Antibody therapies for the prevention and treatment of viral infections

The recent and still ongoing pandemic of Covid-19 shook the world in ways unimaginable. Labs worldwide were urged to find therapies to prevent and treat this deadly viral infection. Today one often hears the word ‘antibodies’ mentioned during this disease’s treatment and recovery phase.

But,

• What are antibodies?
• What are the antibody therapies?
• What purpose do they serve in preventing, treating, and curing viral diseases?

In this article, HHC summarises all you need to know about antibodies by answering these vital questions and highlighting their importance in preventing and treating viral infections.

What are antibodies?

In simple terms, antibodies comprise host proteins in serum that work as the first immune response to infections or viral pathogens. These proteins, produced by the immune system, fortify the human body’s defence mechanism, and combat bacterial, viral diseases, or antigens (originating from within the body or foreign, whether they be carbohydrates, proteins, nucleic acids, or lipids) and obstruct them from affecting human cells.

When encountered with a viral or bacterial infection, the immune system produces antibodies to fight the infection. For certain diseases, such as SARS-CoV-2 or Covid-19, vaccinations enable the immune system to imbibe the creation of antibodies. Antibodies provide a certain amount of protection from a disease once the host produces them.

In case of repeated or eventual infection, host antibodies can prevent serious illness as the host immune system now knows how to combat the disease. That said, it is difficult to state the duration and the extent to which antibodies can protect against the disease without considering the host profile, the condition, and other factors.

What are antibody therapies?

Because antibodies can bind an antigen with great affinity and accuracy, they are used in many scientific and medical fields. They are ubiquitously used in therapy as research and diagnostic reagents and have proved crucial, over decades, in the identification and detection of target proteins in several clinical functions. In addition to mediating or controlling physiological responses, they are utilised for analysis, purification, and enrichment in the treatment of diseases and health improvement.

Given their positive impact on the next-gen therapeutic applications, today, antibodies can be developed by scientists artificially in labs which are called ‘antibody therapies’. These synthetic proteins act like natural antibodies, replicating and improving the human body’s innate immune response.

The anatomy of antibodies

Antibodies constitute Y-shaped immunoglobulin molecules (Ig), produced by B lymphocytes or plasma cells that activate the primary response of the adaptive immune system when a foreign molecule is detected. The Y-shaped structure constitutes two identical heavy and light chains which contain multiple constant (C) and one variable (V) regions connected by disulphide bonds. In the structure of the Y-shaped immunoglobulin molecules, the antigen-binding domains are at the tip of the two arms (Fab), while the effector domains are situated in the tail (Fc).

According to the Ig class, a given antibody may consist of up to five structural molecules. The Ig class determines the type and the timing of the immune response. There are three classes of Ig in avians (IgY, IgM, and IgA) and five classes of Ig in mammals (IgG, IgM, IgA, IgD, and IgE). In some mammals, due to variations in the conserved areas of the heavy chain, IgG and IgA are further divided into subclasses, also called isotypes. IgG or gamma globulins is the most common isotope of antibodies used in research.

Based on the expected research outcomes, scientists can develop two antibody therapies: Polyclonal antibodies (PAbs) and Monoclonal antibodies (MAbs).

Let’s understand what these two therapies consist of and why they are essential in studying and preventing viral pathogens.

What are monoclonal antibodies (MAbs)?

Once an antibody is developed to detect and target specific pathogens, scientists can replicate or clone the antibody in a lab. Antibodies thus created are called monoclonal antibodies. Monoclonal antibodies (MAbs) are produced by cloning a single B lymphocyte and comprise a single IgG that binds to one epitope (the region of an antigen where an antibody binds). Monospecific antibodies are obtained from identical immune cells and clone a single parent cell.

What are polyclonal antibodies (PAbs)?

Polyclonal antibodies result from a combination of different antibodies produced by various B lymphocyte lineages. PAbs are a collection of IgG molecules that bind to different epitopes on a target antigen. A polyclonal antibody response is effective given the complexity of antigens with multiple epitopes identified by many lymphocytes. The process entails the activation of each lymphocyte, leading to their proliferation and differentiation into plasma cells.

Polyclonal antibodies vs Monoclonal antibodies

Whether to utilise a PAb or MAb depends on several variables, the most crucial of which are the antibody’s intended purpose and whether it is easily accessible from researchers or commercial providers.

Below we understand the advantages and disadvantages of each of the antibody preparations.

Principally, when compared with MAbs, PAbs can be produced

• relatively faster,
• at lower costs
• with less technical expertise than is necessary to create MAbs and
• with higher binding affinity against antigens as they detect several epitopes on the target antigen molecule.

While the production of MAbs often takes a year and sometimes even longer, PAbs can be generated several months after commencing vaccination. MAbs require, therefore, more time and expense for their production. PAbs, on the other hand, become easier to procure off-the-shelf therapeutic reagents.

In reactivity, polyclonal antibodies are more sensitive and can identify low-quantity proteins. They have a high potential in capturing target protein in immunoassays such as sandwich ELISA and have high-affinity outcomes due to rapid binding to target antigens in assays like IP or ChIP. 

PAbs are easy to combine with antibody labels, do not impact binding efficiency, and are more likely to identify a native protein. In terms of specificity, PAbs are better than MAbs as they are secreted by many B lymphocyte clones, each generating antibodies to a particular epitope. A collection of antibodies with distinct specificities makes up polyclonal sera. However, MAbs are monospecific antibodies and show greater levels of purity and strength.

Despite the advantages, PAbs are not as viable commercially for the following reasons.

• PAbs are produced at different times in different animals, and so each batch may vary from the other.
• A polyclonal antibody response may lead to cross-reactivity as multiple epitopes are identified.

One of the most important advantages of MAbs is that they are

• consistent,
• homogenous, and
• instrumental in analysing the modifications in protein-protein interactions, phosphorylation states, and molecular shape, as well as for recognising members of a particular protein family.

Because they are monospecific, monobodies also enable the possibility of investigating the molecular structure of the antibody. In contrast to PAbs, MAbs are easier to obtain consistently once the required hybridoma has been generated. Their homogenous nature and binding specificity provide for detecting a specific epitope, reducing the likelihood of a cross-reaction with proteins other than the targeted one.

It is worth noting that despite being superior to PAbs in many ways, the utility of MAbs is limited due to their monospecificity. While monobodies can be affected significantly by minor changes in an epitope’s structure, polyclonal antibodies, being heterogeneous and able to target a host of epitopes, are unlikely to be impacted by such modifications.

Recombinant monoclonal antibodies

Recombinant antibodies are the latest technology in the production of monoclonal antibody therapies. They are the future monoclonal antibody therapies obtained by in vitro cloning of heavy and light chain DNA sequences of the antibody from the immunised B plasma cells of animals. This antibody manufacturing process entails the generation of MAbs by introducing the recombinant vectors into expression hosts such as E. coli and not from hybridomas, as done in the classic technique.

Over the last two decades, the production of recombinant monoclonal antibodies for therapeutic applications has grown exponentially. Scientists have developed numerous recombinant monoclonal antibodies to target and fight against infectious diseases and human viral proteins such as Ebola and Covid-19 that represent increased potential health risks.

MAb therapies have proved significant in the treatment and prevention of a growing number of diseases, such as:

• autoimmune diseases (Crohn’s disease)
• metabolic diseases (asthma and rheumatoid arthritis),
• cancers (bladder cancer)
• respiratory syncytial virus
• Clostridioides difficile and
• Anthrax

In recent years, many monoclonal antibodies have been investigated in clinical trials or under regulatory assessment to determine whether they have the potential to prevent or treat a variety of illnesses and viral infections such as Covid-19. People with specific ailments, such as malignancies and autoimmune diseases, may be more susceptible to infectious diseases because of these underlying illnesses, immune-suppressing drugs, or age.

In this situation, monoclonal antibody therapies may be used to treat patients with an underlying condition and lower their risk of developing a serious illness requiring hospitalisation or death. They may also be used to treat patients who are at risk of infection or more likely to develop a disease.

To further and fortify the constant human endeavour against infectious human pathogens and viruses, Helvetica Health Care (HHC) offers a comprehensive range of monoclonal and polyclonal antibodies. These antibodies, created with the help of the latest manufacturing techniques and expertise, are directed against particular human viral proteins and are highly specific in immunoassays. Our range of MONOBODIES™ can be used in different applications, including ELISA, immunoblotting and immunochemistry.

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