Question

What are the problems that scientists have had to deal with in trying to produce an AIDS vaccine?

Answer 1

Some of the major scientific challenges in way of development of HIV vaccine are:

1. High diversity:  HIV uses reverse transcriptase enzyme to convert their RNA to DNA so that the viral DNA may be incorporated in the host genome. However, reverse transcription is a significantly more error prone process than replication. This results in widespread mutation in HIV virus worldwide. Vaccine design becomes significantly more challenging due to such high and frequent variations.
2. Inadequate animal testing: At present, animal models have proved inadequate for testing HIV virus, as HIV does not elicit the same immunological responses in lab animals as humans.
3. Long latent period: HIV has a very long incubation period, lasting upwards of a decade. During this time it can be entirely asymptomatic. This gives sufficient time for production of extensive viral load in host body which can be difficult to eradicate.
4. Unsafe attenuated virus: Live attenuated HIV virus is not safe enough to be used as vaccine. Whole dead virus or protein subunits, on the other hand do not elicit a broad immune response.
5. Widespread immunogenic response: HIV primarily affects T helper cells which are not directly involved in immune reactions but helps activation of both humoral and cell mediated arms of our immune system. This can affect a myriad of target organs. Immune responses to such attack are highly type specific.Such widespread reactions prove challenging during vaccine development.
6. Inability to prevent acquisition of infection: Cell mediated immune responses induced by a vaccine while helps in stopping further damage, cannot prevent acquisition of infection in the first place.