Antibody Therapy: Past, Present and Future

Review Article

Austin Biochem. 2021; 6(1): 1029.

Antibody Therapy: Past, Present and Future

Moitra D¹, Miraclin Prasanna A¹, Gul N² and Sen P¹*

¹Centre for Bio separation Technology, Vellore Institute of Technology, Vellore, India

²Govt College for Women, Srinagar, India

*Corresponding author: Priyankar Sen, Centre for Bio separation Technology, Vellore Institute of Technology, Vellore-632014, India

Received: August 05, 2021; Accepted: October 01, 2021; Published: October 08, 2021


The emergence of pandemics like SARS-CoV-2 and a gradual increase in Multidrug Resistant (MDR) infections highlights the need of innovation in therapeutics. Antibodies are one of the potential solutions for long. Antibody therapy has come very long way from the fight against infectious diseases, bacterial toxins to hybridoma technology and monoclonal antibodies. Hybridoma cells receive a deserving attention due to their antigen-specificity. But, as they were murine in origin, Human Anti Murine Antibody (HAMA) emerged. To achieve this, phage display was introduced. The emergence of molecular cloning lead to the generation of genetically engineered recombinant antibodies such as Fab, Fc, Variable Fragment (Fv), Single Chain Variable Fragments (scFv), single domain antibodies, diabodies; like scFv fragments to different moieties, such as drugs toxins, radionuclides, liposomes or quantum dots etc. Minimized antibodies have several advantages like rapid blood clearance, reduced immunogenicity, low retention time in non-target tissues, access to cryptic epitopes facilitating tumor penetration, rapid growth facilitating higher yield and lower production cost. This paper gives an overview of the history of development of antibodies and its fragments as potential therapeutic agents for the treatment of infectious diseases, one of the biggest challenges of humanity.

Keywords: scFv; Recombinant antibody; Human anti murine antibody; Single domain antibodies; Fv fragments; Fab fragments; SARS-CoV-2


Antibodies can be potent inhibitors of a number of viral infections which also include the present pandemic Coronavirus Disease 2019 COVID-19 [1-4]. The Coronavirus Disease 2019 (COVID-19) caused by a novel coronavirus Severe Acute Respiratory Syndrome- Coronavirus-2 (SARS-CoV-2) has started in Wuhan, China and then received a worldwide attention. Researchers all over the world are trying their best to find effective therapeutic agents against this virus but no such potent antiviral drug has been discovered yet. Convalescent plasma collected from recovered patients is supposed to contain viral neutralizing antibodies and thus can be potentially used for the treatment of infected individuals [2-4]. In several cases, this therapy has been applied with success [5-6]. On the other hand, the majority of death from the pandemic COVID-19 is taking place due to respiratory failure from Acute Respiratory Distress Syndrome (ARDS) [7-9]. In several patients with COVID-19, a state of hyper inflammation known as secondary haemophagocytic lymphohistiocytosis has been observed which develops a storm of cytokines after infection [10]. This hypercytokinemia is mainly responsible for acute lung injury in the infected individuals. This can be prevented by cytokine inhibitors which are mainly modulators of cytokine responses, thus playing a therapeutic role in the pathogenesis of COVID-19 [11]. Among the proinflammatory cytokines, Tumor Necrosis Factor-a (TNF-a) has been suspected as the major mediator of the immune-based lung injury following infection with SARS coronavirus [12]. Thus, if TNF-a can be inhibited, it can potentially reduce the lung damage which is actually the major cause of the mortality. On the other hand, multidrug resistant bacterial strains have emerged due to the misuse, use or overuse of antibiotics and this creates a global therapeutic challenge. On August 25, 2016, a strain of Klebsiella pneumoniae was found to be resistant to all 26 antibiotics which include aminoglycosides and polymyxins tested at an acute care hospital in the Washoe County Health District in Reno [13]. The emergence of multi drug resistant bacterial strains underlines the necessity of potent treatment for drug resistant bacteria. Thus, antibodies may represent as one of the potential and promising futuristic alternative to the commercial drug therapies for the treatment of challenging infectious diseases. Serum therapy was successfully developed and first used for the treatment of bacterial infections in human in the 1890s [14-16]. But serum therapy was partly abandoned with the emergence of antibody because of toxicities and difficulty in purification and production of antibodies to single determinants at that time [14]. But, gradually with the advancement of technology, high Specificity of Monoclonal Antibodies (mAbs) is responsible for remarkable developments in the field of therapeutics, diagnostics and research till date [17]. But, monoclonal antibodies like Adalimumab, infliximab, rituximab etc. have the major disadvantages of high cost, difficulties in production and low tissue penetration [18,19]. This has led to the shift in attention to the production of small fragments which are more specific. Due to the gradual improvement in recombinant DNA technology, genetic manipulation has been facilitated [20,21]. The cost effective alternative is therapeutics with antibody fragments which has led to the emergence of second and third generation of antibody therapy, offering innovative opportunities in biopharmacy and therapeutic world.

Classic Drug Development

Conventional drugs that are used for therapeutic purposes are synthesized by chemical reactions between different organic or inorganic compounds. These are small active molecules processed into ingestible tablets/capsules after dissolution of which in the gastrointestinal tract, the Active Product Ingredient (API) is absorbed in the bloodstream through the intestinal wall [22]. In Biologics, Biopharmaceuticals refer to the drugs based on therapeutic proteins that bind to specific cell receptors associated with the anomaly [23]. But in case of conventional drug therapy, drugs also attack body’s own cells, besides the foreign substance [24]. Since these drugs are very small in size and many molecular components are present inside the cell, it is difficult for the new small drug to block only problematic processes leading to nonspecific interaction [24]. This results in serious side effects due to off target interactions. Not only that, it takes a lot of time for the development of traditional drugs [25]. Moreover, due to the emergence of multidrug resistant as well as novel pathogens, the antimicrobial conventional drugs have become less effective and it is difficult to implement the anti-infective therapy successfully. Again, it is also difficult to treat infections in immunocompromised patients [26].

Emergence of Antibody Therapy

Antibodies are the glycoproteins and antigen binding proteins present on the B cell membrane and secreted by plasma cells, that recognize the foreign invading molecules. Each of them can recognize and bind a target molecule with the help of its antigen-binding site, paratope (located on the two Fab segments) specific to a particular epitope on an antigen [27]. Thus antigens act as powerful defense system protecting the body against foreign non-self-agents [27]. Moreover, in contrast to conventional drugs, antibodies have low toxicity, high specificity and comparatively need short term timescale for development [28]. Thus, antibodies can act as futuristic alternative to the commercial drug therapies for the treatment of infectious diseases such as novel viruses and multidrug resistant bacteria. Over time, with the development of technology and science, recombinant technology has been explored through somatic recombination and hypermutagenesis of sets of variant genes to give rise to diversity [27,29]. In the early 1890s, the concept of serum therapy was first developed by Behring and Kitasato and passive antibodies were transferred to combat against bacterial toxins [16]. By 1930s, passive antibody administration was being widely used for the treatment of individuals infected with bacteria, fungi and viruses [16]. After the introduction of Hybridoma technology [30], monoclonal antibodies are produced in remarkable quality and enormous quantity in the laboratory that are preferable as they can specifically target a certain antigen. But initially, these were exclusively murine in origin, so after introducing to human, Human Anti Murine Antibody (HAMA) were created [31,32]. Moreover, production technology is laborious and time consuming [27]. Also, high affinity antibody response to particular antigen cannot be provided by mammals like mice [33]. Due to these limitations, several research groups have tried to investigate the use of phage display for production of recombinant antibodies [27]. The recombinant antibody technology was first utilized in 1984 [34,35] in the bacteria but improper folding and polypeptide aggregation in the cytoplasm of the bacteria were the major difficulties for production of recombinant antibodies [20,27,36]. To overcome this, Skerra and Pluckthun in 1988 [37] started a technology where only parts of antibody molecule (Fab or Fv fragments) were used for expression. Various types of vectors were introduced for E. coli expression of antibody fragments, which could directly secrete the proteins into periplasmic space [27,37,38]. This offers an advantage with reduced size retaining the intact antigen binding site [27].

Antibody Fragments-Minimized Antibodies

IgG can be cleaved, by papain into two identical Fab fragments of 45KDa, or by pepsin to form a F(ab’)2 with 100KDa [39] (Figure 1). Later with the advancement in technology, mAbs are further reduced to scFvs, monovalent Fabs, diabodies, minibodies [40,41]. There are several advantages of minimized antibodies- rapid blood clearance, reduced immunogenicity, lower retention time in nontarget tissue, access to cryptic epitopes facilitating tumor penetration [27,42,43], large scale production using microbial expression system, rapid growth facilitating higher yield and lower production cost [43,44]. The advancement of the latest technology and molecular cloning lead to the generation of genetically engineered recombinant antibodies [45-47] such as fragment antigen binding (Fab) [48], the Fragment Crystallizable (Fc) domain, Fragment Variable (Fv) in which V domains are connected by non-covalent forces [37], the single chain variable fragment in which VH and VL genes are joined together with short peptide linker [49,50], bi-scFv where VH and VL are region joined through disulphide bridge by the introduction of cysteine residues [51], single domain antibodies etc. Peptide linkers of bigger than 12 residues provide sufficient spatial flexibility for VH and VL domains to associate as an independent scFv monomer. Two separate scFv molecules are required for complementary VH/ VL pairs to associate and form a bivalent dimer, termed as a diabody [52,53]. Increase in avidity takes place when Fab or scFv molecules are complexed to form diabodies or triabodies [40]. There have been many attempts to conjugate Fab or scFv molecules into diabodies and triabodies to produce high avidity, which are capable of rapid tissue penetration without fast renal clearance [41]. In clinical trials, 30 percent of Biopharmaceuticals are recombinant antibodies [54]. Gradually with the emergence of new technologies, antibodies are reduced in size, valency is increased for higher affinity to form bivalent [55] and multivalent molecules [56,57], and also antibody fragments with different specificities are linked to form bispecific [40], multi-specific, multimeric, or multifunctional molecules [43,58]. Different antibody fragments and their classification is depicted in Scheme 1.