Evaluation of strategies to modify Anti-SARS-CoV-2 monoclonal antibodies for optimal functionality as therapeutics.

The current global COVID-19 pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has resulted in a public health crisis with more than 168 million cases reported globally and more than 4.5 million deaths at the time of writing. In addition to the direct impact of the disease, the economic impact has been significant as public health measures to contain or reduce the spread have led to country wide lockdowns resulting in near closure of many sectors of the economy. Antibodies are a principal determinant of the humoral immune response to COVID-19 infections and may have the potential to reduce disease and spread of the virus. The development of monoclonal antibodies (mAbs) represents a therapeutic option that can be produced at large quantity and high quality. In the present study, a mAb combination mixture therapy was investigated for its capability to specifically neutralize SARS-CoV-2. We demonstrate that each of the antibodies bind the spike protein and neutralize the virus, preventing it from infecting cells in an in vitro cell-based assay, including multiple viral variants that are currently circulating in the human population. In addition, we investigated the effects of two different mutations in the Fc portion (YTE and LALA) of the antibody on Fc effector function and the ability to alleviate potential antibody-dependent enhancement of disease. These data demonstrate the potential of a combination of two mAbs that target two different epitopes on the SARS-CoV2 spike protein to provide protection against SARS-CoV-2 infection in humans while extending serum half-life and preventing antibody-dependent enhancement of disease.

Pre-transplant immune factors may be associated with BK polyomavirus reactivation in kidney transplant recipients.

BK polyomavirus (BKPyV) reactivation in kidney transplant recipients can lead to allograft damage and loss. The elements of the adaptive immune system that are permissive of reactivation and responsible for viral control remain incompletely described. We performed a prospective study evaluating BKPyV-specific T-cell response, humoral response and overall T-cell phenotype beginning pre-transplant through one year post-transplant in 28 patients at two centers. We performed an exploratory analysis of risk factors for the development of viremia and viruria as well as compared the immune response to BKPyV in these groups and those who remained BK negative. 6 patients developed viruria and 3 developed viremia. BKPyV-specific CD8+ T-cells increased post-transplant in viremic and viruric but not BK negative patients. BKPyV-specific CD4+ T-cells increased in viremic, but not viruric or BK negative patients. Anti-BKPyV IgG antibodies increased in viruric and viremic patients but remained unchanged in BK negative patients. Viremic patients had a greater proportion of CD8+ effector cells pre-transplant and at 12 months post-transplant. Viremic patients had fewer CD4+ effector memory cells at 3 months post-transplant. Exploratory analysis demonstrated lower CD4 and higher total CD8 proportions, higher anti-BKPyV antibody titers and the cause of renal failure were associated BKPyV reactivation. In conclusion, low CD4, high CD8 and increased effector CD8 cells were found pre-transplant in patients who became viremic, a phenotype associated with immune senescence. This pre-transplant T-cell senescence phenotype could potentially be used to identify patients at increased risk of BKPyV reactivation.

BK polyomavirus reactivation after reduced-intensity double umbilical cord blood cell transplantation.

Serial serum samples from 27 patients who underwent double umbilical cord blood transplantation (dUCBT) were analyzed for BK polyomavirus (BKPyV) DNA by real-time PCR and BKPyV-specific immune globulin by ELISA. Clinical data were collected on all patients. All pre-transplant sera had detectable anti-BKPyV IgG. Fifteen patients (56%) had detectable serum BKPyV DNA (median 8.9 × 10(4) copies/ml; range 4.1 × 10(3)-7.9 × 10(6) copies/ml) a median of 40 days (range, 27-733 days) after dUCBT, with highest viral loads on Day 100 assessment. The cumulative probability of developing BKPyV viremia by Day 100 was 0.52 (95% CI, 0.33-0.71). Six of 15 patients with BKPyV viremia experienced hemorrhagic cystitis by Day 100. By Day 100, there was a trend towards higher BKPyV viral loads in sera of patients with hemorrhagic cystitis than in those BKPyV viremic patients without hemorrhagic cystitis (p = 0.06). BKPyV viremia was associated with significantly higher anti-BKPyV IgM values at 6 months post-dUCBT (P = 0.003). BKPyV viremia occurs early after dUBCT and is associated with a detectable humoral immune response by 6 months post-dUBCT.

Immune reconstitution after allogeneic hematopoietic stem cell transplantation is associated with selective control of JC virus reactivation.

JC virus (JCV) causes progressive multifocal leukoencephalopathy (PML) in immunocompromised patients. The mechanism of JCV reactivation and immunity in a transplanted immune system remains unclear. We prospectively studied 30 patients undergoing allogeneic hematopoietic stem cell transplantation (HSCT) and collected blood and urine samples before HSCT and 3, 6, and 12 to 18 months after HSCT. Before HSCT, JCV DNA was detected in 7 of 30 urine, 5 of 30 peripheral blood mononuclear cells (PBMC) and 6 of 30 plasma samples. Although JC viruria remained stable after HSCT with detection in 5 of 21 samples, viremia was detected in only 1 of 22 plasma and none of 22 PBMC samples 12 to 18 months after HSCT. Prevalence of anti-JCV IgG was 83% before HSCT and decreased to 72% at 12 to 18 months. Anti-JCV IgM was rarely detected. JCV-specific CD4(+) and CD8(+) T cell responses increased 12 to 18 months after HSCT. Although JC viruria correlated directly with detection of anti-JCV IgG, the cellular immune response to JCV measured by ELISpot was inversely correlated with anti-JCV IgG response. The diagnosis of acute myelogenous leukemia and age group were 2 independent patient factors associated with significantly reduced cellular immune responses to JCV. This prospective study in HSCT patients provides a model of interactions between the host immune response and viral activation in multiple compartments during the recovery of the immune system.

Detection of JC virus-specific immune responses in a novel humanized mouse model.

Progressive Multifocal Leukoencephalopathy (PML) is an often fatal disease caused by the reactivation of the JC virus (JCV). Better understanding of viral-host interactions has been hampered by the lack of an animal model. Engrafting NOD/SCID/IL-2-Rg (null) mice with human lymphocytes and thymus, we generated a novel animal model for JCV infection. Mice were inoculated with either a PML isolate, JCV Mad-4, or with JCV CY, found in the kidney and urine of healthy individuals. While mice remained asymptomatic following inoculation, JCV DNA was occasionally detected in both the blood and the urine compartments. Mice generated both humoral and cellular immune responses against JCV. Expressions of immune exhaustion marker, PD-1, on lymphocytes were consistent with response to infection. Using this model we present the first in vivo demonstration of virological and immunological differences between JCV Mad-4 and CY. This model may prove valuable for studying JCV host immune responses.

Increased program cell death-1 expression on T lymphocytes of patients with progressive multifocal leukoencephalopathy.

The cellullar immune response is important in the containment of progressive multifocal leukoencephalopathy (PML). We examined program cell death-1 (PD-1) expression, a marker of cellular immune exhaustion, on T lymphocytes in PML. PD-1 expression was elevated on total CD4(+) and CD8(+) T cells (medians 36% and 24%) in PML patients compared with healthy control subjects (medians 14% and 18%; P = 0.0015 and P = 0.033). In PML patients, JC virus (JCV)-specific CD8(+) cytotoxic T lymphocytes expressed PD-1 more frequently than total CD8 T lymphocytes (means 39% and 78%, P = 0.0004). Blocking the PD-1 receptor increased JCV-specific T-cell immune response in a subgroup of PML patients.

Carotid body growth during chronic postnatal hyperoxia.

Rats reared in hyperoxia have smaller carotid bodies as adults. To study the time course and mechanisms underlying these changes, rats were reared in 60% O(2) from birth and their carotid bodies were harvested at various postnatal ages (P0-P7, P14). The carotid bodies of hyperoxia-reared rats were smaller than those of age-matched controls beginning at P4. In contrast, 7d of 60% O(2) had no effect on carotid body size in rats exposed to hyperoxia as adults. Bromodeoxyuridine (BrdU) and TdT-mediated dUTP nick end labeling (TUNEL) were used to assess cell proliferation and DNA fragmentation at P2, P4, and P6. Hyperoxia reduced the proportion of glomus cells undergoing cell division at P4; although a similar trend was evident at P2, hyperoxia no longer affected cell proliferation by P6. The proportion of TUNEL-positive glomus cells was modestly increased by hyperoxia. We did not detect changes in mRNA expression for proapoptotic (Bax) or antiapoptotic (Bcl-X(L)) genes or transcription factors that regulate cell cycle checkpoints (p53 or p21), although mRNA levels for cyclin B1 and cyclin B2 were reduced. Collectively, these data indicate that hyperoxia primarily attenuates postnatal growth of the carotid body by inhibiting glomus cell proliferation during the first few days of exposure.

JC virus latency in the brain and extraneural organs of patients with and without progressive multifocal leukoencephalopathy.

JC virus (JCV) is latent in the kidneys and lymphoid organs of healthy individuals, and its reactivation in the context of immunosuppression may lead to progressive multifocal leukoencephalopathy (PML). Whether JCV is present in the brains or other organs of healthy people and in immunosuppressed patients without PML has been a matter of debate. We detected JCV large T DNA by quantitative PCR of archival brain samples of 9/24 (38%) HIV-positive PML patients, 5/18 (28%) HIV-positive individuals, and 5/19 (26%) HIV-negative individuals. In the same samples, we detected JCV regulatory region DNA by nested PCR in 6/19 (32%) HIV-positive PML patients, 2/11 (18%) HIV-positive individuals, and 3/17 (18%) HIV-negative individuals. In addition, JCV DNA was detected in some spleen, lymph node, bone, and kidney samples from the same groups. In situ hybridization data confirmed the presence of JCV DNA in the brains of patients without PML. However, JCV proteins (VP1 or T antigen) were detected mainly in the brains of 23/24 HIV-positive PML patients, in only a few kidney samples of HIV-positive patients, with or without PML, and rarely in the bones of HIV-positive patients with PML. JCV proteins were not detected in the spleen or lymph nodes in any study group. Furthermore, analysis of the JCV regulatory region sequences showed both rearranged and archetype forms in brain and extraneural organs in all three study groups. Regulatory regions contained increased variations of rearrangements correlating with immunosuppression. These results provide evidence of JCV latency in the brain prior to severe immunosuppression and suggest new paradigms in JCV latency, compartmentalization, and reactivation.