Aziz Alami Chentoufi

Immune function declines with age, leading to increased vulnerability of the elderly to viral infectious pathogens. The mechanisms by which aging negatively impacts the innate and adaptive immune system, leading to enhanced susceptibility to respiratory viral pathogens, remain incompletely understood. In the present study, we utilized a mouse model of infection with herpes simplex virus type 1 (HSV-1), a virus that can infect the lungs and lead to pneumonia, a rare but serious health concern in the elderly. Following intranasal inoculation of young (6 weeks), adult (36 weeks), and aged mice (68 weeks) with HSV-1 (KOS strain) we: (i) compared the local and systemic immune responses to infection in young, adult, and aged mice, and (ii) correlated the level and type of immune responses to protection against HSV-1 infection and disease. Compared to young and adult mice, aged mice displayed: (i) increased activation of epithelial cells with a decreased expression of TLR3; (ii) increased activation of dendritic cells with increased expression of MHC-I, MHC-II, and CD80/86; (iii) decreased production of type-I interferons; (iv) delayed production of anti-inflammatory cytokines and chemokines in the lungs; and (v) impairment frequencies of functional HSV-specific CD107+IFN-γ+CD8+ T cells associated with the increased incidence of viral infection and disease. These findings suggest that age-related impairments in innate and adaptive immune responses may exacerbate respiratory viral infections and disease in the elderly.

Herpes simplex virus type 1 (HSV-1) continues to be one of the most prevalent viral infections globally, with approximately 3.72 billion individuals affected worldwide. A clinical herpes vaccine is still lacking. In the present study, a novel prime/pull/keep vaccine was tested in a human leukocyte antigen transgenic rabbit model of ocular herpes (HLA-A*0201 Tg rabbit). Ten asymptomatic (ASYMP) CD8 ⁺ T-cell peptide epitopes and 3 CD4 ⁺ T-cell epitopes were selected from the HSV-1 glycoproteins D and B (gD and gB), viral tegument proteins (VP11/12 and VP13/14), and the DNA replication-binding helicase (UL9), all preferentially recognized by CD8 ⁺ and CD4 ⁺ T cells from “naturally protected” HSV-1-seropositive healthy ASYMP individuals (who never had recurrent corneal herpetic disease). HLA Tg rabbits were ocularly infected with HSV-1, then during latency at day 30 post-infection, the rabbits were ocularly vaccinated with a recombinant neurotropic AAV8 vector (10 ⁷ GC/ eye) encoding for the 10 CD8 ⁺ T-cell peptide and 4 CD4 ⁺ T-cell peptide (prime), T-cell attracting CXCL-11 (pull), and T-cell keeping IL-2/IL-15 cytokines (keep). The rabbits were followed up for corneal disease and viral loads in tears for 28 days. The frequency, function, and protective efficacy of HSV-specific CD8 ⁺ T cells induced by the prime/pull/keep vaccine were assessed in the trigeminal ganglia (TG), cornea, spleen, and peripheral blood. Compared to the mock group (unvaccinated), the peptides/CXCL11/IL-2/IL-15 vaccine generated frequent resident CD8 ⁺ T cells that infiltrated the TG. In ocularly HSV-1-infected and prime/pull/keep vaccinated rabbits, CD8 ⁺ T cell mobilization and retention into TG were associated with a significant reduction in corneal herpes infection and disease. These findings draw attention to the novel prime/pull/keep therapeutic vaccine strategy to mobilize and retain antiviral T cells to tissues protecting them against herpetic infection and disease. IMPORTANCE: There is an urgent need for a vaccine against widespread human herpes simplex virus infections. The present study demonstrates that immunization of humanized HLA-A*0201 transgenic rabbits with CD8 ⁺ and CD4 ⁺ T-cell epitope peptides (prime)/ CXCL11 (pull)/ IL-2/IL-15 (keep) AAV8-based vaccine triggered mobilization and retention of HSV-1-specific CD8 ⁺ T cells locally in the cornea and TG, the sites of acute and latent herpes infections. Mobilization and retention of antiviral CD8 ⁺ T cells into the cornea and TG of HSV-1-infected rabbits that received the prime/pull/keep vaccine was associated with protection against ocular herpes infection and disease. These results highlight the importance of the prime/pull/keep vaccine strategy to bolster the number and function of protective CD8 ⁺ T cells within infected tissues.

Herpes simplex virus (HSV)-specific CD8⁺ T cells protect mice from herpes infection and disease. However, the phenotype and function of HSV-specific CD8⁺ T cells that play a key role in the “natural” protection seen in HSV-1-seropositive healthy asymptomatic (ASYMP) patients (who have never had clinical herpes disease) remain to be determined. We previously reported that symptomatic (SYMP) patients (who have frequent bouts of recurrent ocular herpes disease) had more undifferentiated and dysfunctional HSV-specific CD8⁺ T cells. In contrast, healthy ASYMP individuals maintained a significantly higher proportion of differentiated polyfunctional CD8⁺ T cells. Here, we report that HSV-specific CD8⁺ T cells from 10 SYMP patients, but not HSV-specific CD8⁺ T cells from 10 ASYMP patients, have phenotypic and functional characteristics of cellular senescence, including: (i) high frequency of senescent (CD57⁺) and exhausted (PD-1⁺) CD8⁺ T cells; (ii) late terminally differentiated (KLRG1⁺), non-proliferating CD8⁺ T cells; (iii) HSV-specific CD8⁺ T cells which decreased in number over time and were not homeostatically maintained, as indicated by a reduction in the number of CD127⁺CD8⁺ T cells; (iv) loss of the co-stimulatory molecule CD28 on HSV-specific CD8⁺ T cells; and (v) decreased production of effector molecules (granzyme B and perforin) by HSV-specific CD8⁺ T cells. Our findings provide insights into the role of senescence in HSV-specific CD8⁺ T cells in susceptibility to recurrent herpes and have implications for T-cell-based immunotherapeutic strategies against recurrent herpes in humans.

CD4⁺ T cells have been found to play critical roles in the control of both acute and chronic Toxoplasma infection. Previous studies identified a protective role for the Toxoplasma CD4⁺ T cell-eliciting peptide AS15 (AVEIHRPVPGTAPPS) in C57BL/6J mice. Herein, we found that immunizing mice with AS15 combined with GLA-SE, a TLR-4 agonist in emulsion adjuvant, can be either helpful in protecting male and female mice at early stages against Type I and Type II Toxoplasma parasites or harmful (lethal with intestinal, hepatic, and spleen pathology associated with a storm of IL6). Introducing the universal CD4⁺ T cell epitope PADRE abrogates the harmful phenotype of AS15. Our findings demonstrate quantitative and qualitative features of an effective Toxoplasma-specific CD4⁺ T cell response that should be considered in testing next-generation vaccines against toxoplasmosis. Our results also are cautionary that individual vaccine constituents can cause severe harm depending on the company they keep.

Human leukocyte antigens (HLA) diversity has a tremendous impact on shaping the transplantation practices, transfusion-associated graft versus host disease prevention strategies, and host–pathogen interactions. Here, we conducted a retrospective study of HLA class I and class II homozygosity at allelic and haplotype levels in unrelated individuals genotyped from 2012 to 2016 in a tertiary hospital in the capital of Saudi Arabia. Among 5,000 individuals, 2,773 individuals meet inclusion criteria and were retrospectively analyzed for HLA-A, -B, -C–DRB1, and -DQB1 homozygosity at allelic and haplotype levels. HLA molecular typing was performed using a commercial reverse sequence-specific oligonucleotide (rSSO) kit. We were able to identify 15 HLA-A, 20 HLA-B, 11 HLA-C, 13 HLA-DRB1, and five HLA-DQB1 homozygous alleles demonstrating a very low genetic diversity in the Saudi population. The highest homozygosity in HLA class I was found in locus C followed by A and B (20.3% > 16.1% > 15.5%; p < 0.001) where the most homozygote alleles were A*02 (9.2%), B*51 and B*50 (5.7% and 3.7%), and C*07, C*06, and C*15 (7.2%, 5.48%, and 3.3%) and in HLA class II, the highest homozygosity was found in locus DQB1 compared to DRB1 (31.71% > 19.2%; p < 0.001), with the most common homozygote alleles being DRB1*07 and DRB1*04 (5.33% and 4.2%) and DQB1*02, DQB1*06, and DQB1*03 (13.55%, 7.92%, and 7.64%). The frequency of finding an individual with one homozygote allele was (24.6%), two homozygote alleles (13.5%), three homozygote alleles (4.7%), four homozygote alleles (3.4%), and five alleles were (4.8%). The most frequent homozygote haplotypes are A*23∼C*06∼B*50∼DRB1*07∼DQB1*02 and A*02∼C*06∼B*50∼DRB1*07∼DQB1*02. This study shows low diversity of both class I and II alleles and haplotypes in the Saudi population, which would have a significant impact on shaping the transplantation practices, transfusion-associated graft versus host disease prevention strategies, and host–pathogen interactions.

Over the last two decades, there have been three deadly human outbreaks of coronaviruses (CoVs) caused by SARS-CoV, MERS-CoV, and SARS-CoV-2, which has caused the current COVID-19 global pandemic. All three deadly CoVs originated from bats and transmitted to humans via various intermediate animal reservoirs. It remains highly possible that other global COVID pandemics will emerge in the coming years caused by yet another spillover of a bat-derived SARS-like coronavirus (SL-CoV) into humans. Determining the Ag and the human B cells, CD4+ and CD8+ T cell epitope landscapes that are conserved among human and animal coronaviruses should inform in the development of future pan-coronavirus vaccines. In the current study, using several immunoinformatics and sequence alignment approaches, we identified several human B cell and CD4+ and CD8+ T cell epitopes that are highly conserved in 1) greater than 81,000 SARS-CoV-2 genome sequences identified in 190 countries on six continents; 2) six circulating CoVs that caused previous human outbreaks of the common cold; 3) nine SL-CoVs isolated from bats; 4) nine SL-CoV isolated from pangolins; 5) three SL-CoVs isolated from civet cats; and 6) four MERS strains isolated from camels. Furthermore, the identified epitopes: 1) recalled B cells and CD4+ and CD8+ T cells from both COVID-19 patients and healthy individuals who were never exposed to SARS-CoV-2, and 2) induced strong B cell and T cell responses in humanized HLA-DR1/HLA-A*02:01 double-transgenic mice. The findings pave the way to develop a preemptive multiepitope pan-coronavirus vaccine to protect against past, current, and future outbreaks.

HSV type 1 (HSV-1) is a prevalent human pathogen that infects >3.72 billion individuals worldwide and can cause potentially blinding recurrent corneal herpetic disease. HSV-1 establishes latency within sensory neurons of trigeminal ganglia (TG), and TG-resident CD8⁺ T cells play a critical role in preventing its reactivation. The repertoire, phenotype, and function of protective CD8⁺ T cells are unknown. Bolstering the apparent feeble numbers of CD8⁺ T cells in TG remains a challenge for immunotherapeutic strategies. In this study, a comprehensive panel of 467 HLA-A*0201–restricted CD8⁺ T cell epitopes was predicted from the entire HSV-1 genome. CD8⁺ T cell responses to these genome-wide epitopes were compared in HSV-1–seropositive symptomatic individuals (with a history of numerous episodes of recurrent herpetic disease) and asymptomatic (ASYMP) individuals (who are infected but never experienced any recurrent herpetic disease). Frequent polyfunctional HSV-specific IFN-γ⁺CD107^a/b+CD44^highCD62L^lowCD8⁺ effector memory T cells were detected in ASYMP individuals and were primarily directed against three “ASYMP” epitopes. In contrast, symptomatic individuals have more monofunctional CD44^highCD62L^highCD8⁺ central memory T cells. Furthermore, therapeutic immunization with an innovative prime/pull vaccine, based on priming with multiple ASYMP epitopes (prime) and neurotropic TG delivery of the T cell–attracting chemokine CXCL10 (pull), boosted the number and function of CD44^highCD62L^lowCD8⁺ effector memory T cells and CD103^highCD8⁺ tissue-resident T cells in TG of latently infected HLA-A*0201–transgenic mice and reduced recurrent ocular herpes following UV-B–induced reactivation. These findings have profound implications in the development of T cell–based immunotherapeutic strategies to treat blinding recurrent herpes infection and disease.

The best hope of controlling the herpes simplex virus type 1 and type 2 (HSV-1 and HSV-2) pandemic is the development of an effective vaccine. However, in spite of several clinical trials, starting as early as 1920s, no vaccine has been proven sufficiently safe and efficient to warrant commercial development. In recent years, great strides in cellular and molecular immunology have stimulated creative efforts in controlling herpes infection and disease. However, before moving towards new vaccine strategy, it is necessary to answer two fundamental questions: (i) why past herpes vaccines have failed? (ii) Why the majority of HSV seropositive individuals (i.e., asymptomatic individuals) are naturally “protected” exhibiting few or no recurrent clinical disease, while other HSV seropositive individuals (i.e., symptomatic individuals) have frequent ocular, orofacial, and/or genital herpes clinical episodes? We recently discovered several discrete sets of HSV-1 symptomatic and asymptomatic epitopes recognized by CD4⁺and CD8⁺T cells from seropositive symptomatic versus asymptomatic individuals. These asymptomatic epitopes will provide a solid foundation for the development of novel herpes epitope-based vaccine strategy. Here we provide a brief overview of past clinical vaccine trials, outline current progress towards developing a new generation “asymptomatic” clinical herpes vaccines, and discuss future mucosal “asymptomatic” prime-boost vaccines that could optimize local protective immunity.