Passive immune therapies: another tool against COVID-19

Passive immune therapy consists of several different therapies, convalescent plasma, hyperimmune globulin, and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) neutralizing monoclonal antibodies. Although these treatments were not part of any pandemic planning prior to coronavirus disease 2019 (COVID-19), due to the absence of high-quality evidence demonstrating benefit in other severe respiratory infections, a large amount of research has now been performed to demonstrate their benefit or lack of benefit in different patient groups. This review summarizes the evidence up to July 2021 on their use and also when they should not be used or when additional data are required. Vaccination against SARS-CoV-2 is the most important method of preventing severe and fatal COVID-19 in people who have an intact immune system. Passive immune therapy should only be considered for patients at high risk of severe or fatal COVID-19. The only therapy that has received full regulatory approval is the casirivimab/imdevimab monoclonal cocktail; all other treatments are being used under emergency use authorizations. In Japan, it has been licensed to treat patients with mild to moderate COVID-19, and in the United Kingdom, it has also been licensed to prevent infection.

CMV-Related Gastric Ulcer and Gastroduodenitis in an Immunocompetent Patient: A Case Report and Literature Review

Background. Cytomegalovirus (CMV)- related gastroduodenal infection is rare in immunocompetent hosts, and although it is considered a self-limiting condition in most cases, there is scarce literature to assert its management. Case Presentation. We report a case of a 66-year-old immunocompetent male patient diagnosed with a giant gastric ulcer caused by CMV infection. The ulcer manifested as refractory vomiting and melena. Rapid and full resolution was observed on proton-pump inhibitor (PPI) monotherapy. Conclusion. Gastric CMV infection might mimic an advanced gastric tumor in individuals with an intact immune system. The condition is rare, and the diagnosis is challenging and oftentimes overlooked. However, a rapid resolution has been documented in all cases, even without antiviral therapy.

Effectiveness of the BNT162b2mRNA Covid-19 Vaccine in Patients with Hematological Neoplasms

Evidence regarding the effectiveness of covid-19 vaccine in patients with impaired immunity, is limited. Initial observations suggest a lower humoral response in these patients. We evaluated the relative effectiveness of the mRNA BNT162b2 vaccine in patients with hematological neoplasms compared to matched controls. Data on patients with hematological neoplasms after two vaccine doses were extracted and matched 1:1 with vaccinated controls. Subpopulation analyses focused on patients receiving therapy for the hematological neoplasm, patients without treatment who are only followed, and recipients of specific treatments. The analysis focused on covid-19 outcomes from day 7 through 43 following the second vaccine dose: Documented covid-19 infection by PCR; Symptomatic infection; Hospitalizations; Severe covid-19 disease and covid-19-related death. Of a population of 4.7 million insured people, 32,516 patients with hematological neoplasms were identified, of whom 5,017 were receiving therapy for an active disease. Vaccinated patients with hematological neoplasms, compared with vaccinated matched controls, had an increased risk of documented infections (RR 1.60, 95% confidence interval [CI] 1.12-2.37), symptomatic covid-19 (RR 1.72, 95% CI 1.05-2.85), covid-19 related hospitalizations (RR 3.13, 95% CI 1.68-7.08), severe covid-19 (RR 2.27, 95% CI 1.18-5.19) and covid-19 related death (RR 1.66, 95% CI 0.72-4.47). Limiting the analysis to patients on hematological treatments showed a higher increased risk. This analysis shows that vaccinated patients with hematological neoplasms, in particular patients on treatment, suffer from covid-19 outcomes more than vaccinated individuals with intact immune system. Ways to enhance covid-19 immunity in this patient population, such as additional doses, should be explored.

Efficient methods for generation and expansion of, and gene delivery to Rhesus Macaque plasma B cells

Engineered long lived plasma cells have the potential to be a new area of cell therapy. A key step in developing this cell therapy is testing in a model with an intact immune system similar to humans. To that end, we have developed methods to purify, expand, and differentiate non-human primate (NHP; rhesus macaque) B cells ex vivo. By comparing several media types and conditions, we consistently achieved 10-fold expansion of NHP B cells using a readily available commercial supplement. After only seven days in culture, large percentages of cells in NHP B cell cultures were differentiated. These cells expressed surface markers found in human antibody secreting cells (CD38 and CD138) and secreted immunoglobulin G. We also identified the serotypes (2.5 and D-J) and conditions necessary for efficient transduction of NHP B cells with AAV vectors for the purposes of producing a secreted protein (BAFF). We hope that this work will accelerate proof-of-concept in vivo studies using engineered protein-secreting B cells in an NHP model.

Germinal center–dependent and –independent memory B cells produced throughout the immune response

Memory B cells comprise a heterogenous group of cells that differ in origin and phenotype. During the early phases of the immune response, activated B cells can differentiate into IgM-expressing memory cells, short-lived plasma cells, or seed germinal centers (GCs). The memory compartment is subsequently enriched by B cells that have been through several rounds of division and selection in the GC. Here, we report on the use of an unbiased lineage-tracking approach to explore the origins and properties of memory B cell subsets in mice with an intact immune system. We find that activated B cells continue to differentiate into memory B cells throughout the immune response. When defined on the basis of their origins, the memory B cells originating from activated B cells or GCs differ in isotype and overall gene expression, somatic hypermutation, and their affinity for antigen.

Rare Etiology of Odynophagia in a Female Adolescent

Herpes esophagitis (HE) is a rare condition in immunocompetent adolescents. However, it commonly occurs as a primary infection in younger individuals. Herein, we report a 16-year-old female patient who had a history of fever for 5 days, odynophagia, and orolabial herpes infection for 7 days. Clusters of painful vesicles on an erythematous base on the lips, gingiva, and palate were observed on physical examination. Further, esophagogastroduodenoscopy revealed diffuse linear ulcerations in the distal esophagus. The patient then received the following treatment: intravenous (I.V.) acyclovir 5 mg/kg three times a day, I.V. omeprazole 40 mg two times a day, and acyclovir 5% cream four times a day. After 8 days of admission, the patient was discharged. A follow-up esophagogastroduodenoscopy was performed 7 weeks after discharge, and the results revealed that the esophageal mucosa had a normal appearance. The effect of antiviral treatment against HE remains unknown in these patients. Nevertheless, it is believed to accelerate the healing process in individuals with esophageal mucosal barrier damage. To the best of our knowledge, this case of a female adolescent with an intact immune system is the sixth case of herpes simplex esophagitis to be reported in the literature.

Human Cytomegalovirus UL7, miR-US5-1, and miR-UL112-3p Inactivation of FOXO3a Protects CD34+ Hematopoietic Progenitor Cells from Apoptosis

ABSTRACT Human cytomegalovirus (HCMV) infection of myeloid lineage cells, such as CD34+ hematopoietic progenitor cells (HPCs) or monocytes, results in the upregulation of antiapoptotic cellular proteins that protect the newly infected cells from programmed cell death. The mechanisms used by HCMV to regulate proapoptotic cellular proteins upon infection of CD34+ HPCs have not been fully explored. Here, we show that HCMV utilizes pUL7, a secreted protein that signals through the FLT3 receptor, and miR-US5-1 and miR-UL112-3p to reduce the abundance and activity of the proapoptotic transcription factor FOXO3a at early times after infection of CD34+ HPCs. Regulation of FOXO3a by pUL7, miR-US5-1, and miR-UL112 results in reduced expression of the proapoptotic BCL2L11 transcript and protection of CD34+ HPCs from virus-induced apoptosis. These data highlight the importance of both viral proteins and microRNAs (miRNAs) in protecting CD34+ HPCs from apoptosis at early times postinfection, allowing for the establishment of latency and maintenance of viral genome-containing cells. IMPORTANCE Human cytomegalovirus (HCMV) causes serious disease in immunocompromised individuals and is a significant problem during transplantation. The virus can establish a latent infection in CD34+ hematopoietic progenitor cells (HPCs) and periodically reactivate to cause disease in the absence of an intact immune system. What viral gene products are required for successful establishment of latency is still not fully understood. Here, we show that both a viral protein and viral miRNAs are required to prevent apoptosis after infection of CD34+ HPCs. HCMV pUL7 and miRNAs miR-US5-1 and miR-UL112-3p act to limit the expression and activation of the transcription factor FOXO3a, which in turn reduces expression of proapoptotic gene BCL2L11 and prevents virus-induced apoptosis in CD34+ HPCs.

IMG-12. CHARACTERISATION OF MODELS OF H3F3A_G34R/V MUTANT PAEDIATRIC GLIOBLASTOMA IN VIVO USING MAGNETIC RESONANCE IMAGING

Approximately 15% of paediatric/young adult cerebral hemispheric glioblastomas (pGBM) harbour G34R/V mutations in H3F3A, encoding the histone H3.3 variant. Development of novel therapeutic interventions demands models that accurately recapitulate this subset of disease and sensitive imaging methods with which to study tumours in situ. Three H3F3A_G34R primary-patient-derived cultures, alongside established cell-line KNS42 (H3F3A_G34V), were implanted orthotopically in immunocompromised mice. KNS42 (TP53_R342*) tumours were clearly detectable using T2-weighted (T2w)-MRI, enhanced following contrast agent administration, indicating impaired blood-brain barrier (BBB) integrity, and demonstrated minimal invasion. OPBG_GBM_001 cells (TP53_89-90X,ATRX_II2133-2144X) formed infiltrative tumours that were hyperintense on T2w-MRI and demonstrated contrast-enhancement suggestive of heterogeneous BBB integrity. HSJD_GBM_002 cells (TP53_P278T,ATRX_R666*) spread diffusely throughout the brain with their full extent typically not discernible by T2w-MRI, the BBB also remaining intact. No evidence of CHOP_GBM_001 tumour was detected by MRI 11months post-implantation. Immunocompetent syngeneic models using tumour cells induced by mutations modelling hemispheric pGBM (NRAS/shP53/shATRX±H3.3G34R) are being explored. Fast growing heterogeneous lesions with variable contrast-enhancement were identified; the H3.3G34R mutation conferred longer median survival (2 clones:25/28days, control:14days). These models have the advantage of an intact immune system and short latency for initial efficacy studies. Primary pGBM cells yield tumours that are more representative of the spectrum of clinical disease; variable hyperintensity on T2w-MRI corresponding to cellular density, with diffusely infiltrative disease less clearly definable, a paucity of oedema and a range of contrast-enhancement. Pathological features including giant multinucleated cells, and mitotic figures were also evident.

A Murine Immunocompetent Acute Myeloid Leukemia (AML) Model for Testing Immunotherapies

Background With the emergence of immunotherapies as a promising cancer treatment, there is now a pressing need for pre-clinical animal models to test immunotherapy strategies for acute myeloid leukemia (AML). While murine xenotransplant models generated by transplanting human AML cells are frequently used to model AML, they require immune-deficient mice. Syngeneic murine bone marrow transplant leukemia models (MBMTLM), which are established in immune competent mice, usually require radiation of the recipient mouse before leukemic cells are transplanted. This radiation suppresses the immune system and makes it difficult to study how the immune system responds to leukemia cells. Aim Our aim was to establish immunocompetent MBMTLMs to understand how the immune system responds to leukemia cells expressing a highly immunogenic antigen. Method We first established MBMTLMs models driven by the CALM/AF10 or MLL/AF9 fusion genes. Then leukemia cells were transduced with a SIINFEKL expressing retrovirus (MSCV-DsRed-SIINFEKL). SIINFEKL is a highly immunogenic eight amino acid peptide from ovalbumin. Results The transduction efficiency of MSCV-DsRed-SIINFEKL was about 12.9% on leukemic cells of MLL/AF9 and 13% on CALM/AF10 cells. All primary MLL/AF9-SIINFEKL (n=3) developed leukemia with a latency of 22 days. SIINFEKL expression was detected on 75.5±3% of the spleen cells of these mice. These spleen cells were transplanted into irradiated (n=6) and non-irradiated (n=8) mice to establish secondary MLL/AF9-SIINFEKL leukemias (Table 1). In the irradiated recipients, five out of six mice developed leukemia within 22-29 days. In non-irradiated recipients, four out of eight developed leukemia with a latency of 29-45 days. Flow cytometry showed that SIINFEKL was expressed on 82.28±6% of the spleen cells in irradiated recipients. In contrast, fewer than 1% of the spleen cells in non-irradiated mice with secondary MLL/AF9-SIINFEKL leukemia expressed SIINFEKL. Similar experiments were performed with the CALM/AF10 model. All primary CALM/AF10-SIINFEKL transplanted mice (n=2) developed leukemia with a latency of 32 and 42 days and showed SIINFEKL positivity on 99% of the leukemia cells. Secondary CALM/AF10-SIINFEKL leukemias were generated by transplanting these AML cells into irradiated (n=6) and non-irradiated (n=8) mice. All six irradiated recipients developed leukemia within 21-40 days. However, only five of the eight non-irradiated recipients developed leukemia with a latency of 35-42 days. Strikingly, about 99% of the AML cells in the irradiated mice were SIINFEKL positive but fewer than 1% of the AML cells in the five non-irradiated mice who developed leukemia were SIINFEKL positive. Discussion We find that for both MLL/AF9 and CALM/AF10 AML an intact immune system (non-irradiated recipients) is able to largely eliminate AML cells which express the SIINFEKL antigen, even when challenged with a large number of AML cells. In the non-irradiated recipients only 50 to 60% developed leukemia, and the leukemias that did develop had hardly any SIINFEKL-positive cells. In contrast, nearly all irradiated mice (11 of 12) developed leukemia with a high percentage of SIINFEKL expressing AML cells. SIINFEKL was presented on the surface of leukemic cells by the murine MHC class I H-2Kb molecule. Our results differ slightly from research reported by Hasegawa et al. 2015, who showed that MLL/AF9 AML cells expressing ovalbumin caused leukemia after transplantation into non-irradiated mice. However, they did not investigate whether ovalbumin was still being expressed on the leukemia cells. Conclusion We have established syngeneic murine AML models in immunocompetent mice and have evidence that an intact immune system has the ability to suppress or even eliminate rapidly proliferating AML cells if they express a strong antigen. These models should be useful for developing immunotherapy strategies for AML. Disclosures Desai: University of Auckland: Current Employment. Kakadia:University of Auckland: Current Employment. Browett:University of Auckland: Current Employment; BeiGene: Research Funding; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: TRAVEL, ACCOMMODATIONS, EXPENSES (paid by any for-profit health care company), Research Funding; Shire: Research Funding; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees. Bohlander:University of Auckland: Current Employment; Family of Marijana Kumerich: Research Funding; Leukaemia and Blood Cancer New Zealand: Research Funding.

JCPyV VP1 Mutations in Progressive Multifocal Leukoencephalopathy: Altering Tropism or Mediating Immune Evasion?

Polyomaviruses are ubiquitous human pathogens that cause lifelong, asymptomatic infections in healthy individuals. Although these viruses are restrained by an intact immune system, immunocompromised individuals are at risk for developing severe diseases driven by resurgent viral replication. In particular, loss of immune control over JC polyomavirus can lead to the development of the demyelinating brain disease progressive multifocal leukoencephalopathy (PML). Viral isolates from PML patients frequently carry point mutations in the major capsid protein, VP1, which mediates virion binding to cellular glycan receptors. Because polyomaviruses are non-enveloped, VP1 is also the target of the host’s neutralizing antibody response. Thus, VP1 mutations could affect tropism and/or recognition by polyomavirus-specific antibodies. How these mutations predispose susceptible individuals to PML and other JCPyV-associated CNS diseases remains to be fully elucidated. Here, we review the current understanding of polyomavirus capsid mutations and their effects on viral tropism, immune evasion, and virulence.