Memory CD4+ T-Cell Lymphocytic Angiopathy in Fatal Forms of COVID-19 Pulmonary Infection

The immunopathological pulmonary mechanisms leading to Coronavirus Disease (COVID-19)-related death in adults remain poorly understood. Bronchoalveolar lavage (BAL) and peripheral blood sampling were performed in 74 steroid and non-steroid-treated intensive care unit (ICU) patients (23-75 years; 44 survivors). Peripheral effector SARS-CoV-2-specific T cells were detected in 34/58 cases, mainly directed against the S1 portion of the spike protein. The BAL lymphocytosis consisted of T cells, while the mean CD4/CD8 ratio was 1.80 in non-steroid- treated patients and 1.14 in steroid-treated patients. Moreover, strong BAL SARS-CoV-2 specific T-cell responses were detected in 4/4 surviving and 3/3 non-surviving patients. Serum IFN-γ and IL-6 levels were decreased in steroid-treated patients when compared to non-steroid treated patients. In the lung samples from 3 (1 non-ICU and 2 ICU) additional deceased cases, a lymphocytic memory CD4 T-cell angiopathy colocalizing with SARS-CoV-2 was also observed. Taken together, these data show that disease severity occurs despite strong antiviral CD4 T cell-specific responses migrating to the lung, which could suggest a pathogenic role for perivascular memory CD4 T cells upon fatal COVID-19 pneumonia.

Elevated Neopterin Levels Predict Fatal Outcome in SARS-CoV-2-Infected Patients

Highlights

Innate immune activation during Covid-19 infection is associated with pernicious clinical outcome.

Background

Coronavirus disease 2019 (Covid-19) is a worldwide threat that has already caused more than 3 000 000 deaths. It is characterized by different patterns of disease evolution depending on host factors among which old-age and pre-existing comorbidities play a detrimental role. Previous coronavirus epidemics, notably SARS-CoV, were associated with increased serum neopterin levels, which can be interpreted as a sign of acute innate immunity in response to viral infection. Here we hypothesize that neopterin may serve as a biomarker of SARS-CoV-2 viral infection and Covid-19 disease severity.

Methods

We measured neopterin blood levels by ELISA. Seric concentration was quantified from 256 healthy donors and 374 Covid-19 patients at hospital admission. Enrolled Covid-19 patients were all symptomatic and displayed a large spectrum of comorbidities. Patients were followed until disease resolution or death.

Results

Severe and critically ill SARS-CoV-2 infected patients were characterized by a profound exacerbation of immune activation characterized by elevated neopterin blood levels. Systemic neopterin levels above 19nM stratified healthy individuals from Covid-19 patients with 87% specificity and 100% sensitivity. Moreover, systemic neopterin levels above 53nM differentiated non-survivors from survivors with 64% specificity and 100% sensitivity.

Conclusion

We propose that neopterin concentration measured at arrival to hospital is a hallmark of severe Covid-19 and identifies a high-risk population of pernicious clinical outcome with a need for special medical care.

OVX836 Heptameric Nucleoprotein Vaccine Generates Lung Tissue-Resident Memory CD8+ T-Cells for Cross-Protection Against Influenza

Tissue-resident memory (TRM) CD8+ T-cells play a crucial role in the protection against influenza infection but remain difficult to elicit using recombinant protein vaccines. OVX836 is a recombinant protein vaccine, obtained by the fusion of the DNA sequence of the influenza A nucleoprotein (NP) to the DNA sequence of the OVX313 heptamerization domain. We previously demonstrated that OVX836 provides broad-spectrum protection against influenza viruses. Here, we show that OVX836 intramuscular (IM) immunization induces higher numbers of NP-specific IFNγ-producing CD8+ T-cells in the lung, compared to mutant NP (NPm) and wild-type NP (NPwt), which form monomeric and trimeric structures, respectively. OVX836 induces cytotoxic CD8+ T-cells and high frequencies of lung TRM CD8+ T-cells, while inducing solid protection against lethal influenza virus challenges for at least 90 days. Adoptive transfer experiments demonstrated that protection against diverse influenza subtypes is mediated by NP-specific CD8+ T-cells isolated from the lung and spleen following OVX836 vaccination. OVX836 induces a high number of NP-specific lung CD8+ TRM-cells for long-term protection against influenza viruses.

Imaging resident and recruited macrophage contribution to Wallerian degeneration

Wallerian degeneration (WD) is a process of autonomous distal degeneration of axons upon injury. Macrophages (MPs) of the peripheral nervous system (PNS) are the main cellular agent controlling this process. Some evidence suggests that resident PNS-MPs along with MPs of hematogenous origin may be involved, but whether these two subsets exert distinct functions is unknown. Combining MP-designed fluorescent reporter mice and coherent anti–Stokes Raman scattering (CARS) imaging of the sciatic nerve, we deciphered the spatiotemporal choreography of resident and recently recruited MPs after injury and unveiled distinct functions of these subsets, with recruited MPs being responsible for efficient myelin stripping and clearance and resident MPs being involved in axonal regrowth. This work provides clues to tackle selectively cellular processes involved in neurodegenerative diseases.

[Adaptive immunity against SARS-CoV-2]

The impact of host adaptive immune response on COVID-19 has now become a critical issue in absence of specific therapy and immunotherapies. In SARS CoV-2 infection, the immune response is thought to contribute both to the pathogenesis of the disease and to protection during its resolution. While mild cases develop an immune response that contributes to host protection, immunity of severely infected patients is a balance between harmful and protective immune responses. The severity of the disease has raised many questions about the kinetic, amplitude and the quality of adaptive immunity to the virus and its generation during the early phases of infection in severe, mild and asymptomatic patients. The role of antibody and CD4⁺ and CD8⁺ T cell responses have been studied and the development of an adaptive immunity seems to correlate with convalescence. The bioinformatics study of the T and B epitopes of coronaviruses has raised the question of the existence of cross-immunity between SARS-CoV-2 and other coronaviruses such as MERS-CoV and SARS-CoV. In this review, we discuss the adaptive immune responses and their potential roles in protection during COVID-19.

Prédire la réponse à la vaccination contre la grippe

La vaccination est l’un des progrès majeurs de la médecine moderne. Mais afin d’améliorer l’efficacité des vaccins existants et d’en élaborer de nouveaux, nous devons mieux connaître les mécanismes d’action à l’origine de l’immunité protectrice et les stratégies vaccinales permettant d’induire une défense durable. La voie cutanée est une stratégie de vaccination importante, en raison de la richesse qu’elle présente en cellules de l’immunité innée qui ont un rôle clé dans la qualité, l’intensité et la persistance des réponses adaptatives qu’elles induisent. L’intégration des données biologiques obtenues au cours d’un essai clinique de vaccination antigrippale nous donne un aperçu de l’impact de la voie d’immunisation et de la signature innée sur la qualité des réponses immunitaires.

Acquired immune responses to the seasonal trivalent influenza vaccination in COPD

Epidemiological data suggest that influenza vaccination protects against all‐cause mortality in chronic obstructive pulmonary disease (COPD) patients. However, recent work has suggested there is a defect in the ability of some COPD patients to mount an adequate humoral response to influenza vaccination. The aim of our study was to investigate humoral and cell‐mediated vaccine responses to the seasonal trivalent influenza vaccination (TIV) in COPD subjects and healthy controls. Forty‐seven subjects were enrolled into the study; 23 COPD patients, 13 age‐matched healthy controls (HC ≥ 50) and 11 young healthy control subjects (YC ≤ 40). Serum and peripheral blood mononuclear cells (PBMC) were isolated pre‐TIV vaccination and at days 7 and 28 and 6 months post‐vaccine for haemagglutinin inhibition (HAI) titre, antigen‐specific T cell and antibody‐secreting cell analysis. The kinetics of the vaccine response were similar between YC, HC and COPD patients and there was no significant difference in antibody titres between these groups at 28 days post‐vaccine. As we observed no disease‐dependent differences in either humoral or cellular responses, we investigated if there was any association of these measures with age. H1N1 (r = −0·4253, P = 0·0036) and influenza B (r = −0·344, P = 0·0192) antibody titre at 28 days negatively correlated with age, as did H1N1‐specific CD4⁺ T helper cells (r = −0·4276, P = 0·0034). These results suggest that age is the primary determinant of response to trivalent vaccine and that COPD is not a driver of deficient responses per se. These data support the continued use of the yearly trivalent vaccine as an adjunct to COPD disease management.

HIV therapeutic vaccine enhances non-exhausted CD4+ T cells in a randomised phase 2 trial

VAC-3S is a therapeutic vaccine comprising a highly conserved HIV-gp41 motif coupled with the CRM197 carrier protein. High levels of anti-3S antibodies (Abs) have been associated with improved protection of CD4⁺ T-cell survival. A previous phase 1 study demonstrated the safety of VAC-3S. This multicentre, randomised, double-blind, placebo-controlled phase 2 clinical trial enroled between January 2014 and March 2015 HIV-1-infected patients under ART with plasma HIV RNA levels below 50 copies/mL and CD4 counts between 200 and 500 cells/μL. Participants were immunised with 16, 32, or 64 μg of VAC-3S, and compared to placebo. The primary outcome was immunogenicity assessed by changes from baseline of anti-3S Abs levels at week 12. Secondary outcomes included adverse events and the course of plasma HIV RNA level, CD4 count, CD4/CD8 ratio, inflammation and immune checkpoints from week 0 to week 48. Vaccination was well tolerated with no serious adverse events and induced a significant increase in anti-3S Ab response in vaccinated patients (p < 0.0001), compared to placebo. In high responders, the robust increased of CD4 count was associated with a significant and sustained reduction of PD-1 expression on CD4⁺ T cells through week 48 (variance p = 0.0017). PD-1 expression was correlated with level of anti-3S Abs (p = 0.0092, r = −0.68) and expression of NKp44L (p < 0.0001; r = 0.54) in CD4⁺ T cells. Our findings regarding the increase of non-exhausted CD4⁺ T cells have potentially important application in personalised HIV vaccination for HIV-infected patients with high level of PD-1 to improve their T-cell immune function.

Macrophages of distinct origins contribute to tumor development in the lung

Tissue-resident macrophages can self-maintain without contribution of adult hematopoiesis. Herein we show that tissue-resident interstitial macrophages (Res-TAMs) in mouse lungs contribute to the pool of tumor-associated macrophages (TAMs) together with CCR2-dependent recruited macrophages (MoD-TAMs). Res-TAMs largely correlated with tumor cell growth in vivo, while MoD-TAMs accumulation was associated with enhanced tumor spreading. Both cell subsets were depleted after chemotherapy, but MoD-TAMs rapidly recovered and performed phagocytosis-mediated tumor clearance. Interestingly, anti-VEGF treatment combined with chemotherapy inhibited both Res and Mod-TAM reconstitution without affecting monocyte infiltration and improved its efficacy. Our results reveal that the developmental origin of TAMs dictates their relative distribution, function, and response to cancer therapies in lung tumors.

Interleukin-32 promotes detachment and activation of human Langerhans cells in a human skin explant model

BACKGROUND

Cross-talk between skin keratinocytes (KCs) and Langerhans cells (LCs) plays a fundamental role in the body's first line of immunological defences. However, the mechanism behind the interaction between these two major epidermal cells is unknown. Interleukin (IL)-32 is produced in inflammatory skin disorders. We questioned the role of IL-32 in the epidermis.

OBJECTIVES

We aimed to determine the role of IL-32 produced by KCs on surrounding LCs.

METHODS

We used an ex vivo human explant model from healthy donors and investigated the role of IL-32 on LC activation using imaging, flow cytometry, reverse transcriptase quantitative polymerase chain reaction and small interfering (si)RNA treatment.

RESULTS

Modified vaccinia virus ankara (MVA) infection induced KC death alongside the early production of the proinflammatory cytokine IL-32. We demonstrated that IL-32 produced by MVA-infected KCs induced modest but significant morphological changes in LCs and downregulation of adhesion molecules, such as epithelial cell adhesion molecule and very late antigen-4, and CXCL10 production. The treatment of KCs with IL-32-specific siRNA, and anti-IL-32 blocking antibody significantly inhibited LC activation, demonstrating the role of IL-32 in LC activation. We also found that some Toll-like receptor ligands induced a very high level of IL-32 production by KCs, which initiated LC activation.

CONCLUSIONS

We propose, for the first time, that IL-32 is a molecular link between KCs and LCs in healthy skin, provoking LC migration from the epidermis to the dermis prior to their migration to the draining lymph nodes.

Topically applied virus-like particles containing HIV-1 Pr55gag protein reach skin antigen-presenting cells after mild skin barrier disruption

Loading of antigen on particles as well as the choice of skin as target organ for vaccination were independently described as effective dose-sparing strategies for vaccination. Combining these two strategies, sufficient antigen recognition may be achievable via the transcutaneous route even with minimal-invasive tools. Here, we investigated the skin penetration and cellular uptake of topically administered virus-like particles (VLPs), composed of the HIV-1 precursor protein Pr55^gag, as well as the migratory activity of skin antigen-presenting cells (APCs). We compared VLP administration on ex vivo human skin pre-treated with cyanoacrylate tape stripping (CSSS, minimal-invasive) to administration by skin pricking and intradermal injection (invasive). CSSS as well as pricking treatments resulted in penetration of VLPs in the viable skin layers. Electron microscopy confirmed that at least part of VLPs remained intact during the penetration process. Flow cytometry of epidermal, dermal, and HLA-DR⁺ APCs harvested from culture media of skin explants cultivated at air-liquid interface revealed that a number of cells had taken-up VLPs. Similar results were found between invasive and minimal-invasive VLP application methods. CSSS pre-treatment was associated with significantly increased levels of IL-1α levels in cell culture media as compared to untreated and pricked skin. Our findings provide first evidence for effective cellular uptake of VLPs after dermal application and indicate that even mild physical barrier disruption, as induced by CSSS, provides stimulatory signals that enable the activation of APCs and uptake of large antigenic material.

[Not Available]

SUMMARYThe explosion of vaccines during the 20th century allowed the control of numerous infectious plagues but multiple challenges oppose conservation and extension of these successes. The hesitation of modern societies in front of vaccinations requires researches in life, human and social sciences in order to reach a better understanding of vaccines mechanism of action and to improve the tolerance and acceptability of vaccines and additives. The ageing of the populations and the increase of subjects at risk also require to improve the immunogenicity and the efficiency of existing vaccines. The constant emergence of new epidemics or the development of the antibio-resistance imposes innovation and development of new vaccines. The recent difficulties faced by the development of vaccines against malaria, tuberculosis or AIDS illustrate the necessity of moving beyond classical recipes and of elaborating new vectors and new adjuvants, of better understanding the heterogeneity of vaccine immunity and of developing alternative routes of immunization. Multidisciplinary researches using the most recent advances in molecular, structural and cellular biology, in microbiology, immunology and of genetic engineering to answer these worldwide challenges.

New challenges in modern vaccinology

Vaccination has been a major advance for health care, allowing eradication or reduction of incidence and mortality of various infectious diseases. However, there are major pathogens, such as Human Immunodeficiency Virus (HIV) or the causative agent of malaria, for which classical vaccination approaches have failed, therefore requiring new vaccination strategies. The development of new vaccine strategies relies on the ability to identify the challenges posed by these pathogens. Understanding the pathogenesis and correlates of protection for these diseases, our ability to accurately direct immune responses and to vaccinate specific populations are such examples of these roadblocks. In this respect, the use of a robust, cost-effective and predictive animal model that recapitulates features of both human infection and vaccination is currently a much-needed tool. We discuss here the major limitations faced by modern vaccinology and notably, the development of humanized mice for assessing the immune system, along with their potential as vaccine models.

Low titers of serum antibodies inhibiting hemagglutination predict fatal fulminant influenza A(H1N1) 2009 infection

RATIONALE

The biology of fatal pandemic influenza infection remains undefined.

OBJECTIVES

To characterize the virologic and immune parameters associated with severity or death in patients who required mechanical ventilation for A(H1N1) 2009 pneumonia of various degrees of severity during the two waves of the 2009-2011 pandemic in Paris, France.

METHODS

This multicenter study included 34 unvaccinated patients with very severe or fatal confirmed influenza A(H1N1) infections. It analyzed plasma A(H1N1) 2009 reverse-transcriptase polymerase chain reaction, hemagglutinin 222G viral mutation, and humoral and cellular immune responses to the virus, assessed in hemagglutination inhibition (HI), microneutralization, ELISA, lymphoproliferative, ELISpot IFN-γ, and cytokine and chemokine assays.

MEASUREMENTS AND MAIN RESULTS

The patients' median age was 35 years. Influenza A(H1N1) 2009 viremia was detected in 4 of 34 cases, and a 222G hemagglutinin mutation in 7 of 17 cases, all of them with sequential organ failure assessment greater than or equal to 8. HI antibodies were detectable in 19 of 26 survivors and undetectable in all six fatal fulminant cases. ELISA and microneutralization titers were concordant. B-cell immunophenotyping and plasma levels of immunoglobulin classes did not differ between patients who survived and died. After immune complex dissociation, influenza ELISA serology became strongly positive in the bronchoalveolar lavage of the two fatal cases tested. H1N1-specific T-cell responses in lymphoproliferative and IFN-γ assays were detectable in survivors' peripheral blood, and lymphoproliferative assays were negative in the three fatal cases tested. Plasma levels of IL-6 and IL-10 were high in fatal cases and correlated with severity. Finally, a negative HI serology 4 days after the onset of influenza symptoms predicted death from fulminant influenza (P = 0.04).

CONCLUSIONS

Early negative A(H1N1) 2009 HI serology can predict death from influenza. This negative serology in fatal cases in young adults reflects the trapping of anti-H1N1 antibodies in immune complexes in the lungs, associated with poor specific helper T-cell response. Clinical trial registered with www.clinicaltrials.gov (NCT 01089400).

Recombinant retrovirus-derived virus-like particle-based vaccines induce hepatitis C virus-specific cellular and neutralizing immune responses in mice

While the immunological correlates of hepatitis C virus (HCV)-specific immunity are not well understood, it is now admitted that an effective vaccine against HCV will need to induce both cellular and humoral immune responses and address viral heterogeneity to prevent immune escape. We developed a vaccine platform specifically aimed at inducing such responses against HCV antigens displayed by recombinant retrovirus-based virus-like particles (VLPs) made of Gag of murine leukemia virus. Both ex vivo produced VLPs and plasmid DNA encoding VLPs can be used as vaccines. Here, we report that immunizations with plasmid DNA forming VLPs pseudotyped with HCV E1 and E2 envelope glycoproteins (HCV-specific plasmo-retroVLPs) induce strong T-cell-mediated immune responses that can be optimized by using proper DNA delivery methods and/or genetic adjuvants. Additionally, multigenotype or multi-specific T-cell responses were observed after immunization with plasmids that encode VLPs pseudotyped with E1E2 derived from numerous viral genotypes and/or displaying NS3 antigen in capsid proteins. While homologous prime-boost immunizations with HCV-specific plasmo-retroVLPs or ex vivo produced VLPs induce a low level of specific antibody responses, optimal combination of plasmo-retroVLPs and VLPs was identified for inducing HCV-specific T-cell and B-cell responses as well as neutralizing antibodies. Altogether, these results have important meanings for the development of anti-HCV preventive vaccines and exemplify the flexibility and potential of our retrovirus-based platform in inducing broad cellular and humoral immune responses.

[Current events in vaccination]

The annual meeting of the Infectious Disease Society of America (IDSA) ; which brought together nearly 5000 participants from over 80 countries in Vancouver, Canada, October 21 to 24, 2010 ; provided a review of the influenza (H1N1) 2009 pandemic, evaluated vaccination programmes and presented new vaccines under development. With 12,500 deaths in the United States in 2009-2010, the influenza (H1N1) 2009 pandemic was actually less deadly than the seasonal flu. But it essentially hit the young, and the toll calculated in years of life lost is high. The monovalent vaccines, whether live attenuated or inactivated with or without adjuvants, were well tolerated in toddlers, children, adults and pregnant women. In order to protect infants against pertussis, family members are urged to get their booster shots. The introduction of the 13-valent Pneumococcal conjugated vaccine in the beginning of 2010 may solve - but for how long ? - the problem of serotype replacement, responsible for the re-increasing incidence of invasive Pneumococcal infections observed in countries that had introduced the 7-valent vaccine. The efficacy of a rotavirus vaccine has been confirmed, with a reduction in hospitalization in the United States and a reduction in gastroenteritis-related deaths in Mexico. In the United States, vaccination of pre-adolescents against human papillomavirus (HPV) has not resulted in any specific undesirable effects. Routine vaccination against chicken pox, recommended since 1995, has not had an impact on the evolution of the incidence of shingles. Vaccination against shingles, recommended in the United States for subjects 60 years and over, shows an effectiveness of 55 %, according to a cohort study (Kaiser Permanente, Southern California). Although some propose the development of personalized vaccines according to individual genetic characteristics, the priority remains with increasing vaccine coverage, not only in infants but also in adults and the elderly. Vaccine calendars that cover a whole lifetime should be promoted, since the vaccination of adults and seniors is a determining factor of good health at all ages.

CD56brightCD16+ NK cells: a functional intermediate stage of NK cell differentiation

Human NK cells comprise two main subsets, CD56(bright) and CD56(dim) cells, which differ in function, phenotype, and tissue localization. To further dissect the differentiation from CD56(bright) to CD56(dim) cells, we performed ex vivo and in vitro experiments demonstrating that the CD56(bright)CD16(+) cells are an intermediate stage of NK cell maturation. We observed that the maximal frequency of the CD56(bright)CD16(+) subset among NK cells, following unrelated cord blood transplantation, occurs later than this of the CD56(bright)CD16(-) subset. We next performed an extensive phenotypic and functional analysis of CD56(bright)CD16(+) cells in healthy donors, which displayed a phenotypic intermediary profile between CD56(bright)CD16(-) and CD56(dim)CD16(+) NK cells. We also demonstrated that CD56(bright)CD16(+) NK cells were fully able to kill target cells, both by Ab-dependent cell cytotoxicity (ADCC) and direct lysis, as compared with CD56(bright)CD16(-) cells. Importantly, in vitro differentiation experiments revealed that autologous T cells specifically encourage the differentiation from CD56(bright)CD16(-) to CD56(bright)CD16(+) cells. Finally, further investigations performed in elderly patients clearly showed that both CD56(bright)CD16(+) and CD56(dim)CD16(+) mature subsets were substantially increased in older individuals, whereas the CD56(bright)CD16(-) precursor subset was decreased. Altogether, these data provide evidence that the CD56(bright)CD16(+) NK cell subset is a functional intermediate between the CD56(bright) and CD56(dim) cells and is generated in the presence of autologous T CD3(+) cells.

Mycobacterium bovis bacillus Calmette-Guérin vaccination mobilizes innate myeloid-derived suppressor cells restraining in vivo T cell priming via IL-1R-dependent nitric oxide production

Early immune response to the largely used Mycobacterium bovis bacillus Calmette-Guérin (BCG) intradermal vaccine remains ill defined. Three days after BCG inoculation into the mouse ear, in addition to neutrophils infiltrating skin, we observed CD11b(+)Ly-6C(int)Ly-6G(-) myeloid cells. Neutrophil depletion markedly enhanced their recruitment. These cells differed from inflammatory monocytes and required MyD88-dependent BCG-specific signals to invade skin, whereas neutrophil influx was MyD88 independent. Upon BCG phagocytosis, CD11b(+)Ly-6C(int)Ly-6G(-) cells produced NO, which required the IL-1 receptor. Despite NO production, they were unable to kill BCG or the nonpathogenic Mycobacterium smegmatis. However, they markedly impaired T cell priming in the draining lymph node. Their elimination by all-trans retinoid acid treatment increased the number of IFN-gamma-producing CD4 T cells. Thus, BCG vaccination recruits innate myeloid-derived suppressor cells, akin to mouse tumor-infiltrating cells. These propathogenic cells dampen the early T cell response and might facilitate BCG persistence.

Original encounter with antigen determines antigen-presenting cell imprinting of the quality of the immune response in mice

Background

Obtaining a certain multi-functionality of cellular immunity for the control of infectious diseases is a burning question in immunology and in vaccine design. Early events, including antigen shuttling to secondary lymphoid organs and recruitment of innate immune cells for adaptive immune response, determine host responsiveness to antigens. However, the sequence of these events and their impact on the quality of the immune response remain to be elucidated. Here, we chose to study Modified Vaccinia virus Ankara (MVA) which is now replacing live Smallpox vaccines and is proposed as an attenuated vector for vaccination strategies against infectious diseases.

Methodology/Principal findings

We analyzed in vivo mechanisms triggered following intradermal (i.d.) and intramuscular (i.m.) Modified Vaccinia virus Ankara (MVA) administration. We demonstrated significant differences in the antigen shuttling to lymphoid organs by macrophages (MΦs), myeloid dendritic cells (DCs), and neutrophils (PMNs). MVA i.d. administration resulted in better antigen distribution and more sustained antigen-presenting cells (APCs) recruitment into draining lymph nodes than with i.m. administration. These APCs, which comprise both DCs and MΦs, were differentially involved in T cell priming and shaped remarkably the quality of cytokine-producing virus-specific T cells according to the entry route of MVA.

Conclusions/Significance

This study improves our understanding of the mechanisms of antigen delivery and their consequences on the quality of immune responses and provides new insights for vaccine development.

Influence of antigen exposure on the loss of long-term memory to childhood vaccines in HIV-infected patients

The role of antigen exposure and of CD4 cell deficiency in the long-term persistence of immune memory to childhood vaccines remains uncertain, particularly during HIV infection. We analyzed in vaccinated ART-treated HIV+ patients with undetectable plasma HIV and CD4 cells >250/mm(3) the persistence of two memory cell pools: effector IFNgamma-producing and proliferative central memory T cells against two vaccines: (i) vaccinia against the eradicated smallpox virus, and (ii) BCG against Mtb, a persistent pathogen. None of the HIV+ patients had IFNgamma-effector cells against VV while the one patient with BCG-specific effector T cells had a recent history of tuberculosis. Proliferative responses were detectable but showed significantly lower frequency and intensity of VV-specific than tuberculin-specific responses, independently of the CD4 nadir. Thus, differential patterns of persistence or recovery of T cell memory pools against childhood vaccines are observed in treated HIV infection that are governed by antigen exposure.

Demographic and clinical factors associated with response to smallpox vaccine in preimmunized volunteers

Context

In March 2003, the French Ministry of Health implemented a program on preparedness and response to a biological attack using smallpox as weapon. This program included the establishment of a preoutbreak national team that could be revaccinated against smallpox.

Objective

To identify demographic and clinical factors associated with vaccination success defined as the presence of a pustule at the inoculation site at day 8 (days 7–9), with an undiluted vaccinia virus derived from a Lister strain among preimmunized volunteers.

Volunteers and Methods

From March 2003 to November 2006, we have studied prospectively 226 eligible volunteers. Demographic data were recorded for each volunteer (age, sex, number of previously smallpox vaccinations and date of the last vaccination). Smallpox vaccine adverse reactions were diagnosed on the basis of clinical examination performed at days 0, 7, 14, 21 and 28 after revaccination.

Results

A total of 226 volunteers (sex ratio H/F = 2.7) were revaccinated. Median age was 45 years (range: 27–63 yrs). All volunteers completed follow-up. Median number of vaccinations before revaccination was 2 (range: 1–8). The median delay between time of the study and the last vaccination was 29 years (range; 18–60 yrs). Sixty-one volunteers (27%) experienced one (n = 40) or more (n = 21) minor side effects during the 2–14 days after revaccination. Successful vaccination was noted in 216/226 volunteers (95.6%) at day 8 and the median of the pustule diameter was 5 mm (range: 1–20 mm). Size of the pustule at day 8 was correlated with age (p = 0.03) and with the presence of axillary adenopathy after revaccination (p = 0.007). Sex, number of prior vaccinations, delay between the last vaccination and revaccination, and local or systemic side effects with the exception of axillary adenopathy, were not correlated with the size of the pustule at day 8.

Conclusions

Previously vaccinated volunteers can be successfully revaccinated with the Lister strain.

Infiltration of CD4+ lymphocytes into the brain contributes to neurodegeneration in a mouse model of Parkinson disease

Parkinson disease (PD) is a neurodegenerative disorder characterized by a loss of dopamine-containing neurons. Mounting evidence suggests that dopaminergic cell death is influenced by the innate immune system. However, the pathogenic role of the adaptive immune system in PD remains enigmatic. Here we showed that CD8+ and CD4+ T cells but not B cells had invaded the brain in both postmortem human PD specimens and in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD during the course of neuronal degeneration. We further demonstrated that MPTP-induced dopaminergic cell death was markedly attenuated in the absence of mature T lymphocytes in 2 different immunodeficient mouse strains (Rag1-/- and Tcrb-/- mice). Importantly, similar attenuation of MPTP-induced dopaminergic cell death was seen in mice lacking CD4 as well as in Rag1-/- mice reconstituted with FasL-deficient splenocytes. However, mice lacking CD8 and Rag1-/- mice reconstituted with IFN-gamma-deficient splenocytes were not protected. These data indicate that T cell-mediated dopaminergic toxicity is almost exclusively arbitrated by CD4+ T cells and requires the expression of FasL but not IFNgamma. Further, our data may provide a rationale for targeting the adaptive arm of the immune system as a therapeutic strategy in PD.

Targeting tumor antigens to secreted membrane vesicles in vivo induces efficient antitumor immune responses

Expression of non-self antigens by tumors can induce activation of T cells in vivo, although this activation can lead to either immunity or tolerance. CD8+ T-cell activation can be direct (if the tumor expresses MHC class I molecules) or indirect (after the capture and cross-presentation of tumor antigens by dendritic cells). The modes of tumor antigen capture by dendritic cells in vivo remain unclear. Here we examine the immunogenicity of the same model antigen secreted by live tumors either in association with membrane vesicles (exosomes) or as a soluble protein. We have artificially addressed the antigen to secreted vesicles by coupling it to the factor VIII-like C1C2 domain of milk fat globule epidermal growth factor-factor VIII (MFG-E8)/lactadherin. We show that murine fibrosarcoma tumor cells that secrete vesicle-bound antigen grow slower than tumors that secrete soluble antigen in immunocompetent, but not in immunodeficient, host mice. This growth difference is due to the induction of a more potent antigen-specific antitumor immune response in vivo by the vesicle-bound than by the soluble antigen. Finally, in vivo secretion of the vesicle-bound antigen either by tumors or by vaccination with naked DNA protects against soluble antigen-secreting tumors. We conclude that the mode of secretion can determine the immunogenicity of tumor antigens and that manipulation of the mode of antigen secretion may be used to optimize antitumor vaccination protocols.

Les chimiokines : un réseau sophistiqué de guidage cellulaire

The immune system relies on the motility on various cell types that roam the host through the blood, the peripheral tissues and the lymphoid organs, looking for pathogens. Along their maturation and/or activation, the cell migratory capacities change in order to allow them to leave organs where they have been produced such as thymus and bone marrow, to locate in strategic sites to sense surrounding microbes, to meet and interact with other cells, and finally to access peripheral tissues and organs to eradicate the pathogens. This cell traffic is a highly organized process that involves numerous protein families such as adhesion molecules, proteases and chemotactic factors. Among the latter, chemokines are in the front line. We will here summarize the recent findings stressing out their physiopathological relevance and will describe thereafter their possible therapeutic use.

High cytotoxic and specific migratory potencies of senescent CD8+ CD57+ cells in HIV-infected and uninfected individuals

CD8+ CD57+ T lymphocytes, present at low levels in the peripheral blood of healthy individuals expand during HIV infection and remain elevated during chronic infection. Their role in the immune response remains unclear. We performed a large-scale gene array analysis (3158 genes) to characterize them and, interestingly, found no distinction in the transcriptional profiles of CD8+ CD57+ T lymphocytes from HIV-infected and uninfected subjects. In both groups, these cells showed specificity for multiple Ags and produced large amounts of IFN-gamma and TNF-alpha. The transcriptional profiles of CD8+ CD57+ and CD8+ CD57- cells, however, differed substantially. We propose that CD8+ CD57+ cells were Ag-driven effector cells with very high cytotoxic effector potential including perforin, granzymes, and granulysin, regardless of HIV status. At both the messenger and protein levels, they expressed more adhesion molecules and fewer chemokine receptors (CCR7 and CXCR4) than CD8+ CD57- cells but expressed preferentially CX3CR1. The lower expression level of genes involved in cell cycle regulation showed limited proliferation capacities of CD8+ CD57+ even in response to TCR and IL-2, IL-7, and IL-15 stimulation. CD8+ CD57+ T cells from both HIV and uninfected subjects maintain effective cytotoxic potentials but are destined to migrate to nonlymphoid tissues without further cycling.

Trapping and apoptosis of novel subsets of memory T lymphocytes expressing CCR6 in the spleen of HIV-infected patients

CCR6, a homeostatic chemokine receptor, is shown here to characterize subsets of both central and effector memory T cells that secrete high levels of IL-2 and TNF-alpha in response to polyclonal and antigen-specific stimulation. CCR6(+) T lymphocytes disappeared dramatically from the peripheral blood of HIV-infected patients as HIV disease progressed. The capacity of CD4(+)CCR6(+) to secrete multiple cytokines remained intact among HIV-infected long-term nonprogressors but was partially lost from subjects with standard disease progression. CCR6(+) T lymphocytes, regardless of their CCR7 expression, accumulated in the spleen of HIV-infected patients, where they died by apoptosis. Assessment of CCR6 expression allowed us to describe novel memory T-cell subpopulations capable of high cytokine production and provided evidence of a pathologic CCR6-dependent pathway of memory T-cell homing that may participate in the loss of memory response against infections.

Prime-boost immunization with DNA, recombinant fowlpox virus and VLP(SHIV) elicit both neutralizing antibodies and IFNgamma-producing T cells against the HIV-envelope protein in mice that control env-bearing tumour cells

Different primings with DNA and fowlpox virus (FP) recombinants or FP alone were used in a pre-clinical trial to evaluate and compare immunogenicity and efficacy against HIV/SHIV. Three immunization regimens were tested in three groups of mice in which the SIV gag/pol and HIV-1 env transgenes were separately expressed by DNA and FP vectors, followed by VLP(SHIV) boosting. All of the protocols were effective in eliciting homologous neutralizing antibodies, although the mice immunized with DNA followed by FP recombinants or DNA+FP recombinants showed both high titres of neutralizing antibodies and high frequencies of env-specific IFNgamma-producing T lymphocytes. Vaccine efficacy, as demonstrated by growth control of env-expressing tumours, was obtained in both of these two groups of mice. These results establish a preliminary profile for the combined use of these recombinant vectors in protocols to be tested in the SHIV-macaque model of HIV-1 infection.

Biological weapons

Smallpox virus eradication was one of the greatest successes of the 20th century. Moreover, the quest to combat its use in biological warfare, has fueled efforts to understand residual immune memory and to develop new animal models by the scientific community. Although the literature is full of animal studies of vaccinia virus infection, continuing efforts have helped to increase our knowledge regarding humoral and cellular memory to non-persistent pathogens and to study factors that might influence further vaccination strategies in humans. In addition, the potent immunostimulatory action of poxvirus vectors has led to development and evaluation of new-generation vaccine candidates, which will be discussed in this review.

In vivo cellular imaging of lymphocyte trafficking by MRI: A tumor model approach to cell-based anticancer therapy

The aim of this study was to demonstrate the feasibility of in vivo cell tracking to monitor anticancer cell therapy by means of a high-resolution noninvasive MRI method. Ovalbumin-specific splenocytes (OT-1) labeled with anionic gamma-Fe2O3 superparamagnetic iron oxide (SPIO) nanoparticles were adoptively transferred into C57BL/6 mice with growing ovalbumin-expressing tumors. OT-1 cells were tracked in vivo by 7 T MRI 24, 48, and 72 hr after they were injected. The results showed significant negative enhancement of the spleen at 24 hr, and of the tumor at 48 and 72 hr, after labeled cell injection. This suggests that the lymphocytes initially homed toward the spleen and were then recruited by the tumor. The presence of labeled cells was confirmed in ex vivo by 9.4 T microimaging of tumors and magnetic sorting of spleen cells. These results confirm that MR tracking of lymphocytes is feasible in vivo. This high-resolution imaging method could be used to improve the monitoring of immune cell therapy.

Modulation of interleukin-7 receptor expression characterizes differentiation of CD8 T cells specific for HIV, EBV and CMV

OBJECTIVES

To further understand differentiation and homeostasis of CD8 T cells specific for HIV, Epstein-Barr Virus (EBV) and cytomegalovirus (CMV) during HIV infection, we investigated interleukin-7 receptor alpha (IL-7Ralpha) expression on those virus-specific T cells.

METHODS

Microarrays and cytometry analyses were performed on peripheral blood mononuclear cells (PBMC), total and tetramer-binding virus-specific CD8 T cells from 66 HIV-infected patients.

RESULTS

Microarray analysis revealed reduced levels of IL-7Ralpha and increased levels of perforin with disease progression in total PBMC. This loss of IL-7Ralpha expression was observed on CD8 T cells and was inversely related to perforin expression. The relative expression of both molecules defined three new subsets: IL-7Ralpha(pos)Perforin(neg); IL-7Ralpha(loneg)Perforin(lo); and IL-7Ralpha(loneg)Perforin(hi) corresponding to naive and effector-memory CD8 differentiation, as assessed by CD45RA/CD11a. The IL-7Ralpha expression decreased along the CD8 differentiation pathway defined by CD27 and CD28. In contrast, IL-7Ralpha expression was down-modulated on all the CD8 T cells specific for HIV, EBV and CMV that were almost exclusively IL-7Ralpha(lo/neg)Perforin(lo) and was parallel with the CD27 expression. In addition, this low IL-7Ralpha expression on HIV-specific CD8 T cells was independent of virus load and T-cell activation and remained stable during the first 6 months of antiretroviral therapy despite successful control of HIV replication.

CONCLUSION

The relative expression of IL-7Ralpha, perforin reveals new aspects of virus-specific CD8 T cell differentiation, independently of T-cell activation and virus load. This opens new perspectives for understanding homeostasis of those cells and immune-based therapeutic strategies.

Risque de variole, vaccination et bioterrorisme

The use of the smallpox virus as a biological weapon is very old. Confronted with a high probability of a current bioterrorist menace, counteracting strategies have been developed. One of the principle aims relies on the vaccination of teams dedicated to the management of persons infected and the stocking of vaccine for the whole population of a country. Following worldwide eradication of the disease, preventive vaccination was topped in 1978 in France for the primo-vaccination, and in 1984 for repeat vaccinations. The various strains used in the first generation vaccinations are weakened living vaccine, the natural host and origin of which is unknown. Second and third generations vaccines are under study; the principle objective is to obtain efficacy with a minimum of side effects. There are two types of adverse events, generally observed with the first generation vaccines: the first, extremely rare, can be life-threatening; the others, more frequent (10 to 15% of patients) are benign. In emergency situations, in the presence of smallpox, there should be no absolute contraindications to vaccination. In the bioterrorist context, massive vaccination campaigns of the population are unadvisable (because of the considerable risk of death and severe adverse events) in the absence of any real permit, in each case, definition of the vaccinal strategy to be adopted.

The chemokine receptor CX3CR1 controls homing and anti-viral potencies of CD8 effector-memory T lymphocytes in HIV-infected patients

OBJECTIVES

We have recently reported that the polymorphism of the fractalkine receptor, CX3CR1, provides a new marker for prognosis in HIV disease. In order to understand the mechanism by which CX3CR1 participates in the regulation of HIV-immune responses, we investigated its expression and role on T lymphocytes in HIV-infected patients.

DESIGN

For that purpose, we analysed the expression of CX3CR1 on CD4 and CD8 effector-memory subsets in HIV-positive individuals by flow cytometric analyses, and studied its potential role in the migration and function of CD8 effector cells.

RESULTS

We observed an increased frequency of CD8 cells expressing CX3CR1 that was correlated with disease progression in HIV-infected patients compared with normal individuals. CX3CR1+ was expressed mainly on activated and differentiated CCR7-CD45RA-negative memory lymphocytes. Interestingly, CX3CR1 appeared as the main homing receptor of these cells that have downmodulated most other chemokine receptors. The CD8+CX3CR1+ lymphocytes were engaged in the cytotoxic lineage (perforin+, CD27-negative and CD57+). Ex-vivo analysis showed that CX3C ligand-1 inhibits IFNgamma production in response to T cell receptor engagement.

CONCLUSION

CX3CR1 and its ligand could contribute to the specific migratory pattern of late-stage differentiated CD8 cells and participate in the regulation of effector function of CD8 lymphocytes during HIV infection.

Plasticity of lymphoid compartments during HIV infection and treatments: hopes and limits

Immune reconstitution during antiretroviral therapy has recently been shown to depend upon multiple factors at work in T-cell homeostasis, amongst which the reduction of thymus dysfunction and of immune hyperactivation is instrumental. The restoration of host defenses against opportunistic pathogens is, however, balanced by the poor immunity restored against HIV thus giving a satisfying link between antigen stimulation and the reconstitution of immune responses to pathogens.

Differential TCR signaling regulates apoptosis and immunopathology during antigen responses in vivo

Clonal selection theories postulate that lymphocyte fate is regulated by antigen receptor specificity. However, lymphocyte apoptosis is induced through nonantigen-specific receptors such as Fas (CD95/APO-1) or TNFR. We define a selective TCR that controls apoptosis by Fas or TNFR stimulation. Variant ligands can deliver this "competence to die" signal without the full TCR signals necessary for cytokine synthesis. These partial agonists regulate T cell deletion in vivo even when Fas or TNF is provided by T cells of unrelated specificity, but they do not cause the liver necrosis that is associated with T cell elimination by the full agonist. Thus, selective signaling ligands regulate T cell deletion and immune damage in vivo and may be important for peripheral T cell tolerance.

Selective induction of apoptosis in mature T lymphocytes by variant T cell receptor ligands

Activation, anergy, and apoptosis are all possible outcomes of T cell receptor (TCR) engagement. The first leads to proliferation and effector function, whereas the others can lead to partial or complete immunological tolerance. Structural variants of immunizing peptide-major histocompatibility complex molecule ligands that induce selective lymphokine secretion or anergy in mature T cells in association with altered intracellular signaling events have been described. Here we describe altered ligands for mature mouse CD4(+) T helper 1 cells that lead to T cell apoptosis by the selective expression of Fas ligand (FasL) and tumor necrosis factor (TNF) without concomitant IL-2, IL-3, or interferon gamma production. All ligands that stimulated cell death were found to induce FasL and TNF mRNA expression and TCR aggregation ("capping") at the cell surface, but did not elicit a common pattern of tyrosine phosphorylation of the TCR-associated signal transduction chains. Thus, TCR ligands that uniquely trigger T cell apoptosis without inducing cytokines that are normally associated with activation can be identified.

Qualitative and quantitative contributions of the T cell receptor zeta chain to mature T cell apoptosis

Engagement of the T cell receptor (TCR) of mature T lymphocytes can lead either to activation/proliferation responses or programmed cell death. To understand the molecular regulation of these two fundamentally different outcomes of TCR signaling, we investigated the participation of various components of the TCR-CD3 complex. We found that the TCR-zeta chain, while not absolutely required, was especially effective at promoting mature T cell apoptosis compared with the CD3 epsilon, gamma, or delta chains. We also carried out mutagenesis to address the role of the immunoreceptor tyrosine-based activation motifs (ITAMs) that are the principal signaling components found three times in the TCR-zeta chain and once in each of the CD3 epsilon, gamma, or delta chains. We found that the ability of the TCR-zeta chain to promote apoptosis results both from a quantitative effect of the presence of multiple ITAMs as well as qualitatively different contributions made by individual ITAMs. Apoptosis induced by single chain chimeras revealed that the first zeta ITAM stimulated greater apoptosis than the third zeta ITAM, and the second zeta ITAM was unable to trigger apoptosis. Because microheterogeneity in the amino acid sequence of the various ITAM motifs found in the TCR-zeta and CD3 chains predicts interactions with distinct src-homology-2-domain signaling proteins, our results suggest the possibility that individual ITAM motifs might play unique roles in TCR responses by engaging specific signaling pathways.