Pre-existing immunity and vaccine history determine hemagglutinin-specific CD4 T cell and IgG response following seasonal influenza vaccination.

Effectiveness of seasonal influenza vaccination varies between individuals and might be affected by vaccination history among other factors. Here we show, by monitoring frequencies of CD4 T cells specific to the conserved hemagglutinin epitope HA118-132 and titres of IgG against the corresponding recombinant hemagglutinin protein, that antigen-specific CD4 T cell and antibody responses are closely linked to pre-existing immunity and vaccine history. Upon immunization, a strong early reaction is observed in all vaccine naïve participants and also in vaccine experienced individuals who have not received the respective seasonal vaccine in the previous year. This response is characterized by HA118-132 specific CD4 T cells with a follicular helper T cell phenotype and by ascending titers of hemagglutinin-specific antibodies from baseline to day 28 following vaccination. This trend was observed in only a proportion of those participants who received the seasonal vaccine the year preceding the study. Regardless of history, levels of pre-existing antibodies and CD127 expression on CD4 T cells at baseline were the strongest predictors of robust early response. Thus, both pre-existing immunity and vaccine history contribute to the response to seasonal influenza vaccines.

Ustekinumab Inhibits T Follicular Helper Cell Differentiation in Patients With Crohn's Disease.

BACKGROUND & AIMS: The pathogenesis of chronic inflammatory bowel diseases (Crohn's disease [CD] and ulcerative colitis) involves dysregulated TH1 and TH17 cell responses, which can be targeted therapeutically by the monoclonal antibody Ustekinumab directed against the joint p40 subunit of IL-12 and IL-23. These cytokines may also regulate the differentiation of T follicular helper (TFH) cells, which promote B cell function in germinal centers. However, the role of TFH cells in CD pathogenesis and impact of Ustekinumab therapy on TFH cell fate in patients are poorly defined. METHODS: Lymphocytes were isolated from peripheral blood (n=45) and intestinal biopsies (n=15) of CD patients or healthy controls (n=21) and analyzed by flow cytometry to assess TFH cell phenotypes and functions ex vivo. In addition, TFH cell differentiation was analyzed in the presence of Ustekinumab in vitro. RESULTS: TFH cell frequencies in the intestine as well as peripheral blood were associated with endoscopic as well as biochemical evidence of CD activity. CD patients with clinical response to Ustekinumab, but not those with response to anti-TNF antibodies, displayed reduced frequencies of circulating TFH cells in a concentration-dependent manner while the TFH phenotype was not affected by Ustekinumab therapy. In keeping with this notion, TFH cell differentiation was inhibited by Ustekinumab in vitro while TFH cell maintenance was not affected. Moreover, Ustekinumab therapy resulted in reduced germinal center activity in CD patients in vivo. CONCLUSIONS: These data implicate TFH cells in the pathogenesis of CD and indicate that Ustekinumab therapy affects TFH cell differentiation, which may influence TFH-mediated immune functions in UST-treated CD patients.

OX40 stimulation and PD-L1 blockade synergistically augment HBV-specific CD4 T cells in patients with HBeAg-negative infection.

BACKGROUND & AIMS: Current antiviral therapies lack the potential to eliminate persistent hepatitis B virus (HBV) infection. HBV-specific T cells are crucial for HBV control and have recently been shown to be protective in patients following discontinuation of antiviral therapy. Thus, T cell-based approaches may greatly improve the therapeutic landscape of HBV infection. We aimed to augment HBV-specific CD4 T cells from chronically infected patients by targeting different immunological pathways. METHODS: Expression of various co-stimulatory and inhibitory receptors on HBV- and influenza-specific CD4 T cells was analyzed directly ex vivo by MHC class II-tetramers. Patients infected with HBV genotype D were screened for CD4 T cell responses by IFN-γ ELISpot and intracellular cytokine staining following stimulation with overlapping peptides (OLPs) spanning the HBV-polyprotein. Stimulation with recombinant IL-7, an agonistic OX40-antibody or blockade of PD-L1 was performed in antigen-specific in vitro cultures. Cytokine secretion and expression of transcription factors were analyzed by flow cytometry. Responses targeting influenza, Epstein-Barr virus and tetanus toxoid served as controls. RESULTS: Tetramer-staining revealed that the IL-7 receptor-alpha (CD127), OX40 and PD-1 constitute possible therapeutic targets as they were all strongly expressed on HBV-specific CD4 T cells ex vivo. The HBV-specific CD4 T cell responses identified by OLP screening targeted predominantly the HBV-polymerase and core proteins. Combined OX40 stimulation and PD-L1 blockade significantly augmented IFN-γ and IL-21 producing HBV-specific CD4 T cells in vitro, suggesting active T helper type 1 cell and follicular T helper cell programs. Indeed, transcription factors T-bet and Bcl6 were strongly expressed in cytokine-producing cells. CONCLUSIONS: Combined OX40 stimulation and PD-L1 blockade augmented secretion of the helper T cell signature cytokines IFN-γ and IL-21, suggesting that immunotherapeutic approaches can improve HBV-specific CD4 T cell responses. LAY SUMMARY: CD4 T cells are important in controlling viral infections but are impaired in the context of chronic hepatitis B virus (HBV) infection. Therapeutic approaches to cure chronic HBV infection are highly likely to require an immune-stimulatory component. This study demonstrates that HBV-specific CD4 T cells can be functionally augmented by combined stimulation of the co-stimulatory molecule OX40 and blockade of the inhibitory PD-1 pathway.