Neutralizing Antibody Response to Pseudotype Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Differs Between mRNA-1273 and BNT162b2 Coronavirus Disease 2019 (COVID-19) Vaccines and by History of SARS-CoV-2 Infection

BACKGROUND

Data on the development of neutralizing antibodies (nAbs) against SARS-CoV-2 after SARS-CoV-2 infection and after vaccination with mRNA COVID-19 vaccines are limited.

METHODS

From a prospective cohort of 3975 adult essential and frontline workers tested weekly from August 2020 to March 2021 for SARS-CoV-2 infection by reverse transcription-polymerase chain reaction assay irrespective of symptoms, 497 participants had sera drawn after infection (170), vaccination (327), and after both infection and vaccination (50 from the infection population). Serum was collected after infection and each vaccine dose. Serum-neutralizing antibody titers against USA-WA1/2020-spike pseudotype virus were determined by the 50% inhibitory dilution. Geometric mean titers (GMTs) and corresponding fold increases were calculated using t tests and linear mixed-effects models.

RESULTS

Among 170 unvaccinated participants with SARS-CoV-2 infection, 158 (93%) developed nAbs with a GMT of 1003 (95% confidence interval, 766-1315). Among 139 previously uninfected participants, 138 (99%) developed nAbs after mRNA vaccine dose 2 with a GMT of 3257 (2596-4052). GMT was higher among those receiving mRNA-1273 vaccine (GMT, 4698; 3186-6926) compared with BNT162b2 vaccine (GMT, 2309; 1825-2919). Among 32 participants with prior SARS-CoV-2 infection, GMT was 21 655 (14 766-31 756) after mRNA vaccine dose 1, without further increase after dose 2.

CONCLUSIONS

A single dose of mRNA vaccine after SARS-CoV-2 infection resulted in the highest observed nAb response. Two doses of mRNA vaccine in previously uninfected participants resulted in higher nAbs to SARS-CoV-2 than after 1 dose of vaccine or SARS-CoV-2 infection alone. nAb response also differed by mRNA vaccine product.

Immune responses to SARS-Cov-2 variants in adult and elderly mRNA vaccine recipients

Aging is associated with a reduced magnitude of primary immune responses to vaccination and constriction of immune receptor repertoire diversity. Clinical trials demonstrate high efficacy of mRNA based SARS-CoV-2 vaccines in the elderly but concerns about virus variant escape have not been well addressed. Recently, we have conducted an in-depth analysis of humoral and cellular immunity against the early-pandemic virus strain as well as the P.1./Gamma, B.1.617/Delta and B.1.595 SARS-CoV-2 variants in adult and elderly mRNA vaccine recipients. As others have reported, robust immunity required the second dose of vaccine. Older vaccine recipients exhibited an expected 3–5x reduction (but not a complete loss) in neutralizing antibody titers against P.1./Gamma and B.1.595 that did not statistically differ from that measured in adults. Moreover, older vaccinees manifest robust cellular immunity against SARS-CoV-2, including to variants, that remained statistically comparable to the adult group. While the duration of these immune responses remains to be determined over longer periods of time, these results provide reasons for optimism regarding vaccine protection of older adults against SARS-CoV-2 variants. Experiments are currently in progress to determine cellular immunity in adult and older adult mRNA vaccine recipients to Omicron (B.1.1.529), the newest variant of concern. We will present results on T cell polyfunction and production of cytokines in response to Spike protein peptide pool from Omicron variant in a large cohort of convalescents and adult and elderly mRNA vaccine recipients.

CD4 T-cell depletion prevents Lassa fever associated hearing loss in the mouse model

Lassa virus (LASV) is the causative agent of Lassa fever (LF), which presents as a lethal hemorrhagic disease in severe cases. LASV-induced hearing loss in survivors is a huge socioeconomic burden, however, the mechanism(s) leading to hearing loss is unknown. In this study, we evaluate in a mouse LF model the auditory function using auditory brainstem response (ABR) and distortion product otoacoustic emissions (DPOAE) to determine the mechanisms underlying LASV-induced hearing loss. In the process, we pioneered measures of ABR and DPOAE tests in rodents in biosafety level 4 (BSL-4) facilities. Our T cell depletion studies demonstrated that CD4 T-cells play an important role in LASV-induced hearing loss, while CD8 T-cells are critical for the pathogenicity in the acute phase of LASV infection. Results presented in this study may help to develop future countermeasures against acute disease and LASV-induced hearing loss.

Splenocyte transfer from hypertensive donors eliminates premenopausal female protection from ANG II-induced hypertension

Premenopausal females are protected from angiotensin II (ANG II)-induced hypertension following the adoptive transfer of T cells from normotensive donors. For the present study, we hypothesized that the transfer of hypertensive T cells (HT) or splenocytes (HS) from hypertensive donors would eliminate premenopausal protection from hypertension. Premenopausal recombination-activating gene-1 (Rag-1)-/- females received either normotensive (NT) or hypertensive cells 3 wk before ANG II infusion (14 days, 490 ng/kg/min). Contrary to our hypothesis, no increase in ANG II-induced blood pressure was observed in the NT/ANG or HT/ANG groups. Flow cytometry demonstrated that renal FoxP3+ T regulatory cells were significantly decreased, and immunohistochemistry showed an increase in renal F4/80+ macrophages in the HT/ANG group, suggesting a shift in the renal inflammatory environment despite no change in blood pressure. Renal mRNA expression of macrophage chemoattractant protein-1 (MCP-1), endothelin-1 (ET-1), and G protein-coupled estrogen receptor-1 (GPER-1) was significantly decreased in the HT/ANG group. The adoptive transfer of hypertensive splenocytes before ANG II infusion (HS/ANG) eliminated premenopausal protection from hypertension and significantly decreased splenic FoxP3+ T regulatory cells compared with females that received normotensive splenocytes (NS/ANG). Expression of macrophage inflammatory protein 1α/chemokine (C-C motif) ligand 3 (MCP-1/CCL3), a potent macrophage chemokine, was elevated in the HS/ANG group; however, no increase in renal macrophage infiltration occurred. Together, these data show that in premenopausal females, T cells from hypertensive donors are not sufficient to induce robust ANG II-mediated hypertension; in contrast, transfer of hypertensive splenocytes (consisting of T/B lymphocytes, dendritic cells, and macrophages) is sufficient. Further work is needed to understand how innate and adaptive immune cells and estrogen signaling coordinate to cause differential hypertensive outcomes in premenopausal females.NEW & NOTEWORTHY Our study is the first to explore the role of hypertensive T cells versus hypertensive splenocytes in premenopausal protection from ANG II-induced hypertension. We show that the hypertensive status of T cell donors does not impact blood pressure in the recipient female. However, splenocytes, when transferred from hypertensive donors, significantly increased premenopausal recipient blood pressure following ANG II infusion, highlighting the importance of further investigation into estrogen signaling and immune cell activation in females.

The OM-85 bacterial lysate inhibits SARS-CoV-2 infection of epithelial cells by downregulating SARS-CoV-2 receptor expression

Background

Treatments for coronavirus disease 2019, which is caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), are urgently needed but remain limited. SARS-CoV-2 infects cells through interactions of its spike (S) protein with angiotensin-converting enzyme 2 (ACE2) and transmembrane protease serine 2 (TMPRSS2) on host cells. Multiple cells and organs are targeted, particularly airway epithelial cells. OM-85, a standardized lysate of human airway bacteria with strong immunomodulating properties and an impeccable safety profile, is widely used to prevent recurrent respiratory infections. We found that airway OM-85 administration inhibits Ace2 and Tmprss2 transcription in the mouse lung, suggesting that OM-85 might hinder SARS-CoV-2/host cell interactions.

Objectives

We sought to investigate whether and how OM-85 treatment protects nonhuman primate and human epithelial cells against SARS-CoV-2.

Methods

ACE2 and TMPRSS2 mRNA and protein expression, cell binding of SARS-CoV-2 S1 protein, cell entry of SARS-CoV-2 S protein–pseudotyped lentiviral particles, and SARS-CoV-2 cell infection were measured in kidney, lung, and intestinal epithelial cell lines, primary human bronchial epithelial cells, and ACE2-transfected HEK293T cells treated with OM-85 in vitro.

Results

OM-85 significantly downregulated ACE2 and TMPRSS2 transcription and surface ACE2 protein expression in epithelial cell lines and primary bronchial epithelial cells. OM-85 also strongly inhibited SARS-CoV-2 S1 protein binding to, SARS-CoV-2 S protein–pseudotyped lentivirus entry into, and SARS-CoV-2 infection of epithelial cells. These effects of OM-85 appeared to depend on SARS-CoV-2 receptor downregulation.

Conclusions

OM-85 inhibits SARS-CoV-2 epithelial cell infection in vitro by downregulating SARS-CoV-2 receptor expression. Further studies are warranted to assess whether OM-85 may prevent and/or reduce the severity of coronavirus disease 2019.

Research and resource needs for understanding host immune responses to SARS-CoV-2 and COVID-19 vaccines during aging

On 16 and 17 March 2021, the National Institute of Allergy and Infectious Diseases and the National Institute of Aging convened a virtual workshop to discuss developments in SARS-CoV-2 research pertaining to immune responses in older adults, COVID-19 vaccines in both aged animals and older individuals, and to gain some perspective on the critical knowledge gaps that need addressing to establish scientific priorities for future research studies.

COVID-19 Infection, Reinfection, and Vaccine Effectiveness in a Prospective Cohort of Arizona Frontline/Essential Workers: The AZ HEROES Research Protocol

BACKGROUND

The Arizona Healthcare, Emergency Response, and Other Essential workers Study (AZ HEROES) aims to examine the epidemiology of SARS-CoV-2 infection and COVID-19 illness among adults with high occupational exposure risk.

OBJECTIVE

Study objectives include estimating incidence of SARS-CoV-2 infection in essential workers by symptom presentation and demographic factors, determining independent effects of occupational and community exposures on incidence of SARS-CoV-2 infection, establishing molecular and immunologic characteristics of SARS-CoV-2 infection in essential workers, describing the duration and patterns of rRT-PCR-positivity, and examining post-vaccine immunologic response.

METHODS

Eligible participants include Arizona residents aged 18-85 years who work at least 20 hours per week in an occupation involving regular direct contact (within three feet) with others. Recruitment goals are stratified by demographic characteristics (50% aged 40 or older, 50% women, and 50% Hispanic or American Indian), by occupation (40% healthcare personnel, 30% first responders, and 30% other essential workers), and by prior SARS-CoV-2 infection (with up to 50% seropositive at baseline). Information on sociodemographics, health and medical history, vaccination status, exposures to individuals with suspected or confirmed SARS-CoV-2 infection, use of personal protective equipment, and perceived risks are collected at enrollment and updated through quarterly surveys. Every week, participants complete active surveillance for COVID-19-like illness (CLI) and self-collect nasal swabs. Additional self-collected nasal swab and saliva specimens are collected in the event of CLI onset. Respiratory specimens are sent to Marshfield Laboratories and tested for SARS-CoV-2 by real-time reverse transcription polymerase chain reaction (rRT-PCR) assay. CLI symptoms and impact on work and productivity are followed through illness resolution. Serum specimens are collected every 3 months and additional sera are collected following incident rRT-PCR positivity and after each COVID-19 vaccine dose. Incidence of SARS-CoV-2 infections will be calculated by person-weeks at risk and compared by occupation and demographic characteristics and by seropositivity status and infection and vaccination history.

RESULTS

The AZ HEROES study was funded by the Centers for Disease Control and Prevention. Enrollment began July 27, 2020 and as of May 1, 2021 a total of 3,165 participants have been enrolled in the study.

CONCLUSIONS

AZ HEROES is unique in aiming to recruit a diverse sample of essential workers and prospectively following strata of SARS-CoV-2 seronegative and seropositive adults. Survey results combined with active surveillance data on exposure, CLI, weekly molecular diagnostic testing, and periodic serology will be used to estimate the incidence of symptomatic and asymptomatic SARS-CoV-2 infection, assess the intensity and durability of immune responses to natural infection and COVID-19 vaccination, and contribute to the evaluation of COVID-19 vaccine effectiveness.

CLINICALTRIAL

INTERNATIONAL REGISTERED REPORT

DERR1-10.2196/28925.

Affinity-Restricted Memory B Cells Dominate Recall Responses to Heterologous Flaviviruses

Memory B cells (MBCs) can respond to heterologous antigens either by molding new specificities through secondary germinal centers (GCs) or by selecting preexisting clones without further affinity maturation. To distinguish these mechanisms in flavivirus infections and immunizations, we studied recall responses to envelope protein domain III (DIII). Conditional deletion of activation-induced cytidine deaminase (AID) between heterologous challenges of West Nile, Japanese encephalitis, Zika, and dengue viruses did not affect recall responses. DIII-specific MBCs were contained mostly within the plasma-cell-biased CD80⁺ subset, and few GCs arose following heterologous boosters, demonstrating that recall responses are confined by preexisting clonal diversity. Measurement of monoclonal antibody (mAb) binding affinity to DIII proteins, timed AID deletion, single-cell RNA sequencing, and lineage tracing experiments point to selection of relatively low-affinity MBCs as a mechanism to promote diversity. Engineering immunogens to avoid this MBC diversity may facilitate flavivirus-type-specific vaccines with minimized potential for infection enhancement.

The role of Interleukin-6 in age-related frailty syndrome

Aging is accompanied by chronic low-grade inflammation – a term which relates to increase in serum levels of cytokines such as interleukin 6 (IL-6), TNF-α and acute phase proteins such as C-reactive protein. Multiple studies in humans have shown that IL-6 most reliably increases with aging. Frailty is a geriatric syndrome characterized by decrease in physical ability and increased vulnerability to stressors. One of the most consistent findings in frail subjects is an elevation of serum IL-6 but we lack research which delineates is this a causational relationship. We developed a mouse model with inducible IL-6 expression (IL-6TET-ON/+ mice) that enables overexpression of IL-6 following stimulation with doxycycline (dox) administrated in food. IL-6 induction was dose dependent and led to increase in frailty as measured by 30-point murine clinical frailty index. Mice induced to express high levels of IL-6 quickly displayed an increase in frailty index, decrease in muscle grip strength and loss of fat. Mice induced to express 3–4 fold increase in IL-6 similar to frail humans displayed similar changes after months of induction. We measured IL-6 levels in serum and various tissues (gut, muscle, adipose, spleen) of aged (28-month-old) frail mice and adult controls as well as dox fed IL-6TET-ON/+ mice. We observed that IL-6 levels were increased in serums and spleen homogenates of aged mice and IL-6TET-ON/+ mice but not in other tissues. We determined that neutrophils were the main producers of IL-6 and their numbers were higher in spleens of aged and IL-6TET-ON/+ mice compared to adult controls. We conclude that elevated IL-6 serum levels are directly associated with age-related frailty and that spleen neutrophils are likely the main producers of IL-6.

SARS-CoV-2 and COVID-19 in older adults: what we may expect regarding pathogenesis, immune responses, and outcomes

SARS-CoV-2 virus, the causative agent of the coronavirus infectious disease-19 (COVID-19), is taking the globe by storm, approaching 500,000 confirmed cases and over 21,000 deaths as of March 25, 2020. While under control in some affected Asian countries (Taiwan, Singapore, Vietnam), the virus demonstrated an exponential phase of infectivity in several large countries (China in late January and February and many European countries and the USA in March), with cases exploding by 30–50,000/day in the third and fourth weeks of March, 2020. SARS-CoV-2 has proven to be particularly deadly to older adults and those with certain underlying medical conditions, many of whom are of advanced age. Here, we briefly review the virus, its structure and evolution, epidemiology and pathogenesis, immunogenicity and immune, and clinical response in older adults, using available knowledge on SARS-CoV-2 and its highly pathogenic relatives MERS-CoV and SARS-CoV-1. We conclude by discussing clinical and basic science approaches to protect older adults against this disease.

Abstract P184: Exploring Sex Differences in Immune Cell Profiles of Male, Premenopausal Female, and Postmenopausal Female Mice to Understand Susceptibility to Immune Mediated Hypertension

T cells are required for the development of hypertension in male and postmenopausal female mice while premenopausal females are protected from T cell mediated hypertension. To better understand sex differences in immune-cell mediated hypertensive responses, we sought to determine if there were any significant differences in the immune cell profiles of premenopausal female (F), VCD-treated postmenopausal female (PMF), and male (M) mice. Spleens were collected from all mice and processed for flow cytometric analysis of T cell populations (n=8/group). Analysis of splenic T cell populations revealed no significant difference in the frequency of CD3+ or CD4+ T cells between groups (CD3+: F 33.4%, PMF 30.3%, M 30.2% of total lymphocytes, CD4+: F 64.8%, PMF 70.7%, M 67.5% of CD3+ cells). However, postmenopausal females had a significantly lower frequency of splenic CD8+ T cells compared to both males and premenopausal females (CD8+: F 27.9%, PMF 19.5%*, M 25.3% of CD3+ cells *p<0.05 vs M and F). Additionally, premenopausal females displayed significantly increased expression of the memory marker CD44 and the anti-inflammatory marker CTLA-4 on CD4+ cells compared to both males and postmenopausal females (MFI CD44: F 334.8*, PMF 269.4, M 280.4, MFI CTLA-4: F 100.7*, PMF 80.9, M 86.8 *p<0.01 vs M and PMF). Additional flow cytometric staining was performed to evaluate sex differences in splenic Antigen Presenting Cell (APC) populations (n=8/group). The frequency of CD11b+ APCs, thought to primarily represent macrophage populations, were significantly reduced in postmenopausal females compared to premenopausal females but there was no significant difference from males (CD11b +: F 14.6%, PMF 11.8%*, M 12.9% of monocytes *p<0.05 vs F). Additionally, CD11c+ dendritic cell populations were found to be significantly reduced in postmenopausal females compared to both males and premenopausal females (CD11c+: F 4.1%, PMF 2.8%*, M 3.9% of all monocytes *p<0.01 vs M and F). Taken together, these results indicate a significant difference in the baseline immune environment between male, premenopausal female and postmenopausal females which likely contribute to sex-differences in susceptibility to immune-mediated hypertension.

Abstract P148: Transcriptomic and Proteomic Analysis of CD4 + T Cells to Identify Sex Differences in Angiotensin II Signaling Pathways

T cells are involved in hypertension pathogenesis in both males and postmenopausal females while premenopausal females are resistant to T cell-mediated Ang II-induced hypertension. The goals of this study were (1) to identify T cell specific proteomic pathways associated with postmenopausal susceptibility to hypertension (2) to identify T cell specific transcriptomic changes associated with premenopausal protection from hypertension. Proteomic analysis was performed on splenic CD4 + T cells isolated from premenopausal and postmenopausal females (VCD, 160 mg/kg/day i.p. 20d) following Ang II infusion (800 ng/kg/min 14d). 384 proteins from CD4 + T cells were identified as differentially expressed following Ang II infusion in premenopausal females. 285 proteins from CD4 + T cells were identified as differentially expressed between premenopausal and postmenopausal females following Ang II infusion. Gene ontology (GO) analysis of pre vs. postmenopausal proteins identified enriched pathways associated with RNA binding, chaperone activity and cellular stress responses. Transcriptomic changes were analyzed, via RNAseq, on isolated splenic CD4 + T cells from premenopausal females, with and without Ang II infusion. Thirty-four genes were identified as differentially expressed in CD4 + T cells following Ang II infusion. GO analysis of Ang II upregulated genes revealed an enrichment of five distinct molecular functions, including antioxidant activity. In a subsequent study to validate the RNAseq, we confirmed that Ang II increased CD4 + T cell mRNA expression of calprotectin (S100a8/S100a9), a calcium and zinc binding protein complex that contributes to antioxidant defense (S100a8: Con 1.0 ± 0.4 vs Ang II 5.0 ± 0.8*; S100a9: Con 1.0 ± 0.4 vs Ang II 6.0 ± 0.8*, *P<0.05 vs Con). Furthermore, we determined that Ang II did not increase calprotectin expression in mice lacking estrogen receptor α (ERKO) (S100a8: ERKO 0.1 ± 0.4 vs ERKO/Ang II 0.3 ± 0.7; S100a9: ERKO 0.2 ± 0.5 vs ERKO/Ang II 0.3 ± 0.6). The current studies demonstrate a role for estrogen in Ang II-induced T cell gene expression and signal transduction, and begin to elucidate the molecular mechanisms of female protection from T cell-mediated hypertension.

Menopause and FOXP3+ Treg cell depletion eliminate female protection against T cell-mediated angiotensin II hypertension

Although it is known that the prevalence and severity of hypertension increases in women after menopause, the contribution of T cells to this process has not been explored. Although the immune system is both necessary and required for the development of angiotensin II (ANG II) hypertension in men, we have demonstrated that premenopausal women are protected from T cell-mediated hypertension. The goal of the current study was to test the hypotheses that 1) female protection against T cell-mediated ANG II hypertension is eliminated following progression into menopause and 2) T regulatory cells (Tregs) provide premenopausal protection against ANG II-induced hypertension. Menopause was induced in Rag-1^-/- mice (via 4-vinylcyclohexene diepoxide), and all mice received a 14-day ANG II infusion. Donor CD3⁺ T cells were adoptively transferred 3 wk before ANG II infusion. In the absence of T cells, systolic blood pressure responses to ANG II were similar to those seen in premenopausal mice (Δ12 mmHg). After adoptive transfer of T cells, ANG II significantly increased systolic blood pressure in postmenopausal females (Δ28 mmHg). A significant increase in F4/80 positive renal macrophages, an increase in renal inflammatory gene expression, along with a reduction in renal expression of mannose receptor C-type 1, a marker for M2 macrophages, accompanied the increase in systolic blood pressure (SBP). Flow cytometric analysis identified that Tregs were significantly decreased in the spleen and kidneys of Rag-1^-/- menopausal mice versus premenopausal females, following ANG II infusion. In a validation study, an anti-CD25 antibody was used to deplete Tregs in premenopausal mice, which induced a significant increase in SBP. These results demonstrate that premenopausal protection against T cell-mediated ANG II hypertension is eliminated once females enter menopause, suggesting that a change in hormonal status upregulates macrophage-induced proinflammatory and T cell-dependent responses. Furthermore, we are the first to report that the presence of Tregs are required to suppress ANG II hypertension in premenopausal females.NEW & NOTEWORTHY Whether progression into menopause eliminated female protection against T cell-mediated hypertension was examined. Menopausal mice without T cells remained protected against angiotensin II (ANG II) hypertension; however, in the presence of T cells, blood pressure responses to ANG II increased significantly in menopause. Underlying mechanisms examined were anti-inflammatory protection provided by T regulatory cells in premenopausal females and renal inflammatory processes involving macrophage infiltration and cytokine activation.

Microbial exposure expands a Ly6C+ subpopulation of long lived naive CD8 T cells with a rapid effector function via type I intereferons

Previously we have described human ‘memory T cells with a naïve phenotype’ which were increased in human subjects recovering from acute West Nile Virus infection (Pulko et al., Nature Immunology, 2016). These cells had a naïve phenotype but exhibited some signs of basal activation and displayed a rapid effector function upon polyclonal stimulation. These findings in humans prompted us to investigate effects of bystander infections on naïve CD8 T cells in mice, and here we have utilized viral (West Nile Virus) and bacterial (Listeria monocytogenes) models but most importantly we investigated naïve T cells under non specific pathogen free (SPF) conditions in B6 mice cohoused with pet shop mice hosting a variety of infections. We describe a novel population of naïve CD8 T cells characterized by expression of a single memory marker Ly6C with similar properties to human ‘memory T cells with a naïve phenotype’. Under basal conditions Ly6C is expressed on ~20% on naïve T cells and is transiently up regulated during acute infection but only on CD5hi cells with higher affinity for self peptide-MHC I complexes. Under conditions of ‘non SPF microbiome’ this population is expanded long term and enriched in the lymph nodes. We show that Ly6C+ naïve CD8s are enriched in the lymph nodes and receive improved homeostatic signals from lymph node stromal cells which lead to upregulation of survival factors such as BCL-2 and extend the lifespan of Ly6C+ cells. Our mechanistic studies have identified type I interferons as the only inflammatory signal required for the induction of this population. However this effect is partially indirect as type I interferon induced expression of Ly6C on CD8 T cells is prevented by MHC I blockade.

Cell-specific inhibition of SMAD2/3 restores lymph node cellularity and germinal center function in aged mice responding to acute chikungunya virus (CHIKV) infection

Targeted delivery of small-molecule inhibitors increases drug efficacy by focusing its action upon specific cell-types without global disruption of signaling pathways. TGFβ is a pleotropic cytokine involved in many cellular processes, including specific regulatory functions during anti-viral immune responses. Previously, we have shown that in aged mice, over-production of TGFβ correlates with decreased immune function. TGFβ neutralization during acute chikungunya virus (CHIKV) infection decreases acute- and chronic- disease severity and improves neutralizing antibody titers. Herein, we selectively interrupted TGFβ signaling during acute CHIKV infection via the delivery of lymph node (LN)-targeting nanoparticles coupled to a small-molecule inhibitor of SMAD2/3 phosphorylation. We show that LN-targeted inhibition of SMAD phosphorylation during the initiation of a viral immune response can restore – to the levels measured in adult mice - the cellular content of the draining lymph node. We further demonstrate that inhibition of TGFβ signaling decreases LN fibrosis and improves the germinal center reaction in aged mice.

Prospective evaluation of frailty and functional independence in older adult trauma patients

BACKGROUND

The aim of our study was to assess the association between frailty and functional status in geriatric trauma patients.

METHODS

3-year(2013-2015) prospective analysis and included all geriatric trauma patients(≥65y) discharged to a single rehabilitation center from our level-I trauma center. Frailty was measured using Trauma-Specific-Frailty-Index(TSFI) while Functional status was assessed using functional-independence-measure(FIM) at admission and discharge from rehabilitation center. Multivariate linear regression analysis was performed.

RESULTS

267 patients were enrolled. Mean age was 76.9 ± 7.1y, 63.6% were males. Overall, 22.8% were frail, and 37.4% were pre-frail. On linear regression, higher motor-FIM, higher cognitive-FIM scores at admission, and longer length-of-stay at rehab were independently associated with increased discharge FIM score. While, ISS(injury-severity-score), pre-frail and frail status were negatively correlated with FIM gain.

CONCLUSION

Frail patients were less likely to recover to their baseline functional status compared with non-frail patients. Early focused intervention in frail elderly patients is warranted to improve functional status in this population.

Abstract 020: Sex Difference in T Regulatory Cells After Adoptive Transfer From Hypertensive Donors Leads to Protection Against T Cell-Mediated Hypertension in Premenopausal Female Mice

Activation of T cell-dependent pro-inflammatory responses are required for Ang II hypertension in male mice. However, females are protected from T cell-mediated hypertension and may suppress hypertension by directly preventing Ang II-induced pro-inflammatory T cell activation. Here we sought to determine whether transferring T cells from hypertensive donor mice eliminates female protection against T cell-mediated hypertension. Splenic CD3 + T cells were transferred from normotensive (NT) or Ang II-hypertensive (HT) C57BL/6J male donors to female Rag-1 -/- (NT T cell female-NTF; HT T cell female-HTF) or male Rag-1 -/- (HT T cell male-HTM) recipient mice. Blood pressure was monitored (tail cuff) for 5 weeks post-transfer. Ang II (490ng/kg/min) was infused into recipient mice for 14 days during weeks 4 and 5 post-transfer (NTFA; HTFA; HTMA). Ang II significantly increased MAP in donor male mice (NT 114 vs HT 157 mmHg, p<0.05). Transfer of T cells from HT donors did not induce HT in female or male recipients. Similarly, T cell donor environment did not affect Ang II-induced blood pressure in female recipients, which remained protected compared to male recipients (MAP: NTF 83 + 4 mmHg*, HTF 88 + 6 mmHg*, NTFA 101 + 5 mmHg*, HTFA 103 + 5 mmHg*, HTMA 138 + 3 mmHg, *p<0.05 vs HTMA). Flow cytometry demonstrated similar splenic T cell frequency across all groups (CD3: NTF 18%, NTFA 16%, HTF 17%, HTFA 14%, HTMA 18%, p>0.05). However, regulatory T cells were significantly reduced in male recipients compared to all female groups (Foxp3: NTF 21.6%*, NTFA 22.2%*, HTF 22.8%*, HTFA 22.6%*, HTMA 15.3%, *p<0.05 vs HTMA) Females had significantly less renal T cell infiltration compared to males and infiltration was not impacted by Ang II infusion or T cell donor status (CD3: NTF 12,083*, NTFA 11,317*, HTF 12,656*, HTFA 8,997*, HTMA 22,405, *p<0.05 vs HTMA; CD4: NTF 6,411*, NTFA 4,702*, HTF 5,831*, HTFA 4,579*, HTMA 9,914, *p<0.05 vs HTMA; CD8: NTF 5,397*, NTFA 6,123*, HTF 6,362*, HTFA 3,792*, HTMA 11,727, *p<0.05 vs HTMA). These results demonstrate that female mice prevent T cell-mediated hypertension and renal T cell infiltration regardless of previous T cell exposure to a hypertensive environment, suggesting a direct preventive mechanism in females against pro-hypertensive T cell responses.

Recovery of HIV-mediated Immune Aging of T Cells in Virologically Controlled HIV-Infected Patients on Antiretroviral Therapy

Several studies have shown that HIV infection induces an accelerated aging of T cells, immunosenescence, and alterations in T cell homeostasis resulting in dysregulation of T cell function and rapid HIV disease progression in infected individuals. We have investigated whether long term antiretroviral therapy (ART), which successfully controls viremia and restores CD4 T cell counts in HIV-infected individuals, is correlated with reversal of immunosenescence and/or improved homeostasis of T cells in 100 virologically controlled HIV-infected individuals. We show that the median frequencies of immunosenescence of T cells (CD4+/CD8+ CD28−, CD27−, CD57+ and CD28−CD57+ T cells), were higher in the HIV-infected cohort than the uninfected cohort, however, senescent T cells significantly decreased with increasing CD4 T cell counts in HIV-infected individuals. Although overall levels of naïve CD4+ and CD8+ T cells were lower in HIV-infected than uninfected individuals, there was a significant increase in both CD4+ and CD8+ naïve T cells with increasing CD4 T cell counts in HIV-infected individuals. In addition, the increase in naïve CD4+ and CD8+ T cells in HIV-infected individuals was due to recent thymic immigrants expressing CD31+ marker; however, with increasing CD4 T cells counts accumulation of CD4+CD31− T cells were seen. Moreover, the CD4+ T cells of HIV-infected individuals produced cytokines, including IL-2, IL-10 and IFN-g comparable to uninfected individuals. In conclusion, HIV-infected individuals with controlled viremia and restored CD4 T cell counts due to prolonged ART showed significant reduction in T cell immunoscenesce and improvement of T cell homeostasis and function.

Known unknowns: how might the persistent herpesvirome shape immunity and aging?

The microbial community that colonizes all living organisms is gaining appreciation for its contributions to both physiologic and pathogenic processes. The virome, a subset of the overall microbiome, large and diverse, including viruses that persistently inhabit host cells, endogenous viral elements genomically or epigenomically integrated into cells, and viruses that infect the other (bacterial, protozoan, fungal, and archaeal) microbiome phylla. These viruses live in the organism for its life, and therefore are to be considered part of the aging process experienced by the organism. This review considers the impact of the persistent latent virome on immune aging. Specific attention will be devoted to the role of herpesviruses, and within them, the cytomegalovirus, as the key modulators of immune aging.

Human Monocyte Subsets Are Transcriptionally and Functionally Altered in Aging in Response to Pattern Recognition Receptor Agonists

Age-related alterations in immunity have been linked to increased incidence of infections and decreased responses to vaccines in the aging population. Human peripheral blood monocytes are known to promote Ag presentation and antiviral activities; however, the impact of aging on monocyte functions remains an open question. We present an in-depth global analysis examining the impact of aging on classical (CD14⁺CD16^-), intermediate (CD14⁺CD16⁺), and nonclassical (CD14^dimCD16⁺) monocytes. Monocytes sorted from nonfrail healthy adults (21-40 y) and old (≥65 y) individuals were analyzed after stimulation with TLR4, TLR7/8, and retinoic acid-inducible gene I agonists. Our data showed that under nonstimulated conditions, monocyte subsets did not reveal significant age-related alternations; however, agonist stimulated-monocytes from adults and old subjects did show differences at the transcriptional and functional levels. These alternations in many immune-related transcripts and biological processes resulted in reduced production of IFN-α, IFN-γ, IL-1β, CCL20, and CCL8, and higher expression of CX3CR1 in monocytes from old subjects. Our findings represent a comprehensive analysis of the influence of human aging on pattern recognition receptors signaling and monocyte functions, and have implications for strategies to enhance the immune response in the context of infection and immunization.

Comprehensive analysis of serum and innate immune cells revealed age-related alternations

Age-related alterations in immunity have been linked to increased incidence of infections and decreased responses to vaccines in the aging population. These immune dysfunctions, termed immunosenescence, have been linked to the intricate interactions between the innate and adaptive immune responses. The impact of aging on innate immunity remains an open question. We performed a comprehensive analysis of serum and peripheral blood mononuclear cells (PMBCs) isolated from healthy non-frail adults (≤ 40 years) and old individuals (≥ 65 years). The basal level of circulating inflammatory cytokines and chemokines were measured, as well as transcriptome data was analyzed for both ex vivo and agonist stimulated DCs and monocyte subsets. We observed that sorted DC (BDCA-1, -2, and -3) and monocyte (CD14+CD16−,CD14dimCD16+, and CD14+CD16+) subsets were primarily distinct and have unique transcriptional profiles. Under ex vivo conditions, innate subsets did not reveal significant age-related alternations; however, agonist stimulated-monocytes from adults and old subjects did show differences at the transcriptional and functional levels. After stimulation of TLR4 (LPS), TLR7/8 (CLO97), and RIGI (5′-pppRNA), we observed higher production of interferons, CCL8, CCL20, and IL1B in monocytes isolated from adults compared to old individuals. Pathway analysis revealed that innate agonists induced functional pathways in monocytes isolated from both adults and old subjects. Overall, our data reveals a wide range of potential age-associated alternations in pattern recognition receptors (PRRs) signaling and have implications for strategies to enhance the immune response in the context of infection or immunization.

Global analyses of monocyte subsets revealed age-related alternations after stimulation of pathogen recognition receptors

In the aging population, intricate interactions between the innate and adaptive immune response is not as effective compared to younger adults. Monocytes play an important role in defense against microbes and express an array of pattern recognition receptors (PRRs). We applied a comprehensive approach to evaluate the effects of a broad range of innate immune agonists (LPS, CLO97, and 5′pppRNA) on monocyte subsets isolated from healthy non-frail adults and old subjects. We analyzed transcriptome data and measured cytokine and chemokine, ROS, and NO production. Under ex vivo conditions, we observed a larger proportion of genes were specifically upregulated in the classical (CD14+CD16−) and non-classical (CD14dimCD16+) monocytes while the intermediate (CD14+CD16+) monocytes showed a smaller proportion of upregulated genes. Distinct genes observed across both age groups for CD16+ monocytes included: CX3CR1, IL21R, IFITM1/2/3, SIGLEC10, and SOD1; whereas CD16− monocytes expressed CCR1/2, SELL, CD64, CD93, CD36, and CD14. Analysis of the transcriptional profiles elicited by innate agonists revealed age-related alternations in functional pathways. After stimulation of RIGI with 5′pppRNA, we observed that classical monocytes isolated from adults uniquely expressed the RIGI MDA5 mediated induction of IFNα and IFNβ pathway, as well as the IFNα transcript, which corresponded to higher levels of IFNα production. In addition, agonists elicited higher levels of IFNγ from non-classical monocytes isolated from adults. Our findings represent a comprehensive analysis of the influence of human aging on PRRs signaling and have implications for strategies to enhance the immune response in the context of infection or immunization.

An interlaboratory comparison of dosimetry for a multi-institutional radiobiological research project: Observations, problems, solutions and lessons learned

PURPOSE

An interlaboratory comparison of radiation dosimetry was conducted to determine the accuracy of doses being used experimentally for animal exposures within a large multi-institutional research project. The background and approach to this effort are described and discussed in terms of basic findings, problems and solutions.

METHODS

Dosimetry tests were carried out utilizing optically stimulated luminescence (OSL) dosimeters embedded midline into mouse carcasses and thermal luminescence dosimeters (TLD) embedded midline into acrylic phantoms.

RESULTS

The effort demonstrated that the majority (4/7) of the laboratories was able to deliver sufficiently accurate exposures having maximum dosing errors of ≤5%. Comparable rates of 'dosimetric compliance' were noted between OSL- and TLD-based tests. Data analysis showed a highly linear relationship between 'measured' and 'target' doses, with errors falling largely between 0 and 20%. Outliers were most notable for OSL-based tests, while multiple tests by 'non-compliant' laboratories using orthovoltage X-rays contributed heavily to the wide variation in dosing errors.

CONCLUSIONS

For the dosimetrically non-compliant laboratories, the relatively high rates of dosing errors were problematic, potentially compromising the quality of ongoing radiobiological research. This dosimetry effort proved to be instructive in establishing rigorous reviews of basic dosimetry protocols ensuring that dosing errors were minimized.

Abstract P618: Foxp3+ Regulatory T cell Depletion Eliminates Ang II-Induced Hypertension Resistance in Female Mice

Compared to males, premenopausal females are resistant to the development of Ang II hypertension. In males, Ang II induces hypertension, in part, through mechanisms requiring T effector lymphocytes. Recently, our lab has demonstrated that females can prevent the T lymphocyte-dependent increase in blood pressure (SBP and MAP) and expression of pro-inflammatory cytokines in the kidney in response to Ang II infusion. Because Foxp3 + T regulatory cells suppress the pro-inflammatory and hypertensive actions of T effector cells, we sought to determine whether Foxp3 + T regulatory cells contribute to this resistance in females. Premenopausal (8 week old) 129SVE female mice were infused with Ang II (800ng/kg/min, 14d) and received 4 doses of the anti-CD25 antibody PC-61 to transiently deplete Foxp3 + T regulatory cells (every 84 hours beginning 12 hours prior to Ang II infusion, 250μg/dose, i.p., vehicle control). Blood pressure was measured before and after Ang II infusion via non-invasive tail cuff. Ang II induced a significant increase in systolic blood pressure in Foxp3 + -depleted mice, while resistance was retained in vehicle-treated mice (Con Δ5 ± 5mmHg, Ang II Δ10 ± 7mmHg, PC-61 Δ28 ± 9 * mmHg, * p<0.05 vs Con). Flow cytometric analysis demonstrated that PC-61-treatment significantly reduced the number of Foxp3 + splenic T cells compared to control (Con 1.7x10 6 cells, Ang II 2.3x10 6 cells, PC-61 8.3x10 5* cells, * P<0.05 vs Con) without changing CD3 + and CD4 + T cell counts. The number of Foxp3 + T cells residing in the kidney was also significantly reduced by PC-61 (Con 1,152 ± 368 cells, Ang II 686 ± 389 cells, PC-61 210 ± 35 * cells, * P<0.05 vs Con). Quantitative real-time PCR demonstrated that whole kidney expression of MCP-1 and ENaC alpha were significantly increased in Foxp3 + -depleted mice (MCP-1- Con 1.0 ± 0.1, Ang II 1.6 ± 0.4, PC-61 1.8 ± 0.2 * ; ENaC-α- Con 1.0 ± 0.1, Ang II 1.6 ± 0.2, PC-61 2.1 ± 0.1 * , * P<0.05 vs Con). These data suggest that the anti-inflammatory Foxp3 + T regulatory cells play a significant role in mediating the resistance to Ang II hypertension in premenopausal female mice, and may influence renal inflammation and sodium retention during chronic Ang II infusion.

Heterochronic parabiosis: allowing the dissection of the aged immune system (LYM2P.723)

Parabiosis is the surgical union of two organisms resulting in the development of a single, shared circulatory system. When animals of different ages are conjoined (i.e. heterochronic parabiosis), blood-borne factors from the younger animal can often beneficially affect the older animal and recapitulate the youthful phenotype & function in target tissues. However, the effects of heterochronic parabiosis on the aged immune system remain unexplored. An important question to be answered is whether the cellular defects involved in the aged immune system are due to intrinsic deficiencies or if they can be rescued by extrinsic factors. Also, T cell ontogenesis is known to diminish with age due to thymic involution as well as defects in lymphopoiesis that affect pre-T cells. The heterochronic parabiosis model allows testing of contributions of the aged thymus, pre-T cells and of systemic environment in immune aging. The preliminary data demonstrate differential migration patterns of T cells, B cells & dendritic cells as a function of age. Of interest, pre-T cells from either animal adequately seed the opposing thymus and undergo thymopoiesis and other data suggest that there are no intrinsic defects in old thymocytes, but rather of the old thymic environment. That latter defect may not be corrected by heterochronic parabiosis.

Abstract 310: 17-β Estradiol Treatment Prevents Angiotensin II-Induced Hypertension in VCD-Treated Menopausal Female Mice, Independent of Renal T Lymphocyte Infiltration

T lymphocytes are required for the development of Angiotensin II (Ang II) hypertension in male mice. Cycling female mice are protected against Ang II hypertension, and inducing ovarian failure (menopause) eliminates this protection. We have previously shown that female Rag-1 -/- mice with adoptively transferred T cells have significantly reduced renal T cell infiltration compared to males. Therefore, we hypothesized that an increase in renal T cell infiltration underlies the genesis of hypertension in menopausal female mice. 10 week old C57Bl/6 female mice received ip VCD injections for 20 consecutive days to induce ovarian failure. Cyclicity was monitored daily via vaginal cytology. Once in menopause, an osmotic minipump was implanted, releasing Ang II (800ng/kg/min) for 14 days. In a subset of mice, a 17-β estradiol pellet (0.1mg) was implanted subcutaneously. Upon harvest, T cell infiltration was measured via flow cytometry. Baseline blood pressure was similar among all groups. Ang II infusion elicited a significantly greater increase in MAP in menopausal mice compared to cycling control (Ang Δ11±10mmHg vs Meno/Ang Δ32±6, p<0.05), which was prevented by 17-β estradiol replacement (Meno/Ang/E 2 Δ5±2mmHg). Despite elevated MAP, there was no significant increase in renal CD3 + , CD4 + or CD8 + T lymphocyte infiltration in Meno/Ang group vs control. However, 17-β estradiol replacement decreased IL-2 renal mRNA expression (0.45±0.13 fold), and increased IL-10 expression (2.41±0.73 fold) compared to Ang II-treated menopausal mice. Ang II induced glomerular hypertrophy in all groups, independent of hormonal status (Control 2156±54μm 2 vs. Ang 3970±383*μm 2 vs. Meno/Ang 3729±51*μm 2 vs. Meno/E 2 /Ang 3505±71*μm 2 , *p<0.05 vs. control). These results demonstrate that the enhanced hypertensive response to Ang II in VCD-treated menopausal mice results from the loss of estrogen function, and does not require an increase in renal T lymphocyte infiltration. Ang II-induced glomerular hypertrophy occurs independently of blood pressure or hormonal status. The VCD model of ovarian failure is a useful model for investigating the underlying mechanisms of estrogen’s role in blood pressure regulation.

New advances in CMV and immunosenescence

Immunosenescence, defined as the age-associated dysregulation and dysfunction of the immune system, is characterized by impaired protective immunity and decreased efficacy of vaccines. An increasing number of immunological, clinical and epidemiological studies suggest that persistent Cytomegalovirus (CMV) infection is associated with accelerated aging of the immune system and with several age-related diseases. However, current evidence on whether and how human CMV (HCMV) infection is implicated in immunosenescence and in age-related diseases remains incomplete and many aspects of CMV involvement in immune aging remain controversial. The attendees of the 4th International Workshop on "CMV & Immunosenescence", held in Parma, Italy, 25-27th March, 2013, presented and discussed data related to these open questions, which are reported in this commentary.

Sex differences in T-lymphocyte tissue infiltration and development of angiotensin II hypertension

There is extensive evidence that activation of the immune system is both necessary and required for the development of angiotensin II (Ang II)-induced hypertension in males. The purpose of this study was to determine whether sex differences exist in the ability of the adaptive immune system to induce Ang II-dependent hypertension and whether central and renal T-cell infiltration during Ang II-induced hypertension is sex dependent. Recombinant activating gene-1 (Rag-1)(-/-) mice, lacking both T and B cells, were used. Male and female Rag-1(-/-) mice received adoptive transfer of male CD3(+) T cells 3 weeks before 14-day Ang II infusion (490 ng/kg per minute). Blood pressure was monitored via tail cuff. In the absence of T cells, systolic blood pressure responses to Ang II were similar between sexes (Δ22.1 mm Hg males versus Δ18 mm : Hg females). After adoptive transfer of male T cells, Ang II significantly increased systolic blood pressure in males (Δ37.7 mm : Hg; P<0.05) when compared with females (Δ13.7 mm : Hg). Flow cytometric analysis of total T cells and CD4(+), CD8(+), and regulatory Foxp3(+)-CD4(+) T-cell subsets identified that renal lymphocyte infiltration was significantly increased in males versus females in both control and Ang II-infused animals (P<0.05). Immunohistochemical staining for CD3(+)-positive T cells in the subfornical organ region of the brain was increased in males when compared with that in females. These results suggest that female Rag-1(-/-) mice are protected from male T-cell-mediated increases in Ang II-induced hypertension when compared with their male counterparts, and this protection may involve sex differences in the magnitude of T-cell infiltration of the kidney and brain.

Cytomegalovirus and early-life irradiation synergize to erode protective immunity in aging (VIR5P.1034)

Susceptibility to infectious disease increases with age, making it one of the leading causes of death in people over 65. The immune aging process may be accelerated by the presence of life-long latent infections, such as cytomegalovirus, that put a constant burden on the immune system. Theories of biological aging also suggest that immune cells may have defective functions in old age because of a lifetime of self-renewal, and DNA damage related senescence, among other factors. Sub-lethal whole-body irradiation results in dose-dependent death of immune cells throughout the body, forcing some peripheral self-renewal of surviving immune cells. We exposed mice to various sub-lethal irradiation doses (0Gy - 4Gy) in youth, and followed them for life. Some mice were also given life-long murine cytomegalovirus (MCMV) to reflect the most common latent virus in human populations. At the end of life, mice were vaccinated against, and then infected with, a potentially lethal dose of West Nile Virus (WNV). Neither MCMV, nor any dose of sub-lethal irradiation, independently altered survival following vaccination and WNV infection. However, mice that received a combination of 4Gy of irradiation in youth, and life-long MCMV infection, were less likely to survive WNV challenge. Mechanisms and implications for radiobiology, immune aging, and vaccine efficacy will be discussed.

Contrasting effects of chronic, systemic treatment with mTOR inhibitors rapamycin and metformin on adult neural progenitors in mice

The chronic and systemic administration of rapamycin extends life span in mammals. Rapamycin is a pharmacological inhibitor of mTOR. Metformin also inhibits mTOR signaling but by activating the upstream kinase AMPK. Here we report the effects of chronic and systemic administration of the two mTOR inhibitors, rapamycin and metformin, on adult neural stem cells of the subventricular region and the dendate gyrus of the mouse hippocampus. While rapamycin decreased the number of neural progenitors, metformin-mediated inhibition of mTOR had no such effect. Adult-born neurons are considered important for cognitive and behavioral health, and may contribute to improved health span. Our results demonstrate that distinct approaches of inhibiting mTOR signaling can have significantly different effects on organ function. These results underscore the importance of screening individual mTOR inhibitors on different organs and physiological processes for potential adverse effects that may compromise health span.

Acute neonatal infections 'lock-in' a suboptimal CD8+ T cell repertoire with impaired recall responses

Microbial infection during various stages of human development produces widely different clinical outcomes, yet the links between age-related changes in the immune compartment and functional immunity remain unclear. The ability of the immune system to respond to specific antigens and mediate protection in early life is closely correlated with the level of diversification of lymphocyte antigen receptors. We have previously shown that the neonatal primary CD8+ T cell response to replication competent virus is significantly constricted compared to the adult response. In the present study, we have analyzed the subsequent formation of neonatal memory CD8+ T cells and their response to secondary infectious challenge. In particular, we asked whether the less diverse CD8+ T cell clonotypes that are elicited by neonatal vaccination with replication competent virus are ‘locked-in’ to the adult memory T cell, and thus may compromise the strength of adult immunity. Here we report that neonatal memory CD8+ T cells mediate poor recall responses compared to adults and are comprised of a repertoire of lower avidity T cells. During a later infectious challenge the neonatal memory CD8+ T cells compete poorly with the fully diverse repertoire of naïve adult CD8+ T cells and are outgrown by the adult primary response. This has important implications for the timing of vaccination in early life.

Newborns typically have a heightened sensitivity to infectious diseases, the reasons for which are not yet well understood. One contributing factor is the limited diversity of lymphocyte receptors early in life to recognize antigen and control infection. We have previously shown that antigen-specific CD8+ T cell repertoires are significantly constricted in neonates compared with adults. In this study, we addressed the question of whether the developmental stage of the host at the time of vaccination influences the composition of the memory CD8⁺ T cell repertoire and its ability to mount a robust response to subsequent infections. We observed that the antigen-specific T cell repertoires elicited in the context of an acute neonatal infection, that are less diverse and comprised of lower-avidity T cells, are partially ‘locked-in’ to the adult memory T cell repertoire. However, in the face of a secondary infectious challenge, naïve adult T cells outcompete the lower avidity neonatal memory T cells and raise the diversity of the overall CD8⁺ T cell response. These results have potential implications for the design of vaccines to be administered in early life.

Abstract 514: Females are Protected from Hypertension and Kidney and Brain Infiltration of T Lymphocytes During Angiotensin II Infusion

There is extensive evidence that activation of the immune system is both necessary and required for the development of Ang II induced hypertension in males and that the central nervous system (CNS) is involved in this response. The purpose of the present study was to determine if there are sex differences in ability of the adaptive immune system to induce Ang II hypertension and the effect of sex on T-cell infiltration into the brain and kidney during Ang II induced hypertension. Rag-1-/- mice, with a genetic deletion of the recombinase-activating gene and lacking both T and B cells were used in this study. Male (n=4) and female (n=4) Rag-1-/- mice both received adoptive transfer of male CD3+ T cells three weeks prior to 14 day Ang II infusion (490 ng/kg/min). Blood pressure was monitored non-invasively via tail cuff. In Rag-1-/- mice, in the absence of T cells, male and female mean arterial pressure (MAP) responses to Ang II were similar, males increased MAP 14.6 mmHg (107.8mmHg to122.5mmHg) and females increased 14.4 mmHg (102.7mmHg to 117.2 mmHg). However, following adoptive transfer of male CD3+ Tcells, Ang II induced a significantly greater increase in blood pressure in males (delta 37.8 mmHg, 107.2mmHg to 139.5mmHg, p<.05) while female mice had similar changes as seen in controls (delta 16.7 mmHg, 110.1mmHg to126.8mmHg). Flow cytometric analysis of CD3+, CD3+CD4+, CD3+CD4+Foxp3 and CD3+CD8+, lymphocyte surface markers from Rag-1-/- males and females was performed on whole blood, splenic, renal and brain tissue. Absolute CD3+ T cell count from spleen suggested that both sexes had equal T cells engraftment. Males had significantly greater numbers of CD3+CD4+, CD3+CD4+Foxp3 and CD3+CD8+ lymphocyte infiltration of the kidney compared to females in both control and AngII infused animals (p<0.05 comparison of males to females). Males also had significantly increased CD3+CD4+ brain infiltration relative to females. These results suggest that intact female Rag-1-/- mice during Ang II infusion are protected from the hypertensive effects of CD3+ male T cell adoptive transfer as compared to their male counterparts and this protection may involve sex differences in T cell infiltration of the kidney and brain.

Differential function and maintenance of distinct precursor T cell subsets in unimmunized mice with aging (P1302)

While age-related T cell defects in the context of infection are being elucidated, changes in the naïve T cell pool with aging remain poorly understood. We recently showed that unimmunized old mice lose &gt;70% of Ag-specific CD8 T cell precursors, and many of the remaining precursors acquire a “virtual memory” (CD44hiCD62Lhi) phenotype. Here, we demonstrate that unimmunized TCR transgenic mice also undergo massive virtual memory conversion with age. Similar to non-transgenic mice, TCR transgenic virtual memory cells expressed increased levels of IL-15 receptor and were capable of rapid effector function upon both TCR and cytokine triggering. TCR transgenic virtual memory cells exhibited age-related delayed proliferation, suggesting an onset of proliferative senescence. This reduced proliferation could not be explained by the modest increase in expression of exhaustion molecules PD-1and LAG-3. Importantly, in Rag-sufficient OT-I mice, the highest rate of conversion to virtual memory occurred in cells that replaced the transgenic TCRα chain with endogenously recombined TCRα chains; indeed, these cells randomly expressed alternate Vα rearrangements. In contrast, OT-I Rag-/- mice, which cannot rearrange endogenous Vα, contained a small population (&lt;5%) of virtual memory cells, which did not increase with aging. These results identify a new subset of Ag-specific CD8 precursors in unimmunized mice, with distinct age-related maintenance requirements and functional capabilities.

Age-associated increase of low-avidity cytomegalovirus-specific CD8+ T cells that re-express CD45RA

The mechanisms regulating memory CD8(+) T cell function and homeostasis during aging are unclear. CD8(+) effector memory T cells that re-express CD45RA increase considerably in older humans and both aging and persistent CMV infection are independent factors in this process. We used MHC class I tetrameric complexes that were mutated in the CD8 binding domain to identify CMV-specific CD8(+) T cells with high Ag-binding avidity. In individuals who were HLA-A*0201, CD8(+) T cells that expressed CD45RA and were specific for the pp65 protein (NLVPMVATV epitope) had lower avidity than those that expressed CD45RO and demonstrated decreased cytokine secretion and cytolytic potential after specific activation. Furthermore, low avidity NLVPMVATV-specific CD8(+) T cells were significantly increased in older individuals. The stimulation of blood leukocytes with CMV lysate induced high levels of IFN-α that in turn induced IL-15 production. Moreover, the addition of IL-15 to CD45RA(-)CD45RO(+) CMV-specific CD8(+) T cells induced CD45RA expression while Ag activated cells remained CD45RO(+). This raises the possibility that non-specific cytokine-driven accumulation of CMV-specific CD8(+)CD45RA(+) T cells with lower Ag-binding avidity may exacerbate the effects of viral reactivation on skewing the T cell repertoire in CMV-infected individuals during aging.

mTORC1 inhibition pronounces CD8 T cell effector defects in aging (P1233)

Mammalian target of rapamycin complex 1 (mTORC1) is a critical cell nutrient sensor and its role in CD8 T cell development, homeostasis, and fate decisions during infection are becoming increasingly evident. Seminal studies showed that direct mTORC1 inhibition with rapamcyin favored memory CD8 T cell development after infection. Simultaneously, rapamycin was shown to extend lifespan in mice. Whether or not rapamycin treatment alters the CD8 T cell immune response in old mice has not been studied. This question is particularly critical given recent data from our lab that CD8 T cell defects after Listeria monocytogenes (Lm) and West Nile Virus infection are both associated with increased infection mortality in old mice. Therefore, we tested the effect of rapamycin (75μg/kg), when given during the T cell priming phase, on CD8 T cell effector responses in adult (3 months) and old (18 months) mice infected with Lm. We found that mTORC1 inhibition with rapamycin significantly inhibited effector differentiation of antigen-specific CD8 T cells and this was especially pronounced in old mice. Additionally, contrary to previous reports, we measured no benefit on CD8 T cell memory formation in either old or adult mice. Therefore, we conclude that any beneficial effects of rapamycin on memory formation likely come at the cost of effector function, and these effects may be pathogen-specific. Furthermore, rapamycin may not be a suitable candidate for extending lifespan or “Healthspan.”

Varicella zoster-specific CD4+Foxp3+ T cells accumulate after cutaneous antigen challenge in humans

We investigated the relationship between varicella zoster virus (VZV)-specific memory CD4(+) T cells and CD4(+)Foxp3(+) regulatory T cells (Tregs) that accumulate after intradermal challenge with a VZV skin test Ag. VZV-specific CD4(+) T cells were identified with a MHC class II tetramer or by intracellular staining for either IFN-γ or IL-2 after Ag rechallenge in vitro. VZV-specific T cells, mainly of a central memory (CD45RA(-)CD27(+)) phenotype, accumulate at the site of skin challenge compared with the blood of the same individuals. This resulted in part from local proliferation because >50% of tetramer defined Ag-specific CD4(+) T cells in the skin expressed the cell cycle marker Ki67. CD4(+)Foxp3(+) T cells had the characteristic phenotype of Tregs, namely CD25(hi)CD127(lo)CD39(hi) in both unchallenged and VZV challenged skin and did not secrete IFN-γ or IL-2 after antigenic restimulation. The CD4(+)Foxp3(+) T cells from unchallenged skin had suppressive activity, because their removal led to an increase in cytokine secretion after activation. After VZV Ag injection, Foxp3(+)CD25(hi)CD127(lo)CD39(hi) T cells were also found within the VZV tetramer population. Their suppressive activity could not be directly assessed by CD25 depletion because activated T cells in the skin were also CD25(+). Nevertheless, there was an inverse correlation between decreased VZV skin responses and proportion of CD4(+)Foxp3(+) T cells present, indicating indirectly their inhibitory activity in vivo. These results suggest a linkage between the expansion of Ag-specific CD4(+) T cells and CD4(+) Tregs that may provide controlled responsiveness during Ag-specific stimulation in tissues.

IRF-3, IRF-5, and IRF-7 coordinately regulate the type I IFN response in myeloid dendritic cells downstream of MAVS signaling

Although the transcription factors IRF-3 and IRF-7 are considered master regulators of type I interferon (IFN) induction and IFN stimulated gene (ISG) expression, Irf3^−/−×Irf7^−/− double knockout (DKO) myeloid dendritic cells (mDC) produce relatively normal levels of IFN-β after viral infection. We generated Irf3^−/−×Irf5^−/−×Irf7^−/− triple knockout (TKO) mice to test whether IRF-5 was the source of the residual induction of IFN-β and ISGs in mDCs. In pathogenesis studies with two unrelated positive-sense RNA viruses (West Nile virus (WNV) and murine norovirus), TKO mice succumbed at rates greater than DKO mice and equal to or approaching those of mice lacking the type I IFN receptor (Ifnar^−/−). In ex vivo studies, after WNV infection or exposure to Toll-like receptor agonists, TKO mDCs failed to produce IFN-β or express ISGs. In contrast, this response was sustained in TKO macrophages following WNV infection. To define IRF-regulated gene signatures, we performed microarray analysis on WNV-infected mDC from wild type (WT), DKO, TKO, or Ifnar^−/− mice, as well as from mice lacking the RIG-I like receptor adaptor protein MAVS. Whereas the gene induction pattern in DKO mDC was similar to WT cells, remarkably, almost no ISG induction was detected in TKO or Mavs^−/− mDC. The relative equivalence of TKO and Mavs^−/− responses suggested that MAVS dominantly regulates ISG induction in mDC. Moreover, we showed that MAVS-dependent induction of ISGs can occur through an IRF-5-dependent yet IRF-3 and IRF-7-independent pathway. Our results establish IRF-3, -5, and -7 as the key transcription factors responsible for mediating the type I IFN and ISG response in mDC during WNV infection and suggest a novel signaling link between MAVS and IRF-5.

Host pathogen sensors, including those of the Toll-like receptor and RIG-I like receptor (RLR) families, detect viral infection in cells. Signaling through these receptors triggers expression of type I interferon (IFN) and IFN-stimulated genes (ISGs), in part through the IRF family of transcription factors. Previous studies with West Nile virus (WNV) showed that IRF-3 and IRF-7 control IFN expression in fibroblasts and neurons, whereas macrophages and myeloid dendritic cells (mDC) retained the ability to induce IFN-β without IRF-3 and IRF-7. In the current study, we generated Irf3^−/−×Irf5^−/−×Irf7^−/− (TKO) mice to characterize the contributions of specific IRF transcription factors to IFN and ISG induction in response to WNV infection in cells and in mice. We found that induction of IFN and ISGs was largely abolished in TKO mDC, but sustained in TKO macrophages. Because IFN and ISG induction also was absent in mDC lacking MAVS, a key mediator of RLR signaling, our results suggest a novel signaling link between IRF-5 and MAVS. This study establishes the molecular pathways responsible for IFN induction in mDC and suggests a cross-talk between IRF-5 and RLR signaling pathways.

CMV and Immunosenescence: from basics to clinics

Alone among herpesviruses, persistent Cytomegalovirus (CMV) markedly alters the numbers and proportions of peripheral immune cells in infected-vs-uninfected people. Because the rate of CMV infection increases with age in most countries, it has been suggested that it drives or at least exacerbates “immunosenescence”. This contention remains controversial and was the primary subject of the Third International Workshop on CMV & Immunosenescence which was held in Cordoba, Spain, 15-16^th March, 2012. Discussions focused on several main themes including the effects of CMV on adaptive immunity and immunosenescence, characterization of CMV-specific T cells, impact of CMV infection and ageing on innate immunity, and finally, most important, the clinical implications of immunosenescence and CMV infection. Here we summarize the major findings of this workshop.

Report from the second cytomegalovirus and immunosenescence workshop

The Second International Workshop on CMV & Immunosenescence was held in Cambridge, UK, 2-4^th December, 2010. The presentations covered four separate sessions: cytomegalovirus and T cell phenotypes; T cell memory frequency, inflation and immunosenescence; cytomegalovirus in aging, mortality and disease states; and the immunobiology of cytomegalovirus-specific T cells and effects of the virus on vaccination. This commentary summarizes the major findings of these presentations and references subsequently published work from the presenter laboratory where appropriate and draws together major themes that were subsequently discussed along with new areas of interest that were highlighted by this discussion.

Functional CD8 T cell memory responding to persistent latent infection is maintained for life

Aging is associated with depressed naive T cell responses, but it is less clear whether T cell memory established early in life also becomes impaired with age. This is particularly important for T cells responding to latent persistent infection, which need to remain functional and capable of controlling the infection over the lifetime; however, repeated stimulation over the lifetime may dysregulate their maintenance or function, potentially contributing to impaired immunity in the elderly. Systemic infection with HSV-1, a persistent latent virus, is associated with memory inflation of virus-specific CD8 T cells. We tested how these inflated memory cells are maintained from adulthood into old age. We found no significant differences in the numbers (i.e., blood, spleen), ex vivo Ag-specific IFN-γ production, and in vivo recall response to HSV-1 (i.e., proliferation, IFN-γ production, cytolysis) between adult and old memory T cells. There was a discrete shift from dominantly effector memory phenotype in the adults to a central memory-like phenotype in the old mice, with fewer old cells expressing the killer cell lectin-like receptor G1 (KLRG1). Adult and old KLRG1(+) memory CD8 T cells were functionally identical: both produced IFN-γ but could minimally proliferate in response to viral challenge. Interestingly, regardless of age, KLRG1(+) cells retained the ability to proliferate and survive in response to homeostatic signals, both in vitro (culture with IL-7 and IL-15) and in vivo (expansion following transfer into lymphopenic recipients). This finding demonstrates that functional effector memory T cells, including those expressing KLRG-1, are maintained and are functional for life, despite the presence of persistent viral infection.

Cytomegalovirus-specific T cell immunity is maintained in immunosenescent rhesus macaques

Although CMV infection is largely benign in immunocompetent people, the specific T cell responses associated with control of this persistent virus are enormous and must be maintained for life. These responses may increase with advanced age and have been linked to an "immune risk profile" that is associated with poor immune responsiveness and increased mortality in aged individuals. Based on this association, it has been suggested that CMV-specific T cell responses might become dysfunctional with age and thereby contribute to the development of immune senescence by homeostatic disruption of other T cell populations, diminished control of CMV replication, and/or excess chronic inflammation. In this study, we use the rhesus macaque (RM) model of aging to ask whether the quantity and quality of CMV-specific T cell responses differ between healthy adult RMs and elderly RMs that manifest hallmarks of immune aging. We demonstrate that the size of the CD4(+) and CD8(+) CMV-specific T cell pools are similar in adult versus old RMs and show essentially identical phenotypic and functional characteristics, including a dominant effector memory phenotype, identical patterns of IFN-γ, TNF-α, and IL-2 production and cytotoxic degranulation, and comparable functional avidities of optimal epitope-specific CD8(+) T cells. Most importantly, the response to and protection against an in vivo CMV challenge were identical in adult and aged RMs. These data indicate that CMV-specific T cell immunity is well maintained in old RMs and argue against a primary role for progressive dysfunction of these responses in the development of immune senescence.

Immune responses in the skin in old age

A marked increase in the susceptibility to cutaneous infections and malignancies has been observed in older humans indicating that cutaneous immunity becomes defective with age. In this review we will focus on recent developments in the understanding of age-related changes in immune function of the skin with a particular emphasis on how alterations in the interaction between cells involved in innate and adaptive immunity leads to decreased cutaneous antigen-specific T cell immunosurveillance.

Molecular dissection of T-cell differentiation defects in the old CD8 T cell (113.12)

One in eight people are 65 years and older in the United States; this population is expected to double within the next 50 years. Alarmingly, infectious diseases remain amongst the leading causes for death in people over 65 years old. Widespread defects in the immune system have been found to increase with age, including qualitative and quantitative decline with adaptive immunity. CD8 T cells have been found to decrease in both number and function in aged mice. We recently found that in response to systemic Listeria monocytogenes (Lm) infection, old mice mobilize fewer Lm-specific CD8 T cells. Moreover, these cells exhibited lower effector cytokine production, and are less polyfunctional. We evaluated the expression of key transcription factors crucial to effector CD8 T cell development in adult and old CD8 T cells in the mouse. We found that in response to in vivo stimulation, old CD8 T cells exhibited altered expression of T-homeobox transcription factors , correlating with lower expression of interferon-gamma (IFNγ), tumor necrosis factor alpha (TNFα) and granzyme B. Altered transcriptional activation may constitute a common denominator underlying suboptimal function of old CD8 T cells in response to primary infection. Experiments are in progress to correct these defects and improve function of aged CD8 T cells.

Repeated in vivo stimulation of T and B cell responses in old mice generates protective immunity against lethal West Nile virus encephalitis

Older adults exhibit higher morbidity and mortality from infectious diseases compared with those of the general population. The introduction and rapid spread of West Nile virus (WNV) throughout the continental United States since 1999 has highlighted the challenge of protecting older adults against emerging pathogens: to this day there is no therapy or vaccine approved for human use against West Nile encephalitis. In this study, we describe the characterization of T and B cell responses in old mice after vaccination with RepliVAX WN, a novel West Nile encephalitis vaccine based on single-cycle flavivirus particles. In adult mice, RepliVAX WN induced robust and long-lasting CD4(+) and CD8(+) T cell and Ab (B cell) responses against natural WNV epitopes, similar to those elicited by primary WNV infection. Primary and memory T and B cell responses in old mice against RepliVAX WN vaccination were significantly lower than those seen in younger mice, similar to the response of old mice to infection with WNV. Surprisingly, both the quality and the quantity of the recall Ab and T cell responses in vaccinated old mice were improved to equal or exceed those in adult animals. Moreover, these responses together (but not individually) were sufficient to protect both old and adult mice from severe WNV disease upon challenge. Therefore, at least two cycles of in vivo restimulation are needed for selection and expansion of protective lymphocytes in older populations, and live, single-cycle virus vaccines that stimulate both cellular and humoral immunity can protect older individuals against severe viral disease.

Evolution of the antigen-specific CD8+ TCR repertoire across the life span: evidence for clonal homogenization of the old TCR repertoire

Defects in T cell responses against pathogens and reduced diversity of TCRs have been described at both extremes of the life span. Yet, we still lack information on how Ag-specific T cell populations are maintained and/or altered from birth to old age. In this study, for the first time to our knowledge, we provide insight into Ag-specific TCR repertoire changes over the life span at the single-cell level. We have examined the TCR diversity of the primary CD8(+) T cell response to the immunodominant HSV-1 epitope HSV glycoprotein B 495-502 (HSV gB(498-505); SSIEFARL) (gB-8p) in neonatal, adult, and old C57BL/6 mice. The global distinctive features of the gB-8p-specific TCR repertoire were preserved in mice of different ages. However, both old and especially neonatal mice exhibited significant decreases in TCR diversity compared with that of adult mice. Still, although the neonatal Ag-specific repertoire comprised expectedly shorter germline-biased CDR3β lengths, the repertoire was surprisingly complex, and only a minority of responding cells lacked random nucleotide additions. Changes with aging included increased use of the already dominant TCRVβ10 family, a trend for lower content of the TCR containing the germline WG motif in the CDR3, and a remarkable sharing of one dominant clonotype between individual old mice, implying operation of selective mechanisms. Implications for the rational design of vaccines for neonates and the elderly are discussed.