Elaine A. Muchmore

Human uptake and incorporation of an immunogenic nonhuman dietary sialic acid

Humans are genetically unable to produce the sialic acid N-glycolylneuraminic acid (Neu5Gc), because of a mutation that occurred after our last common ancestor with great apes. Although Neu5Gc is presumed absent from normal humans, small amounts have been claimed to exist in human tumors and fetal meconium. We have generated an antibody with high specificity and avidity for Neu5Gc. Fetal tissues, normal adult tissues, and breast carcinomas from humans showed reactivity to this antibody, primarily within secretory epithelia and blood vessels. The presence of small amounts of Neu5Gc was confirmed by MS. Absent any known alternate pathway for its synthesis, we reasoned that these small amounts of Neu5Gc might originate from exogenous sources. Indeed, human cells fed with Neu5Gc incorporated it into endogenous glycoproteins. When normal human volunteers ingested Neu5Gc, a portion was absorbed and eliminated in urine, and small quantities were incorporated into newly synthesized glycoproteins. Neu5Gc has never been reported in plants or microbes to our knowledge. We found that Neu5Gc is rare in poultry and fish, common in milk products, and enriched in red meats. Furthermore, normal humans have variable amounts of circulating IgA, IgM, and IgG antibodies against Neu5Gc, with the highest levels comparable to those of the previously known anti-α-galactose xenoreactive antibodies. This finding represents an instance wherein humans absorb and metabolically incorporate a nonhuman dietary component enriched in foods of mammalian origin, even while generating xenoreactive, and potentially autoreactive, antibodies against the same molecule. Potential implications for human diseases are briefly discussed.

Systemic treatment of AIDS-related kaposi's sarcoma: Results of a randomized trial

PURPOSE Patients with acquired immunodeficiency syndrome (AIDS)-related epidemic Kaposis sarcoma generally respond well to cytotoxic chemotherapy. However, due to the associated myelosuppression, these patients are at risk for developing complicating infections that may affect survival. We therefore conducted a multi-center randomized clinical trial comparing single-agent against combination chemotherapy in advanced AIDS-related Kaposis sarcoma. Low-dose chemotherapy was employed to evaluate its role in combination therapy for this disease and the toxicities associated with the lower intensity. PATIENTS AND METHODS Sixty-one patients with extensive mucocutaneous Kaposis sarcoma or visceral involvement were randomized for treatment with low-dose Adriamycin (doxorubicin, 20 mg/m2) alone (31 cases) or in combination with bleomycin and vincristine (ABV) (30 cases). Patients were randomized within strata based on prognostic features associated with shorter survival in prior studies. Both treatment arms were evenly matched at study entry. RESULTS Complete and partial tumor remissions were significantly higher with ABV (88%) than with Adriamycin alone (48%) (p = 0.004). The median survival was 9 months in both groups. Study entry criteria significantly associated with shorter survival included CD4 lymphocyte counts less than 100/mm3, hemoglobin level less than 10 g/dL, a history of constitutional symptoms, and a prior history of opportunistic infection(s). Toxicities were similar in both arms, and the regimens were well tolerated. Neutropenia (granulocyte count less than 1,000/mm3) occurred in 34% of patients receiving Adriamycin alone and in 52% of patients receiving ABV and was progressive in successive courses of chemotherapy in both treatment arms. The development of AIDS-defined opportunistic infections was relatively infrequent during therapy (14%). CONCLUSIONS Low-dose ABV is an effective chemotherapy regimen for the treatment of extensive Kaposis sarcoma. ABV chemotherapy is associated with significantly higher responses than Adriamycin alone and with acceptable toxicity.

A structural difference between the cell surfaces of humans and the great apes

The sialic acids are major components of the cell surfaces of animals of the deuterostome lineage. Earlier studies suggested that humans may not express N-glycolyl-neuraminic acid (Neu5Gc), a hydroxylated form of the common sialic acid N-acetyl-neuraminic acid (Neu5Ac). We find that while Neu5Gc is essentially undetectable on human plasma proteins and erythrocytes, it is a major component in all the four extant great apes (chimpanzee, bonobo, gorilla and orangutan) as well as in many other mammals. This marked difference is also seen amongst cultured lymphoblastoid cells from humans and great apes, as well as in a variety of other tissues compared between humans and chimpanzees, including the cerebral cortex and the cerebrospinal fluid. Biosynthetically, Neu5Gc arises from the action of a hydroxylase that converts the nucleotide donor CMP-Neu5Ac to CMP-Neu5Gc. This enzymatic activity is present in chimpanzee cells, but not in human cells. However, traces of Neu5Gc occur in some human tissues, and others have reported expression of Neu5Gc in human cancers and fetal tissues. Thus, the enzymatic capacity to express Neu5Gc appears to have been suppressed sometime after the great ape-hominid divergence. As terminal structures on cell surfaces, sialic acids are involved in intercellular cross-talk involving specific vertebrate lectins, as well as in microbe-host recognition involving a wide variety of pathogens. The level of sialic acid hydroxylation (level of Neu5Ac versus Neu5Gc) is known to positively or negatively affect several of these endogenous and exogenous interactions. Thus, there are potential functional consequences of this widespread structural change in humans affecting the surfaces of cells throughout the body.

Developmental regulation of sialic acid modifications in rat and human colon.

Using high‐pressure liquid chromatography (HPLC) and gas‐liquid chromatography/mass spectrometry (GLC/MS), we have confirmed the existence of several sialic acid modifications in the adult rat and human colon. The major O‐acetylated sialic acid in both species is 9‐O‐acetyl‐N‐acetylneuraminic acid; N‐glycolylneuraminic acid is a major component of the adult rat colon. Both of these major modifications were found to be developmentally regulated during the perinatal period in the rat. The N‐glycolyl modification is present prenatally and disappears rapidly in the postnatal period. It reappears in the preweanling period, reaching levels at weaning comparable to those found prenatally. In contrast, the 9‐O‐acetyl modification is very low prenatally, and undergoes a marked increase shortly after birth in both the rat and human colon. The difference in the kinetics of appearance of the two modifications suggests that they are independently regulated. Regulation of these modifications seems to be influenced by exposure to bacterial by‐products or environmental stimuli. The N‐glycolyl modification in the rat colon reappeared at weaning, a time of major change in enteral colonic substances. Spontaneously aborted human fetuses, including three with intrauterine infection at 27, 33, and 35 wk of gestation, showed adult levels of O‐acetylation in colonic tissue. Also, although O‐acetylation in freshly isolated colon tumor specimens was only somewhat lower than that in the adult normal colon, all established colon cancer cell lines studied showed minimal O‐acetylation.— Muchmore, E. A.; Varki, N. M.; Fukuda, M.; Varki, A. Developmental regulation of sialic acid modifications in rat and human colon. FASEB J. 1: 229‐235; 1987.

Chimpanzee models for human disease and immunobiology

Summary: Chimpanzees have greater than 98% genomic sequence homology with humans but have significantly more favorable reponses to human imunodeficiency virus (HIV)‐1 and hepatitis B virus (HBV) and an apparently low incidence of epithelial malignancy. Although there are few shared major histocompatibility complex (MHC) alleles between human and chimp, there is considerable overlap in binding repertoires for epitopes of HIV‐1 and HBV. This indicates that differences in viral handling may be due to involvement of cells other than T lymphocytes. Similar mechanisms may be involved in host response to dysplastic or malignant cells. In seeking to understand these differences, most attention has been focused on comparing and contrasting well‐characterized steps in immune response. As an additional possibility, alterations in cell–cell interactions dependent upon sialic acid binding proteins known to be involved in immune responses should also be considered. The lack of a particular sialic acid structure (N‐glycolyl neuraminic acid, or Neu5Gc) in humans, due to a gene mutation in an essential synthetic enzyme, has potentially altered the kinetics of cellular responses dependent upon these lectins. The absence of Neu6Gc represents the only known major biochemical difference between humans and chimpanzees.

Chemotherapy with 5-fluorouracil (5-FU) and cisplatin or 5-FU, cisplatin, and vinblastine for advanced non-small cell lung cancer. A randomized phase II study of the cancer and leukemia group B.

Two hundred forty‐seven patients with previously untreated nonresectable non‐small cell lung cancer (NSCLC) were entered in a prospective, randomized Phase II trial. Response assessment was possible in 232 patients, and 237 patients were evaluable for survival. Thirteen partial responses (11%) and 5 regressions (4%) of evaluable disease were obtained for the 116 patients treated with 5‐fluorouracil (5‐FU) and cisplatin (C) (95% confidence interval [CI], 8.5% to 21.5%). The median time to progression was 2.2 months and the median survival time was 4.6 months for 5‐FU plus C. Twenty‐three partial responses (20%) and 4 regressions (3%) of evaluable disease were obtained for the 116 patients treated with 5‐FU, C, and vinblastine (V) (95% CI, 15.3% to 30.7%). The median time to progression was 2.8 months and the median survival time was 5.6 months for 5‐FU, C, and V. The 5‐FU and C doses were equivalent in the two treatment regimens. Sixteen of 85 patients (19%) with a performance status of 0 and 18 of 103 patients (17%) with a performance status of 1 responded, whereas only 2 of 44 patients (5%) with a performance status of 2 or greater responded (P = 0.009). Patients who had received locoregional radiation therapy had a lower overall response rate then those in the no prior radiation therapy group (P = 0.028). The median survival time for patients with a performance status of 0 or 1 was 6.3 months compared with 1.9 months for patients with a performance status of 2 or greater (P < 0.001). Performance status also appeared to be a significant factor for time to progression. More frequent and severe leukopenia, fever, genitourinary (GU) toxicity, and pulmonary toxicity was reported with 5‐FU, C, and V. There were three treatment‐related deaths with 5‐FU, C, and V and one treatment‐related death with 5‐FU plus C. Grade III/VI myelotoxicity was not influenced by prior radiation therapy or performance status. Neither regimen is active enough to be considered as standard therapy for advanced NSCLC.

The Chimpanzee Model

Efforts to control the global pandemic of human hepatitis B virus (hHBV) infection have been hampered by incomplete understanding of viral–host interactions in this disease. This situation has been confounded by the fact that hHBV has a limited host range and cannot be propagated in simple cell culture (1). Reproducible experimental infection with determination of infectivity was demonstrated in chimpanzees (Pan troglodytes), but not other primates (2–4), long before other animal models such as the woodchuck were identified. After successful inoculation of chimpanzees was reported in 1972, multiple institutions, including a multigroup collaboration between the FDA, CDC, and NIH, initiated studies to evaluate them as a model for the study of HBV. For the majority of studies only chimpanzees “with no prior exposure” to virus were used because those with positive serology [either from exposure to hHBV or chimpanzee HBV (chHBV)], with an estimated prevalence of 3–6% in Africa (5), were not reproducibly susceptible to infection (3). It has been widely reported that the effects of HBV infection in chimpanzees are milder than in humans, that is, few have developed fulminant hepatitis, and inoculated chimpanzees exhibit few symptoms or signs of infection. Furthermore, the incidence of chronic infection with HBV (see Table 2) and horizontal and vertical transmission (from mother to offspring) in chimpanzees is lower than in humans (6,7). Chimpanzees have been the cornerstone of all research on infectivity of HBV and safety and efficacy of vaccines. Chronic HBV infection occurs in approx 5% of experimentally infected chimpanzees, defined as persistence of hepatitis B surface antigen (HBsAg) for 12 months (approx 2⁄3 clear HBsAg between 6 and 12 months of infection) (8). Liver biopsies of chimpanzees with chronic HBsAg have never been reported to have more severe abnormalities than mild persistent hepatitis (8–11), but we were unable to find published

Primary Care Residents Improve Knowledge, Skills, Attitudes, and Practice After a Clinical Curriculum With a Hospice.

Effective approaches to teaching attitudes, knowledge, and skills to resident physicians in primary care that can be implemented in any residency program are needed. We examined the feasibility and impact of a single palliative care residency curriculum, including a clinical rotation with a hospice program, across 5 cohorts of residents in 7 divergent primary care residency programs (both family medicine and internal medicine). The didactic content was drawn from the national Education for Physicians on End-of-Life Care Project. A total of 448 residents completed the curriculum. A large effect size was seen in measures of knowledge change (*Cohen d = .89) when compared to a national sample of primary care residency programs. Additionally, measures of confidence to perform palliative care skills and ethical concerns also improved significantly (P < .001). A frequent comment is wishing the rest of medicine were like that experienced in the hospice setting. In a separate, ancillary evaluation, the average length of stay of patients enrolled in hospice care was 18.5 days longer for the alumni of this program when compared to physicians referring for hospice care who hadn’t experienced the curriculum.

Prostate adenocarcinoma metastases to the testis and brain: case report and review of the literature

Abstract Prostate cancer is the second most common cancer in men worldwide. While clinicians commonly see metastases to the bones and lymph nodes, it may infrequently spread to more uncommon locations. We report an unusual case of an 83-year-old patient with previously treated prostate adenocarcinoma who presents with symptomatic metastases to the testis and brain in the absence of widely disseminated disease. This case report highlights the importance of including metastatic disease in the differential for patients with a history of prostate cancer and a newly discovered mass until an evaluation of the tissue can be performed.

Delaying the Pediatric Fellowship Start Date to Improve Trainee Well-Being

In this issue of The Journal, the Council of Pediatric Subspecialties (CoPS) is pleased to make its inaugural contribution to AMSPDC Pages. The work of the CoPS Fellowship Start Date Action Team reported here demonstrates the successful networking capabilities that CoPS has developed. CoPS thanks AMSPDC and The Journal for this opportunity. –Rob Spicer for CoPS