The epidemiology of neonatal herpes simplex virus infections in California from 1985 to 1995.

Comprehensive hospital discharge data completed by the California Office of Statewide Health Planning and Development was used to determine whether the proportion of infants

Sequence variation in the src gene product affects metastasis formation: the central, but not exclusive, role of the tumor immune response.

Sequence variation in the src gene product could, in principle, influence metastasis formation through either of 2 effects: an alteration in tumor antigenicity or a non-immune-mediated change in one or more src-associated functions. Our present results establish that both mechanisms underlie the difference in relative levels of metastasis formation induced by the v-src vs. the c-src(527) oncogene. A point that emerges from this analysis is the segregation, within a chicken line genotypically uniform at the major histocompatibility (B) complex (MHC), of a phenotype defined by strong resistance to secondary v-src-induced tumor challenge. The pattern of segregation is consonant with the possibility that a gene unlinked to the MHC governs immune response levels to v-src-encoded tumor antigen.

Endogenous c-src as a determinant of the tumorigenicity of src oncogenes.

We have compared the tumorigenicity of two src oncogenes, v-src and c-src(527), whose respective protein products pp60v-src and pp60c-src(527) show a different spectrum of amino acid substitutions vis-à-vis the c-src protooncogene-encoded product pp60c-src. Whereas the extent of primary tumor growth induced by c-src(527) was quite similar in the two chicken lines tested, the extent of v-src-induced tumor growth showed a marked line dependence. As examined with a line of chickens that shows immune-mediated regression of v-src-induced tumors, a weaker tumor immunity, as correlated with a greater level of primary tumor growth, resulted from inoculation of c-src(527) DNA than of v-src DNA. These observations indicated that the v-src-specific amino acid substitutions define a major tumor antigenicity. That a separate src-associated antigenicity is also targetable by the tumor immune response followed from the finding that the level of protective immunity against the growth of c-src(527) DNA-induced tumors was augmented under conditions of the prior regression of v-src DNA-induced tumors. As this latter antigenicity may include one or more c-src(527)-encoded peptides that are equivalent to c-src-encoded self peptides, these observations suggest that a host tolerance to pp60c-src can be broken so as to permit a tumor immune response based on recognition of self peptides of pp60c-src(527).

Major histocompatibility (B) complex control of the formation of v-src-induced metastases.

Previous observations have shown that the major histocompatibility (B) complex is a determinant of the growth of v-src-induced primary tumors. In the present study, we have observed with two chicken lines congenic for B complex alleles that the control of v-src-mediated oncogenesis by the B complex extends to metastasis formation. In addition, our results show that the differences in metastasis frequencies between these two lines are correlated with the relative strengths of their respective tumor immune responses.

Tumor cells induced by the v-src oncogene are heterogeneous for expression of markers of mesenchyme differentiation.

The observation that v-src-induced tumors contain tumor cells of differing morphology, notably fibroblastoid or polygonal, raised the question as to whether the tumor cells are also heterogeneous with respect to expression of markers of cellular differentiation. Of the markers tested here, consistent reactivity for tumor tissue was noted only for antibody probes reactive to muscle actin (HHF35, alpha sm-1) or to procollagen type I (SP1. D8); for any given tumor, whether induced by v-src DNA or by Rous sarcoma virus, each of these markers was found only in a subpopulation of tumor cells. The observation of marker heterogeneity in the one v-src DNA-induced tumor examined here that typed as monoclonal suggests that v-src-induced transformation is consonant with a degree of plasticity in the phenotypes of the clonal progeny of a single transformant.

Immune-based resistance to the formation of v-src-induced distal tumors.

Although v-src, the oncogene of Rous sarcoma virus, has been shown to be capable of inducing lethal tumors at visceral sites distal to the primary tumor mass, the mechanisms opposing visceral tumor formation remain to be elucidated. In the present study, we show that visceral tumors, many of which represent a metastasis spawned by the primary mass, are found only in hosts exhibiting reduced levels of tumor immunity. We conclude that it is the weakness of the tumor immune response, rather than a lack of expression of tumor antigen on visceral tumor cells, that is a major underpinning of the formation of v-src-induced visceral tumors.

Major histocompatibility (B) complex control of the growth pattern of v-src DNA-induced primary tumors.

Observations that the major histocompatibility (B) complex is a determinant of the growth pattern of Rous sarcoma virus (RSV)-induced tumors raised the question as to whether control is exerted at the level of a v-src-determined, i.e., transformation-specific, function. To investigate this point, the tumor size scores and tumor profile indices of v-src-induced tumors were compared in two lines of chickens congenic for B complex genotypes. The finding that the growth patterns of tumors, induced by v-src DNA inoculation at 6 weeks posthatch, differ in these two lines establishes that the B complex exerts control over tumor growth at the level of a v-src-determined function. The potential importance of this control, in terms of the naturally occurring case of an avian sarcoma virus infection, is suggested by the observation that the patterns of tumor growth in a given congenic line are similar whether the tumors are induced by v-src DNA or by RSV.

Intraventricular conduction disturbances in civilian flying personnel: left anterior hemiblock.

We undertook a retrospective study of the natural history, clinical significance, prognosis, associated conduction disturbances, and pathology, as well as flying fitness qualification of 247 cases of left anterior hemiblock (LAH), detected in a presumably healthy population of 8,915 male individuals engaged in civilian flying activities (prevalence: 2.77%). The cases were divided into three groups according to the electrical axis value of the first electrocardiogram (ECG). The group with the slow mode of appearance of LAH was the most common. If associated with right bundle branch block, LAH usually evolves first. LAH could not be ascribed to any definite pathology; neither was it a forerunner of left bundle branch block nor complete atrioventricular block. Not one episode of syncope nor of sudden incapacitation was reported. As a mere ECG finding, LAH does not modify an aviator's fitness qualification. If another conduction disturbance develops, qualification will depend on the results of complementary studies, non-invasive or invasive, according to any associated conduction disturbance.

Tumor immunity generated in the course of regression of v-src-induced sarcomas.

Previous studies have indicated that the regression versus progression of v-src-DNA-induced sarcomas is dependent on chicken line. As a first step in analyzing the role of tumor immunity as a determinant of this line dependence, experiments were undertaken to ascertain whether an antisarcoma immune response is generated in the course of sarcoma growth in TK chickens, a regressor line. To assay for this response, test TK chickens in which v-src-induced wing web sarcomas had regressed, as well as control TK chickens that had not been exposed to v-src, were challenged in protocols known to yield v-src-dependent sarcoma formation and monitored for challenge sarcoma growth. Compared with the control chickens, the test chickens showed a significant resistance to the sarcomagenic challenge. These results raise the possibility that the antisarcoma response that is inducible in regressor lines, as demonstrated here in terms of a protective effect against a subsequent sarcomagenic challenge, may also underlie the regression of v-src-induced primary sarcomas.

Induction of a diffuse mesothelioma in chickens by intraperitoneal inoculation of v-src DNA.

The presence of peritoneum-based, cytokeratin-positive tumor cells, as detected under conditions of intravenous inoculation of chickens with a v-src-positive DNA fragment, raised the possibility that such DNA may be inductive for diffuse mesothelioma. To investigate this possibility, chickens were inoculated intraperitoneally with v-src DNA, and the resultant peritoneum-based tumor tissue was subjected to histopathological analysis. On the basis of (i) morphology, (ii) immunohistochemistry/histochemistry, and (iii) ultrastructure, we concluded that this tissue represents a diffuse mesothelioma.

Regression of v-src DNA-induced sarcomas is under host genetic control.

Previous results have established that subcutaneous inoculation of chickens (line SC) with a v-src(+) subviral DNA fragment induces the formation of progressor sarcomas at the wing web site of inoculation. Because the sarcoma cells are incompetent for production of exogenous progeny virus, this system is a useful model of tumor expansion by sarcoma cell division, in the absence of infection-mediated recruitment of new tumor cells. The present study was undertaken to define conditions that modulate the pattern of growth (regression vs progression) of v-src DNA-induced sarcomas. These conditions were found to include the line of chicken or the presence on the subviral v-src(+) DNA fragment of a viral replication-specific sequence that includes env.

Wing web or intravenous inoculation of chickens with v-src DNA induces visceral sarcomas.

We have previously found that sarcomas localized to visceral organs frequently arise following wing web inoculation of Rous sarcoma virus. This observation prompted an investigation of whether visceral sarcomas are also inducible by wing web inoculation of a subgenomic viral DNA fragment (v-src DNA) that includes v-src but lacks genes encoding viral structural protein. For this analysis, line SC chickens were inoculated with v-src DNA at 1-2 days posthatch and monitored for 9 weeks. Ninety percent of the chickens developed wing web (primary) tumors at the site of inoculation and, of these, about 30% exhibited visceral tumors. All tumors were histologically identifiable as sarcomas, and both the primary and visceral sarcoma cells were specifically reactive with two monoclonal antibodies elicited to different peptide fragments of pp60v-src. In a separate set of experiments, visceral sarcomas were also observed in about half of the line SC chickens that had been inoculated intravenously with v-src DNA. These results indicate that exogenous progeny virus production is not required for v-src-induced, visceral sarcoma formation. In addition, they demonstrate that intravenous inoculation of v-src DNA is a means to achieve rapid and widespread, disseminated sarcoma growth.

Restricted clonality of visceral sarcomas in avian sarcoma virus-infected chickens.

Experiments were undertaken to analyze proviral DNA in primary (wing web) and visceral sarcomas arising in FP chickens infected with BH-RSV(RAV-2). Using the degree of heterogeneity of BH-RSV proviral integration sites as a measure of the degree of polyclonality of sarcoma tissue, we observed that a high proportion of the visceral sarcomas examined comprised dominant clones, independently of whether these sarcomas were isolated from immune-suppressed or nonsuppressed infected chickens; by contrast, a marked heterogeneity of BH-RSV proviral integration sites was noted with primary sarcoma tissue. Several visceral sarcomas containing dominant clones were characterized by the integration of a deleted form of the BH-RSV provirus. In addition, all of the primary and visceral sarcomas exhibited sequences specific for the RAV-2 provirus, and both types of sarcoma tissue were competent for infectious sarcoma virus production.

Intraventricular conduction disturbances in flying personnel: incomplete right bundle branch block.

We studied the evolving characteristics, as well as the qualification criteria, applied to 261 fliers with incomplete right bundle branch block (IRBBB), detected in a presumable healthy population of 7,685 males engaged in civilian flying activities (prevalence 3.4%). In 136 cases, the IRBBB was detected in the first electrocardiogram. The highest prevalence was observed between 20 and 29 years of age. The IRBBB was permanent in 66 cases and transitory in the remaining 195. The electrical axis shifted to the left in 94 cases. Twelve cases (4.6%) evolved to complete RBBB. The IRBBB pattern implies many different clinical conditions. Flying fitness certification depends upon the cause of the IRBBB. Those due to conduction disturbance with no underlying pathology may qualified. IRBBB associated with other conduction disturbance deserves further study for possible restricted qualification.

The capacity of avian retrovirus-induced sarcomas to expand by infectious virus production.

Sarcomas arising in FP chickens infected with subgroup B avian sarcoma virus at increasing times posthatch were compared for their capacity to mediate recruitment of new sarcoma cells by infectious virus production. This comparison was premised on the observation that primary sarcoma growth is much slower when older chickens are infected with avian sarcoma virus. As measured in a transplantation assay, no age-related diminution in the recruitment capacity of sarcoma tissue from virus-infected transplant donors was observed, despite the marked age-related differences in their patterns of primary sarcoma growth. These observations establish that a diminished recruitment capacity is not required for slow primary sarcoma growth. The capacity to induce the formation of sarcomas at sites distal to the primary sarcoma was correlated with a strong recruitment capacity.

The arginine-stimulated insulin response is impaired in congenital duck hepatitis B virus infection.

Duck hepatitis B virus (DHBV) infects both A (glucagon-containing) and B (insulin-containing) islet cells. To examine the effect of this infection on islet cell function, baseline and secretagogue-augmented plasma insulin and glucagon levels as well as the pancreatic content of insulin and glucagon were compared in congenitally DHBV- and noninfected ducks. No difference in baseline plasma levels or the pancreatic content of insulin or glucagon was detected. However, the magnitude of the second phase of the biphasic arginine-stimulated insulin response was markedly diminished in infected ducks.

The immune status of avian sarcoma virus-infected chickens as a determinant of sarcoma growth pattern and viral antigen expression.

Patterns of sarcoma growth were compared in immune-suppressed (cyclophosphamide-treated) vs nonsuppressed avian sarcoma virus-infected chickens. Sarcomas were initially induced in suppressed or nonsuppressed line FP chickens (donors) by wing web inoculation with clone 85, an avian sarcoma virus encoding an envelope glycoprotein that is non-antigenically cross-reactive with endogenous viral glycoprotein. Sarcoma tissue from these donors was then implanted in the wing webs of suppressed or nonsuppressed recipients to compare the effects of immune suppression of donors and of recipients. Sarcoma tissue that had been excised from suppressed donors and implanted in the wing webs of nonsuppressed recipients evidenced a much greater capacity than sarcoma tissue from nonsuppressed donors to yield distal sarcomas localized to visceral organs and to induce expansion by infection-mediated recruitment of new sarcoma cells. In contrast, immune suppression of the recipients of sarcoma tissue from nonsuppressed donors was not significantly enhancing for these effects. The enhancement achieved by immune suppression of the donors correlated with a markedly increased level of virus production and viral antigen expression by the primary (wing web) sarcoma cells from these donors.

Humoral immune responsiveness in duck hepatitis B virus-infected ducks.

Immunofluorescence assays with fixed tissue sections were used to characterize antibody reactivity in sera obtained from duck hepatitis B virus-infected ducks. Under conditions of experimental infection, antibody to core antigen but not to surface antigen was detectable. A majority of the ducks infected at 8 days after hatching and a minority of those infected at 1 day after hatching showed a transient anti-core antigen humoral response; this response was stronger in the antibody-positive ducks infected on day 8 than in those infected on day 1. Antiviral antibody was not detected in the sera of ducks congenitally infected with duck hepatitis B virus. Several of the infected ducks, but none of the uninfected ducks, exhibited autoantibody reactivity for alpha-islet-cell-associated antigen.

Embryonic infection with the endogenous avian leukosis virus Rous-associated virus-0 alters responses to exogenous avian leukosis virus infection.

We inoculated susceptible chicken embryos with the endogenous avian leukosis virus Rous-associated virus-0 (RAV-0) on day 6 of incubation. At 1 week after hatching, RAV-0-infected and control chickens were inoculated with either RAV-1 or RAV-2, exogenous viruses belonging to subgroups A and B, respectively. The chickens injected with RAV-0 as embryos remained viremic with exogenous virus longer and either failed to develop type-specific humoral immunity to exogenous virus or developed it later than the control chickens not inoculated with RAV-0. The RAV-0-injected chickens also developed neoplasms at a much higher frequency than did the control chickens. We suggest that the lower immune responses of the RAV-0-injected chickens were due to an immunological tolerance to envelope group-specific glycoproteins shared among endogenous and exogenous viruses.

Expression of endogenous retroviral envelope glycoprotein as a determinant of immunity to Rous sarcoma.

To analyze the effect of the expression of endogenous retroviral envelope glycoprotein on tumor immunity, patterns of sarcoma growth were compared in inbred FP line chickens infected with either of two strains of avian sarcoma virus, Pr-B (subgroup B) or cl.85 (subgroup G). These viruses were chosen for analysis because the envelope glycoprotein of Pr-B, but not of cl.85, is antigenically cross-reactive with the endogenous retroviral envelope glycoprotein expressed in the FP line. Inoculation of 1-day-old hatchmates with either virus yielded a significant percentage of chickens with distal sarcomas localized to visceral organs. By contrast, a marked difference in the percentage of chickens bearing distal sarcomas was noted when sarcoma tissue excised from virus-inoculated donors was implanted in 1-day-old recipients; a high proportion of the recipients of Pr-B-induced sarcoma tissue (Pr-B-sarcoma recipients), but only a low proportion of the cl.85-sarcoma recipients, exhibited distal sarcomas. At 3 weeks posthatch, a significantly higher percentage of donor-derived cells was detected in the primary tumors of the cl.85- versus the Pr-B-sarcoma recipients. A model of immune control, premised on the tolerogenicity of endogenous viral glycoprotein, is proposed to rationalize these results.