Monday, November 15, 2010

Immunization and Vaccines

There are two types of immunization: Active and Passive. Passive immunization is temporary. Breast milk provides passive immunity for infants by providing them with antibodies. Passive is also used with immunodeficient individuals, after an exposure, and to block bacterial toxins. The shots for these are called peanut butter shots because they are really thick.  Passive comes in the form of immune serum globulin, specific immunoglobulins, and monoclonal antibodies.

When the immunization causes the activation of your own immune cells it is active immunization. This happens when you are naturally exposed to the pathogen or through vaccines. Vaccines come in two types, inactivated vaccines and live vaccines.


Autism vs Vaccines
A lot of people think that vaccines cause autism, and the short answer is they don't. There have been some reports stating there is a correlation, suck as the Wakefield et al that presented 12 cases of children with autism that supposedly got it from the MMR vaccine. But here are some facts about the Wakefield study:
  • The 12 children in the study were carefully selected, and many of their parents already believed MMR vaccination was the cause of their children’s autism.14
  • Dr Wakefield had serious undisclosed financial conflicts: he was funded by lawyers involved in lawsuits against immunization manufacturers and was applying for a new vaccine patent.14,15
  • In 2004, 10 of the 13 authors retracted their support for the MMR-autism association.16
  • Britain’s General Medical Council investigation found Wakefield guilty of dishonesty and irresponsibility.15
  • In 2010, the Lancet fully retracted the Wakefield study 
(Alan, Micheal G. The autism-vaccine story:fiction and deception?. Canadian Family Physician, 56, October 2010).

There have been over 20 case studies to determine of there is a correlation (correlation does equal causation) between MMR and autism, and all have failed to find any. Mrozek-Budzyn D and colleagues publish a paper this may in Pediatric Infectious Disease Journal stating:

Results: For children vaccinated before diagnosis, autism risk was lower in children vaccinated with MMR than in the nonvaccinated (OR: 0.17, 95% CI: 0.06-0.52) as well as to vaccinated with single measles vaccine (OR: 0.44, 95% CI: 0.22-0.91). The risk for vaccinated versus nonvaccinated (independent of vaccine type) was 0.28 (95% CI: 0.10-0.76). The risk connected with being vaccinated before onset of first symptoms was significantly lower only for MMR versus single vaccine (OR: 0.47, 95% CI: 0.22-0.99).
Conclusions: The study provides evidence against the association of autism with either MMR or a single measles vaccine.

I started a part on live vaccines, but it got lost so all I am going to say about them is some come from incubating in chicken eggs, where they grow them so they become better suited for an environment not similar to our bodies. Maybe more once my headache is gone.

Friday, November 12, 2010

Daily Disease: Influenza and Vaccines

With flu season coming up (depending on where you live) I thought this would be a good review to go over.

According the Control of Communicable Diseases Manual (<3) it is an "acute viral disease of the respiratory tract characterized by fever, cough (usually dry), headache, myalgia, prostration, coryza, and sore throat." The reservoir is humans and the mode of transmission is through large spread from coughing or sneezing.

Cover your mouth sicko!!

Always cover your mouth when coughing or sneezing, but not with your hands! Use your elbow if you don't have a tissue.

The incubation period is on average two days, which means that from your first exposure to full blown disease takes two days. Influenza can be fatal for the elderly, infants, and those with compromised immune systems and may lead to secondary bacterial infections such as pneumonia.

Family Orthomyxoviridae. The virion is enveloped and 80-120 nm in length. The enveloped is taken from the host plasma membrane during the process of budding. The genome is ss RNA negative sense and is in six to eight fragments, each of the segments codes for one or two proteins
The hemagglutinin glycoprotein attaches to host cells sialic acid residues present in the ciliated epithilium, and the loss of these cells is a loss in their function, which is to clear the tracts of debris and bacteria. Viral replication in these cells induces the secretion of interferons and cytokines that causes inflammation.

The HA and NA are the proteins that determine the virions tropism, or what tissues it can infect and is also used in the classification of the virus. An H1N1 and H5N1 differ in the HA protein.
Okay I just notice a discrepancy between the image and my notes, the RNA is negative sense, we'll go with the leading virologist that wrote the section on Orthomyxovirus.

Epidemics and Pandemics
The worst epidemic since the black plague was the 1918 Spanish flu pandemic (meaning it was world wide) that killed 20 million people world wide and unleashed the terror that is Edward Cullen (according to my virology professor).  Other epidemics include the Hong Kong epidemic in 1967, Asian flu in 1956, and the H1N1 flu in 2009. The epidemics appear to be cyclic, occurring every 10 to 50 years.

The epidemics are caused the genomes affinity for genetic variability and rapid evolution. In a process know as antigenic drift the RNA ploymerase that copies the RNA for progeny makes mistakes (there is no proof reading function, unlike DNA polymerase), and the accumulation of mutations causes changes in the HA and NA glycoproteins. This is the main reason why there are new flu vaccines each new flu season. It is a new virus that our immune systems haven't encountered before.

The other process that allows for genetic variability is antigenic shift. Antigenic shift occurs when a cell is infected with multiple types of influenza virions, and the genes are reassorted.
In this picture we can see that the pig is infected with a human  virus and an avian virus. Some of the avian influenza genes are packages with the human influenza genes creating a knew virus that our immune systems have not encountered before.  This was the case with the H1N1 flu last year. And no, you can't get it from eating pork.

Well, hope that made sense (compressing pages and pages of notes is hard) and was interesting if not entertaining. Feel free to ask questions, make requests, etc.

I'm going to eat lunch then post about vaccines and whether or not viruses are alive.
Oh, does anyone know how to get the cute poupee girl gagdet? It's driving me crazy.

My brother just accused me of plagiarism, so here are my sources: CDC, Fundamentals of Molecular Virology, Medical Microbiology sixth edition, and my old papers.

Thursday, November 11, 2010

Anatomy of the Virus

A virus consists of a genome enclosed in a protein coat called a capsid. This capsid protects the genome from the environment while it is outside of the host cell.
This image shows the DNA of the adenovirus inside of the capsid. Some capsids have icosahedral geometry as shown in this figure:
The capsid also aids the virus in attaching entering a host. The surface proteins, such as the ones labeled "fiber" in the first image attach to proteins on cells. Some viruses have an envelope, a lipid membrane that surrounds the capsid. There is a variety of shapes and sizes, they can be icosahedral, helical, or alien robotish like bacteriophages.
A single infectious particle is called a virion.

Viruses also show diversity in genetic make up. Excluding a lot of viruses, all life starts with the blue prints of double stranded DNA. From bacteria and protozoa to trees and tigers. But viruses can use either DNA or RNA. Further, it can be either single stranded (ss) or double stranded (ds), or linear or circular (bacterial DNA is circular and eukaryotic is linear). Bacteriophage phiX 174 is a ds DNA virus. The Papillomaviruses have circular ds DNA.

Viruses are relatively simple organisms, and carry none or  a few proteins and enzymes with them. This creates a problem, since they have no enzymes to carry out tasks such as building nucleic acid (essential for replication) for DNA or RNA, nor can they create usable energy. They have no ribosomes to synthesize proteins. To overcome this problem they essentially hijack other living organisms and use their machinery to make new viruses. Because of this viruses are considered obligatory intracellular parasites.

Stay tuned for scenes from the next entry!!

So next time I'll cover influenza and vaccines. After that I want to do ebola, HIV, MRSA, papillomavirus, herpes, neisseria, and an enterobacteriaceae. If you want to see anything in particular just ask!

Also some feedback would be really appreciated, was it easy to follow, confusing, boring, etc.
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