Identification of Mycoplasma incognitus infection in patients with AIDS: an immunohistochemical, in situ hybridization and ultrastructural study.

Monoclonal antibodies (Mabs) were developed against antigens from a pure culture of Mycoplasma incognitus grown in modified SP-4 medium. All the Mabs obtained were shown to react only with M. incognitus, and not with other species of human mycoplasma. The Mabs identified M. incognitus immunohistologically in thymus, liver, spleen, lymph node, or brain from 22 patients with AIDS, as well as in 2 placentas delivered by patients with AIDS. Using an 35S-labeled DNA probe specific for M. incognitus and in situ hybridization technique, we also identified M. incognitus-specific genetic material in these tissues. Furthermore, ultrastructural studies of the specific areas of tissues which were highly positive for M. incognitus antigens revealed characteristic structures of mycoplasma organisms. These mycoplasma-like particles could be identified intracellularly and extracellularly. Histopathology of the tissues infected by M. incognitus varied from no pathological changes to fulminant necrosis with or without an associated inflammatory reaction. M. incognitus, a novel pathogenic mycoplasma, was cytopathic and cytocidal.

Association of the virus-like infectious agent originally reported in patients with AIDS with acute fatal disease in previously healthy non-AIDS patients.

We studied 6 patients from 6 different geographic areas who presented with acute flu-like illnesses. The patients developed persistent fevers, lymphadenopathy or diarrhea, pneumonia, and/or heart, liver, or adrenal failure. They died in 1-7 weeks. These patients had no serological evidence of HIV infection and could not be classified as AIDS patients according to CDC criteria. The clinical signs as well as laboratory and pathological studies of these patients suggested an active infectious process, although no etiological agent was found despite extensive infectious disease work-ups during their hospitalization. Post-mortem examinations showed histopathological lesions of fulminant necrosis involving the lymph nodes, spleen, lungs, liver, adrenal glands, heart, and/or brain. No viral inclusion cells, bacteria, fungi, or parasites could be identified in these tissues using special tissue stains. We report that immunohistochemistry using rabbit antiserum raised against VLIA, the virus-like infectious agent previously identified in patients with AIDS and shown to cause fatal systemic infection in primates, revealed VLIA antigens in these necrotizing lesions. In situ hybridization using an 35S labeled VLIA-specific DNA probe also detected VLIA genetic material in the areas of necrosis. Furthermore, virus-like particles closely resembling VLIA were identified ultrastructurally in these histopathological lesions. VLIA was associated with the systemic necrotizing lesions in these previously healthy non-AIDS patients with an acute fatal disease.

Fatal infection of silvered leaf monkeys with a virus-like infectious agent (VLIA) derived from a patient with AIDS.

Four silvered leaf monkeys, inoculated with a virus-like infectious agent (VLIA) derived from transformed NIH/3T3 cells (sb51) transfected with Kaposi's sarcoma DNA of an AIDS patient, showed wasting syndromes and died in 7-9 months. Two monkeys had a transient lymphadenopathy in earlier stages. Two moribund animals showed lymphopenia. Although 3 of the VLIA inoculated monkeys had persistent low grade fever early in the infection, the animals became afebrile in the later stages. One VLIA inoculated animal had a prominent antibody response, which occurred 7 months after VLIA inoculation. The other 3 monkeys had a transient or poor antibody response in the later stages. These 3 animals revealed periodic VLIA antigenemia during the course of the experiment. A control monkey was killed 8 months after the last VLIA inoculated monkey succumbed and showed neither an antibody response nor evidence of antigenemia. VLIA-specific DNA could be directly detected in necropsy tissues of all 4 monkeys inoculated with VLIA using the polymerase chain reaction method. VLIA infection was identified in all 4 spleens, 2 of 4 livers, 1 of 2 kidneys, and all 3 brains tested from these 4 animals, but not in the tissues from the control monkey. The necropsy examination of the 4 VLIA inoculated animals revealed no opportunistic infections, acute inflammatory lesions, malignancy or cause of death other than VLIA infection. We believe that the VLIA caused a fatal systemic infection in these monkeys.