Latina contraceptive decision-making and use: The importance of provider communication and shared decision-making for patient-centered care

BACKGROUND

Poor patient-provider communication, among other reasons, is a notable barrier to contraceptive decision-making among Latinas. Patient-centered approaches to contraceptive counseling that optimize communication align with shared decision-making (SDM) -which is associated with satisfaction and continued contraceptive use among various populations.

OBJECTIVE

To examine associations of patient-provider communication and importance of SDM tenets with consistent contraceptive use among a population of Latinas.

PATIENT INVOLVEMENT

Formative work for this study included prior qualitative and quantitative research with Latinas who expressed the importance of patient-provider communication during contraceptive counseling and therefore were instrumental in problem definition.

METHODS

Cross-sectional surveys were administered to Latinas ages 15-29 years. Patient-provider communication, patient-reported importance of specific SDM tenets, and consistent contraception use were measured and analyzed for associations.

RESULTS

103 Latinas (mean age = 21.4) participated. 33% of participants<21 years were using contraception consistently vs. 67% for those ≥ 21 (p = 0.003). Among participants ≥ 21, consistent users reported higher communication scores compared to inconsistent users and non-users (p = 0.042). For participants< 21, consistent users were more likely than inconsistent users and non-users to report that 2 SDM tenets (discussion of contraceptive preferences and avoidance of race/ethnic-based judgement) are important (p = 0.052, 0.028, respectively).

DISCUSSION

Patient-provider communication was especially important for Latinas ≥ 21 while using an SDM approach during counseling was highly valued by those<21. Patient-centered approaches to contraceptive counseling provide opportunities to optimize healthcare delivery for this vulnerable population.

PRACTICAL VALUE

Results from this research demonstrate that patient-centered communication is highly valued by Latina study participants and is an important consideration in their contraceptive counseling. Clinicians should consider employing techniques such as SDM as they seek to provide patient-centered care during contraceptive counseling for this patient population.

Contraceptive Decision Making Among Latina Immigrants: Developing Theory-Based Survey Items

BACKGROUND

Contraception is important for reproductive autonomy, yet many Latinas do not use contraception consistently despite research reporting a desire to do so. Factors varying in priority and value come into play during contraceptive decision making. When measuring these, relevant survey items may vary by populations.

AIM

This study focused on developing an ethnically responsive, patient-centered, content-valid survey for measuring factors that influence contraceptive decision making among immigrant Latinas.

METHOD

Nonpregnant self-identified Latinas ages 15 to 24 years in Baltimore, MD, were recruited from a family planning facility. Using the theory of planned behavior as a theoretical framework and prior formative research, initial survey items were drafted (Step 1). Content validation and cognitive interviewing procedures (Step 2 and Step 3) were used to develop final items.

RESULTS

Final items (27) were content-validated by the target population; items reflect important factors and relevant contexts affecting contraceptive decision making among Latinas in Baltimore.

DISCUSSION

These theory-based items provide an important contribution to the literature because they measure and explore factors related to contraceptive decision making in an understudied population. Providers might consider these factors during counseling to build patient-centered communication. These items might serve to measure responses to theory of planned behavior-based interventions designed to improve the contraceptive counseling of Latinas.

Is depression associated with contraceptive motivations, intentions, and use among a sample of low-income Latinas?

BACKGROUND

Latinas in the United States experience high rates of unintended pregnancy and low rates of contraception use, yet reasons are not completely understood. Depression is common among pregnant and nonpregnant Latinas; its influence on contraceptive motivations, intentions, and use is understudied.

OBJECTIVES

We sought to 1) describe Latinas' contraceptive motivations, intentions, and use; 2) use structural equation modeling to test associations between depression and contraceptive self-efficacy/motivations/intentions/use; and 3) determine whether associations differ by pregnancy status.

METHODS

This cross-sectional study included Latinas ages 15 to 45 recruited from an urban Federally Qualified Health Center in Baltimore, Maryland. Structured surveys were used to collect data regarding depressive symptoms measured using the PHQ-9. All other constructs were measured with previously validated questions. Constructs included contraceptive self-efficacy, positive and negative contraceptive motivations (perceived advantages and disadvantages of using contraception), contraceptive intentions to begin or continue contraception use, and contraceptive methods currently used.

RESULTS

Among pregnant Latinas, depression was associated with negative motivations (β = 0.16; p < .05), negative motivations were associated with intentions (β = -0.22; p < .01), and contraceptive self-efficacy was associated with intentions (β = 0.43; p < .001). Among nonpregnant Latinas, contraceptive self-efficacy was associated with intentions (β = 0.78; p < .001) and intentions were associated with use (β = 0.40; p < .05).

CONCLUSIONS

Among pregnant Latinas, negative motivations intervene in the association between depression and contraceptive intentions. For nonpregnant Latinas, intentions intervene in the association between self-efficacy and contraceptive use. This study underscores the importance of depression screening during pregnancy and encourages practitioners to target contraceptive motivations to improve contraceptive use.

Engaging hard-to-reach patients in patient-centered outcomes research

Aims: This study aimed to identify methods to engage hard-to-reach patients in the research process. Materials & methods: With funding from the Patient-Centered Outcomes Research Institute (Washington, DC, USA), the University of Maryland (MD, USA) conducted 20 focus groups and one individual interview. The sample consisted of six groups of hard-to-reach patients, two groups of healthcare providers who work with hard-to-reach patients and two groups of surrogates of hard-to-reach patients. Results & conclusion: In order to make patient-centered outcomes research more meaningful to patients and their caregivers, patient-centered outcomes research should be conducted with a focus on building and maintaining trust, which is achieved via pre-engagement with communities and continuous engagement of study participants and their communities.

Social determinants of breast cancer screening in urban primary care practices: a community-engaged formative study

BACKGROUND

The recent decline in the breast cancer mortality rate can be attributed to intensive screening and early detection efforts. However, studies have documented a decline in self-reported recent mammography use and interventions to enhance mammography utilization have yielded modest improvements. To address the root causes of breast cancer disparities and improve mammography use, interventions need to address multiple layers of patient, provider, and health system factors.

OBJECTIVE

Using community-based participatory research principles, we sought to learn from women receiving care through urban primary care practices about issues surrounding mammography screening and strategies to increase screening.

METHODS

We conducted five focus groups among 41 eligible women who were predominantly African American, recruited using nonprobability purposive sampling methods from urban community health centers in Baltimore, Maryland. Data are reported from three focus groups (n = 28) that provided usable data. We used the social determinants of health perspective to conduct a qualitative content analysis and interpretation of the data.

RESULTS

Major obstacles to obtaining a screening mammogram were individual-level (i.e., pain from the procedure) and structural-level factors (i.e., cost, geography, convenience). Strategies to overcome obstacles could include the creation of structural mechanisms whereby women can receive a host of services during one visit to a healthcare professional's office. Important promoters of screening behavior included social-level factors such as social support, hope, and positive treatment outcomes.

CONCLUSION

The social determinants of health perspective provided a unique perspective to frame barriers and promoters of mammography utilization and insights to develop interventions aimed at improving cancer control among women receiving care at urban primary care health centers.

Adherence to medication regimens among low-income patients with multiple comorbid chronic conditions

This qualitative study sought to explore facilitators and barriers to adherence to multiple medications among low-income patients with comorbid chronic physical and mental health conditions. The 50 focus group participants identified personal/contextual and health system factors as major impediments to adherence to multiple medications. These factors included medication side effects, fear of harm from medication, fear of dependence on medication, complex instructions, suboptimal communications with doctor, suspicion about doctors' and pharmaceutical companies' motives in prescribing medication, and the high cost ofmedications. Participants also identified motivators, both internal (self-initiated) and external (initiated by family, doctor, support groups),to ensure adherence to multiple medications. These motivators included self-discipline, sense of personal responsibility, faith, support from family members and doctors, and focused health education and self-management support. Three themes emerged that enhanced understanding of the complexity of adherence to multiple medications: (1) reaching one's own threshold for medication adherence, (2) lack of shared information and decision making, and (3) taking less than the prescribed medication. Further analysis of the data revealed that the patients perceived a lack of shared decision making in the management of their comorbid chronic conditions and their medication regimen.

Motivational intervention to reduce rapid subsequent births to adolescent mothers: a community-based randomized trial

PURPOSE

One-quarter of adolescent mothers bear another child within 2 years, compounding their risk of poorer medical, educational, economic, and parenting outcomes. Most efforts to prevent rapid subsequent birth to teenagers have been unsuccessful but have seldom addressed motivational processes.

METHODS

We conducted a randomized trial to determine the effectiveness of a computer-assisted motivational intervention (CAMI) in preventing rapid subsequent birth to adolescent mothers. Pregnant teenagers (N = 235), aged 18 years and older who were at more than 24 weeks' gestation, were recruited from urban prenatal clinics serving low-income, predominantly African American communities. After completing baseline assessments, they were randomly assigned to 3 groups: (1) those in CAMI plus enhanced home visit (n = 80) received a multi-component home-based intervention (CAMI+); (2) those in CAMI-only (n = 87) received a single component home-based intervention; (3) and those in usual-care control (n = 68) received standard usual care. Teens in both intervention groups received CAMI sessions at quarterly intervals until 2 years' postpartum. Those in the CAMI+ group also received monthly home visits with parenting education and support. CAMI algorithms, based on the transtheoretical model, assessed sexual relationships and contraception-use intentions and behaviors, and readiness to engage in pregnancy prevention. Trained interventionists used CAMI risk summaries to guide motivational interviewing. Repeat birth by 24 months' postpartum was measured with birth certificates.

RESULTS

Intent-to-treat analysis indicated that the CAMI+ group compared with the usual-care control group exhibited a trend toward lower birth rates (13.8% vs 25.0%; P = .08), whereas the CAMI-only group did not (17.2% vs 25.0%; P = .32). Controlling for baseline group differences, the hazard ratio (HR) for repeat birth was significantly lower for the CAMI+ group than it was with the usual-care group (HR = 0.45; 95% CI, 0.21-0.98). We developed complier average causal effects models to produce unbiased estimates of intervention effects accounting for variable participation. Completing 2 or more CAMI sessions significantly reduced the risk of repeat birth in both groups: CAMI+ (HR = 0.40; 95% CI, 0.16-0.98) and CAMI-only (HR = 0.19; 95% CI, 0.05-0.69).

CONCLUSIONS

Receipt of 2 or more CAMI sessions, either alone or within a multicomponent home-based intervention, reduced the risk of rapid subsequent birth to adolescent mothers.

Bypass of local primary care in rural counties: effect of patient and community characteristics

PURPOSE

This national study sought information from rural patients (1) to assess the prevalence of bypass, a pattern of seeking health care outside the local community; (2) to examine the impact of locally available primary care physicians (PCPs) and hospital size on the odds of bypass; and (3) to identify patient demographic and geographic factors associated with bypass. This study also ascertained the reasons patients give for bypass and their suggestions for how hospitals can retain patients locally.

METHODS

We analyzed data from a 2005 telephone survey of 1,264 adults, aged 18 years or older, who lived within 20 miles of 25 randomly selected Critical Access Hospitals and were linked with a Health Professional Shortage Area and 2004 census data. Respondents were asked about demographic characteristics, travel time and distance to local hospitals, and insurance status, as well as for suggestions of what local hospitals could do to retain patients.

RESULTS

Overall, 32% of respondents bypassed local primary care; the rate ranged from 9% to 66% across the Critical Access Hospital service areas. Factors associated with bypass included age, education, marital status, satisfaction with the local hospital, admission to a hospital in the past 12 months, hospital size, and local density of PCPs. Compared with residents in areas with a higher density of PCPs (=3,500 residents per PCP), residents in areas with a low density (>4,500 residents per PCP) were more likely to bypass local care (odds ratio, 1.58; 95% confidence interval, 1.02-2.46). Lack of specialty care and limited services were most frequently mentioned as reasons why patients bypassed local hospitals.

CONCLUSIONS

The sizable variation in bypass rates among this sample of Critical Access Hospital service areas suggests that strategies to reduce bypass behavior should be directed at the local community or facility level. Changing rural residents' perception of their local care, helping them gain a better understanding of the function of primary care, and increasing the number of PCPs might help hospitals retain patients and rural communities stay healthy.

Home visiting for adolescent mothers: effects on parenting, maternal life course, and primary care linkage

PURPOSE

Adolescent mothers are at risk for rapidly becoming pregnant again and for depression, school dropout, and poor parenting. We evaluated the impact of a community-based home-visiting program on these outcomes and on linking the adolescents with primary care.

METHODS

Pregnant adolescents aged 12 to 18 years, predominantly with low incomes and of African American race, were recruited from urban prenatal care sites and randomly assigned to home visiting or usual care. Trained home visitors, recruited from local communities, were paired with each adolescent and provided services through the child's second birthday. They delivered a parenting curriculum, encouraged contraceptive use, connected the teen with primary care, and promoted school continuation. Research assistants collected data via structured interviews at baseline and at 1 and 2 years of follow-up using validated instruments to measure parenting (Adult-Adolescent Parenting Inventory) and depression (Center for Epidemiologic Studies Depression). School status and repeat pregnancy were self-reported. We measured program impact over time with intention-to-treat analyses using generalized estimating equations (GEE).

RESULTS

Of 122 eligible pregnant adolescents, 84 consented, completed baseline assessments, and were randomized to a home-visited group (n = 44) or a control group (n = 40). Eighty-three percent completed year 1 or year 2 follow-up assessments, or both. With GEE, controlling for baseline differences, follow-up parenting scores for home-visited teens were 5.5 points higher than those for control teens (95% confidence interval, 0.5-10.4 points; P = .03) and their adjusted odds of school continuation were 3.5 times greater (95% confidence interval, 1.1-11.8; P <.05). The program did not have any impact on repeat pregnancy, depression, or linkage with primary care.

CONCLUSIONS

This community-based home-visiting program improved adolescent mothers' parenting attitudes and school continuation, but it did not reduce their odds of repeat pregnancy or depression or achieve coordination with primary care. Coordinated care may require explicit mechanisms to promote communication between the community program and primary care.

Reduced School Dropout Rates Among Adolescent Mothers Receiving School-Based Prenatal Care

BACKGROUND

Adolescent pregnancy is associated with increased school dropout rates. Dropping out amplifies the probability of persistent social and economic disadvantage. Whether school-based health centers might help reduce school absenteeism and dropout rates in this group has not been well studied.

OBJECTIVE

To examine the association of school-based prenatal services on school attendance and dropout rates.

METHODS

In this retrospective cohort study, using school rosters from an alternative school, we identified adolescents aged 18 years or younger who delivered a baby between July 1, 1995, and August 30, 1997, in Baltimore, Md. We linked school records spanning 3 years with medical records and birth certificates. School variables such as attendance and dropout rates were examined in relation to the teen's year of pregnancy and prenatal care setting (school-based vs non-school-based). Hierarchical logistic regression was used to examine effects of school-based prenatal care on dropout and promotion or graduation rates, with adjustment for baseline group differences.

RESULTS

We identified 431 predominantly African American, low-income adolescents who attended the alternative school in their pregnancy school year. In the year prior to pregnancy, most performed poorly in school and had significant absenteeism. During their pregnancy school year, teens receiving school-based prenatal care were absent 12 fewer days, as compared with those receiving non-school-based care (P =.001), and their dropout rate was half that of those receiving non-school-based care (6% vs 15%; P =.02). Hierarchical logistic regression analyses, with adjustment for baseline prepregnancy differences, demonstrated that teens receiving school-based prenatal care were less likely to drop out of school during the pregnancy year (adjusted odds ratio, 0.39; 95% confidence interval, 0.15-0.99; P =.048).

CONCLUSIONS

Absenteeism and dropout rates were reduced for pregnant adolescents receiving prenatal care at a school-based health center in an urban alternative school. Findings underscore the importance of funding and evaluating school-based health centers and other interventions that may ameliorate negative outcomes among childbearing adolescents.

Reduced low birth weight for teenagers receiving prenatal care at a school-based health center: effect of access and comprehensive care

PURPOSE

To examine and compare access to care, comprehensiveness of care, and birth outcomes for teenagers receiving prenatal care in comprehensive adolescent pregnancy programs (CAPPS) in two different settings: school-based vs. hospital-based.

METHODS

Retrospective sohort study using existing data sources: medical records and birth certificates. Using school rosters and hospital clinic databases, we identified pregnant adolescents < or =18 years old who delivered a baby between July 1, 1995 and August 30, 1997 and who received prenatal care in a school-based CAPP (SB-CAPP) or hospital-based CAPP (HB-CAPP). Process of care measures (prenatal care adequacy and comprehensive care) and outcomes (low birth weight) were examined by site of care. Logistic regression models were computed to predict the odds of low birth weight by site of prenatal care, adjusting for prenatal care adequacy, comprehensive care, and possible confounders including baseline maternal characteristics.

RESULTS

Three-hundred-ninety eligible teens were identified. Mean age was 15.9 years, 93% were African-American, 84% in school, 13% had a prior birth, and 11% were cigarette smokers. Teens receiving care in the SB-CAPP were significantly younger and more likely to be in school than those in the HB-CAPP. Overall, the two groups had similar low rates of prenatal care adequacy, but compared with teens in the SB-CAPP, those in the HB-CAPP were 1.5 times less likely to receive comprehensive care. Logistic regression analyses adjusting for baseline maternal differences showed that HB-CAPP teens were more than three times as likely to deliver a low birth weight infant compared with SB-CAPP teens (AOR 3.75; 95% CI 1.05-13.36). The increased odds of low birth weight for HB-CAPP teens attenuated when prenatal care was adequate and comprehensive (AOR-HB-CAPP: 2.31, 95% CI 0.65-8.24).

CONCLUSIONS

School-based prenatal care was associated with significantly lower odds of low birth weight compared with HB-CAPP care. Although selection bias may be a factor in this observational study, our findings suggest that these improved birth outcomes may be mediated through prenatal care adequacy and provision of comprehensive care.

The effect of volunteer home visitation for adolescent mothers on parenting and mental health outcomes: a randomized trial

BACKGROUND

Children of adolescent mothers may suffer because of parenting inadequacies. The use of volunteer home visitors to enhance parenting skills has not been well studied.

OBJECTIVE

To evaluate the effect of a volunteer model home visitation program on adolescent parenting outcomes.

DESIGN

Randomized trial with assignment to home visitation or control group.

SETTING

Urban, African American community.

PARTICIPANTS

Adolescents aged 12 to 18 years at 28 or more weeks' gestation or who had delivered a baby in the past 6 months were recruited between February 1996 and August 1999.

INTERVENTION

Volunteers were recruited from the community and trained to implement a parenting curriculum during weekly home visits. Each volunteer was paired with one teenager.

MAIN OUTCOME MEASURE

Validated instruments measuring parenting stress, parenting behaviors, and mental health.

RESULTS

A total of 232 teenagers were successfully randomized to home visitation and control groups. At baseline, the groups were comparable on demographic, social support, and mental health measures. Almost half the teenagers had poor mental health at baseline, and high rates persisted at follow-up in both groups. In multivariate models, the home visitation group demonstrated significantly better parenting behavior scores at follow-up than did the control group (P =.01) but showed no differences in parenting stress or mental health.

CONCLUSIONS

The volunteer home visitation program significantly improved some parenting outcomes but not parental distress or poor mental health. Volunteers may be an effective means of providing parenting education, but interventions that include specific means of addressing poor mental health are likely to have greater effects.

The diagnostic challenge of infective endocarditis: cutaneous vasculitis leading to the diagnosis of infective endocarditis

BACKGROUND

Signs and symptoms of infectious endocarditis are protean. They result from destruction of cardiac endothelium, metastatic embolization, hematogenous seeding, and immune complex deposition. Embolic manifestations of infectious endocarditis can mimic several other pathologic conditions and make the diagnosis of infectious endocarditis difficult.

METHODS

We describe a case of cutaneous vasculitis leading to the diagnosis of infectious endocarditis. A review of the literature highlights the variable clinical presentations and key diagnostic strategies in the evaluation of infectious endocarditis.

RESULTS AND CONCLUSION

Infective endocarditis has protean clinical symptoms and signs and can be a challenging diagnosis. Being alert to the condition is crucial, and where a high clinical probability exists despite a negative transthoracic echocardiogram, diagnostic evaluation with transesophageal echocardiograph is required.

Depressive symptoms, stress, and social support in pregnant and postpartum adolescents

OBJECTIVE

To assess prospectively the incidence and course of depressive symptoms among pregnant and postpartum adolescents and explore the roles of stress and social support as influencing factors.

METHODS

Pregnant teenagers attending a comprehensive adolescent pregnancy and parenting program were enrolled during their third trimester of pregnancy and followed up through 4 months post partum. Depressive symptoms and social support were measured with validated, self-administered instruments during the third trimester and at 2 and 4 months post partum. Stress was measured during the prenatal and postpartum periods.

RESULTS

Study participants (N=125) were predominantly black (93%), and wee aged 12 to 18 years. Completed assessments were obtained from 114 subjects at 2 months post partum and 108 at 4 months. Forty-two percent had significant depressive symptoms in the third trimester, with 36% and 32% having scores that indicated depression at 2 and 4 months post partum. Stress levels increased significantly from the third trimester to the postpartum period (P < .01) and were positively associated with depressive symptoms. Receiving social support from the adolescent's mother or the infant's father, especially in the postpartum period, was significantly associated with lower rates of depression. Reporting conflict with the infant's father was strongly associated with increased rates of depressive symptoms.

CONCLUSIONS

Results indicate that depressive symptoms are common among pregnant teenagers and postpartum adolescents. Stress and social support appear to be important mediators. Identifying those teenagers with high stress and conflict and low levels of support will help identify those who are at particular risk for depressive symptoms.

Association between postpartum substance use and depressive symptoms, stress, and social support in adolescent mothers

OBJECTIVE

Substance use by pregnant teenagers is an important public health problem, but published data on alcohol and illicit drug use by parenting teenagers are virtually nonexistent. This study determined the prevalence of alcohol and drug use in adolescent mothers in the first 4 months postpartum and explored associated psychosocial characteristics.

METHODS

Teenagers attending a comprehensive adolescent pregnancy and parenting program were enrolled consecutively during a routine third trimester prenatal visit. Alcohol use since delivery was determined by self-report at 4 months postpartum using an instrument developed for the 1984 Survey of Drug Abuse Among Maryland Adolescents. Illicit drug use was measured with anonymous quantitative urine drug screens at 2 and 4 months postpartum. Depressive symptoms, stress, and social support were assessed at 2 and 4 months postpartum using validated, self-administered instruments. Differences in demographic characteristics, peer group influences, and psychosocial variables between substance users and nonusers were evaluated.

RESULTS

Participants (125/129 eligible) were predominantly African-American, mean age 16.3 years. Completed assessments were obtained from 110 at 2 months and 105 at 4 months postpartum. Forty-two percent screened positive for illicit drugs at a postpartum visit or reported using alcohol since delivering their baby and were classified as substance users. Thirty-one percent of subjects reported alcohol use since delivery. Marijuana was the most prevalent illicit drug (14%), followed by opiates (5%), and cocaine (4%). When substance users were compared with nonusers, 44% versus 24% scored depressed (P = .02), 62% versus 43% had high stress (P = .04), and 62% versus 44% reported a high need for social support (P = .07). Results of logistic regression, after controlling for age, indicated that illicit substance and/or alcohol use was 3.3 times greater for those who were depressed, 2.8 times greater if they reported friends' using illicit drugs, and 6.7 times greater if the adolescent reported smoking cigarettes since delivery.

CONCLUSIONS

This study indicates that alcohol and drug use are common among this sample of postpartum teenage mothers and that depression, stress, high support need, and peer group drug use are associated factors. Although this study cannot determine whether depression and stress precede or result from use of substances, attention to these factors appears warranted in the care of adolescent mothers.

Hepatic vein thrombosis in a teenager: a case report

Hepatic vein thrombosis or the Budd-Chiari syndrome is an uncommon condition which rarely occurs in teenagers. The condition involves obstruction of blood flow from the liver with progressive congestion and hepatic failure. The etiology is often idiopathic but may involve conditions that increase thrombogenic tendencies. Oral contraceptives are known to increase the risk of a number of thrombotic conditions and have been associated with the Budd-Chiari syndrome. Although millions of teenagers have used oral contraceptives without incident, occasionally we are reminded of their potential serious complications. The case of a 19-year-old who developed hepatic vein thrombosis while using oral contraceptives is presented.

Discrete regions of simian virus 40 large T antigen are required for nonspecific and viral origin-specific DNA binding

The nondefective adenovirus type 2 (Ad2)-simian virus 40 (SV40) hybrid viruses, Ad2+ND2 and Ad2+ND4, have been used to determine which regions of the SV40 genome coding for the large tumor (T) antigen are involved in specific and nonspecific DNA binding. Ad2+ND2 encodes 45,000 M4 (45K) and 56,000 Mr (56K) T antigen-related polypeptides. The 45K polypeptide did not bind to DNA, but the 56K polypeptide bound nonspecifically to calf thymus DNA, Ad2+ND4 encodes 50,000 Mr (60K), 66,000 Mr (66K), 70,000 Mr (70K), 74,000 Mr (74K), and 90,000 Mr (90K) T antigen-related polypeptides, all of which bound nonspecifically to calf thymus DNA. However, in more stringent assays, where tight binding to viral origin sequences was tested, only the 90K protein specified by Ad2A+ND4 showed specific high affinity for sequences at the viral origin of replication. From these results and previously published experiments describing the SV40 DNA integrated into these hybrid viruses, it was concluded that SV40 early gene sequences located between 0.39 and 0.44 SV40 map units contribute to nonspecific DNA binding, whereas sequences located between 0.50 and 0.63 SV40 map units are necessary for specific binding to the viral origin of replication.

A small subclass of SV40 T antigen binds to the viral origin of replication

We examined the affinities of SV40 large T antigen for unique viral DNA sequences by binding SV40 Bst NI DNA fragments in extracts of infected or transformed cells, and then immunoprecipitating the T antigen-DNA complex. The G fragment, which spans the viral origin of replication (ori) was quantitatively bound to T antigen. A T-antigen-specific monoclonal antibody (McI 7), which recognized only 5%-10% of the T antigen from infected or transformed cells, immunoprecipitated the majority of the ori-binding activity. This suggests that only a minor subclass of wild-type T antigen is active in binding to the origin. C6 cells contain a replication-defective mutant T antigen that when tested in the DNA-binding immunoassay, showed no affinity for the ori fragment. McI 7 not only failed to immunoprecipitate ori binding in C6 cells, but also did not detect any labeled C6 T antigen whatever. Thus McI 7 recognizes an immunologically distinct subset of wild-type 7 antigen that comprises the origin-binding form of the viral protein, which is absent in the C6 T antigen population. McI 122, which recognizes a 53 kilodalton host protein that complexes with T antigen, immunoprecipitated ori-binding activity from extracts of infected or transformed cells, but not from C6 cells. Thus wild-type T antigen can bind ori sequences even when complexed to the host protein. These data suggest that T antigen consists of different subpopulations with different functions.

Different forms of simian virus 40 large tumor antigen varying in their affinities for DNA

In various permissive monkey cell lines infected with simian virus 40 there are two major forms of large T antigen which differ in their rate of sedimentation through sucrose gradients. The lighter (5 to 7S) form sedimented slightly more rapidly than the 4S tRNA marker, whereas the heavier (16S) form sedimented slightly more slowly than the 18S rRNA marker. The small t antigen did not form complexes which sedimented as rapidly as those formed by the large T antigen. The 16S T antigen form was converted to the slowly sedimenting 5 to 7S form in the presence of 1.0 M NaCl. The majority of large T antigen synthesized in cell-free protein-synthesizing systems primed by mRNA isolated from infected cells sedimented as the 5 to 7S form even when premixed with excess quantities of cellular T antigen. The formation of the 16S form in infected cells did not require ongoing viral or cellular DNA replication because considerable quantities of this T antigen class were produced in the presence of DNA synthesis inhibitors, such as cytosine arabinoside. Both 5 to 7S and 16S forms could be isolated separately and, therefore, each could be analyzed as to its individual properties. The 5 to 7S T antigen form bound more efficiently and tightly to DNA and had specific affinity for sequences at the viral origin of replication, whereas the 16S form bound less efficiently to DNA and exhibited very little specificity for origin-containing DNA sequences. It is therefore likely that the active DNA-binding species of T antigen isolated from infected cells is the 5 to 7S form.