Viral infections, particularly human norovirus (NoV), are a leading cause of diarrheal diseases globally. To better understand NoV susceptibility, it is crucial to investigate both host glycobiology and the influence of the microbiota. Histo-blood group antigens (HBGA) displayed on surfaces of host cells act as NoV receptors, while certain bacteria express HBGA-like substances, facilitating virus-bacteria interactions. To identify bacterial species interacting with NoV during infection, stool samples from children infected with NoV GII.4 were analyzed. The samples were subjected to bacteria separation using anti-NoV GII.4 polyclonal antibodies coupled to magnetic beads, followed by microbiota profiling through 16S rDNA sequencing. This approach identified the genus Rhodococcus as enriched in samples captured with anti-NoV antibodies compared to controls. Electron microscopy confirmed the binding of NoV GII.4 Sydney 2012 viral-like particles (VLP) to five Rhodococcus strains from different species, which expressed HBGA-like substances on their surfaces, particularly from A and B blood groups. In human intestinal enteroids, Rhodococcus erythropolis reduced NoV GII.4 Sydney 2012 infection levels under displacement, exclusion and competitive exclusion settings. Extracellular polysaccharides (EPS) isolated from Rhodococcus strains bound VLP from both GII.4 and GII.6 genotypes. Blocking antibodies targeting A and B epitopes reduced the binding of the EPS from R. erythropolis to GII.6 VLP, while enhanced binding to GII.4 VLP was observed when A and B epitopes were blocked. These findings revealed the interaction of Rhodococcus to NoV in an in vitro setting and open new avenues for developing innovative antiviral strategies to prevent and treat NoV infections through the HBGA-like substances present in their EPS.

Rotavirus (RV) is the leading cause of acute gastroenteritis (AGE) in children under 5 years old worldwide, and several studies have demonstrated that histo–blood group antigens (HBGAs) play a role in its infection process. In the present study, human stool filtrates from patients diagnosed with RV diarrhea (genotyped as P[8]) were used to infect differentiated Caco-2 cells (dCaco-2) to determine whether such viral strains of clinical origin had the ability to replicate in cell cultures displaying HBGAs. The cell culture-adapted human RV Wa model strain (P[8] genotype) was used as a control. A time-course analysis of infection was conducted in dCaco-2 at 1, 24, 48, 72, and 96 h. The replication of two selected clinical isolates and Wa was further assayed in MA104, undifferentiated Caco-2 (uCaco-2), HT29, and HT29-M6 cells, as well as in monolayers of differentiated human intestinal enteroids (HIEs). The results showed that the culture-adapted Wa strain replicated more efficiently in MA104 cells than other utilized cell types. In contrast, clinical virus isolates replicated more efficiently in dCaco-2 cells and HIEs. Furthermore, through surface plasmon resonance analysis of the interaction between the RV spike protein (VP8*) and its glycan receptor (the H antigen), the V7 RV clinical isolate showed 45 times better affinity compared to VP8* from the Wa strain. These findings support the hypothesis that the differences in virus tropism between clinical virus isolates and RV Wa could be a consequence of the different HBGA contents on the surface of the cell lines employed. dCaco-2, HT29, and HT29M6 cells and HIEs display HBGAs on their surfaces, whereas MA104 and uCaco-2 cells do not. These results indicate the relevance of using non-cell culture-adapted human RV to investigate the replication of rotavirus in relevant infection models.

Rotavirus remains a significant public health threat, especially in low-income countries, where it is the leading cause of severe acute childhood gastroenteritis, contributing to over 128,500 deaths annually. Although the introduction of the Rotarix and RotaTeq vaccines in 2006 marked a milestone in reducing mortality rates, approximately 83,158 preventable deaths persisted, showing ongoing challenges in vaccine accessibility and effectiveness. To address these issues, a novel subcutaneous vaccine formulation targeting multiple rotavirus genotypes has been developed. This vaccine consists of nine VP8* proteins from nine distinct rotavirus genotypes and sub-genotypes (P[4], P[6], P[8]_LI, P[8]_LIII, P[8]_LIV, P[9], P[11], P[14], and P[25]) expressed in E. coli. Two groups of mice were immunized either with a single immunogen, the VP8* from the rotavirus Wa strain (P[8]_LI), or with the nonavalent formulation. Preliminary results from mouse immunization studies showed promising outcomes, eliciting antibody responses against six of the nine immunogens. Notably, significantly higher antibody titers against VP8* P[8]_LI were observed in the group immunized with the nonavalent vaccine compared to mice specifically immunized against this genotype alone. Overall, the development of parenteral vaccines targeting multiple rotavirus genotypes represents a promising strategy in mitigating the global burden of rotavirus-related morbidity and mortality, offering new avenues for disease prevention and control.

Species A rotavirus (RVA) is a major cause of acute gastroenteritis in children. However, three other rotavirus species (RVB, RVC, and RVH) are also able to infect humans. It has been suggested that vaccination against RVA could facilitate an increase of non‐A rotavirus infections. We investigated the antibody prevalence against RVA, RVB, RVC, and RVH in 420 human sera collected between 2020 and 2022 from different age groups in Valencia (Spain). Antibody prevalence rates to RVA, RVB, RVC, and RVH were 79.3%, 17.9%, 18.8%, and 14.5%, respectively. Antibody titers against RVA remained consistent across the different age groups, and RVB showed low titers except in younger individuals. RVC‐specific antibodies peaked in children 5–10 years of age, whereas RVH exhibited the highest titers in the elderly. The detection of antibodies against non‐A rotaviruses in humans in Spain, for the first time against RVB and RVH, highlights the need for their surveillance.