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The dynamics of SARS-CoV-2 replication and shedding in humans remain poorly understood. We captured the dynamics of infectious virus and viral RNA shedding during acute infection through daily longitudinal sampling of 60 individuals for up to 14 days. By fitting mechanistic models, we directly estimated viral expansion and clearance rates and overall infectiousness for each individual. Significant person-to-person variation in infectious virus shedding suggests that individual-level heterogeneity in viral dynamics contributes to 'superspreading'. Viral genome loads often peaked days earlier in saliva than in nasal swabs, indicating strong tissue compartmentalization and suggesting that saliva may serve as a superior sampling site for early detection of infection. Viral loads and clearance kinetics of Alpha (B.1.1.7) and previously circulating non-variant-of-concern viruses were mostly indistinguishable, indicating that the enhanced transmissibility of this variant cannot be explained simply by higher viral loads or delayed clearance. These results provide a high-resolution portrait of SARS-CoV-2 infection dynamics and implicate individual-level heterogeneity in infectiousness in superspreading.

Fermented milk products produced with probiotic lactic acid bacteria (LAB) have attracted interest due to their potential health benefits. Probiotic bacteria have a range of immunomodulatory activity, interacting with a variety of cell types in the immune system. Interactions with intestinal epithelial cells (IEC) are an avenue through which probiotics and their fermented milks can influence production of key immunoregulatory molecules, including cytokines and eicosanoids. The eicosanoids, which include the prostaglandins (PGs), are lipid mediators implicated in both acute and chronic inflammatory processes. The primary objective of this study was to determine the ability of probiotic LAB and their ferments to interact with IEC and influence their eicosanoid production. Effects of LAB and their milk ferments on prostaglandin E 2 (PGE 2 ) and prostaglandin F 2α (PGF 2α )production by human IEC lines were determined using a competitive enzyme immunoassay. LAB alone did not alter interleukin (IL)-1β-induced prostaglandin production by IEC. However, milk fermented with Lactobacillus (L.) rhamnosus strain R0011 significantly suppressed IL-1β-induced levels of PGE 2 and PGF 2α , an effect which was counteracted by the addition of strain R0011. Milk ferments prepared with L acidophilus strain R0052 were less effective in down-regulation of PG production by IEC. Naltrexone, an opioid receptor antagonist, blocked the suppressive effects of L rhamnosus R0011 milk ferments on PGF 2α production by IEC, suggesting that the bioactivity the ferments is opioid receptor-mediated. These findings support immunomodulatory potential of fermented food components through interactions with intestinal epithelial cells.

As a participant in the mucosal immune response, the intestinal epithelial cell must respond to a variety of stimuli, including lactic acid bacteria (LAB) consumed in the diet. The objective of this study was to compare the abilities of several strains of LAB to modulate cytokine secretion by human intestinal epithelial cell (IEC) line HT-29. Certain strains of Lactobacillus rhamnosus, Lactobacillus delbrueckii, and Lactobacillus acidophilus suppressed the production of the chemokine RANTES by stimulated HT-29 IEC, although the magnitude of this suppression varied depending on the nature of the bacterial growth medium. Similarly, specific strains showed growth condition-dependent suppression of HT-29 interleukin-8 (IL-8) production. Strain-dependent effects were also seen for the suppression of tumor necrosis factor alpha (TNF-alpha) and transforming growth factor beta (TGF-beta) production. The binding of several of these bacterial strains to the HT-29 cell line was also examined. Different strains were found to have differing abilities to interact with IEC, with L. rhamnosus R0011 being the strain that generally had the most extensive effects on HT-29 cytokine production and also bound to HT-29 IEC most effectively. Modulation of IEC cytokine production has the potential to profoundly affect the mucosal microenvironment, influencing the immune response to pathogens and other ingested antigens.

We have identified three novel, rarely expressed human genes that encode new members of the lipid transfer/lipopolysaccharide binding protein (LT/LBP) gene family based on sequence homology. BPI and other members of the LT/LBP family are structurally related proteins capable of binding phospholipids and lipopolysaccharides. Real-time PCR studies indicate that BPIL1 and BPIL3 are highly expressed in hypertrophic tonsils. In situ hybridization analysis of BPIL2 shows prominent expression in skin specimens from psoriasis patients. BPIL1 and BPIL3 map to Chromosome 20q11; thus, these novel genes form a cluster with BPI and two other members of the LT/LBP gene family on the long arm of human Chr 20. BPIL2 maps to Chr 22q13. The exon/intron organization of all three genes is highly conserved with that of BPI, suggesting evolution from a common ancestor.

Intestinal epithelial cells (IECs) act as a key point of initial contact with bacteria in the microenvironment of the intestinal tract. Interactions between IECs and bacteria lead to alterations in IEC activity, including modified cytokine secretion patterns, which may influence the mucosal immune response. IECs respond to lipopolysaccharide (LPS) from gramnegative bacteria by production of pro-inflammatory cytokines, including interleukin-8 (IL-8). Two strains of Lactobacillus rhamnosus , R0011 and R0049, were able to down-regulate LPS-induced IL-8 production by the human IEC line HT-29. Similar results were seen with KATO III gastric epithelial cells, suggesting a possible route for anti-inflammatory actions by L. rhamnosus . To further explore potential interactions in the gastrointestinal mucosal microenvironment, the effects of the neuropeptide vasoactive intestinal peptide (VIP) on the actions of L. rhamnosus R0011 were examined. VIP blocked the ability of this strain to down-regulate both constitutive and LPS-induced IL-8 production, suggesting that interactions between lactic acid bacteria (LAB) and IECs can be influenced by neuropeptides released into intestinal tissues. High levels of protein kinase A (PKA) and protein kinase C (PKC) activation rendered IEC refractory to the down-regulatory effects of L. rhamnosus on IL-8 production. L. rhamnosus R0011 induces moderate elevation of intracellular cAMP levels, indicating that its actions may, at least in part, be mediated through this signalling pathway in IECs. Key words: interleukin-8, vasoactive intestinal peptide, lactobacilli, probiotics, intestinal epithelial cell