HIV-1 belongs to the Retroviridae family and is one of the most widespread lentiviruses with a high annual prevalence rate. As a result of zoonotic transmission from primates, it has evolved into a human pathogen that is transmitted through body fluids and causes immunodeficiency and impaired general health in infected individuals. One of the main obstacles to viral eradication is the high mutation rate of the genome. The spherical HIV-1 virus consists of an envelope with built-in spikes, a capsid, and a nucleoprotein complex containing RNA molecules and proteins important for replication. A total of 9 genes have been classified, which are divided into structural and auxiliary genes according to their function. Gag and env code for envelope and capsid proteins, pol for enzyme proteins. The tat and rev genes are responsible for regulating gene expression, while vif, vpr, vpu, and nef promote viral immunopathogenesis. Infection of the host cell begins with fusion of the virion to the host membrane, entry, reverse transcription, and integration of the newly synthesized DNA into the host genome. After the synthesis of late viral proteins, including structural proteins, begins, new virions bud from the infected cell and are disseminated throughout the body. Immune defense mechanisms against HIV-1 include the innate immune system (dendritic cells, NK cells, macrophages, and cytokine network), the adaptive immune response (CD4+ and CD8+ T lymphocytes and B lymphocytes), and the intrinsic immune system (APOBEC3G, TRIM5α, tetherin, and SAMHD1). The most important role in evading the immune system is played by the accessory HIV-1 protein Nef. One of its most important roles is to downregulate MHC-I molecules so that they are degraded. This prevents lysis of infected cells by cytolytic T cells (CTLs). Nef also promotes activation of transcription factors and thus viral replication. Other immune defence mechanisms mediated by HIV-1 include mutations and/or masking of epitopes, latency, reverse transcriptase errors, and others. Due to the increasing adaptation of HIV-1, it is necessary to develop the most effective drug or vaccine to stop the spread of the virus or improve the quality of life of those infected.