Archive for July 20th, 2012

A bit of viral archeology

20 July, 2012

We were sifting through stuff found in a service room the other day, when I found a box of glass slides – undisturbed since about 1979 or so.  A very interesting box: double- and triple-width microscope slides, coated with dried agarose gel, and stained with Coomassie Brilliant Blue.  With my handwriting on them.  With whole virus electropherograms on them….

Backing up a bit: back in a previous research career, I was a plant virologist who had become an expert, during my MSc project, on physical and serological techniques to do with plant viruses, and the multicomponent isometric bromoviruses in particular.  This included differential, density gradient and analytical centrifugation; methods for purification of virus, capsid protein and genomic nucleic acid (all ssRNA); double-diffusion gel precipitin (=Ouchterlony’s technique) assays; the then new-fangled enzyme-linked immunosorbent assays (ELISA) – and whole-virus agarose gel electrophoresis, and immunoelectrophoresis.

This is mostly published – in my first-ever paper published in 1981, that I was too naive to know I shouldn’t submit to a good journal, so got it into Virology.

However, there were some bits that only ever made it into my Masters write-up – and then only in monochrome.  Here, then, is a little piece of virological and personal history: electropherograms of Brome mosaic bromovirus strains, electrophoresed in 1% agarose on glass slides, then dried down and stained with CBB.  Left all alone, in a drawer, undisturbed from then till now.

It is very easy to see how the three strains on the right have a pI between pH 6.0 and pH 7.5, and that the two on the left and the one on the furthest right seem to be mixtures of differently-charged variants.

Interesting technique, this: it’s a very nice way of characterising and in fact separating virus strains that differ only in a couple of charges in their capsid proteins – for future infectivity assays, if need be, or for preparative purposes by sucrose gradient “zone” electrophoresis, as done here.  The thing about the slide gels, though, is that it is very cheap, very easy, and very quick – ideal for practicals and demonstrations.

I’m going to make my current MSc student characterise his plant-made virus-like particles this way…B-)

Oh, and while we’re archeologising: here is a 30+ year experiment in sedimentation at one gravity, of Tobacco mosaic virus.  Shows why one should stay in one place for a while.  Or not…B-)

Evidence for Antigenic Seniority in Influenza A (H3N2) Antibody Responses in Southern China

20 July, 2012

See on Scoop.itVirology and Bioinformatics from

“A key observation about the human immune response to repeated exposure to influenza A is that the first strain infecting an individual apparently produces the strongest adaptive immune response. Although antibody titers measure that response, the interpretation of titers to multiple strains – from the same sera – in terms of infection history is clouded by age effects, cross reactivity and immune waning. From July to September 2009, we collected serum samples from 151 residents of Guangdong Province, China, 7 to 81 years of age. Neutralization tests were performed against strains representing six antigenic clusters of H3N2 influenza circulating between 1968 and 2008, and three recent locally circulating strains. Patterns of neutralization titers were compared based on age at time of testing and age at time of the first isolation of each virus. Neutralization titers were highest for H3N2 strains that circulated in an individual’s first decade of life (peaking at 7 years). Further, across strains and ages at testing, statistical models strongly supported a pattern of titers declining smoothly with age at the time a strain was first isolated. Those born 10 or more years after a strain emerged generally had undetectable neutralization titers to that strain (<1:10). Among those over 60 at time of testing, titers tended to increase with age. The observed pattern in H3N2 neutralization titers can be characterized as one of antigenic seniority: repeated exposure and the immune response combine to produce antibody titers that are higher to more ‘senior’ strains encountered earlier in life.”


An interesting paper, which helps explain several observations made over the years with pandemic flu: for example, in the 2009 H1N1 pandemic, older people seemed to be more protected – and rhe same was probably true of the 1918 pandemic.

See on