Applying valency-based immuno-selection to generate broadly cross-reactive antibodies against influenza hemagglutinins.

Conserved epitopes shared between virus subtypes are often subdominant, making it difficult to induce broadly reactive antibodies by immunization. Here, we generate a plasmid DNA mix vaccine that encodes protein heterodimers with sixteen different influenza A virus hemagglutinins (HA) representing all HA subtypes except H1 (group 1) and H7 (group 2). Each single heterodimer expresses two different HA subtypes and is targeted to MHC class II on antigen presenting cells (APC). Female mice immunized with the plasmid mix produce antibodies not only against the 16 HA subtypes, but also against non-included H1 and H7. We demonstrate that individual antibody molecules cross-react between different HAs. Furthermore, the mix vaccine induces T cell responses to conserved HA epitopes. Immunized mice are partially protected against H1 viruses. The results show that application of valency-based immuno-selection to diversified antigens can be used to direct antibody responses towards conserved (subdominant) epitopes on viral antigens.

Targeting Xcr1 on Dendritic Cells Rapidly Induce Th1-Associated Immune Responses That Contribute to Protection Against Influenza Infection.

Targeting antigen to conventional dendritic cells (cDCs) can improve antigen-specific immune responses and additionally be used to influence the polarization of the immune responses. However, the mechanisms by which this is achieved are less clear. To improve our understanding, we here evaluate molecular and cellular requirements for CD4+ T cell and antibody polarization after immunization with Xcl1-fusion vaccines that specifically target cDC1s. Xcl1-fusion vaccines induced an IgG2a/IgG2b-dominated antibody response and rapid polarization of Th1 cells both in vitro and in vivo. For comparison, we included fliC-fusion vaccines that almost exclusively induced IgG1, despite inducing a more mixed polarization of T cells. Th1 polarization and IgG2a induction with Xcl1-fusion vaccines required IL-12 secretion but were nevertheless maintained in BATF3-/- mice which lack IL-12-secreting migratory DCs. Interestingly, induction of IgG2a-dominated responses was highly dependent on the early kinetics of Th1 induction and was important for optimal protection in an influenza infection model. Early Th1 induction was dominant, since a combined Xcl1- and fliC-fusion vaccine induced IgG2a/IgG2b polarized antibody responses similar to Xcl1-fusion vaccines alone. In summary, our results demonstrate that targeting antigen to Xcr1+ cDC1s is an efficient strategy for enhancing IgG2a antibody responses through rapid Th1 induction, which can be utilized for improved vaccine design.

Intranasal delivery of a cDC1 targeted influenza vaccine with poly(I:C) enhances T cell responses and protects against influenza infection.

Targeting antigens to dendritic cells represent a promising method for enhancing immune responses against specific antigens. However, many studies have focused on systemic delivery (intravenous or intraperitoneally) of targeted antigen, approaches that are not easily transferable to humans. Here we evaluate the efficacy of an influenza vaccine targeting Xcr1+ cDC1 administered by intranasal immunization. Intranasal delivery of antigen fused to the chemokine Xcl1, the ligand of Xcr1, resulted in specific uptake by lung CD103+ cDC1. Interestingly, intranasal immunization with influenza A/PR/8/34 haemagglutinin (HA) fused to Xcl1, formulated with poly(I:C), resulted in enhanced induction of antigen-specific IFNγ+ CD4+ and IFNγ+ CD8+ T cell responses in lung compared non-targeted anti-NIP-HA (αNIP-HA). Induction of antibody responses was, however, similar in Xcl1-HA and αNIP-HA immunized mice, but significantly higher than in mice immunized with monomeric HA. Both Xcl1-HA and αNIP-HA vaccines induced full protection when mice were challenged with a lethal dose of influenza PR8 virus, reflecting the strong induction of HA-specific antibodies. Our results demonstrate that i.n. delivery of Xcl1-HA is a promising vaccine strategy for enhancing T cell responses in addition to inducing strong antibody responses.

Targeting Antigens to Different Receptors on Conventional Type 1 Dendritic Cells Impacts the Immune Response.

Targeting Ag to surface receptors on conventional type 1 dendritic cells can enhance induction of Ab and T cell responses. However, it is unclear to what extent the targeted receptor influences the resulting responses. In this study, we target Ag to Xcr1, Clec9A, or DEC-205, surface receptors that are expressed on conventional type 1 dendritic cells, and compare immune responses in BALB/c and C57BL/6 mice in vitro and in vivo after intradermal DNA vaccination. Targeting hemagglutinin from influenza A to Clec9A induced Ab responses with higher avidity that more efficiently neutralized influenza virus compared with Xcr1 and DEC-205 targeting. In contrast, targeting Xcr1 resulted in higher IFN-γ+CD8+ T cell responses in spleen and lung and stronger cytotoxicity. Both Clec9A and Xcr1 targeting induced Th1-polarized Ab responses, although the Th1 polarization of CD4+ T cells was more pronounced after Xcr1 targeting. Targeting DEC-205 resulted in poor Ab responses in BALB/c mice and a more mixed Th response. In an influenza challenge model, targeting either Xcr1 or Clec9A induced full and long-term protection against influenza infection, whereas only partial short-term protection was obtained when targeting DEC-205. In summary, the choice of targeting receptor, even on the same dendritic cell subpopulation, may strongly influence the resulting immune response, suggesting that different targeting strategies should be considered depending on the pathogen.

Author Correction: Dendritic cell targeted Ccl3- and Xcl1-fusion DNA vaccines differ in induced immune responses and optimal delivery site.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Targeting Conventional Dendritic Cells to Fine-Tune Antibody Responses.

Dendritic cells (DCs) facilitate cross talk between the innate and adaptive immune system. They sense and phagocytose invading pathogens, and are not only capable of activating naïve T cells, but can also determine the polarization of T cell responses into different effector subtypes. Polarized T cells in turn have a crucial role in antibody class switching and affinity maturation, and consequently the quality of the resulting humoral immunity. Targeting vaccines to DCs thus provides a great deal of opportunities for influencing the humoral immune responses, by fine-tuning the T cell response as well as regulating antigen availability for B cells. In this review we aim to outline how different DC targeted vaccination strategies can be utilized to induce a desired humoral immune response. A range of factors, including route of vaccine administration, use of adjuvants, choice of DC subset and surface receptor to target have been reported to influence the resulting immune response and will be reviewed herein. Finally, we will discuss opportunities for designing improved vaccines and challenges with translating this knowledge into clinical or veterinary medicine.

Dendritic cell targeted Ccl3- and Xcl1-fusion DNA vaccines differ in induced immune responses and optimal delivery site.

Fusing antigens to chemokines to target antigen presenting cells (APC) is a promising method for enhancing immunogenicity of DNA vaccines. However, it is unclear how different chemokines compare in terms of immune potentiating effects. Here we compare Ccl3- and Xcl1-fusion vaccines containing hemagglutinin (HA) from influenza A delivered by intramuscular (i.m.) or intradermal (i.d.) DNA vaccination. Xcl1 fusion vaccines target cDC1s, and enhance proliferation of CD4+ and CD8+ T cells in vitro. In contrast, Ccl3 target both cDC1 and cDC2, but only enhance CD4+ T cell proliferation in combination with cDC2. When Ccl3- or Xcl1-HA fusion vaccines were administered by i.m. DNA immunization, both vaccines induced Th1-polarized immune responses with antibodies of the IgG2a/IgG2b subclass and IFNγ-secreting T cells. After i.d. DNA vaccination, however, only Xcl1-HA maintained a Th1 polarized response and induced even higher numbers of IFNγ-secreting T cells. Consequently, Xcl1-HA induced superior protection against influenza infection compared to Ccl3-HA after i.d. immunization. Interestingly, i.m. immunization with Ccl3-HA induced the strongest overall in vivo cytotoxicity, despite not inducing OT-I proliferation in vitro. In summary, our results highlight important differences between Ccl3- and Xcl1- targeted DNA vaccines suggesting that chemokine fusion vaccines can be tailor-made for different diseases.

Influences of gender in metabolic syndrome and its components among people living with HIV virus using antiretroviral treatment in Hawassa, southern Ethiopia.

BACKGROUND: Data regarding the influences of gender in metabolic syndrome (MetS) among patients using antiretroviral treatment (ART) in Ethiopia is scarce. The aim of this study was to assess the influences of gender in MetS and its components among HIV-infected patients receiving ART. METHODS: A cross-sectional study was conducted between February 2012 and April 2013. Data on demographic, clinical and anthropometric characteristics were collected from 185 HIV patients using ART. Glucose and lipid profiles were measured from overnight fast blood. The International Diabetes Federation (IDF) and United States national cholesterol education program: adult treatment (US NCEP-ATP) panel III criteria were used to define MetS. RESULT: A total number of 185 (36.8% males and 63.2% females) participants were recruited in this study. The overall prevalence of MetS was 24.3 and 17.8%, diagnosed using IDF and NCEP-ATP criteria respectively. Using IDF criteria, MetS was significantly higher in females compared to males (33.3 vs. 8.8%; p = <0.0001) respectively. Low HDL-c and central obesity were significantly higher MetS components in female compared to males (p = 0.003); and (p = <0.0001, using IDF and NCEP-ATP criteria) respectively. BMI >25 kg/m(2) was significantly associated with MetS in both IDF and NCEP-ATP criteria: unadjusted (UOR) and adjusted odds ratio (AOR) with 95% CI were 3.0 (1.3-6.5) and 3.8 (1.5-9.8); as well as 3.2 (1.4-7.4) and 3.4 (1.4-7.4) respectively. Furthermore age >40 years was significantly associated with MetS using NCEP-ATP: UOR and AOR (95% CI) were 3.1 (1.2-8.3), and 3.8 (1-13.70) respectively. CONCLUSION: Comprehensive medical care approach including with MetS components are a crucial instruments in order to minimize the risk of developing cardiovascular diseases in HIV-infected patients using ART.

Burden of metabolic syndrome among HIV-infected patients in Southern Ethiopia.

BACKGROUND: HIV infection and highly active antiretroviral therapy (HAART) can induce metabolic disturbances including lipodystrophy, dyslipidemia, and insulin resistance, which are reminiscences of metabolic syndrome (MS). However, little is known regarding the magnitude of MS in Ethiopian HIV population. This study, aimed to estimate the prevalence of MS among HIV positive patients with and without HAART. METHODS: A cross-sectional study was conducted at Hawassa University Referral Hospital, southern Ethiopia between February 2012 and April 2013. Data on demographic and anthropometric characteristics were collected from a total of 374 HIV positive participants (188 on ART and 186 on Pre-ART) using WHO stepwise approach. Fasting blood glucose, total cholesterol, triglyceride, HDL-cholesterol and LDL-cholesterol was measured. The International Diabetes Federation (IDF) and the National Cholesterol Education Program: Adult Treatment Panel III (ATP) Criteria were used to define MS. RESULT: Of the 374 study participants 68% were females, and 50.3% were receiving ART. Using the IDF criteria, metabolic syndrome was diagnosed in 25% of patients receiving ART compared to 22.5% of the ART naïve group (OR: 1.14 CI: 0.71-1.84). Using the ATP criteria, the prevalence of MS was 18.1% in the ART groups compared to 15.6% in ART naïve group (OR: 1.20, CI: 0.69-2.06). Patients receiving ART had significantly elevated Cholesterol, triglyceride, glucose and LDL-c levels but lower CD4(+) cell counts than the Pre-ART groups. Being a female, having BMI of at least 25, older age (i.e. age≥45 years) and having total cholesterol of at least 200mg/dl were significantly associated with the presence of MS. Using the ATP criteria to define MS, taking d4T-3TC-EFV regimen was significantly associated with higher odds of MS. CONCLUSION: Almost a quarter of HIV patients on ART developed metabolic syndrome. Furthermore patients on ART had elevated lipid profile and glucose metabolism disturbance than the ART naïve.