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Archive for October, 2009

Immune Evasion

Dear Viewers of ViroMag, Peace be upon You

A few days ago I had a conversation with a student which finally led us to talk about ‘Immune Evasion strategies’ adopted by viruses, she was asking about ‘How viruses could establish an infection, though presence of all these cellular defences?’, actually her question could be more broadly asked as ‘How viruses succeed in infecting our bodies, complete their life cycle, and cause disease in the presence of Immune System in our bodies?!’

We talked generally about the issue, but I think the answer lies in that viruses were created with capabilities which are strengthened by continuous evolution to ‘evade immune responses’ through many mechanisms, and here is ‘An Introduction to the Immune Evasion Strategies‘;

As invaders, parasites, and pathogens initiate the relationship with host species to support their own chances for survival, proliferation, and subsequent dissemination. A stable interaction, from their perspective, consists of a high prevalence rate among the host population and lifelong persistence with minimal symptoms of disease. Achieving such goals would guarantee sufficient time for reproduction and passage to new hosts.

The host immune system, however, mobilizes its molecular arsenal to prevent multiplication and eliminate the infectious agent.

Pathogens, in response, have evolved various strategies to deal with the threat of the host immune system.

What are the basic types of evasion strategies?

  • Passive Mechanisms:

  1. Viruses, such as herpes simplex virus, enter a state of latency in which viral protein production is drastically down-regulated.

  2. Other microbes reside in so-called privileged tissues (salivary glands, neurons) in which factors of the immune response are not active.

  3. Some pathogens exhibit antigenic variation to prevent the immune system from preparing for re-infection

  • Active Mechanisms:

  1. Host-specific active strategies often involve the production of pathogenic immune-modulatory proteins which alter normal host protein function and general immune function

  • Aggressive Mechanisms:

  1. Microbes, like HIV and the measles virus, infect cells essential for immune function (T and B lymphocytes, monocytes), thereby causing immunosuppression”

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Dear Viewers, Peace be upon you all, Here is the answer to the question that I posted few days ago “Can Saliva Transmit Hepatitis C?“, but first, for those who have no information about Hepatitis C Virus, they can go back and read first a previous post here in this blog about Hepatitis C in Egypt, “HCV in Egypt – A HOT SPOT !

Now back to our question “Can Saliva Transmit Hepatitis C?“:

Here are some information for you;

  • The concentration of Hepatitis C virus in a drop of infected blood is exponentially higher than the concentration of HIV in a drop of infected blood (this explains why it is important to avoid anything that could possibly be tainted with any amount of blood)

  • Unlike many other viruses (like HIV), any potential source of blood to blood contact seems capable of carrying the Hepatitis C virus. This is true, even if the source is indirect, such as a used razor, making HCV far more transmissible than most other blood borne viruses

  • While not normally found in urine, semen, vaginal/cervical fluids, feces or saliva, injury or illness may cause some of these substances to be contaminated with blood

  • In nearly half the cases of Hepatitis C, the infected individuals cannot identify the source for their infection

Here are results from studies concerning the issue:

1. As published in the September 2006 issue of Journal of Viral Hepatitis, German researchers investigated the transmission of Hepatitis C via a toothbrush. A team from the University of Regensburg examined 30 patients with Hepatitis C to see whether they had contaminated their toothbrushes with the virus. They collected saliva samples from infected patients both before and after tooth brushing. Figures showed that 30 percent of infected patients tested positive for traces of the virus in their saliva before brushing their teeth, while 38 percent tested positive in their saliva after brushing. Additionally, about 40 percent of the water used to rinse the infected toothbrushes tested positive for the virus. This information confirms the caution against toothbrush sharing, and also sounds a possible Hepatitis C transitory alarm.

2. In September of 2003, evidence that saliva contains the Hepatitis C virus was disclosed at the Interscience Conference on Antimicrobial Agents and Chemotherapy. Scientists from the University of Washington in Seattle concluded that while saliva may be infectious, the strongest predictor of viral presence in the saliva is serum viral load. Researchers found that Hepatitis C was not found in saliva if the person’s viral load was under one million. Additionally, any risk of acquiring infection through salivary contact existed only in the presence of gum disease. Investigators attribute this risk to microscopic amounts of blood in the saliva and visually undetectable open mouth wounds present in gum disease.

All possibilities must be considered in trying to determine how unknown sources of Hepatitis C infection took place. Although Hepatitis C has been detected in saliva, the necessary conditions render it unlikey—but not impossible—to be transmitted by kissing or through the sharing of a toothbrush.

Before anybody panics about these potential risks, remember that there are conditions accompanying these possible modes of transmission:

  1. The person with the virus must have a viral load over one million.

  2. Both parties involved have gum disease.

While experts view the risk of transmitting this disease through saliva as extremely low, it is recommended to maintain good oral hygiene, and toothbrushes be used solely by their owners

NOTE of Importance;

Knowing that risk of transmitting the disease through saliva as extremely low, shouldn’t stop you from calling a physician, it will cost you nothing, just a phone call, or a regular visit, discuss the issue with him, he shall give you more specialized advice about how to avoid more risks in the future;

It is not my intention in this blog to give – by any means – any MEDICAL ADVICE at all!, seek a physician whenever you should do

Thanks for reading my blog, feel free to send me your comments

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Facing Vaccine Shortage

Facing a shortage of vaccines, New York State yesterday dropped its mandate for health care workers to get immunized against swine flu.

Without enough H1N1 vaccine to go around, the Empire State opted to prioritize vulnerable people, such as pregnant women and children, ahead of nurses and doctors. “We had told hospitals that if they had to choose between vaccinating patients or employees to vaccinate patients first,” Richard Daines, New York’s health commissioner, said in a statement.”

Monitoring the situation in developed countries, makes me more worried about poor ones!

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“PARIS (Reuters) (Thu Oct 22, 2009 1:55pm EDT), By Tan Ee Lyn – Brief electric shocks may help the body better respond to certain kinds of experimental AIDS vaccines, U.S. researchers said on Thursday.

They used a device that looks like a handgun to inject vaccine along with three brief electrical pulses to open up cell membranes so that the vaccine can get inside.

Sandhya Vasan of the Aaron Diamond AIDS Research Center in New York said the technique, called electroporation, may be particularly useful in delivering DNA vaccines, which use an infectious agent’s own genetic material to elicit an immune response.

“With a brief pulse of electricity, our cell membrane temporarily opens up and allows a lot more of the DNA to get inside. The reason why DNA vaccines by themselves don’t trigger A powerful immune response is because most of it (DNA) does not get inside our cells,” Vasan told Reuters in an interview.

(more…)

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Yesterday one of our students came to ask me – she seemed worried – about ‘Can Saliva Transmit Hepatitis C Virus?’, she told me that her – as I can remember – younger brother (a child) put the toothbrush of her grandmother (which is HCV positive) into his mouth, WHAT DO YOU THINK! I am posting later God Willing, till then, you can give me your answers

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“As America faces warnings of a vaccine shortage, Europe is getting underway with the H1N1 jabbing.

In the UK vaccinations start today, with doctors, nurses and pregnant women first in line for shots. “This is the first pandemic for which we have had vaccine to protect people. I urge everyone in the priority groups to have the vaccine,” says Liam Donaldson, the UK’s Chief Medical Officer (press release).

France has also started vaccinating this week, and Germany will begin 26 October, followed by Ireland on 2 November.

Last week the US Centers for Disease Control and Prevention warned that vaccine production was not going as well as might be hoped. Anne Schuchat told reporters some manufacturers were having difficulties and production was “a bit delayed”.

“We wish that we had more vaccine and there is more vaccine coming out every day,” she said.

Australia became the first country to begin mass vaccination against H1N1 when it rolled out its programme on 30 September”

SOURCE

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Baltimore Scheme

Peace be upon you All, during the first session of a plant virology course, our undergraduate students are introduced to viral structures, morphology, and some other basics, I had a discussion with some of these young students that led us to the Baltimore classification scheme, so I think it might be of benefit to give some info about it;

The Baltimore classification clusters viruses into families depending on their type of genome.

Cell genomes are all composed of double-stranded DNA, whereas viral genomes are declined into all nucleic-acids possibilities: dsDNA, ssDNA, dsRNA, ssRNA. Moreover some viruses are using unique replication mechanisms such as reverse-transcription. David Baltimore (Nobel prize 1975) proposed a classification based on the genome present in virions. This system classify all known viruses into seven classes;

  • I: dsDNA viruses (e.g. AdenovirusesHerpesvirusesPoxviruses)
  • II: ssDNA viruses (+)sense DNA (e.g. Parvoviruses)
  • III: dsRNA viruses (e.g. Reoviruses)
  • IV: (+)ssRNA viruses (+)sense RNA (e.g. PicornavirusesTogaviruses)
  • V: (−)ssRNA viruses (−)sense RNA (e.g. OrthomyxovirusesRhabdoviruses)
  • VI: ssRNA-RT viruses (+)sense RNA with DNA intermediate in life-cycle (e.g. Retroviruses)
  • VII: dsDNA-RT viruses (e.g. Hepadnaviruses)
  • The nice about this scheme (actually about any classification scheme) is that classifying viruses according to their genome means that those in a given category will all behave in much the same way, which offers some indication of how to proceed with further research

    Learn MORE

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