test, shock), and other laboratory (platelet and total white cell counts) parameters. In contrast, the qualitative dengue RNA status (PCR positive or negative) was not statistically significantly correlated with any of these other parameters. The results for this population during this outbreak, obtained from single acute samples, demonstrate a wide range of intervals post-onset of illness during which dengue IgM and dengue RNA may be detected. Interestingly, in this study, the dengue IgM positivity correlates more closely with significant clinical illness than the dengue RNA positivity, which may be a feature specific to this particular outbreak.

Seasonality of influenza A(H3N2) virus: a Hong Kong perspective (1997-2006).

BACKGROUND: The underlying basis for the seasonality of influenza A viruses is still uncertain. Phylogenetic studies investigated this phenomenon but have lacked sequences from more subtropical and tropical regions, particularly from Southeast Asia. METHODOLOGY/PRINCIPAL FINDINGS: 281 complete hemagglutinin (HA) and neuraminidase (NA) sequences were obtained from influenza A(H3N2) viruses, collected over 10 years (1997-2006) from Hong Kong. These dated sequences were analyzed with influenza A(H3N2) vaccine strain sequences (Syd/5/97, Mos/10/99, Fuj/411/02, Cal/7/04) and 315 other publicly available dated sequences from elsewhere, worldwide. In addition, the NA sequence alignment was inspected for the presence of any naturally occurring, known, neuraminidase inhibitor (NAI) resistance-associated amino acid mutations (R292K and E119V). Before 2001, the Hong Kong HA and NA sequences clustered more closely with the older vaccine sequences (Syd/5/97, Mos/10/99) than did sequences from elsewhere. After 2001, this trend reversed with significant clusters containing HA and NA sequences from different locations, isolated at different times, suggesting that viral migration may account for much of the influenza A(H3N2) seasonality during this 10-year period. However, at least one example from Hong Kong was found suggesting that in some years, influenza A(H3N2) viruses may persist in the same location, perhaps continuing to circulate, sub-clinically, at low levels between seasons, to re-emerge in the influenza season the following year, relatively unchanged. None of these Hong Kong influenza A(H3N2) NA sequences contained any of the known NAI-resistance associated mutations. CONCLUSIONS/SIGNIFICANCE: The seasonality of influenza A(H3N2) may be largely due to global migration, with similar viruses appearing in different countries at different times. However, occasionally, some viruses may remain within a single location and continue to circulate within that population, to re-emerge during the next influenza season, with relatively little genetic change. Naturally occurring NAI resistance mutations were absent or, at least, very rare in this population.

Emergence of adamantane-resistant influenza A(H3N2) viruses in Hong Kong between 1997 and 2006.

Resistance to adamantanes for treating influenza A(H3N2) has increased dramatically, worldwide, over the past 5 years. A comprehensive 10-year data set on the rise of adamantane-resistance in Hong Kong is reported. Nucleotide sequences encoding the M2-ion channel of influenza A(H3N2) were obtained from 281 H3N2 isolates collected from adamantane-naive children admitted to a teaching hospital in Hong Kong, between 1997 and 2006. These sequences were screened for the presence of recognized adamantane resistance-associated amino acid mutations (L26F, V27A, A30T, S31N, G34E). The amantadane (rimantadine is not used in Hong Kong) usage for this hospital during this period was also collated. Fifty-eight isolates harbored at least one of these resistance signatures, the majority (57/58) being S31N, which increased rapidly over 2003-2005 from 20% to 83.3%. Other amino acid mutations, not previously associated with adamantane resistance, were also found. In particular, I51V was found to rise in frequency, along with S31N, though the significance of this mutation remains uncertain at present. A rise in amantadane usage occurred in Hong Kong between 2000 and 2002, which slightly preceded the subsequent rise in adamantane-resistant influenza A(H3N2) isolates. This study shows a temporal correlation between increases in amantadane prescriptions and the prevalence of adamantane-resistant influenza A(H3N2) viruses in Hong Kong. The underlying reasons for these findings are unclear and similar studies are required elsewhere to elucidate these and prevent this spread of drug-resistance happening again in future.

Hypophysitis presented as inflammatory pseudotumor in immunoglobulin G4-related systemic disease.

Immunoglobulin (Ig) G4-related systemic disease is a recently characterized entity. The best-known manifestation is pancreatitis. Other systemic involvements are also described. Three cases of this disease with hypophyseal involvement have been reported in the literature, all diagnosed clinically. We herein present the first case of IgG4-related hypophysitis diagnosed histopathologically. The patient is a 77-year-old Chinese man with a pituitary tumor. Histologic examination of the resected tumor showed hypophysitis with features of inflammatory pseudotumor. Clinical review showed history of pancreatitis and cholecystitis 4 years ago. The pancreatic biopsy and gall bladder specimens obtained previously had the same pathologic features of inflammatory pseudotumor. Immunohistochemistry highlighted abundant IgG4-positive plasma cells in all 3 specimens. Serum IgG4 level was also elevated. A diagnosis of IgG4-related systemic disease was confirmed. This is the first case of intracranial inflammatory pseudotumor shown to be associated with IgG4-related systemic disease.