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.

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.

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.

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.

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.

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.

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.

Neuroprotective and anti-human immunodeficiency virus activity of minocycline

CONTEXT

The prevalence of human immunodeficiency virus (HIV) central nervous system (CNS) disease has not decreased despite highly active antiretroviral therapy. Current antiretroviral drugs are expensive, have significant adverse effects including neurotoxicity, and few cross the blood-brain barrier.

OBJECTIVE

To examine the ability of minocycline, an antibiotic with potent anti-inflammatory and neuroprotective properties, to protect against encephalitis and neurodegeneration using a rapid, high viral load simian immunodeficiency virus (SIV) model of HIV-associated CNS disease that constitutes a rigorous in vivo test for potential therapeutics.

DESIGN AND SUBJECTS

Five SIV-infected pigtailed macaques were treated with 4 mg/kg per day of minocycline beginning at early asymptomatic infection (21 days after inoculation). Another 6 macaques were inoculated with SIV but remained untreated. Blood and cerebrospinal fluid (CSF) samples were taken on days 7, 10, 14, 21, 28, 35, 43, 56, 70, 77, and 84, and all macaques were humanely killed at 84 days after inoculation, a time that corresponds to late-stage infection in HIV-infected individuals.

MAIN OUTCOME MEASURES

Blood and CSF samples were tested for viral load by real-time reverse transcription-polymerase chain reaction and levels of monocyte chemoattractant protein 1 were quantitated by enzyme-linked immunosorbent assay. The presence and severity of encephalitis was determined by microscopic examination of tissues. Central nervous system inflammation was further assessed by measuring infiltration and activation of macrophages, activation of p38 mitogen-activated protein kinase and expression of amyloid precursor protein by quantitative immunohistochemistry.

RESULTS

Minocycline-treated macaques had less severe encephalitis (P = .02), reduced CNS expression of neuroinflammatory markers (major histocompatibility complex class II, P = .03; macrophage marker CD68 , P = .07; T-cell intracytoplasmic antigen 1, P = .03; CSF monocyte chemoattractant protein 1, P = .001), reduced activation of p38 mitogen-activated protein kinase (P<.001), less axonal degeneration (beta-amyloid precursor protein, P = .03), and lower CNS virus replication (viral RNA, P = .04; viral antigen, P = .04). In in vitro analysis, minocycline suppression of HIV and SIV replication in cultured primary macrophages did not correlate with suppression of activation of p38-mitogen-activated protein kinase pathways, whereas suppression in primary lymphocytes correlated with suppression of p38 activation.

CONCLUSIONS

In this experimental SIV model of HIV CNS disease, minocycline reduced the severity of encephalitis, suppressed viral load in the brain, and decreased the expression of CNS inflammatory markers. In vitro, minocycline inhibited SIV and HIV replication. These findings suggest that minocycline, a safe, inexpensive, and readily available antibiotic should be investigated as an anti-HIV therapeutic.