Influenza A and B viruses form different genera, which were originally distinguished by antigenic differences in their nucleoproteins and matrix 1 proteins. Cross-protection between these two genera has not been observed in animal experiments, which is consistent with the low homology in viral proteins common to both viruses except for one of three polymerase proteins, polymerase basic 1 (PB1). Recently, however, antibody and CD4+ T cell epitopes conserved between the two genera were identified in humans. A protective antibody epitope was located in the stalk region of the surface glycoprotein, hemagglutinin, and a CD4+ T cell epitope was located in the fusion peptide of the hemagglutinin. The fusion peptide was also found to contain antibody epitopes in humans and animals. A short stretch of well-conserved peptide was also identified in the other surface glycoprotein, neuraminidase, and antibodies binding to this peptide were generated by peptide immunization in rabbits. Although PB1, the only protein which has relatively high overall sequence homology between influenza A and B viruses, is not considered an immunodominant protein in the T cell responses to influenza A virus infection, amino acid sequence comparisons show that a considerable number of previously identified T cell epitopes in the PB1 of influenza A viruses are conserved in the PB1 of influenza B viruses. These data indicate that B and T cell cross-reactivity exists between influenza A and B viruses, which may have modulatory effects on the disease process and recovery. Although the antibody titers and the specific T cell frequencies induced by natural infection or standard vaccination may not be high enough to provide cross protection in humans, it might be possible to develop immunization strategies to induce these cross-reactive responses more efficiently.
Effect of Race/Ethnicity and Socioeconomic Status on Pandemic H1N1-Related Outcomes in Massachusetts
Objectives. We linked hospital discharge and American Community Survey and US Census data to investigate 2009 H1N1 influenza (H1N1)-related outcomes by racial/ethnic groups and socioeconomic status (SES).
Methods. We examined the population discharged from any acute care hospital in Massachusetts and calculated rates of intensive care unit (ICU) stay by racial/ethnic and SES groups between April 26 and September 30, 2009. We used logistic regression models to identify predictors of ICU stay.
Results. Of 4874 H1N1-related hospitalizations, 526 (11%) were admitted to the ICU. Those in less affluent SES groups had lower risk of ICU stay than the most affluent SES group. Compared with Whites, Hispanics had significantly lower risk of 2009 H1N1-related ICU stay (odds ratio = 0.52; 95% confidence interval = 0.32, 0.86). Only 13% of Whites admitted to the ICU were in the lowest SES group, compared with 63% of Hispanics and 43% of Blacks.
Conclusions. To our knowledge, this is the first statewide description of 2009 H1N1 influenza-related ICU stays according to racial/ethnic group and SES in the United States. Future work should investigate evidence related to social determinants of health among racial/ethnic groups to reduce disparities in relation to pandemic influenza.
(Am J Public Health. Published online ahead of print November 14, 2013: e1-e8. doi:10.2105/AJPH.2013.301626).
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Nature 503 449 doi: 10.1038/503449a