To define better the human immune response to individual structural proteins of human cytomegalovirus (HCMV), 55 human sera with different IgG and IgM titres were studied for their reactivity with HCMV structural polypeptides separated by SDS-PAGE and electrotransferred to nitrocellulose paper. The results obtained showed that antibody titres detected by immunoassay correlate with the intensity and the number of polypeptides reacting by immunoblotting (IB). The IB profiles of HCMV polypeptides reacting with different sera having the same antibody titres show considerable variation. Sera with high levels of IgG antibody and that are IgM-positive frequently react with 155, 149, 82.5, 74.5, 67, 57, 55, 38.5, and 28 kD polypeptides; all these sera react with 155, 67, 57, 55, 38.5 kD polypeptides. Sera with high levels of IgG antibody but that are IgM negative frequently react with all these polypeptides, with the exception of 149 and 74.5. Only 155 and 28 kD polypeptides were recognized by all sera of this group. The sera with moderate levels of IgG antibody preferentially recognize 155, 110, 82.5, 62, 55, 38.5 and 28 kD polypeptides. The sera with low levels of antibody reacted especially with 155 and 62 kD polypeptides. IgM antibody seems to recognize preferentially 155, 110, 67, 57, 55, 38.5 kD polypeptides.

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Several HIV-1 infected patients show bone loss and osteopenia/osteoporosis during the course of disease. The mechanisms underlying this degenerative process are largely unsettled and it has not been determined yet whether bone dysfunction is linked to HIV-1-mediated direct and/or indirect effects on osteoblasts/osteoclasts cross-talk regulation. This study investigated the effects of HIV-1(IIIb) and HIV-1(ADA) strains on osteoblasts using the osteoblast-derived cell line (HOBIT) and primary human osteoblasts as cellular models. The challenge of these cell cultures by both HIV-1 strains triggered a significant apoptosis activation unrelated to viral infection, since proviral HIV-1 DNA and supernatant HIV-1 RNA were not detected by real time PCR or b-DNA assays respectively. Under the experimental conditions, even heat-inactivated HIV-1 or cross-linked recombinant gp120 treatment of HOBIT and osteoblasts induced programmed cell death, suggesting that apoptosis is regulated by the interaction between HIV-1 gp120 and cell membrane. The analysis of cell culture supernatants showed a significant up-regulation of TNFalpha, a pleiotropic protein considered an apoptosis inducer in the osteoblast model. In fact, pretreatment of HOBIT and osteoblast cell cultures with anti-TNFalpha polyclonal antibody tackled effectively HIV-1 related induction of cell apoptosis. As a whole, these results indicate that HIV-1 may impair bone mass structure homeostasis by TNFalpha regulated osteoblast apoptosis.

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