Suda Louisirirotchanakul

An Avian Influenza H5N1 Virus That Binds to a Human-Type Receptor

ABSTRACT Avian influenza viruses preferentially recognize sialosugar chains terminating in sialic acid-α2,3-galactose (SAα2,3Gal), whereas human influenza viruses preferentially recognize SAα2,6Gal. A conversion to SAα2,6Gal specificity is believed to be one of the changes required for the introduction of new hemagglutinin (HA) subtypes to the human population, which can lead to pandemics. Avian influenza H5N1 virus is a major threat for the emergence of a pandemic virus. As of 12 June 2007, the virus has been reported in 45 countries, and 312 human cases with 190 deaths have been confirmed. We describe here substitutions at position 129 and 134 identified in a virus isolated from a fatal human case that could change the receptor-binding preference of HA of H5N1 virus from SAα2,3Gal to both SAα2,3Gal and SAα2,6Gal. Molecular modeling demonstrated that the mutation may stabilize SAα2,6Gal in its optimal cis conformation in the binding pocket. The mutation was found in approximately half of the viral sequences directly amplified from a respiratory specimen of the patient. Our data confirm the presence of H5N1 virus with the ability to bind to a human-type receptor in this patient and suggest the selection and expansion of the mutant with human-type receptor specificity in the human host environment.

Neutralization of primary and T-cell line adapted isolates of human immunodeficiency virus type 1: role of V3-specific antibodies

The role of the third variable domain (V3) of gp120 in the neutralization of primary and T-cell line adapted (TCLA) strains of human immunodeficiency virus type 1 (HIV-1) by serum from HIV-1-infected individuals was investigated. A primary virus isolate, M2424/4, when adapted to H9 cells, was more sensitive to neutralization on MT2 cells than the same stock passaged in PBMC. Neutralization of the PBMC-passaged stock by V3-specific MAbs was abrogated by addition of V3 (MN) peptide. However, exogenous V3 (MN) peptide failed to reduce the neutralization of this isolate on PBMC, or MT2 cells, by high titre anti-HIV-1 polyclonal human sera in contrast to the extensive reduction of neutralization by the same sera on MT2 cells using the prototype MN strain (4- to > or = 24-fold) and the TCLA M2424/H9 isolate (2- to 8-fold). These results indicate that the neutralization of primary virus isolates by serum from HIV-1-infected individuals is not significantly mediated by V3-specific antibodies.

Serological Response to the 2009 Pandemic Influenza A (H1N1) Virus for Disease Diagnosis and Estimating the Infection Rate in Thai Population

Background Individuals infected with the 2009 pandemic virus A(H1N1) developed serological response which can be measured by hemagglutination-inhibition (HI) and microneutralization (microNT) assays. Methodology/Principal Findings MicroNT and HI assays for specific antibody to the 2009 pandemic virus were conducted in serum samples collected at the end of the first epidemic wave from various groups of Thai people: laboratory confirmed cases, blood donors and health care workers (HCW) in Bangkok and neighboring province, general population in the North and the South, as well as archival sera collected at pre- and post-vaccination from vaccinees who received influenza vaccine of the 2006 season. This study demonstrated that goose erythrocytes yielded comparable HI antibody titer as compared to turkey erythrocytes. In contrast to the standard protocol, our investigation found out the necessity to eliminate nonspecific inhibitor present in the test sera by receptor destroying enzyme (RDE) prior to performing microNT assay. The investigation in pre-pandemic serum samples showed that HI antibody was more specific to the 2009 pandemic virus than NT antibody. Based on data from pre-pandemic sera together with those from the laboratory confirmed cases, HI antibody titers ≥40 for adults and ≥20 for children could be used as the cut-off level to differentiate between the individuals with or without past infection by the 2009 pandemic virus. Conclusions/Significance Based on the cut-off criteria, the infection rates of 7 and 12.8% were estimated in blood donors and HCW, respectively after the first wave of the 2009 influenza pandemic. Among general population, the infection rate of 58.6% was found in children versus 3.1% in adults.

One-year experience of nucleic acid technology testing for human immunodeficiency virus Type 1, hepatitis C virus, and hepatitis B virus in Thai blood donations

BACKGROUND: Blood donations collected at the National Blood Center, the Thai Red Cross Society, Bangkok, in 2007 were tested by nucleic acid amplification technology (NAT) using the Chiron TIGRIS/Procleix Ultrio test and the Roche cobas s 201/cobas TaqScreen multiplex (MPX) test.

Kinetics and Longevity of Antibody Response to Influenza A H5N1 Virus Infection in Humans

ABSTRACT Anti-H5N1 antibody was determined by microneutralization, hemagglutination inhibition, and Western blotting assays in serial blood samples collected from eight Thai patients, including four fatal cases and four survivors. The antibody was detected as early as 5 days and, typically, with an increase in titer in paired blood at about 15 days after disease onset. The anti-H5 antibody response was long-lasting, for almost 5 years in cases which can be followed that far. In addition, cross-neutralizing activity to related clade 1 viruses was observed.

Erythrocyte binding preference of avian influenza H5N1 viruses.

ABSTRACT Five erythrocyte species (horse, goose, chicken, guinea pig, and human) were used to agglutinate avian influenza H5N1 viruses by hemagglutination assay and to detect specific antibody by hemagglutination inhibition test. We found that goose erythrocytes confer a greater advantage over other erythrocyte species in both assays.

Role of maternal humoral immunity in vertical transmission of HIV-1 subtype E in Thailand

The significance of the maternal humoral immune response in relation to vertical transmission of HIV-1 was investigated in 123 mothers infected with subtype E from Thailand. Antibody binding titers to HIV-1 env domains (monomeric gp120, the CD4/gp120 binding site [BS], V3 loop, and gp41) and antibody-mediated neutralization of primary and T-cell line-adapted (TCLA) subtypes B and E HIV-1 isolates were investigated. No correlation between maternal anti HIV-1 antibodies at delivery and vertical transmission of HIV-1 subtype E was found. However, a trend to higher titer antibody-mediated cross-neutralization of a heterologous subtype B TCLA isolate, HIV-1MN, was observed in nontransmitting mothers postpartum. The HIV-1-specific antibody titers in these infected mothers increased significantly from delivery to 6 months postpartum (p < .05), but this was only partially attributable to hemodilution and an additional factor or factors appear to affect humoral immunity to HIV-1 during late pregnancy.

Characterization of sera from subjects infected with HIV-1 subtypes B and E in Thailand by antibody binding and neutralization.

The range and specificity of the humoral immune response to HIV-1 subtypes B and E was investigated in Thai samples. Sera from HIV-1-positive subjects, consisting of subtypes B (n = 24) and E (n = 138), were characterized in relation to the neutralization of primary isolates and T-cell line-adapted (TCLA) strains and binding to monomeric gp120, the CD4/gp120 binding site (BS), and V3 peptides. A subtype-specific pattern of antibody binding was observed with the exception of the CD4/gp 120MN BS. Neutralization of TCLA strains (n = 4) was strongly type-specific (p = .002); however, neutralization of primary isolates (n = 8) was weak and group specific. Thus, the subtype specificity of B and E sera in the neutralization of TCLA strains, but not primary isolates, supports the dominance of the V3 region in TCLA virus neutralization but does not support the distinction of subtypes B and E as discrete neutralization serotypes in Thailand.

Erythrocyte binding preference of 16 subtypes of low pathogenic avian influenza and 2009 pandemic influenza A (H1N1) viruses.

All 16 subtypes of avian influenza viruses of low pathogenicity (LPAIV) as well as their hemagglutinin (H) antigens, and four 2009 pandemic influenza A (H1N1) virus isolates were assayed for hemagglutinating activity against 5 erythrocyte species: goose, guinea pig, human group O, chicken and horse. Of all viruses and antigens assayed, the highest hemagglutination (HA) titers were obtained with goose and guinea pig erythrocytes. Hemagglutinating activity of replicating LPAIV and LPAIV antigens decreased, in order, with chicken and human group O; meanwhile, horse erythrocytes yielded lowest or no HA titer. Moreover, the 2009 pandemic viruses did not agglutinate both horse and chicken erythrocytes. Our study concluded that goose and guinea pig erythrocytes are the best in HA assay for all subtypes of influenza viruses.

The distribution of hepatitis B virus genotypes in Thailand

Phylogenetic analysis was performed on hepatitis B virus (HBV) strains obtained from 86 hepatitis B surface antigen (HBsAg) positive donors from Thailand originating throughout the country. Based on the S gene, 87.5% of strains were of genotype C while 10.5% were of genotype B, with all genotype B strains obtained from patients originating from the central or the south Thailand. No genotype B strains were found in the north of Thailand. Surprisingly, one patient was infected with a genotype H strain while another patient was infected with a genotype G strain. Complete genome sequencing and recombination analysis identified the latter as being a genotype G and C2 recombinant with the breakpoint around nucleotide position 700. The origin of the genotype G fragment was not identifiable while the genotype C2 fragment most likely came from strains circulating in Laos or Malaysia. The performance of different HBsAg diagnostic kits and HBV nucleic acid amplification technology (NAT) was evaluated. The genotype H and G/C2 recombination did not interfere with HBV detection. J. Med. Virol. 84:1541–1547, 2012.