Human cytomegalovirus (HCMV) is the most common congenital infection. Several HCMV vaccines are in development, but none have yet been approved. An understanding of the kinetics of CMV replication and transmission may inform the rational design of vaccines to prevent this infection. The salivary glands (SG) are an important site of sustained CMV replication following primary infection and during viral reactivation from latency. As such, the strength of the immune response in the SG likely influences viral dissemination within and between hosts. To study the relationship between the immune response and viral replication in the SG, and viral dissemination from the SG to other tissues, mice were infected with low doses of murine CMV (MCMV). Following intra-SG inoculation, we characterized the viral and immunological dynamics in the SG, blood, and spleen, and identified organ-specific immune correlates of protection. Using these data, we constructed compartmental mathematical models of MCMV infection. Model fitting to data and analysis indicate the importance of cellular immune responses in different organs and point to a threshold of infection within the SG necessary for the establishment and spread of infection.
Copyright: © 2024 Byrne et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Human cytomegalovirus (HCMV) is the most common congenital infection. Several HCMV vaccines are in development, but none have yet been approved. An understanding of the kinetics of CMV replication and transmission may inform the rational design of vaccines to prevent this infection. The salivary glands (SG) are an important site of sustained CMV replication following primary infection and during viral reactivation from latency. As such, the strength of the immune response in the SG likely influences viral dissemination within and between hosts. To study the relationship between the immune response and viral replication in the SG, and viral dissemination from the SG to other tissues, mice were infected with low doses of murine CMV (MCMV). Following intra-SG inoculation, we characterized the viral and immunological dynamics in the SG, blood, and spleen, and identified organ-specific immune correlates of protection. Using these data, we constructed compartmental mathematical models of MCMV infection. Model fitting to data and analysis indicate the importance of cellular immune responses in different organs and point to a threshold of infection within the SG necessary for the establishment and spread of infection. Author Summary Cytomegalovirus (CMV) is the most common congenital infection and causes an enormous burden of childhood disease. To gain insight into the immune requirements for controlling infection, we used a mouse model to reproduce characteristics of natural CMV infection, employing a low viral inoculum, and delivering the virus to the salivary glands (SG), a key site of CMV replication. Our results provide detailed data on the spatial and temporal spread of infection throughout the body and identify key immune correlates of the control of viral replication. By translating these findings into mechanistic mathematical models, we revealed the importance of organ-specific immune responses, particularly the requirement of TNF- α and IFN- γ to control infection within the salivary glands. Furthermore, our mathematical modeling allowed us to compare known characteristics of human CMV infection related to infection establishment and spread to those predicted in mice, underscoring the suitability of the MCMV model to study its human homologue. These insights provide guidance for developing targeted vaccines to prevent CMV infection and disease.

This study explored the effects of Chenopodium quinoa's ingredients on the major lipids' hepatic profile and the functional selective differentiation of monocyte-derived macrophages and innate lymphoid cells in mice on a high-fat diet. Six-week-old Rag2-/- and Rag2-/-Il2-/- mice received (12 days) a low-molecular-weight protein fraction (LWPF) or the lipid fraction (qLF) obtained from the cold pressing of C. quinoa's germen. At the end of the experiment, mouse serum and liver tissue were collected. The differences in triglycerides, phospholipids, and the major lipids profile were analyzed. Infiltrated monocyte-derived macrophages and innate lymphoid cells (ILCs) and the expression of liver metabolic stress-related mRNA were measured. In the Rag2-/- mice, feeding them LWPF appeared to improve, to a larger extent, their hepatic capacity to utilize fatty acids in comparison to the qLF by preventing the overwhelming of triglycerides (TGs), despite both reducing the hepatic lipid accumulation. An analysis of the hepatic major lipids profile revealed significant increased variations in the PUFAs and phospholipid composition in the Rag2-/- mice fed with the LWPF or LF. The Rag2-/-Il2-/- mice, lacking innate and adaptive lymphocytes, seemed resistant to mobilizing hepatic TGs and unresponsive to lipid accumulation when fed with the LF. Notably, only the Rag2-/- mice fed with the LWPF showed an increased proportion of hepatic CD68+F4/80+ cells population, with a better controlled expression of the innate immune 'Toll-like' receptor (TLR)-4. These changes were associated with an oriented expansion of pluripotential CD117+ cells towards ILC2s (CD117+KLRG1+). Thus, C. quinoa's ingredients resulted in being advantageous for improving the mechanisms for controlling the hepatic lipotoxicity derived from a high-fat diet, promoting liver macrophage and ILCs expansion to a selective functional differentiation for the control of HFD-driven immune and metabolic disturbances.

Cytomegalovirus (CMV) establishes a lifelong infection facilitated, in part, by circumventing immune defenses mediated by tumor necrosis factor (TNF)-family cytokines. An example of this is the mouse CMV (MCMV) m166 protein, which restricts expression of the TNF-related apoptosis-inducing ligand (TRAIL) death receptors, promoting early-phase replication. We show here that replication of an MCMV mutant lacking m166 is also severely attenuated during viral persistence in the salivary glands (SG). Depleting group I innate lymphoid cells (ILCs) or infecting Trail-/- mice completely restored persistent replication of this mutant. Group I ILCs are comprised of two subsets, conventional natural killer cells (cNK) and tissue-resident cells often referred to as innate lymphoid type I cells (ILC1). Using recently identified phenotypic markers to discriminate between these two cell types, their relative expression of TRAIL and gamma interferon (IFN-γ) was assessed during both early and persistent infection. ILC1 were found to be the major TRAIL expressers during both of these infection phases, with cNK expressing very little, indicating that it is ILC1 that curtail replication via TRAIL in the absence of m166-imposed countermeasures. Notably, despite high TRAIL expression by SG-resident ILC1, IFN-γ production by both ILC1 and cNK was minimal at this site of viral persistence. Together these results highlight TRAIL as a key ILC1-utilized effector molecule that can operate in defense against persistent infection at times when other innate control mechanisms may be muted and highlight the importance for the evolution of virus-employed countermeasures.IMPORTANCE Cytomegalovirus (a betaherpesvirus) is a master at manipulating immune responses to promote its lifelong persistence, a result of millions of years of coevolution with its host. Using a one-of-a-kind MCMV mutant unable to restrict expression of the TNF-related apoptosis-inducing ligand death receptors (TRAIL-DR), we show that TRAIL-DR signaling significantly restricts both early and persistent viral replication. Our results also reveal that these defenses are employed by TRAIL-expressing innate lymphoid type I cells (ILC1) but not conventional NK cells. Overall, our results are significant because they show the key importance of viral counterstrategies specifically neutralizing TRAIL effector functions mediated by a specific, tissue-resident subset of group I ILCs.
Copyright © 2019 American Society for Microbiology.