Oluoch, P. O. | Search bioRxiv

bioRxiv2026

EBV Type 1 versus Type 2: A determinant of NK cell anti-tumor activity in Burkitt lymphoma

Terminally differentiated CD56negCD16pos NK cells have been described after chronic viral and malaria infections, and in children diagnosed with Burkitt lymphoma (BL). Despite CD56neg NK cells appearing to be poor at direct cytotoxicity, they express high levels of cytotoxic granules (i.e. granzymes, perforin), activation markers, and Fc-{gamma} receptors (CD32 and CD16) that are typically engaged in antibody-dependent cell cytotoxicity (ADCC). In addition, the abundance of CD56neg NK cells strongly correlates with IgG1 and IgG3 plasma levels, which are essential subclasses for ADCC. To determine whether CD56neg NK cells have superior ADCC capacity relative to CD56dim NK cells, we performed ADCC assays using effector cells from pediatric cancer patients and healthy children from malaria endemic regions of Kenya, targeting in vitro rituximab-treated commercial and newly established BL cell lines. We found that CD56neg NK cells were indeed capable of in vitro ADCC, showing a significant increase of CD107a-mediated degranulation in the presence of rituximab; however, they were not as efficient as CD56dim NK cells. Moreover, we found that the ADCC magnitude was significantly lower against EBV-Type 2 (EBV-T2) BL lines compared to EBV-Type 1 (EBV-T1). EBV-T2 tumor cell lines expressed significantly more lytic viral proteins than EBV-T1, making them more sensitive to direct cytotoxicity. Results from this study highlight the importance of assessing inter-patient variation in NK cell profiles in conjunction with ADCC sensitivity and EBV type within tumor cells when evaluating clinical outcomes for NK-mediated immunotherapies. SignificanceEBV type dictates NK cytotoxicity: EBV-T1 BL cells require rituximab for NK killing, while EBV-T2 BL cells are eliminated without antibody assistance, highlighting target-specific immune response to EBV-associated cancers.

immunology↗

bioRxiv2024

Chemical genetic interactions elucidate pathways controlling tuberculosis antibiotic efficacy during infection

Successful tuberculosis therapy requires treatment with an unwieldy multidrug combination for several months. Thus, there is a growing need to identify novel genetic vulnerabilities that can be leveraged to develop new, more effective antitubercular drugs. Consequently, recent efforts to optimize TB therapy have exploited Mtb chemical genetics to identify pathways influencing antibiotic efficacy, novel mechanisms of antibiotic action, and new targets for TB drug discovery. However, the influence of the complex host environment on these interactions remains largely unknown, leaving the therapeutic potential of the identified targets unclear. In this study, we leveraged a library of conditional mutants targeting 467 essential Mtb genes to characterize the chemical-genetic interactions (CGIs) with TB drugs directly in the mouse infection model. We found that these in vivo CGIs differ significantly from those identified in vitro. Both drug-specific and drug-agnostic effects were identified, and many were preserved during treatment with a multidrug combination, suggesting numerous strategies for enhancing therapy. This work also elucidated the complex effects of pyrazinamide (PZA), a drug that relies on aspects of the infection environment for efficacy. Specifically, our work supports the importance of coenzyme A synthesis inhibition during infection, as well as the antagonistic effect of iron limitation on PZA activity. In addition, we found that inhibition of thiamine and purine synthesis increases PZA efficacy, suggesting novel therapeutically exploitable metabolic dependencies. Our findings present a map of the unique in vivo CGIs, characterizing the mechanism of PZA activity in vivo and identifying novel targets for TB drug development. SignificanceThe inevitable rise of multi-drug-resistant tuberculosis underscores the urgent need for new TB drugs and novel drug targets while prioritizing synergistic drug combinations. Chemical-genetic interaction (CGI) studies have delineated bacterial pathways influencing antibiotic efficacy and uncovered druggable pathways that synergize with TB drugs. However, most studies are conducted in vitro, limiting our understanding of how the host environment influences drug-mutant interactions. Using an inducible mutant library targeting essential Mtb genes to characterize CGIs during infection, this study reveals that CGIs are both drug-specific and drug-agnostic and differ significantly from those observed in vitro. Synergistic CGIs comprised distinct metabolic pathways mediating antibiotic efficacy, revealing novel drug mechanisms of action, and defining potential drug targets that would synergize with frontline antitubercular drugs.

microbiology↗