Evolution of H3N2 Influenza Virus in a Guinea Pig Model

Studies of influenza virus evolution under controlled experimental conditions can provide a better understanding of the consequences of evolutionary processes with and without immunological pressure. Characterization of evolved strains assists in the development of predictive algorithms for both the selection of subtypes represented in the seasonal influenza vaccine and the design of novel immune refocused vaccines. To obtain data on the evolution of influenza in a controlled setting, naïve and immunized Guinea pigs were infected with influenza A/Wyoming/2003 (H3N2). Virus progeny from nasal wash samples were assessed for variation in the dominant and other epitopes by sequencing the hemagglutinin (HA) gene to quantify evolutionary changes. Viral RNA from the nasal washes from infection of naïve and immune animals contained 6% and 24.5% HA variant sequences, respectively. Analysis of mutations relative to antigenic epitopes indicated that adaptive immunity played a key role in virus evolution. HA mutations in immunized animals were associated with loss of glycosylation and changes in charge and hydrophobicity in and near residues within known epitopes. Four regions of HA-1 (75–85, 125–135, 165–170, 225–230) contained residues of highest variability. These sites are adjacent to or within known epitopes and appear to play an important role in antigenic variation. Recognition of the role of these sites during evolution will lead to a better understanding of the nature of evolution which help in the prediction of future strains for selection of seasonal vaccines and the design of novel vaccines intended to stimulated broadened cross-reactive protection to conserved sites outside of dominant epitopes

Afforestation neutralizes soil pH

Soil pH regulates soil biogeochemical processes and has cascading effects on terrestrial ecosystem structure and functions. Afforestation has been widely adopted to increase terrestrial carbon sequestration and enhance water and soil preservation. However, the effect of afforestation on soil pH is still poorly understood and inconclusive. Here we investigate the afforestation-caused soil pH changes with pairwise samplings from 549 afforested and 148 control plots in northern China. We find significant soil pH neutralization by afforestation-afforestation lowers pH in relatively alkaline soil but raises pH in relatively acid soil. The soil pH thresholds (TpH), the point when afforestation changes from increasing to decreasing soil pH, are species-specific, ranging from 5.5 (Pinus koraiensis) to 7.3 (Populus spp.) with a mean of 6.3. These findings indicate that afforestation can modify soil pH if tree species and initial pH are properly matched, which may potentially improve soil fertility and promote ecosystem productivity