Hematopoietic cell-mediated dissemination of murine cytomegalovirus is regulated by NK cells and immune evasion

Abstract

Cytomegalovirus (CMV) causes clinically important diseases in immune compromised and immune immature individuals. Based largely on work in the mouse model of murine (M)CMV, there is a consensus that myeloid cells are important for disseminating CMV from the site of infection. In theory, such dissemination should expose CMV to cell-mediated immunity and thus necessitate evasion of T cells and NK cells. However, this hypothesis remains untested. We constructed a recombinant MCMV encoding target sites for the hematopoietic specific miRNA miR-142-3p in the essential viral gene IE3. This virus disseminated poorly to the salivary gland following intranasal or footpad infections but not following intraperitoneal infection in C57BL/6 mice, demonstrating that dissemination by hematopoietic cells is essential for specific routes of infection. Remarkably, depletion of NK cells or T cells restored dissemination of this virus in C57BL/6 mice after intranasal infection, while dissemination occurred normally in BALB/c mice, which lack strong NK cell control of MCMV. These data show that cell-mediated immunity is responsible for restricting MCMV to hematopoietic cell-mediated dissemination. Infected hematopoietic cells avoided cell-mediated immunity via three immune evasion genes that modulate class I MHC and NKG2D ligands (m04, m06 and m152). MCMV lacking these 3 genes spread poorly to the salivary gland unless NK cells were depleted, but also failed to replicate persistently in either the nasal mucosa or salivary gland unless CD8+ T cells were depleted. Surprisingly, CD8+ T cells primed after intranasal infection required CD4+ T cell help to expand and become functional. Together, our data suggest that MCMV can use both hematopoietic cell-dependent and -independent means of dissemination after intranasal infection and that cell mediated immune responses restrict dissemination to infected hematopoietic cells, which are protected from NK cells during dissemination by viral immune evasion. In contrast, viral replication within mucosal tissues depends on evasion of T cells.

Multiple Autonomous Cell Death Suppression Strategies Ensure Cytomegalovirus Fitness

“…The genomic integrity of double mutants and control viruses were confirmed by direct evaluation ( Figure S1A ), as previously shown for single mutant viruses [ 29 , 30 , 38 ]. MCMV was shed in saliva mediates horizontal transmission [ 88 ], so viral load in these glands may therefore be considered an indicator of viral fitness. MCMV detection in salivary glands requires entry followed by replication in cells at the origin of infection, myeloid-cell mediated dissemination to different tissues including the salivary glands, and ultimate replication salivary glands [ 88 , 89 , 90 , 91 , 92 , 93 ].…”

“…MCMV was shed in saliva mediates horizontal transmission [88], so viral load in these glands may therefore be considered an indicator of viral fitness. MCMV detection in salivary glands requires entry followed by replication in cells at the origin of infection, myeloid-cell mediated dissemination to different tissues including the salivary glands, and ultimate replication salivary glands [88][89][90][91][92][93]. Virus-encoded modulators of adaptive and innate immunity (including cell death suppressors) suppress host defense to influence infection at different stages in dissemination [30,93,94].…”

New intranasal and injectable gene therapy for healthy life extension

“…CMV's large genome accommodates nearly 75% dispensable genes, many involved in immune evasion mechanisms that protect it from aggressive viral clearance responses regardless of route of entry. Olfactory infection spreads through dendritic cells, which migrate to lymph nodes and then extravasate into the bloodstream, whereas IP inoculation is expected to engage a wider range of myeloid progenitor cells, which in turn dictates viral dissemination and immune response outcomes (38).…”

“…This result exceeds the longevity achieved with a single dose of AVV9-TERT in the same animal model (13-24% when delivered in a single dose at 2 and 1 year old mice, respectively) (7). Interestingly, CMV therapy was equally effective regardless of route of inoculation, although the mechanism of dissemination differs, suggesting that expression of the therapeutic load is not substantially affected by the vector's interaction with the immune system (37) (38).…”

Comparability of CMV DNA Extraction Methods and Validation of Viral Load

“…The family of the Herpesviridae, such as human cytomegalovirus (HCMV), Epstein–Barr virus (EBV), and BK virus (BKV) are among the most common viral infections after allogeneic transplantation [ 2 ]. Particularly, HCMV infection most commonly occurs through reactivation of a latent infection enabled by impaired T-cell-mediated immunity and phagocytic function [ 3 ]. Clinical manifestations can range from mild to severe life-threatening diseases [ 4 ] and can present as a non-specific systemic viral disease [ 5 ] or a localized tissue-invasive infection, most commonly including pneumonia [ 6 ], hepatitis [ 7 ], colitis [ 8 ], and retinitis [ 9 , 10 ].…”