Revolutionizing antiviral therapy with nanobodies: Generation and prospects

As the world continues to grapple with infectious diseases, scientists are constantly searching for effective ways to combat these deadly pathogens. One promising avenue of research is the use of nanobodies as neutralization agents. These small proteins, derived from camelid antibodies, have several unique advantages over traditional antibodies, including their small size. Nanobodies are much smaller than conventional antibodies, typically weighing in at around 15 kDa compared to the 150 kDa of a typical human antibody. This small size allows them to penetrate into tight spaces that larger molecules cannot reach, such as the crevices on the surface of viruses or bacteria. This makes them highly effective at neutralizing viruses by binding to and blocking their key functional sites. In this mini-review we discuss the construction approaches of nanobodies, and some methods to increase the half-life of nanobodies. Moreover, we discuss Nanobodies and their therapeutic potential for infectious agents.

Exploring the Diversity of the B-Cell Receptor Repertoire Through High-Throughput Sequencing

Repertoire sequencing of B cells is the high-throughput profiling of B cell receptors (BCR) expressed on the surface of B cells and of immunoglobulins (Ig) expressed by antibody secreting cells. Each BCR/Ig transcript has a unique complementarity-determining region 3 (CDR3) sequence that can be used to identify and track individual B cell lymphocytes over time and throughout different compartments of the human body. B cell differentiation can be further tracked by assessing the point mutations acquired during affinity maturation via somatic hypermutation (SHM). Here we describe a method for high-throughput sequencing of the variable region of Ig heavy-chain transcripts for repertoire analysis of human B cells on the Illumina Miseq platform.

Significance of the intraindividual variability of HLA IgG antibodies in renal disease patients observed with different beadsets monitored with two different secondary antibodies on a Luminex platform

The accurate measurement of anti-HLA alloantibodies in transplant candidates is required for determining the degree of sensitization and for the listing of unacceptable antigens for organ allocation. Both the configuration of the HLA molecules coated on the beads and the nature of detection antibodies may impede assessment of the presence and strength of anti-HLA IgG- with the Luminex single-antigen-bead assay. Sera antibodies of the end-stage renal disease patients were compared using LIFECODES (LC) and LABScreen (LS) beadsets monitored with polyclonal-Fab (IgHPolyFab) and monoclonal-IgG (FcMonoIgG) second antibodies. Positive results at mean fluorescence intensity (MFI) > 500 (at serum dilution 1/10) were used to calculate panel reactive antibody (cPRA) levels. LS-beadsets are coated with monomeric variants in addition to intact HLA antigens with or without peptides, while LC-beadsets are devoid of monomeric variants and with lesser levels of peptide-free heterodimers. Consequently, IgG antibodies against both classes of HLA were reactive to more antigens with LS than with LC-beadsets. For both classes, MFIs were also frequently higher with LS than with LC. For HLA-I, MFIs were higher with IgHPolyFab than with FcMonoIgG with the exception of sera with MFIs > 5000 where they were comparable. For HLA-II, the reverse occurred, with significantly higher levels with FcMonoIgG regardless of the beadsets. The intraindividual variability observed between beadsets with two detection antibodies elucidates that antigens found as acceptable with one beadset may end up unacceptable with the other beadsets, with the possibility of denying potentially compatible transplants to candidates.

Transcriptomic analysis of immunoglobulin novel antigen receptor (IgNAR) heavy chain constant domains of brownbanded bamboo shark (Chiloscyllium punctatum)

Cartilaginous fish are the evolutionarily oldest group of animals which possess antibodies, T cell receptors and major histocompatibility complex (MHC). The immunoglobulin novel antigen receptor (IgNAR) found in cartilaginous fish is a heavy chain homodimer which lacks light chain. The presence of non-canonical cysteine molecules and lack of CDR2 region make it more significant. To synthesize active binding domains based on variable region of IgNAR (VNAR), knowledge on the constant region dynamics play a significant role. The IgNAR exhibit species variations in its primary sequence features; hence, this study was conducted to determine the IgNAR heavy chain constant domain of the brownbanded bamboo shark (Chiloscyllium punctatum). Peripheral blood leukocytes (PBL) isolated from adult bamboo sharks were used to synthesize a cDNA library. A total of four billion residues of two million sequences (average length 218.41 bp) were obtained. Assembled sequences were aligned with published cartilaginous fish IgNAR constant region sequences. Transcriptome analysis revealed two distinct types of IgNAR in the brownbanded bamboo shark. Also, constant-1 domain sequences displayed 13 unique sequences which may reflect the least number of IgNAR gene clusters. The phylogenetic analysis revealed the closest relationship with the nurse shark (Ginglymostoma cirratum) followed by the wobbegong shark (Orectolobus maculatus) which belong to the same order Orectolobiformes. Analysis of the constant domains of the brownbanded bamboo shark IgNAR revealed an evolutionarily conserved nature and this knowledge can be used to design primers for VNAR cloning. Furthermore, knowledge on the structural features in IgNAR constant domains that increase the stability could be useful in the process of stabilizing human immunoglobulins.

The antibody loci of the domestic goat (Capra hircus)

The domestic goat (Capra hircus) is an important ruminant species both as a source of antibody-based reagents for research and biomedical applications and as an economically important animal for agriculture, particularly for developing nations that maintain most of the global goat population. Characterization of the loci encoding the goat immune repertoire would be highly beneficial for both vaccine and immune reagent development. However, in goat and other species whose reference genomes were generated using short-read sequencing technologies, the immune loci are poorly assembled as a result of their repetitive nature. Our recent construction of a long-read goat genome assembly (ARS1) has facilitated characterization of all three antibody loci with high confidence and comparative analysis to cattle. We observed broad similarity of goat and cattle antibody-encoding loci but with notable differences that likely influence formation of the functional antibody repertoire. The goat heavy-chain locus is restricted to only four functional and nearly identical IGHV genes, in contrast to the ten observed in cattle. Repertoire analysis indicates that light-chain usage is more balanced in goats, with greater representation of kappa light chains (~ 20-30%) compared to that in cattle (~ 5%). The present study represents the first characterization of the goat antibody loci and will help inform future investigations of their antibody responses to disease and vaccination.

Preferential combination between the light and heavy chain isotypes of fish immunoglobulins

Immunoglobulin light chain (IgL) is necessary for the assembly of an Ig molecule, which plays important roles in the immune response. IgL genes were identified in various teleost species, but the basic functions of different IgL isotypes and the preferential combination between IgL and IgH (Ig heavy chain) isotypes remain unclear. In the current study, by EST database searching and cDNA cloning in rainbow trout, 8 IgL sequences were obtained, which could be classified into the IgLκF, IgLκG, IgLσ and IgLλ isotypes, respectively. Trout IgL isotypes were highly expressed in the immune-related tissues, and participated in the immune responses in spleen and gut by stimulation with LPS and poly (I:C). The results of FACS and LC-MS/MS indicated that the IgLκG and IgLσ isotypes preferentially bonded with the heavy chains of IgM and IgT, respectively, in trout B cells and serum. In addition, the genomic organization of trout IgL isotypes and the utilization of recombination signal sequences were studied.

Structural and functional analysis of botulinum neurotoxin subunits for pH-dependent membrane channel formation and translocation

The structure-function relationship of Botulinum Neurotoxin (BoNT) proteins is greatly influenced by pH. While the low pH of endosome favors membrane interaction of the heavy chain (HC) for the formation of a membrane channel and translocation of the light chain (LC), the catalytic activity of the LC requires a neutral pH for cleavage of the soluble NSF attachment protein receptor (SNARE) complex in the cytosol. In this study, we monitored secondary structural characteristics of LC, HC and holotoxin at individual pHs 4.5 and 7.2 and at the transition pH4.5 to 7.2 to identify the structural signatures underlying their function. The HC showed higher thermal stability at pH4.5 with a melting temperature (Tm) of 60.4°C. The structural analysis of HC in the presence of liposomes showed no difference in ellipticity with that of HC at pH7.2 at 208 and 222 nm but a 25.2% decrease in ellipticity at 208 nm at acidic pH, indicating low pH-induced structural changes that might facilitate interaction with the membrane. Further, HC showed 18% release of K+ ions from liposomes at pH4.5 as against 6% at neutral pH, reinforcing its role in membrane channel formation. LC on the other hand, showed maximum ellipticity at pH7.2, a condition that is relevant to its endopeptidase activity in the cytosol of the neurons. Also, the similarity in the structures at pH7.2 and transition pH4.5 to 7.2 suggested that the flexibility acquired by the protein at low pH was reversible upon exposure to neutral pH for cleavage of SNARE proteins.

A closer look to botulinum neurotoxin type A-induced analgesia

Chronic pain indicates a type of pain that lasts over time and is accompanied by diagnostic and therapeutic difficulties. It follows that treatment failures are common and patients roam from doctor to doctor in search of an effective care program. So there is an urgent need for long-acting and effective therapeutics to alleviate symptoms of the varied forms of chronic pain. During the past few years, a good success has been achieved with a derivative of a neurotoxin. It has been shown that administration of this toxin can block the release of neurotransmitters and pain mediators. Botulinum neurotoxin type A (BoNT/A) is well known as a treatment for neuromuscular conditions such as dystonia and spasticity. However, the clinical application for BoNT/A has continued to expand. Its analgesic effect has been used in clinical practice with satisfactory results. This review provides an introduction of a hypothesis for the mechanism by which BoNT/A eases chronic pain. It also summarizes the clinical therapeutic effects of BoNT/A in different types of chronic pain and its potential prospects.

Generation and Characterization of Mouse Hybridomas Secreting Monoclonal Antibodies Specific for Human IgG3

Mammalians express several subclasses of the IgG molecule. In human being there are four homologous IgG subclasses, each of which is structurally unique and has different functions. Quantification of IgG subclasses is fundamental to clinical assessment and diagnosis of many diseases as such assessments depends on the availability of subclassspecific antibodies (Abs), particularly monoclonal antibodies (MAbs). In the present study, we produced and characterized two murine MAbs specific for human IgG3 molecule. These MAbs were obtained by the fusion of myeloma cells with splenocytes from Balb/c mice immunized with heavy chain of a human IgG3 myeloma protein. Fused cells were selected in hypoxanthine, aminopterine and thymidine (HAT) medium and cloned by limiting dilution assay. Ab-secreting cells were screened by enzyme-linked immunosorbent assay (ELISA) and the specificity of secreted MAbs was further analyzed, using a panel of purified myeloma proteins by ELISA and immunoblotting. Two stable hybridomas designated 1F18G7 and 1F18A11 were obtained secreting MAbs specific for Fc fragment of human IgG3. None of these MAbs showed cross-reactivity with other immunoglobulin isotypes derived from human and nine other animals, except 1F18A11 which displayed a weak cross-reactivity with only dog serum. Immunoblotting results indicate that these MAbs react with linear epitope(s) located in the heavy chain of human IgG3 molecules. The affinity constant of 1F18G7 and 1F18A11 MAbs was found to be 0.81×10(9) Mol (-1) and 0.71×10(9) Mol (-1), respectively, as measured by ELISA. These two MAbs with relatively high affinity can be useful tools for quantification of IgG3 subclass levels in human serum.