2320. Novel checkpoint modifier lowers T cell activation threshold and enhances and broadens vaccine-induced responses to chronic viral infections

Background

Vaccines aim to induce immune responses that prevent disease. They may also clear chronic infections or reduce tumor progression. Vaccine adjuvants augment immune responses, in general, by providing stimulatory signals. Our focus has been on a different type of adjuvant that enhances vaccine-induced T cell responses by modulating the herpes virus entry mediator (HVEM) pathway. The B and T cell attenuator (BTLA) is expressed on naïve T cells and, upon binding to HVEM on antigen presenting cells, dampens signaling through the T cell receptor. HVEM binds with a different domain to the co-stimulator LIGHT. Within a trimolar BTLA-LIGHT/HVEM complex, inhibition prevails. Herpes simplex virus (HSV-1) glycoprotein D (gD) attaches to the BTLA binding site of HVEM and as it has higher binding affinity outcompetes BTLA binding and allows for co-stimulation through LIGHT. This results in enhanced signaling through the T cell receptor and thereby augments and broadens CD8+ T cell responses as we showed with chimpanzee adenovirus (AdC) vector vaccines for several viral antigens.

Methods

Immunogenicity in rodents was evaluated following one or two immunizations with AdC vectors expressing antigens of HIV (gag), HPV-16 (E7/6/5), HBV (core & pol), influenza virus (nucleoprotein) and SARS-CoV2 (nucleoprotein), with or without gD. Vaccine-induced CD8⁺ T cell responses, including their magnitude, functions, duration, and breadth were characterized. Vaccine efficacy was also evaluated.

Results

Vaccination with gD-antigen fusion proteins increased CD8⁺ T cell frequencies to all of the antigens tested (Fig) and improved efficacy. Addition of gD increased stimulation of CD8⁺ T cells to subdominant epitopes and thereby enhanced breadth of responses.

Conclusion

Checkpoint modification of the HVEM pathway with a gD-antigen fusion protein produces potent, prolonged, and broad responses of CD8⁺ T cells to immunodominant and subdominant epitopes. The latter is especially important for chronic viral infections, where, due to exhaustion of T cells to dominant epitopes therapeutic efficacy of vaccines may rely on expansion of T cells to subdominant epitopes. Clinical studies to evaluate therapeutic vaccination for chronic HBV are planned.

Disclosures

All Authors: No reported disclosures.

Glycoprotein D, a checkpoint inhibitor of early T-cell activation, to improve immunogenicity and efficacy of an HPV-16 vaccine in preclinical studies

71

Background: CD8+ T cells can inhibit tumor progression, but their induction is hampered by the low immunogenicity of most tumor antigens. HSV-1 glycoprotein D (gD), when genetically expressed as a fusion protein with tumor antigens, serves as a checkpoint inhibitor of the B and T cell attenuator (BTLA)-herpes virus entry mediator (HVEM) pathway, which acts early during T cell activation. HSV-1 gD thereby augments antigen-driven CD8+ T cell responses. We describe the immunogenicity and efficacy of a chimpanzee adenoviral vector (AdC) vaccine containing a detoxified E7/E6/E5(AdC-gDE765dt) sequence of HPV-16 fused into gD. Methods: The frequency of HPV-16 E7-specific CD8+ T-cells was assessed by tetramer staining in C57/Bl6 mice 14 days after a single IM vaccination with AdC vectors encoding wild-type or mutant HPV-16 oncoproteins expressed within gD, a non-HVEM-binding form of gD or without gD. Efficacy was tested in a TC-1 tumor cell challenge model with mice receiving no treatment or a single IM vaccine injection 3 days after tumor cell transplantation. Mice were followed for 80 days. Results: The addition of gD increases HPV-16 E7-specific CD8+ T-cell frequencies approximately 10-fold. T cell responses are similar to AdC vaccines expressing wild-type or mutant oncoproteins within gD. All AdC-gDE765dt treated mice show delayed tumor progression after a single vaccination with 50% of animals remaining tumor-free at study completion. Conclusions: These results show that the addition of gD, an early checkpoint inhibitor, which acts locally at the site of T cell stimulation, to an HPV-16 vaccine markedly improves the vaccine’s immunogenicity and efficacy. AdC-gDE765dt is currently in GMP manufacture for Phase 1 investigation in HPV-16 infected patients.

Therapeutic drug monitoring in HIV infection: current status and future directions

BACKGROUND

Highly active antiretroviral therapy (HAART) can suppress viral replication and prolong patient life substantially. However, HAART can fail for a number of reasons, including incomplete adherence, pharmacokinetic factors and the emergence of resistance. Because the number of possible antiretroviral combinations is limited, the use of existing treatment options must be optimized. Whether the application of therapeutic drug monitoring (TDM) in routine clinical practice may help with this purpose remains a subject of debate. However, TDM has been introduced in some centres despite the lack of guidelines for optimal use of this test.

OBJECTIVE

In October 2000, a panel of experts met in Perugia, Italy, to discuss the key issues surrounding the introduction of TDM into routine clinical practice. The purpose of the meeting was to achieve a consensus among panel members on the following issues: (i) validity of data suggesting the utility of TDM in HAART; (ii) patient categories and clinical settings in which TDM may be of most benefit; (iii) target levels of antiretroviral agents; (iv) influence of covariables on target levels of drugs; (v) blood sampling and dosage adjustment strategies; and (vi) future research steps needed to elucidate issues regarding the applicability of TDM in clinical practice.

OUTCOME

This report, which has been updated to include data published or presented at conferences up to the end of August 2001, summarizes the data presented and issues discussed at the meeting. This article will guide the reader through the data and discussions that have allowed the panel to formulate a series of position statements regarding the current status and future applications of TDM in antiretroviral therapy. These statements have been formulated to provide suggestions for the design of future TDM clinical trials, as well as to provide useful points of reflection for centres in which TDM is already in use.

Procalcitonin and CGRP-1 mrna expression in various human tissues

Procalcitonin (PCT) is a highly sensitive and specific marker of systemic bacterial infection and sepsis. In contrast to its diagnostic significance, the cellular sources of plasma procalcitonin remain to be clarified. Two forms of PCT mRNAs originate from calcitonin/calcitonin gene-related peptide gene (CALC-I gene) along with mRNA for calcitonin gene-related peptide-I (CGRP-I). Reverse transcription polymerase chain reaction with newly designed primers detecting different PCT mRNAs and CGRP-I mRNA was used to identify tissues that might contribute to PCT production. Our study indicates that a variety of human tissues (13 of the 16 analyzed overall) express PCT-I, PCT-II, and/or CGRP-I mRNAs, with the highest levels detected for liver, testis, lung, prostate, kidney, and small intestine. Various tissues differ in the proportions of PCT-I, PCT-II, and CGRP-I mRNA expression levels. Thus we demonstrate the complexity of tissue-specific regulation of CALC-I gene expression and suppose a variety of tissues as a potential source of CALC-I-encoded peptides.

[The SPHA technic (solid phase hemadsorption) in syphilis serology. A year's experience in routine laboratory procedure]

The first results in routine syphilis serology with the new solid-phase hemadsorption assay (SPHA) are presented. Sera (63019) were screened by the VDRL test and by the automated hemagglutination assay with Treponema pallidum antigen (AMHA-TP). Samples reactive to one or both of these tests were further examined by the FTA-ABS test, the IgM-FTA-ABS test, the 19S IgM-FTA-ABS test (IgM-FTA-ABS test performed with the 19S fraction of the serum after gelfiltration) and the IgM-SPHA test. IgM-SPHA reactive sera derived from patients who were in the early stage or in the phase of latency (of undefinable duration), further from patients with active neurosyphilis and from 26 patients after reinfection. Erroneous results in the IgM-FTA-ABS test caused by a competitive inhibition of IgM by IgG can be eliminated by the IgM-SPHA method. The agreement between 19S IgM-FTA-ABS test and IgM-SPHA test is above 96.3%. As compared to the fluorescence test, the IgM-SPHA test is simpler to perform and can be easily automated.