During human and murine cytomegalovirus (MCMV) infection an exceptionally large virus-specific CD8 T cell pool is maintained in the periphery lifelong. This anomalous response is only seen for ...specific subsets of MCMV-specific CD8 T cells which are referred to as 'inflationary T cells'. How memory CD8 T cell inflation is induced and maintained is unclear, though their activated phenotype strongly suggests an involvement of persistent antigen encounter during MCMV latency. To dissect the cellular and molecular requirements for memory CD8 T cell inflation, we have generated a transgenic mouse expressing an MHC class I-restricted T cell receptor specific for an immunodominant inflationary epitope of MCMV. Through a series of adoptive transfer experiments we found that memory inflation was completely dependent on antigen presentation by non-hematopoietic cells, which are also the predominant site of MCMV latency. In particular, non-hematopoietic cells selectively induced robust proliferation of inflationary CD8 T cells in lymph nodes, where a majority of the inflationary CD8 T cells exhibit a central-memory phenotype, but not in peripheral tissues, where terminally differentiated inflationary T cells accumulate. These results indicate that continuous restimulation of central memory CD8 T cells in the lymph nodes by infected non-hematopoietic cells ensures the maintenance of a functional effector CD8 T pool in the periphery, providing protection against viral reactivation events.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Helicobacter pylori infection causes chronic active gastritis that after many years of infection can develop into peptic ulceration or gastric adenocarcinoma. The bacterium is highly adapted to ...surviving in the gastric environment and a key adaptation is the virulence factor urease. Although widely postulated, the requirement of urease expression for persistent infection has not been elucidated experimentally as conventional urease knockout mutants are incapable of colonization. To overcome this constraint, conditional H. pylori urease mutants were constructed by adapting the tetracycline inducible expression system that enabled changing the urease phenotype of the bacteria during established infection. Through tight regulation we demonstrate that urease expression is not only required for establishing initial colonization but also for maintaining chronic infection. Furthermore, successful isolation of tet-escape mutants from a late infection time point revealed the strong selective pressure on this gastric pathogen to continuously express urease in order to maintain chronic infection. In addition to mutations in the conditional gene expression system, escape mutants were found to harbor changes in other genes including the alternative RNA polymerase sigma factor, fliA, highlighting the genetic plasticity of H. pylori to adapt to a changing niche. The tet-system described here opens up opportunities to studying genes involved in the chronic stage of H. pylori infection to gain insight into bacterial mechanisms promoting immune escape and life-long infection. Furthermore, this genetic tool also allows for a new avenue of inquiry into understanding the importance of various virulence determinants in a changing biological environment when the bacterium is put under duress.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Priming of CD8+ T cells specific for viruses that interfere with the MHC class I presentation pathway is a challenge for the immune system and is believed to rely on cross‐presentation. ...Cytomegalovirus (CMV) infection induces vigorous CD8+ T‐cell responses despite its potent immune evasion strategies. Furthermore, CD8+ T cells specific for a subset of viral epitopes accumulate and are maintained at high levels exhibiting an activated phenotype – referred to as “inflationary T cells”. Taking advantage Batf3−/− mice in which the development of cross‐presenting CD8α+ and CD103+ DCs is severely compromised, we analyzed their role in the induction and inflation of murine (M)CMV‐specific CD8+ T‐cell responses. We found that priming of MCMV‐specific CD8+ T cells was severely impaired in the absence of cross‐presenting DCs. However, inflation of two immuno‐dominant MCMV‐specific CD8+ T‐cell populations was largely normal in the absence of cross‐presenting DCs, indicating that inflation during latency was mainly dependent on direct antigen presentation. These results highlight differential antigen presentation requirements during acute and latent MCMV infection.
Horizontal transmission of cytomegaloviruses (CMV) occurs via prolonged excretion from mucosal surfaces. We used murine CMV (MCMV) infection to investigate the mechanisms of immune control in ...secretory organs. CD4 T cells were crucial to cease MCMV replication in the salivary gland (SG) via direct secretion of IFNγ that initiated antiviral signaling on non-hematopoietic cells. In contrast, CD4 T cell helper functions for CD8 T cells or B cells were dispensable. Despite SG-resident MCMV-specific CD8 T cells being able to produce IFNγ, the absence of MHC class I molecules on infected acinar glandular epithelial cells due to viral immune evasion, and the paucity of cross-presenting antigen presenting cells (APCs) prevented their local activation. Thus, local activation of MCMV-specific T cells is confined to the CD4 subset due to exclusive presentation of MCMV-derived antigens by MHC class II molecules on bystander APCs, resulting in IFNγ secretion interfering with viral replication in cells of non-hematopoietic origin.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
IL-10 is an anti-inflammatory cytokine that regulates the extent of host immunity to infection by exerting suppressive effects on different cell types. Herpes viruses induce IL-10 to modulate the ...virus-host balance towards their own benefit, resulting in prolonged virus persistence. To define the cellular and molecular players involved in IL-10 modulation of herpes virus-specific immunity, we studied mouse cytomegalovirus (MCMV) infection. Here we demonstrate that IL-10 specifically curtails the MCMV-specific CD4 T cell response by suppressing the bidirectional crosstalk between NK cells and myeloid dendritic cells (DCs). In absence of IL-10, NK cells licensed DCs to effectively prime MCMV-specific CD4 T cells and we defined the pro-inflammatory cytokines IL-12, IFN-γ and TNF-α as well as NK cell activating receptors NKG2D and NCR-1 to regulate this bidirectional NK/DC interplay. Consequently, markedly enhanced priming of MCMV-specific CD4 T cells in Il10(-/-) mice led to faster control of lytic viral replication, but this came at the expense of TNF-α mediated immunopathology. Taken together, our data show that early induction of IL-10 during MCMV infection critically regulates the strength of the innate-adaptive immune cell crosstalk, thereby impacting beneficially on the ensuing virus-host balance for both the virus and the host.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The highly contagious SARS-CoV-2 is mainly transmitted by respiratory droplets and aerosols. Consequently, people are required to wear masks and maintain a social distance to avoid spreading of the ...virus. Despite the success of the commercially available vaccines, the virus is still uncontained globally. Given the tropism of SARS-CoV-2, a mucosal immune reaction would help to reduce viral shedding and transmission locally. Only seven out of hundreds of ongoing clinical trials are testing the intranasal delivery of a vaccine against COVID-19.
In the current study, we evaluated the immunogenicity of a traditional vaccine platform based on virus-like particles (VLPs) displaying RBD of SARS-CoV-2 for intranasal administration in a murine model. The candidate vaccine platform, CuMV
-RBD, has been optimized to incorporate a universal T helper cell epitope derived from tetanus-toxin and is self-adjuvanted with TLR7/8 ligands.
CuMV
-RBD vaccine elicited a strong systemic RBD- and spike-IgG and IgA antibodies of high avidity. Local immune response was assessed, and our results demonstrate a strong mucosal antibody and plasma cell production in lung tissue. Furthermore, the induced systemic antibodies could efficiently recognize and neutralize different variants of concern (VOCs).
Our data demonstrate that intranasal administration of CuMV
-RBD induces a protective systemic and local specific antibody response against SARS-CoV-2 and its VOCs.
Cytomegalovirus (CMV) infects a majority of the human population and establishes a life‐long persistence. CMV infection is usually asymptomatic but the virus carries pathogenic potential and causes ...severe disease in immunocompromised individuals. T‐cell‐mediated immunity plays an essential role in control of CMV infection and adoptive transfer of CMV‐specific CD8+ T cells restores viral immunity in immunosuppressed patients but a role for CD4+ T cells remains elusive. Here, we analyzed in adoptive transfer studies the features and antiviral functions of virus‐specific CD4+ T cells during primary murine CMV (MCMV) infection. MCMV‐specific CD4+ T cells expanded upon MCMV infection and displayed an effector phenotype and function. Adoptive transfer of in vivo activated MCMV‐specific CD4+ T cells to immune‐compromised mice was protective during pathogenic MCMV infection and IFN‐γ was a crucial mediator of this protective capacity. Moreover, co‐transfer of low doses of both MCMV‐specific CD4+ T cells and CD8+ T cells synergized in control of lytic viral replication in immune‐compromised mice. Our data reveal a pivotal antiviral role for virus‐specific CD4+ T cells in protection from pathogenic CMV infection and provide evidence for their antiviral therapeutic potential.
Background
SARS‐CoV‐2 caused one of the most devastating pandemics in the recent history of mankind. Due to various countermeasures, including lock‐downs, wearing masks, and increased hygiene, the ...virus has been controlled in some parts of the world. More recently, the availability of vaccines, based on RNA or adenoviruses, has greatly added to our ability to keep the virus at bay; again, however, in some parts of the world only. While available vaccines are effective, it would be desirable to also have more classical vaccines at hand for the future. Key feature of vaccines for long‐term control of SARS‐CoV‐2 would be inexpensive production at large scale, ability to make multiple booster injections, and long‐term stability at 4℃.
Methods
Here, we describe such a vaccine candidate, consisting of the SARS‐CoV‐2 receptor‐binding motif (RBM) grafted genetically onto the surface of the immunologically optimized cucumber mosaic virus, called CuMVTT‐RBM.
Results
Using bacterial fermentation and continuous flow centrifugation for purification, the yield of the production process is estimated to be >2.5 million doses per 1000‐litre fermenter run. We demonstrate that the candidate vaccine is highly immunogenic in mice and rabbits and induces more high avidity antibodies compared to convalescent human sera. The induced antibodies are more cross‐reactive to mutant RBDs of variants of concern (VoC). Furthermore, antibody responses are neutralizing and long‐lived. In addition, the vaccine candidate was stable for at least 14 months at 4℃.
Conclusion
Thus, the here presented VLP‐based vaccine may be a good candidate for use as conventional vaccine in the long term.
In this study, we describe a novel conventional COVID‐19 vaccine that consists of the RBM of SARS‐CoV‐2 genetically grafted onto the surface of our optimized cucumber‐mosaic virus‐like particles. We demonstrate that the vaccine candidate (mCuMVTT‐RBM) is highly immunogenic in mice and rabbits, can efficiently neutralize SARS‐CoV‐2, and is stable and highly scalable. The induced antibodies show cross‐reactivity with VoC. Abbreviations: COVID‐19, coronavirus disease 2019; CuMVTT‐VLPs, cucumber‐mosaic virus‐like particles; RBD, receptor‐binding domain; RBM, receptor‐binding motif; SARS‐CoV‐2, severe acute respiratory syndrome coronavirus 2; VOCs, variant of concerns.
Cytomegaloviruses (CMVs) disseminate within the human population via mucosal excretions, for example, from the salivary glands (SGs), which represent a privileged site of viral immune evasion and ...persistence. The murine CMV (MCMV) model has served to identify factors that maintain a unique virus–host relationship in this organ. In contrast to all other organs, the SG is resistant to CD8+ T‐cell mediated control of MCMV replication due to virally induced MHC class I downregulation, which is exceptionally efficient in acinar glandular epithelial cells. Uniquely to the SG, IFN‐γ producing CD4+ T cells are required for virus control. While T‐cell responses have been extensively characterized in the SG, the ontogeny and function of APCs in this organ remain to be assessed. Here, we show that macrophage‐like cells constitute the population of SG‐resident APCs in steady state and during MCMV‐induced inflammation in mice. Inflammatory monocytes, monocyte‐derived DCs as well as conventional, Flt3L‐dependent DCs do not contribute to this population. Despite supporting contact formation to CD4+ and CD8+ T cells in principle, SG‐resident APCs fail to activate the latter due to their inability to cross‐present MCMV‐derived antigen.
Background
The highly contagious SARS‐CoV‐2 is mainly transmitted by respiratory droplets and aerosols. Consequently, people are required to wear masks and maintain a social distance to avoid ...spreading of the virus. Despite the success of the commercially available vaccines, the virus is still uncontained globally. Given the tropism of SARS‐CoV‐2, a mucosal immune reaction would help to reduce viral shedding and transmission locally. Only seven out of hundreds of ongoing clinical trials are testing the intranasal delivery of a vaccine against COVID‐19.
Methods
In the current study, we evaluated the immunogenicity of a traditional vaccine platform based on virus‐like particles (VLPs) displaying RBD of SARS‐CoV‐2 for intranasal administration in a murine model. The candidate vaccine platform, CuMVTT‐RBD, has been optimized to incorporate a universal T helper cell epitope derived from tetanus‐toxin and is self‐adjuvanted with TLR7/8 ligands.
Results
CuMVTT‐RBD vaccine elicited a strong systemic RBD‐ and spike‐IgG and IgA antibodies of high avidity. Local immune response was assessed, and our results demonstrate a strong mucosal antibody and plasma cell production in lung tissue. Furthermore, the induced systemic antibodies could efficiently recognize and neutralize different variants of concern (VOCs).
Conclusion
Our data demonstrate that intranasal administration of CuMVTT‐RBD induces a protective systemic and local specific antibody response against SARS‐CoV‐2 and its VOCs.
In this study, we describe a COVID‐19 vaccine based on virus‐like particles (VLPs) for intranasal administration. We demonstrate that the vaccine candidate (CuMVTT‐RBD) is highly immunogenic in mice and is capable of inducing mucosal and systemic RBD as well as spike specific antibody responses. The induced antibodies are capable of neutralizing SARS‐CoV‐2 and variants of concern (VOCs).Abbreviations: COVID‐19, coronavirus disease 2019; RBD, receptor‐binding domain; SARS‐CoV‐2, severe acute respiratory syndrome coronavirus 2; VLPs, virus‐like particles; VOC, variant of concern
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