Superior protection in a relapsing Plasmodium cynomolgi rhesus macaque model by a chemoprophylaxis with sporozoite immunization regimen with atovaquone-proguanil followed by primaquine.

BACKGROUND: To gain a deeper understanding of protective immunity against relapsing malaria, this study examined sporozoite-specific T cell responses induced by a chemoprophylaxis with sporozoite (CPS) immunization in a relapsing Plasmodium cynomolgi rhesus macaque model. METHODS: The animals received three CPS immunizations with P. cynomolgi sporozoites, administered by mosquito bite, while under two anti-malarial drug regimens. Group 1 (n = 6) received artesunate/chloroquine (AS/CQ) followed by a radical cure with CQ plus primaquine (PQ). Group 2 (n = 6) received atovaquone-proguanil (AP) followed by PQ. After the final immunization, the animals were challenged with intravenous injection of 104 P. cynomolgi sporozoites, the dose that induced reliable infection and relapse rate. These animals, along with control animals (n = 6), were monitored for primary infection and subsequent relapses. Immunogenicity blood draws were done after each of the three CPS session, before and after the challenge, with liver, spleen and bone marrow sampling and analysis done after the challenge. RESULTS: Group 2 animals demonstrated superior protection, with two achieving protection and two experiencing partial protection, while only one animal in group 1 had partial protection. These animals displayed high sporozoite-specific IFN-γ T cell responses in the liver, spleen, and bone marrow after the challenge with one protected animal having the highest frequency of IFN-γ+ CD8+, IFN-γ+ CD4+, and IFN-γ+ γδ T cells in the liver. Partially protected animals also demonstrated a relatively high frequency of IFN-γ+ CD8+, IFN-γ+ CD4+, and IFN-γ+ γδ T cells in the liver. It is important to highlight that the second animal in group 2, which experienced protection, exhibited deficient sporozoite-specific T cell responses in the liver while displaying average to high T cell responses in the spleen and bone marrow. CONCLUSIONS: This research supports the notion that local liver T cell immunity plays a crucial role in defending against liver-stage infection. Nevertheless, there is an instance where protection occurs independently of T cell responses in the liver, suggesting the involvement of the liver's innate immunity. The relapsing P. cynomolgi rhesus macaque model holds promise for informing the development of vaccines against relapsing P. vivax.

Human Memory B Cells in Healthy Gingiva, Gingivitis, and Periodontitis.

The presence of inflammatory infiltrates with B cells, specifically plasma cells, is the hallmark of periodontitis lesions. The composition of these infiltrates in various stages of homeostasis and disease development is not well documented. Human tissue biopsies from sites with gingival health (n = 29), gingivitis (n = 8), and periodontitis (n = 21) as well as gingival tissue after treated periodontitis (n = 6) were obtained and analyzed for their composition of B cell subsets. Ag specificity, Ig secretion, and expression of receptor activator of NF-κB ligand and granzyme B were performed. Although most of the B cell subsets in healthy gingiva and gingivitis tissues were CD19(+)CD27(+)CD38(-) memory B cells, the major B cell component in periodontitis was CD19(+)CD27(+)CD38(+)CD138(+)HLA-DR(low) plasma cells, not plasmablasts. Plasma cell aggregates were observed at the base of the periodontal pocket and scattered throughout the gingiva, especially apically toward the advancing front of the lesion. High expression of CXCL12, a proliferation-inducing ligand, B cell-activating factor, IL-10, IL-6, and IL-21 molecules involved in local B cell responses was detected in both gingivitis and periodontitis tissues. Periodontitis tissue plasma cells mainly secreted IgG specific to periodontal pathogens and also expressed receptor activator of NF-κB ligand, a bone resorption cytokine. Memory B cells resided in the connective tissue subjacent to the junctional epithelium in healthy gingiva. This suggested a role of memory B cells in maintaining periodontal homeostasis.

Tissue Distribution of Memory T and B Cells in Rhesus Monkeys following Influenza A Infection.

Studies of influenza-specific immune responses in humans have largely assessed systemic responses involving serum Ab and peripheral blood T cell responses. However, recent evidence indicates that tissue-resident memory T (TRM) cells play an important role in local murine intrapulmonary immunity. Rhesus monkeys were pulmonary exposed to 2009 pandemic H1N1 virus at days 0 and 28 and immune responses in different tissue compartments were measured. All animals were asymptomatic postinfection. Although only minimal memory immune responses were detected in peripheral blood, a high frequency of influenza nucleoprotein-specific memory T cells was detected in the lung at the "contraction phase," 49-58 d after second virus inoculation. A substantial proportion of lung nucleoprotein-specific memory CD8(+) T cells expressed CD103 and CD69, phenotypic markers of TRM cells. Lung CD103(+) and CD103(-) memory CD8(+) T cells expressed similar levels of IFN-γ and IL-2. Unlike memory T cells, spontaneous Ab secreting cells and memory B cells specific to influenza hemagglutinin were primarily observed in the mediastinal lymph nodes. Little difference in systemic and local immune responses against influenza was observed between young adult (6-8 y) and old animals (18-28 y). Using a nonhuman primate model, we revealed substantial induction of local T and B cell responses following 2009 pandemic H1N1 infection. Our study identified a subset of influenza-specific lung memory T cells characterized as TRM cells in rhesus monkeys. The rhesus monkey model may be useful to explore the role of TRM cells in local tissue protective immunity after rechallenge and vaccination.

Antibody profiles to plasmodium merozoite surface protein-1 in Cambodian adults during an active surveillance cohort with nested treatment study.

BACKGROUND: In addition to evidence for a protective role of antibodies to the malaria blood stage antigen merozoite surface protein 1 (MSP1), MSP1 antibodies are also considered as a marker of past malaria exposure in sero-epidemiological studies. METHODS: In order to better assess the potential use of MSP1 serology in malaria chemoprophylaxis trials in endemic areas, an analysis for the prevalence of antibodies to both Plasmodium falciparum and Plasmodium vivax MSP142 in healthy Cambodian adults was conducted at two sites as part of an active, observational cohort evaluating the efficacy of dihydroartemisinin-piperaquine (DP) for uncomplicated malaria (ClinicalTrials.gov identifier NCT01280162). RESULTS: Rates of baseline sero-positivity were high (59 and 73% for PfMSP142 and PvMSP142, respectively), and titers higher in those who lived in a higher transmission area, although there was little correlation in titers between the two species. Those volunteers who subsequently went on to develop malaria had higher baseline MSP142 titers than those who did not for both species. Titers to both antigens remained largely stable over the course of the 4-6 month study, except in those infected with P. falciparum who had multiple recurrences. CONCLUSION: These findings illuminate the difficulties in using MSP142 serology as either a screening criterion and/or biomarker of exposure in chemoprophylaxis studies. Further work remains to identify useful markers of malarial infection and/or immunity.

MxA expression induced by α-defensin in healthy human periodontal tissue.

Although periodontal tissue is continually challenged by microbial plaque, it is generally maintained in a healthy state. To understand the basis for this, we investigated innate antiviral immunity in human periodontal tissue. The expression of mRNA encoding different antiviral proteins, myxovirus resistance A (MxA), protein kinase R (PKR), oligoadenylate synthetase (OAS), and secretory leukocyte protease inhibitor (SLPI) were detected in both healthy tissue and that with periodontitis. Immunostaining data consistently showed higher MxA protein expression in the epithelial layer of healthy gingiva as compared with tissue with periodontitis. Human MxA is thought to be induced by type I and III interferons (IFNs) but neither cytokine type was detected in healthy periodontal tissues. Treatment in vitro of primary human gingival epithelial cells (HGECs) with α-defensins, but not with the antimicrobial peptides ß-defensins or LL-37, led to MxA protein expression. α-defensin was also detected in healthy periodontal tissue. In addition, MxA in α-defensin-treated HGECs was associated with protection against avian influenza H5N1 infection and silencing of the MxA gene using MxA-targeted-siRNA abolished this antiviral activity. To our knowledge, this is the first study to uncover a novel pathway of human MxA induction, which is initiated by an endogenous antimicrobial peptide, namely α-defensin. This pathway may play an important role in the first line of antiviral defense in periodontal tissue.

Preclinical evaluation of immunogenicity, efficacy and safety of a recombinant plant-based SARS-CoV-2 RBD vaccine formulated with 3M-052-Alum adjuvant.

Cost-effective, and accessible vaccines are needed for mass immunization to control the ongoing coronavirus disease 2019 (COVID-19), especially in low- and middle-income countries (LMIC).A plant-based vaccine is an attractive technology platform since the recombinant proteins can be easily produced at large scale and low cost. For the recombinant subunit-based vaccines, effective adjuvants are crucial to enhance the magnitude and breadth of immune responses elicited by the vaccine. In this study, we report a preclinical evaluation of the immunogenicity, efficacy and safety of a recombinant plant-based SARS-CoV-2 RBD vaccine formulated with 3M-052 (TLR7/8 agonist)-Alum adjuvant. This vaccine formulation, named Baiya SARS-CoV-2 Vax 2, induced significant levels of RBD-specific IgG and neutralizing antibody responses in mice. A viral challenge study using humanized K18-hACE2 mice has shown that animals vaccinated with two doses of Baiya SARS-CoV-2 Vax 2 established immune protection against SARS-CoV-2. A study in nonhuman primates (cynomolgus monkeys) indicated that immunization with two doses of Baiya SARS-CoV-2 Vax 2 was safe, well tolerated, and induced neutralizing antibodies against the prototype virus and other viral variants (Alpha, Beta, Gamma, Delta, and Omicron subvariants). The toxicity of Baiya SARS-CoV-2 Vax 2 was further investigated in Jcl:SD rats, which demonstrated that a single dose and repeated doses of Baiya SARS-CoV-2 Vax 2 were well tolerated and no mortality or unanticipated findings were observed. Overall, these preclinical findings support further clinical development of Baiya SARS-CoV-2 Vax 2.

A Pvs25 mRNA vaccine induces complete and durable transmission-blocking immunity to Plasmodium vivax.

Plasmodium vivax (P. vivax) is the major malaria parasite outside of Africa and no vaccine is available against it. A vaccine that interrupts parasite transmission (transmission-blocking vaccine, TBV) is considered highly desirable to reduce the spread of P. vivax and to accelerate its elimination. However, the development of a TBV against this pathogen has been hampered by the inability to culture the parasite as well as the low immunogenicity of the vaccines developed to date. Pvs25 is the most advanced TBV antigen candidate for P. vivax. However, in previous phase I clinical trials, TBV vaccines based on Pvs25 yielded low antibody responses or had unacceptable safety profiles. As the nucleoside-modified mRNA-lipid nanoparticle (mRNA-LNP) vaccine platform proved to be safe and effective in humans, we generated and tested mRNA-LNP vaccines encoding several versions of Pvs25 in mice. We found that in a prime-boost vaccination schedule, all Pvs25 mRNA-LNP vaccines elicited robust antigen-specific antibody responses. Furthermore, when compared with a Pvs25 recombinant protein vaccine formulated with Montanide ISA-51 adjuvant, the full-length Pvs25 mRNA-LNP vaccine induced a stronger and longer-lasting functional immunity. Seven months after the second vaccination, vaccine-induced antibodies retained the ability to fully block P. vivax transmission in direct membrane feeding assays, whereas the blocking activity induced by the protein/ISA-51 vaccine dropped significantly. Taken together, we report on mRNA vaccines targeting P. vivax and demonstrate that Pvs25 mRNA-LNP outperformed an adjuvanted Pvs25 protein vaccine suggesting that it is a promising candidate for further testing in non-human primates.

Lymphostatin, a virulence factor of attaching and effacing Escherichia coli, inhibits proliferation and cytokine responses of human T cells in a manner associated with cell cycle arrest but not apoptosis or necrosis.

Lymphostatin is a virulence factor of enteropathogenic E. coli (EPEC) and non-O157 serogroup enterohaemorrhagic E. coli. Previous studies using whole-cell lysates of EPEC showed that lymphostatin inhibits the mitogen-activated proliferation of bulk human peripheral blood mononuclear cells (PBMCs) and the production of cytokines IL-2, IL-4, IL-5, and IFN-γ. Here, we used highly purified lymphostatin and PBMC-derived T cells to show that lymphostatin inhibits anti-CD3/anti-CD28-activated proliferation of human CD4+ and CD8+ T cells and blocks the synthesis of IL-2, IL-4, IL-10 and IFN-γ without affecting cell viability and in a manner dependent on an N-terminal DTD glycosyltransferase motif. Such inhibition was not observed with T cells activated by phorbol 12-myristate 13-acetate and ionomycin, implying that lymphostatin targets T cell receptor signaling. Analysis of the expression of CD69 indicated that lymphostatin suppresses T cell activation at an early stage and no impacts on apoptosis or necrosis were observed. Flow cytometric analysis of the DNA content of lymphostatin-treated CD4+ and CD8+ T cells showed a concentration- and DTD-dependent accumulation of the cells in the G0/G1 phase of the cell cycle, and corresponding reduction of the percentage of cells in S phase. Consistent with this, we found a marked reduction in the abundance of cyclins D3, E and A and loss of phosphorylated Rb over time in activated T cells from 8 donors treated with lymphostatin. Moreover, the cyclin-dependent kinase (cdk) inhibitor p27kip1, which inhibits progression of the cell cycle at G1 by acting on cyclin E-cdk2 or cyclin D-cdk4 complexes, was found to be accumulated in lymphostatin-treated T cells. Analysis of the abundance of phosphorylated kinases involved in signal transduction found that 30 of 39 were reduced in abundance following lymphostatin treatment of T cells from 5 donors, albeit not significantly so. Our data provide novel insights into the mode of action of lymphostatin on human T lymphocytes.

Evaluation of the safety and immunogenicity in rhesus monkeys of a recombinant malaria vaccine for Plasmodium vivax with a synthetic Toll-like receptor 4 agonist formulated in an emulsion.

Plasmodium vivax is the major cause of malaria outside sub-Saharan Africa and inflicts debilitating morbidity and consequent economic impacts in developing countries. In order to produce a P. vivax vaccine for global use, we have previously reported the development of a novel chimeric recombinant protein, VMP001, based on the circumsporozoite protein (CSP) of P. vivax. Very few adjuvant formulations are currently available for human use. Our interest is to evaluate second-generation vaccine formulations to identify novel combinations of adjuvants capable of inducing strong, long-lasting immune responses. In this study rhesus monkeys were immunized intramuscularly three times with VMP001 in combination with a stable emulsion (SE) or a synthetic Toll-like receptor 4 (TLR4) agonist (glucopyranosyl lipid A [GLA]) in SE (GLA-SE). Sera and peripheral blood mononuclear cells (PBMCs) were tested for the presence of antigen-specific humoral and cellular responses, respectively. All groups of monkeys generated high titers of anti-P. vivax IgG antibodies, as detected by enzyme-linked immunosorbent assays (ELISAs) and immunofluorescence assays. In addition, all groups generated a cellular immune response characterized by antigen-specific CD4(+) T cells secreting predominantly interleukin-2 (IL-2) and lesser amounts of tumor necrosis factor (TNF). We conclude that the combination of VMP001 and GLA-SE is safe and immunogenic in monkeys and may serve as a potential second-generation vaccine candidate against P. vivax malaria.

Department of Defense influenza and other respiratory disease surveillance during the 2009 pandemic.

The Armed Forces Health Surveillance Center's Division of Global Emerging Infections Surveillance and Response System (AFHSC-GEIS) supports and oversees surveillance for emerging infectious diseases, including respiratory diseases, of importance to the U.S. Department of Defense (DoD). AFHSC-GEIS accomplishes this mission by providing funding and oversight to a global network of partners for respiratory disease surveillance. This report details the system's surveillance activities during 2009, with a focus on efforts in responding to the novel H1N1 Influenza A (A/H1N1) pandemic and contributions to global public health. Active surveillance networks established by AFHSC-GEIS partners resulted in the initial detection of novel A/H1N1 influenza in the U.S. and several other countries, and viruses isolated from these activities were used as seed strains for the 2009 pandemic influenza vaccine. Partners also provided diagnostic laboratory training and capacity building to host nations to assist with the novel A/H1N1 pandemic global response, adapted a Food and Drug Administration-approved assay for use on a ruggedized polymerase chain reaction platform for diagnosing novel A/H1N1 in remote settings, and provided estimates of seasonal vaccine effectiveness against novel A/H1N1 illness. Regular reporting of the system's worldwide surveillance findings to the global public health community enabled leaders to make informed decisions on disease mitigation measures and controls for the 2009 A/H1N1 influenza pandemic. AFHSC-GEIS's support of a global network contributes to DoD's force health protection, while supporting global public health.

A single injection of 19 kda carboxy-terminal fragment of Plasmodium yoelii merozoite surface protein 1 (PyMSP1(19)) formulated with Montanide ISA and CpG ODN induces protective immune response in mice.

OBJECTIVE: To investigate the efficacy of a vaccine formulation of the 19 kDa conserved carboxyl-terminal fragment of Plasmodium yoelii merozoite surface protein-1 (PyMSP1(19)) formulated with CpG ODN 1826 and Montanide ISA51 or ISA720 when used to immunize mice by a single injection. METHODS: Groups of BALB/c mice were immunized parenterally with one, two or four injections with PBS or PyMSP1(19) formulated with CpG ODN in ISA51 or ISA720. Sera were collected weekly and assessed for total IgG and IgG subclass titers. Protection was tested by challenge infection with P. yoelii YM. RESULTS: Interestingly, single injection immunization showed the same kinetics of antibody responses as two- or four-injection immunization. However, the peak antibody response induced by PyMSP1(19) in CpG ODN and ISA51 appeared earlier than that induced by PyMSP1(19) in CpG ODN and ISA720 (28 days vs 41 days). At day 63 after the first injection, the PyMSP1(19)-specific IgG antibody levels by single injection and four-injection immunizations were not different. However, the levels of the IgG2a antibody subclass were significantly lower by single injection immunization with PyMSP1(19) in CpG ODN and ISA720. The antibodies were sustained at high levels for at least 20 weeks. After challenge infection, all mice immunized by a single injection of PyMSP1(19) in CpG ODN and ISA51 survived with low-grade parasitemia, while 50% of mice immunized with PyMSP1(19) in CpG ODN and ISA720 died with high levels of parasitemia. CONCLUSION: These findings suggest that MSP1(19) immunization by a single injection can induce protective immunity, particularly when formulated with an appropriate strong adjuvant.

Antiviral immune responses in H5N1-infected human lung tissue and possible mechanisms underlying the hyperproduction of interferon-inducible protein IP-10.

Information on the immune response against H5N1 within the lung is lacking. Here we describe the sustained antiviral immune responses, as indicated by the expression of MxA protein and IFN-alpha mRNA, in autopsy lung tissue from an H5N1-infected patient. H5N1 infection of primary bronchial/tracheal epithelial cells and lung microvascular endothelial cells induced IP-10, and also up-regulated the retinoic acid-inducible gene-I (RIG-I). Down-regulation of RIG-I gene expression decreased IP-10 response. Co-culturing of H5N1-infected pulmonary cells with TNF-alpha led to synergistically enhanced production of IP-10. In the absence of viral infection, TNF-alpha and IFN-alpha also synergistically enhanced IP-10 response. Methylprednisolone showed only a partial inhibitory effect on this chemokine response. Our findings strongly suggest that both the H5N1 virus and the locally produced antiviral cytokines; IFN-alpha and TNF-alpha may have an important role in inducing IP-10 hyperresponse, leading to inflammatory damage in infected lung.

Prevalence of CYP2D6 Genotypes and Predicted Phenotypes in a Cohort of Cambodians at High Risk for Infections with Plasmodium vivax.

Clinical failure of primaquine (PQ) has been demonstrated in people with CYP450 2D6 genetic polymorphisms that result in reduced or no enzyme activity. The distribution of CYP2D6 genotypes and predicted phenotypes in the Cambodian population is not well described. Surveys in other Asian countries have shown an approximate 50% prevalence of the reduced activity CYP2D6 allele *10, which could translate into increased risk of PQ radical cure failure and repeated relapses, making interruption of transmission and malaria elimination difficult to achieve. We determined CYP2D6 genotypes from 96 volunteers from Oddor Meanchey Province, Cambodia, an area endemic for Plasmodium vivax. We found a 54.2% frequency of the *10 allele, but in approximately half of our subjects, it was paired with a normal activity allele, either *1 or *2. The prevalence of *5, a null allele, was 9.4%. Overall predicted phenotype percentages were normal metabolizers, 46%; intermediate metabolizers, 52%; and poor metabolizers, 1%.

Expression of toll-like receptors on antigen-presenting cells in patients with falciparum malaria.

The continuous release of blood-stage malaria parasites and their products can activate components of the innate immune system and induce the production of proinflammatory cytokines. Toll-like receptors (TLRs) have emerged as pattern-recognition receptors, residing on/in innate immune cells whose function is recognizing specific conserved components on different microbes. The aim of this study was to determine the expression of TLR2, TLR4 and TLR9 on antigen-presenting cells (APCs) in patients with mild and severe forms of falciparum malaria. Healthy individuals were used as controls. Peripheral blood mononuclear cells (PBMCs) were stained with specific monoclonal antibodies (mAbs) to investigate the percentage and the level of TLR expression by flow cytometry. Patients with severe and mild malaria showed increased surface expression of TLR2 and TLR4 on CD14(+)monocytes and myeloid dendritic cells (MDCs) and decreased intracellular expression of TLR9 on plasmacytoid dendritic cells (PDCs), compared to those of healthy controls. A significant decrease in the percentage of circulating CD14(+)monocytes and MDCs expressing TLR2 was found in both severe and mild malaria patients. These findings suggested that TLRs might play role in innate immune recognition in which the differential expression of TLRs on APCs could be regulated by the P. falciparum parasite.

Expression and function of Toll-like receptors on dendritic cells and other antigen presenting cells from non-human primates.

Antigen presenting cells (APCs), especially dendritic cells (DCs), play a crucial role in immune responses against infections by sensing microbial invasion through Toll-like receptors (TLRs). In this regard, TLR ligands are attractive candidates for use in humans and animal models as vaccine adjuvants. So far, no studies have been performed on TLR expression in non-human primates such as rhesus macaques. Therefore, we studied the TLR expression patterns in different subsets of APC in rhesus macaques and compared them to similar APC subsets in human. Also, expression was compared with corresponding DC subsets from different organs from mice. Here we show by semi-quantitative RT-PCR, that blood DC subsets of rhesus macaque expressed the same sets of TLRs as those of human but substantially differed from mouse DC subsets. Macaque myeloid DCs (MDCs) expressed TLR3, 4, 7 and 8 whereas macaque plasmacytoid DCs (PDCs) expressed only TLR7 and 9. Additionally, TLR expression patterns in macaque monocyte-derived dendritic cells (mo-DCs) (i.e., TLR3, 4, 8 and 9), monocytes (i.e., TLR4, 7, and 8) and B cells (i.e., TLR4, 7, 8, and 9) were also similar to their human counterparts. However, the responsiveness of macaque APCs to certain TLR ligands partially differed from that of human in terms of phenotype differentiation and cytokine production. Strikingly, in contrast to human mo-DCs, no IL-12p70 production was observed when macaque mo-DCs were stimulated with TLR ligands. In addition, CD40 and CD86 phenotypic responses to TLR8 ligand (poly U) in mo-DCs of macaque were higher than that of human. Despite these functional differences, our results provide important information for a rational design of animal models in evaluating TLR ligands as adjuvant in vivo.

Memory T cell subsets in healthy gingiva and periodontitis tissues.

BACKGROUND: In the gingival sulcus, effective and balanced innate and adaptive immune responses against subgingival plaque microbiome are crucial to maintain immune homeostasis. In this study, we investigated the memory T cell subsets in healthy gingiva and periodontitis tissues. METHODS: Anatomical localization of T cells (CD3+ , CD4+ , and CD8+ ) in healthy gingiva and periodontitis tissues were examined immunohistochemically. Subsets of memory T cells from isolated gingival cells were analyzed by flow cytometry using a cocktail of monoclonal antibodies (anti-CD69, anti-CD103, anti-CD45RA, anti-CCR7, anti-CD28, and anti-CD95). Intracellular cytokine staining of interleukin (IL)-17 and interferon (IFN)-γ expression on memory T cells in periodontitis tissues was also investigated. RESULTS: We found that healthy gingiva contains two memory T cell populations; a CD69- recirculating population and a CD69+ gingiva-resident memory T cell population. CD4+ T cells with transitional memory (TTM ) phenotype (CD45RA- CCR7- CD28+ CD95+ ) constitute the major subset within these two populations. A significant increase in the proportion of CD4+ CD69+ CD103- memory T cells was observed in periodontitis tissues compared with healthy gingiva. CD4+ memory T cells from periodontitis tissues produced either IL-17 or IFN-γ whereas CD8+ memory T cells produced only IFN-γ. CONCLUSIONS: Our findings suggest that recirculating and gingiva-resident memory T cells could represent an important part of the immune surveillance network in the connective tissue, maintaining periodontal homeostasis. Imbalance of subgingival bacterial communities could damage gingival barrier allowing bacterial antigens to get access to the deeper connective tissue where they activate memory T cells leading to deleterious inflammation; a hallmark of periodontitis.

Relative levels of IL4 and IFN-gamma in complicated malaria: association with IL4 polymorphism and peripheral parasitemia.

Functional IL4-590 C/T polymorphisms and the relative amounts of IL4 and IFN-gamma were investigated in relation to severity of malaria in 110 and 169 Thai patients with complicated and uncomplicated malaria, respectively. The plasma IL4 and IFN-gamma levels were determined by ELISA and the IL4-590 C/T polymorphisms were genotyped. The IFN-gamma levels were significantly elevated in patients with complicated malaria in the initial stage of the disease before treatment compared to the levels found with uncomplicated malaria (231pg/ml versus 150pg/ml, p=0.0029), while the IL4 levels were significantly elevated 7 days after treatment (167pg/ml versus 81pg/ml, p=0.0003). Our study did not reveal any association between the IL4-590 C/T transition and the severity of malaria. However, a significant difference in the IL4 to IFN-gamma ratio between patients with complicated and uncomplicated malaria was observed only in patients with IL4-590 T allele homozygosity (geometric mean: 0.321 versus 0.613, p=0.0087 for TT allele). A significant inverse correlation between IL4 to IFN-gamma ratio and peripheral parasitemia was observed only in complicated malaria patients carrying TT genotype (r=-0.283, p=0.046). These results suggest that the IL4-590 C/T polymorphism may play a role in the balance between IL4 and IFN-gamma, as well as in the control of parasitemia, which in turn may alter the severity of malaria.

Chemoprophylaxis with sporozoite immunization in P. knowlesi rhesus monkeys confers protection and elicits sporozoite-specific memory T cells in the liver.

Whole malaria sporozoite vaccine regimens are promising new strategies, and some candidates have demonstrated high rates of durable clinical protection associated with memory T cell responses. Little is known about the anatomical distribution of memory T cells following whole sporozoite vaccines, and immunization of nonhuman primates can be used as a relevant model for humans. We conducted a chemoprophylaxis with sporozoite (CPS) immunization in P. knowlesi rhesus monkeys and challenged via mosquito bites. Half of CPS immunized animals developed complete protection, with a marked delay in parasitemia demonstrated in the other half. Antibody responses to whole sporozoites, CSP, and AMA1, but not CelTOS were detected. Peripheral blood T cell responses to whole sporozoites, but not CSP and AMA1 peptides were observed. Unlike peripheral blood, there was a high frequency of sporozoite-specific memory T cells observed in the liver and bone marrow. Interestingly, sporozoite-specific CD4+ and CD8+ memory T cells in the liver highly expressed chemokine receptors CCR5 and CXCR6, both of which are known for liver sinusoid homing. The majority of liver sporozoite-specific memory T cells expressed CD69, a phenotypic marker of tissue-resident memory (TRM) cells, which are well positioned to rapidly control liver-stage infection. Vaccine strategies that aim to elicit large number of liver TRM cells may efficiently increase the efficacy and durability of response against pre-erythrocytic parasites.