STL polyomavirus

STL polyomavirus (STLPyV, also known as Saint Louis polyomavirus or Human polyomavirus 11) is a virus of the polyomavirus family that infects human hosts. It was first reported in 2013 and is most closely related to MW polyomavirus.^[1] It has been identified mostly in stool samples from children and has been detected in a variety of geographic locations.^[2]

STL polyomavirus
Virus classification
(unranked):	Virus
Realm:	Monodnaviria
Kingdom:	Shotokuvirae
Phylum:	Cossaviricota
Class:	Papovaviricetes
Order:	Sepolyvirales
Family:	Polyomaviridae
Genus:	Deltapolyomavirus
Species:	Deltapolyomavirus undecihominis
Synonyms
Human polyomavirus 11

Discovery

STL polyomavirus was first discovered in 2013 in a stool sample from a healthy child in Malawi; the same research group then detected the virus in stool from children in The Gambia and Saint Louis, Missouri (after which the virus was named).^[1] The designation "STL polyomavirus" was included in the International Committee on Taxonomy of Viruses proposed classification of polyomaviruses. It was the 11th human polyomavirus to be discovered.^[3]

Genome

The organization of the STLPyV genome is typical of polyomaviruses. At around 4.8 kilobase pairs in length, it contains genes for the small tumor antigen and large tumor antigen, a novel additional tumor antigen, and three viral coat proteins, VP1, VP2, and VP3.^[1] It is most closely related to MW polyomavirus, also first isolated from a child in Malawi.^[4] Different STLPyV isolates have a relatively large amount of sequence variation, up to approximately 5%; this pattern is similar to both MWPyV and the much better characterized BK polyomavirus.^[1][4][5]

A distinctive characteristic of the STLPyV genome is its alternatively spliced tumor antigen; in addition to the small and large tumor antigens highly conserved in polyomaviruses, STLPyV also expresses a third tumor antigen designated 229T, which contains a novel fusion of portions of the small and large tumor antigen sequences.^[1]

Taxonomy

Among the human polyomaviruses, STLPyV is most closely related to MWPyV; like MWPyV, its genome suggests different ancestries for the large tumor antigen and the major capsid protein VP1, implying that the virus might have evolved from an ancestral recombination event.^[1][4]

In the 2015 taxonomic update to the polyomavirus group, the International Committee on Taxonomy of Viruses classified STLPyV in the genus Deltapolyomavirus. This genus contains four viruses that infect humans: HPyV6, HPyV7, MW polyomavirus, and STL polyomavirus.^[3]

Prevalence

All known human polyomaviruses are fairly common in healthy adult populations and are usually asymptomatic. In a study that profiled polyomavirus seroprevalence, or prevalence of detectable antibodies against viral proteins indicating either past or present exposure in immunocompetent adults, the estimate of STLPyV prevalence was approximately 70%, with an age distribution consistent with transmission of maternal antibodies combined with early childhood infection.^[6] Studies of the presence of viral DNA, indicating active viral replication, suggest STLPyV prevalence in the range of 1-2% of children.^[1][2][7]