Complex sentence: This is a brief description of the traditional view of viral infection, however, viruses can also infect target immune system cells through endocytosis as may be the case with T lymphocytes and HIV infection.
Split into simpler sentences: This is a description of the traditional view of viral infection, however, viruses can also infect target immune system cells as those cells engulf and phagocytize the virus. This may be the case with T lymphocytes and HIV infection.