Antibody Response to Influenza Hemagglutinin Conserved Stalk Domain after Sequential Immunization with Old Vaccine Strains.

Hemagglutinin (HA) is the major envelope glycoprotein and antigen on the surface of influenza virions. The glycoprotein comprises a globular head and a stalk region. While immunodominant epitopes on influenza HA head are highly variable, the stalk domain is conserved.

Intra-serotypic antigenic diversity of dengue virus serotype 3 in Thailand during 2004-2015.

In addition to the well-known differences among the four dengue serotypes, intra-serotypic antigenic diversity has been proposed to play a role in viral evolution and epidemic fluctuation. A replacement of genotype II by genotype III of dengue virus serotype 3 (DENV3) occurred in Thailand during 2007-2014, raising questions about the role of intra-serotypic antigenic differences in this genotype shift. We characterized the antigenic difference of DENV3 of genotypes II and III in Thailand, utilizing a neutralizing antibody assay with DENV3 vaccine sera and monotypic DENV3 sera.

A live attenuated H5N2 prime- inactivated H5N1 boost vaccination induces influenza virus hemagglutinin stalk specific antibody responses.

Background: The emergence and spread of highly pathogenic avian influenza (H5N1) viruses have raised global concerns of a possible human pandemic, spurring efforts towards H5N1 influenza vaccine development and improvements in vaccine administration methods. We previously showed that a prime-boost vaccination strategy induces robust and broadly cross-reactive antibody responses against the hemagglutinin globular head domain. Here, we specifically measure antibodies against the conserved hemagglutinin stem region in serum samples obtained from the prior study to determine whether stalk-reactive antibodies can also be induced by the prime-boost regimen.

H1N1 seasonal influenza virus evolutionary rate changed over time.

It was previously shown that the seasonal H1N1 influenza virus antigenic drift occurred at a slower rate than the seasonal H3N2 virus during the first decade of the 21th century. It was hypothesized that the slower antigenic evolution led to a decrease in average ages of infection, which in turn resulted in lower level of global viral circulation. It is unclear what caused the difference between the two viruses, but a plausible explanation may be related to the fact that the H1N1 virus had been in human population for much longer than the H3N2 virus.