The present invention relates to novel monoclonal antibodies which may be used in the detection of Human Immunodeficiency Virus (HIV). These antibodies exhibit an unusually high degree of sensitivity, a remarkably broad range of specificity, and bind to novel shared, non-cross-reactive epitopes. In particular, the monoclonal antibodies of the present invention may be utilized to detect HIV-1 antigen and HIV-2 core antigen in a patient sample.