Sequential immunization of macaques with two differentially attenuated vaccines induced long-term virus-specific immune responses and conferred protection against AIDS caused by heterologous simian human immunodeficiency Virus (SHIV(89.6)P)

Four rhesus macaques were sequentially immunized with live vaccines DeltavpuDeltanefSHIV-4 (vaccine-I) and Deltavpu SHIV(PPC) (vaccine-II). The vaccine viruses did not replicate productively in the peripheral blood mononuclear cells (PBMCs) of the vaccinated animals. All four animals developed binding antibodies against both the vaccine-I and -II envelope glycoproteins but neutralizing antibodies only against vaccine-I. They developed vaccine virus-specific CTLs that also recognized homologous as well as heterologous pathogenic SHIVs. Thirty weeks after the last immunization, the vaccinated animals and three unvaccinated control animals were challenged iv with a highly virulent heterologous SHIV(89.6)P. As expected, the three unvaccinated control animals developed large numbers of infectious PBMCs, high plasma viremia, and precipitous loss of CD4(+) T cells. Two controls did not develop any immune response and succumbed to AIDS in about 6 months. The third control animal developed neutralizing antibodies and had a more chronic disease course, but eventually succumbed to AIDS-related complications 81 weeks after inoculation. The four vaccinated animals became infected with challenge virus as indicated by the presence of challenge virus-specific DNA in the PBMCs and RNA in plasma. However, virus in these animals replicated approximately 200- to 60,000-fold less efficiently than in control animals and eventually, plasma viral RNA became undetectable in three of the four vaccinates. The animals maintained normal CD4(+) T-cell levels throughout the observation period of 85 weeks after a transient drop at Week 3 postchallenge. They also maintained CTL responses throughout the observation period. These studies thus showed that the graded immunization schedule resulted in a safe and highly effective long-lasting immune response that was associated with protection against AIDS by highly pathogenic heterologous SHIV(89.6)P.

[Preliminary analysis of the hemoglobin levels of children under 6 years of age]

Among the 40 survey sites in the "China Food and Nutrition Surveillance Project", we picked six sites to estimate the Levels of preschool children and collected 2416 valid cases. Our analysis formed the following results: Children anemia prevalence level was 16.8%, which was higher than the figure from the "Third National Nutrition Survey in 1992", and was lower than that from the Nutrition Surveillance and Improvement Project in 101 poor countries". The situation where the anemia prevalence was above 20% existed not only in poor rural villages, but also in other rural areas in general as well as cities. Looking at different age structures, we found that the anemia prevalence level was the highest for children aged six to twelve months. The number was as high as 30.90%, consistent with results from many earlier research projects.

Evaluation of immune responses induced by HIV-1 gp120 in rhesus macaques: effect of vaccination on challenge with pathogenic strains of homologous and heterologous simian human immunodeficiency viruses

The simian human immunodeficiency virus (SHIV) macaque model of AIDS has provided a very useful system for evaluation of envelope-based candidate vaccines against HIV-1. Eight rhesus macaques were immunized with monomeric recombinant gp120 of HIV-1(LAI) (rgp120) and used to evaluate whether this vaccine conferred protection against challenge with pathogenic SHIVs (SHIV(KU-2) and SHIV(89.6)P). The vaccinated macaques developed high titers of antibodies against rgp120 that reacted efficiently with the envelope proteins of homologous SHIV (SHIV(KU-2)) and poorly with the SHIV(89.6)P envelope, a heterologous strain of SHIV. This vaccine also induced neutralizing antibodies but only against SHIV(KU-2). Vaccine-induced antibodies were of high avidity and predominantly against linear epitopes on the protein. Vaccinated macaques developed gp120-specific T-helper cells but no consistent cytotoxic T lymphocytes. However, cellular immune responses were short-lived in all eight vaccinates. At week 22 postimmunization, four vaccinates were challenged with SHIV(KU-2) and the other four with SHIV(89.6)P. Four unvaccinated control macaques were also infected: two with SHIV(KU-2) and two with SHIV(89.6)P. Vaccinated macaques generally showed anamnestic antibody and T-helper cell responses. However, T-helper responses were again short-lived. Upon challenge, the level of productive virus replication was indistinguishable between vaccine and control groups, suggesting that rgp120 did not confer protection against virus replication when animals were challenged with homologous or heterologous SHIV viruses.

Neuropathogenesis of chimeric simian human immunodeficiency virus infection in rhesus macaques

Comparative studies were performed to determine the neuropathogenesis of infection in macaques with simian human immunodeficiency virus (SHIV)89.6P and SHIV(KU). Both viruses utilize the CD4 receptor and CXCR4 co-receptor. However, in addition, SHIV89.6P uses the CCR5 co-receptor. Both agents are dual tropic for CD4+ T cells and blood-derived macrophages of rhesus macaques. Following inoculation into macaques, both caused rapid elimination of CD4+ T cells but they varied greatly in mechanisms of neuropathogenesis. Two animals infected with SHIV89.6P developed typical lentiviral encephalitis in which multinucleated giant cell formation, nodular accumulations of microglial cells, activated macrophages and astrocytes, and perivascular accumulations of mononuclear cells were present in the brain. Many of the macrophages in these lesions contained viral RNA. Three macaques infected with SHIV(KU) and killed on days 6, 11 and 18, respectively, developed a slowly progressive infection in the CNS but macrophages were not productively infected and there were no pathological changes in the brain. Two other animals infected with this virus and killed several months later showed minimal infection in the brain even though one of the two developed encephalitis of unknown etiology. The basic difference in the mechanisms of neuropathogenesis by the two viruses may be related to co-receptor usage. SHIV89.6P, in utilizing the CCR5 co-receptor, caused neuropathogenic effects that are similar to other neurovirulent primate lentiviruses.

[Dietary intake of some micronutrients in different provinces of China]

Based on the data collected in 1992 China National Nutrition Survey, which covered 100,201 persons of all ages in 29 provinces, the dietary intakes of some micronutrients were calculated. The intake of calcium, retinal equivalent and riboflavin were the most insufficient nutrients; zinc, selenium and thiamin were close to (80%-90%) of Chinese RDAs. The intakes of niacin, ascorbic acid and vitamin E were sufficient. The regions in the northeast, northwestern and the southeastern inland were more at risk of nutrition deficiency. Dietary intervention or food fortification with some micronutrients could be used for improving the situation.

Morphological correlates of neurological dysfunction in macaques infected with neurovirulent simian immunodeficiency virus

The pattern of neurological disease caused by human immunodeficiency virus (HIV) infection of the central nervous system (CNS) was investigated using a macaque model of acquired immune defiency syndrome (AIDS). Seven of nine macaques inoculated with neurovirulent simian imunodeficiency virus (SIVmac ) developed AIDS within 3 months. Four of these had clinically obvious neurological disease and extensive conduction defects in the form of latency increases in evoked potential (EP) responses. Neuropathologically, all four animals had disseminated white matter disease in the form of multifocal, perivascular and nodular parenchymal mononuclear cell infiltrates, along with extensive involvement of the cortical grey matter, leptomeninges and intracranial portions of cranial nerves. A brisk multinucleated giant cell (MGC) response was a frequent accompaniment in the affected areas. Three of the animals in this group also showed spongiform vacuolation in the occipital grey matter, a lesion described only rarely in HIV encephalitis. In the remaining three animals, there was only minimal evidence of overt neurological impairment or conduction defects. These animals had only mild to moderate neuropathological changes and lesions were virtually confined to the white matter regions of the brain. MGC responses were rare or absent in the CNS of these animals. Neuropathological findings in this SIVmac model have therefore shown good correlation with the severity of clinical and neurophysiological changes, and are reminiscent of HIV-1 encephalitis. More importantly, white matter involvement was a consistent finding in the affected macaques, regardless of the duration and severity of disease, or type of virus inoculated, suggesting an unusual susceptibility for lentiviral infection in these regions of the macaque CNS.

[Effect of nutrition on the health improvement of preschool children in rural areas]

"Surveillance and Improvement of Children's Nutrition" is the largest project in connection with the nutrition of preschool children in China up to now. It focused on nutrition improvement of preschool children in rural areas. The results of the baseline survey and the project final evaluation surveys showed that the nutritional status of children was improved from 1990 to 1995. The prevalence of moderate and severe stunting and underweight at the national level decreased by 23.1% and 28.6% respectively. Anemia decreased by 48%. It was identified that the benefits of nutrition improvement were associated with nutrition education and other integrated nutrition interventions, e.g., improvement the dietary habit of the target children.

[The value of 99mTc-sulfer colloid bone marrow scintigraphy in differential diagnosis of aplastic anemia]

OBJECTIVE

To diagnose equivocal aplastic anemia(AA) patients by the combination of clinical data and bone marrow scintigraphy.

METHODS

Bone marrow scintigraphy using 99mTc-sulfer colloid 370-550 MBq was analysed in 47 patients, including 28 cases of AA, 12 of myelodysplastic syndromes(10 MDS-RA and 2 MDS-RAEB) and 7 of AA-PNH syndrome.

RESULTS

Pancytopenia, hypercellular bone marrow associated with uneven disappearance of marrow image or focal hematopoiesis were found in 28 AA and 2 of 30 MDS-RA cases. Marrow imaging showed uneven low accumulation of radioactivity in 12 and focal patterns in 18 patients. Normal or high activity and expanded periphery of bone marrow was found in MDS patients (8 RA and 2 RAEB cases). Changes of activity and distribution of bone marrow during the transforming course were noticed in 4 AA-PNH syndrome patients.

CONCLUSIONS

Patch distribution and focal hemopoiesis is the outstanding features of AA marrow. The imaging features as well as expanded manner and increased activity of bone marrow are helpful to the differential diagnosis, evaluation of clinical status and explanation of marrow aspirate results.

Characterization of a neutralization-escape variant of SHIVKU-1, a virus that causes acquired immune deficiency syndrome in pig-tailed macaques

A chimeric simian-human immunodeficiency virus (SHIV-4) containing the tat, rev, vpu, and env genes of HIV type 1 (HIV-1) in a genetic background of SIVmac239 was used to develop an animal model in which a primate lentivirus expressing the HIV-1 envelope glycoprotein caused acquired immune deficiency syndrome (AIDS) in macaques. An SHIV-infected pig-tailed macaque that died from AIDS at 24 weeks postinoculation experienced two waves of viremia: one extending from weeks 2-8 and the second extending from week 18 until death. Virus (SHIVKU-1) isolated during the first wave was neutralized by antibodies appearing at the end of the first viremic phase, but the virus (SHIVKU-1b) isolated during the second viremic phase was not neutralized by these antibodies. Inoculation of SHIVKU-1b into 4 pig-tailed macaques resulted in severe CD4(+) T cell loss by 2 weeks postinoculation, and all 4 macaques died from AIDS at 23-34 weeks postinoculation. Because this virus had a neutralization-resistant phenotype, we sequenced the env gene and compared these sequences with those of the env gene of SHIVKU-1 and parental SHIV-4. With reference to SHIV-4, SHIVKU-1b had 18 and 6 consensus amino acid substitutions in the gp120 and gp41 regions of Env, respectively. These compared with 10 and 3 amino acid substitutions in the gp120 and gp41 regions of SHIVKU-1. Our data suggested that SHIVKU-1 and SHIVKU-1b probably evolved from a common ancestor but that SHIVKU-1b did not evolve from SHIVKU-1. A chimeric virus, SHIVKU-1bMC17, constructed with the consensus env from the SHIVKU-1b on a background of SHIV-4, confirmed that amino acid substitutions in Env were responsible for the neutralization-resistant phenotype. These results are consistent with the hypothesis that neutralizing antibodies induced by SHIVKU-1 in pig-tailed macaque resulted in the selection of a neutralization-resistant virus that was responsible for the second wave of viremia.

Passively administered neutralizing serum that protected macaques against infection with parenterally inoculated pathogenic simian-human immunodeficiency virus failed to protect against mucosally inoculated virus

Macaques inoculated orally, vaginally, or parenterally with SHIV(KU-1) develop severe systemic infection, acute loss of CD4+ T cells, and AIDS. We showed in a previous report that passive immunization with neutralizing serum protected macaques against infection with parenterally inoculated pathogenic SHIV given 24 hr later. In the study reported here we asked whether the identical passive immunization protocol would protect macaques against infection with pathogenic SHIV following oral inoculation of the virus. Ten pigtail macaques were inoculated orally with one animal infectious dose of SHIV(KU-1). Four of the 10 had been given pooled anti-SHIV plasma (15 ml/kg) 24 hr earlier, 4 others were given the same dose of anti-SHIV plasma 2 hr after virus challenge, and the 2 remaining animals were used as controls. The neutralizing antibodies failed to protect macaques against infection after mucosal challenge with SHIV(KU-1).

Oral immunization of macaques with attenuated vaccine virus induces protection against vaginally transmitted AIDS

The chimeric simian-human immunodeficiency virus SHIVKU-1, bearing the envelope of human immunodeficiency virus type 1 (HIV-1), causes fulminant infection with subtotal loss of CD4(+) T cells followed by development of AIDS in intravaginally inoculated macaques and thus provides a highly relevant model of sexually transmitted disease caused by HIV-1 in human beings. Previous studies using this SHIV model had shown that the vpu and nef genes were important in pathogenesis of the infection, and so we deleted portions of these genes to create two vaccines, DeltavpuDeltanefSHIV-4 (vaccine 1) and DeltavpuSHIVPPc (vaccine 2). Six adult macaques were immunized subcutaneously with vaccine 1, and six were immunized orally with vaccine 2. Both viruses caused infection in all inoculated animals, but whereas vaccine 1 virus caused only a nonproductive type of infection, vaccine 2 virus replicated productively but transiently for a 6- to 10-week period. Both groups were challenged 6 to 7 months later with pathogenic SHIVKU-1 by the intravaginal route. All four unvaccinated controls developed low CD4(+) T-cell counts (<200/microliter) and AIDS. The 12 vaccinated animals all became infected with SHIVKU-1, and two in group 1 developed a persistent productive infection followed by development of AIDS in one. The other 10 have maintained almost complete control over virus replication even though spliced viral RNA was detected in lymph nodes. This suppression of virus replication correlated with robust antiviral cell-mediated immune responses. This is the first demonstration of protection against virulent SHIV administered by the intravaginal route. This study supports the concept that sexually transmitted HIV disease can be prevented by parenteral or oral immunization.

Neutralizing antibodies administered before, but not after, virulent SHIV prevent infection in macaques

By subcutaneous inoculation of SHIV(KU-2) in the hands of macaques, we developed a model of human immunodeficiency virus type-1 (HIV-1) occupational infection due to needle-stick injury and used the model to determine whether neutralizing serum to SHIV administered before or after virus inoculation could either prevent or abort infection, respectively. Six rhesus macaques were given 15 ml/kg pooled anti-SHIV plasma and challenged 24 hr later with approximately 300 animal infectious doses of SHIV(KU-2), subcutaneously. Three of the six macaques completely resisted infection with SHIV(KU-2). A fourth animal failed to yield infectious virus, but DNA extracted from its peripheral blood mononuclear cells (PBMC) and lymph nodes had viral sequences. Partial resistance was noted in the other two animals because virus recovery was delayed compared with the control animals. In contrast, six of six macaques given the same dose of anti-SHIV plasma 18 hr after exposure to virus became infected, as did two of two macaques given anti-SHIV plasma only 2 hr after exposure to virus. Our results suggest that neutralizing antibodies may have a prophylactic but not a therapeutic role in HIV-1 infections.

Failure of SIVmac to be neutralized in macrophage cultures is unique to SIVmac and not observed with neutralization of SHIV or HIV-1

Except during acutely lethal infection, macaques infected with SIVmac251 produce antibodies that neutralize the virus in CEMx174 cells, macaque PBMC and macrophage cultures. In a previous report, we had shown that whereas neutralization of the SIVmac251 was complete in lymphocyte cultures, "protected" macrophages had actually become latently infected, and remained viral DNA-positive, but the infection was nonproductive as long as antibodies were maintained in the medium. Removal of the antibodies as long as 1 week later, resulted in resurgence of virus replication. In the present study, we compared neutralization of SIVmac239 with that of neutralization of SHIV and HIV-1, and sought to determine whether the failure to prevent infection in macrophages was also typical of neutralization of SHIV and HIV-1 in macaque and human macrophage cultures, respectively. The results showed that similar to SIVmac251, neutralizing antibodies did not block SIVmac239 infection in macaque macrophages, although they blocked infection of the virus in T cells. The data from neutralization of SHIV using anti-SHIV antibodies and for neutralization of HIV-1 (89.6 and Bal) using anti-HIV IgG in both T cells and macrophages, however, can be summarized with a single statement: neutralization of SHIV and HIV-1 was complete in all of the cultures, with no evidence of establishment of latent infection in or resurgence of virus replication after antibodies were removed from macrophage cultures. The non-neutralizability of SIVmac (251 and 239) in macrophages is therefore unique to the SIVmac and not relevant to neutralization of HIV-1.

Chimeric SHIV that causes CD4+ T cell loss and AIDS in rhesus macaques

By animal to animal passage in rhesus and pig-tailed macaques, we developed a rhesus model of HIV-1 disease in humans. Rhesus macaques infected with a cell-free stock of SHIVKU-2 developed CD4+ T cell loss, primary lentiviral encephalitis and pneumonia, and AIDS. Six of nine rhesus macaques died within eight months post-inoculation, while the remaining three are at five, five, and eight months post-inoculation, respectively. Animals infected by either mucosal or parenteral routes of infection had a similar course of infection.

Characterization of the pathogenic KU-SHIV model of acquired immunodeficiency syndrome in macaques

By animal-to-animal passage in macaques we derived a pathogenic chimeric simian-human immunodeficiency virus (SHIV) that caused CD4+ T cell loss and AIDS in pigtail macaques and used it to inoculate 20 rhesus and pigtail macaques by the intravaginal and intravenous routes. On the basis of the outcome of infection and patterns of CD4+ T cell loss and viral load, disease was classified into four patterns: acute, subacute, chronic, and nonprogressive infection. During the study period, 15 of the 20 animals developed fatal disease, including AIDS, encephalitis, pneumonia, and severe anemia. Opportunistic pathogens identified in these animals included Pneumocystis, cytomegalovirus, Cryptosporidium, Toxoplasma, and Candida. No single parameter by itself predicted outcome, although a combination of low CD4+ T cell counts in blood, high plasma virus levels, and presence of autoantibodies to red blood cells reliably predicted a fatal outcome. Five animals (25%) died within 3 months of inoculation and constituted the group with acute disease, whereas the nine animals (45%) with subacute disease died between 3 and 8 months postinoculation. This 70% mortality within 8 months is significantly shorter than in HIV-1-infected human beings, of whom 70% develop fatal disease a decade after infection. SHIV infection in macaques provides a useful model with which to evaluate antiviral strategies, combining all the advantages of the SIVmac system, yet using a virus bearing the envelope gene of HIV-1.

Plasmas from lymphocyte- and macrophage-tropic SIVmac-infected macaques have antibodies with a broader spectrum of virus neutralization activity in macrophage versus lymphocyte cultures

We examined plasma from macaques infected with three different phenotypes of SIVmac for their ability to neutralize the infectivity of homologous and heterologous virus in lymphocyte (CEMx174 cells or normal rhesus macaque peripheral blood lymphocytes) or normal rhesus macaque macrophage (Mphi) cultures. Similar to previous findings, we observed that some plasmas failed to neutralize or poorly neutralized the infectivity of SIVmac239 and SIVmac251(<1:20 plasma dilution) in lymphocyte cultures. In contrast, when primary rhesus Mphi cultures were used as the indicator cells, the same plasmas neutralized both viruses at high dilutions (1:200 to 1:20,000). Neutralization of virus infectivity by the various plasmas was confirmed by SIV core antigen capture assays. We excluded the possibility that this differential neutralization in Mphi was related to the differences in the ability of the virus strain to replicate in these two cell types by demonstrating that the replication efficiency of SIVmac251 in CEMx174 cells, PBMC, and Mphi cultures was very similar. The role of Fc receptors on the Mphi surface in the clearance of the virus-antibody complexes was also excluded since similar neutralizing results were obtained using whole plasmas, purified IgG antibodies, and purified Fab fragments derived from the IgG fraction of these plasmas. The mechanism of virus neutralization in Mphi does not appear to involve blocking of virus entry into the cells since radiolabeled virus reacted with anti-SIV antibodies was taken up by rhesus Mphi as efficiently as virus reacted with normal antibody. DNA of the neutralized virus was identified in the Mphi cultures, but virus replication, as evidenced by accumulation of viral protein products, was not detectable so long as the antibodies were present in the medium. Removal of the antibodies resulted in a resumption of virus replication in the Mphi. These results indicate that virus infectivity can be efficiently neutralized by antibodies in Mphi cultures by a mechanism that is fundamentally different from that in lymphocyte cultures.

Interaction of virion protein Vpr of human immunodeficiency virus type 1 with cellular transcription factor Sp1 and trans-activation of viral long terminal repeat

Acquired immunodeficiency syndrome (AIDS) is a result of replication of the human immunodeficiency virus type 1 (HIV-1) predominantly in CD4+ T lymphocytes and macrophages. However, most of these cells in vivo are immunologically quiescent, a condition restricting HIV-1 replication. Vpr is an HIV-1 virion protein suspected to enhance HIV-1 replication in vivo. We demonstrate in this report that Vpr specifically activates HIV-1 long terminal repeat (LTR)-directed transcription. This effect is most pronounced on a minimal promoter from HIV-1 LTR containing the TATA box and binding motifs for the ubiquitous cellular transcription factor Sp1. Evidence is presented that Vpr interacts with Sp1 when Sp1 is bound to the Sp1 motifs within the HIV-1 LTR Both Vpr-Sp1 interaction and Vpr trans-activation require a central Leu/Ile-rich domain in Vpr. Our findings suggest that Vpr trans-activation through Sp1 is most critical for the immediate early transcription of HIV-1 when other positive regulators, such as NF-kappa B, are limited or inactive, a condition presumably present in vivo. By interacting with Sp1, Vpr also has the potential to influence cellular gene expression and cellular functions. Thus, therapeutic approaches directed toward blocking the Vpr trans-activation function could prove valuable in treating AIDS.

Contribution of tumor necrosis factor-alpha and glucocorticoid in hydrazine sulfate-mediated protection against endotoxin lethality

Hydrazine sulfate pretreatment has previously been shown in our laboratory to protect normal mice against endotoxin and D-galactosamine-sensitized mice against both exogenous tumor necrosis factor (TNF) and endotoxin. An intact pituitary is required for manifestation of the protective effects. Further, we have demonstrated that hydrazine sulfate pretreatment specifically modulates the TNF response to lipopolysaccharide (LPS) in mouse macrophages in vitro. This in vivo study was performed to test whether a reduced TNF response and/or increased glucocorticoid response may contribute to hydrazine sulfate protection against LPS-induced lethality in vivo. The results presented here establish that hydrazine sulfate pretreatment selectively attenuates circulating TNF levels following LPS challenge. Moreover, adrenalectomy abrogates hydrazine sulfate protection but does not prevent hydrazine sulfate attenuation of circulating TNF levels in response to LPS. Hydrazine sulfate-mediated protection is, however, restored permissively by corticosterone. Thus, the mechanism by which hydrazine sulfate protects against LPS lethality in adrenalectomized mice includes TNF modulation in response to endotoxin, as well as a pivotal requirement for glucocorticoid.

[Studies on the effects of rhTNF-alpha anti-replication against EHFV and HAV in vitro]

It was demonstrated in this study that rhTNF-alpha can inhibit the replication of epidemic hemorrhagic fever virus and hepatitis A virus in tissue culture. EHFV infection produced strong fluorescence ( - +) on Vero-E6 cells after 9 days. In the rhTNF-alpha treated group, however the fluorescence was very weak (- or +/-). rhTNF-alpha also showed anti-HAV effects on 2BS cells. The fluorescence intensity on 2BS cells infected by HAV was - +, but in the rhTNF-alpha treated group, the fluorescence was negative. We observed that rhTNF-alpha inhibited EHFV antigen expression on Vero-E6 at different times (-2h, 0h, +2h). Dr. Old had recently suggested that the physiological role of rhTNF-alpha is that of a protective agent against infectious diseases, and this view is supported by our findings.

The effect of phage T7 lysozyme on the production of biologically active porcine somatotropin in Escherichia coli from a gene transcribed by T7 RNA polymerase

We have analyzed the inducible synthesis of recombinant porcine somatotropin (rPST) from the phage T7 gene 10 promotor on the vector pET3a [Rosenberg et al., Gene 56 (1987) 125-135]. Low-level synthesis of phage T7 lysozyme is crucial for high-level synthesis (40%) of rPST, which is greatly reduced if T7 lysozyme synthesis is absent or too high. The synthesis of rPST mRNA is optimized in those constructs coding for low levels of T7 lysozyme, with a reduction in mRNA levels in constructs coding for higher levels of T7 lysozyme or no lysozyme. The rPST can be readily purified following a single chromatographic step and is biologically active as determined by the tibia test following administration to hypophysectomized rats.