Background: Significant differences in human papillomavirus (HPV) prevalence between pregnant and nonpregnant women have been reported. Some studies suggest that physiological processes during pregnancy modify the host–immune response, increasing detectability of high-risk HPV infection as a result of viral reactivation. It remains uncertain, however, whether pregnancy has an effect on HPV DNA positivity as a result of a general lack of data and based on contradictory results found in previous epidemiologic studies. We conducted an epidemiologic study to identify differences in the prevalence of HPV infection between pregnant and nonpregnant women in Mexico. We also investigated the relationship of HPV DNA positivity with socioeconomic, gynecologic, and obstetric risk factors. Methodology: We screened pregnant and age-matched nonpregnant women for high-risk HPV infection. The study population was clients of the family medicine healthcare services of the Mexican Institute of Social Security in Cuernavaca, Morelos, Mexico. A total of 274 pregnant and 1060 nonpregnant study participants were screened for the presence of high-risk HPV DNA in self-collected specimens by the Hybrid Capture 2 test (HC2; Digene Corp., Gaithersburg, MD). Results: High-risk HPV DNA was detected in 37.2% (95% confidence interval [CI], 31–43%) of pregnant women and in 14.2% (95% CI, 12–16%) of nonpregnant women. Combining both groups for the multivariate analysis, pregnancy was associated with an increased risk for HPV infection (odds ratio, 3.5; CI, 2.7–4.9). Conclusions: Our results are consistent with other studies reporting increased high-risk HPV detection rates among pregnant women. HPV-positive status in pregnant and nonpregnant women appears to be influenced by age. The decrease in HPV positivity by number of pregnancies in both currently pregnant and nonpregnant women is consistent with a possible effect of immune protection as a result of earlier HPV infections. Despite lack of information about a woman’s history of sexual behavior, these data support the hypothesis that an alteration of immunologic responses during pregnancy may be associated with an increased risk of HPV acquisition or reactivation.

Infection by Helicobacter pylori affects about 50% of the human population. Of those infected, 10% to 15% will develop peptic ulcer and up to 3% will present with gastric cancer. These estimates suggest that around 7% of the world's population will eventually develop H. pylori –associated

Objective. The purpose of this paper is to describe some of the results of the Morelos HPV Study. The main objective of the Morelos HPV Study is to evaluate the use of human papillomavirus (HPV) DNA testing, as compared to the Papanicolaou (Pap) test, for cervical cancer (CC) screening. Material and Methods. The Morelos HPV Study is currently being conducted in Mexico, to examine the possibility of using HPV testing for CC screening. The HPV testing of self-collected vaginal and clinician-collected cervical specimens was evaluated as part of this study. The acceptability of the HPV testing of self-collected specimens was compared to that of the Pap test. A cost-effectiveness analysis (CEA) and cost-benefit analysis (CBA) was also performed. Results. The Morelos HPV Study results indicate that HPV testing has a greater sensitivity to detect cervical intraepithelial neoplasia (CIN) 2/3 and CC than the Pap test, Our results also indicate an over-all lower acceptability of the Pap test as compared to the self-collected procedure. The results of the CEA and CBA indicate that screening women between the ages of 20-80 for CC using some type of HPV testing is always more cost-effective than screening for CC using the Pap test. Conclusions. Our results suggest that self- and clinician-collected HPV testing could be used in CC prevention programs, as an effective complement or substitute for the Pap test.

Objective. The purpose of this paper is to describe the design and methodology of the Morelos HPV Study. The main objective of this study is to examine the use of two different methods for obtaining HPV DNA specimens, self-collected vaginal and clinician-collected cervical, to detect pre-invasive cervical lesions and cancer. Material and Methods. This study was conducted within the regular population-based framework of the Mexican Institute of Social Security (IMSS) cervical cancer screening program in Morelos. A total of 7,868 women were recruited between May and October 1999 and are representative of the population of women attending cervical cancer screening services at the 23 IMSS clinics in the state of Morelos in 1999. Women were provided with a detailed description of the study before signing an informed consent form. Basic data were obtained from all participants using a standard IMSS registration form. During the initial recruitment visit, a randomly selected subsample of 1069 participants were interviewed to collect additional information about cervical cancer risk factors, acceptability of the HPV and Pap tests, as well as patient costs. Before the pelvic exam, participants were asked to provide a self-collected vaginal specimen for HPV testing. All participants underwent a pelvic examination that involved collecting a cervical sample for the Pap smear and a clinician-collected HPV specimen. Data were evaluated from 7732 women with complete information for the three tests. The 1147 women who received at least one positive result (Pap, self- and/or clinician-HPV tests) were invited to return for a colposcopic examination. During colposcopy, biopsies were taken as appropriate, to histologically confirm a diagnosis of cervical intraepithelial neoplasia (CIN) 2/3 or invasive cancer. A total of 1,015 women attended colposcopy, and 101 women received a histologically-confirmed CIN 2/3 or cervical cancer diagnosis. Conclusions. The initial enrollment activities of the Morelos HPV study are the basis for a prevalent case-control study and a prospective cohort study that will investigate the natural history of HPV infections and determine if an HPV-based screening strategy is a safe and cost-effective alternative to Pap screening. The English version of this paper is available too at: http://www.insp.mx/salud/index.html.

The human leukocyte antigen DRB1 locus (HLA-DRB1) was typed in genomic DNA extracted from whole blood samples of 34 Mexican dengue hemorrhagic fever (DHF) patients and 47 dengue fever (DF) patients, by polymerase chain reaction-sequence-specific oligonucleotide reverse dot blot. HLA-DRB1*04 was negatively associated with risk of DHF (OR 0.31, 95% CI 0.11-0.85). HLA-DR4 homozygous individuals were 11.6 times less likely to develop DHF in comparison to DR4 negative persons (OR 0.08, 95% CI 0.01-0.75). After adjusting for gender and infection type by logistic regression, DR4 positive individuals were 3.6 times less likely to develop DHF than DR4 negative persons (OR 0.28, 95% CI 0.12-0.66). A secondary dengue virus infection was also positively linked with DHF risk (OR 2.89, 95% CI 0.92-9.07). This data suggests that genes of the major histocompatibility complex play a major role in the susceptibility and/or resistance to develop DHF. In Mexicans, HLA-DR4 may be a genetic factor that is protective against DHF. Because HLA-DR4 has been positively selected in Latin American populations, these results may apply also to other similar ethnic groups, particularly those with high percentages of admixture with indigenous Amerindian genes.

BACKGROUND:Human papillomavirus 16 (HPV16) has a number of variants, each with a different geographic distribution and some that are associated more often with invasive neoplasias. We investigated whether the high incidence of cervical cancer in Mexico (50 cases per 100 000 women) may be associated with a high prevalence of oncogenic HPV16 variants.METHODS:Cervical samples were collected from 181 case patients with cervical cancer and from 181 age-matched control subjects, all from Mexico City. HPV16 was detected with an E6/E7 gene-specific polymerase chain reaction, and variant HPV classes and subclasses were identified by sequencing regions of the E6 and L1/MY genes. Clinical data and data on tumor characteristics were also collected. All statistical tests were two-sided.RESULTS:HPV16 was detected in cervical scrapes from 50.8% (92 of 181) of case patients and from 11% (20 of 181) of control subjects. All HPV16-positive samples, except one, contained European (E) or Asian-American (AA) variants. AA and E variants were found statistically significantly more often in case patients (AA = 23.2% [42 of 181]; E = 27.1% [49 of 181]) than in control subjects (AA = 1.1% [two of 181]; E = 10% [18 of 181]) (P<.001 for case versus control subjects for either E or AA variants, chi2 test). However, the frequency of AA variants was 21 times higher in cancer patients than in control subjects, whereas that ratio for E variants was only 2.7 (P =.006, chi2 test). The odds ratio (OR) for cervical cancer associated with AA variants (OR = 27.0; 95% confidence interval [CI] = 6.4 to 113.7) was higher than that associated with E variants (OR = 3.4; 95% CI = 1.9 to 6.0). AA-positive case patients (46.2 +/- 12.5 years [mean +/- standard deviation]) were 7.7 years younger than E-positive case patients (53.9 +/- 12.2 years) (P =.004, Student's t test). AA variants were associated with squamous cell carcinomas and adenocarcinomas, but E variants were associated with only squamous cell carcinomas (P =.014, Fisher's exact test).CONCLUSIONS:The high frequency of HPV16 AA variants, which appear to be more oncogenic than E variants, might contribute to the high incidence of cervical cancer in Mexico.

The authors analyzed the relation between lactation history, organochlorine serum levels-in particular, 2,2-bis(p-chlorophenyl)-1,1,1-trichloroethane (DDT) and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE)-and the risk of breast cancer within a subsampe from a larger breast cancer case-control study conducted among women living in Mexico City, Mexico, between 1990 and 1995. From the original study, they selected a random sample of 260 subjects (1:1 case/control ratio). Analysis was restricted to 120 cases and 126 controls who had given birth to at least one child and had complete information on all key variables. Serum DDE levels were higher among cases (mean = 3.84 microg/g lipids, standard deviation = 5.98) than among controls (mean = 2.51 microg/g lipids, standard deviation = 1.97). After adjustment for age, age at menarche, duration of lactation, Quetelet index, and serum DDT levels, serum DDE levels were positively related to the risk of breast cancer (adjusted odds ratio (OR)Q1-Q2 = 1.24, 95% confidence interval (CI): 0.50, 3.06; ORQ1-Q3 = 2.31, 95% CI: 0.92, 5.86; ORQ1-Q4 = 3.81, 95% CI: 1.14, 12.80; test of trend, p = 0.02). The increased risk associated with higher serum DDE levels was more apparent among postmenopausal women (ORQ1-Q4 = 5.26, 95% CI: 0.80, 34.30; test of trend p = 0.03). A longer period of lactation was associated with a slightly decreased risk of breast cancer independently of serum DDE levels (OR = 0.91, 95% CI: 0.85, 0.99 change in risk per 10 months of lactation). Serum DDT level was not related to the risk of breast cancer. The data suggest that high levels of exposure to DDE may increase women's risk of breast cancer, particularly among postmenopausal women.