Variations in CD4 Expression by Human Monocytes and Macrophages and Their Relationship to Infection with the Human Immunodeficiency Virus

Abstract

SUMMARYThe expression of CD4 antigen on the surface of LeuM3-positive human blood monocytes was found to be variable with 65 to 90~ of cells from 46 normal human volunteers being positive by dual staining flow cytometry. When monocytes adhered to plastic (but not when cultured on Teflon), a marked decrease in CD4 expression was observed between 1 and 24 h post-adherence. CD4 expression could not be detected in macrophages adhered to plastic for 5 days by using four anti-CD4 monoclonal antibodies in flow cytometry or direct immunofluorescence. Conversely an increasing proportion of adherent cells expressed LeuM3 and OKM5 surface antigens over the 5 days. CD4 mRNA levels were measured by slot-blot and Northern hybridization, and total cellular CD4 protein levels by immunoprecipitation. Both cellular mRNA and 'CD4 levels remained constant throughout the 5 day period but membrane CD4 protein levels were greatly reduced indicating that the down-regulation of CD4 was posttranslational. Infection with two of six fresh human immunodeficiency virus (HIV) isolates showed different kinetic patterns when tested on purified monocytes recently adhered to plastic and macrophages adherent for 5 days. HIV antigen and reverse transcriptase levels in infected monocyte cultures remained high for 3 to 4 weeks before detachment and necrosis of the cells occurred. Infection of macrophages generated much lower levels of antigen and reverse transcriptase which declined to very low or undetectable levels over 2 weeks, leaving persisting viable macrophages. One week after infection HIV nucleic acid was detected in 69 + 7~ of monocytes and 6 + 3~ of macrophages by in situ hybridization. Blocking experiments with anti-Leu3a monoclonal antibody suggested that HIV infection of 5 day adherent macrophages occurred mainly by a mechanism other than binding to CD4.

Recombinant interleukin 4 stimulates human immunodeficiency virus production by infected monocytes and macrophages

“…Aliquots (150 ml) of blood were obtained from healthy HIV seronegative volunteers. Monocytes were separated as described previously (Kazazi et al, 1989). Briefly, after Ficoll-Hypaque separation, blood mononuclear cells were separated into eight fractions by countercurrent elutriation in a Beckman J2-21 centrifuge fitted with a JE6B elutriation rotor (Beckman Instruments).…”

“…Pure populations of macrophages were obtained by allowing the monocytes to differentiate and enlarge for 5 days in cluster well plates (Nunc); contaminating T or B lymphocytes detached during this period (Cunningham & Merigan, 1984;Kazazi et al, 1989). These cultures were compared with cultures of monocytes purified by centrifugal elutriation and complementdependent cytotoxicity, grown on plastic or in Teflon jars (Savillex) and allowed to mature for 5 days.…”

“…In addition, the marked biological differences between HIV infection of monocyte/macrophages and CD4 ÷ lymphocytes are also well described. For example, in contrast to lymphocytes, productive HIV infection of monocyte/macrophages does not require a cellular activation step, is predominantly intracellular (within vacuoles) and is not associated with marked c.p.e, in macrophages (Gartner et al, 1986;Nicholson et al, 1986;Gendelman et al, 1988;Kazazi et al, 1989). Factors that modulate HIV infection of mononuclear 0001-0510 © 1992 SGM phagocytes may influence the local production of virus, the function of infected monocytes/macrophages, or their production of toxic or biologically active molecules.…”

CCR5 Expression and β-Chemokine Production During Placental Neonatal Monocyte Differentiation

“…The degree of susceptibility to HIV Bal infection was clearly associated with the stage of differentiation of CM during in vitro culture. The increased susceptibility to HIV infection by macrophages during in vitro differentiation is not related to the expression of CD4 receptors (1,(27)(28)(29). In fact, CD4 expression on both cord and adult MDM was decreased at time (7-10 d) of HIV infection (1).…”

Effect of a recombinant HIV gpl60 vaccine on monokine production

“…Since CD4 receptor expression may decrease upon culture (Kazazi et al, 1989), assays were performed to establish that CD4 receptors were expressed on the THP-1 monocytic cell line. Indirect immunofluorescence using murine monoclonal anti-OKT4 revealed that 92% ofthe THP-1 cells were CD4 positive.…”