Development of functional human monoclonal single-chain variable fragment antibody against HIV-1 from human cervical B cells

Deciphering the Role of Mucosal Immune Responses and the Cervicovaginal Microbiome in Resistance to HIV Infection in HIV-Exposed Seronegative (HESN) Women

The female genital tract (FGT) is an important site of human immunodeficiency virus (HIV) infection. Discerning the nature of HIV-specific local immune responses is crucial for identifying correlates of protection in HIV-exposed seronegative (HESN) individuals. The present study involved a comprehensive analysis of soluble immune mediators, secretory immunoglobulins (sIg), natural killer (NK) cells, CXCR5⁺ CD8⁺ T cells, T follicular helper (Tfh) cells, and T regulatory cells (Tregs) in the vaginal mucosa as well as the nature and composition of the cervicovaginal microbiome in HESN women. We found significantly elevated antiviral cytokines, soluble immunoglobulins, and increased frequencies of activated NK cells, CXCR5⁺ CD8⁺ T cells, and Tfh cells in HESN females compared to HIV-unexposed healthy (UH) women. Analysis of the genital microbiome of HESN women revealed a greater bacterial diversity and increased abundance of Gardnerella spp. in the mucosa. The findings suggest that the female genital tract of HESN females represents a microenvironment equipped with innate immune factors, antiviral mediators, and critical T cell subsets that protect against HIV infection.

IMPORTANCE The vast majority of human immunodeficiency virus (HIV) infections across the world occur via the sexual route. The genital tract mucosa is thus the primary site of HIV replication, and discerning the nature of HIV-specific immune responses in this compartment is crucial. The role of the innate immune system at the mucosal level in exposed seronegative individuals and other HIV controllers remains largely unexplored. This understanding can provide valuable insights to improve vaccine design. We investigated mucosal T follicular helper (Tfh) cells, CXCR5⁺ CD8⁺ T cells, natural killer (NK) cells subsets, soluble immune markers, and microbiome diversity in HIV-exposed seronegative (HESN) women. We found a significantly higher level of mucosal CXCR5⁺ CD8⁺ T cells, CD4⁺ Tfh cells, activated NK cell subsets, and antiviral immune cell mediators in HESN women. We also found a higher abundance of Gardnerella spp., microbiome dysbiosis, and decreased levels of inflammatory markers to be associated with reduced susceptibility to HIV infection. Our findings indicate that increased distribution of mucosal NK cells, CXCR5⁺ CD8⁺ T cells, Tfh cells, and soluble markers in HIV controllers with a highly diverse cervicovaginal microbiome could contribute effectively to protection against HIV infection. Overall, our findings imply that future vaccine design should emphasize inducing these highly functional cell types at the mucosal sites.

Novel Antibody Drug Conjugates Targeting Tumor-Associated Receptor Tyrosine Kinase ROR2 by Functional Screening of Fully Human Antibody Libraries Using Transpo-mAb Display on Progenitor B Cells

Receptor tyrosine kinase-like orphan receptor 2 (ROR2) has been identified as a highly relevant tumor-associated antigen in a variety of cancer indications of high unmet medical need, including renal cell carcinoma and osteosarcoma, making it an attractive target for targeted cancer therapy. Here, we describe the de novo discovery of fully human ROR2-specific antibodies and potent antibody drug conjugates (ADCs) derived thereof by combining antibody discovery from immune libraries of human immunoglobulin transgenic animals using the Transpo-mAb mammalian cell-based IgG display platform with functional screening for internalizing antibodies using a secondary ADC assay. The discovery strategy entailed immunization of transgenic mice with the cancer antigen ROR2, harboring transgenic IgH and IgL chain gene loci with limited number of fully human V, D, and J gene segments. This was followed by recovering antibody repertoires from the immunized animals, expressing and screening them as full-length human IgG libraries by transposon-mediated display in progenitor B lymphocytes ("Transpo-mAb Display") for ROR2 binding. Individual cellular "Transpo-mAb" clones isolated by single cell sorting and capable of expressing membrane-bound as well as secreted human IgG were directly screened during antibody discovery, not only for high affinity binding to human ROR2, but also functionally as ADCs using a cytotoxicity assay with a secondary anti-human IgG-toxin-conjugate. Using this strategy, we identified and validated 12 fully human, monoclonal anti-human ROR2 antibodies with nanomolar affinities that are highly potent as ADCs and could be promising candidates for the therapy of human cancer. The screening for functional and internalizing antibodies during the early phase of antibody discovery demonstrates the utility of the mammalian cell-based Transpo-mAb Display platform to select for functional binders and as a powerful tool to improve the efficiency for the development of therapeutically relevant ADCs.

Cervical HIV-specific IgA in a population of commercial sex workers correlates with repeated exposure but not resistance to HIV

We conducted a comprehensive cross-sectional analysis of total and HIV-specific cervical antibody levels in HIV-1-resistant, uninfected, and infected women in order to examine the role of HIV-specific antibody responses in the female genital tract and examine the effect on antibody levels of various epidemiologic factors in this population. Cervical lavages were collected from 272 subjects of the Pumwani commercial sex worker cohort. Total and HIV-specific genital tract IgA and IgG levels were measured using an ELISA and correlated with behavioral and demographic factors. No significant difference was seen between cervical HIV-specific IgA levels in infected, uninfected, and resistant individuals, nor were any correlations between cervical HIV-specific IgA and neutralization capacity or viral shedding seen. We did, however, note increased HIV-specific IgA in HIV-negative women with four or more clients per day, and decreased HIV-specific IgA in both long-term nonprogressors and long-term survivors. These results show that there is not a strong cohort-wide correlation between HIV-specific cervical IgA levels and resistance to infection by HIV-1 as previously believed, but there is a correlation between exposure to HIV and HIV-specific cervical IgA. Our findings do not preclude the possibility that functional differences in the cervical IgA of HEPS women may play a role in resistance, but argue that HIV-specific responses may not be a universal protective factor. They also indicate that resistance to HIV is a complex condition related to more factors than exposure. Further studies of correlates of immune protection in these individuals would be beneficial to the field.

Interrogating genomes with combinatorial artificial transcription factor libraries: asking zinc finger questions

Artificial transcription factors (ATFs) are proteins designed to specifically bind and regulate genes. Because of their DNA-binding selectivity and modular organization, arrays of zinc finger (ZF) domains have traditionally been used to build the ATF's DNA-binding domains. ATFs have been designed and constructed to regulate a variety of therapeutic targets. Recently, novel combinatorial technologies have been developed to induce expression of any gene of interest or to modify cellular phenotypes. Large repertoires of ATFs have been generated by recombination of all available sequence-specific ZF lexicons. These libraries comprise millions of ATFs with unique DNA-binding specificities. The ATFs are produced by combinatorial assembly of three- and six-ZF building blocks and are linked to activator or repressor domains. Upon delivery into a cell population, any gene in the human genome can potentially be regulated. ATF library members generate genome-wide, experimental perturbations of gene expression, resulting in a phenotypically diverse population, or cellular library. A variety of phenotypic screenings can be applied to select for cells exhibiting a phenotype of interest. The ATFs are then used as genetic probes to identify the targeted genes responsible for the phenotypic switch. In this review we will summarize several applications of ATF library screenings in gene discovery, biotechnology, and disease therapeutics.

Rational monoclonal antibody development to emerging pathogens, biothreat agents and agents of foreign animal disease: The antigen scale

Many factors influence the choice of methods used to develop antibody to infectious agents. In this paper, we review the current status of the main technologies used to produce monoclonal antibodies (mAbs) from the B cells of antigen-sensitized animals. While companies are adopting advanced high-throughput methods, the major technologies used by veterinary and medical research laboratories are classical hybridoma fusion and recombinant library selection techniques. These methods have inherent advantages and limitations but have many common aspects when using immunized rodents. Laboratories with expertise in both methods of antibody development have a distinct advantage in their ability to advance mAb technology. New and re-emerging infectious threats in today's world emphasize the need for quality immunoreagents and the need to maintain expertise in mAb development. We provide examples of some common applications for mAb reagents used to identify pathogens such as the SARS-coronavirus (SARS-CoV), Bacillus anthracis, and foot-and-mouth disease (FMD) virus. We also outline a framework for investigators to make rational decisions concerning which method to use to develop mAbs based upon characteristics of the pathogen under study and the intended downstream application. Lastly, we provide parameters for the immunisation of mice and a classification system which describes the expected outcome for mAb development strategies when using classes of immunogens to generate mAbs with desired activities.

Molecular analysis of monoclonal antibodies to group variant capsular polysaccharide of Neisseria meningitidis: recurrent heavy chains and alternative light chain partners

We determined the molecular sequence of monoclonal antibodies (mAbs) to serogroups B and C capsular polysaccharides (PS) of Neisseria meningitidis. N. meningitidis infections are a leading cause of bacterial septicemia and meningitis in humans. Antibodies to PS are fundamental to host defense and diagnostics. The polysaccharide capsule of group B N. meningitidis is poorly immunogenic and thus is an important model for studying pathogen-host co-evolution through understanding the molecular basis of the host immune response. We used a modified reverse-transcriptase PCR to amplify and sequence the V-genes of murine hybridomas produced against types B and C capsular PS. Databank analysis of the sequences encoding the V-genes of type C capsular PS mAb, 4-2-C, reveal that heavy chain alleles are recurrently used to encode this specificity in mice. Interestingly, a V-gene from the same germline family also encodes the V-domain of mAbs 2-2-B, which targets the antigenically distinct serogroup B capsular PS. Somatic mutation, junctional diversity and alternative light chains collectively impart the specificity for these serologically distinct epitopes. Knowledge of the specific immunoglobulin genes used to target common bacterial virulence factors may lead to insights on pathogen-host co-evolution, and the potential use of this information in pre-symptomatic diagnosis is discussed.

Molecular characterization of a panel of murine monoclonal antibodies specific for the SARS-coronavirus

The availability of monoclonal antibodies (mAbs) specific for the SARS-coronavirus (SARS-CoV) is important for the development of both diagnostic tools and treatment of infection. A molecular characterization of nine monoclonal antibodies raised in immune mice, using highly purified, inactivated SARS-CoV as the inoculating antigen, is presented in this report. These antibodies are specific for numerous viral protein targets, and six of them are able to effectively neutralize SARS-CoV in vitro, including one with a neutralizing titre of 0.075 nM. A phylogenetic analysis of the heavy and light chain sequences reveals that the mAbs share considerable homology. The majority of the heavy chains belong to a single Ig germline V-gene family, while considerably more sequence variation is evident in the light chain sequences. These analyses demonstrate that neutralization ability can be correlated with specific murine V_H-gene alleles. For instance, one evident trend is high sequence conservation in the V_H chains of the neutralizing mAbs, particularly in CDR-1 and CDR-2. The results suggest that optimization of murine mAbs for neutralization of SARS-CoV infection will likely be possible, and will aid in the development of diagnostic tools and passive treatments for SARS-CoV infection.