Human Immunodeficiency Virus (HIV-1) is an epidemic that affects over 34 million people worldwide. Although there is currently no effective vaccine, some patients can develop broad neutralizing antibodies after 2-5 years of infection. These broadly neutralizing antibodies, however, are not capable of neutralizing all strains of HIV-1. When attempting to produce an effective vaccine, overcoming these downfalls of naturally occurring neutralizing antibodies is crucial for creating a vaccine that is applicable to the neutralization of many different virus strains. Differences in the exposed envelope glycoprotein may explain why certain strains, which have been adapted for easy laboratory use, can be easily neutralized but other strains, which affect the majority of infected patients, cannot. Previous work has identified a region of interest within the envelope glycoprotein subunit gp41 responsible for causing differences in neutralization sensitivity. From this region, we have identified amino acids that differ between two representative strains and are attempting to specify which mutation is responsible for determining sensitivity or resistance by point-directed mutagenesis. If we can understand how these differences prevent neutralizing antibodies from binding, we may be able to produce better immunogens able to guide the immune system to overcome these resistance-inducing mutations.