Vaccine development is difficult because:

	HIV mutates rapidly
	HIV is not expressed in many cells that are infected
	HIV is not completely cleared by the host immune response after primary infection.
	HIV isolates show a marked variation, especially in the envelope antigens-variability that probably promotes the emergence of neutralization-resistant mutants
	Lack of an appropriate animal model for HIV.
	Chimpanzees are the only animals that are susceptible to HIV.

Novel methods are under investigation:

Soluble form of CD4 has been made by recombinant DNA techniques and is being studied as a viral blocking agent. As CD4 is the HIV receptor on cells, soluble CD4 may inhibit HIV from infecting cells; may block gp120-mediated events, such as cell fusions and may serve as a targeting signal to direct cytotoxic agents to HIV-infected cells.

Gene therapy approach are being developed that are designed to achieve "intracellular immunization," ie., genetically alter target cells to make them resistant to HIV.

Control measures:

To avoid epidemic spread of HIV it is important to educate the people about eliminating the high risk factors.

All blood donors should be tested for HIV antibody

Myths to be dispelled about HIV

HIV is not spread by

Sharing meals with an HIV +ve patient

Exposures to sneezing, coughing, or other casual contacts.