Lecture on Vaccines and HIV Evolution

Lecture was giver by Dr.Bruce.D.Walker from Howard Hughes Medical Institute,Topic is Vaccines and HIV Evolution.some of important points from the lecture.About 33 million people are currently infected by HIVof this 90% of people are living in Developing countries

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How vaccine works

  • Preventing infection (sterilizing immunity).
  • Prevent disease (but doesn't prevent infection) by keeping the microbe or its toxins in check (non-sterilizing immunity).
  • Goal of the vaccine is to alleviate symptoms and stem transmission.

When B-cells exposed to pathogen are converted into plasma cell and starts to secreate antibodies who job is directly neutralizes virus by binding to outer surface of the virus cell.

Aim of vaccine is to trick the B-cells in thinking that are seeing pathogen,so that they start making antibodies that will prevent future infection.

Possible vaccine
  • Killed Virus
  • Live attenuated Virus
  • Recombinant protein
  • Recombinant Virus

Reasons for non availability HIV vaccine

  • HIV Reverse trascriptase makes frequent errors during replication
  • Sequence variation leads to escape from antibodies and CTL(cytotoxic T-cells) responses
  • Loss of CD4 cells leaves immune system unable to respond effectively to newly emerging Mutants.
  • GP120 envelope protein undergoes lot of mutation which in turn makes the gp120 structure differnt,Because of this antibodies are unable to bind with HIV virus.

Hiv Vaccine Marveck
On 21 September 2007, the pharmaceutical giant Merck called a halt to a phase II trial of a new vaccine candidate against HIV . An interim assessment showed that the vaccine, long considered the most promising in development, failed both in preventing HIV infection and in reducing the viral load of those infected.The vaccine candidate (Merck V520) is a mixture of three components, each a weakened adenovirus vector carrying one of the three synthetic HIV genes gag, pol and nef. The vaccine is designed to elicit a cell-mediated immune response, to stimulate the body’s own CD8 T-cells that recognize and kill the HIV-infected cells.

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