Medicina

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Immunological characteristics










Sara Garrido Paniagua
3ºMedicine 2012-2013 (Medical English)
INDEX



+Introduction………………………………………………………………….Page 1

+Virus characteristics………………………………………………………….Page 1

+Lifecycle……………………………………………………………….……..Page 2

+Stages of infection………………………………………………………....…Page 3

+Immunologicalabnormalities………………………………………...…..…Pages 3-4

+Infection ways………………………………………………………….…….Pages 4-5

+Treatment…………………………………………………………………….Page 5

+References……………………………………………………………………Page 6





































INTRODUCTION

To begin with the work, it’s a good idea to start by defining the type of disease that AIDS is, an immunodeficiency. Asan introductory explanation, we can say that:

The immune system consists on a set of proteins and cells that work together to defend the individual from infectious agents. Therefore, any fault that occurs in this system will result in a defective response, favoring the development of infections. A heterogeneous group of diseases caused by defects of immune system are calledimmunodeficiencies.

These immunodeficiencies can:

1. Only affect a component of the immune system, altering a particular function.

2. Produce an overall deterioration of the immune response as in the case of AIDS that is what we will focus on.

Immunodeficiency is defined as any change that occurs in the individual results in a severe defect in any of the immunefunctions. This may be due to:

1. Genetic defect, as in the case of congenital immunodeficiencies

2. Process acquired (as in the case of AIDS virus infection), malnutrition or even depression, i.e. postnatal changes in the body. They are called acquired immunodeficiencies.




VIRUS CHARACTERISTICS

HIV (the virus which causes AIDS) belongs to the family ofretroviruses whose genetic material consists on RNA, which needs to be copied to a double strand of DNA to integrate into the infected cell (CD4 + lymphocytes). This process is carried out by the enzyme “reverse transcriptase”. Genetic material is covered by a nucleocapsid core and an outer lipid envelope where are inserted several viral proteins gp 160, gp 41, gp 120.

LIFECYCLEHIV infects CD4 leucocytes through molecules CD4, but relies on other molecules: the chemokine.

1. Attachment of the virus to the cell:

HIV not only infects CD4 + leukocytes, especially CD4 + T cell but also some monocytes and dendritic cells expressing the marker, and using this marker as a receptor molecule specific to gp120 protein. But this is not enough. Besidesexpressing CD4 +, target cell should express at least some chemokine receptors (RQ) used as the virus coreceptor: CCR3, CXCR4 (fusin) or CCR5. In fact, there are two strains of HIV virus: the monotropic (more frequent early in the infection, like to infect monocytes and macrophages) and lymphotropic (in the last period, preferentially infect lymphocytes). Early strains use as coreceptor CCR5 to infectmacrophages (or in the case of CCR3 microglia, brain macrophages), whereas the later strains use CXCR4 to infect lymphocytes. After union of gp120-CD4/RQ, protein gp41 of HIV lipid envelope of the virus induces fusion to the target cell membrane allowing entry into the cell.

2. Releasing of nucleic acids in the Cell

3. Retrotranscription

 Once inside, the host cellvirus enzymatic machinery starts working to convert the RNA strand of a double strand of complementary DNA to the virus.

4. GDNA-insertion:

 The viral DNA, thanks to the enzyme “integrase”, will be integrated into the cellular genome. The copy of integrated viral DNA can remain for months or years. The viral genome’s transcription will start when the infected cell...