Antibody based vaccines for Viruses

As viruses replicate and reside inside a cell, antibodies are of not much use in eliminating a viral infection, as they can not penetrate inside the cells. Some viruses have to exit the cell, to infect neighboring cells. In such cases antibodies may help to prevent spread of infection. But, some viruses can directly spread to neighboring cells with out being exposed to antibodies. So once a virus has entered a host cell, cell mediated responses play important roles in eliminating infection. This is about eliminating infection but antibodies can play important roles in blocking infection. Before entering inside a host cell a virus has to attach to the cell and thus is exposed to the extracellular components at least briefly. Antibodies thus might not be of much help in eliminating already established infection, but they can be very good in protecting against new infection. Due to this reason, most of the antiviral vaccines work by inducing strong and specific antibody responses. In such cases, killed vaccine can also be used, which are safer than attenuated, live vaccines.

What keeps a virus from being blocked by antibodies? There could be many possible reasons but one could be the variable nature of surface antigens on these viruses. One of the most famous example is HIV. The glycoproteins on the surface of HIV are extremely variable. Thus, an antibody that can block one virus strain might not be effective against another. This problem can be solved by targeting those antigens which are not variable. The approach is to find out epitopes on the surface of viruses which are conserved. If a antibody can be designed against such targets, then it might prove useful in protecting against many strains of viruses.

A recent review published in annual reviews of medicine, has summarized progress in understanding the host antibody response to HIV-1 and current strategies for applying this information to develop an effective vaccine.
I would like to quote the abstract here:
Developing an HIV-1 vaccine that can elicit antibodies to prevent infection has been a formidable challenge. Although no single immunogen has generated antibodies that can neutralize diverse isolates, progress has been made in understanding (a) the structure of the HIV-1 envelope glycoprotein, which is targeted by neutralizing antibodies, (b) how HIV-1 evades antibodies made by an infected host, and (c) how rare monoclonal antibodies can exhibit broadly neutralizing activity. Advances in structural and molecular biology coupled with new approaches to isolate neutralizing antibodies from HIV-1-infected individuals are enhancing our understanding of what humoral immune responses will be required for a vaccine.