The mechanisms linking human immunodeficiency virus replication to the progressive immunodeficiency of acquired immune deficiency syndrome are controversial, particularly the relative contribution of CD4+ T cell destruction. Here, we used the simian immunodeficiency virus (SIV) model to investigate the relationship between systemic CD4+ T cell dynamics and rapid disease progression. Of 18 rhesus macaques (RMs) infected with CCR5-tropic SIVmac239 (n = 14) or CXCR4-tropic SIVmac155T3 (n = 4), 4 of the former group manifested end-stage SIV disease by 200 d after infection. In SIVmac155T3 infections, naive CD4+ T cells were dramatically depleted, but this population was spared by SIVmac239, even in rapid progressors. In contrast, all SIVmac239-infected RMs demonstrated substantial systemic depletion of CD4+ memory T cells by day 28 after infection. Surprisingly, the extent of CD4+ memory T cell depletion was not, by itself, a strong predictor of rapid progression. However, in all RMs destined for stable infection, this depletion was countered by a striking increase in production of short-lived CD4+ memory T cells, many of which rapidly migrated to tissue. In all rapid progressors (P < 0.0001), production of these cells initiated but failed by day 42 of infection, and tissue delivery of new CD4+ memory T cells ceased. Thus, although profound depletion of tissue CD4+ memory T cells appeared to be a prerequisite for early pathogenesis, it was the inability to respond to this depletion with sustained production of tissue-homing CD4+ memory T cells that best distinguished rapid progressors, suggesting that mechanisms of the CD4+ memory T cell generation play a crucial role in maintaining immune homeostasis in stable SIV infection.

Sixteen isolates of simian retrovirus closely related to human immunodeficiency virus (HIV) were obtained from healthy African green monkeys (AGM) (Cercopithecus aethiops). The first isolate was obtained from a monkey seropositive for HIV, and the others were isolated from monkeys harboring antibodies to the first isolate. These simian retroviruses were referred to as simian immunodeficiency virus from AGM, SIV[AGM], due to their cross-reactivities with HIV structural proteins. These SIV[AGM] isolates were found by Western blotting analysis to have virus-specific proteins of 120, 66, 55, 32-40, 24 and 17 kDa, which were all similar in size to the analogous proteins of HIV. Putative gag proteins of p55, p24 and p17 were recognized by sera of human AIDS patients, but the corresponding env proteins of 32-40 and 120 kDa showed only weak cross-reactivity with those of HIV. The transmembrane glycoproteins of these 3 SIV[AGM] isolates showed size heterogeneity, being 32, 35 and 40 kDa. This virus had particles that were morphologically similar to those of HIV, and had Mg2+-dependent reverse transcriptase. Furthermore, the SIV[AGM] showed tropism and cytopathic effects on CD4-positive human cell lines. In a sero-epidemiological survey of SIV[AGM] in various non-human primates, 2 other African monkey species, the mandrill and de Brazza's monkey, were also found to have antibodies to SIV[AGM]. These HIV-related simian retroviruses will be important in determining the origin and transmission of HIV group viruses, and may provide useful animal models for studies on the infection and pathogenesis of HIV and AIDS.

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Nef is an HIV-1 accessory protein essential for AIDS progression and an attractive target for drug discovery. Lack of a catalytic function makes Nef difficult to assay in chemical library screens. We developed a high-throughput screening assay for inhibitors of Nef function by coupling it to one of its host cell binding partners, the Src-family kinase Hck. Hck activation is dependent upon Nef in this assay, providing a direct readout of Nef activity in vitro. Using this screen, a unique diphenylfuropyrimidine was identified as a strong inhibitor of Nef-dependent Hck activation. This compound also exhibited remarkable antiretroviral effects, blocking Nef-dependent HIV replication in cell culture. Structurally related analogs were synthesized and shown to exhibit similar Nef-dependent anti-viral activity, identifying the diphenylfuropyrimidine substructure as a new lead for antiretroviral drug development. This study demonstrates that coupling non-catalytic HIV accessory factors with host cell target proteins addressable by high-throughput assays may afford new avenues for the discovery of anti-HIV agents.

The iron rust phase was analyzed by using the in-situ x-ray diffraction (XRD) and alternating current (AC) impedance methods after a wet/dry corrosion test using sodium chloride (NaCl) solution, which is the main composition of airborne saline particles. The corrosion content of the carbon steel depended on the concentration of Cl ions in the environment of the test chamber. As the concentration of Cl ions increased, the content of β-FeOOH increased in iron rust phases. The transition of β-FeOOH from the green rust I (GRI) was observed directly by in-situ XRD. The amount of GRI depended on the concentration of Cl ions, and β-FeOOH was transformed from GRI automatically in the dry process of the test. AC impedance showed that the resistance of the rust (Rrust) increased with the number of cycles in the corrosion test, and that the structural factor of the rust became predominant in Rrust. With the increase of the amount of rust, the resistance corresponding to the corrosion rate (Rt decreased, which was related to the reduction of β-FeOOH in the rust phase.

Previously, we have reported that a serial passage of 83P-5 strain of porcine epidemic diarrhea virus (PEDV) in Vero cells resulted in a growth adaptation of the virus in cultured cells at the 22nd passage. In this study, we further maintained the 83P-5 in Vero cells up to the 100th passage and analyzed changes in the spike (S), membrane (M), and nucleocapsid (N) gene sequences and pathogenicity of the virus at the 34th, 61st, and 100th passage levels. Sequence analyses revealed a strong selection for the S gene of 83P-5 in Vero cells, and virtually all mutations occurring at the 34th and 61st passages had been carried over to the 100th-passaged virus. In contrast, the viral M and N genes showed a strong conservation during the serial passage. Pigs experimentally infected with the 34th- or 61st-passaged virus, but not the 100th-passaged virus, exhibited diarrhea, indicating an attenuation of the 83P-5 at the 100th passage. Interestingly, S protein of the attenuated 100th-passaged 83P-5 showed a remarkable sequence similarity to that of previously reported DR-13 strain of attenuated PEDV that also had been established by serial passage in Vero cells. Further studies will be required to define whether the mutations in the S gene of 83P-5 that had been selected and accumulated during the serial passages are indeed the causalities of the growth adaptation in vitro and the attenuation of virulence in vivo.

Rhesus monkeys were immunizd by multiple inoculations with purified, disrupted, noninfectious sinmian immunodeficiency virus (SIV) in adjuvant. Immunized monkeys developed anti-SIV antibodies detectable by whole-virus ELISA and by immunoblot reactivity; these antibodies had weak neutralizing activity. One week after the last immuniza-

The location of the translational termination codon for the transmembrane protein (TMP) varies in three infectious molecular clones of simian immunodeficiency virus from macaques (SIVmac). The SIV.aC251 and SIVmaC142 infectious clones have premature stop signals that differ in location by one codon; transfection of these DNAs into human HUT-78 cells yielded virus with a truncated TMP (28 to 30 kilodaltons [kDa]).