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What is the attacking mechanism of RF on IgG?

What is the attacking mechanism of RF on IgG?


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Rheumatoid Factor (RF) attacks Fc portion of Immunoglobulin G (IgG), I want to know the underlying mechanism at molecular level. Also, what type of bond or attachment is made by RF and Fc portion of IgG?

// I'm a student of mathematical physics and have no detailed knowledge in biology, this question comes in my mind because my sister is suffering from Rheumatoid arthritis. All I want is to understand this disease from physical aspects//


RF factors comprise antibodies that your body makes that exhibit auto-immunity (recognition of self as an antigen). They often recognize and bind to IgG antibodies as illustrated in this picture:

So the answer to your first question is that the underlying mechanism is inappropriate recognition of self from your immune system.

For your second question, I am not an expert in the type of chemical bonds employed by antibody-antigen interactions, so I looked it up briefly. This article was quite informative for that: Antibody/Antigen Complexes. The majority of binding seems to be hydrogen and ionic binding.

Hope that gets you going in your own searches.


Antibody-dependent cellular cytotoxicity

Antibody-dependent cellular cytotoxicity (ADCC), also referred to as antibody-dependent cell-mediated cytotoxicity, is a mechanism of cell-mediated immune defense whereby an effector cell of the immune system actively lyses a target cell, whose membrane-surface antigens have been bound by specific antibodies. [1] It is one of the mechanisms through which antibodies, as part of the humoral immune response, can act to limit and contain infection. [2]

ADCC is independent of the immune complement system that also lyses targets but does not require any other cell. ADCC requires an effector cell which classically is known to be natural killer (NK) cells that typically interact with immunoglobulin G (IgG) antibodies. [3] However, macrophages, neutrophils and eosinophils can also mediate ADCC, such as eosinophils killing certain parasitic worms known as helminths via IgE antibodies. [4]

In general, ADCC has typically been described as the immune response to antibody-coated cells leading ultimately to the lysing of the infected or non-host cell. In recent literature, its importance in regards to treatment of cancerous cells and deeper insight into its deceptively complex pathways have been topics of increasing interest to medical researchers.


General Concepts of Immunity

Nima Rezaei , . Hamid-Reza Mohammadi-Motlagh , in Reference Module in Biomedical Sciences , 2021

Antibody-dependent cell cytotoxicity (ADCC): An extracellular killing mechanism

ADCC could be considered as an extracellular killing mechanism resulting in pathogen elimination. This process requires: (1) immune cells expressing Fc receptor on their surface, and (2) target antigen coated by antibody ( Fig. 1 ). Immunoglobulin G (IgG) and its receptor named FcγRIII (CD16) play an important role in ADCC activation. NK cells which express high levels of CD16 are regarded as the key players in this process. However, in addition to NK cells, macrophages, neutrophils, and eosinophils are able to mediating ADCC ( Hubert et al., 2011 Siders et al., 2010 Valerius et al., 1990 ).

IgG possess a bifunctional structure which is related to the fragment antigen-binding (Fab) and Fc portions of antibody. ADCC is initiated by the engagement of Fab and Fc regions of antibodies with the pathogen and FcγR on effector cells, respectively. Subsequently, degranulation of effector cells (mainly NK cell) leading to pathogen lysis ( Nigro et al., 2019 ).


Disease Initiation

The search for an elusive single trigger for RA has been ongoing for many years. Multiple studies have failed to conclusively demonstrate that any organism or exposure is singly responsible for the disease. However, a number of well done epidemiological studies and genetic studies have provided valuable information to inform our genera, albeit still incomplete, understanding of the dynamic process of disease initiation.

Genetic Susceptibilities

In the early 1980’s an association was described for the association of RA with class II major histocompatability (MHC) antigens, specifically the shared epitope found in HLA-DR4. Class II MHC on the surface of an antigen presenting cell interacts with a T cell receptor in the context of a specific antigen, usually a small peptide sequence from a protein. A sequence of amino acid residues with highly conserved sequence and charge characteristics within the hypervariable region of HLA-DR4 remains the largest genetic risk factor described for RA, estimated to contribute approximately 30% of the genetic risk for the disease. It is hypothesized that a triggering peptide (or peptides) with a tight conformational fit for the pocket formed by these residues is an early event leading to the activation of T lymphocytes. More recently, it has been found that modified citrullinated peptides may have significant binding specificity for shared epitope alleles, with some data now suggesting that citrullinated sequences from different proteins are associated with allelic restriction. (A more detailed discussion of citrullination is below).

Other genetic susceptibilities have been described in RA, but their relative contributions to the disease are still not well defined. These include peptidyl arginine deiminase-4 (PAD-4) which may lead to increased citrullination, PTNP22, STAT4, and CTLA4 which may be involved in T cell activation, TNF receptors, and others.

That RA has a genetic component is also borne out through a number of studies of monozygotic (from the same embryo, thus nearly identical DNA) and dizygotic (from different embryos) twins. In these studies the concordance rates between twins was higher in monozygotic twins ranging from 15-35% compared with dizygotic twins in which the concordance was in the 5% range. Even the dizygotic RA prevalence was higher than the general population estimates of approximately 1%. It is important to emphasize however that even in twins with nearly identical DNA, there was far from perfect correlation of the development of RA, implicating many other factors related to the development of disease than genetic factors.

Triggers of Disease

The fact that there is not perfect genetic concordance implicates other factors in disease development. A search for these elusive triggers has been largely unrevealing. A number of well performed studies have demonstrated that cigarette smoking is a significant risk factor for the development of disease and also with disease severity. Interestingly this relationship is especially strong in individuals who carry the shared epitope, and even more in patients who have RA autoantibodies.

The search for bacterial or viral infections as causes of RA have often been hypothesized, and many patients will relate the onset of their symptoms to an antecedent infection however, the recovery of organisms or their DNA from blood or joint tissue have been unfruitful in discovering “the” elusive infection responsible for RA. Nonetheless, the ability of an infection to activate a number of immunological and inflammatory pathways may “prime the pump” in combination with other factors.

Perhaps the most exciting developments in the last few years in terms of RA initiation has been the growing research to evaluate the possible role of oral bacteria as a trigger for RA. There has been a longstanding association described between periodontal disease with RA, however cause and effect has been far from proven. Periodontal disease is characterized by significant inflammation of the gums that leads to bone destruction and collagen matrix destruction. Both are inflammatory diseases with many of the same mediators and pathways involved, thus this could simply be an association between two inflammatory processes. However, it is now recognized that a specific species of bacteria, Porphyromonas gingivalis, which colonizes patients with periodontal disease and marks the progression from gingivitis to more aggressive periodontitis has an enzyme that can cause citrullination of proteins. With the growing recognition that protein citrullination is an early event leading to an immune response against these in RA, these data suggest that periodontal infection may precede the development of RA in some patients serving as a disease initiation factor. A number of groups worldwide, including our own, are now investigating these pathways to better understand these processes.

Citrullination

The recognition of antibodies directed against citrullinated peptides in RA has been a major development to improve disease identification and provide prognostic information. Citrulline is a post-translational modification that occurs on arginine residues contained within proteins and peptides. There are a number of enzymes that can cause citrullination to occur, present in various cell types and tissues known as peptidylarginine deiminases (PADs). Citrullination is a normal process, required for normal skin formation and other physiologic functions. However, in rheumatoid arthritis an autoimmune response develops against citrullinated peptides detected as anti-citrullinated peptide antibodies (ACPA). One of tests to detect these antibodies detects anti-cyclic citrullinated peptides (anti-CCP), currently the most commonly used diagnostic test for them. The presence of anti-CCP are >98% specific for the diagnosis of rheumatoid arthritis however, not all patients with RA will develop anti-CCP antibodies.

Of significant importance is the recognition that these anti-CCP antibodies may be detected up to 15 years before the onset of clinical symptoms of RA indicating a preclinical phase of disease in which immunologic activation is already ongoing. Moreover, it has recently been demonstrated that specific citrullinated peptide sequences bind to shared epitope alleles with high affinity and can lead to T cell activation.

The mechanisms to citrullination that lead to RA remain unclear. A polymorphism in the PAD4 gene which may lead to increased citrullination has been described populations. In RA patients, autoantibody responses also develop against the PAD4 protein, associated with a more aggressive disease course. One species of oral bacteria Porphyromonas gingivalis has a PAD enzyme. Given the relationships described with periodontal disease and RA, it has been hypothesized that this bacteria may also serve to initiate citrullination in the preclinical phases of RA.


Antigen-antibody reaction

Cause of

…effects are the result of antibody-antigen responses (i.e., they are the products of B-cell stimulation). These can be divided into three basic types.

…anaphylaxis is mediated primarily by antibodies—specifically those of the immunoglobulin E (IgE) class. These antibodies recognize the offending antigen and bind to it. The IgE antibodies also bind to specialized receptor molecules on mast cells and basophils, causing these cells to release their stores of inflammatory chemicals such as histamine,

…the result of an aberrant immune system.

…carry the Rh factor (an antigen in this context) cross the placental barrier and enter the mother’s bloodstream. They stimulate the production of antibodies, some of which pass across the placenta into fetal circulation and lyse, or break apart, the red blood cells of the fetus (hemolysis).

…of complement in response to antigen-antibody (immune) complexes that are deposited in tissues. The classes of antibody involved are the same ones that participate in type II reactions—IgG and IgM—but the mechanism by which tissue damage is brought about is different. The antigen to which the antibody binds is not…

Antigen-antibody complexes form only after the nuclear contents of a cell are released into the bloodstream during the normal course of cell death or as a result of inflammation. The resultant immune complexes are deposited in tissues, causing injury. Certain organs are more commonly involved…

…components of the streptococci (antigens) whose structure resembles that of molecules found in human tissue (“self antigens”). Because of this resemblance, the antibodies that recognize streptococcal antigens may mistakenly react with similarly shaped antigens of certain cells of the body—such as those of the heart. By binding to these…

…would any foreign invader, forming antigen-antibody complexes that lodge in the blood vessel walls. Complement, a series of blood proteins, is then activated, causing inflammation. Serum sickness develops within two weeks of serum injection and usually lasts only a few days. Its severity depends on both the amount of serum…

Response to

An antigen that induces an immune response—i.e., stimulates the lymphocytes to produce antibody or to attack the antigen directly—is called an immunogen.

A significant feature of antigen-antibody reactions is specificity the antibodies formed as a result of inoculating an animal with one microbe will not react with the antibodies formed by inoculation with a different microbe. Antibodies appear in the blood serum of animals, and laboratory tests of antigen-antibody reactions are…

To be antigenic, a substance is usually both relatively large and foreign to the body. Large proteins are often strong antigens. Smaller chemicals can become antigenic by combining with proteins in chemicals called haptens.

…animals mount two kinds of immune response, humoral and cellular. In humoral immunity, B lymphocytes, usually triggered by helper T lymphocytes, make antibodies (proteins that recognize and bind foreign molecules) to the viral protein. The antibody synthesized as a result of the immune response against a specific viral antigen

Work of

…to be his investigations into antigen-antibody interactions, which he carried out primarily at Rockefeller Institute (now called Rockefeller University) in New York City (1922–43). In this research Landsteiner used small organic molecules called haptens—which stimulate antibody production only when combined with a larger molecule, such as protein—to demonstrate how small…

…many important discoveries about the immune response. Perhaps his most notable achievement was his recognition that the phagocyte is the first line of defense against acute infection in most animals, including humans, whose phagocytes are one type of leukocyte, or white blood cell. This work formed the basis of Metchnikoff’s…

…term allergy to describe these antibody-antigen reactions.

…the first evidence that an immune response could cause damage as well as provide protection against disease. During his career Richet helped to elucidate problems of hay fever, asthma, and other allergic reactions to foreign substances and explained some cases of toxicity and sudden death not previously understood.


Resisting Adaptive Immune Defenses

Bacteria utilize a variety of mechanisms to resist antibodies made during adaptive immunity. These include the following:

a. Certain bacteria can evade antibodies is by changing the adhesive tips of their pili as mentioned above with Escherichia coli and Neisseria gonorrhoeae (Figure (PageIndex<4>)).

Figure (PageIndex<4>): Bacteria Altering the Adhesive Tips of Their Pili. By genetically altering the adhesive tips of their pili, certain bacteria are able to: 1) adhere to and colonize different cell types with different receptors, and 2) evade antibodies made against the previous pili.

Bacteria can also vary other surface proteins so that antibodies previously made against those proteins will no longer "fit." ( Figure (PageIndex<5>)). For example, N. gonorrhoeae produces Rmp protein (protein III) that protects against antibody attack by antibodies made against other surface proteins (such as adhesins) and the lipooligosaccharide (LOS) of the bacterium.

Figure (PageIndex<5>): (A) Normal Antibody-Antigen Reaction. The Fab portion of the antibody has specificity for binding an epitope of an antigen. An epitope is the portion of an antigen - such as a few amino acids sticking out of a protein - to which the Fab portion of an antibody molecule fits. The Fc portion of an antibody directs the biological activity of the antibody. In the case of IgG, the Fc portion can bind to phagocytes for enhanced attachment (opsonization) as well as activate the classical complement pathway. (B) Altering Epitopes of an Antigen in order to Resist Antibody Molecules. The Fab portion of the antibody has specificity for binding an epitope of an antigen. By altering the molecular shape of an epitope of an antigen through mutation or genetic recombination, previous antibody molecules agains the original shaped epitope no longer fit or bind to the antigen.

b. Strains of Neisseria meningitidis have a capsule composed of sialic acid while strains of Streptococcus pyogenes (group A beta streptococci) have a capsule made of hyaluronic acid. Both of these polysaccharides closely resemble carbohydrates found in human tissue and because they are not recognized as foreign by the lymphocytes that carry out the adaptive immune responses, antibodies are not made against those capsules. Likewise, some bacteria are able to coat themselves with host proteins such as fibronectin , lactoferrin , or transferrin and in this way avoid having antibodies being made against them because they are unable to be recognized as foreign by lymphocytes.

c. Staphylococcus aureus produces protein A while Streptococcus pyogenes produces protein G. Both of these proteins bind to the Fc portion of the antibody IgG, the portion that is supposed to bind the bacterium to phagocytes during enhanced attachment (Figure (PageIndex<1>)). The bacteria become coated with antibodies in a way that does not result in opsonization (Figure (PageIndex<6>)).

Figure (PageIndex<6>): Staphylococcus aureus Resisting Opsonization via Protein A. The Fc portion of the antibody IgG, the portion that would normally binds to Fc receptors on phagocytes, instead binds to protein A on Staphylococcus aureus. In this way the bacterium becomes coated with a protective coat of antibodies that do not allow for opsonization.

d. Salmonella species can undergo phase variation of their capsular (K) and flagellar (H) antigens, that is, they can change the molecular shape of their capsular and flagellar antigens so that antibodies made against the previous form no longer fit the new form ( Figure (PageIndex<5>)).

e. Bacteria such as Haemophilus influenzae, Streptococcus pneumoniae, Helicobacter pylori, Shigella flexneri, Neisseria meningitidis, Neisseria gonorrhoeae and enteropathogenic E. coli produce immunoglobulin proteases. Immunoglobulin proteases degrade the body's protective antibodies (immunoglobulins) that are found in body secretions, a class of antibodies known as IgA.

f. Many pathogenic bacteria, as well as normal flora, form complex bacterial communities as biofilms. Bacteria in biofilms are often able to communicate with one another by a process called quorum sensing (discussed later in this unit) and are able to interact with and adapt to their environment as a population of bacteria rather than as individual bacteria. By living as a community of bacteria as a biofilm, these bacteria are better able to resist attack by antibiotics and are better able to resist the host immune system.


Novel 2019 coronavirus structure, mechanism of action, antiviral drug promises and rule out against its treatment

In the past two decades, the world has faced several infectious disease outbreaks. Ebola, Influenza A (H1N1), SARS, MERS, and Zika virus have had a massive global impact in terms of economic disruption, the strain on local and global public health. Most recently, the global outbreak of novel coronavirus 2019 (SARS-CoV-2) that causes COVID-19 is a newly discovered virus from the coronavirus family in Wuhan city, China, known to be a great threat to the public health systems. As of 15 April 2020, The Johns Hopkins University estimated that the COVID-19 affected more than two million people, resulting in a death toll above 130,000 around the world. Infected people in Europe and America correspond about 40% and 30% of the total reported cases respectively. At this moment only few Asian countries have controlled the disease, but a second wave of new infections is expected. Predicting inhibitor and target to the COVID-19 is an urgent need to protect human from the disease. Therefore, a protocol to identify anti-COVID-19 candidate based on computer-aided drug design is urgently needed. Thousands of compounds including approved drugs and drugs in the clinical trial are available in the literature. In practice, experimental techniques can measure the time and space average properties but they cannot be captured the structural variation of the COVID-19 during the interaction of inhibitor. Computer simulation is particularly suitable to complement experiments to elucidate conformational changes at the molecular level which are related to inhibition process of the COVID-19. Therefore, computational simulation is essential tool to elucidate the phenomenon. The structure-based virtual screening computational approach will be used to filter the best drugs from the literature, the investigate the structural variation of COVID-19 with the interaction of the best inhibitor is a fundamental step to design new drugs and vaccines which can combat the coronavirus. This mini-review will address novel coronavirus structure, mechanism of action, and trial test of antiviral drugs in the lab and patients with COVID-19.

Keywords: ACE2 receptor COVID-19 Coronavirus antiviral drugs computational simulation coronavirus Spike.

Figures

The schematic diagram of the…

The schematic diagram of the mechanism of COVID-19 entry and viral replication and…

Three-dimensional structure of COVID-19 M…

Three-dimensional structure of COVID-19 M pro (Jin et al., 2020).

Cartoon representation of COVID-19 M…

Cartoon representation of COVID-19 M pro with Antiviral inhibitors, Lopinar and N3 highlighted…


Reader Interactions

Comments

Is there a good understanding of what different parts of the immune response the inactivated vs. live attenuated vaccines trigger? It seems like the attenuated virus should produce a CTL response (so I end up with a fair population of CTLs ready to clear infected cells when they start showing flu peptides on their MHC1 molecules). Is that right, or does whatever is done to attenuate the virus keep it from producing that kind of response?

I'm wondering if this might become important, if most people get the inactivated vaccine. That should cause some selection of the flu virus to mutate the bits that stick out of the envelope of the virus (the H and the N), so that the antibodies can't stick to it. But the CTL response (as well as the Th1 response, I think) might not be selected against so strongly.

I'm puzzled trying to reconcile two statements.

1. Viruses cannot be killed because they were never alive, and
2. The Sabin polio vaccine is a “live, attenuated vaccine”.

Also, I'm puzzled by this ostensibly counterproductive relationship (on occasion) between non-neutralizing antibodies and viruses when you state that occasionally these particular antibodies may actually ENHANCE infectivity.

Does this mean that some of these non-neutralizing antibodies have the characteristics of “bad actors”?

Do virus populations ever take advantage of this occasional infectivity quotient amplification by such non-neutralizing antibodies?

Clearly the statement 'live, attenuated vaccine' is incorrect.
Unfortunately I am guilty of using that phrase for years, but it's
wrong. It's ensconced in the literature and will be difficult to
purge. It should read 'infectious, attenuated vaccine'. Recently I
read an article entitled 'Live Marburg virus isolated from bats' and I
made a point to tell the writer that it should be 'infectious'. As for
antibodies enhancing infectivity on occasion – not all antibodies made
against a virion are able to block infectivity. The antibodies may
bind to the virus, but they do not inhibit infection. Such antibodies
can lead to enhancement of infectivity, because the antibody – via the
Fc portion – can bind to receptors on cells not normally infected by
the virus. The virus-antibody complex is taken up into cells, and
infection proceeds.

I didn't answer the last part of your question – do viruses 'use' this
method of entering cells. We think so, but we are not sure. Dengue
virus may be one that enters cells via antibody-mediated uptake.

This is a very good question – but the answer is long and deserves a
post of its own. CTLs are generally involved in clearing, not
preventing infections. But the kinds of T cells that are produced do
vary among different types of vaccines. I promise I'll cover this in a
subsequent post. As for escape – T cell epitopes are also short and
known to change so as to avoid CTL killling.

Thanks for the clarification on “live, attenuated virus” that I, as an informed lay person, have encountered on several occasions. That phrasing had led me to wonder if there was a controversy about whether viruses were alive. Clearly there is no controversy.

Interesting about viruses possibly taking advantage of infectivity enhancing characteristics of selected antibodies. I often find the most fascinating stories in evolutionary biologies to be those discussing the co-evolution of two or more symbiotic organisms, as Lynn Margulis (originator of the notion that the distinct DNA in mitochondria is evidence of cells being a product of co-evolution) as she describes in “Acquiring Genomes: A Theory of the Origin of Species”.

It would seem to be an interesting pathway for viral evolution. Sets of viruses may be evolving to directly enter the cell, while other sets may be evolving towards getting their “foot in the door” via alternate pathways such as this. Fascinating stuff, to me at least!

Is it possible to know how many antibodies are needed to neutralize a virus?
Thanks

It's an interesting question that has been studied theoretically and
experimentally. Intuitively it would seem that occupation of all
attachment sites with antibodies would be needed to block attachment.
However, for influenza virus, as few as 1-2 antibodies per virion have
been shown to be sufficient to neutralize influenza virus. The
assumption is that few antibodies can cause conformational changes in
the envelope which blocks attachment. Alternatively, such antibodies
might act catalytically and block fusion.

Dear Prof. Racaniello,
Thank you very much for your responses (very accurate and to the point). I am an influenza fan. I have also been doing some research on influenza for the past year, and I become more and more interested on the topic as I learn more about it. I read an article on Science this week about cross-protection between neutralizing Abs against 1918 HA and 2009 HA. I have always wondered if a 'multi-valent' vaccine (including multiple HAs, more than 3) would be more efficacious to generate a more protective response against new viral HAs. Has any lab tried this before? Is this a real possibility?
Many thanks.

Multivalent doesn't help, because the virus drifts each year
antigenically, and the direction can't be predicted. What is needed is
a cross-protective vaccine, which has not been developed. There have
been some inroads and you can read about them on this blog, for
example: https://www.virology.ws/2009/02/25/influenza-vac….

Dear Prof. Racaniello,
Thank you very much for your responses (very accurate and to the point). I am an influenza fan. I have also been doing some research on influenza for the past year, and I become more and more interested on the topic as I learn more about it. I read an article on Science this week about cross-protection between neutralizing Abs against 1918 HA and 2009 HA. I have always wondered if a 'multi-valent' vaccine (including multiple HAs, more than 3) would be more efficacious to generate a more protective response against new viral HAs. Has any lab tried this before? Is this a real possibility?
Many thanks.


Diagnosing Rheumatoid Arthritis with Anti-CCP Test

In order to reach a rheumatoid arthritis diagnosis when a patient tests positive for anti-CCPs, several other criteria must be met. Doctors will perform a physical examination to look for clear clinical symptoms of rheumatoid arthritis.

Other blood tests are also performed in conjunction with the anti-CCP test, including testing for rheumatoid factor (RF) antibodies and increased inflammation levels. Doctors will also use imaging scans to observe any signs of bone and cartilage deterioration around the affected joints.

The anti-CCP test is thought to be slightly more specific than RF for diagnosing rheumatoid arthritis. The reason for this is RF is present in patients without rheumatoid arthritis who have other autoimmune disorders.


Treatment of Viral Infections

Sometimes antiviral drugs

Treatment of symptoms

There are no specific treatments for many viruses. However, many things can help relieve certain symptoms, such as the following:

Dehydration: Plenty of fluids, sometimes given by vein (intravenously)

Diarrhea: Sometimes an antidiarrheal drug, such as loperamide

Fever and aches: Acetaminophen or nonsteroidal anti-inflammatory drugs (NSAIDs)

Nausea and vomiting: A clear-liquid diet and sometimes an antiemetic (antinausea) drug, such as ondansetron

Some rashes: Soothing or moisturizing creams and sometimes an antihistamine taken by mouth for itching

A runny nose: Sometimes nasal decongestants, such as phenylephrine or phenylpropanolamine

A sore throat: Sometimes throat-numbing lozenges containing benzocaine or dyclonine

Not everyone who has these symptoms needs treatment. If symptoms are mild, it may be better to wait for them to go away on their own. Some treatments may not be appropriate for infants and young children.

Antiviral drugs

Drugs that combat viral infections are called antiviral drugs. There are no effective antiviral drugs for many viral infections. However, there are several drugs for influenza, many drugs for infection by one or more herpesviruses (see Table: Some Antiviral Drugs for Herpesvirus Infections), and many new antiviral drugs for treatment of HIV (see Table: Drugs for HIV Infection) , hepatitis C, hepatitis B, and Ebola.

Many antiviral drugs work by interfering with replication of viruses. Most drugs used to treat HIV infection work this way. Because viruses are tiny and replicate inside cells using the cells' own metabolic functions, there are only a limited number of metabolic functions that antiviral drugs can target. In contrast, bacteria are relatively large organisms, commonly reproduce by themselves outside of cells, and have many metabolic functions that antibacterial drugs (antibiotics) can target. Therefore, antiviral drugs are much more difficult to develop than antibiotics. Also, unlike antibiotics, which are usually effective against many different species of bacteria, most antiviral drugs are usually effective against only one (or a very few) viruses.

Viruses are infectious agents that enter and replicate within healthy cells. In order for the virus to attach, receptors on the virus must bind to receptors on the outside of the healthy cell. This allows the viral membrane to fuse with the cell membrane and release the genetic material used in viral replication.

Once the virus replicates inside the cell, it may remain dormant for long periods of time or be released immediately and attach to other healthy cells to begin the infection process again.

Many diseases are caused by viruses such as the flu, chicken pox, hepatitis, and HIV. While they differ in symptoms such as fever and weakness, some present no symptoms at all.

The potential for recovery depends on the type of virus. Viruses may cause harm and if left untreated potentially death.

Antiviral drugs work by stopping the infection process. Depending on the virus and medicine, the blocking of the process can occur at many different locations. One drug prevents the virus from fusing to the healthy cell by blocking a receptor that helps bind the virus to the cell. By preventing this attachment, the viruses cannot enter or infect the cell.

Sometimes multiple drugs are used to treat a particular infection, so that more than one viral process is disrupted and the chances for the patient’s recovery from the infection are improved.

While some viral infections such as hepatitis or HIV cannot be fully cured, a patient’s state of health can be returned to normal by controlling the virus and preventing further harm to the body.

Always consult a doctor before starting treatment or making any changes to your current therapy.

Antiviral drugs can be toxic to human cells. Also, viruses can develop resistance to antiviral drugs.

Most antiviral drugs can be given by mouth. Some can also be given by injection into a vein (intravenously) or muscle (intramuscularly). Some are applied as ointments, creams, or eye drops or are inhaled as a powder.

Antibiotics are not effective against viral infections, but if a person has a bacterial infection in addition to a viral infection, an antibiotic is often necessary.

Interferon drugs are replicas of naturally occurring substances that slow or stop viral replication. These drugs are used to treat certain viral infections such as


Watch the video: Types of antibody IgA IgD IgE IgG IgM परतरकष क परकर हद म (October 2022).