Stability of different influenza subtypes: How can high hydrostatic pressure be a useful tool for vaccine development?

BACKGROUND: Avian influenza A viruses can cross naturally into mammals and cause severe diseases, as observed for H5N1. The high lethality of human infections causes major concerns about the real risk of a possible pandemic of severe diseases to which human susceptibility may be high and universal. High hydrostatic pressure (HHP) is a valuable tool for studies regarding the folding of proteins and the assembly of macromolecular structures such as viruses; furthermore, HHP has already been demonstrated to promote viral inactivation. METHODS: Here, we investigated the structural stability of avian and human influenza viruses using spectroscopic and light-scattering techniques. We found that both particles have similar structural stabilities and that HHP promotes structural changes. RESULTS: HHP induced slight structural changes to both human and avian influenza viruses, and these changes were largely reversible when the pressure returned to its initial level. The spectroscopic data showed that H3N2 was more pressure-sensitive than H3N8. Structural changes did not predict changes in protein function, as H3N2 fusion activity was not affected, while H3N8 fusion activity drastically decreased. The fusion activity of H1N1 was also strongly affected by HHP. In all cases, HHP caused inactivation of the different influenza viruses. CONCLUSIONS: HHP may be a useful tool for vaccine development, as it induces minor and reversible structural changes that may be associated with partial preservation of viral biological activities and may potentiate their immunogenic response while abolishing their infectivity. We also confirmed that, although pressure does not promote drastic changes in viral particle structure, it can distinctly affect viral fusion activity.

Isolation, sequencing and phylogenetic analysis of the hemagglutinin, neuraminidase and nucleoprotein genes of the Chilean equine influenza virus subtypes H7N7 and H3N8.

We report here on the isolation and sequencing of the hemagglutinin, neuraminidase and nucleoprotein genes of the Chilean equine influenza virus subtypes H7N7 (A/equi-1/Santiago/77, Sa77) and H3N8 (A/equi-2/Santiago/85, Sa85). The sequences obtained allowed a variability analysis, which indicated significant differences when compared with other isolates. We found that Chilean isolates are more similar to the North American variety than to European isolates. Isolate Sa77 is a good candidate for inclusion in a vaccine as it is the latest isolate of the subtype H7N7 and is probably better-adapted to the equine host. Isolate Sa85, of subtype H3N8, also appears to be a good candidate since it has no significant differences in the main antigenic sites with recent isolates.

Isolation, sequencing and phylogenetic analysis of the hemagglutinin, neuraminidase and nucleoprotein genes of the Chilean equine influenza virus subtypes H7N7 and H3N8

We report here on the isolation and sequencing of the hemagglutinin, neuraminidase and nucleoprotein genes of the Chilean equine influenza virus subtypes H7N7 (A⁄equi-1⁄Santiago⁄77, Sa77) and H3N8 (A⁄equi-2⁄Santiago⁄85, Sa85) . The sequences obtained allowed a variability analysis, which indicated significant differences when compared with other isolates. We found that Chilean isolates are more similar to the North American variety than to European isolates. Isolate Sa77 is a good candidate for inclusion in a vaccine as it is the latest isolate of the subtype H7N7 and is probably better-adapted to the equine host. Isolate Sa85, of subtype H3N8, also appears to be a good candidate since it has no significant differences in the main antigenic sites with recent isolates.

Influência do pH na atividade hemolítica de uma amostra aviária de vírus influnza A / Influence of pH on hemolytic activity of an avian sample of influenza a virus

A atividade de fusäo, depende de pH, de uma amostra aviária de Vírus Influenza A com eritrócitos de galinhas, foi investigada usando oteste de hemólise (HL). Este teste é baseado na quantificaçäo de hemoglobina (Hb) liberada como consequência da fusäo vírus/eritrócito. A atividade hemolítica desta preparaçäo viral pode ser demonstrada na faixa de pH ácido (5.0-5.8), o que está relacionado à ocorrência de uma mudança conformacional nas moléculasda hemaglutinina (HA) sob estas condiçöes. A atividade fusogênica era rapidamente inativada após incubaçäo do vírus, em pH ácido, a 37 graus C, na ausência de eritrócitos, sugerindo que a mudança conformacional da HA do vírus pode ser responsável pela ativaçäo e/ou inativaçäo da capacidade fusogênica. O estudo da reaçäo de HL mostra que elevando-se a concentraçäo de eritrócitos, enquanto a concentraçäo de vírus permanece constante, pode-se observar um aumento na liberaçäo de hemoglobina (Hb), o qual sugere que, provavelmente, os vírus tiveram a chance de encontrar um maior número de células susceptíveis. Uma vez que a Hb em soluçäo muda de tonalidade em funçäo do pH em que se encontra, um fator de correçäo foi utilizado após o ensaio colorimétrico.

[A structural protein study of the influenza A (H1N1) virus by polyacrylamide gel electrophoresis]. / Estudio de las proteínas estructurales de influenzavirus A (H1N1) por electroforesis en gel de poliacrilamida.

Influenza is an acute respiratory disease typically appearing as an epidemic. Three immunological types of the influenza virus are known: A, B and C. Continually, antigen changes occur, especially in type A. Therefore, a comparative study was carried out on 4 influenza A(H1N1) virus strains in relation to protein structure (surface antigens), by using polyacrylamide gel electrophoresis by the modified Laemmli method. The objective was to compare the structural proteins of the A/Havana/1292/78 (H1N1) national strain with the proteins of 3 international pattern strains. In all the cases, 6 bands were detected by densitometry. In the 4 strains studied the most abundant protein was M. Great differences between the Cuban strain and the 3 international patterns were not seen.