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trH3N2 Pandemic Vaccine Target Media Myth
Recombinomics Commentary 20:20
November 5, 2011

After a spate of human cases of swine H3N2 infection last year, the CDC asked the laboratory that makes candidate viruses for vaccines to make one for a swine H3N2 vaccine. That lab is at New York Medical College in Valhalla.

That virus had the same hemagglutinin and neuraminidase genes — the H and N in a virus's name — as the new virus does.

The above comments are internally inconsistent and incorrect.  The novel trH3N2 that emerged in  2011 is a reassortant which has changed the N gene, as well as the M gene.  Therefore, none of human trH3N2 isolates from 2010 match the H and N combination in the new 2011 trH3N2 human contagion.  One of the hallmarks of the virus was the acquisition of flu genes from a variety parental triple reassortants, which had been identified spreviously in humans.

The H and N in the new trH3N2 matched two human isolates from Pennsylvania, A/Pennsylvania/40/2010 and A/Pennsylvania/14/2010.  The H was also in other human isolates from 2010, including A/Wisconsin/12/2010 and A/Minnesota/11/2010.  The N was in other swine isolates, including Pennsylvania swine closely related to Pennsylvania/14/2010, as well as a number of swine H1N2 isolates.

The vaccine target for pandemic trH3N2 is A/Minnesota/11/2010 (MN/11/10), as indicated by sequences released by the CDC at GISAID in August.  The confirmation of this target was made in the WHO September report on pandemic vaccine targets.  MN/11/10 was the only trH3N2 target cited.  Table 7 in that report detailed the cross reactivity of the MN/11/10 anti-sera (listed as MN/10) with various targets, including other human trH3N2 isolates from 2009/2010 (A/Kansas/13/2009, A/Pennsylvania/14/2010, A/Wisconsin/12/2010) which were also being tested as targets), as well as the novel 2011 trH3N2 human contagion, A/Indiana/08/2011,which produced a high titer (1280), indicating the trH3N2 pandemic vaccine target will remain MN/11/10.

The N from MN/11/10 was distinct and did not match the other 2010 trH3N2 isolates (or the 2011 isolates).  Thus, although the N gene of MN/11 is distinct, the titer against the 2011 test sample is high.
MN/11/10 is from the index case (31M) in the Minnesota cluster.  It was reported in the December 17, 2010 “Did You Hear?”, while his contacts were “under investigation”.  In the week 21 MMWR (6 months after the initial report) the results of the investigation were made public.  The daughter of the index case was trH3N2 confirmed serologically.  Other symptomatic family members were “inconclusive”.  Thus, the trH3N2 was transmitting human to human

That confirmation was the most recent trH3N2 confirmed case prior to the detection of the 2011 trH3N2 cases for which all seven of the sequences have been remarkably stable, signaling adaptation to and transmission in humans.

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