Antibody and memory CD4 T-cell responses after meningococcal disease

Currently, Neisseria meningitidis serogroup C (MenC) is the major cause of bacterial meningitis in Brazil, affecting mainly teenagers and adults due to the lack of routine public vaccination of these age groups. The goal of this study was to investigate the bactericidal antibody response and the development of CD4⁺ T cell memory during the convalescent phase of patients infected with N. menigitidis. Most (85.7%) of the patients developed a protective antibody response against MenC and 57% also responded to N. meningitidis serogroup B. We detected a significant CD4⁺ T central memory (T_CM) response to meningococcal outer membrane proteins.     

CD4+ and CD8+ mediated cellular immune response to recombinant influenza nucleoprotein

The stimulatory properties of soluble recombinant influenza nucleoprotein (NP) on purified CD4(+) and CD8(+) T cells from young and elderly individuals were studied. Recombinant influenza NP failed to induce proliferation of resting CD4(+) and CD8(+) T cells in the absence of IL-2. Addition of small amounts of IL-2, however, led to strong proliferation of resting CD4(+) and CD8(+) T cells from young and elderly donors. NP-reactive CD4(+) and CD8(+) T cell lines from both age groups grew equally well under long-term culture conditions. T cell lines raised to live influenza virus could recognize recombinant influenza NP and showed a substantial proliferative response. Stimulation of CD8(+) T cells is presumably due to cross-presentation, as EBV-transformed MHC class I-positive cell lines, which are incapable of antigen processing, stimulated live influenza virus-reactive CD8(+) T cell lines when loaded with NP-derived immunodominant peptides but not following loading with the whole NP molecule. Vaccines containing recombinant influenza NP might confer cross-protective immunity and could therefore be especially useful in cases of major epidemics or pandemics.     

Liposome-encapsulated HIV-1 Gag p24 containing lipid A induces effector CD4+ T-cells,memory CD8+ T-cells,and pro-inflammatory cytokines

Liposomal lipid A is an effective adjuvant for the delivery of antigens and for the induction of both cellular and humoral immunity. In this study, we demonstrate that following the third immunization with HIV-1 Gag p24 encapsulated in liposomes containing lipid A [L(p24 + LA)], central memory CD8+ T-cells were localized in the spleen and lymph nodes of mice while effector memory CD8+ T-cells and effector CD4+ T-cells were found in the PBMC. Effector CD4+ T-cells were also detected in the spleen and lymph nodes. The predominant cytokine secreted from splenic lymphocytes and lymph nodes was IFN-γ. In contrast, IL-6 and IL-10 were the major cytokines produced from PBMC. The peptide stimulation indicated that the cytokine responses observed were T-cell specific. The results demonstrate the importance of the adjuvant liposomal lipid A for the induction of HIV-1 Gag p24 -specific CD8+ T-cells, effector CD4+ T-cells, and cytokines with a Th-1 type profile after immunization with L(p24 + LA).     

Human antibody and memory B and T-cell responses after primary and booster immunisation against Neisseria meningitidis B

Vaccination against disease aims at the induction of long-lasting cellular and humoral immune responses. Few studies have addressed the mechanisms by which meningococcal vaccines generate and sustain immunological memory. The goal of this study was to investigate the development of long-term humoral and cellular memory to Neisseria meningitidis serogroup B (MenB) in health subjects after immunisation with the Cuban outer membrane protein (OMP) vaccine (VA-MENGOC-BC^®). The results showed that three doses of vaccine were necessary to induce a detectable memory B-cell response (mean of 0.46%) which became undetectable 6 months later. After boosting, only 2 of 5 individuals responded with an increase in memory B-cell frequencies (values of 0.15% and 0.34%). Bactericidal and opsonic antibody levels were higher after primary immunisation (log₂ mean and median of 4.7 and 1212, respectively) when compared with post-booster response (log₂ mean of 2.6 and median of 285, respectively). Together, these data suggest a failure of vaccine to induce long-term memory B-cell and serological memory in adults. However, we observed a significant and functional memory T-cell response specially after boosting, with a predominance of activated (CD69⁺) central memory T-cell (CD4⁺CD45⁻CCR7⁺) response. Therefore, this study suggests that vaccination with the MenB vaccine induced the generation and activation of memory T-cells but failed to maintain the memory B-cell population at a stable size and/or function.     

Phenotype of the anti-Rickettsia CD8 T cell response suggests cellular correlates of protection for the assessment of novel antigens

The obligately intracellular bacteria Rickettsia infect endothelial cells and cause systemic febrile diseases that are potentially lethal. No vaccines are currently available and current knowledge of the effective immune response is limited. Natural and experimental rickettsial infections provide strong and cross-protective cellular immunity if the infected individual survives the acute infection. Although resistance to rickettsial infections is attributed to the induction of antigen-specific T cells, particularly CD8⁺ T cells, the identification and validation of correlates of protective cellular immunity against rickettsial infections, an important step toward vaccine validation, remains a gap in this field. Here, we show that after a primary challenge with Rickettsia typhi in the C3H mouse model, the peak of anti-Rickettsia CD8⁺ T cell-mediated responses occurs 7 days post-infection (dpi), which coincides with the beginning of rickettsial clearance. At this time point, both effector-type and memory-type CD8⁺ T cells are present, suggesting that 7 dpi is a valid time point for the assessment of CD8⁺ T cell responses of mice previously immunized with protective antigens. Based on our results, we suggest four correlates of cellular protection for the assessment of protective rickettsial antigens: (1) production of IFN-γ by antigen-experienced CD3⁺CD8⁺CD44^high cells, (2) production of Granzyme B by CD27^lowCD43^low antigen-experienced CD8⁺ T cells, (3) generation of memory-type CD8⁺ T cells [Memory Precursor Effector Cells (MPECs), as well as CD127^highCD43^low, and CD27^highCD43^low CD8⁺ T cells], and (4) generation of effector-like memory CD8⁺ T cells (CD27^lowCD43^low). We propose that these correlates could be useful for the general assessment of the quality of the CD8⁺ T cell immune response induced by novel antigens with potential use in a vaccine against Rickettsia.     

Actively induced antigen-specific CD8(+) T cells by epitope-bearing parasite pre-infection but not prime/boost virus vector vaccination could ameliorate the course of Plasmodium yoelii blood-stage infection

The lack of MHC molecules on red blood cells (RBCs) has led to questions regarding the immunological function of CD8(+) T cells against malarial blood-stage (MBS). However, several recent reports contradicting with this concept have suggested that they play an important role in the course of MBS infection. The present study generated genetically engineered murine malaria, Plasmodium yoelii, which expresses a well-defined Trypanosoma cruzi-derived, H-2K(b)-restricted CD8(+) T cell epitope, ANYNFTLV. Prime/boost vaccination by the use of recombinant adenovirus and recombinant modified vaccinia virus Ankara (MVA), which induced an enhanced number of ANYNFTLV-specific CD8(+) T cells, failed to prevent a pathological outcome to occur upon ANYNFTLV-expressing murine MBS infection. This outcome did not change even with the combination of passive transfer of an appreciable number of in vitro-expanded ANYNFTLV-specific CD8(+) T cells. In contrast, the pre-infection of mice with T. cruzi, which intrinsically bears the same CD8(+) T cell epitope significantly improved the survival of ANYNFTLV-expressing malaria-infected mice but not that of control malaria-infected ones. This protective effect was abrogated by the use of a CD8(+) T cell-depleting monoclonal antibody. Although the protective effect was observed only in certain situations, the actively induced antigen-specific CD8(+) T cells could ameliorate the pathologies caused by the MBS. This is the first study to implicate that the active induction of antigen-specific CD8(+) T cells should be included in the development of a vaccine against MBS.     

Energy-restricted diets result in higher numbers of CD4, CD8, immunoglobulins (A, M, and G), and CD45RA cells in spleen and CD4, immunoglobulin A, and CD45RA cells in colonic lamina propria of rats

Dietary energy restriction (ER) offers certain health benefits, particularly when ER is controlled through manipulation of dietary fats. Our hypothesis is that cellular immunity is modulated by dietary ER. Furthermore, we believe that the immune response may differ between spleen and colon because their lymphatic and vascular organization is different. The objective of the study was to test this hypothesis by determining the effects of dietary ER through manipulation of energy intake from high-fat (HF) diets on the expression and frequency of the CD4⁺ (T-helper/T-inducer) and CD8⁺ (T-cytotoxic/T-suppressor) cells, CD45RA (B-cell–specific marker), and immunoglobulins (Ig) A-, G-, and M-bearing cells in spleen and colon in rats by immunohistochemical method. Rats fed the HF diet had a significantly (P < .05) reduced number of immune cells as compared with those fed ER diets. Energy-restricted diet–fed rats showed higher (P < .05) numbers of CD4⁺, CD8⁺, IgA, IgM, IgG, and CD45RA cells in spleen and CD4⁺, IgA, and CD45RA cells in colonic lamina propria. The IgA-containing cells were markedly higher in the colon compared with the spleen. No change occurred in the number of IgM- and IgG-containing cells in colonic tissues between groups, except for the 20% ER group where IgM-labeled cells were higher (P < .05) compared with HF and 40% ER groups. These findings suggest that ER may modulate adaptive immune function and that CD4⁺ and IgA cells may serve as biological indicators for dietary energy-modulated immunoresponse in spleen and colon, respectively.     

Profound CD8+ T cell immunity elicited by sequential daily immunization with exogenous antigen plus the TLR3 agonist poly(I:C)

The development of vaccines that elicit robust CD8⁺ T cell immunity has long been a subject of intense investigation. Although whole exogenous protein has not historically been considered as useful for eliciting CD8⁺ T cell immunity, we report herein that whole, protein antigen is capable of eliciting profound levels of CD8⁺ T cell immunity if it is administered via repeated, daily subcutaneous immunization in combination with the TLR3 agonist poly(I:C). Mice immunized for four consecutive days with 100 μg of either whole exogenous OVA or whole HPV16 E7 protein combined with 10 μg of poly(I:C) mounted remarkable antigen-specific CD8⁺ T cell responses as measured by tetramer staining and ELISPOT analysis of splenocytes and peripheral blood, with up to 30% of peripheral CD8⁺ T cells being antigen specific within 7-8 days of vaccination. CD8⁺ T cell immunity elicited using this vaccination approach was critically dependent upon cross presentation, as either whole protein or long synthetic peptides were highly effective immunogens whereas minimal peptide epitopes were not. Vaccine-induced CD8⁺ T cells were also able to regress large, established tumors in vivo. Together these data suggest that ‘cluster’ vaccination with exogenous antigen combined with TLR3 agonist may constitute a profoundly important advancement in therapeutic vaccine design.     

CD4+CD25+ regulatory T cell-mediated changes in the expression of endocytic receptors and endocytosis process of human dendritic cells

CD4⁺CD25⁺ regulatory T cells (Tregs) are known to inhibit immune responses to antigens. Since, the process of antigen uptake by dendritic cells (DC) is central to induction of immune responses, we analyzed the effect of Tregs on the expression of endocytic receptors on DC and its repercussion on antigen uptake. Our results demonstrate that Tregs down-regulate the expression and uptake of antigens via C-type lectin-like receptors CD206 and DC-SIGN, restrain the pinocytosis process of DC and augment the expression of FcγRIIB, an inhibitory Fcγ receptor the engagement of which by IgG-bound antigens leads to inhibition of DC activation. Our results thus provide an additional insight on the pertinence of strategies aimed at blocking Treg functions towards improved vaccination protocols.     

Memory CD8 T cells elicited by HIV-1 lipopeptide vaccines display similar phenotypic profiles but differences in term of magnitude and multifunctionality compared with FLU- or EBV-specific memory T cells in humans

Differentiation marker, multifunctionality and magnitude analyses of specific-CD8⁺ memory T cells are crucial to improve development of HIV vaccines designed to generate cell-mediated immunity. Therefore, we fully characterized the HIV-specific CD8⁺ T cell responses induced in volunteers vaccinated with HIV lipopeptide vaccines for phenotypic markers, tetramer staining, cytokine secretion, and cytotoxic activities. The frequency of ex vivo CD8⁺ T cells elicited by lipopeptide vaccines is very rare and central-memory phenotype and functions of these cells were been shown to be important in AIDS immunity. So, we expanded them using specific peptides to compare the memory T cell responses induced in volunteers by HIV vaccines with responses to influenza (FLU) or Epstein Barr virus (EBV). By analyzing the differentiation state of IFN-γ-secreting CD8⁺ T cells, we found a CCR7⁻CD45RA⁻CD28^+int/CD28⁻ profile (>85%) belonging to a subset of intermediate-differentiated effector T cells for HIV, FLU, and EBV. We then assessed the quality of the response by measuring various T cell functions. The percentage of single IFN-γ T cell producers in response to HIV was 62% of the total of secreting T cells compared with 35% for FLU and EBV, dual and triple (IFN-γ/IL-2/CD107a) T cell producers could also be detected but at lower levels (8% compared with 37%). Finally, HIV-specific T cells secreted IFN-γ and TNF-α, but not the dual combination like FLU- and EBV-specific T cells. Thus, we found that the functional profile and magnitude of expanded HIV-specific CD8⁺ T precursors were more limited than those of to FLU- and EBV-specific CD8⁺ T cells. These data show that CD8⁺ T cells induced by these HIV vaccines have a similar differentiation profile to FLU and EBV CD8⁺ T cells, but that the vaccine potency to induce multifunctional T cells needs to be increased in order to improve vaccination strategies.     

Antigenic peptide nanofibers elicit adjuvant-free CD8 T cell responses

Vaccines that elicit robust CD8⁺ T cell responses are desirable for protection against infectious diseases and cancers. However, most vaccine adjuvants fail to elicit robust CD8⁺ T cell responses without inflammation and associated toxicity. We recently reported that self-assembling peptides that form nanofibers in physiological buffers elicited strong adjuvant-free and antigen-specific antibody responses in mice. However, whether or not such nanofibers likewise can elicit strong CD8⁺ T cell responses is unknown. Here, we demonstrate that the self-assembling peptide Q11 conjugated to a CD8⁺ T cell epitope of ovalbumin (Q11-OVA), elicits strong antigen-specific primary and recall responses, and in a vaccination regimen protects against subsequent infection. Importantly, we show that these antigenic peptide nanofibers do not persist as an inflammatory antigen depot at the injection site. Our results demonstrate for the first time that self-assembling peptides may be useful as carriers for vaccines where CD8⁺ T cell-mediated protection is needed.     

CD4 T-cell responses among adults and young children in response to Streptococcus pneumoniae and Haemophilus influenzae vaccine candidate protein antigens

We characterized cytokine profiles of CD4⁺ T-helper (h) cells in adults and young children to ascertain if responses occur to next-generation candidate vaccine antigens PspA, PcpA, PhtD, PhtE, Ply, LytB of Streptococcus pneumonia (Spn) and protein D and OMP26 of non-typeable Haemophilus influenzae (NTHi). Adults had vaccine antigen-specific Th1 and Th2 cells responsive to all antigens evaluated whereas young children had significant numbers of vaccine antigen-specific CD4⁺ T cells producing IL-2, (p = 0.004). Vaccine antigen-specific CD4⁺ T-cell populations in adults were largely of effector (T_EM) and/or central memory (T_CM) phenotypes as defined by CD45RA⁻CCR7⁺ or CD45RA⁻CCR7⁻ respectively; however among young children antigen-specific IL-2 producing CD4⁺ T cells demonstrated CD45RA⁺ expression (non-memory cells). We conclude that adults have circulating memory CD4⁺ T cells (CD45RA⁻) that can be stimulated by all the tested Spn and NTHi protein vaccine candidate antigens, whereas young children have a more limited response.     

Zoledronic acid induces dose-dependent increase of antigen-specific CD8 T-cell responses in combination with peptide/poly-IC vaccine

Zoledronic acid (ZA) is used for treating osteoporosis and for preventing skeletal fractures in cancer patients suffering from myeloma and prostate cancer. It is also reported to directly induce cancer cell apoptosis and indirectly modulate T-cell immune response as an antitumor agent. In this study, the effect of ZA following peptide/polyinosinic–polycytidylic acid (poly-IC) vaccination was investigated in a murine tumor model. The combination of ZA with peptide/poly-IC vaccine showed a synergistic effect on the induction of antigen-specific CD8 T-cell response. Three consecutive intravenous administrations of ZA was defined to induce the highest CD8 T-cell response. Further, total splenocyte counts and antigen-specific CD8 T-cell response gradually increased depending on the dose of ZA. In tumor-bearing mice, ZA showed a dose-dependent decrease of growth and prolonged survival. Treatment with ZA only decreased the number of CD11b⁺Gr1⁺ myeloid cells in blood. Our results demonstrate that the use of ZA could improve antitumor immune responses induced by the peptide/poly-IC vaccine.     

Novel CD8+ T cell-based vaccine stimulates Gp120-specific CTL responses leading to therapeutic and long-term immunity in transgenic HLA-A2 mice

The limitations of highly active anti-retroviral therapy have necessitated the development of alternative therapeutics for human immunodeficiency virus type-1 (HIV-1)-infected patients with dysfunctional dendritic cells (DCs) and CD4(+) T cell deficiency. We previously demonstrated that HIV-1 Gp120-specific T cell-based Gp120-Texo vaccine by using ConA-stimulated C57BL/6 (B6) mouse CD8(+) T (ConA-T) cells with uptake of pcDNA(Gp120)-transfected B6 mouse DC line DC2.4 (DC2.4(Gp120))-released exosomes (EXO(Gp120)) was capable of stimulating DC and CD4(+) T cell-independent CD8(+) cytotoxic T lymphocyte (CTL) responses detected in wild-type B6 mice using non-specific PE-anti-CD44 and anti-IFN-γ antibody staining by flow cytometry. To assess effectiveness of Gp120-Texo vaccine in transgenic (Tg) HLA-A2 mice mimicking the human situation, we constructed adenoviral vector AdV(Gp120) expressing HIV-1 GP120 by recombinant DNA technology, and generated Gp120-Texo vaccine by using Tg HLA-A2 mouse CD8(+) ConA-T cells with uptake of AdV(Gp120)-transfected HLA-A2 mouse bone marrow DC (DC(Gp120))-released EXO(Gp120). We then performed animal studies to assess Gp120-Texo-induced stimulation of Gp120-specific CTL responses and antitumor immunity in Tg HLA-A2 mice. We demonstrate that Gp120-Texo vaccine stimulates Gp120-specific CTL responses detected in Tg HLA-A2 mice using Gp120-specific PE-HLA-A2/Gp120 peptide (KLTPLCVTL) tetramer staining by flow cytometry. These Gp120-specific CTLs are capable of further differentiating into functional effectors with killing activity to Gp120 peptide-pulsed splenocytes in vivo. In addition, Gp120-Texo vaccine also induces Gp120-specific preventive, therapeutic (for 6 day tumor lung metastasis) and CD4(+) T cell-independent long-term immunity against B16 melanoma BL6-10(Gp120/A2Kb) expressing both Gp120 and A2Kb (α1 and α2 domains of HLA-A2 and α3 domain of H-2K(b)) in Tg HLA-A2 mice. Taken together, the novel CD8(+) Gp120-Texo vaccine capable of stimulating efficient CD4(+) T cell-independent Gp120-specific CD8(+) CTL responses leading to therapeutic and long-term immunity in Tg HLA-A2 mice may represent a new immunotherapeutic vaccine for treatment of HIV-1 patients with CD4(+) T cell deficiency.     

Humoral and cellular immune response generated by different vaccine programs before and after Salmonella Enteritidis challenge in chickens

The poultry industry has a high demand for Salmonella vaccines in order to generate safer Salmonella-free food for consumers around the world. Vaccination against S. Enteritidis (SE) is vastly undertaken in many countries, although the criteria for the use of live vaccine (LV) or killed vaccine (KV) should also depend on the immune mechanisms triggered by each. In this study, a commercial bacterin (KV) and an attenuated SG mutant (LV) were used in four different vaccine programs (LV; LV + LV; KV; LV + KV). At 1 day before (dbi) and 1, 6 and 9 days after SE challenge (dpi), humoral (IgM, IgG and secretory IgA) and cellular (CD8⁺ T cells) immune responses were evaluated along with the production of IL-10, IL-12 and IFN-γ. Although after challenge, all birds from each group had an influx of CD8⁺ T cells, birds which received KV had lower levels of these cells in organs and significantly higher levels of immunoglobulins. The expression of the cytokines was up-regulated in all groups post-vaccination, although, after challenge, cytokine expression decreased in the vaccinated groups, and increased in the unvaccinated group A. IL-10 levels were significantly higher at 1 day post-infection in the group that received KV, which may be involved in the weak cellular immune response observed within this group. In caecal tonsils, IFN-γ expression at 1 dbi was higher in birds which received two vaccine doses, and after challenge, the population of CD8⁺ T cells constantly increased in birds that were only vaccinated with the LV. This study demonstrated that the development of a mature immune response by CD8⁺ T cells, provided by the use of the LV, had better efficacy in comparison to the high antibody levels in the serum stimulated by the KV. However, high secretory IgA levels in the intestinal lumen associated with influx CD8⁺ T cells may be indicative of protection as noticed in group E (LV + KV).     

An unbiased peptide-wide discovery approach to select Mycobacterium tuberculosis antigens that target CD8+ T cell response during infection

Accruing data strongly support the possible role of CD8+ T cells in immunity against tuberculosis (TB). Multivalent vaccines against Mycobacterium tuberculosis (Mtb) that incorporate CD8+ T cell antigens with those that elicit CD4+ T cells are therefore highly desirable. To screen for potential CD8+ T cell antigens that are produced by Mtb during infection, we isolated pathogen-derived peptides that bound to MHC Class I molecules expressed in adherent splenocytes obtained from Mtb-infected mice. Mass spectroscopy analysis revealed the following four nonamer peptides that had 100% homology with Mtb proteins: DGYVGAPAH (MT_0401), TTMPLFAD (MT_1164), RSGAATPVR (MT_2160.1) and LAAVVGVVL (MT_0078). The gene MT_0401 codes the protein 5′-phosphoribosylglycinamide transformylase 2 and the other three genes code for hypothetical proteins with unknown function. The NCBI/Blast analysis showed that among the four peptides DGYVGAPAH had the highest maximum alignment score and lowest E value (number of alignments expected by chance). Therefore, we assessed whether MT_0401 expressed in two genetic vaccine formulations was capable of stimulating CD8+ T cell response that is specific to DGYVGAPAH peptide. When mice were immunized with a recombinant plasmid DNA and an E1/E3-deleted Adenovirus 5 expressing MT0401 protein, using both homologous and heterologous prime-boost protocols, they developed strong DGYVGAPAH-specific CD8+ T cell response as well as antibody and CD4+ specific T cell response to the full length MT0401 protein. Equally important was the observation that mice infected with Mtb developed DGYVGAPAH-specific CD8+ T cell responses in both spleen and lungs. These results demonstrate that Mtb antigens that are processed and presented via MHC Class I machinery can be readily identified by the described approach and may be useful candidate antigens to stimulate specific CD8+ T cell responses in vaccine development programs.     

Discovery of novel cross-protective Rickettsia prowazekii T-cell antigens using a combined reverse vaccinology and in vivo screening approach

Rickettsial agents are some of the most lethal pathogens known to man. Among them, Rickettsia prowazekii is a select agent with potential use for bioterrorism; yet, there is no anti-Rickettsia vaccine commercially available. Owing to the obligate intracellular lifestyle of rickettsiae, CD8⁺ T cells are indispensable for protective cellular immunity. Furthermore, T cells can mediate cross-protective immunity between different pathogenic Rickettsia, a finding consistent with the remarkable similarity among rickettsial genomes. However, Rickettsia T cell antigens remain unidentified. In the present study, we report an algorithm that allowed us to identify and validate four novel R. prowazekii vaccine antigen candidates recognized by CD8⁺ T cells from a set of twelve in silico-defined protein targets. Our results highlight the importance of combining proteasome-processing as well as MHC class-I-binding predictions. The novel rickettsial vaccine candidate antigens, RP778, RP739, RP598, and RP403, protected mice against a lethal challenge with Rickettsia typhi, which is indicative of cross-protective immunity within the typhus group rickettsiae. Together, our findings validate a reverse vaccinology approach as a viable strategy to identify protective rickettsial antigens and highlight the feasibility of a subunit vaccine that triggers T-cell-mediated cross-protection among diverse rickettsiae.     

Mucosal immunization in macaques upregulates the innate APOBEC 3G anti-viral factor in CD4 memory T cells

APOBEC3G is an innate intracellular anti-viral factor which deaminates retroviral cytidine to uridine. In vivo studies of APOBEC3G (A3G) were carried out in rhesus macaques, following mucosal immunization with SIV antigens and CCR5 peptides, linked to the 70 kDa heat shock protein. A progressive increase in A3G mRNA was elicited in PBMC after each immunization (p < 0.0002 to p ≤ 0.02), which was maintained for at least 17 weeks. Analysis of memory T cells showed a significant increase in A3G mRNA and protein in CD4⁺CCR5⁺ memory T cells in circulating (p = 0.0001), splenic (p = 0.0001), iliac lymph nodes (p = 0.002) and rectal (p = 0.01) cells of the immunized compared with unimmunized macaques. Mucosal challenge with SIVmac 251 showed a significant increase in A3G mRNA in the CD4⁺CCR5⁺ circulating cells (p < 0.01) and the draining iliac lymph node cells (p < 0.05) in the immunized uninfected macaques, consistent with a protective effect exerted by A3G. The results suggest that mucosal immunization in a non-human primate can induce features of a memory response to an innate anti-viral factor in CCR5⁺CD4⁺ memory and CD4⁺CD95⁺CCR7⁻ effector memory T cells.     

CD4+ and CD8+ T cell- and IL-17-mediated protection against Entamoeba histolytica induced by a recombinant vaccine

Amebiasis in the murine model can be prevented by vaccination with the Gal/GalNAc lectin through a T cell-dependent mechanism. In this work we further decipher the mechanism of this protection. Mice vaccinated with the recombinant “LecA” fragment of the Gal/GalNAc lectin with alum were capable of transferring protection to naïve recipients by both CD4+ T cells and surprisingly CD8+ T cells. We then examined the cytokine profile of these cells. CD4+ T cells from PBMC of LecA-alum vaccinated mice were observed to be a major source of IFN-γ, known to be a protective cytokine with this vaccine. In contrast, CD8+ T cells produced relatively little IFN-γ but more IL-17 than the CD4 compartment. We thus examined the role of IL-17 in vaccine mediated protection and found through neutralization experiments that this cytokine contributed to LecA-alum vaccine protection. In addition we examined whether these cells exhibited direct amebicidal activity in vitro and found that both populations had amebicidal activity at high concentrations (1000:1) but CD8+ T cells appeared more potent, capable of cytotoxicity at a 100:1 ratio. In conclusion, both CD4 and CD8 T cells exert protection with this amebiasis vaccine. The mechanism of CD8 T cell-mediated protection may include direct amebicidal activity and/or IL-17 production. Both IL-17 and IFN-γ are useful surrogates for immune protection.     

CD4 T lymphocytes mediated protection against invasive pneumococcal infection induced by mucosal immunization with ClpP and CbpA

Intranasal delivery of pneumococcal protein vaccines would be a promising way to prevent invasive pneumococcal infection. Using an invasive infection model by intranasal inoculation of pneumococci, we demonstrated that immunizing mice intranasally with a mixture of ClpP (the caseinolytic protease) and CbpA (Choline binding protein A) elicited better protection than that of immunizing either single ClpP or CbpA. Anti-ClpP or anti-CbpA hyperimmune sera from intranasal-immunized mice significantly inhibited the adhesion of Streptococcus pneumoniae to A549 cells and combination of two antisera resulted in an additive effect. Both of two antisera could also kill S. pneumoniae by polymorphonuclear leukocytes in a complement-dependent way. The anti-infection activity and production of hyperimmune antibodies induced by mucosal immunization with ClpP and CbpA could be abrogated by the depletion of CD4⁺ T lymphocytes. Our data therefore indicated a critical role for CD4⁺ T lymphocytes in developing mucosal protein-based vaccines against invasive pneumococcal infection.