Recent Advances in Host-Directed Therapies for Tuberculosis and Malaria

Mycobacterium tuberculosis protein Rv2652c enhances intracellular survival by inhibiting host immune responses

BACKGROUNDS

Mycobacterium tuberculosis (Mtb), the pathogen responsible for tuberculosis, secretes a multitude of proteins that modulate the host's immune response to ensure its own persistence. The region of difference (RD) genes encoding proteins play key roles in TB immunity and pathogenesis. Nevertheless, the roles of the majority of RD-encoded proteins remain to be elucidated.

OBJECTS

To elucidate the role of Rv2652c located in RD13 in Mtb on bacterial growth, bacterial survival, and host immune response.

METHODS

We constructed the strain MS_Rv2652c which over-expresses Mtb RD-encoding protein Rv2652c in M. smegmatis (MS), and compared it with the wild strain in the bacterial growth, bacterial survival, virulence of Rv2652c, and determined the effect of MS_Rv2652c on host immune response in macrophages.

RESULTS

Rv2652c protein is located at cell wall of MS_Rv2652c strain and also an integral component of the Mtb H37Rv cell wall. Rv2652c can enhance the resistance of recombinant MS to various stressors. Moreover, Rv2652c inhibits host proinflammatory responses via modulation of the NF-κB pathway, thereby promoting Mtb survival in vitro and in vivo.

CONCLUSION

Our data suggest that cell wall protein Rv2652c plays an important role in creating a favorable environment for bacterial survival by modulating host signals and could be established as a potential TB drug target.

In vitro evaluation of the binding activity of novel mouse IgG1 opsonic monoclonal antibodies to Mycobacterium tuberculosis and other selected mycobacterial species

Antimicrobial resistance alongside other challenges in tuberculosis (TB) therapeutics have stirred renewed interest in host-directed interventions, including the role of antibodies as adjunct therapeutic agents. This study assessed the binding efficacy of two novel IgG1 opsonic monoclonal antibodies (MABs; GG9 & JG7) at 5, 10, and 25 µg/mL to live cultures of Mycobacterium tuberculosis, M. avium, M. bovis, M. fortuitum, M. intracellulare, and M. smegmatis American Type Culture Collection laboratory reference strains, as well as clinical susceptible, multi-drug resistant, and extensively drug resistant M. tuberculosis strains using indirect enzyme-linked immunosorbent assays. These three MAB concentrations were selected from a range of concentrations used in previous optimization (binding and functional) assays. Both MABs bound to all mycobacterial species and sub-types tested, albeit to varying degrees. Statistically significant differences in MAB binding activity were observed when comparing the highest and lowest MAB concentrations (p < 0.05) for both MABs GG9 and JG7, irrespective of the M. tuberculosis resistance profile. Binding affinity increased with an increase in MAB concentration, and optimal binding was observed at 25 µg/mL. JG7 showed better binding activity than GG9. Both MABs also bound to five MOTT species, albeit at varied levels. This non-selective binding to different mycobacterial species suggests a potential role for GG9 and JG7 as adjunctive agents in anti-TB chemotherapy with the aim to enhance bacterial killing.

The potential role of protein disulfide isomerases (PDIs) during parasitic infections: a focus on Leishmania spp

Leishmaniasis is a group of vector-borne diseases caused by intracellular protozoan parasites belonging to the genus Leishmania. Leishmania parasites can employ different and numerous sophisticated strategies, including modulating host proteins, cell signaling, and cell responses by parasite proteins, to change the infected host conditions to favor the parasite persistence and induce pathogenesis. In this sense, protein disulfide isomerases (PDIs) have been described as crucial proteins that can be modulated during leishmaniasis and affect the pathogenesis process. The effect of modulated PDIs can be investigated in both aspects, parasite PDIs and infected host cell PDIs, during infection. The information concerning PDIs is not sufficient in parasitology; however, this study aimed to provide data regarding the biological functions of such crucial proteins in parasites with a focus on Leishmania spp. and their relevant effects on the pathogenesis process. Although there are no clinical trial vaccines and therapeutic approaches, highlighting this information might be fruitful for the development of novel strategies based on PDIs for the management of parasitic diseases, especially leishmaniasis.