Early-Life Colonization by Anelloviruses in Infants

Abstract

Anelloviruses (AVs) are found in the vast majority of the human population and are most probably part of a healthy virome. These viruses infect humans in the early stage of life, however, the characteristics of the first colonizing AVs are still unknown. We screened a collection of 107 blood samples from children between 0.4 and 64.8 months of age for the presence of three AV genera: the Alpha-, Beta- and Gammatorquevirus. The youngest child that was positive for AV was 1.2 months old, and a peak in prevalence (100% of samples positive) was reached between the twelfth and eighteenth months of life. Intriguingly, the beta- and gammatorqueviruses were detected most at the early stage of life (up to 12 months), whereas alphatorqueviruses, the most common AVs in adults, increased in prevalence in children older than 12 months. To determine whether that order of colonization may be related to oral transmission and unequal presence of AV genera in breast milk, we examined 63 breast milk samples. Thirty-two percent of the breast milk samples were positive in a qPCR detecting beta- and gammatorqueviruses, while alphatorqueviruses were detected in 10% of the samples, and this difference was significant (p = 0.00654). In conclusion, we show that beta- and gammatorqueviruses colonize humans in the first months of life and that breastfeeding could play a role in AV transmission.

Keywords: Anelloviridae; alphatorquevirus; anelloviruses; betatorquevirus; breast milk; early-life infections; gammatorquevirus; mother-to-child transmission.

Figure 1

Anellovirus concentration in the children’s blood over months. (A) Anellovirus concentration in the first 12 months of life and (B) anellovirus concentration in children aged 12 months until 65 months. All samples are arranged in the order of children’s age and the age of 6 months is depicted with a vertical line. The samples under the horizontal line were either negative for the viruses, or samples contained concentrations below the cutoff. Filled black dots represent alphatorquevirus white dots betatorqueviruses, and gray dots gamma- or betatorqueviruses.

Figure 2

Anellovirus concentration in breast milk. All samples are arranged in the order of children’s age at the moment of the breast milk collection. The samples under the horizontal line were either negative for the viruses, or samples contained concentrations below the cutoff. Filled black dots represent alphatorqueviruses, white dots betatorqueviruses, and gray dots gamma- or betatorqueviruses.