Mother-to-child transmission of human T-lymphotropic virus type II

Viruses and Human Milk: Transmission or Protection?

Human milk (HM) is considered the best source of nutrition for infant growth and health. This nourishment is unique and changes constantly during lactation to adapt to the physiological needs of the developing infant. It is also recognized as a potential route of transmission of some viral pathogens although the presence of a virus in HM rarely leads to a disease in an infant. This intriguing paradox can be explained by considering the intrinsic antiviral properties of HM. In this comprehensive and schematically presented review, we have described what viruses have been detected in HM so far and what their potential transmission risk through breastfeeding is. We have provided a description of all the antiviral compounds of HM, along with an analysis of their demonstrated and hypothesized mechanisms of action. Finally, we have also analyzed the impact of HM pasteurization and storage methods on the detection and transmission of viruses, and on the antiviral compounds of HM. We have highlighted that there is currently a deep knowledge on the potential transmission of viral pathogens through breastfeeding and on the antiviral properties of HM. The current evidence suggests that, in most cases, it is unnecessarily to deprive an infant of this high-quality nourishment and that the continuation of breastfeeding is in the best interest of the infant and the mother.

Breast milk and infection

Three viruses (CMV, HIV, and HTLV-I) frequently cause infection or disease as a result of breast-milk transmission. Reasonable guidelines have been pro-posed for when and how to avoid breast milk in the case of maternal infection. For other viruses, prophylactic immune therapy to protect the infant against all modes of transmission are indicated (VZV, varicella-zoster immunoglobulin, HAV and immunoglobulin, HBV, and HBIg + HBV vaccine). In most maternal viral infections, breast milk is not an important mode of transmission, and continuation of breastfeeding is in the best interest of the infant and mother (see Tables 2 and 3). Maternal bacterial infections rarely are complicated by transmission of infection to their infants through breast milk. In a few situations, temporary cessation of breastfeeding or the avoidance of breast milk is appropriate for a limited time (24 hours for N gonorrheae, H infiuenzae, Group B streptococci, and staphylococci and longer for others including B burgdorferi, T pallidum, and M tuberculosis). In certain situations, prophylactic or empiric therapy may be advised for the infant (eg, T pallidum, M tuberculosis, H influenzae) (see Table 1). Antimicrobial use by the mother should not be a reason not to breastfeed. Alternative regimens that are compatible with breastfeeding can be chosen to treat the mother effectively. In most cases of suspected infection in the breastfeeding mother, the delay in seeking medical care and making the diagnosis means the infant has been ex-posed already. Stopping breastfeeding at this time only deprives the infant of the nutritional and potential immunologic benefits. Breastfeeding or the use of expressed breast milk, even if temporarily suspended, should be encouraged and supported. Decisions about breast milk and infection should balance the potential risk compared with the innumerable benefits of breast milk.

Seroepidemiology of HTLV-I/II in Argentina: an overview

In this report, the results of seroepidemiologic studies of human T-lymphotropic virus type I (HTLV-I) and type II (HTLV-II) infections in different population groups in Argentina have been compiled. The studies have shown a high prevalence of HTLV-I/II infection in blood donors in the provinces in the north of Argentina (1.0% in Jujuy, 0.7% in Salta, and 0.6% in Formosa) and a low prevalence in the provinces in the central region of the country (<or=0.1%). High rates of HTLV-I (0.45%-2.78%) and HTLV-II (2.78%-21.9%) infections have been documented in Native Indian groups and have highlighted the importance of sexual and mother-to-child transmission of the viruses. The presence of HTLV-I/II antibodies in HIV-infected individuals indicates that both viruses are circulating in certain high-risk population groups. HTLV-I/II was detected in intravenous drug users (2.56%-21.7%), homosexual men (0.5-1.33%), prostitutes (0.8%), and hemophiliacs (2.8%). In conclusion, HTLV-I/II infection is circulating in low- and high-risk populations in Argentina, and these findings would support the view that selective screening for HTLV-I/II should be implemented to reduce the spread of infection.

Soroprevalência de vírus linfotrópico de células T humanas, vírus da imunodeficiência humana, sífilis e toxoplasmose em gestantes de Botucatu - São Paulo - Brasil: fatores de risco para vírus linfotrópico de células T humanas

Com o objetivo de estudar a soroprevalência de vírus linfotrópico de células T humanas I/II (HTLV-I/II), vírus da imunodeficiência humana, sífilis e toxoplasmose, em gestantes atendidas em unidade básicas de saúde do município de Botucatu - São Paulo - Brasil, bem como os fatores de risco para a infecção pelo HTLV -I/II, foram realizados inquérito sorológico e avaliação dos resultados de exames solicitados na rotina do prénatal. Em 913 gestantes, a soroprevalência de HTLV- I e de HTLV- II foi de 0,1%. Sífilis, toxoplasmose e infecção pelo HIV foram encontradas. Nenhum dos fatores de risco pesquisados mostrou-se seguro para identificar gestantes com infecção pelo HTLV- I/II. A comparação da proporção de gestantes infectadas e de doadores de sangue da região sudeste do Brasil com testes reagentes para HTLV- I/II não mostrou diferença estatística.

Prevalence of human T-cell leukemia virus types I and II in Switzerland

The retroviruses human immunodeficiency virus (HIV)-1/2 and human T-cell leukemia virus (HTLV)-I/II share modes of transmission, suggesting that efforts to monitor the current HIV-1 epidemic in Switzerland should be complemented by assessment of HTLV-I/II prevalence. This study presents an updated evaluation of HTLV-I/II infection among groups within the Swiss population polarized towards either low or increased risk of infection. Archived serum and peripheral blood mononuclear cell (PBMC) samples were examined for evidence of HTLV-I/II infection by enzyme-linked immunosorbant assay (ELISA), type-specific Western blot, type-specific polymerase chain reaction (PCR), DNA sequence analysis, and virus culture. Among blood donations obtained from low-risk Swiss donors, we report a complete lack of HTLV-II infection and the occurrence of HTLV-I infection limited to a prevalence of 0.079 per 100,000 (1/1,266,466). Among high-risk HIV-positive persons and HIV-negative persons at increased risk of HIV-infection, we report a focus of HTLV-I and HTLV-II infection at prevalence rates of 62 per 100,000 (1/1,620) and 309 per 100,000 (5/1,620), respectively. The finding of low HTLV-I/II prevalence among Swiss blood donors and containment of HTLV-I/II infection within known risk-groups does not support initiation of HTLV-I/II screening for Swiss blood, tissue, and organ donations.

Breast milk transmission of viral disease

Breast milk transmission of maternal viral infection is well established for CMV and HIV-1. In the case of CMV, this usually does not pose a risk to the infant since serious disease is prevented by placentally transferred maternal antibody. However, in HIV infection, breast-feeding increases the risk of maternal-fetal transmission by about 25% with late breast-feeding (after six months of age) constituting a particular risk. In other maternal viral diseases, e.g., other herpes viruses, parvovirus, hepatitis A, B and C, and rubella, the virus is often demonstrated in the breast milk, but transmission is very rare. The highest risk is during an acute viral infection at the time of birth, since the breast milk has a high titer of virus, and a lack of antibody to neutralize the organism.

Efficacy of 3'-azido 3'deoxythymidine (AZT) in preventing HTLV-1 transmission to human cord blood mononuclear cells

The present study investigated the effect of 3'-azido 3'deoxythymidine (AZT) treatment on in vitro infection of human cord blood mononuclear cells (CBMCs) exposed to HTLV-1 by cocultivation with the MT-2 cell line. Cultures of CBMCs were grown in IL-2 and were either left untreated or were treated with concentrations of AZT ranging from 0.0078 to 32 microM. HTLV-1-infected cultures were monitored at different times of culture by evaluating proliferation activity, cell growth and the presence and expression of HTLV-1 genes. Results showed that untreated cultures infected with HTLV-1 were able to grow for several weeks, while those treated with AZT at 0.03 microM or higher concentrations were limited in their growth capacity. Moreover, the addition of AZT at the moment of infection significantly inhibited cell proliferation in a dose-dependent fashion. In the presence of AZT, detection of proviral DNA and, more remarkably, viral RNA expression were clearly reduced. In addition, treatment with AZT resulted in a noticeable decrease in Tax protein expression. Using treatment with relatively low doses of AZT, effective in exerting an antiviral action, cytotoxicity on CBMCs was not observed, whereas higher doses induced apoptosis in uninfected CBMCs. These data show that CBMCs are protected by AZT against HTLV-1 transmission even at low, non-toxic doses.

Different population dynamics of human T cell lymphotropic virus type II in intravenous drug users compared with endemically infected tribes

The phylogeny of human T cell lymphotropic virus type II (HTLV-II) was investigated by using strains isolated from Amerindian and Pygmy tribes, in which the virus is maintained primarily through mother-to-child transmission via breast-feeding, and strains from intravenous drug users (IDUs), in which spread is mainly blood-borne via needle sharing. Molecular clock analysis showed that HTLV-II has two different evolutionary rates with the molecular clock for the virus in IDUs ticking 150-350 times faster than the one in endemically infected tribes: 2.7 x 10(-4) compared with 1.71/7.31 x 10(-7) nucleotide substitutions per site per year in the long terminal repeat region. This dramatic acceleration of the evolutionary rate seems to be related with the mode of transmission. Mathematical models showed the correlation of these two molecular clocks with an endemic spread of HTLV-II in infected tribes compared with the epidemic spread in IDUs. We also noted a sharp increase in the population size of the virus among IDUs during the last decades probably caused by the worldwide increase in intravenous drug use.

Vertical transmission of HTLV-I/II: a review

The vertical transmission of the human T-cell lymphotropic virus type I (HTLV-I) occurs predominantly through breast-feeding. Since some bottle-fed children born to carrier mothers still remain seropositive with a frequency that varies from 3.3% to 12.8%, an alternative pathway of vertical transmission must be considered. The prevalence rate of vertical transmission observed in Japan varied from 15% to 25% in different surveys. In Brazil there is no evaluation of this form of transmission until now. However, it is known that in Salvador, Bahia, 0.7% to 0.88% of pregnant women of low socio-economic class are HTLV-I carriers. Furthermore the occurrence of many cases of adult T-cell leukemia/lymphoma and of four cases of infective dermatitis in Salvador, diseases directly linked to the vertical transmission of HTLV-I, indicates the importance of this route of infection among us. Through prenatal screening for HTLV-I and the refraining from breast-feeding a reduction of approximately 80% of vertical transmission has been observed in Japan. We suggest that in Brazil serologic screening for HTLV-I infection must be done for selected groups in the prenatal care: pregnant women from endemic areas, Japanese immigrants or Japanese descendents, intravenous drug users (IDU) or women whose partners are IDU, Human immunodeficiency virus carriers, pregnant women with promiscuous sexual behavior and pregnant women that have received blood transfusions in areas where blood donors screening is not performed. There are in the literature few reports demonstrating the vertical transmission of HTLV-II.

Highly endemic human T-lymphotropic virus type II (HTLV-II) infection in a Venezuelan Guahibo Amerindian group

Sera from 166 Guahibo Indians (55% of the population) living in southwest Venezuela were screened by enzyme-linked immunoassay for antibodies to human T-cell lymphotropic virus (HTLV) I and II. Positive samples were confirmed by immunofluorescence and Western blot. Forty-one Guahibos (24.8%) were found to be seropositive. Polymerase chain reaction (PCR) analysis of proviral DNA in mononuclear cell lysates revealed the virus to be HTLV-II. Prevalence increased with age, and sexual contact with HTLV-II-seropositive partners was identified as a risk factor for infection. PCR amplification of a region of the pol gene, utilizing the primer pair SK110/SK111, with subsequent digestion of the 140-base-pair amplification products with HinfI and MseI restriction enzymes, showed an HTLV-II subtype-b restriction pattern in all cases. These data suggest that the substrain infecting this Guahibo community belongs to the b subtype, the most frequent among Paleo-Amerindian populations.