Comparison of Geographic Variation of CMV Glycoprotein B Between Minnesotan and Ugandan Populations
Autumn Kittilson, Nelmary Hernandez-Alvarado, Emma Anghel, Claudia Fernandez-Alarcon, Mark Blackstad, Caleb Skipper, Mark R SchleissAbstract
Background
Cytomegalovirus (CMV) is a common opportunistic viral infection in immunocompromised patients and the most common intrauterine infection. Congenital CMV is the leading infectious cause of pediatric disability, including sensorineural hearing loss. Glycoprotein B (gB), a surface protein of CMV, facilitates viral entry into host cells and is a driver of immune response by eliciting production of host neutralizing antibodies. Because of this, gB is a target of interest for CMV vaccine studies. CMV vaccines have only been tested in the US and Europe, despite CMV affecting populations globally. We compared the distribution of circulating gB genotypes in de-identified samples from Uganda and Minnesota to determine if there is significant geographic variation in gB genotypes.
Methods
The two populations we compared were based on de-identified samples obtained from pediatric studies in Minnesota and from individuals living with AIDS in Uganda with confirmed CMV viremia. Extracted CMV DNA was subjected to PCR amplification targeting a 265 bp region of the UL55 (gB) gene. PCR amplicons were screened for presence of UL55 via agarose gel electrophoresis. The DNA sequences of PCR positive samples were obtained via Sanger sequencing. The nucleotide sequences were translated into amino acid sequences which were then aligned via a clustal-omega algorithm. Genotypes were then assigned by constructing a phylogenetic tree from the protein alignment with known gB genotype sequences (gB1-5) serving as controls.
Results
In total, 46 sequences from the Minnesotan group and 65 sequences from the Ugandan group were analyzed. The Minnesotan strains were comprised of 35% gB1, 22% gB2, 37% gB3, 4% gB4, and 2% gB5 genotypes. The distribution of genotypes in the Ugandan group was 25% gB1, 55% gB2, 18% gB3, and 2% gB4. The gB5 genotype was not present in the Ugandan group. Between the two groups, we found a significant difference in the circulating genotypes gB2 (p=0.0004), which was more prevalent in Ugandan strains, and gB3 (p= 0.047), which was more prevalent in Minnesotan strains.
Conclusion
The differences in genotype distribution between these two groups suggests that there may be global differences in circulating CMV strains. This is significant for global health efforts in controlling CMV, particularly for tailoring responses to CMV gB subunit vaccines which are based on the protein sequence of a single strain. Further investigation will be required to determine whether sequence variations reflect geographic variability, difference in susceptibility based on age or underlying conditions, or both.