Randal A. Byrn

Production of tumor necrosis factor alpha and interleukin 1 beta by monocytic cells infected with human immunodeficiency virus.

The production of tumor necrosis factor alpha (TNF alpha) and IL-1 beta by the monocytic cell line THP-1, productively infected with HIV-1, was investigated using specific RIA and Northern blot analysis. HIV-infected cells, like uninfected cells, did not constitutively produce any detectable amounts of protein or mRNA for TNF alpha or IL-1 beta. After stimulation with LPS or a combination of LPS plus IFN-gamma, TNF alpha and IL-1 beta were detected in tissue culture supernatants and cell lysates and transcripts for both cytokines were seen on Northern blots. No significant difference in production of these two cytokines was observed between uninfected and chronically infected cells. Acutely HIV-infected cells, however, showed phenotypic changes compatible with maturation and an increase in TNF alpha and IL-1 beta mRNA production, and released significantly higher levels of TNF alpha and IL-1 beta compared with chronically infected or uninfected cells. Furthermore, LPS stimulation of HIV-infected cells increased virus production. These results suggest that HIV-infected monocytic cells may produce increased amounts of TNF alpha and IL-1 beta in response to stimuli that could be present in vivo.

The regulation of HIV by retinoic acid correlates with cellular expression of the retinoic acid receptors

ObjectivesTo analyze the effect of retinoic acids (RA) on HIV-1 expression and correlate this effect with expression levels of RA receptors (RARs) in T-lymphoid and monocytoid cell lines. Design and methodsThe effect of all-trans and 9-cis RA on HIV-1 production in T-lymphoid (H9,CEM) and monocytoid (U937/THP-1) cell lines was measured during acute and chronic infection. The expression levels of human RARa (hRARa, receptor for all-trans RA) and the human retinoid-X receptor a (hRXRa receptor for 9-cis RA) were determined by Northern blot analysis. ResultsBoth all-trans and 9-cis RA inhibited virus replication in HIV-1 IIB-infected monocytoid cells, in the presence and absence of the co-stimulatory agent phorbol myristate acetate (PMA). The retinoids had weak or no stimulatory effects on HIV production by T-cell lines. HIV production by PMA-stimulated T-cell lines was inhibited by these retinoids. The 9-cis RA was generally more effective than all-trans RA in inhibiting HIV production and in combination generally more effective than the single agents alone. Human RARa was expressed in H9, U937 and THP-1 cells, but almost undetectable in CEM cells. Human RXRa was significantly expressed in U937 and THP-1 cells, weakly expressed in H9 cells and not detectable in CEM cells. After stimulation by PMA, RXRa expression increased in H9 and U937 cells but not in CEM cells. Human RARa expression was unchanged in H9 and CEM cells, and elevated in U937 cells, after PMA stimulation. ConclusionThe effect of RA on HIV-1 expression was cell-type-dependent and partially correlated with cellular expression of RARs. Endogenous or exogenously administered RA may have a significant role in HIV regulation.

Comparison of the immune response to recombinant gp120 in humans and chimpanzees

ObjectiveTo assess similarities and differences in antibody responses to recombinant (r) HIV-1IIIMB gp120 in chimpanzees, previously protected from HIV-1 infection, and human volunteers immunized in connection with a Phase I clinical trial. MethodsFrozen sera from humans immunized with rgp120 from HIV-IIIB and chimpanzees immunized with the same antigen or recombinant soluble gp160 were compared in a variety of serologic assays. ResultsThe magnitude of the antibody response to gp120 was similar in both species; however, the half-life of the antibody response to rgp120 was approximately 4.5 times longer in humans (9 weeks) than in chimpanzees (2 weeks). Antibodies to gp120 in both species were broadly cross-reactive with gp120 from diverse isolates of HIV-1 and were effective in blocking the binding of gp120 to CD4. Antibody binding to native gp120 was greater than to denatured gp120 in both species. Antibody responses to the principal neutralizing determinant (V3 domain) and virus neutralization titers were approximately 10-fold lower in humans than chimpanzees. The relative avidity of antibody binding to gp120 was higher in the sera from the immunized chimpanzees than in the immunized humans. ConclusionsWhile the antibody responses to rgp120 elicited in man and chimpanzees were in many ways similar, significant differences did occur. Predictions made on the basis of chimpanzee immunogenicity studies overestimated the potency of the virus neutralizing titers and under-estimated the duration of the antibody response achieved in humans.