Feeds:
Posts
Comments

Archive for the ‘Immunology’ Category

Dear readers, Peace be upon you all!

This post comes in reply for what was published recently by, Rogier Bodewes and colleagues (Yearly influenza vaccinations: a double-edged sword?) urging re-evaluation of vaccine recommendations because the inactivated vaccine available at present does not induce heterosubtypic immunity and might make infants more susceptible to pandemic influenza.”1,

and before reading the reply, it would worth mentioning that heterosubtypic immunity is an immunity that is cross-protective between different influenza A virus subtypes

a reply came recently in the Lancet,

“… Bodewes and colleagues’ concern is primarily on the basis of their recent animal experiment.1, In animal studies, the investigators have full control over any environmental or other factors that might have an effect on the outcome of interest.

This is in [obvious] contrast with the situation among people leading their daily lives. In the context of influenza, it is highly probable that almost everyone, vaccinated or not, who lives in a community during an outbreak of influenza is exposed to the circulating influenza viruses.  The consequences of such exposures in vaccinated persons are not known, but it would be difficult to believe that these would not induce any immunological responses. The efficacy of  influenza vaccine is far from optimum and, especially among young children, symptomatic

breakthrough illnesses happen frequently despite vaccination. Because influenza vaccination cannot prevent all symptomatic infections, it could be postulated that its ability to prevent asymptomatic infections is even worse [!].

A logical implication of this is that most vaccinated children are repeatedly attacked by wild-type influenza viruses during local outbreaks and might develop asymptomatic infections that, in turn, can induce the development of partial heterosubtypic immunity

On the basis of the accumulating data from the present A H1N1 pandemic, the authors’ concern does not seem warranted. By contrast with regular influenza seasons in which the highest attack rates are seen in young children, 2,3

the 2009 A H1N1 pandemic has so far primarily affected adolescents and young adults. 4 Available data from the USA also suggest that paediatric influenza-associated case mortality during the present pandemic—the first one in the era of a general recommendation to vaccinate all children in the country—seems not to be higher than that seen during the three preceding regular influenza seasons.5

In a case–control study from Mexico, seasonal influenza vaccination was associated with a reduced risk of severe pandemic H1N1 infection.6 Moreover, the well-known W-shaped mortality curve from the infamous 1918 A H1N1 pandemic—during which time no vaccine was available—does not support the authors’ hypothesis. 7 If heterosubtypic immunity induced by repeated influenza infections during childhood provided any substantial protection against severe forms of illness, no such increased mortality among young adults should have been seen.[this is a nice observation I think]

We fully agree that there is a need for more effective influenza vaccines that would induce broader immune responses.

In children, the live-attenuated influenza vaccine seems to be more effective than the conventional inactivated vaccine,8 but the live vaccine is not available in Europe at present, and even in the USA it is only indicated for children 2 years of age or older.9 Public health decisions should be based on the best clinical evidence available. There is ample evidence for the great burden of influenza in young children,2,3,10 and this burden appears during every influenza

season. By contrast, there is no clinical evidence that vaccinating children against influenza  would  prevent the induction of heterosubtypic immunity and thereby be disadvantageous to children in the long run.

While waiting for improved influenza vaccines, the simple question isshould we let young children suffer  from a severe and potentially lethal but easily preventable illness, just because there is a theoretical possibility that withholding vaccination might result in a slightly less severe illness sometime in the future? We believe that the answer to this question is a simple one.”

Did the post assure you, or not!, (you can tell me)


References:

1  Bodewes R, Kreijtz JHCM, Baas C, et al. Vaccination against human influenza A/H3N2 virus prevents the induction of heterosubtypic immunity against lethal infection with avian influenza A/H5N1 virus. PLoS One 2009;4: e5538.

2  Heikkinen T, Silvennoinen H, Peltola V, et al. Burden of infl uenza in children in the community. J Infect Dis 2004; 190: 1369–73.
3  Poehling KA, Edwards KM, Weinberg GA, et al. The underrecognized burden of influenza in young children. N Engl J Med 2006; 355: 31–40.

4  Gilsdorf A, Poggensee G, on behalf of the working group pandemic influenza A(H1N1)v. Infl  uenza A(H1N1)v in Germany: the first 10,000 cases. Euro Surveill 2009; 14: pii=19318.

5 CDC. Seasonal infl  uenza—weekly report: infl  uenza summary update. Atlanta, GA: Centers for Disease Control and Prevention, 2009. http://www.cdc.gov/fl  u/weekly/ (accessed Oct 12, 2009).

6  Garcia-Garcia L, Valdespino-Gómez JL, Lazcano-Ponce E, et al. Partial protection of seasonal trivalent inactivated vaccine against novel pandemic influenza A/H1N1 2009: case-control study in Mexico City. BMJ 2009; published online Oct 6. DOI:10.1136/bmj.b3928.

7  Glezen WP. Emerging infections: pandemic influenza. Epidemiol Rev 1996;18: 64–76.

8  Belshe RB, Edwards KM, Vesikari T, et al. Live attenuated versus inactivated infl uenza vaccine in infants and young children. N Engl J Med 2007;356: 685–96.

9 CDC. Seasonal influenza—recommendations for using TIV and LAIV during the 2009–10 influenza season. Atlanta, GA: Centers for Disease Control and Prevention, 2009. http://www.cdc.gov/flu/professionals/acip/
recommendations.htm (accessed Oct 12, 2009).

10  Heikkinen T, Booy R, Campins M, et al. Should healthy children be vaccinated against infl  uenza? Eur J Pediatr 2006; 165: 223–28

 

 

Advertisements

Read Full Post »

Dear ViroMag Readers, Peace!

I’m back, and thanks for not going away!

Here is a WHO page on “Safety of Pandemic Vaccines”, where “WHO has received vaccination information from 16 of around 40 countries conducting national H1N1 pandemic vaccine campaigns.” and here are the results

Finally, WHO report concludes “Although intense monitoring of vaccine safety continues, all data compiled to date indicate that pandemic vaccines match the excellent safety profile of seasonal influenza vaccines, which have been used for more than 60 years.

Note: For those who hold the conspiracy theory approach and do not believe such publications, sorry, I can’t help

Read Full Post »

Dear readers, Peace!

Few days ago I was asked about obesity, whether it is a risk factor for increased morbidity/mortality form the current swine flu (H1N1) pandemic strain, and here is what I found (in the news)

“A study in California shows that about a quarter of the people hospitalized for H1N1 complications were morbidly obese, even though less than 5% of the population falls into that category.

Obesity appears to be a risk factor [nearly similar] with pregnancy for developing complications from an infection with pandemic H1N1 influenza, according to the most comprehensive look yet at swine flu hospitalizations

The CDC considers adults to be obese if their body mass index is 30 or above and morbidly obese if their BMI tops 40

BMI

About a quarter of those hospitalizations have been for people who were morbidly obese, even though such people make up less than 5% of the population. That fivefold increase in risk is close to the sixfold increase observed in pregnant women, according to the report published today in the Journal of the American Medical Assn.

The researchers found that two-thirds of the obese patients had a health problem that was previously recognized as an underlying risk factor for swine flu. The most common were chronic lung disease, heart disease and diabetes.

But that still left one-third of obese patients without other risk factors [other than obesity]“, said Dr. Janice K. Louie, lead author of the study and chief of the state health department’s influenza and respiratory syndromes section.

There are many possible explanations;

Some of them are physiological. The lungs of obese patients are compressed because the abdomen presses up on the diaphragm. In addition, the chest wall is heavier, so it’s more difficult for the lungs to stay inflated.

Both of those factors make it difficult for blood and oxygen to travel throughout the lungs and fight off infection, said Dr. Lena Napolitano, chief of acute-care surgery at the University of Michigan Health System. She recently published a report in the CDC’s Morbidity and Mortality Weekly Report on 10 swine flu patients admitted to the intensive care unit there; of the 10, nine were obese, including seven who were morbidly obese.

The compromised immune system of obese people probably also plays a role, said Dr. David Heber, director of the Risk Factor Obesity Program at UCLA’s David Geffen School of Medicine. Scientists believe that people who are obese have a baseline level of inflammation that diminishes the body’s ability to fight diseases.

Researchers at the University of North Carolina in Chapel Hill found that 42% of obese mice died when infected with a human strain of flu, while the same virus killed only 5% of lean mice. The lungs of the obese mice failed to produce two crucial kinds of immune cells called cytokines that fight off viruses. There was also a decrease in natural killer cells and T-cells, two other components of the immune system, said Patricia Sheridan, a nutritional immunologist at UNC who worked on the study.”

I think that Obesity is bad anyway!

Read Full Post »

Immunodiffusion

Peace be upon you, yesterday in our weekly Medical Immunology section we were talking about ‘Immunodiffusion‘ we first talked about what is meant by immunoprecipitation? (the principle behind immunodiffusion techniques) which simply is ‘a technique in which an antigen is precipitated from solution by using an antibody’, we discussed a little the ‘point of equivalence’ where maximum precipitation takes place, when optimal proportions of antigens and antibodies are met ‘to cross link and form a lattice

then we talked about ‘Gel Immunodiffusion’ where reactants (antigen and antibodies) diffuse through a substance such as agar, and lines of precipitation are observed in Gel!

Immunodiffusion may be carried out as either ‘single radial immunodiffusion’ or ‘double immunodiffusion’ reactions, in single immunodiffusion reactions, only one reactant diffuse through the gel, and the other is ’embedded’ in the gel!, where results appear as a ring of precipitation around the well containing the diffusing reactant.

Second ‘double immunodiffusion’ which is also called ‘Ouchterlony Double Immunodiffusion‘ where both reactants (antigen and antibodies) diffuse in opposite directions towards each other forming an arc (not a ring!)

Immunodiffusion reactions can be done in Plates

like this one,

and it is obvious (as shown above) that they can be also made on slides !!!

I left them with a question to comment on the following figures, I’ll leave the answer to them, and we can discuss the answer in another post

Read Full Post »

Pregnancy Test – ELISA

Dear 4th year Microbiology/Special students, Peace be Upon You, here is the Animation I was talking about Last Section, watch and feel free to Leave your comments and questions

Vodpod videos no longer available.

Read Full Post »

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”

Read Full Post »

Immunology Quizz

Yesterday I had a ‘Medical Immunology’ section, where we were discussing agglutination (e.g. clumping of red blood cells (RBCs) due to presence of antibodies), then we discussed the ABO and Rh systems for blood grouping,

then I gave my students the following question that I wanted to share with you, that if you got an answer you’d like to share with us, that would be great, I think the issue is so exciting to discuss, with nice immunology in it, and many simple notions that every person shall take care of, esp. pregnant women, HERE IS THE QUESTION;

Consider the following case; A woman with a blood group B+ married to a man with A- blood type, she was pregnant with an AB- child, and she delivered safely, later on she developed an acute condition that demanded plasma transfusion, discuss options available for this women, provided the following tables;

RBCTablePlasmaTable

Waiting for your Answers!

Read Full Post »