A Crucial Role for Infected-Cell/Antibody Immune Complexes in the Enhancement of Endogenous Antiviral Immunity by Short Passive Immunotherapy

Antiviral monoclonal antibodies (mAbs) represent promising therapeutics. However, most mAbs-based immunotherapies conducted so far have only considered the blunting of viral propagation and not other possible therapeutic effects independent of virus neutralization, namely the modulation of the endogenous immune response. As induction of long-term antiviral immunity still remains a paramount challenge for treating chronic infections, we have asked here whether neutralizing mAbs can, in addition to blunting viral propagation, exert immunomodulatory effects with protective outcomes. Supporting this idea, we report here that mice infected with the FrCas^E murine retrovirus on day 8 after birth die of leukemia within 4–5 months and mount a non-protective immune response, whereas those rapidly subjected to short immunotherapy with a neutralizing mAb survive healthy and mount a long-lasting protective antiviral immunity with strong humoral and cellular immune responses. Interestingly, the administered mAb mediates lysis of infected cells through an antibody-dependent cell cytotoxicity (ADCC) mechanism. In addition, it forms immune complexes (ICs) with infected cells that enhance antiviral CTL responses through FcγR-mediated binding to dendritic cells (DCs). Importantly, the endogenous antiviral antibodies generated in mAb-treated mice also display the same properties, allowing containment of viral propagation and enhancement of memory cellular responses after disappearance of the administered mAb. Thus, our data demonstrate that neutralizing antiviral mAbs can act as immunomodulatory agents capable of stimulating a protective immunity lasting long after the end of the treatment. They also show an important role of infected-cells/antibody complexes in the induction and the maintenance of protective immunity through enhancement of both primary and memory antiviral T-cell responses. They also indicate that targeting infected cells, and not just viruses, by antibodies can be crucial for elicitation of efficient, long-lasting antiviral T-cell responses. This must be considered when designing antiviral mAb-based immunotherapies.     

Long-Lasting Protective Antiviral Immunity Induced by Passive Immunotherapies Requires both Neutralizing and Effector Functions of the Administered Monoclonal Antibody

Using FrCas^E retrovirus-infected newborn mice as a model system, we have shown recently that a long-lasting antiviral immune response essential for healthy survival emerges after a short treatment with a neutralizing (667) IgG2a isotype monoclonal antibody (MAb). This suggested that the mobilization of adaptive immunity by administered MAbs is key for the success in the long term for the MAb-based passive immunotherapy of chronic viral infections. We have addressed here whether the anti-FrCas^E protective endogenous immunity is the mere consequence of viral propagation blunting, which would simply give time to the immune system to react, and/or to actual immunomodulation by the MAb during the treatment. To this aim, we have compared viral replication, disease progression, and antiviral immune responses between different groups of infected mice: (i) mice treated with either the 667 MAb, its F(ab′)₂ fragment, or an IgM (672) with epitopic specificity similar to that of 667 but displaying different effector functions, and (ii) mice receiving no treatment but infected with a low viral inoculum reproducing the initial viral expansion observed in their infected/667 MAb-treated counterparts. Our data show that the reduction of FrCas^E propagation is insufficient on its own to induce protective immunity and support a direct immunomodulatory action of the 667 MAb. Interestingly, they also point to sequential actions of the administered MAb. In a first step, viral propagation is exclusively controlled by 667 neutralizing activity, and in a second one, this action is complemented by FcγR-binding-dependent mechanisms, which most likely combine infected cell cytolysis and the modulation of the antiviral endogenous immune response. Such complementary effects of administered MAbs must be taken into consideration for the improvement of future antiviral MAb-based immunotherapies.Although monoclonal antibodies (MAbs) principally have been considered for anticancer applications heretofore (62, 64), they now are increasingly being considered to treat severe acute and chronic viral infections (43, 63, 83). The best-studied antiviral MAbs are (i) pavalizumab, a humanized anti-respiratory syncytial virus (RSV) MAb approved by the FDA in 1998 for treating severe lower-respiratory-tract diseases in infants (45); (ii) several anti-human immunodeficiency virus (HIV) MAbs, which have been used in macaque preclinical infection models and in several human trials (4, 5, 19, 27-30, 32, 42, 50, 55, 57, 76-79); and (iii) a few anti-hepatitis C virus (HCV) MAbs, some of which currently are being tested in humans (9, 22, 40). However, other MAbs, some of them of human origin, also have been generated against other human viruses in recent years. Among them are antibodies against Ebola virus (75), West Nile virus (WNV) (48, 53, 54), cytomegalovirus (CMV) (11), avian and human influenza viruses (59, 60, 73, 74), severe acute respiratory syndrome coronavirus (SARS CoV) (81), hepatitis B virus (HBV) (31, 35), Hanta virus (80, 82), and Nipah virus (80, 82). These antiviral MAbs all have been selected on the basis of their neutralizing activity and the possibility that they interfere with the antiviral immune response of treated hosts, because their effector functions have been considered surprisingly little so far. Addressing this question in clinical settings currently is not possible for a variety of reasons that include ethical, technical, and cost concerns. Therefore, we have turned to the neonatal infection of mice by the lethal FrCas^E retrovirus as a model system. This model allowed us to show that a very short immunotherapy by a neutralizing MAb of the IgG2a isotype (667 MAb) can permit, in addition to an immediate direct effect on the viral load, the mounting of a long-lasting endogenous antiviral immunity, which is essential for viral control and healthy survival (23-25). Because of the broad therapeutic perspectives opened by this observation, it now is essential to elucidate the molecular and cellular mechanisms underlying this effect.FrCas^E is a simple chimeric mouse retrovirus in which the env gene of the leukemogenic Friend murine leukemia virus (F-MuLV) was replaced by that of the neurodegeneration-inducing CasBr retrovirus (58). When 5 × 10⁴ infectious particles are inoculated into newborn mice under the age of 5 to 6 days, FrCas^E can enter the central nervous system (CNS) and induces a neurodegeneration fatal within 1 to 2 months with 100% incidence (15, 23, 41, 58). However, upon infection at a later time, FrCas^E can no longer enter the CNS. Instead, it replicates only in the periphery and gives rise to a fatal erythroleukemia preceded by spleen enlargement and a dramatic drop of the hematocrit. Erythroleukemia incidence and incubation period, however, are variable, depending on the inoculum and the date of infection (46).667 is an IgG2a/κ (44) directed to the main viral receptor-binding site of CasBr Env (16). It displays both in vitro (44) and in vivo (56) neutralizing activities. When rapidly (<2 days) administered for a few days to neonatally FrCas^E-infected pups, viral propagation is rapidly blunted, which prevents virus entry in the brain and subsequent neurodegeneration (23). Moreover, all 667-treated mice develop a strong, long-lasting antiviral immune response, which is necessary for them to survive healthy and with no sign of neurodegeneration or of erythroleukemia (23-25) and to resist viral challenges carried out as long as 14 months after first infection (23). Protective antiviral immunity is of a typical TH1 type with humoral and cytotoxic T-cell (CTL) contributions. The anti-FrCas^E humoral contribution is high, sustained, and principally of the IgG2a type with both in vitro neutralization- and complement-dependent cytolysis activities (23). Interestingly, it shows typical secondary response characteristics in viral challenge experiments (23), and anti-FrCas^E antibodies are transmitted transplacentally and through breastfeeding by mothers to children, where they manifest the same properties as those of 667 in the perinatal infection setting, i.e., they prevent mice from developing neurodegeneration and permit the induction of an endogenous protective antiviral immune response (25). Finally, the CTL response directed to infected cells was shown to be necessary for the protection of FrCas^E-infected, 667-treated mice, as the depletion of CD8⁺ T cells leads to death by retrovirally induced erythroleukemia (24).At this stage, an important issue is the clarification of whether the anti-FrCas^E protective immunity seen in 667 MAb-treated mice is due to actual immunomodulation by the MAb owing to its effector function(s) and/or is the consequence of viral propagation blunting, which would prevent the immune system from being overwhelmed by an excess of antigen and, hence, would give it time to react optimally. To address these two nonexclusive possibilities, we compared here viral propagations, health statuses, and endogenous immune responses in four groups of mice. The first three groups were mice neonatally infected under standard conditions (5 × 10⁴ infectious particles) and treated with either the natural 667 MAb, the antibody effector function-lacking F(ab′)₂ fragment of 667, or a neutralizing IgM (672) with effector functions inherently different from those of 667. The last group consisted of mice neonatally infected with a low FrCas^E inoculum but not subjected to immunotherapy, which is a condition permitting early viral propagation kinetics similar to those of animals infected and 667 MAb treated under standard conditions. Taken together, our data indicate that the drastic reduction of viral propagation shortly after infection is not sufficient for the induction of protective adaptive immunity and, thereby, point to an immunomodulatory action of 667. Interestingly, they also point to two sequential actions of the administered MAb. In the immediate postinfection period, viral spread is controlled exclusively by 667 neutralizing activity, and later it involves the cytolysis of infected cells owing to FcγR-binding-dependent mechanisms. Finally, our work shows that not all antibody isotypes are equally efficient at protecting infected mice and favoring the mounting of protective immunity, as 672 IgM immunotherapy-treated animals died of erythroleukemia.     

Efficient mother-to-child transfer of antiretroviral immunity in the context of preclinical monoclonal antibody-based immunotherapy

When mice under the age of 5 to 6 days are infected, the FrCas(E) retrovirus induces a neurodegenerative disease leading to death within 1 to 2 months. We have recently reported that transient treatment with a neutralizing monoclonal antibody (MAb) shortly after infection, in addition to an expected immediate decrease in the viral load, also favors the development of a strong protective immune response that persists long after the MAb has been cleared. This observation may have important therapeutic consequences, as it suggests that MAbs might be used, not only as direct neutralizing agents, but also as immunomodulatory agents enabling patients to mount their own antiviral immune responses. We have investigated whether immunoglobulins from mothers who displayed a strong anti-FrCas(E) humoral response induced upon MAb treatment could affect both viremia and the immune systems of FrCas(E)-infected pups till adult age upon placental and/or breastfeeding transfer. The strongest effects, i.e., reduction in the viral load and induction of protective humoral antiviral responses, were observed upon breastfeeding alone and breastfeeding plus placental immunity transfer. However, placental transfer of anti-FrCas(E) antibodies was sufficient to both protect neonatally infected animals and help them initiate a neutralizing anti-FrCas(E) response. Also, administration of a neutralizing MAb to naive mothers during late gestation and breastfeeding could generate similar effects. Taken together, our data support the concept that passive immunotherapies during late gestation and/or breastfeeding might help retrovirally infected neonates prime their own protective immune responses, in addition to exerting an immediate antiviral effect.     

Induction of long-term protective antiviral endogenous immune response by short neutralizing monoclonal antibody treatment

Long-term immune control of viral replication still remains a major challenge in retroviral diseases. Several monoclonal antibodies (MAbs) have already shown antiviral activities in vivo, including in the clinic but their effects on the immune system of treated individuals are essentially unknown. Using the lethal neurodegeneration induced in mice upon infection of neonates by the FrCas(E) retrovirus as a model, we report here that transient treatment by a neutralizing MAb shortly after infection can, after an immediate antiviral effect, favor the development of a strong protective host immune response containing viral propagation long after the MAb has disappeared. In vitro virus neutralization- and complement-mediated cell lysis assays, as well as in vivo viral challenges and serum transfer experiments, indicate a clear and essential contribution of the humoral response to antiviral protection. Our observation may have important therapeutic consequences as it suggests that short antibody-based therapies early after infection should be considered, at least in the case of maternally infected infants, as adjunctive treatment strategies against human immunodeficiency virus, not only for a direct effect on the viral load but also for favoring the emergence of an endogenous antiviral immune response.     

Neonatal vaccination against respiratory syncytial virus infection

Respiratory syncytial virus (RSV) is the leading cause of pneumonia and bronchiolitis in infants and is the most frequent cause of lower respiratory tract infections in children.Efficacious vaccination...     

Protective Role of the Virus-Specific Immune Response for Development of Severe Neurologic Signs in Simian Immunodeficiency Virus-Infected Macaques

The pathogenesis of human immunodeficiency virus-associated motor and cognitive disorders is poorly understood. In this context both a protective and a harmful role of the immune system has been discussed. This question was addressed in the present study by correlating the occurrence of neurologic disease in simian immunodeficiency virus (SIV)-infected macaques with disease progression and the humoral and cellular intrathecal antiviral immune response. Overt neurologic signs consisting of ataxia and apathy were observed at a much higher frequency in rapid progressor animals (6 of 12) than in slow progressors (1 of 7). Whereas slow progressors mounted a strong antiviral antibody (Ab) response as evidenced by enzyme-linked immunosorbent and immunospot assays, neither virus-specific Ab titers nor Ab-secreting cells could be found in the cerebrospinal fluid (CSF) or brain parenchyma of rapid progressors. Similarly, increased infiltration of CD8⁺ T cells and cytotoxic T lymphocytes specific for viral antigens were detected only in the CSF of slow progressors. The finding that neurologic signs develop frequently in SIV-infected macaques in the absence of an antiviral immune response demonstrates that the immune system does not contribute to the development of motor disorders in these animals. Moreover, the lower incidence of neurologic symptoms in slow progressors with a strong intrathecal immune response suggests a protective role of the virus-specific immunity in immunodeficiency virus-induced central nervous system disease.     

IL-17作为分子佐剂增强蛋白疫苗细胞免疫应答的研究

目的:为了进一步增强重组蛋白质疫苗的细胞免疫应答,利用重组的IL-17作为分子佐剂,与卵清蛋白(ovalbumin,OVA)一起免疫小鼠,研究IL-17作为分子佐剂对适应性免疫的影响,探索IL-17对蛋白疫苗诱导的免疫反应,特别是细胞免疫应答的影响.方法:用OVA作为特异性蛋白疫苗,与不同剂量的IL-17联合免疫C57...     

Viral escape from the neutralizing antibody response: the lymphocytic choriomeningitis virus model

In addition to CD8+ cytotoxic T lymphocyte (CTL) responses, neutralizing antibodies contribute substantially to the long-term immune control of noncytopathic viruses, as demonstrated during infection with the lymphocytic choriomeningitis virus (LCMV). The high virus load during the initial phase of an infection and the ability of this RNA virus to spontaneously acquire mutations are important prerequisites for escaping an ongoing immune response. In this context, LCMV escape from the humoral response by single point mutations in neutralizing envelope protein determinants may occur, particularly during conditions of CTL deficiency, leading to virus persistence.     

Perforin and Fas cytolytic pathways coordinately shape the selection and diversity of CD8+-T-cell escape variants of influenza virus

Antigenic variation is a viral strategy exploited to promote survival in the face of the host immune response and represents a major challenge for efficient vaccine development. Influenza viruses are pathogens with high transmissibility and mutation rates, enabling viral escape from immunity induced by prior infection or vaccination. Intense selection from neutralizing antibody drives antigenic changes in the surface glycoproteins, resulting in emergence of new strains able to reinfect hosts immune to previously circulating viruses. CD8+ cytotoxic T cells (CTLs) also provide protective immunity from influenza virus infection and may contribute to the antigenic evolution of influenza viruses. Utilizing mice transgenic for an influenza virus NP366-374 peptide-specific T-cell receptor, we demonstrated that the respiratory tract is a suitable site for generation of escape variants of influenza virus selected by CTL in vivo. In this report the contributions of the perforin and Fas pathways utilized by influenza virus-specific CTLs in viral clearance and selection of CTL escape variants have been evaluated. While transgenic CTLs deficient in either perforin- or Fas-mediated pathways are efficient in initial pulmonary viral control, variant virus emergence was observed in all the mice studied, although the spectrum of viral CTL escape variants selected varied profoundly. Thus, a less-restricted repertoire of escape variants was observed in mice with an intact perforin cytotoxic pathway compared with a limited variant diversity in perforin pathway-deficient mice, although maximal variant diversity was observed in mice having both Fas and perforin pathways intact. We conclude that selection of viral CTL escape variants reflects coordinate action between the tightly controlled perforin/granzyme pathway and the more promiscuous Fas/FasL pathway.     

Rectification of age-associated deficiency in cytotoxic T cell response to influenza A virus by immunization with immune complexes

Decline in cellular immunity in aging compromises protection against infectious diseases and leads to the increased susceptibility of the elderly to infection. In particular, Ag-specific cytotoxic T lymphocyte (CTL) response against virus is markedly reduced in an aged immune system. It is of great importance to explore novel strategy in eliciting effective antiviral CTL activity in the elderly. In this study, the efficacy and mechanisms of immunization with immune complexes in overcoming age-associated deficiency in cellular immunity were investigated. In this study, we show that the severely depressed CTL response to influenza A in aged mice can be significantly restored by immunization with immune complexes consisting of influenza A virus and mAb to influenza A nucleoprotein. The main mechanisms underlying this recovery of CTL response induced by immune complex immunization in aged mice are enhanced dendritic cell function and elevated production of IFN-gamma in both CD4(+) Th1 and CD8(+) CTLs. Thus, these results demonstrate that immune complex immunization may represent a novel strategy to elicit effective virus-specific cytotoxic response in an aged immune system, and possibly, to overcome age-related immune deficiency in general.     

Killer dendritic cells and their potential for cancer immunotherapy

Known for years as the principal messengers of the immune system, dendritic cells (DC) represent a heterogeneous population of antigen presenting cells critically located at the nexus between innate and adaptive immunity. DC play a central role in the initiation of tumor-specific immune responses as they are endowed with the unique ability to take up, process and present tumor antigens to naïve CD4⁺ or CD8⁺ effector T lymphocytes. By virtue of the cytokines they produce, DC also regulate the type, strength and duration of T cell immune responses. In addition, they can participate in anti-tumoral NK and NKT cell activation and in the orchestration of humoral immunity. More recent studies have documented that besides their primary role in the induction and regulation of adaptive anti-tumoral immune responses, DC are also endowed with the capacity to directly kill cancer cells. This dual role of DC as killers and messengers may have important implications for tumor immunotherapy. First, the direct killing of malignant cells by DC may foster the release and thereby the immediate availability of specific tumor antigens for presentation to cytotoxic or helper T lymphocytes. Second, DC may participate in the effector phase of the immune response, potentially augmenting the diversity of the killing mechanisms leading to tumor elimination. This review focuses on this non-conventional cytotoxic function of DC as it relates to the promotion of cancer immunity and discusses the potential application of killer DC (KDC) in tumor immunotherapy.     

Adoptive immunotherapy of HCMV infection

Human cytomegalovirus (HCMV) infection or reactivation is a frequent cause of morbidity and mortality in immunocompromised individuals such as transplant recipients. Primary HCMV infection or reactivation of HCMV from latency is mostly asymptomatic in immunocompetent individuals and is controlled by the host's cell-mediated immune response. Healthy HCMV seropositive individuals develop high frequencies of HCMV-specific cytotoxic T lymphocytes (CTL) in the peripheral blood. Furthermore, a direct correlation between the recovery of HCMV-specific CTL responses and an improved outcome of HCMV disease could be demonstrated in immunocompromised patients. Deriving from these observations, the strategy of an adoptive transfer of HCMV-specific T cells has been developed. Protective immunity can be transferred successfully by the infusion of donor-derived HCMV-specific CD8+ cytotoxic T-cell clones or cell lines. In addition, several studies have supported the importance of antiviral effector functions of Th cells in maintaining CTL responses after adoptive transfer and their capacity to produce antiviral cytokines. Until today, a broad variety of clinical protocols for HCMV-specific immunotherapy has been published. These protocols vary regarding the isolation procedure, composition of cellular product, number of transferred cells and thus treatment efficacy. In this review, we aim to provide a comprehensive synopsis of the current standard of knowledge concerning cellular HCMV-specific immunotherapeutic approaches.     

Rotavirus anti-VP6 secretory immunoglobulin A contributes to protection via intracellular neutralization but not via immune exclusion

Immunoglobulin A (IgA) monoclonal antibodies (MAbs) directed at the conserved inner core protein VP6 of rotavirus, such as the IgA7D9 MAb, provide protective immunity in adult and suckling mice when delivered systemically. While these antibodies do not have traditional in vitro neutralizing activity, they could mediate their antiviral activity either by interfering with the viral replication cycle along the IgA secretory pathway or by acting at mucosal surfaces as secretory IgA and excluding virus from target enterocytes. We sought to determine the critical step at which antirotaviral activity was initiated by the IgA7D9 MAb. The IgA7D9 MAb appeared to directly interact with purified triple-layer viral particles, as shown by immunoprecipitation and immunoblotting. However, protection was not conferred by passively feeding mice with the secretory IgA7D9 MAb. This indicates that the secretory IgA7D9 MAb does not confer protection by supplying immune exclusion activity in vivo. We next evaluated the capacity of polymeric IgA7D9 MAb to neutralize rotavirus intracellularly during transcytosis. We found that when polymeric IgA7D9 MAb was applied to the basolateral pole of polarized Caco-2 intestinal cells, it significantly reduced viral replication and prevented the loss of barrier function induced by apical exposure of the cell monolayer to rotavirus, supporting the conclusion that the antibody carries out its antiviral activity intracellularly. These findings identify a mechanism whereby the well-conserved immunodominant VP6 protein can function as a target for heterotypic antibodies and protective immunity.     

An mRNA vaccine encoding Chikungunya virus E2-E1 protein elicits robust neutralizing antibody responses and CTL immune responses

Arthropod-borne chikungunya virus (CHIKV) infection can cause a debilitating arthritic disease in human. However, there are no specific antiviral drugs and effective licensed vaccines against CHIKV available for clinical use. Here, we developed an mRNA-lipid nanoparticle (mRNA-LNP) vaccine expressing CHIKV E2-E1 antigen, and compared its immunogenicity with soluble recombinant protein sE2-E1 antigen expressed in S2 cells. For comparison, we first showed that recombinant protein antigens mixed with aluminum adjuvant elicit strong antigen-specific humoral immune response and a moderate cellular immune response in C57BL/6 mice. Moreover, sE2-E1 vaccine stimulated 12-23 folds more neutralizing antibodies than sE1 vaccine and sE2 vaccine. Significantly, when E2-E1 gene was delivered by an mRNA-LNP vaccine, not only the better magnitude of neutralizing antibody responses was induced, but also greater cellular immune responses were generated, especially for CD8⁺ T cell responses. Moreover, E2-E1-LNP induced CD8⁺ T cells can perform cytotoxic effect in vivo. Considering its better immunogenicity and convenience of preparation, we suggest that more attention should be placed to develop CHIKV E2-E1-LNP mRNA vaccine.     

Identification of new prostate stem cell antigen-derived peptides immunogenic in HLA-A2<Superscript>+</Superscript> patients with hormone-refractory prostate cancer

Purpose Prostate cancer refractory to hormonal manipulation requires new treatment modalities. In the present study we attempted to identify prostate stem cell antigen (PSCA)-derived peptides immunogenic in HLA-A2⁺ prostate cancer patients in order to develop peptide-based immunotherapy against hormone-refractory prostate cancer (HRPC).Methods Eleven different PSCA-derived peptides, which were prepared based on the HLA-A2 binding motif, were examined to determine whether they would be recognized by cellular and humoral immune responses in 12 HLA-A2⁺ patients (11 with HRPC and 1 with non-HRPC).Results Among the PSCA-derived peptides, PSCA 7–15 and PSCA 21–30 peptides effectively induced HLA-A2-restricted peptide-specific and tumor-reactive cytotoxic T lymphocytes (CTLs) from peripheral blood mononuclear cells (PBMCs) of HLA-A2⁺ patients. The PSCA 21–30 peptide was capable of inducing peptide-specific CTLs in both cancer patients and healthy donors, whereas the PSCA 7–15 peptide was immunogenic in only cancer patients. Immunoglobulin G (IgG) reactive to the PSCA 21–30 peptide was detected in plasma of most patients and healthy donors, whereas IgG reactive to PSCA 7–15 was undetectable in all cases. These results indicate that the former peptide elicits both cellular and humoral immune responses in both patients and healthy donors, whereas the latter elicits only cellular responses in patients.Conclusion These two PSCA peptides should be considered for use in clinical trials of immunotherapy for HLA-A2⁺ HRPC patients.     

乙型肝炎病毒特异性细胞毒性T淋巴细胞在病毒清除过程中的作用

在乙型肝炎病毒(HBV)感染过程中,适应性免疫与病毒的致病和清除密切相关。一般认为,体液免疫产生的抗体可以清除外周循环的病毒颗粒,从而阻止病毒在宿主体内的传播,细胞免疫主要清除被感染细胞中的病毒。HBV特异性的细胞毒性T淋巴细胞(CTL)在抑制HBV复制过程中发挥着重要的作用。CTL在肝内主要通过分泌γ干扰素抑制病毒,同时,当CTL识别HBV抗原后,HBV特异性CTL募集抗原非特异性炎症细胞对肝组织浸润,造成肝细胞的损伤。对CTL抗病毒作用进行深入研究,将为乙型肝炎的治疗开辟新的途径。     

Herpes simplex virus type 1-specific immunity induced by peptides corresponding to an antigenic site of glycoprotein B.

Herpes simplex virus (HSV) envelope glycoproteins are the prime targets of adaptive antiviral immunity. Previous investigation identified a protective, neutralizing, glycoprotein B1 (gB-1)-reactive monoclonal antibody (MAb B6) and localized the linear epitope recognized by the MAb to residue 84 of gB-1. Three overlapping peptides (two 20-mers and one 18-mer), together spanning amino acids 63 to 110 of the wild-type sequence of gB-1, were synthesized and analyzed for their ability to stimulate immunity which cross-reacts with HSV-1. All stimulated some level of response. Two peptides, the gB 18-mer and 20.1-mer, were recognized by MAb B6 and HSV-immune antibody but were unable to stimulate virus-neutralizing antibody or serum able to protect against zosteriform spread in vivo. The 20.2-mer peptide, however, which was not recognized by MAb B6 or HSV-generated immune antibody, stimulated the production of neutralizing antibody and serum able to protect against zosteriform spread. Immunization with all of the peptides was able to enhance viral clearance of a low dose of HSV-1 in an ear challenge model and induce antibody reactive in antibody-dependent complement-mediated lysis of HSV-1-infected cells in vitro. These results are the first report of HSV immunity induced by peptides corresponding to gB and indicate that the best immunogen, in terms of stimulating neutralizing antiserum able to protect in vivo against HSV-1, was a peptide not recognized by HSV-immune mechanisms or by the MAb used to localize it.     

Kinetic Analysis of the Specific Host Response to a Murine Gammaherpesvirus

Respiratory infection of BALB/c mice with the murine gammaherpesvirus 68 (MHV-68) induces the clonal expansion of virus-specific cytotoxic T-lymphocyte (CTL) precursors (CTLp) in the regional, mediastinal lymph nodes (MLN). Some of these CTLps differentiate to become fully functional CTL effectors, which can be detected in both the lymphoid tissue and in the site of pathology in the lung. Though the lymph nodes and spleen harbor substantial populations of latently infected B cells for life, the level of virus-specific CTL activity decreases rapidly in all sites. The CD8⁺ CTLp numbers fall to background levels in the MLN within several months of the termination of the productive phase of MHV-68 infection in the respiratory epithelium but are maintained at relatively low frequency in the spleen. The continued presence of a gamma interferon-producing, MHV-68-specific CD4⁺ set can also be demonstrated in cultured spleen cells. The virus-specific immunoglobulin G (IgG) response is slow to develop, with serum neutralizing antibody and enzyme-linked immunosorbent assay titers continuing to rise for several months. The level of total serum IgG increases dramatically within 2 weeks of infection, probably as a consequence of polyclonal B-cell activation, and remains high. The immune response profile is clearly influenced by the persistence of this DNA virus.     

A20 Deficiency in Lung Epithelial Cells Protects against Influenza A Virus Infection

A20 negatively regulates multiple inflammatory signalling pathways. We here addressed the role of A20 in club cells (also known as Clara cells) of the bronchial epithelium in their response to influenza A virus infection. Club cells provide a niche for influenza virus replication, but little is known about the functions of these cells in antiviral immunity. Using airway epithelial cell-specific A20 knockout (A20^AEC-KO) mice, we show that A20 in club cells critically controls innate immune responses upon TNF or double stranded RNA stimulation. Surprisingly, A20^AEC-KO mice are better protected against influenza A virus challenge than their wild type littermates. This phenotype is not due to decreased viral replication. Instead host innate and adaptive immune responses and lung damage are reduced in A20^AEC-KO mice. These attenuated responses correlate with a dampened cytotoxic T cell (CTL) response at later stages during infection, indicating that A20^AEC-KO mice are better equipped to tolerate Influenza A virus infection. Expression of the chemokine CCL2 (also named MCP-1) is particularly suppressed in the lungs of A20^AEC-KO mice during later stages of infection. When A20^AEC-KO mice were treated with recombinant CCL2 the protective effect was abrogated demonstrating the crucial contribution of this chemokine to the protection of A20^AEC-KO mice to Influenza A virus infection. Taken together, we propose a mechanism of action by which A20 expression in club cells controls inflammation and antiviral CTL responses in response to influenza virus infection.     

The antiviral efficacy of HIV-specific CD8⁺ T-cells to a conserved epitope is heavily dependent on the infecting HIV-1 isolate

A major challenge to developing a successful HIV vaccine is the vast diversity of viral sequences, yet it is generally assumed that an epitope conserved between different strains will be recognised by responding T-cells. We examined whether an invariant HLA-B8 restricted Nef_90–97 epitope FL8 shared between five high titre viruses and eight recombinant vaccinia viruses expressing Nef from different viral isolates (clades A–H) could activate antiviral activity in FL8-specific cytotoxic T-lymphocytes (CTL). Surprisingly, despite epitope conservation, we found that CTL antiviral efficacy is dependent on the infecting viral isolate. Only 23% of Nef proteins, expressed by HIV-1 isolates or as recombinant vaccinia-Nef, were optimally recognised by CTL. Recognition of the HIV-1 isolates by CTL was independent of clade-grouping but correlated with virus-specific polymorphisms in the epitope flanking region, which altered immunoproteasomal cleavage resulting in enhanced or impaired epitope generation. The finding that the majority of virus isolates failed to present this conserved epitope highlights the importance of viral variance in CTL epitope flanking regions on the efficiency of antigen processing, which has been considerably underestimated previously. This has important implications for future vaccine design strategies since efficient presentation of conserved viral epitopes is necessary to promote enhanced anti-viral immune responses.