Lipid uptake in chronic lymphocytic leukemia.

Many cancers rely on glucose as an energy source, but it is becoming increasingly apparent that some cancers use alternate substrates to fuel their proliferation. Chronic lymphocytic leukaemia (CLL) is one such cancer. Through the use of flow cytometry and confocal microscopy, low levels of glucose uptake were observed in the OSU-CLL and HG3 CLL cell lines relative to highly glucose-avid Raji cells (Burkitt's lymphoma). Glucose uptake in CLL cells correlated with low expression of the GLUT1 and GLUT3 receptors. In contrast, both CLL cell lines and primary CLL cells, but not healthy B cells, were found to rapidly internalise medium- and long-chain, but not short-chain, fatty acids (FAs). Differential FA uptake was also observed in primary cells taken from patients with unmutated immunoglobulin heavy variable chain usage (IGHV) compared with patients with mutated IGHV. Delipidation of serum in the culture medium slowed the proliferation and significantly reduced the viability of OSU-CLL and HG3 cells, effects that were partially reversed by supplementation with a chemically defined lipid concentrate. These observations highlight the potential importance of FAs in the pathogenesis of CLL and raise the possibility that targeting FA utilisation may represent a novel therapeutic and prognostic approach in this disease.

Loss of CD22 expression and expansion of a CD22dim subpopulation in adults with relapsed/refractory B-lymphoblastic leukaemia after treatment with Inotuzumab-Ozogamicin.

Treatment options for relapsed or refractory B-lymphoblastic leukaemia (r/r B-ALL) are limited and the prognosis of these patients remains dismal, but novel immunotherapeutic options such as the anti-CD22 antibody-drug-conjugate Inotuzumab-Ozogamicin (InO) have improved outcomes in these patients. Flow cytometry is essential to assess antigen-expression prior to treatment initiation of antigen-directed immunotherapies. Here, we present flow cytometric and clinical data of three adult patients with r/r B-ALL who failed treatment with InO associated with reduced or lost antigen-expression. In addition, we present comparative data on two different diagnostic CD22-specific antibody clones that exhibit significant differences in staining intensities.

Mediator subunit MED1 is required for E2A-PBX1-mediated oncogenic transcription and leukemic cell growth.

The chimeric transcription factor E2A-PBX1, containing the N-terminal activation domains of E2A fused to the C-terminal DNA-binding domain of PBX1, results in 5% of pediatric acute lymphoblastic leukemias (ALL). We recently have reported a mechanism for RUNX1-dependent recruitment of E2A-PBX1 to chromatin in pre-B leukemic cells; but the subsequent E2A-PBX1 functions through various coactivators and the general transcriptional machinery remain unclear. The Mediator complex plays a critical role in cell-specific gene activation by serving as a key coactivator for gene-specific transcription factors that facilitates their function through the RNA polymerase II transcriptional machinery, but whether Mediator contributes to aberrant expression of E2A-PBX1 target genes remains largely unexplored. Here we show that Mediator interacts directly with E2A-PBX1 through an interaction of the MED1 subunit with an E2A activation domain. Results of MED1 depletion by CRISPR/Cas9 further indicate that MED1 is specifically required for E2A-PBX1-dependent gene activation and leukemic cell growth. Integrated transcriptome and cistrome analyses identify pre-B cell receptor and cell cycle regulatory genes as direct cotargets of MED1 and E2A-PBX1. Notably, complementary biochemical analyses also demonstrate that recruitment of E2A-PBX1 to a target DNA template involves a direct interaction with DNA-bound RUNX1 that can be further stabilized by EBF1. These findings suggest that E2A-PBX1 interactions with RUNX1 and MED1/Mediator are of functional importance for both gene-specific transcriptional activation and maintenance of E2A-PBX1-driven leukemia. The MED1 dependency for E2A-PBX1-mediated gene activation and leukemogenesis may provide a potential therapeutic opportunity by targeting MED1 in E2A-PBX1+ pre-B leukemia.

Artesunate inhibits Sjögren's syndrome-like autoimmune responses and BAFF-induced B cell hyperactivation via TRAF6-mediated NF-κB signaling.

BACKGROUND: Hyperactivation of B cells by activators has been demonstrated to play a central role in the pathogenesis of Sjögren's syndrome (SS). In this study, we found that artesunate (ART) can attenuate BAFF-induced B cell hyperactivation and SS-like symptoms in NOD/Ltj mice. PURPOSE: To determine the efficacy of ART in attenuating SS-like symptoms in vivo and explore the underlying mechanism in vitro. STUDY DESIGN: ART was intragastrically injected into SS-like NOD/Ltj mice. The cytokine hsBAFF was used to activate Raji and Daudi B cells to mimic B cell hyperactivation in vitro. METHODS: The efficacy of ART in inhibiting SS progression was studied in NOD/Ltj mice. Salivary flow rate, the number of lymphocytic infiltration foci, the level of autoantibodies and the extent of B cell infiltration were measured in the indicated groups. CCK-8 assays, flow cytometry-based EdU staining and Annexin V/PI staining were also used to detect the effect of ART on the survival and proliferation mechanism in BAFF-induced Raji and Daudi cells. Further studies determined that TRAF6 degradation is a potential mechanism by which ART determines B cell fate. RESULTS: Treatment with ART inhibited lymphocytic foci formation, B cell infiltration and autoantibody secretion in SS-like NOD/Ltj mice. In vitro assay results indicated that ART effectively inhibited BAFF-induced viability, survival and proliferation of neoplastic B cells. Mechanistically, ART targeted BAFF-activated NFκB by regulating the proteasome-mediated degradation of TRAF6 in Raji and Daudi cells. CONCLUSION: ART ameliorated murine SS-like symptoms and regulated TRAF6-NFκB signaling, thus determining survival and proliferation of B cells.

Immunoactive polysaccharides produced by heterotrophic mutant of green microalga Parachlorella kessleri HY1 (Chlorellaceae).

Hot water extract from biomass of heterotrophic mutant green alga Parachlorella kessleri HY1 (Chlorellaceae) was deproteinised, and three polysaccharidic fractions were obtained by preparative chromatography. The low-molecular fraction (1.5 × 104g mol-1) was defined mainly as branched O-2-ß-xylo-(1→3)-ß-galactofuranan where xylose is partially methylated at O-4. Two high-molecular fractions (3.05 × 105 and 9.84 × 104g mol-1) were complex polysaccharides containing α-l-rhamnan and xylogalactofuranan parts in different ratios. The polysaccharides were well soluble in hot water and, upon cooling, tended to self-segregate. Immunomodulatory activities of the obtained fractions were preliminary tested using ELISA, FACS and ImmunoSpot kits. The polysaccharides increased the TNF-α production in melanoma bearing mice with much higher intensity than in healthy mice. This was in agreement with the FACS results on T and B cells indicating their possibly secondary activation by innate immunity cells.

Allergen-specific IgG+ memory B cells are temporally linked to IgE memory responses.

BACKGROUND: IgE is the least abundant immunoglobulin and tightly regulated, and IgE-producing B cells are rare. The cellular origin and evolution of IgE responses are poorly understood. OBJECTIVE: The cellular and clonal origin of IgE memory responses following mucosal allergen exposure by sublingual immunotherapy (SLIT) were investigated. METHODS: In a randomized double-blind, placebo-controlled, time course SLIT study, PBMCs and nasal biopsy samples were collected from 40 adults with seasonal allergic rhinitis at baseline and at 4, 8, 16, 28, and 52 weeks. RNA was extracted from PBMCs, sorted B cells, and nasal biopsy samples for heavy chain variable gene repertoire sequencing. Moreover, mAbs were derived from single B-cell transcriptomes. RESULTS: Combining heavy chain variable gene repertoire sequencing and single-cell transcriptomics yielded direct evidence of a parallel boost of 2 clonally and functionally related B-cell subsets of short-lived IgE+ plasmablasts and IgG+ memory B cells. Mucosal grass pollen allergen exposure by SLIT resulted in highly diverse IgE and IgGE repertoires. These were extensively mutated and appeared relatively stable as per heavy chain isotype, somatic hypermutations, and clonal composition. Single IgGE+ memory B-cell and IgE+ preplasmablast transcriptomes encoded antibodies that were specific for major grass pollen allergens and able to elicit basophil activation at very low allergen concentrations. CONCLUSION: For the first time, we have shown that on mucosal allergen exposure, human IgE memory resides in allergen-specific IgG+ memory B cells. These cells rapidly switch isotype, expand into short-lived IgE+ plasmablasts, and serve as a potential target for therapeutic intervention.

Antitumor effect of baicalin from the Scutellaria baicalensis radix extract in B-acute lymphoblastic leukemia with different chromosomal rearrangements.

Acute B-lymphoblastic leukemia (B-ALL) is the most common hematologic malignancy in children. Many cases of B-ALL harbor chromosomal translocations which are often critical determinants of prognosis. Most of them represent altered transcription factors that impact gene transcription or enhance signaling. B-ALLs harboring the mixed-lineage leukemia 1 (MLL1) gene rearrangements represent aggressive, high-risk type of early childhood leukemias that are usually associated with a very poor prognosis. Therefore, there is an urgent need for novel therapeutic agents as well as new treatment strategies. The objective was to examine the vitro inhibitory effects of Scutellaria baicalensis root extract (SBE) in B-ALL cell lines with different chromosomal rearrangements and in leukemic blasts derived from patients' bone marrow (BMCs). In this study we showed that baicalin which is the main component of the SBE possess antitumor activity against all leukemic cell lines especially those with MLL and PBX1 gene rearrangements. Baicalin inhibited cell proliferation, arrested the cell cycle at the G0/G1 phase, and induced cell death through caspase 3/7 activation. Moreover, baicalin treatment inhibited the glycogen synthase kinase-3ß (GSK-3ß) by suppressing its phosphorylation at Y216, and upregulated the downstream mediator of the cell cycle arrest - cyclin dependent kinase inhibitor p27Kip1. Bone marrow derived blasts from B-ALL patients also exhibited varied sensitivity towards baicalin with 72% patients sensitive to the SBE and baicalin treatment. Taken together, our findings provide new insights into the anti-cancer properties of baicalin by showing its diverse mode of action which might be related to the different genetic background.

Selenium supplementation suppresses immunological and serological features of lupus in B6.Sle1b mice.

Systemic lupus erythematosus (SLE) is a debilitating multi-factorial immunological disorder characterized by increased inflammation and development of anti-nuclear autoantibodies. Selenium (Se) is an essential trace element with beneficial anti-cancer and anti-inflammatory immunological functions. In our previous proteomics study, analysis of Se-responsive markers in the circulation of Se-supplemented healthy men showed a significant increase in complement proteins. Additionally, Se supplementation prolonged the life span of lupus prone NZB/NZW-F1 mice. To better understand the protective immunological role of Se in SLE pathogenesis, we have investigated the impact of Se on B cells and macrophages using in vitro Se supplementation assays and the B6.Sle1b mouse model of lupus with an oral Se or placebo supplementation regimen. Analysis of Se-treated B6.Sle1b mice showed reduced splenomegaly and splenic cellularity compared to untreated B6. Sle1b mice. A significant reduction in total B cells and notably germinal center (GC) B cell numbers was observed. However, other cell types including T cells, Tregs, DCs and pDCs were unaffected. Consistent with reduced GC B cells there was a significant reduction in autoantibodies to dsDNA and SmRNP of the IgG2b and IgG2c subclass upon Se supplementation. We found that increased Se availability leads to impaired differentiation and maturation of macrophages from mouse bone marrow derived progenitors in vitro. Additionally, Se treatment during in vitro activation of B cells with anti-CD40L and LPS inhibited optimal B cell activation. Overall our data indicate that Se supplementation inhibits activation, differentiation and maturation of B cells and macrophages. Its specific inhibitory effect on B cell activation and GC B cell differentiation could be explored as a potential therapeutic supplement for SLE patients.

The effect of hexanic extract of Serenoa repens on prostatic inflammation: results from a randomized biopsy study.

PURPOSE: To evaluate the effect of hexanic extract of Serenoa repens (HESr) on prostatic inflammation in patients with diagnosed prostatic inflammation. METHODS: Patients with prostatic inflammation histologically confirmed by TRUS prostatic biopsy were randomized either to receive HESr (320 mg/day) or no treatment. A second biopsy was performed 6 months later according to standard clinical practice. Inflammation was assessed by the Irani's score and immunohistochemical staining using the CD3, CD4 and CD8 (for T-leucocytes), CD20 (for B-leucocytes) and CD163 (for macrophages) antibodies. RESULTS: Overall 97 patients were eligible for analysis. In the HESr group the mean inflammation grading and aggressiveness grading score significantly decreased from 1.55 and 1.55 at baseline to 0.79 (p = 0.001) and 0.87 (p = 0.001) at the second biopsy, respectively. In the control group the mean inflammation grading score was 1.44 at first biopsy and 1.23 at the second biopsy. The mean aggressiveness gradings core was 1.09 and 0.89, respectively. No statistical significance was found (p = 0.09 and p = 0.74).The mean decrease in all inflammation scores was statistically higher in the HESr patients compared to controls. The immunohistochemical staining showed a significant change in the expression of the analyzed antibodies for the HESr patients compared to the first biopsy. In the nontreatment group, no significant difference was found at the second biopsy. The change in expression of each antibody in the HESr group was statistical significant compared to control. CONCLUSIONS: HESr seems to reduce prostatic inflammation in terms of histological and immunohistochemical parameters in this specific patients population.

Cellular Composition of the B- and T-Cell-Dependent Areas in the Small Intestine during the Post-Stress Period (Experimental Study).

A quantitative study of lymphoid cells in the B- and T-cell-dependent areas of intestinal lymphoid nodules and mesenteric lymph nodes in behaviorally passive and active rats was performed at various periods after acute stress on the model of 1-h immobilization with simultaneous electrocutaneous stimulation. Stress exposure is accompanied by a decrease in the number of lymphoid cells in immunogenic structures of the gastrointestinal tract. Post-stress changes in the cytoarchitectonics of B- and T-cell-dependent areas in mesenteric lymph nodes of animals are less pronounced than in lymphoid nodules. Quantitative changes in lymphoid cells of B-cell-dependent areas in the small intestine of rats are greater than in T-cell-dependent areas. Changes in the cellular composition of immunogenic structures in the digestive system are most significant at the early stages of the post-stress period (1st week). Passive rats are characterized by significant changes in the cytoarchitectonics of B- and Tcell-dependent areas in the small intestine after extreme exposure, which illustrates functional exhaustion of the lymphoid tissue in stress-predisposed specimens.

Bruton's tyrosine kinase inhibitor BMS-986142 in experimental models of rheumatoid arthritis enhances efficacy of agents representing clinical standard-of-care.

Bruton's tyrosine kinase (BTK) regulates critical signal transduction pathways involved in the pathobiology of rheumatoid arthritis (RA) and other autoimmune disorders. BMS-986142 is a potent and highly selective reversible small molecule inhibitor of BTK currently being investigated in clinical trials for the treatment of both RA and primary Sjögren's syndrome. In the present report, we detail the in vitro and in vivo pharmacology of BMS-986142 and show this agent provides potent and selective inhibition of BTK (IC50 = 0.5 nM), blocks antigen receptor-dependent signaling and functional endpoints (cytokine production, co-stimulatory molecule expression, and proliferation) in human B cells (IC50 ≤ 5 nM), inhibits Fcγ receptor-dependent cytokine production from peripheral blood mononuclear cells, and blocks RANK-L-induced osteoclastogenesis. Through the benefits of impacting these important drivers of autoimmunity, BMS-986142 demonstrated robust efficacy in murine models of rheumatoid arthritis (RA), including collagen-induced arthritis (CIA) and collagen antibody-induced arthritis (CAIA). In both models, robust efficacy was observed without continuous, complete inhibition of BTK. When a suboptimal dose of BMS-986142 was combined with other agents representing the current standard of care for RA (e.g., methotrexate, the TNFα antagonist etanercept, or the murine form of CTLA4-Ig) in the CIA model, improved efficacy compared to either agent alone was observed. The results suggest BMS-986142 represents a potential therapeutic for clinical investigation in RA, as monotherapy or co-administered with agents with complementary mechanisms of action.

Drug discovery and therapeutic delivery for the treatment of B and T cell tumors.

Hematological malignancies manifest as lymphoma, leukemia, and myeloma, and remain a burden on society. From initial therapy to endless relapse-related treatment, societal burden is felt not only in the context of healthcare cost, but also in the compromised quality of life of patients. Long-term therapeutic strategies have become the standard in keeping hematological malignancies at bay as these cancers develop resistance to each round of therapy with time. As a result, there is a continual need for the development of new drugs to combat resistant disease in order to prolong patient life, if not to produce a cure. This review aims to summarize advances in targeting lymphoma, leukemia, and myeloma through both cutting-edge and well established platforms. Current standard of treatment will be reviewed for these malignancies and emphasis will be made on new therapy development in the areas of antibody engineering, epigenetic small molecule inhibiting drugs, vaccine development, and chimeric antigen receptor cell engineering. In addition, platforms for the delivery of these and other drugs will be reviewed including antibody-drug conjugates, micro- and nanoparticles, and multimodal hydrogels. Lastly, we propose that tissue engineered constructs for hematological malignancies are the missing link in targeted drug discovery alongside mouse and patient-derived xenograft models.

Present and future of biologic drugs in primary Sjögren's syndrome.

INTRODUCTION: Primary Sjögren's (pSS) syndrome is a chronic, autoimmune, and systemic disease characterized by xerostomia, xerophthalmia, muscle pain and fatigue. The disease may be complicated by a systemic involvement, such as a pulmonary fibrosis or the development of lymphoma which severely worsens the prognosis. Actually, there are no recommendations for the management of pSS. However, recent advances in the understanding of its pathogenesis have uncovered some pathways that have potential as therapeutic targets. Areas covered: In this review, the authors present the biologic drugs potentially valuable to the treatment of pSS in light of its physiopathology with a 'bird's eye' view of future prospects. The authors took into account relevant studies published from 2004 to 2016. Expert opinion: Biological treatment in pSS is a promising opportunity to potentially control disease activity and prevent its complication. Currently, inhibition of B-cell and IL-17 pathways seem to be the most promising avenues. New achievements in the knowledge of pSS pathophysiology are necessary in order to try to simultaneously predict the predominant pathogenic pathway, the kind of patients at major risk to develop a more severe disease, and the appropriate biological therapy to use.

Epitope analysis of Japanese cedar pollen allergen Cry j2 with a human IgM class monoclonal antibody 404-117.

Japanese cedar pollen allergen Cry j2 is a causal allergen of seasonal pollinosis in Japan. To analyze B cell epitopes of Cry j2, we established two human-mouse hybridomas secreting IgM class human monoclonal antibodies to Cry j2. A pin-peptide enzyme-linked immunosorbent assay with synthesized icosa peptides showed that 404-117 monoclonal antibody bound to peptides #11-13 with cry j2 amino acid sequence of 101F-L140. Detailed analysis with octa peptides and alanine substituted peptides indicated that an amino acid sequence of 118FKVD121 was an essential for antibody binding. When K119 (Asn) was substituted with alanine, 404-117 monoclonal antibody did not bind to the alanine substituted peptide. We concluded that the 118FKVD121 sequence might have a very important role in early recognition by Cry j2-specific B cells, which could act as antigen presenting cells.

B-Cell Disorders and Curcumin.

Clinical studies with patients with early hematological malignancies (ie, monoclonal gammopathy of undetermined significance, smoldering multiple myeloma, or stage 0/1 chronic lymphocytic leukemia) suggest that early intervention with curcumin, derived from the spice turmeric, may lead to prolonged survival and delay in progressive disease in some of these patients.

Modulatory effects of vitamin D on peripheral cellular immunity in patients with recurrent miscarriage.

PROBLEM: We aimed to investigate the modulatory effects of vitamin D on peripheral blood cellular immune response in patients with recurrent miscarriage (RM). METHOD OF STUDY: The effect of vitamin D on the number of peripheral blood cells, T helper 1 (Th1) cytokines, and NK cytotoxicity was measured in 99 women with RM. RESULTS: The percentage of CD19+ B cells and NK cytotoxicity at an effector-to-target cell (E:T) ratio of 50:1, 25:1, and 12.5:1 were significantly higher in the vitamin D insufficiency group (VDI) than in the vitamin D normal group (VDN) (P<.05 each). The proportion of TNF-α-expressing Th cells was significantly higher in the vitamin D deficiency group (VDD) than in VDN (P<.05). However, there were no significant differences between VDI and VDD. This dysregulation was significantly reduced with 1,25(OH)2 D supplementation. CONCLUSION: The data suggest that the abnormalities of cellular immune response were observed in RM patients with a low vitamin D level, which could be regulated to some extent with 1,25(OH)2 D supplementation.

Rewired NFκB signaling as a potentially actionable feature of activated B-cell-like diffuse large B-cell lymphoma.

Diffuse large B-cell lymphoma (DLBCL) is the most common type of aggressive lymphoma in the Western world and remains a clinical challenge. Two types of DLBCL are distinguishable, namely a germinal center B-cell-like phenotype (GCB) and an activated B-cell-like phenotype (ABC). Particularly ABC-DLBCL is difficult to treat, as this subentity typically displays resistance against frontline chemo-immune therapy. Through the availability of novel experimental technologies, such as next-generation sequencing and cutting-edge mouse models, we recently caught an unprecedentedly detailed glimpse at the genomic and biological features of ABC-DLBCL. Currently, a picture is emerging which suggests that ABC-DLBCL critically depends on sustained activity of the NFκB pathway, which, among others, is achieved through numerous distinct genetic aberrations, including CD79A/B-, CARD11-, and MYD88 mutations. Further genomic aberrations include amplifications of BCL2 and inactivating mutations in PRMD1. These molecular insights have spurred the development of novel autochthonous mouse models that faithfully mimic the biology and genetics of human ABC-DLBCL and could serve as preclinical platforms in future experiments. Furthermore, our genomic understanding of the disease now enables us to develop and validate novel targeted therapeutic intervention strategies that aim at decapitating non-physiological NFκB activity and repressing anti-apoptotic BCL2 signaling. In this review, we highlight these recent developments and make suggestions for further tool development and the design and stratification of future clinical trials.

Preclinical Evaluation of the Novel BTK Inhibitor Acalabrutinib in Canine Models of B-Cell Non-Hodgkin Lymphoma.

Acalabrutinib (ACP-196) is a second-generation inhibitor of Bruton agammaglobulinemia tyrosine kinase (BTK) with increased target selectivity and potency compared to ibrutinib. In this study, we evaluated acalabrutinib in spontaneously occurring canine lymphoma, a model of B-cell malignancy similar to human diffuse large B-cell lymphoma (DLBCL). First, we demonstrated that acalabrutinib potently inhibited BTK activity and downstream effectors in CLBL1, a canine B-cell lymphoma cell line, and primary canine lymphoma cells. Acalabrutinib also inhibited proliferation in CLBL1 cells. Twenty dogs were enrolled in the clinical trial and treated with acalabrutinib at dosages of 2.5 to 20mg/kg every 12 or 24 hours. Acalabrutinib was generally well tolerated, with adverse events consisting primarily of grade 1 or 2 anorexia, weight loss, vomiting, diarrhea and lethargy. Overall response rate (ORR) was 25% (5/20) with a median progression free survival (PFS) of 22.5 days. Clinical benefit was observed in 30% (6/20) of dogs. These findings suggest that acalabrutinib is safe and exhibits activity in canine B-cell lymphoma patients and support the use of canine lymphoma as a relevant model for human non-Hodgkin lymphoma (NHL).

Immunogenicity of Outer Membrane Proteins VirB9-1 and VirB9-2, a Novel Nanovaccine against Anaplasma marginale.

Anaplasma marginale is the most prevalent tick-borne livestock pathogen and poses a significant threat to cattle industry. In contrast to currently available live blood-derived vaccines against A. marginale, alternative safer and better-defined subunit vaccines will be of great significance. Two proteins (VirB9-1 and VirB9-2) from the Type IV secretion system of A. marginale have been shown to induce humoral and cellular immunity. In this study, Escherichia coli were used to express VirB9-1 and VirB9-2 proteins. Silica vesicles having a thin wall of 6 nm and pore size of 5.8 nm were used as the carrier and adjuvant to deliver these two antigens both as individual or mixed nano-formulations. High loading capacity was achieved for both proteins, and the mouse immunisation trial with individual as well as mixed nano-formulations showed high levels of antibody titres over 107 and strong T-cell responses. The mixed nano-formulation also stimulated high-level recall responses in bovine T-cell proliferation assays. These results open a promising path towards the development of efficient A. marginale vaccines and provide better understanding on the role of silica vesicles to deliver multivalent vaccines as mixed nano-formulations able to activate both B-cell and T-cell immunity, for improved animal health.

The function and affinity maturation of HIV-1 gp120-specific monoclonal antibodies derived from colostral B cells.

Despite the risk of transmitting HIV-1, mothers in resource-poor areas are encouraged to breastfeed their infants because of beneficial immunologic and nutritional factors in milk. Interestingly, in the absence of antiretroviral prophylaxis, the overwhelming majority of HIV-1-exposed, breastfeeding infants are naturally protected from infection. To understand the role of HIV-1 envelope (Env)-specific antibodies in breast milk in natural protection against infant virus transmission, we produced 19 HIV-1 Env-specific monoclonal antibodies (mAbs) isolated from colostrum B cells of HIV-1-infected mothers and investigated their specificity, evolution, and anti-HIV-1 functions. Despite the previously reported genetic compartmentalization and gp120-specific bias of colostrum HIV Env-specific B cells, the colostrum Env-specific mAbs described here demonstrated a broad range of gp120 epitope specificities and functions, including inhibition of epithelial cell binding and dendritic cell-mediated virus transfer, neutralization, and antibody-dependent cellular cytotoxicity. We also identified divergent patterns of colostrum Env-specific B-cell lineage evolution with respect to crossreactivity to gastrointestinal commensal bacteria, indicating that commensal bacterial antigens play a role in shaping the local breast milk immunoglobulin G (IgG) repertoire. Maternal vaccine strategies to specifically target this breast milk B-cell population may be necessary to achieve safe breastfeeding for all HIV-1-exposed infants.