Pathology of experimental aerosol Zaire ebolavirus infection in rhesus macaques.

There is limited knowledge of the pathogenesis of human ebolavirus infections and no reported human cases acquired by the aerosol route. There is a threat of ebolavirus as an aerosolized biological weapon, and this study evaluated the pathogenesis of aerosol infection in 18 rhesus macaques. Important and unique findings include early infection of the respiratory lymphoid tissues, early fibrin deposition in the splenic white pulp, and perivasculitis and vasculitis in superficial dermal blood vessels of haired skin with rash. Initial infection occurred in the respiratory lymphoid tissues, fibroblastic reticular cells, dendritic cells, alveolar macrophages, and blood monocytes. Virus spread to regional lymph nodes, where significant viral replication occurred. Virus secondarily infected many additional blood monocytes and spread from the respiratory tissues to multiple organs, including the liver and spleen. Viremia, increased temperature, lymphocytopenia, neutrophilia, thrombocytopenia, and increased alanine aminotransferase, aspartate aminotransferase, γ-glutamyl transpeptidase, total bilirubin, serum urea nitrogen, creatinine, and hypoalbuminemia were measurable mid to late infection. Infection progressed rapidly with whole-body destruction of lymphoid tissues, hepatic necrosis, vasculitis, hemorrhage, and extravascular fibrin accumulation. Hypothermia and thrombocytopenia were noted in late stages with the development of disseminated intravascular coagulation and shock. This study provides unprecedented insight into pathogenesis of human aerosol Zaire ebolavirus infection and suggests development of a medical countermeasure to aerosol infection will be a great challenge due to massive early infection of respiratory lymphoid tissues. Rhesus macaques may be used as a model of aerosol infection that will allow the development of lifesaving medical countermeasures under the Food and Drug Administration's animal rule.

Human antibodies to major histocompatibility complex alloantigens mediate lysis and neutralization of HIV-1 primary isolate virions in the presence of complement.

Cellular proteins, including major histocompatibility complex (MHC) class I and class II antigens, are incorporated into the membrane of HIV-1 when virions bud from infected cells. Experiments were performed to determine whether human sera that contained MHC class I and/or class II antibodies would lyse or neutralize a primary isolate of HIV. These results demonstrate that in the presence of complement, sera from some alloimmunized persons mediated significant anti-viral activity against an HIV primary isolate. Both lysis and neutralization of virus were observed. The antiviral effects were complement dependent because heat inactivation eliminated most anti-viral effects. Antiviral activity mediated by sera containing MHC alloantibodies in the presence of complement was > or = activity due to sera from HIV-infected persons as reported in this and a previous study. High levels of antibodies to both MHC class I and class II were present in sera that mediated the highest levels of anti-viral activity. Absorption of serum with platelets (which express class I but not class II antigens) substantially reduced their lytic activity. These studies suggest that MHC antibodies mediate potent anti-viral effects on primary isolates of HIV and support the possibility that deliberately alloimmunizing humans might protect against HIV infection.

CD4-Negative cells bind human immunodeficiency virus type 1 and efficiently transfer virus to T cells.

The ability of human immunodeficiency virus strain MN (HIV(MN)), a T-cell line-adapted strain of HIV, and X4 and R5 primary isolates to bind to various cell types was investigated. In general, HIV(MN) bound to cells at higher levels than did the primary isolates. Virus bound to both CD4-positive (CD4(+)) and CD4-negative (CD4(-)) cells, including neutrophils, Raji cells, tonsil mononuclear cells, erythrocytes, platelets, and peripheral blood mononuclear cells (PBMC), although virus bound at significantly higher levels to PBMC. However, there was no difference in the amount of HIV that bound to CD4-enriched or CD4-depleted PBMC. Virus bound to CD4(-) cells was up to 17 times more infectious for T cells in cocultures than was the same amount of cell-free virus. Virus bound to nucleated cells was significantly more infectious than virus bound to erythrocytes or platelets. The enhanced infection of T cells by virus bound to CD4(-) cells was not due to stimulatory signals provided by CD4(-) cells or infection of CD4(-) cells. However, anti-CD18 antibody substantially reduced the enhanced virus replication in T cells, suggesting that virus that bound to the surface of CD4(-) cells is efficiently passed to CD4(+) T cells during cell-cell adhesion. These studies show that HIV binds at relatively high levels to CD4(-) cells and, once bound, is highly infectious for T cells. This suggests that virus binding to the surface of CD4(-) cells is an important route for infection of T cells in vivo.

Association of indicators of bacterial vaginosis with a female genital tract factor that induces expression of HIV-1.

OBJECTIVE: The aim of this study was to determine the relationship of bacterial vaginosis and bacterial vaginosis-associated microorganisms with an HIV-inducing factor (HIF) found in cervicovaginal lavage. DESIGN: A total of 26 cervicovaginal lavage specimens collected from 17 women were used in this study to determine if HIF was significantly associated with features consistent with bacterial vaginosis. METHODS: Patients were evaluated for various clinical features including age, HIV status and stage, CD4 cell counts, clinical diagnosis of gynecological infections, vaginal pH, Gram stains of vaginal fluid, phase of menstruation, and presence of cervical dysplasia. Cervicovaginal lavage specimens were analyzed for the presence of HIF by U1 bioassay. The presence of Gardnerella vaginalis, and general Mycoplasmataceae, and specifically Mycoplasma hominis, Ureaplasma urealyticum, M. fermentans, M. genitalium in cervicovaginal lavage were determined by semiquantitative PCR. RESULTS: Eleven cervicovaginal lavage samples from seven women were HIF-positive and 15 cervicovaginal lavage samples from 11 women were HIF-negative (patient No. 8 had two HIF-negative cervicovaginal lavage and one HIF-positive cervicovaginal lavage). The following parameters were significantly associated with HIF: abnormal vaginal fluid pH (>4.5) (P = 0.006), Gram stains indicative of bacterial vaginosis (P = 0.007), normal menstrual cycle (P = 0.0007) and PCR detection and relative quantity of M. hominis (P = 0.0003, P = 0.002). CONCLUSIONS: This study indicates that HIF is closely associated with features of bacterial vaginosis.

Bacterial vaginosis-associated microflora isolated from the female genital tract activates HIV-1 expression.

Alteration of cervicovaginal microbial flora can lead to vaginosis, which is associated with an increased risk of HIV-1 transmission. We recently characterized a soluble HIV-inducing factor (HIF) from the cervicovaginal lavage (CVL) samples of women. The goals of this study were to determine the effect of cervicovaginal microflora on HIV-1 expression and to elucidate the relationship between HIF activity and microflora. Physiologically relevant microorganisms, Mycoplasma, diphtheroid-like bacteria, Gardnerella vaginalis, Streptococcus agalactiae, and Streptococcus constellatus, cultured from the CVL of a representative woman with a clinical condition of bacterial vaginosis and possessing HIF activity, induced HIV-1 expression. The magnitude of virus induction varied widely with the greatest stimulation induced by diphtheroid-like bacteria and Mycoplasma. The transcriptional induction by Mycoplasma was mediated by activation of the KB enhancer, an activation mechanism shared with HIF. Also as with HIF, Mycoplasma induced AP-1 dependent transcription. Polymerase chain reaction (PCR)-based speciation showed that the isolate was M. hominis. Our data indicate that bacterial vaginosis-associated microflora can enhance HIV-1 transcription and replication and identify M. hominis as a potential source for HIF activity. The virus-enhancing activities associated with the microflora and HIF may increase genital tract viral load, potentially contributing to HIV transmission.