Group A rotaviruses (RVAs) remain the leading cause of acute gastroenteritis (AGE) in young children in low- and middle-income countries. In Brazil, the oral attenuated RVA vaccine (Rotarix^®), monovalent genotype G1P[8], is distributed by the national immunization program and has drastically reduced morbidity and mortality associated with RVA etiology. In this study, Rotarix^® G1P[8] was detected using specific qRT-PCR from the fecal shedding of children living in the Amazon region, and 18.3% (29/158) were positive and 75.8% (22/29) presented with AGE. The VP4 (VP8*) gene of these sheddings, submitted to Sanger nucleotide sequencing, showed an occurrence of mutations, including the silent mutation at 144C > G (one child) and the following missense mutations— 499T > C (F167L) (two children), 644G > C (C215S) (one child), and 787G > A (E263K) (one child). These mutations had no impact on the protein model structure in silico deduced from the VP4 (VP8*) mutants. The in silico protein model deduced from the VP4 (VP8*) nucleotide sequences, bound to type 1H sugar antigens (H1) and its precursor Lac-para-N-biose (LNB), had a stronger binding to the G1P[8] genotype, when compared to G3P[8]. Rotarix^® shedding was higher in HBGA secretors than in non-secretors (79.3%; 23/29). A total of 11.4% (18/158) of children with Rotarix^® G1P[8] shedding were unvaccinated, indicating the occurrence of indirect protection. Stability evidence of Rotarix^® VP4 (VP8*) spike protein from samples collected in vivo is presented.

The introduction of rotavirus A (RVA) vaccines has considerably reduced the RVA-associated mortality among children under 5 years of age worldwide. The ability of RVA to reassort gives rise to different combinations of surface proteins G (glycoprotein, VP7) and P (protease sensitive, VP4) RVA types infecting children. During the epidemiological surveillance of RVA in the Northwest Amazon region, an unusual rotavirus genotype G6P[8] was detected in feces of a 2-year-old child with acute gastroenteritis (AGE) that had been vaccinated with one dose of Rotarix^® (RV1). The G6P[8] sample had a DS-1-like constellation with a Wa-like VP3 gene mono-reassortment similar to equine-like G3P[8] that has been frequently detected in Brazil previously. The results presented here reinforce the evolutionary dynamics of RVA and the importance of constant molecular surveillance.

Objectives : We assessed the prevalence and genetic diversity of human adenovirus in children up to five years old, with and without acute gastroenteritis, in the Amazon region during 2016, 2017, and 2021. Design : This cross-sectional study used fecal samples from children admitted to a hospital in Boa Vista, Roraima. The samples were tested for adenovirus using quantitative real-time PCR and further characterized by PCR and sequencing of three specific genes. Results : Out of 942 samples, 13% tested positive for adenovirus—12% in children with acute gastroenteritis and 15.6% in children without gastroenteritis. Genotyping revealed that species F and C were predominant in acute gastroenteritis cases, while species F and A were more common in non-acute cases. The study found significant temporal variations in prevalence, with the highest rates in 2016. Adenovirus D37 was detected for the first time in Brazil. Conclusions : The study highlighted the notable presence and diversity of adenovirus among children in the Amazon region, emphasizing the need for continuous monitoring.

COVID-19 infection caused by SARS-CoV-2 continues to cause significant mortality and morbidity. ACE2 is a key regulator of the renin–angiotensin–aldosterone system (RAAS). Differences in COVID-19 severity are thought to be due to the imbalance of RAAS/ACE mutations. This retrospective study evaluated the detection and genetic susceptibility to SARS-CoV-2 infection in 202 children ≤3 years of age living in the Amazon region in 2021. The angiotensin-converting enzyme ACE I/D (rs4646994) and ACE2 G8790A (rs2285666) polymorphisms were detected by SYBR GREEN real-time PCR and PCR-RFLP/Alul digestion, respectively. SARS-CoV-2 detection was performed by RT-qPCR in feces and saliva samples collected simultaneously from the same children presenting acute gastroenteritis (AGE) or acute respiratory infection (ARI). The frequency of SARS-CoV-2 detected by qRT-PCR in children was low (5.9%, 12/202), although higher in the group of children with AGE (8.9%, 9/101) than with ARI (2.9%, 3/101). Susceptibility to SARS-CoV-2 infection was not verified due to the low frequency. Homozygous II (rs4646994) children were the majority (87.1%, 176/202). Boys with genotype A (rs2285666) were more susceptible to ARI and pneumonia symptoms than AGE (OR = 3.8, 95% CI 1.4–10.3, p 0.007). Boys with genotype G (rs4646994) or the combination II + G were more susceptible to acquiring AGE. Surveillance, along with understanding their causes, is crucial to controlling ARI and COVID-19 in children living in low-income countries.

This study evaluated the epidemiological and genetic susceptibility profile caused by coronavirus 2 (SARS-CoV-2) in children ≤3 years of age with acute gastroenteritis (AGE) or acute respiratory infection (ARI), living in the northwestern region of the Amazon (NWAR). Fecal and saliva sam-ples collected from 202 children (n=404) were subjected to detection of SARS-CoV-2 by RT-qPCR. Polymorphisms in the angiotensin-converting enzyme (ACE rs4646994) and ACE2 G8780A; rs2285666) genes were detected by SYBR GREEN real-time PCR and PCR/Alul digestion, respec-tively. Secretory and Lewis status of histo-blood group antigen (HBGA) was performed using phenotyping/ELISA. Frequencies for the AGE group: SARS-CoV-2; 8.9%; ARI group: SARS-CoV-2; 2.9%. The ACE I/I homozygous polymorphism gene was majority. Males with the ACE2 G8780A SNP were more susceptible to ARI symptoms than AGE (OR = 3.85; 95% CI-1.42-10.38; P 0.007). Most children were secretory FUT2 phenotype (92.6%). Surveillance of diarrhea and respiratory infections in children, along with understanding their causes, are crucial for identifying preven-tion and control strategies and for prioritizing and developing new vaccines. Clinical manifesta-tions of COVID-19 in children ≤3 years of age include AGE.

Human populations are classified as secretors or non-secretors by, respectively, the ability to produce or not produce FUT2 enzyme (alpha-1,2-fucosyltransferase; FUT2 gene). Non-secretors have some protection against diseases and viral infections. Two single-nucleotide polymorphisms (SNPs), rs601338 (non-secretor; sese), and rs1047781 (weak secretor; Se^w), are known population markers. In this study, 68 saliva samples collected from children living in the Brazilian Amazon region were evaluated for zygosity—genotyping (homozygous or heterozygous) of the rs601338 and rs1047781 SNPs by pyrosequencing. Nine children were heterozygous (Sese) for the rs601338 SNP (13.2%; 9/68) and one homozygous (sese) (1.5%; 1/68). One child that was heterozygous for the rs601338 SNP was also heterozygous for the rs1047781 SNP (Se^w) (1.5%; 1/68). By using Sanger nucleotide sequencing of the FUT2 coding region, strongly linked SNPs (171A>G, 216C>T, 357T>C, 428G>A, 739G>A, 960A>G), including the FUT2*01N.02 allele (428G>A; 739A>G), were detected and have been associated with non-secretor children. A novel SNP (315C>T) and others (40A>G; 480C>T; 863C>T) detected in worldwide populations were also detected. The sensitivity of the pyrosequencing method provided an unprecedented discovery of the zygosity of the SNP rs1047781 only previously detected in East and Southeast Asians. The identification of novel SNPs in this population expands our knowledge of genetic susceptibility to viral infections.