VIRUSES

A virus is a very simple infective agent consisting of a nucleic acid surrounded by one or more proteins and in some cases an outer membrane envelope.

It is crucial to appreciate the wide range of consequences of this simple form of life on all the other forms of life.

Viruses can only replicate themselves inside cells as they lack ribosomes or enzymes for high-energy phosphate generation, or for carbohydrate, protein or lipid metabolism.

They may have a few, up to several hundred, genes.

Many of these genes are able to inactivate or modulate immune system mechanisms.

Enteroviruses, Coxsackie, hepatitis A, influenza and polioviruses are all RNA viruses.

The recently studies SARS virus is a corona virus.

Hepatitis B and Herpes Family Virus (HSV1 and 2, varicella-zoster, Epstein Barr virus (EBV) and cytomegalo virus (CMV) as well as HHV6 types A and B, HHV7 and 8,) and parvovirus are DNA viruses.

Parvoviruses are the smallest DNA viruses. Some are autonomous, while others are not.

Parvovirus B19 (an autonomous virus) depends upon cellular DNA replication and requires the virus-coded Rep protein.

Dr Jonathon Kerr from London, UK, reports CFS following acute infection with this virus.

Symptomatic B19 infection has been shown to be associated with carriage of HLA DRB1*01, 804 and *07 alleles.

I am currently collecting data on South Australian CFS cases with more detailed HLA haplotyping.

We are looking closely at cytokine dysregulation in cases with the persistent illnesses.

Interestingly, another non autonomous parvovirus, adeno-associated virus (AAV) requires helper viruses of the adenovirus or herpes family for replication, and may be a safe human gene vector because its Rep protein causes its integration at a single chromosomal site.

This should alert us to the interplay in living systems, including one virus affecting another,

Viruses of the lentivirus and retrovirus groups are not purely RNA or DNA viruses as they are enveloped RNA viruses with two identical sense-strand genomes and associated reverse transcriptase and integrase enzymes.

They reverse transcribe themselves into partially duplicated double-strand DNA copies and integrate with the host genome as part of their replication strategy. Human immunodeficiency virus (HIV) does this.

Viruses, which cause similar illnesses, may have different ways or degrees in which they do so.

I want to illustrate this, because too often people (even health practitioners) tend to generalize about viruses.

Hepatitis A virus is a picornavirus. It causes an acute illness, which is usually mild and never progresses to chronic illness.

Hepatitis B virus is a DNA virus, now classified as a hepadenavirus, and its genome codes for four sets of viral products. Each gene and gene products and effects have been measured.

As an example, the x gene codes for a small protein that can transactivate transcription of both viral and host cellular genes.

The host gene which produces interferon g, and the gene which produces class1 MHC molecules are activated by this viral gene activity.

It exists inside and outside the liver in the infected individual, contains its own DNA polymerase, and is associated with acute and chronic hepatitis, and hepatocellular carcinoma.

In the infective phase this virus is found in all bodily fluids.

Also a variety of acute and chronic autoimmune disorders are seen in many cases of hepatitis B.

Hepatitis C virus is distinct, classified as a flavivirus, has at least 6 genotypes and usually a quite insidious course with some 50% of those infected showing low grade hepatitis.

Interestingly, many cases experience ongoing chronic fatigue.

Research in virology has accelerated and we are rapidly reaching sufficient knowledge of all stages of viral activity and replication, to plan management strategies.

This has led to development of a range of antiviral drugs.

Unfortunately these therapies often fail to cure the infected person.

The Government may have restrictions in PBS listing in the indications, such that the drugs are too expensive for most people.

Herpes viruses.

The following viruses are in this family

HHV1 (Herpes simplex virus, HSV1) (classically cold sores and dendritic ulcers of the cornea) (probably present in 60% of most communities)

HHV2 (Herpes simplex type2, HSV2) (usually causes genital herpes)

HHV3 (varicella-zoster), (causes chickenpox and shingles,) (98% of western populations)

These 3 herpes type viruses have a predilection for skin and neural cells.

The other herpes viruses tend to target immune cells (B and T lymphocytes).

HHV4 Epstein Barr virus (EBV) (Causes infectious mononucleosis/glandular fever) (80% of Western populations are infected by young adulthood years.)

This virus infects B-lymphocytes.

HHV5 Cytomegalovirus (CMV)(glandular like fever like illness except in immunocompromised individuals where it causes many serious and even fatal conditions.) (50-75% prevalence in Western populations)

Human CMV encodes more than 200 genes and the function of these genes has been gradually revealed by research.

Some of these genes are able to subvert immune mechanisms. (See below)

HHV6 types A and B, (Infantile roseola is usually caused by the B strain, but both can sometime cause more serious diseases.) HHV6B is probably carried by 100% of people)

HHV6A is unique among herpes viruses in its ability to integrate into host bcell chromosomes, using a viral genome encoded integrase gene.

There is evidence that the HHV6A strain is associated with some cases of CFS. (Ablashi et al) and this is supported by research from Dr Daniel Peterson’s group in Nevada. (Whittemore Peterson institute)

The estimate of ongoing active (PCR positivity) of HHV6A in CFS appears to be about 15%.

W John Martin has the following to say about HHV6

 

"Twenty years after the discovery of Epstein-Barr virus (EBV) a new

herpes virus was reported by Salahuddin and his associates. This new

virus was isolated from Patients with AIDS and other lymphoproliferative

disorders and was eventually named as human herpes virus type-6 (HHV-6).

HHV-6 is the smallest of herpes viruses (170 kb) and has been classified as

beta-herpes virus. HHV-6 has been reisolated by many laboratories and a

consensus conference has classified them into subgroups A and B. The

subgrouping is based on restriction endonuclease sites, and biological and

Immunological characteristics.

 

Antibody to HHV-6 and therefore, possible exposure/infection is detected in <80% individuals in the Western world. From all indication it appears that the infection by HHV-6 takes place very early in life after the acute phase the virus becomes

dormant to be activated at a later time. HHV-6 can be reactivated by the

usual factors e.g., immunological and environmental.

 

HHV-6 is exclusive T-cell tropic, induces and up regulates CD4

receptors and cytokine expression, enhances the killing of cells infected

with other lytic viruses such as HIV-1.

 

There is evidence for the association of HHV-6 with at least three lymphoproliferative

diseases; HHV6B is a causative agent for childhood disease Roseola (Exanthem subitum),

a febrile illness in young children, and EBV- and CMV- negative cases

of mononucleosis in young adults. This is an important pathogen that

can initiate pathologies mentioned before, it may also be a cofactor in

several other diseases such as AIDS, cervical carcinoma, and oral carcinoma

HHV-6 is probably reactivated in some infectious diseases, proliferative disorders, and immune deficiencies ”

 

A variety of pathogens either co-infect the same cell or are present in the same environment.

The type and level of viral antigens as well as specific T cell activations for example and

the duration of their presence in that milieu can be important factors that may give rise to a particular disease.

Whereas HHV-6A and HIV-1 may give rise to AIDS-like disease, HHV-6 in conjunction with HPV may result in malignancy of the cervix. HHV-6A becomes latent after the initial infection and can be reactivated by a variety of viruses and vice versa. Interaction between the viruses may take place after the reactivation of these agents."

HHV6a requires special antiviral agents to treat it as the virus does not respond to some of the common anti-herpes anti-virals.

HHV7 and 8. These appear as significant in some malignant diseases.

HHV8 has been identified in Kaposi sarcoma and multiple myeloma.

Immune cells (lymphocytes and macrophages) are major targets in HHV4-9

Herpes virus and immune system evasion.

Members of this family of viruses are capable of interfering at many levels of immune function, as follows.

Impairment of

(1) Antibody recognition of viral epitopes,

(2) Presentation of viral peptides by major histocompatibility complex (MHC) class1 and 2 molecules,

(eg Human and murine CMV both encode a set of glycoproteins known as immunoevasins which prevent presentations of antigenic peptides by MHC class 1 pathways.)

(3) Recruitment of immune effector cells,

(4) Complement activation, and also

By existing in latent forms, and extending the time window for viral replication and spread.

As well viruses appear to make decoy molecules with cytokine action (eg EBV can make an IL10 called vIL10)

Human cytomegalovirus can live in haemopoietic progenitor cells, fibroblasts, smooth muscle cells, endothelial cells, epithelial cells, monocytes, and granulocytes.

In the acute stages lytic effects are seen, but latent presence in monocytes is not lytic.

Most DNA viruses (except for pox viruses) need to enter the cell nucleus for their DNA to be transcribed by cellular RNA polymerase II. Most also depend upon the cell for messenger RNA synthesis and processing.

Tropisms: Many viruses seem to have a predilection for certain cell types. For example, herpes type I and II live in skin and nerve cells, respiratory syncytial virus in respiratory epithelium, EB virus in B-lymphocytes and polio virus in anterior horn cells.

Quite complex processes lead to 10-1000 infectious progeny.

Pathology results from damage to host cells, including induction of apoptosis, but also a variety of other responses including proliferation, of which one long-term consequence can be malignancy (e.g. with hepatitis B and C infections).

I would like to return to Dr W John Martin as he explains one difficulty with some viruses.

 

“What are Stealth Viruses?

Viruses are submicroscopic infectious agents that replicate inside cells. Viral illnesses are normally controlled by the body’s immune system acting primarily through white blood cells called lymphocytes. These cells recognize certain viral proteins that provide the antigens targeted by specific lymphocytes, leading to an anti-viral inflammatory response.

Not all viral proteins, however, can function as antigens for effective anti-viral immunity. Indeed, for many viruses, only a very few proteins are involved in lymphocyte recognition of virally infected cells. Loss of these critical antigenic proteins can allow a virus to essentially go unrecognized by the cellular immune system. When such viruses have managed to retain the capacity to damage cells, they can potentially cause a persistent infection resulting in a prolonged illness.

The viral nature of such an illness is usually overlooked because of the absence of overt inflammation. Atypically structured cell-damaging (cytopathic) viruses were initially identified in patients with the chronic fatigue syndrome and in patients with more severe neurological and neuropsychiatric illnesses.

The term “stealth” was introduced to highlight their basic property of evading effective immune recognition, and also because they had gone unrecognized by the medical community.

Detection of Stealth Viruses

Stealth-adapted viruses can be most readily detected using specialized, semi-quantitative, viral culture methods developed and refined over the last decade. Using these procedures, stealth viruses will typically induce a characteristic vacuolating cytopathic effect (CPE) in cultures of human and animal-derived cells.

Stealth virus infected cultures can be distinguished from cultures of conventional herpes viruses, adenoviruses, enteroviruses and retroviruses, by the appearance and host range of the CPE, and also by using selective immunological and molecular probe based assays, including polymerase chain reaction (PCR) testing methods.”

It seems that further independent work is needed to verify this statement by Martin, but I include his writings for he principles they convey.

It seems likely that even if his ideas are not yet validated, it opens us all to consider the strange balances that may exist between micro-organisms and their hosts.

NOTE:I have included the above, even though Martin has had his lab closed down and some of his work apparently discredited. It is very difficult in this kind of research to be sure that living cells used for viral culture, have not been accidentally contaminated!

The work provides a good model, which if not true fro simian CMV, may be true for HHV6A.

As seen above, I emphasize that viral effects on the immune system include mechanisms to inactivate, deviate or down regulate components of this vital body system, and it is beyond doubt that these strange small infective agents inhabit us all and will emerge as playing more roles in our health and disease than we estimated.

BACTERIOPHAGES
Before we leave the field of virology there is a re-awakening of knowledge about viruses that specifically attack particular bacteria. With the emergence of bacteria that are resistant to antibiotics, researchers are beginning to pay attention the fact that a particular virus called a bacteriophage could kill these resistant organisms.

Attention is drawn to the adverse effects of bacterial lysis by bacteriophages in some situations (eg E coli in some cases of fibromyalgia)

When we come to the later notes on bacteria we need to raise the possibility that we will be able to change the bacterial flora in safer ways than before.

The study of virology is very extensive and the above is to give some basic information about these organisms.

RESIDUAL AND DELAYED EFFECTS OF VIRAL INFECTION.

It is known that viruses such as human immunodeficiency viruses. herpes viruses, E B viruses and CMV persist in the body for life. Research is needed to clarify whether there are some people who carry heavier loads of the herpes family of viruses, and have different T lymphocyte and cytokine responses contributing to some of the fatigue features.

It is already clear that there are different pathologies that emerge in some people when multiple factors operate together (e.g. In Africa E B virus is part of the reason for Burkitt's lymphoma, and in multiple myeloma and Kaposi's sarcoma, HHV8 has been isolated.)

Some researchers such as W John Martin suggest that viruses can be present and participate in pathologies, but escape detection by standard laboratory tests. They have named such viruses "stealth viruses", and these seem to be mutant versions of such organisms as CMV. This may involve mutant forms which have less antigenic proteins.

I have looked at Martin's publications and find them intriguing, but the work requires validation in independent laboratories.

So far such support has not appeared!

I therefore have added an appendage on his work after the reference section.

Some peptide sequences in CMV may be triggers for evoking autoimmune responses.

There is interest in the poliomyelitis virus sometimes giving a delayed post polio syndrome. Perhaps the delayed effect is a subtle residual vulnerability in the anterior horn motor neurones that were originally infected with the virus.

In the section on therapy I will provide a little information about emerging anti viral therapies.

Mechanisms of fever

PYROGENS
In medical sciences much attention has been paid to fever and the mechanisms of generation of high temperatures. Pyrogens are substances from outside the body (exogenous) or from inside the body (endogenous), which generate fever.

Exogenous pyrogens:

These are largely from micro-organisms.

a) Molecules from gram negative bacteria made of lipopolysaccharide and termed endotoxins.

b) Molecules from gram positive bacteria such as cell wall derived lipotechoic acid and peptidoglycans.

c) Some exo and endo toxins from staphylococci and streptococci act as bacterial superantigens -(polyclonal T lymphocyte activators) that bind to the variable region of T cell receptors rather than the antigen-binding region. This can result in mediator* release.

*These mediators are also called cytokines.

I will give a detailed account of these chemical messengers in the section on immunology.

Endogenous pyrogens.

These are polypeptides produced by a variety of host cells, mainly monocytes and macrophages. Interleukin 1 alpha and 1 beta can be produced by phagocytic cells, endothelial cells, B lymphocytes, T (natural killer) cells, fibroblasts and some other muscle cells, also keratinocytes and glial cells. TNF alpha, interferon alpha, and IL6 are also pyrogens.

Fever can make it easier for the body to deal with micro-organisms by impairing micro-organism growth, lessening virulence and enhancing human neutrophil activity against bacteria and enhancing cytotoxic effects of lymphocytes.

There is however an energy loss to the host, as a 1o C temperature increase, increases oxygen requirement by 13%, as well as increasing catabolism, and caloric and fluid requirements.

As mentioned, I will refer further to cytokines and interleukins later in this document.

The next group of organisms is larger than viruses. Viruses are not referred to as cells.

Life certainly contains amazing variation.

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