Mucosal CD8+ T cell responses induced by an MCMV based vaccine vector confer protection against influenza challenge

Abstract

20Cytomegalovirus (CMV) is a ubiquitous β-herpesvirus that establishes life-long latent infection 21 in a high percentage of the population worldwide. CMV induces the strongest and most durable 22 CD8 + T cell response known in human clinical medicine. Due to its unique properties, the virus 23 represents a promising candidate vaccine vector for the induction of persistent cellular 24 immunity. To take advantage of this, we constructed a recombinant murine CMV (MCMV) 48 but only if we administered it through the nose, to activate killer T cells that will persist in the 49 lungs close to the airways. Therefore, our data show that the subset of lung-resident killer T 50 cells is sufficient to protect against influenza. 3 51 Introduction 52 Respiratory infections caused by influenza viruses usually are associated with mild-to-53 moderate disease symptoms but are linked with high morbidity and mortality in susceptible 54 populations like the elderly, young children, patients with co-morbidities and 55 immunocompromised patients. Influenza virus causes seasonal epidemics, with typically 3 to 56 5 million cases of severe illness worldwide, according to WHO reports [1], and influenza type 57 A viruses (IAV) cause the more severe disease form. Vaccines against influenza are based on 58 the induction of adaptive immunity that targets the projected yearly epidemics. While most 59 vaccines are based on inactivated IAV formulations inducing anti-IAV IgG responses, live 60 attenuated influenza vaccines (LAIV) are also used as formulations for i.n. administration. This 61 is based on the assumption that the induction of local immunity may provide superior immune 62 protection [2, 3]. However, it remains unclear whether this protection depends on local IgA 63 responses, on cytotoxic T cell responses, or on their combined antiviral activity. Of note, 64 functional T cell responses were shown to substantially contribute to antiviral IAV immunity [4-65 6]. In particular, cytotoxic influenza-specific CD8 + T lymphocytes (CTLs) promote viral 66 clearance indirectly by secretion of pro-inflammatory cytokines such as IFNγ [7] and directly 67 by perforin/Fas-mediated killing of infected epithelial cells in the bronchoalveolar space [8]. 68 However, it remained unclear if T cell responses alone may control IAV, or if Ig responses were 69 the crucial contributor to LAIV-mediated immune protection. We considered that this question 70 could be addressed by developing a vaccine formulation that optimizes T cell responses 71 against IAV, while excluding the humoral ones. 72 CMV infection induces sustained functional T cell responses that are stronger in the long-term 73 than the immune response to any other infectious pathogen [9]. Experiments in the mouse 74 model have shown that defined CMV epitope-specific CD8 + T cells accumulate in tissues and 75 blood and are maintained at stable high levels during mouse CMV (MCMV) latency [10]. This 76 phenomenon was termed ''Memory Inflation'' [11]. While some MCMV derived peptides, as the 77 ones de...

gB co‐immunization with GP96 enhances pulmonary‐resident CD8 T cells and exerts a long‐term defence against MCMV pneumonitis

“…To further confirm that the long‐lasting protection depends on lung‐resident CD8 T cells, in pgB/pGP96‐NT co‐immunization group, 16 weeks after the last immunization, we performed site‐specific depletion of total pulmonary mucosal CD8 T cells by i.n . administration with αCD8 Ab or isotype control Ab 3 days and 1 day prior to MCMV challenge as previously reported 26,27 (depletion efficiency was shown in Figure ). 7 days post‐infection, the severity of pneumonitis, weight loss and viral burdens were evaluated.…”

“…IVCD45 ‐ CD8 T RM (CD69 + CD103 + ) cells were enhanced in the lung (Figure 6A), and the proportion and number of this population was significantly higher in pgB/pGP96‐NT co‐immunized mice compared to those in pgB‐immunized mice (Figure 6B,C). However, CD69 and CD103 were not enough to identify CD8 T RM cells, and CD8 T RM cells were also known to express lower level of eomesodermin (Eomes) compared to classic T cells 27 . We further validated our finding by detecting Eomes expression in CD69 + CD103 + and CD69 + CD103 − subsets.…”

“…In accordance with our hypothesis, data reflected that increased CD69 + CD103 + CD8 T‐cell population in lung (Figure 6A), which might be converted into pulmonary‐resident effector CD8 T cells that exhibited CTL activity (Figure 5G). Site‐specific anti‐CD8 antibody administration depleted CD8 T RM which aggravated influenza challenge by a MCMV‐based vaccine 27 . The majority (>90%) of the Ag‐specific T cells would die 4 months after the last immunization, while the rest would differentiate into memory T cells 60 .…”

“…To specifically deplete mucosal CD8 T cells in the lung, according to published protocol, 26,27 mice were i.n. administered 10 μg αCD8 (clone2.43) or IgG2b (LTF-2) in 20 μl of PBS −3 day and −1 day following MCMV challenge.…”

Harnessing Cross-Reactive CD8+TRMCells for Long-Standing Protection Against Influenza A Virus

“…Inflation, the concept that a small amount of persistent antigen can stimulate a T cell population without causing T cell exhaustion, has recently been gaining substantial attention and also how inflation can maintain the T RM population in the lungs and airways (6). Except for adenovectors, intranasal vaccination with Murin Cytomegalovirus (MCMV) vectors has recently been explored as a method for generating and maintaining a T RM population by inflation long term (37,38,59). However, as discussed earlier, cells in the lung and particularly the airways have a high rate of apoptosis and the time limit of the inflation process and the effect on the T RM population long term in the lungs has not been thoroughly studied.…”