Non-neutralizing antibodies targeting the immunogenic regions of HIV-1 envelope reduce mucosal infection and virus burden in humanized mice.

Antibodies are principal immune components elicited by vaccines to induce protection from microbial pathogens. In the Thai RV144 HIV-1 vaccine trial, vaccine efficacy was 31% and the sole primary correlate of reduced risk was shown to be vigorous antibody response targeting the V1V2 region of HIV-1 envelope. Antibodies against V3 also were inversely correlated with infection risk in subsets of vaccinees. Antibodies recognizing these regions, however, do not exhibit potent neutralizing activity. Therefore, we examined the antiviral potential of poorly neutralizing monoclonal antibodies (mAbs) against immunodominant V1V2 and V3 sites by passive administration of human mAbs to humanized mice engrafted with CD34+ hematopoietic stem cells, followed by mucosal challenge with an HIV-1 infectious molecular clone expressing the envelope of a tier 2 resistant HIV-1 strain. Treatment with anti-V1V2 mAb 2158 or anti-V3 mAb 2219 did not prevent infection, but V3 mAb 2219 displayed a superior potency compared to V1V2 mAb 2158 in reducing virus burden. While these mAbs had no or weak neutralizing activity and elicited undetectable levels of antibody-dependent cellular cytotoxicity (ADCC), V3 mAb 2219 displayed a greater capacity to bind virus- and cell-associated HIV-1 envelope and to mediate antibody-dependent cellular phagocytosis (ADCP) and C1q complement binding as compared to V1V2 mAb 2158. Mutations in the Fc region of 2219 diminished these effector activities in vitro and lessened virus control in humanized mice. These results demonstrate the importance of Fc functions other than ADCC for antibodies without potent neutralizing activity.

Targeting disialoganglioside GD2 with chimeric antigen receptor-redirected T cells in lung cancer.

BACKGROUND: We explored whether the disialoganglioside GD2 (GD2) is expressed in small cell lung cancer (SCLC) and non-SCLC (NSCLC) and can be targeted by GD2-specific chimeric antigen receptor (CAR) T cells. METHODS: GD2 expression was evaluated in tumor cell lines and tumor biopsies by flow cytometry and immunohistochemistry. We used a GD2.CAR that coexpress the IL-15 to promote T-cell proliferation and persistence, and the inducible caspase 9 gene safety switch to ablate GD2.CAR-T cells in case of unforeseen toxicity. The antitumor activity of GD2.CAR-T cells was evaluated using in vitro cocultures and in xenograft models of orthotopic and metastatic tumors. The modulation of the GD2 expression in tumor cell lines in response to an epigenetic drug was also evaluated. RESULTS: GD2 was expressed on the cell surface of four of fifteen SCLC and NSCLC cell lines (26.7%) tested by flow cytometry, and in 39% of SCLC, 72% of lung adenocarcinoma and 56% of squamous cell carcinoma analyzed by immunohistochemistry. GD2 expression by flow cytometry was also found on the cell surface of tumor cells freshly isolated from tumor biopsies. GD2.CAR-T cells exhibited antigen-dependent cytotoxicity in vitro and in vivo in xenograft models of GD2-expressing lung tumors. Finally, to explore the applicability of this approach to antigen low expressing tumors, we showed that pretreatment of GD2low/neg lung cancer cell lines with the Enhancer of zeste homolog 2 inhibitor tazemetostat upregulated GD2 expression at sufficient levels to trigger GD2.CAR-T cell cytotoxic activity. CONCLUSIONS: GD2 is a promising target for CAR-T cell therapy in lung cancer. Tazemetostat treatment could be used to upregulate GD2 expression in tumor cells, enhancing their susceptibility to CAR-T cell targeting.

THEMIS-SHP1 Recruitment by 4-1BB Tunes LCK-Mediated Priming of Chimeric Antigen Receptor-Redirected T Cells.

Chimeric antigen receptor (CAR) T cell costimulation mediated by CD28 and 4-1BB is essential for CAR-T cell-induced tumor regression. However, CD28 and 4-1BB differentially modulate kinetics, metabolism and persistence of CAR-T cells, and the mechanisms governing these differences are not fully understood. We found that LCK recruited into the synapse of CD28-encoding CAR by co-receptors causes antigen-independent CAR-CD3ζ phosphorylation and increased antigen-dependent T cell activation. In contrast, the synapse formed by 4-1BB-encoding CAR recruits the THEMIS-SHP1 phosphatase complex that attenuates CAR-CD3ζ phosphorylation. We further demonstrated that the CAR synapse can be engineered to recruit either LCK to enhance the kinetics of tumor killing of 4-1BB CAR-T cells or SHP1 to tune down cytokine release of CD28 CAR-T cells.