Determinants of de novo B cell responses to drifted epitopes in post-vaccination SARS-CoV-2 infections

Vaccine-induced immunity may impact subsequent de novo responses to drifted epitopes in SARS-CoV-2 variants, but this has been difficult to quantify due to the challenges in recruiting unvaccinated control groups whose first exposure to SARS-CoV-2 is a primary infection. Through local, statewide, and national SARS-CoV-2 testing programs, we were able to recruit cohorts of individuals who had recovered from either primary or post-vaccination infections by either the Delta or Omicron BA.1 variants. Regardless of variant, we observed greater Spike-specific and neutralizing antibody responses in post-vaccination infections than in those who were infected without prior vaccination. Through analysis of variant-specific memory B cells as markers of de novo responses, we observed that Delta and Omicron BA.1 infections led to a marked shift in immunodominance in which some drifted epitopes elicited minimal responses, even in primary infections. Prior immunity through vaccination had a small negative impact on these de novo responses, but this did not correlate with cross-reactive memory B cells, arguing against competitive inhibition of naïve B cells. We conclude that dampened de novo B cell responses against drifted epitopes are mostly a function of altered immunodominance hierarchies that are apparent even in primary infections, with a more modest contribution from pre-existing immunity, perhaps due to accelerated antigen clearance.

Immune responses to two and three doses of the BNT162b2 mRNA vaccine in adults with solid tumors

Vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have shown high efficacy, but immunocompromised participants were excluded from controlled clinical trials. In this study, we compared immune responses to the BNT162b2 mRNA Coronavirus Disease 2019 vaccine in patients with solid tumors (n = 53) who were on active cytotoxic anti-cancer therapy to a control cohort of participants without cancer (n = 50). Neutralizing antibodies were detected in 67% of patients with cancer after the first immunization, followed by a threefold increase in median titers after the second dose. Similar patterns were observed for spike protein-specific serum antibodies and T cells, but the magnitude of each of these responses was diminished relative to the control cohort. In most patients with cancer, we detected spike receptor-binding domain and other S1-specific memory B cell subsets as potential predictors of anamnestic responses to additional immunizations. We therefore initiated a phase 1 trial for 20 cancer cohort participants of a third vaccine dose of BNT162b2 ( NCT04936997 ); primary outcomes were immune responses, with a secondary outcome of safety. At 1 week after a third immunization, 16 participants demonstrated a median threefold increase in neutralizing antibody responses, but no improvement was observed in T cell responses. Adverse events were mild. These results suggest that a third dose of BNT162b2 is safe, improves humoral immunity against SARS-CoV-2 and could be immunologically beneficial for patients with cancer on active chemotherapy.

Immune Responses to COVID-19 mRNA Vaccines in Patients with Solid Tumors on Active, Immunosuppressive Cancer Therapy

Vaccines against SARS-CoV-2 have shown high efficacy, but immunocompromised participants were excluded from controlled clinical trials. We compared immune responses to the Pfizer/BioNTech mRNA vaccine in solid tumor patients (n=53) on active cytotoxic anti-cancer therapy to a control cohort (n=50) as an observational study. Using live SARS-CoV-2 assays, neutralizing antibodies were detected in 67% and 80% of cancer patients after the first and second immunizations, respectively, with a 3-fold increase in median titers after the booster. Similar trends were observed in serum antibodies against the receptor-binding domain (RBD) and S2 regions of Spike protein, and in IFNγ+ Spike-specific T cells. Yet the magnitude of each of these responses was diminished relative to the control cohort. We therefore quantified RBD- and Spike S1-specific memory B cell subsets as predictors of anamnestic responses to additional immunizations. After the second vaccination, Spike-specific plasma cell-biased memory B cells were observed in most cancer patients at levels similar to those of the control cohort after the first immunization. We initiated an interventional phase 1 trial of a third booster shot (NCT04936997); primary outcomes were immune responses with a secondary outcome of safety. After a third immunization, the 20 participants demonstrated an increase in antibody responses, with a median 3-fold increase in virus-neutralizing titers. Yet no improvement was observed in T cell responses at 1 week after the booster immunization. There were mild adverse events, primarily injection site myalgia, with no serious adverse events after a month of follow-up. These results suggest that a third vaccination improves humoral immunity against COVID-19 in cancer patients on active chemotherapy with no severe adverse events.

Impact of Thoracic Endografting on the Hemodynamics of the Native Aorta: Pre- and Postoperative Assessments of Wall Shear Stress and Vorticity Using Computational Fluid Dynamics

PURPOSE

To quantify the hemodynamic consequences of thoracic endovascular aortic repair (TEVAR) by comparing the preoperative and postoperative wall shear stress (WSS) and vorticity profiles on computational fluid dynamics (CFD) simulations.

MATERIALS AND METHODS

The pre- and postoperative computed tomography (CT) scans from 20 consecutive patients (median age 69 years, range 20-87) treated for different thoracic aortic pathologies (11 aneurysms, 5 false aneurysms, 3 penetrating ulcers, and 1 traumatic aortic rupture) were segmented to construct patient-specific CFD models using a meshless code. The simulations were run over the cardiac cycle, and the WSS and vorticity values measured at the proximal and distal landing zones were compared.

RESULTS

The CFD runs provided 4-dimensional simulations of blood flow in all patients. WSS and vorticity profiles at the proximal landing zone (located in zones 0-3 in 15 patients) varied in 18 and 20 of the cases, respectively; WSS was increased in 11 cases and the vorticity in 9. Pre- and postoperative WSS median values were 4.19 and 4.90 Pa, respectively. Vorticity median values were 40.38 and 39.17 Hz, respectively.

CONCLUSION

TEVAR induces functional alterations in the native thoracic aorta, though the prognostic significance of these changes is still unknown. CFD appears to be a valuable tool to explore aortic hemodynamics, and its application in a larger series would help define a predictive role for these hemodynamic assessments.

Pivotal Clinical Study to Evaluate the Safety and Effectiveness of the MANTA Percutaneous Vascular Closure Device

Background:

Open surgical closure and small-bore suture-based preclosure devices have limitations when used for transcatheter aortic valve replacement, percutaneous endovascular abdominal aortic aneurysm repair, or percutaneous thoracic endovascular aortic aneurysm repair. The MANTA vascular closure device is a novel collagen-based technology designed to close large bore arteriotomies created by devices with an outer diameter ranging from 12F to 25F. In this study, we determined the safety and effectiveness of the MANTA vascular closure device.

Methods and Results:

A prospective, single arm, multicenter investigation in patients undergoing transcatheter aortic valve replacement, percutaneous endovascular abdominal aortic aneurysm repair, or thoracic endovascular aortic aneurysm repair at 20 sites in North America. The primary outcome was time to hemostasis. The primary safety outcomes were accessed site-related vascular injury or bleeding complications. A total of 341 patients, 78 roll-in, and 263 in the primary analysis cohort, were entered in the study between November 2016 and September 2017. For the primary analysis cohort, transcatheter aortic valve replacement was performed in 210 (79.8%), and percutaneous endovascular abdominal aortic aneurysm repair or thoracic endovascular aortic aneurysm repair was performed in 53 (20.2%). The 14F MANTA was used in 42 cases (16%), and the 18F was used in 221 cases(84%). The mean effective sheath outer diameter was 22F (7.3 mm). The mean time to hemostasis was 65±157 seconds with a median time to hemostasis of 24 seconds. Technical success was achieved in 257 (97.7%) patients, and a single device was deployed in 262 (99.6%) of cases. Valve Academic Research Consortium-2 major vascular complications occurred in 11 (4.2%) cases: 4 received a covered stent (1.5%), 3 had access site bleeding (1.1%), 2 underwent surgical repair (0.8%), and 2 underwent balloon inflation (0.8%).

Conclusions:

In a selected population, this study demonstrated that the MANTA percutaneous vascular closure device can safely and effectively close large bore arteriotomies created by current generation transcatheter aortic valve replacement, percutaneous endovascular abdominal aortic aneurysm repair, and thoracic endovascular aortic aneurysm repair devices.

Clinical Trial Registration:

URL: https://www.clinicaltrials.gov . Unique identifier: NCT02908880.

Plug the Hole--A Bailout Option for Acute Focal Aortic Rupture

BACKGROUND

Focal aortic rupture may result from expanding aneurysms, penetrating aortic wall ulcerations, or virulent infections. An urgent repair of paravisceral focal aortic rupture is associated with high morbidity. A staged repair approach may provide an alternative option.

CASE REPORT

A 64-year-old woman presented with acute focal rupture of the posterior paravisceral aortic wall and was progressing to hemorrhagic shock and mesenteric ischemia. Given the patient's dire condition, an endovascular approach was used to plug her focal aortic wall defect using a ventricular septal defect occluder device. Subsequently, the patient underwent resuscitation, stabilization, and operative exploration. Postoperatively, she recovered well from this staged approach.

CONCLUSIONS

This case provides an example of a staged endovascular plugging of an acute paravisceral focal aortic rupture. In select cases, this type of repair strategy is feasible, until off-the-shelf endovascular repair options become a reality.

Electromagnetic navigation for thoracic aortic stent-graft deployment: a pilot study in swine

PURPOSE

To determine the feasibility of electromagnetic tracking as a method to augment conventional imaging guidance for the safe delivery, precise positioning, and accurate deployment of thoracic aortic endografts.

MATERIALS AND METHODS

Custom guide wires were fabricated, and the delivery catheters for thoracic aortic endoprostheses were retrofitted with integrated electromagnetic coil sensors to enable real-time endovascular tracking. Preprocedure thoracic computed tomographic (CT) angiograms were obtained after the placement of fiducial skin patches on the chest wall of three anesthetized swine, enabling automatic registration. The stent-graft deployment location target near the subclavian artery was selected on the preprocedure CT angiogram. Two steps were analyzed: advancing a tracked glidewire to the aortic arch and positioning the tracked stent-graft assembly by using electromagnetic guidance alone. Multiple CT scans were obtained to evaluate the accuracy of the electromagnetic tracking system by measuring the target registration error, which compared the actual position of the tracked devices to the displayed "virtual" electromagnetic-tracked position. Postdeployment CT angiography and necropsy helped confirm stent-graft position and subclavian artery patency.

RESULTS

A stent-graft was successfully delivered and deployed in each of the three animals by using real-time electromagnetic tracking alone. The mean fiducial registration error with autoregistration was 1.5 mm. Sixteen comparative scans were obtained to determine the target registration error, which was 4.3 mm +/- 0.97 (range, 3.0-6.0 mm) for the glidewire sensor coil. The mean target registration error for the stent-graft delivery catheter sensor coil was 2.6 mm +/- 0.7 (range, 1.9-3.8 mm). The mean deployment error for the stent-graft, defined as deployment deviation from the target, was 2.6 mm +/- 3.0.

CONCLUSIONS

Delivery and deployment of customized thoracic stent-grafts with use of electromagnetic tracking alone is feasible and accurate in swine. Combining endovascular electromagnetic tracking with conventional fluoroscopy may further improve accuracy and be a more realistic multimodality approach.

Reevaluating the Need for Left Subclavian Artery Revascularization With Thoracic Endovascular Aortic Repair

BACKGROUND

With increased utilization of thoracic endovascular aortic repair (TEVAR), the anatomic limitations of proximal device landing zones are being challenged. As our experience has grown with TEVAR involving exclusion of the left subclavian artery (LSA), the need for selective revascularization of the LSA appeared to be more common than we initially anticipated. We hypothesize that for patients undergoing TEVAR requiring coverage of the LSA, the need for LSA revascularization is higher than reported in the literature.

METHODS

The charts of all patients undergoing TEVAR performed at a single tertiary care center from 1999 to 2006 were reviewed. The review included the preoperative radiographic evaluations, the assessment of comorbidities, the anatomic position of the proximal and distal landing zones, outcomes, complications, and the need for preoperative or postoperative subclavian artery revascularization.

RESULTS

Sixty-four patients underwent TEVAR and 27 (42%) of these patients required exclusion of the LSA from the thoracic aorta. Seven of these 27 patients (25.9%) required preoperative LSA revascularization. Four patients developed late symptoms, necessitating LSA revascularization. No patients died or developed paraplegia, but three adverse neurological events occurred unrelated to the posterior fossa circulation. No patient developed any left arm disability.

CONCLUSIONS

The TEVAR coverage of the LSA with selective revascularization was safe for patients, but greater than 11 of 27 (40.7%) required either preoperative or postoperative LSA revascularization. Although this study represents our early experience with TEVAR, these data suggest that selective revascularization after TEVAR exclusion of the origin of the LSA may be required more frequently than previously reported.

Standardized evaluation and reporting of stent fractures in clinical trials of noncoronary devices

OBJECTIVES

Define the prospective surveillance and reporting parameters for assessment of metallic stents used in clinical trials of superficial femoral artery atherosclerosis.

BACKGROUND

While advances in medical therapies to improve atherosclerotic risk factor profiles in patients with peripheral arterial disease have focused on prevention of disease progression, the development of endovascular devices is altering the therapeutic algorithm for patients with peripheral arterial disease. Stents have emerged as one of the advances that may promote durable patency, particularly in the infrainguinal arteries.

METHODS

The Zilver-PTX is a prospective multicenter randomized trial of bare metal versus drug-eluting nitinol stents for superficial femoral artery peripheral arterial disease. A predefined surveillance program is mandated in this trial. During the genesis of this program, it became clear that no single standard has existed to identify, classify, and report fractures of metallic stents placed in peripheral arteries.

RESULTS

This report defines the key components of prospective stent fracture surveillance, including location of radiographic images obtained, types of radiographic equipment, methods of limb, and image intensifier positioning, intervals required for imaging, grading schemes for reporting, and methods of analyzing the images.

CONCLUSIONS

As the proliferation of minimally invasive revascularization strategies continues, the stability of metallic endoprostheses is increasingly critical. Uniform surveillance of these devices for fracture and disarticulation is important in order to compare the relative merits of various stent-based devices in clinical trials.

Successful transduction of liver in hemophilia by AAV-Factor IX and limitations imposed by the host immune response

We have previously shown that a single portal vein infusion of a recombinant adeno-associated viral vector (rAAV) expressing canine Factor IX (F.IX) resulted in long-term expression of therapeutic levels of F.IX in dogs with severe hemophilia B. We carried out a phase 1/2 dose-escalation clinical study to extend this approach to humans with severe hemophilia B. rAAV-2 vector expressing human F.IX was infused through the hepatic artery into seven subjects. The data show that: (i) vector infusion at doses up to 2 x 10(12) vg/kg was not associated with acute or long-lasting toxicity; (ii) therapeutic levels of F.IX were achieved at the highest dose tested; (iii) duration of expression at therapeutic levels was limited to a period of approximately 8 weeks; (iv) a gradual decline in F.IX was accompanied by a transient asymptomatic elevation of liver transaminases that resolved without treatment. Further studies suggested that destruction of transduced hepatocytes by cell-mediated immunity targeting antigens of the AAV capsid caused both the decline in F.IX and the transient transaminitis. We conclude that rAAV-2 vectors can transduce human hepatocytes in vivo to result in therapeutically relevant levels of F.IX, but that future studies in humans may require immunomodulation to achieve long-term expression.

Lack of germline transmission of vector sequences following systemic administration of recombinant AAV-2 vector in males

A potential consequence of systemic administration of viral vectors is the inadvertent introduction of foreign DNA into recipient germ cells. To evaluate the safety of in vivo recombinant adeno-associated virus (rAAV) mediated gene transfer approaches for hemophilia B, we explored the risk of germline transmission of vector sequences following intramuscular (IM) injection of rAAV in four species of male animals (mouse, rat, rabbit and dog). In vector biodistribution studies in mice and rats, there is a dose-dependent increase in the likelihood that vector sequences can be detected in gonadal DNA using a sensitive PCR technique. However, in dogs DNA extracted from semen is negative for vector sequences. To address this discrepancy, studies were done in rabbits, and both semen and testicular DNAs were analyzed for the presence of vector sequences. These studies showed that no AAV vector sequences were detected in DNA extracted from rabbit semen samples collected at time points ranging from 7 to 90 days following IM injection of 1 x 10(13) vector genomes rAAV (vg) per kg. In contrast, DNA extracted from gonadal tissue was positive for vector sequences, but the positive signals diminished in number and strength with time. By FISH analysis, AAV signals were localized to the testis basement membrane and the interstitial space; no intracellular signal was observed. We observed similar findings following hepatic artery administration of rAAV in rats and dogs, suggesting that our findings are independent of the route of administration of vector. Attempts to transduce isolated murine spermatogonia directly with AAV-lacZ were unsuccessful. In clinical studies human subjects injected IM with an AAV vector at doses up to 2 x 10(12) vg/kg have shown no evidence of vector sequences in semen. Together, these studies suggest that rAAV introduced into skeletal muscle or the hepatic artery does not transduce male germ cells efficiently. We conclude that the risk of inadvertent germline transmission of vector sequences following IM or hepatic artery injection of AAV-2 vectors is extremely low.

Vertebral artery stenting following percutaneous transluminal angioplasty. Technical note

The authors report initial results and follow up using stent placement to treat atherosclerotic stenosis in vertebral arteries. Three patients with severe atherosclerotic vascular disease underwent vertebral artery stent placement using a balloon expandable stent. Medical therapy (aspirin and warfarin) and conventional percutaneous angioplasty failed to resolve the disease and the patients developed symptomatic restenosis within 3 months of angioplasty. Two patients had symptoms of anterior circulation ischemia with carotid artery occlusions and reduced supply to the anterior circulation from the stenosed vertebral arteries. One patient had recurrent posterior circulation symptoms. Stents were successfully placed in all three, resulting in immediate reversal of stenosis and resolution of symptoms. Clinical follow-up study (mean 9 months) has shown no recurrent symptoms in the patient with posterior circulation symptoms, but the two patients with anterior circulation ischemia did develop recurrent symptoms. Angiographic follow up in these two patients at 3 months and 1 year, however, demonstrated continued patency of vertebral artery lumina. They underwent extracranial-intracranial bypass surgery to relieve their symptoms. This experience suggests stents can be placed without complication in the proximal vertebral arteries and may have an adjunctive role in the treatment of atherosclerotic cerebrovascular disease following unsuccessful angioplasty.

Transjugular intrahepatic portosystemic shunts

Management of bleeding esophageal varices due to portal hypertension has traditionally relied on endoscopic sclerotherapy and operative intervention with placement of a portosystemic shunt. Although percutaneous decompression of portal hypertension was investigated 25 years ago, it was not clinically feasible until recently. With the advent of intravascular stents, the technique of creating a transjugular intrahepatic portosystemic shunt (TIPS) can now be effectively applied to treat the complications of portal hypertension, including variceal hemorrhage and refractory ascites. Since its introduction in 1989, TIPS has enjoyed widespread clinical application. The initial results with this procedure are encouraging and suggest that it is an effective means of reducing the frequency of variceal hemorrhage in patients with portal hypertension. The long-term patency rate and frequency of complications, however, have not been clearly defined. Similarly, the role of TIPS in the treatment of refractory ascites, Budd-Chiari syndrome, and hepatorenal syndrome remains unclear because sufficient data do not yet exist to support its general use in these settings.

Balloon expandable stents to treat central venous stenoses in hemodialysis patients

Vascular access failure in hemodialysis patients remains a significant problem. The use of thrombolytic agents and balloon angioplasty instead of or in conjunction with surgical revision, has been helpful in increasing the life span of vascular access in these patients. The application of newer endovascular therapies, such as vascular stents, may further improve the salvage rate of hemodialysis access sites. These stents may be particularly valuable in treating stenoses in large central veins. We present 2 cases in which a balloon-expandable Palmaz stent was used to treat a central venous stenosis causing signs of vascular access failure.