The present invention relates to cupredoxin, specifically Pseudomonas aeruginosa azurin, and/or Pseudomonas aeruginosa cytochrome c.sub.551 and their use in inhibiting of viral infection, and in particular infection of mammalian cells by the Human Immunodeficiency Virus (HIV). The invention also relates to variants and derivatives of cupredoxin and cytochrome c that retain the ability to inhibit viral infection, and in particular infection by the Human Immunodeficiency Virus (HIV). The invention also relates to research methods for studying viral and bacterial infection in mammalian cells.