Biology subjects

Braunstein, M.

Publications and source records attributed to Braunstein, M..

3 recordsLinked to original sources

bioRxiv2025

Inactivating conditions of therapeutic mycobacteriophages

There is a need for new therapies to treat drug resistant nontuberculous mycobacteria (NTM) disease. Bacteriophages (phages), which are viruses that infect and kill bacteria, are actively being explored as an alternative approach for treating mycobacterial diseases. Several compassionate-use cases of phage therapy for drug resistant NTM infections exhibit favorable outcomes. To further the development of phage therapy it is important to recognize and avoid conditions that negatively impact phage activity during phage production, storage, formulation, or treatment. Conversely, there is a need to inactivate free phages in certain preclinical phage therapy experiments. In this study, we investigated three mycobacteriophages BPs{Delta}33HTH-HRM10, Muddy, and ZoeJ{Delta}45 from compassionate-use NTM treatment cases for their sensitivity to a variety of conditions that included temperature, acid pH, detergents, mucus, and phage inactivating buffers. Several conditions resulted in dramatic and rapid reductions in the level of active phage while others had no effect. We also observed different sensitivities between the phages. The results provide valuable information to support further investigation and development of these phages as therapeutics.

microbiology↗

bioRxiv2023

Pharmacokinetic considerations for optimizing inhaled spray-dried pyrazinoic acid formulations

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), remains a leading cause of death with 1.6 million deaths worldwide reported in 2021. Oral pyrazinamide (PZA) is an integral part of anti-TB regimens, but its prolonged use has the potential to drive development of PZA resistant Mtb. PZA is converted to the active moiety pyrazinoic acid (POA) by the Mtb pyrazinamidase encoded by pncA, and mutations in pncA are associated with the majority of PZA resistance. Conventional oral and parenteral therapies may result in subtherapeutic exposure in the lung, hence direct pulmonary administration of POA may provide an approach to rescue PZA efficacy for treating pncA-mutant PZA-resistant Mtb. The objectives of the current study were to i) develop novel dry powder POA formulations ii) assess their feasibility for pulmonary delivery using physicochemical characterization, iii) evaluate their pharmacokinetics (PK) in the guinea pig model and iv) develop a mechanism based pharmacokinetic model (MBM) using in vivo PK data to select a formulation providing adequate exposure in epithelial lining fluid (ELF) and lung tissue. We developed three POA formulations for pulmonary delivery and characterized their PK in plasma, ELF, and lung tissue following passive inhalation in guinea pigs. Additionally, the PK of POA following oral, intravenous and intratracheal administration was characterized in guinea pigs. The MBM was used to simultaneously model PK data following administration of POA and its formulations via the different routes. The MBM described POA PK well in plasma, ELF and lung tissue. Physicochemical analyses and MBM predictions suggested that POA maltodextrin was the best among the three formulations and an excellent candidate for further development as it has: (i) the highest ELF-to-plasma exposure ratio (203) and lung tissue-to-plasma exposure ratio (30.4) compared with POA maltodextrin and leucine (75.7/16.2) and POA leucine salt (64.2/19.3); (ii) the highest concentration in ELF (CmacELF: 171 nM) within 15.5 minutes, correlating with a fast transfer into ELF after pulmonary administration (kPM: 22.6 1/h). The data from the guinea pig allowed scaling, using the MBM to a human dose of POA maltodextrin powder demonstrating the potential feasibility of an inhaled product. Table of Contents (TOC)/Abstract Graphic O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=107 SRC="FIGDIR/small/534965v1_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@c548fforg.highwire.dtl.DTLVardef@3b8efborg.highwire.dtl.DTLVardef@281d94org.highwire.dtl.DTLVardef@1ae07a2_HPS_FORMAT_FIGEXP M_FIG C_FIG

pharmacology and toxicology↗

bioRxiv2023

The SapM phosphatase arrests phagosome maturation in an ESX-1 independent manner in Mycobacterium tuberculosis and BCG

Mycobacterium tuberculosis (Mtb) is an intracellular pathogen that survives and grows in macrophages. A mechanism used by Mtb to achieve intracellular survival is to secrete effector molecules that arrest the normal process of phagosome maturation. Through phagosome maturation arrest (PMA), Mtb remains in an early phagosome and avoids delivery to degradative phagolysosomes. One PMA effector of Mtb is the secreted SapM phosphatase. Because the host target of SapM, phosphatidylinositol-3-phosphate (PI3P), is located on the cytosolic face of the phagosome, SapM needs to be both released by the mycobacteria and escape the phagosome to carry out its function. To date, the only mechanism known for Mtb molecules to escape the phagosome is phagosome permeabilization by the ESX-1 secretion system. To understand this step of SapM function in PMA, we generated identical in-frame sapM mutants in both the attenuated Mycobacterium bovis bacille Calmette-Guerin (BCG) vaccine strain, which lacks the ESX-1 system, and Mtb. Characterization of these mutants demonstrated that SapM is required for PMA in both BCG and Mtb. Further, by establishing a role for SapM in PMA in BCG, and subsequently in a Mtb mutant lacking the ESX-1 system, we demonstrated that the role of SapM is ESX-1-independent. We further determined that ESX-2 or ESX-4 are also not required for SapM to function in PMA. These results indicate that SapM is a secreted effector of PMA in both BCG and Mtb and that it functions independent of the known mechanism for Mtb molecules to escape the phagosome.

microbiology↗