The Global Fool

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Sex Differences in the Immune Response to Vaccines
Feb11

Sex Differences in the Immune Response to Vaccines

By Roberta Attanasio Women and men respond differently to infectious microbes and vaccines – it is said, indeed, that the immune system of women is stronger than the immune system of men. Stronger or weaker, one thing is certain – men and women are not the same in terms of immune response. A few years ago, the journal Lancet Infectious Diseases published “ The Xs and Y of immune responses to viral vaccines” – a comprehensive article that clearly shows how the biological differences between sexes influence the immune response to vaccines, as for example the influenza, yellow fever and hepatitis vaccines. There are not many published studies on the same subject, though. The majority of scientists involved in vaccine research do not consider sex as a variable and, typically, vaccine trials are not designed to take into account the physiological differences that exist between men and women. If we had to take these differences into account, how would things change when vaccinating human populations? In the New York Times article “Do women need such big flu shots?” Op-Ed contributors Sabra Klein and Phyllis Greenberger provide an example related to one of the influenza vaccines: “Under the current guidelines, men and women are to get equal-sized doses of the H1N1 vaccine. Yet women’s bodies generate a stronger antibody response than men’s do, research shows, so less vaccine may be needed to immunize them. If we could give women a smaller dose, there would be more vaccine to go around. And we might also spare them the mild side effects that vaccines can cause, like pain at the injection site, inflammation and fever. All of these are more common in women than in men.” In 2010, the World Health Organization published “Sex, Gender and Influenza”, a report that “focuses on the different effects of seasonal epidemics, pandemics and localized outbreaks of influenza on males and females including pregnant women.” The report concludes that “significantly more research is required to gain a more complete understanding of the complex and varied effects of sex and gender on influenza infection and vaccination, and underscores the need to consider their interplay with any infectious disease of global concern.” However, there are still large gaps in our understanding of how sex differences influence the immune response to vaccines and not enough research is done to fill these gaps. May be, step by step, we’ll get there. Meanwhile, here is one of the steps – a new study found that high levels of testosterone make the immune response to the flu vaccine go south. The study – “Systems analysis of sex differences reveals an immunosuppressive role for...

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H7N9 Influenza Virus: Ethnicity and Protection from Infection
Jan29

H7N9 Influenza Virus: Ethnicity and Protection from Infection

By Roberta Attanasio In March 2013, a new flu virus — the H7N9 — was identified in China. By early May, before retreating and disappearing, it had infected 131 people and killed 26 of them.  However, less than two weeks ago (January 17), the New York Times reported that “China is disclosing a steadily growing number of cases of H7N9 bird flu, including four more cases announced on Friday, reviving concerns among health experts that the disease may be spreading and could pose a further threat as the world’s largest annual human migration begins ahead of Chinese New Year.” The H7N9 virus is a “reassortant” — it includes combined elements from three distinct viruses. People acquire the virus mostly from exposure to infected poultry. As of today (January 29, 2013), the World Health Organization states that there is no evidence of sustained person-to-person spread of H7N9. No cases of H7N9 infection have been reported outside of China. According to the Centers for Disease Control and Prevention (CDC), “It’s likely that sporadic cases of H7N9 associated with poultry exposure will continue to occur in China. Cases associated with poultry exposure also may be detected in neighboring countries. It’s also possible that H7N9 may be detected in the United States at some point, possibly in a traveler returning from an affected area. Most concerning about this situation is the pandemic potential of this virus.” During pandemics, which are caused by the worldwide spread of infectious microbes, different human populations respond differently to the infection, most likely because of specific differences in factors related to their immune system. Is this also true for the H7N9 virus? Should we expect differences in the susceptibility of different populations to infection? An international team of investigators from institutions in Australia, Singapore, the U.S. and the U.K. report, in an article recently published by the journal Proceedings of the National Academy of Sciences USA (January 21, 2014), that different human populations may indeed vary in their susceptibility to H7N9 infection. The article is titled “Preexisting CD8+ T-cell immunity to the novel H7N9 influenza A virus varies across ethnicities” and presents results related to several ethnic groups, including Caucasoid, North American natives, Oriental, African, Amerindian, Alaskan Yupik and Australian Aboriginals. Because H7N9 is a “new” virus, the immune system does not have memory of it and it is not ready to quickly produce neutralizing antibodies — which protect from infection or severe disease — when it encounters the virus. In absence of neutralizing antibodies, the human immune system relies mostly on a type of killer cells — called cytotoxic T lymphocytes — for protection against the virus.  These lymphocytes kill cells infected with the virus...

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The Great Global Die-Off: Frogs and Lymphocytes
Oct28

The Great Global Die-Off: Frogs and Lymphocytes

By Roberta Attanasio Frogs and other amphibians – salamanders and caecilians – have been declining worldwide during the past few decades at an alarming rate. According to a June 2012 assessment by the International Union for the Conservation of Nature and Natural Resources (IUCN), about 41 percent of amphibian species are at risk of extinction, and some are already extinct. Like many other inhabitants of our planet, amphibians have been hit hard by climate change and habitat loss – and not only. Amphibians have also been decimated by the spread of chytridiomycosis, which is defined by the IUCN as the single most devastating infectious disease of vertebrate animals. In a historical article published in 2008, David Wake and Vance Vredenburg state: “A general message from amphibians is that we may have little time to stave off a potential mass extinction.”   The deadly chytridiomycosis is caused by Batrachochytrium dendrobatidis (Bd), a fungus found on all continents except Antarctica. According to epidemiological evidence described in an article published in 2004, the Bd fungus was present in African clawed frogs (Xenopus laevis) in their native South Africa as early as the mid-1930s. African clawed frogs infected with Bd do not show any clinical sign of disease and can carry the fungus for long periods of time without dying. Therefore, these frogs are Bd carriers and transmit the fungus to vulnerable species. Worldwide dissemination of Bd started in the 1930s because of the international trade of African clawed frogs. From the 1930s to 1950s, large numbers of these frogs were caught in the wild in southern Africa and exported across the world, mostly for use in the first human pregnancy tests and scientific research. Results from a study recently published in the journal PLOSone confirm that Bd was present as a stable, endemic infection in Xenopus populations in Africa prior to their worldwide distribution, which likely occurred via international live-amphibian trade. Vance Vredenburg, lead author of the study, said: “Today, these frog populations are often found in or near urban areas, probably because hospitals released them into the wild when new pregnancy testing methods were invented in the 1960s.” Bd proliferates in skin cells and rapidly kills amphibians by disrupting skin function – it impairs the skin’s ability to absorb electrolytes. A few years ago, a group of scientists from Australia found that, in diseased frogs, the skin’s ability to take up sodium and potassium ions from the water decreases by more than 50 percent, leading to a sharp decline of these ions in the blood and eventually causing cardiac arrest and death. Despite these recent discoveries, there was an unanswered question: “Why is the amphibian immune system so inept at clearing the fungus?” Now, a team of investigators from Vanderbilt University reports, in an article published in the journal Science and entitled...

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