To better understand how CMV evolves in fetuses and newborns during symptomatic congenital infection, researchers at UMMS and the University of Minnesota Medical School collected samples from the plasma and urine of five congenitally infected infants during the first year after birth. Using next generation DNA sequencing, Kowalik and colleagues studied the diversity and changes in viral DNA sequences over time and between organs. Though the DNA sequences from viruses taken from the same type of sample (e.g. plasma) were similar to each other, the study's authors found dramatic differences between the sequences collected from viruses in the plasma and urine of the same infant. Surprisingly, the plasma and urine sequences from the same infant were as different as sequences from two unrelated infants.
These results suggest that CMV is able to evolve very quickly as the differences between the plasma and urine sequences likely occurred in the short period between the initial, in utero infection, and the first year after birth. However, the mechanism driving this phenomenon remained unclear.
To answer this question, researchers used mathematical modeling and statistical inference to uncover evidence that population bottlenecks and expansions may play a significant role in the virus' evolution after infection. Characterized by a substantial reduction in viral copies followed by a quick rebound, population bottlenecks and expansions can lead to dramatic changes in DNA sequences that result in two related populations quickly becoming dissimilar. In the case of CMV infection, this phenomenon appeared to coincide with the virus moving from the mother to the fetus and later migrating from the plasma to the kidneys.
The model also suggests that the timing of initial fetal infection in the patients was at 13 to 18 weeks gestati
|Contact: Jim Fessenden|
University of Massachusetts Medical School