In vivo antiviral efficacy of LCTG-002, a pooled, purified human milk secretory IgA product, against SARS-CoV-2 in a murine model of COVID-19

Immunoglobulin A (IgA) is the most abundant antibody (Ab) in human mucosae, with secretory form (sIgA) being dominant and uniquely stable. sIgA is challenging to produce recombinantly but is naturally found in human milk, which could be considered a global resource for this biologic, justifying its development as a mucosal therapeutic. Presently, SARS-CoV-2 was utilized as a model mucosal pathogen, and methods were developed to efficiently extract human milk sIgA from donors who were naïve to SARS-CoV-2 or had recovered from infection that elicited high-titer anti-SARS-CoV-2 Spike sIgA in their milk (pooled to make LCTG-002). Mass spectrometry determined that proteins with a relative abundance of 1% or greater were all associated with sIgA. Western blot demonstrated that all batches consisted predominantly of sIgA. Compared to control IgA, LCTG-002 demonstrated significantly higher Spike binding (mean endpoint of 0.87 versus 5.87). LCTG-002 was capable of blocking the Spike receptor-binding domain - angiotensin-converting enzyme 2 (ACE2) interaction with significantly greater potency compared to control (mean LCTG-002 IC50 154ug/mL versus 50% inhibition not achieved for control), and exhibited significant neutralization activity against Spike-pseudotyped virus infection (mean LCTG-002 IC50 49.8ug/mL versus 114.5ug/mL for control). LCTG-002 was tested for its capacity to reduce viral lung burden in K18+hACE2 transgenic mice inoculated with SARS-CoV-2. LCTG-002 significantly reduced SARS-CoV-2 titers compared to control when administered at 0.25 mg/day or 1 mg/day, with a maximum TCID50 reduction of 4.9 logs. This innovative study demonstrates that LCTG-002 is highly pure and efficacious in vivo, supporting further development of milk-derived, polyclonal sIgA therapeutics.

In Vivo Antiviral Efficacy of LCTG-002, a Pooled, Purified Human Milk Secretory IgA product, Against SARS-CoV-2 in a Murine Model of COVID-19

Immunoglobulin A (IgA) is the most abundant antibody (Ab) in human mucosal compartments including the respiratory tract, with the secretory form of IgA (sIgA) being dominant and uniquely stable in these environments. sIgA is naturally found in human milk, which could be considered a global resource for this biologic, justifying the development of human milk sIgA as a dedicated airway therapeutic for respiratory infections such as SARS-CoV-2. In the present study, methods were therefore developed to efficiently extract human milk sIgA from donors who were either immunologically naïve to SARS-CoV-2 (pooled as a control IgA) or had recovered from a PCR-confirmed SARS-CoV-2 infection that elicited high-titer anti-SARS-CoV-2 Spike sIgA Abs in their milk (pooled together to make LCTG-002). Mass spectrometry determined that proteins with a relative abundance of 1.0% or greater were all associated with sIgA. None of the proteins exhibited statistically significant differences between batches. Western blot demonstrated all batches consisted predominantly of sIgA. Compared to control IgA, LCTG-002 demonstrated significantly higher binding to Spike, and was also capable of blocking the Spike - ACE2 interaction in vitro with 6.3x greater potency compared to control IgA (58% inhibition at ∼240ug/mL). LCTG-002 was then tested in vivo for its capacity to reduce viral burden in the lungs of K18+hACE2 transgenic mice inoculated with SARS-CoV-2. LCTG-002 was demonstrated to significantly reduce SARS-CoV-2 titers in the lungs compared to control IgA when administered at either 250ug/day or 1 mg/day, as measured by TCID50, plaque forming units (PFU), and qRT-PCR, with a maximum reduction of 4.9 logs. This innovative study demonstrates that LCTG-002 is highly pure, efficacious, and well tolerated in vivo, supporting further development of milk-derived, polyclonal sIgA therapeutics against SARS-CoV-2 and other mucosal infections.

[A "fast track" to improve management of neovascular age related macular degeneration]

OBJECTIVE

To evaluate the role of a fast track for management of patients with neovascular age- related macular degeneration (nARMD) treated by intravitreal injection of anti-VEGF.

PATIENTS

The records of 100 patients in the chronic maintenance phase of intravitreal anti-VEGF followed in the fast track and 63 patients followed in the standard protocol for at least 12 months were retrospectively analyzed.

METHOD

Patients in the fast track underwent visual acuity (VA) testing by ETDRS, optical coherence tomography (OCT) and a physician assessment. The injection was performed the same day whenever possible. The primary endpoint to evaluate patient adherence was the time between the ideal date of visit or injection prescribed by the physician and the actual date of administration.

RESULTS

The mean time between the ideal date of visit or injection prescribed by the physician and the actual date of administration was 4.1±7.5 days for the patients followed in the fast track and 5.6±18.7 days for the patients followed in the standard protocol. Mean VA remained stable for the patients followed in the fast track: 20/50 (20/800 to 20/20) at baseline vs. 20/50 (20/800 to 20/16) at the conclusion of follow-up. It dropped from 40/50 at baseline to 20/63 at the conclusion of follow-up for the patients followed in the standard protocol.

CONCLUSION

In the context of a fast track, it was possible to improve the adherence of nARMD patients and maintain their VA gain or stabilization achieved after the induction phase.

Biodistribution and endocytosis of ICAM-1-targeting antibodies versus nanocarriers in the gastrointestinal tract in mice

Drug delivery to the gastrointestinal (GI) tract is key for improving treatment of GI maladies, developing oral vaccines, and facilitating drug transport into circulation. However, delivery of formulations to the GI tract is hindered by pH changes, degradative enzymes, mucus, and peristalsis, leading to poor GI retention. Targeting may prolong residence of therapeutics in the GI tract and enhance their interaction with this tissue, improving such aspects. We evaluated nanocarrier (NC) and ligand-mediated targeting in the GI tract following gastric gavage in mice. We compared GI biodistribution, degradation, and endocytosis between control antibodies and antibodies targeting the cell surface determinant intercellular adhesion molecule 1 (ICAM-1), expressed on GI epithelium and other cell types. These antibodies were administered either as free entities or coated onto polymer NCs. Fluorescence and radioisotope tracing showed proximal accumulation, with preferential retention in the stomach, jejunum, and ileum; and minimal presence in the duodenum, cecum, and colon by 1 hour after administration. Upstream (gastric) retention was enhanced in NC formulations, with decreased downstream (jejunal) accumulation. Of the total dose delivered to the GI tract, ∼60% was susceptible to enzymatic (but not pH-mediated) degradation, verified both in vitro and in vivo. Attenuation of peristalsis by sedation increased upstream retention (stomach, duodenum, and jejunum). Conversely, alkaline NaHCO(3), which enhances GI transit by decreasing mucosal viscosity, favored downstream (ileal) passage. This suggests passive transit through the GI tract, governed by mucoadhesion and peristalsis. In contrast, both free anti-ICAM and anti-ICAM NCs demonstrated significantly enhanced upstream (stomach and duodenum) retention when compared to control IgG counterparts, suggesting GI targeting. This was validated by transmission electron microscopy and energy dispersive X-ray spectroscopy, which revealed anti-ICAM NCs in vesicular compartments within duodenal epithelial cells. These results will guide future work aimed at improving intraoral delivery of targeted therapeutics for the treatment of GI pathologies.

An attenuated innate immune response to a clinical strain of respiratory syncytial virus (RSV) in human monocyte derived dendritic cells (MDDC) (37.43)

RSV clinical strain 19 was isolated from a severely affected infant and was characterized in a model in which mice develop severe disease defined by enhanced mucous secretion, IL-13 expression, and low expression of IFN-α compared to infection with the lab strain A2. We compared the innate response induced by RSV strain 19 with strain A2 in human MDDC using a qRT-PCR based array and a novel qRT-PCR assay we developed that discriminates among all IFN-α and IFN-λ subtypes and also includes IFN-β. Human MDDC expressed a similar profile of inflammatory and IFN response genes (IRG) to both RSV strains. The response to strain 19, however, was attenuated for many IRG and inflammatory genes, including CXCL9, CXCL10, CCL2 and genes associated with the RIG-I pathway. Similarly, MDDC expressed IFN-α1, IFN-β, IFN-λ1, and -λ2 in response to either strain, but strain 19 expressed lower levels of each. Another IFN subtype, IFN-α14, was expressed by 5 donors in response to strain A2 but was undetectable in response to strain 19. IFN-α protein, however, was undetectable in 9 of 10 supernatants from strain 19 in contrast to 1 of 10 supernatants from A2 infected cells. Evasion or active suppression of the IFN-α, -β or -λ response may explain the enhanced pathogenicity of strain 19. The qualitative difference in IFN-α14 expression in response to A2 but not 19 suggests a potentially important role for this subtype.

Expression patterns of Human Interferon-alpha and Interferon-lambda subtypes by monocytes, dendritic cells and B cells. (136.14)

Human interferon-alpha comprises a family of thirteen highly homologous genes and twelve subtypes (coding sequences of IFN-alpha1 and -13 are identical). We employed two modifications of fluorescent-labeled probe technology--molecular beacons (MB) and locked-nucleic acids (LNA) to develop a highly efficient, sensitive, and specific quantitative RT-PCR assay for each human IFN-alpha subtype as well as the three subtypes of IFN-lambda, and for completion, IFN-beta and -gamma. The assay is formatted to a 384-well plate that measures 16 samples/plate and includes four-point standards for each IFN. Using this assay, we determined expression patterns of these IFN by monocytes, monocyte-derived macrophages and dendritic cells (MDM and MDDC), primary mDC, pDC and B cells in response to ligands for TLR 3, 4, and 9. All the myeloid cells, including mDC expressed high levels of IFN-beta and -lambda1, and moderate levels of IFN-alpha. pDC expressed high levels of almost all IFN, although with quantitative and in one case, a qualitative difference in between the response to CpG (TLR9) vs. imiquod (TLR7). B cells also expressed IFN—more subtypes than myeloid cells, but and fewer than pDC. Type I IFN expression was always accompanied by type III IFN expression. We conclude that IFN expression patterns are both ligand and cell-type specific. Subtypes alone or in combination may have unique roles in the innate immune response.

Phenotypic correction of ornithine transcarbamylase deficiency using low dose helper-dependent adenoviral vectors

BACKGROUND

Helper-dependent adenoviral vectors (HDAd) can mediate long-term phenotypic correction in the ornithine transacarbamylase (OTC)-deficient mice model with negligible chronic toxicity. However, the high doses required for metabolic correction will result in systemic inflammatory response syndrome in humans. This acute toxicity represents the major obstacle for clinical applications of HDAd vectors for the treatment of OTC deficiency. Strategies for reducing the dose necessary for disease correction are highly desirable because HDAd acute toxicity is clearly dose-dependent.

METHODS

We analysed a potent expression cassette and the hydrodynamic injection for the ability to reduce the HDAd dose necessary for phenotypic correction in OTC-deficient spf-ash mice.

RESULTS

We have developed a vector containing a potent expression cassette expressing the OTC transgene, which allowed phenotypic correction at lower doses. Our results suggest that vector expressing greater OTC levels allows correction of orotic acid overproduction at lower doses that make clinical translation more relevant. We were able to further reduce the minimal effective dose by delivering the vector through the hydrodynamic injection technique.

CONCLUSIONS

Vectors containing the expression cassette used in the present study, combined with other strategies for improving HDAd therapeutic index, will likely permit application of these vectors for the treatment of OTC deficiency as well as other urea cycle disorders.

Antigen-specific tolerance of human alpha1-antitrypsin induced by helper-dependent adenovirus

As efficient and less toxic virus-derived gene therapy vectors are developed, a pressing problem is to avoid immune response to the therapeutic gene product. Secreted therapeutic proteins potentially represent a special problem, as they are readily available to professional antigen-presenting cells throughout the body. Some studies suggest that immunity to serum proteins can be avoided in some mouse strains by using tissue-specific promoters. Here we show that expression of human alpha1-antitrypsin (AAT) was nonimmunogenic in the immune-responsive strain C3H/HeJ, when expressed from helper-dependent (HD) vectors using ubiquitous as well as tissue-specific promoters. Coadministration of less immunogenic HD vectors with an immunogenic first-generation vector failed to immunize, suggesting immune suppression rather than immune stealth. Indeed, mice primed with HD vectors were tolerant to immune challenge with hAAT emulsified in complete Freund's adjuvant. Such animals developed high-titer antibodies to coemulsified human serum albumin, showing that tolerance was antigen specific. AAT-specific T cell responses were depressed in tolerized animals, suggesting that tolerance affects both T and B cells. These results are consistent with models of high-dose tolerance of B cells and certain other suppressive mechanisms, and suggest that a high level of expression from HD vectors can be sufficient to induce specific immune tolerance to serum proteins.

Correction of murine hemophilia A and immunological differences of factor VIII variants delivered by helper-dependent adenoviral vectors

Bioengineering of the factor VIII (FVIII) molecule has led to the production of variants that overcome poor secretion and/or rapid inactivation. We tested six modified FVIII variants for in vivo efficacy by expressing them from helper-dependent adenoviral (HD-Ad) vectors. We constructed a wild-type (WT) variant, a B-domain-deleted (BDD) variant, a point mutant for improved secretion (F309S), a variant with a partial B-domain deletion for improved secretion (N6), a combination of the point mutant and partial BDD variant (F309N6), and an inactivation-resistant (IR8) FVIII variant. All the constructs expressed functional protein after injection of high-dose HD-Ad. Activity ranged from 20 to 50% with WT, to approximately 100% with the N6 and F309N6 variants. Interestingly, mice treated with N6 showed long-term FVIII activity and phenotypic correction for up to 74 weeks, with low anti-FVIII antibody titer. Importantly, the N6 variant was therapeutically efficacious even after a 50% reduction of viral dose, thereby indicating that transgene modification itself can improve the dose efficacy of HD-Ad. This finding is significant, because dose efficacy is a key factor in clinical application. In summary, bioengineering of the FVIII molecule may be an effective approach to improving the safety, immunogenicity, and efficacy of HD-Ad gene therapy in hemophilia A (HA).

Toll-like Receptor 9 Triggers an Innate Immune Response to Helper-dependent Adenoviral Vectors

A major obstacle to the clinical application of systemic adenoviral gene replacement therapy is the host innate immune response. Although recent studies have attempted to characterize the cellular basis for this response to systemically administered helper-dependent adenoviral vector (HD-Ad), the underlying molecular components of the innate immune repertoire required to recognize the viral vector have yet to be identified. Here, we show that primary macrophages can sense HD-Ad vectors via the Toll-like Receptor 9 (TLR9) and respond by increasing pro-inflammatory cytokine secretion. Moreover, TLR9 sensing is involved in the rapid innate immune response to HD-Ad in vivo. TLR9 deficiency attenuates the innate immune response to HD-Ad, whereas TLR9 blockade reduces the acute inflammatory response after intravenous injection of the vector. Moreover, HD-Ad upregulates TLR9 gene expression independent of TLR9 function, suggesting that additional innate signaling pathways work cooperatively with TLR9. The identification of the components of the innate immune response to adenovirus will facilitate the development of combinatorial therapy directed at increasing the maximal tolerated dose of systemically delivered adenoviral vectors.

Increased hepatic transduction with reduced systemic dissemination and proinflammatory cytokines following hydrodynamic injection of helper-dependent adenoviral vectors

Hydrodynamic injection of helper-dependent adenoviral vectors (HDAd) in mice results in increased hepatic transduction, reduced splenic and pulmonary transduction, and reduced levels of the proinflammatory cytokines IL-6 and IL-12 compared to conventional injection. These results indicate that hepatic transduction by HDAd, at least alone, does not necessarily provoke a severe innate inflammatory response. Instead, they suggest that systemic vector dissemination may play a major role in the severity of the innate inflammatory response. These results further suggest that the safety and efficacy of HDAd-mediated, liver-directed gene therapy may be improved if the vector could be preferentially, if not exclusively, targeted to liver.

Long-Term Correction of Ornithine Transcarbamylase Deficiency by WPRE-Mediated Overexpression Using a Helper-Dependent Adenovirus

The urea cycle disorders (UCDs) are important models for developing gene replacement therapy for liver diseases. Long-term correction of the most common UCD, ornithine transcarbamylase (OTC) deficiency, has yet to be achieved in clinical or preclinical settings. The single human clinical trial using early-generation adenovirus (Ad) failed to show any biochemical correction. In adult OTC-deficient mice, an E1/E2-deleted Ad vector expressing the mouse OTC gene, but not the human, was only transiently therapeutic. By using post-transcriptional overexpression in the context of the less immunogenic helper-dependent adenoviral vector, we achieved metabolic correction of adult OTC-deficient mice for >6 months. Demonstrating this result were normalized orotic aciduria, normal hepatic enzyme activity, and elevated OTC RNA and protein levels in the absence of chronic hepatotoxicity. Overexpressing the human protein may have overcome two potential mechanisms accounting for poor cross-species complementation: a kinetic block at the level of mitochondrial import or a dominant negative effect by the mutant polypeptide. These data represent an important approach for treating human inborn errors of hepatocyte metabolism like the UCDs that require high-level transduction and gene expression for clinical correction.