When secretion turns into excretion - the different roles of IgA

Nasal delivery of secretory IgA confers enhanced neutralizing activity against Omicron variants compared to its IgG counterpart

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its multiple variants continue to spread worldwide, causing respiratory symptoms primarily through mucosal infection. The mucosa serves as the primary barrier against viral entry, in which secretory immunoglobulin A (sIgA) plays a critical role in preventing infection. Here, we engineered and characterized a neutralizing monoclonal antibody, ZW2G10, in IgG, monomeric, dimeric, secretory IgA1, and IgA2 formats. All seven forms of the ZW2G10 antibody showed similar thermal stability. sIgA, especially sIgA1, displayed enhanced neutralizing activity against Omicron-lineage BA.2.75, BA.2.76 and BA.4/5 pseudoviruses compared to IgG. Nasal administration of sIgA1 conferred robust protection against the BA.2.76 pseudovirus in ACE2 transgenic mice, and its protective efficacy was superior to that of IgG. The crystal structure of Omicron receptor binding domain (RBD) and ZW2G10 antibody fragment (Fab) complex revealed that ZW2G10 had no clashes with ACE2. Thus, nasal administration of sIgA may serve as a promising tool for the prevention and treatment of Omicron infection.

Design, Production, and Optimization of Antigen-Specific Recombinant Antitumor Dimeric IgA Antibody

Available cancer immunotherapies are currently restricted to extracellular targets, while chemotherapy is the only option for intracellular targets, such as mutant KRAS. Antibodies are serum immunoglobulins, each having high binding specificity against particular antigens. Patients produce antibody responses against abnormally expressed self-proteins and neoantigens presented by the cancer cells. However, despite their infiltration into the tumor beds, many times the magnitude of the antitumor antibodies produced by spontaneously infiltrated B lymphocytes remains insufficient to control tumor growth. Recent work has established that dimeric IgA antibodies can target intracellular targets inside cancer cells expressing the polymeric immunoglobulin receptor (pIgR). Here, we thoroughly discuss the entire process of recombinant production of intracellular antigen-specific dimeric IgA antibodies that could be utilized for targeting oncodrivers inside tumor cells.

B cell responses and antibody-based therapeutic perspectives in human cancers

BACKGROUND

Immuno-oncology has been focused on T cell-centric approaches until the field recently started appreciating the importance of tumor-reactive antibody production by tumor-infiltrating plasma B cells, and the necessity of developing novel therapeutic antibodies for the treatment of different cancers.

RECENT FINDINGS

B lymphocytes often infiltrate solid tumors and the extent of B cell infiltration normally correlates with stronger T cell responses while generating humoral responses against malignant progression by producing tumor antigens-reactive antibodies that bind and coat the tumor cells and promote cytotoxic effector mechanisms, reiterating the fact that the adaptive immune system works by coordinated humoral and cellular immune responses. Isotypes, magnitude, and the effector functions of antibodies produced by the B cells within the tumor environment differ among cancer types. Interestingly, apart from binding with specific tumor antigens, antibodies produced by tumor-infiltrating B cells could bind to some non-specific receptors, peculiarly expressed by cancer cells. Antibody-based immunotherapies have revolutionized the modalities of cancer treatment across the world but are still limited against hematological malignancies and a few types of solid tumor cancers with a restricted number of targets, which necessitates the expansion of the field to have newer effective targeted antibody therapeutics.

CONCLUSION

Here, we discuss about recent understanding of the protective spontaneous antitumor humoral responses in human cancers, with an emphasis on the advancement and future perspectives of antibody-based immunotherapies in cancer.

Targeting intracellular oncoproteins with dimeric IgA promotes expulsion from the cytoplasm and immune-mediated control of epithelial cancers

Dimeric IgA (dIgA) can move through cells via the IgA/IgM polymeric immunoglobulin receptor (PIGR), which is expressed mainly on mucosal epithelia. Here, we studied the ability of dIgA to target commonly mutated cytoplasmic oncodrivers. Mutation-specific dIgA, but not IgG, neutralized KRASG12D within ovarian carcinoma cells and expelled this oncodriver from tumor cells. dIgA binding changed endosomal trafficking of KRASG12D from accumulation in recycling endosomes to aggregation in the early/late endosomes through which dIgA transcytoses. dIgA targeting of KRASG12D abrogated tumor cell proliferation in cell culture assays. In vivo, KRASG12D-specific dIgA1 limited the growth of KRASG12D-mutated ovarian and lung carcinomas in a manner dependent on CD8+ T cells. dIgA specific for IDH1R132H reduced colon cancer growth, demonstrating effective targeting of a cytoplasmic oncodriver not associated with surface receptors. dIgA targeting of KRASG12D restricted tumor growth more effectively than small-molecule KRASG12D inhibitors, supporting the potential of this approach for the treatment of human cancers.

Preexisting immunity restricts mucosal antibody recognition of SARS-CoV-2 and Fc profiles during breakthrough infections

Understanding mucosal antibody responses from SARS-CoV-2 infection and/or vaccination is crucial to develop strategies for longer term immunity, especially against emerging viral variants. We profiled serial paired mucosal and plasma antibodies from COVID-19 vaccinated only vaccinees (vaccinated, uninfected), COVID-19-recovered vaccinees (recovered, vaccinated), and individuals with breakthrough Delta or Omicron BA.2 infections (vaccinated, infected). Saliva from COVID-19-recovered vaccinees displayed improved antibody-neutralizing activity, Fcγ receptor (FcγR) engagement, and IgA levels compared with COVID-19-uninfected vaccinees. Furthermore, repeated mRNA vaccination boosted SARS-CoV-2-specific IgG2 and IgG4 responses in both mucosa biofluids (saliva and tears) and plasma; however, these rises only negatively correlated with FcγR engagement in plasma. IgG and FcγR engagement, but not IgA, responses to breakthrough COVID-19 variants were dampened and narrowed by increased preexisting vaccine-induced immunity against the ancestral strain. Salivary antibodies delayed initiation following breakthrough COVID-19 infection, especially Omicron BA.2, but rose rapidly thereafter. Importantly, salivary antibody FcγR engagements were enhanced following breakthrough infections. Our data highlight how preexisting immunity shapes mucosal SARS-CoV-2-specific antibody responses and has implications for long-term protection from COVID-19.