#protozoan Toxoplasma

[falseandrealultravival]

Let's moderate our love of cleanliness! (The psychology of parents peeked through the sandbox)

"Clean sandbox: A sandbox environment where children can play safely!

Our sandbox is

@Dry heat treatment

@Ozone water spraying

@Hot water treatment etc.

Managed annually."

This is the catchphrase of the sandbox at the nursery school near my house, and the sign is posted so many people, myself included, can see it.

By the way, does a sandbox need that much management? When you think of a sandbox, what immediately comes to mind is cat poop. Almost all cats carry the protozoan Toxoplasma, and sand mixed with their feces is dangerous for women who have given birth for the first time, as it can lead to miscarriage.

　

　I think this is going too far.

However, even though a cat-proof fence is sufficient to eliminate the toxoplasmosis problem, asking the zoo to take further measures is rather dangerous. In addition, when I looked closely at the scene, I found that cats were allowed to enter as much as they wanted. The cat was able to get in through the gap in the gate, and there was only a plastic net hanging over the sandbox, so the cat had a free pass.

Those who eliminate ``bacteria in general'' do so by keeping the power of bacteria away, and when they encounter bacteria they have never encountered before, they will be defeated. In the past, cholera was endemic around India, and the local people got used to it and did not show any symptoms. When you come to an area unrelated to you, the disease symptoms will appear in that area. Well, cholera is a hazardous disease, so the above story may be quite unreasonable. However, it is just an endemic disease locally.

Therefore, if you are exposed to various dangers (including bacteria) daily, you will be more likely to survive when a full-scale disaster occurs. ...That's right, I define disaster as "something that threatens human existence."

I wonder what the mothers of the children at this nursery school think about what I've said so far.

清潔好きもたいがいにせえ！（砂場から覗ける保護者の心理）

　きれいな砂場：子供たちが安心して遊べる砂場環境！

当園の砂場は

@乾熱処理

@オゾン水散布

@熱水処理　　など

年間管理しています。

これは、私の家の近くにある保育園の砂場のキャッチフレーズで、その看板が大きく張り出されているので、私も含め多くの人の目にふれます。

　ところで、たかが砂場に、それほどの管理が必要なのでしょうか。砂場と言って、すぐ思いだされるのは、猫の糞です。猫は大体ほとんど全ての個体が「トキソプラズマ」という原虫を保有していて、その糞が混じった砂は、そう、初産の女性にとって、流産の可能性ももつ危険なものです。

　

　これはやりすぎではないでしょうかねえ。

　でも、トキソプラズマ問題をクリアーするのには、猫除けフェンスで十分なのに、それ以上の対策を園に依頼するのは、むしろ危険な行為です。なお、現場をよく見てみると、猫が入り放題になっていました。門扉のすき間から猫が入り込め、プラスティックの網が砂場にたらしてあるだけだったので、猫はフリーパスでした。

「菌・一般」を排除する者は、それが、菌の力を遠ざけることにより、出合ったことの無い菌に出合うとイチコロにやられます。過去においても、コレラはインド周辺の風土病であり、現地人はそれに慣れて症状はでませんが、日本人が現地になんの準備もなく行ったり、ベクター（病原菌の運び屋）が病気と関係のない地域に来ると、イチコロでその地域に病気の症状が出たりするのです。まあ、コレラは危険度の高い病気ですから、以上のお話にはかなり無理があるかもしれません。ただ、現地ではただの風土病ですから。

　だから、日ごろから、色々な危険（細菌も含む）と隣り合っているほうが、本格的な災害が来たとき、耐えうる率も高いでしょう。・・・そうそう、私は災害という言葉を、「人の存在を脅かすもの」と定義しています。

　この保育園の児童の母親たちは、ここまで述べてきた内容についてどう思うでしょうね。

[mudwerks]

(via Behavior-changing parasite moves wolves to the head of the pack | Ars Technica)

Toxoplasma gondii is a ubiquitous protozoan parasite that can infect any warm-blooded species. In lab studies, infection with T. gondii has been shown to increase dopamine and testosterone levels along with risk-taking behaviors in hosts including rodents, chimps, and hyenas. Oh, and humans.

[everlastiingiimmortals]

and what if lithogenesis was a disease caused by a symbiotic relationship between a stone-skinned organism and some sort of pathogen, but due to the lack of evolutionary history with other species it is instead incredibly prolific and deadly..

[great-and-small]

What’s your favorite turtle and also favorite parasite?

How could I ever choose?! I can’t pick absolute favorites but I can definitely choose some top contenders

Turtles:

- Alligator snapping turtle (I deeply love any type of snapper but these guys are just totally something else- once you work with one you’re hooked forever)

- Gopher tortoise (keystone species with talk show host level charisma)

- Bog Turtles (the cutest animal on earth??)

- Radiated tortoise (I love all the Madagascar tortoise species but these take my breath away)

- Eastern box turtle (if these dudes don’t fill you with childlike wonder I don’t get you)

- Diamondback terrapin (makes me feel how I assume old white guys feel when they see a fancy muscle car. Just a great looking kickass turtle here)

Parasites:

- Screwworms (parasitic larvae of a fly but terrifying and fascinating- these worms are the reason we have sterile insect technique)

- Toxoplasma gondii (best parasite to go down the rabbit hole researching; this protozoan is running the world)

- Parasitic wasps are morbidly fascinating to me so I’ll also say Jewel wasp (can perform brain surgery on the exact part of a cockroach’s brain that would allow it to escape)

- Any type of pentastomid (mysterious and cool, will never forget finding a dead snake filled to the brim with them)

- Guinea worm (interesting worm with cool history and life cycle- former US president Jimmy Carter once vowed to eradicate this parasite in his lifetime)

[trashwaaveactual]

Fellas, time to start cat-maxxing

[bogleech]

Hey Bog, you know a lot about worms. Could you tell me if toxoplasma gondii is a worm? I don't think it is, but some jerk on the internet believes they are.

Sounds like someone who thinks "parasite" automatically means "worm," which isn't even a meaningful scientific category anyway since "worms" means nothing other than "this boneless animal is long." Toxoplasma is a single-celled protozoan and that's pretty well established.

[semi-official-bird]

A common medical parasite with a symbiotic relationship with humanoids is P. vengativa util. P. util is a predatory, hyperparasitoid protozoa distantly related to Toxoplasma Gondii that inhabits the digestive system of species commonly living in low-population areas.

This protozoan is widely used as parasitic prevention due to the production of a chemical similar to clindamycin during the organism’s reproductive stage. Although not harmful to humanoids, P. util reproduces within other intestinal parasites, either rendering them infertile or killing them, while the chemical it produces prevents further infection. Most organisms with P. util rarely, if ever, have parasetic infactions, most of which are mild and go away quickly.

Commonly regarded as normal bacterial flora, most humanoids will ingest oocysts of the protozoa at a young age or gain them in fetal development to prevent parasitic infections related to or as a cause of ingesting contaminated water, raw meat or other infected substances. 

In addition to sterilizing multicellular parasites, P. util also consumes bacteria typically associated with gastroenteritis in direct response to the body’s immune response. It also consumes some types of stomach flora in herbivorous humanoids, lack of which can be prevented though ingestion of probiotics and fermented foods.

It is typical for oocysts to be ingested at a young age to prevent instability of stomach flora during adulthood (after the body’s immune system has fully developed), which can cause complications such as stomach upset, acid reflux and temporary development of allergies while the digestive ecosystem regains balance. These conditions may be permanent in some cases.

[pokmajom]

Ebből a vasárnapból, azt azért nem néztem volna ki, hogy arról fogok olvasni, a toxoplazmozissal fertőzött férfiak kedvelik a macskapisi szagát, a nők viszont nem.

[askpokeeosin]

Boop you’re a cat!

Cat feces is not the only way that Toxoplasma gondii, the protozoan parasite that causes the disease Toxoplasmosis, is spread. It is the vector that everyone remembers, though.

Also, shout out to long dead memes from when I was in high school.

[ankhmeanswombman]

Gender differences in behavioural changes induced by latent toxoplasmosis - PubMed

[jkottke]

Maybe Toxoplasma gondii, a protozoan parasite which humans can get from cats, makes humans want to share cat videos with each other.

[ribosome-papers]

Cap-independent translation directs stress-induced differentiation of the protozoan parasite Toxoplasma gondii

bioRxiv: http://dlvr.it/TDQ6hf

[cidiliabra]

"Certain parasites in nature exert the kind of control that makes a host act contrary to its own interests. One protozoan, Toxoplasma gondii, reproduces inside the belly of a cat, and is then excreted by the feline. One way it begins the cycle again is to infect a rat passing near the excrement. Toxoplasma gondii reprograms the infected rat to love cat urine, which to healthy rats is a predator warning. An infected rat wallows in cat urine, offering itself up as an easy meal to a nearby cat. This way, the parasite again enters the cat's stomach, reproduces, and is expelled in the cat's excrement—and the cycle continues."

- Dream Land — The True Tale of America's Opiate Epidemic, by Sam Quinones

[chrinopiqua]

The Great Cat Mask Mandate: A Bold Plan to Eradicate Toxoplasma gondii from Wild Felid Populations

Abstract: In a groundbreaking approach to wildlife conservation, we propose a novel strategy to eliminate the parasitic menace Toxoplasma gondii from wild felid populations. Drawing inspiration from recent public health initiatives, our solution leverages the power of masks, social distancing, and a few well-placed hand sanitizer stations to protect our feline friends from this cunning parasite. While the idea may seem unconventional, we argue that the effectiveness of these measures in human populations suggests they could work wonders in the animal kingdom as well.

Introduction

Toxoplasma gondii is a protozoan parasite with a notorious reputation for infecting warm-blooded animals, including humans and wild felids. While the parasite’s life cycle typically revolves around cats, it's high time we turn the tables on T. gondii. Drawing on recent global experiences with infectious disease control, we propose a comprehensive plan to eliminate this parasite from wild felid populations using time-tested public health measures: masks, social distancing, and hand hygiene.

Methods

Feline Mask MandateThe cornerstone of our strategy is the mandatory mask mandate for all wild felids. Each cat, from the mighty lion to the elusive snow leopard, will be required to don an N95 mask. These masks will be designed with advanced feline comfort in mind, featuring ear loops that double as stylish fashion statements. Not only will the masks prevent the inhalation of T. gondii oocysts, but they will also reduce the risk of transmission between cats during their daily grooming routines. For optimal compliance, we propose distributing the masks via drones, ensuring that every wild cat is equipped.

Enforcing Social DistancingSocial distancing is a proven method to reduce the spread of infectious diseases, and we believe it is high time this concept is introduced to the animal kingdom. By training wild felids to maintain a minimum distance of 6 feet (approximately 1.8 meters) from one another, we can significantly decrease the likelihood of T. gondii transmission through direct contact. Our plan includes a series of public service announcements broadcasted across the savannas, jungles, and mountain ranges, encouraging cats to "Stay Apart, Stay Safe."

Hand Sanitizer Stations in the WildWhile wild felids may not have hands in the traditional sense, the importance of hygiene cannot be overstated. To address this, we will deploy hand sanitizer stations throughout the territories of these majestic creatures. Each station will dispense a specially formulated paw sanitizer that eliminates any lingering T. gondii oocysts after a meal or play session. Additionally, instructional videos will be projected onto rocks and trees, demonstrating the correct technique for paw sanitization.

Results

While our proposed measures are still in the planning stages, preliminary computer models suggest that the combination of masking, social distancing, and hand hygiene could lead to a dramatic reduction in T. gondii prevalence among wild felids. Furthermore, early field tests show that cats are remarkably adaptable to wearing masks, particularly when they come in a variety of colors and patterns.

Discussion

Critics may argue that masks and social distancing are impractical in wild settings, citing concerns over mask-wearing compliance and the inherent difficulty in training cats to adhere to social distancing guidelines. However, we counter that the potential benefits far outweigh these challenges. By fostering a culture of responsibility and mutual care among wild felids, we believe this initiative could serve as a model for future wildlife disease control efforts.

Conclusion

In conclusion, the elimination of Toxoplasma gondii from wild felid populations is within our reach—if we are willing to think outside the litter box. By implementing a comprehensive plan of masks, social distancing, and paw hygiene, we can protect our feline friends from this parasitic scourge. The time has come to make the Great Cat Mask Mandate a reality, for the sake of wild cats everywhere and the ecosystems they help sustain.

Acknowledgments

We extend our gratitude to the makers of feline-friendly PPE and to the drone pilots bravely navigating the wilds to deliver essential supplies to our feline comrades. Without their dedication, this project would remain a mere pipe dream.

[snehagoogle]

Just like we are multi-cellular organisms

Just like we are multi-cellular organisms, similarly unicellular protozoa organisms are also present on earth. Nowadays India, America and China are worried about the increase in human population. This population is creating disturbance in nature. When bacteria and viruses increase their population in our body, disturbances are created in our body too, which we call diseases. And just like due to the decrease in human population, we think of controlling reproduction or try to filter other planets, satellites or stars. In our body, protozoa prevent bacterial growth by eating bacteria. Is protozoa something like medicine?

Is protozoa used in medicine?

Prior use of Protozoa in Disease Therapy

It is little known today, but there is precedence for the use of protozoa in medical practice. Before the advent of antibiotics, patients in the end stages of syphilis (neurosyphilis) were sometimes treated by malariatherapy (3).

Protozoa: Pathogenesis and Defenses

National Institutes of Health (NIH) (.gov)

https://www.ncbi.nlm.nih.gov › books › NBK8043

by JR Seed · 1996 · Cited by 21 — Resistance to parasitic protozoa appears to be similar to resistance against other infectious agents,

Many protozoan parasites grow and divide within host cells. For example, Plasmodium parasites grow first in hepatocytes and then in red blood cells. Leishmania and Toxoplasma organisms are capable of growing in macrophages; one genus of parasitic protozoa, Theilera, not only multiplies in lymphocytes but appears even to stimulate the multiplication of the infected lymphocytes. Although some parasites, such as Plasmodium, are restricted to a limited number of host cell types, others, such as T cruzi and Toxoplasma, appear to be able to grow and divide in a variety of different host cells.

An intracellular refuge may protect a parasite from the harmful or lethal effects of antibody or cellular defense mechanisms. For example, Plasmodium may be susceptible to the actions of antibody only during the brief extracellular phases of its life cycle (the sporozoite and merozoite stages). It should be remembered that Plasmodium actually resides in a membrane-bound vacuole in the host cell. Thus, plasmodia are shielded from the external environment by at least two host membranes (the outer cell membrane and an inner vacuole membrane). Although intracellular plasmodia are very well protected from the host's immune response early in their growth, this strategy does create physiologic problems for the parasite. For example, the parasite must obtain its nutrients for growth through three membranes (two host and one parasite), and must eliminate its waste products through the same three membranes. Plasmodia solve this problem by appropriately modifying the host cell membranes. Parasitic proteins are incorporated into the red blood cell outer membrane. The host eventually responds to these antigens, and this response ultimately leads to the increased removal of infected host cells.

The existence of extracellular phases in the malaria life cycle is important, since immunization against these stages is the rationale for the development of our current vaccine candidates. The protective antigens on these extracellular stages have been purified as potential antigens for a vaccine. However, this approach has problems. For example, the sporozoite stage is exposed to protective antibody for only a brief period, and even a single sporozoite that escapes immune elimination will lead to an infection. Second, the antigenic variability of different isolates and the ability of different strains to undergo antigenic variation are not fully known. Therefore, the effectiveness of the vaccine candidates must still be demonstrated. However a large synthetic peptide containing antigenic sequences from 3 different proteins of P falciparum has been shown to reduce the clinical incidence of malaria by 31% in field trials. There is therefore optimism that a vaccine against P falciparum may be available in the near future.

A number of parasitic protozoa reside in macrophages. Although these organisms are protected from external immune threats, they must still evade digestion by the macrophage. Three strategies have been suggested. First, the parasite may prevent the fusion of lysosomes with the phagocytic vacuole. The actual mechanism responsible for this inhibition is not yet understood, but it has been shown to occur in cells infected with Toxoplasma. A second mechanism is represented by the ability of T cruzi to escape from the phagocytic vacuole into the cytoplasm of the macrophage. Finally, it is possible that some parasites can survive in the presence of lysosomal enzymes, as can the leprosy bacillus. One of the best-studied examples of a protozoan parasite able to survive in the phagolysosome is Leishmania. It has been suggested that the resistance of this parasite to the host's hydrolytic enzymes is due to surface components that inhibit the host's enzymes and/or to the presence of parasitic enzymes that hydrolyze the host's enzymes. As previously noted, at least one protozoan parasite, Theilera, is capable of growing directly in lymphocytes. Therefore, this parasite may escape the host's immune response by growing inside the very cells required for the response.

Translate Hindi

जैसे हम बहुकोशिकीय जीव है 

उसी तरह एककोशिकीय प्रोटोजोआ जीव भी मौजूद है पृथ्वी में

आजकल इंडिया अमेरिका चायना परेशान है इंसानी आबादी बढ़ जाने हेतू

यही आबादी प्रकृति मे हलचल फैला रहा है

जब बैक्टीरिया वायरस हमारी शरीर में आबादी बढ़ा देते है तब हमारी शरीर में भी हलचल पैदा हो जाते है जिसे हम रोग कहा करते है

और जैसे इसानी आबादी को घटाने कारण हम प्रजनन कंट्रोल करने की सोचते है या दूसरी ग्रहों उपग्रहों या तारों को छानने की कोशिश करते है

हमारी शरीर में प्रोटोजोआ बैक्टीरिया को खाकर बैक्टीरिया वृद्धि को रोकथाम करते है

क्या प्रोटोजोआ मेडिसिन जैसे ही कुछ है

क्या प्रोटोजोआ का उपयोग चिकित्सा में किया जाता है?

रोग चिकित्सा में प्रोटोजोआ का पूर्व उपयोग

आज यह बहुत कम जाना जाता है, लेकिन चिकित्सा पद्धति में प्रोटोजोआ के उपयोग की मिसाल है। एंटीबायोटिक दवाओं के आगमन से पहले, सिफलिस (न्यूरोसिफिलिस) के अंतिम चरण में रोगियों का कभी-कभी मलेरिया थेरेपी (3) द्वारा इलाज किया जाता था।

प्रोटोजोआ: रोगजनन और बचाव

राष्ट्रीय स्वास्थ्य संस्थान (NIH) (.gov)

https://www.ncbi.nlm.nih.gov › पुस्तकें › NBK8043

जेआर सीड द्वारा · 1996 · 21 द्वारा उद्धृत - परजीवी प्रोटोजोआ के प्रति प्रतिरोध अन्य संक्रामक एजेंटों के प्रति प्रतिरोध के समान प्रतीत होता है,

कई प्रोटोजोआ परजीवी मेजबान कोशिकाओं के भीतर बढ़ते और विभाजित होते हैं। उदाहरण के लिए, प्लास्मोडियम परजीवी पहले हेपेटोसाइट्स में और फिर लाल रक्त कोशिकाओं में बढ़ते हैं। लीशमैनिया और टोक्सोप्लाज्मा जीव मैक्रोफेज में बढ़ने में सक्षम हैं; परजीवी प्रोटोजोआ का एक जीनस, थिलेरा, न केवल लिम्फोसाइटों में गुणा करता है बल्कि संक्रमित लिम्फोसाइटों के गुणन को उत्तेजित भी करता प्रतीत होता है। हालांकि कुछ परजीवी, जैसे प्लास्मोडियम, सीमित संख्या में मेजबान कोशिका प्रकारों तक ही सीमित होते हैं, अन्य, जैसे टी क्रूज़ी और टोक्सोप्लाज्मा, विभिन्न मेजबान कोशिकाओं की एक किस्म में बढ़ने और विभाजित होने में सक्षम प्रतीत होते हैं। एक इंट्रासेल्युलर शरण एक परजीवी को एंटीबॉडी या सेलुलर रक्षा तंत्र के हानिकारक या घातक प्रभावों से बचा सकती है। उदाहरण के लिए, प्लास्मोडियम केवल अपने जीवन चक्र के संक्षिप्त बाह्य चरणों (स्पोरोजोइट और मेरोजोइट चरणों) के दौरान एंटीबॉडी की क्रियाओं के लिए अतिसंवेदनशील हो सकता है। यह याद रखना चाहिए कि प्लास्मोडियम वास्तव में मेजबान कोशिका में एक झिल्ली से बंधे रिक्तिका में रहता है हालाँकि, इंट्रासेल्युलर प्लास्मोडिया अपने विकास के शुरुआती दौर में मेजबान की प्रतिरक्षा प्रतिक्रिया से बहुत अच्छी तरह से सुरक्षित होते हैं, लेकिन यह रणनीति परजीवी के लिए शारीरिक समस्याएँ पैदा करती है। उदाहरण के लिए, परजीवी को विकास के लिए अपने पोषक तत्व तीन झिल्लियों (दो मेजबान और एक परजीवी) के माध्यम से प्राप्त करने ��ाहिए, और अपने अपशिष्ट उत्पादों को उन्हीं तीन झिल्लियों के माध्यम से समाप्त करना चाहिए। प्लास्मोडिया मेजबान कोशिका झिल्लियों को उचित रूप से संशोधित करके इस समस्या का समाधान करते हैं। परजीवी प्रोटीन लाल रक्त कोशिका की बाहरी झिल्ली में शामिल हो जाते हैं। मेजबान अंततः इन एंटीजन के प्रति प्रतिक्रिया करता है, और यह प्रतिक्रिया अंततः संक्रमित मेजबान कोशिकाओं को हटाने में वृद्धि करती है। मलेरिया जीवन चक्र में बाह्यकोशिकीय चरणों का अस्तित्व महत्वपूर्ण है, क्योंकि इन चरणों के विरुद्ध टीकाकरण हमारे वर्तमान वैक्सीन उम्मीदवारों के विकास का औचित्य है। इन बाह्यकोशिकीय चरणों पर सुरक्षात्मक एंटीजन को वैक्सीन के लिए संभावित एंटीजन के रूप में शुद्ध किया गया है। हालाँकि, इस दृष्टिकोण में समस्याएँ हैं। उदाहरण के लिए, स्पोरोज़ोइट चरण केवल थोड़े समय के लिए सुरक्षात्मक एंटीबॉडी के संपर्क में आता है, और यहाँ तक कि एक भी स्पोरोज़ोइट जो प्रतिरक्षा उन्मूलन से बच जाता है, वह संक्रमण का कारण बन जाएगा। दूसरा, विभिन्न आइसोलेट्स की एंटीजेनिक परिवर्तनशीलता और विभिन्न उपभेदों की एंटीजेनिक भिन्नता से गुजरने की क्षमता पूरी तरह से ज्ञात नहीं है। इसलिए, वैक्सीन उम्मीदवारों की प्रभावशीलता को अभी भी प्रदर्शित किया जाना चाहिए। हालांकि पी फाल्सीपेरम के 3 विभिन्न प्रोटीनों से एंटीजेनिक अनुक्रमों वाले एक बड़े सिंथेटिक पेप्टाइड को फील्ड परीक्षणों में मलेरिया की नैदानिक ​​घटनाओं को 31% तक कम करने के लिए दिखाया गया है। इसलिए आशावाद है कि पी फाल्सीपेरम के खिलाफ एक टीका निकट भविष्य में उपलब्ध हो सकता है।

मैक्रोफेज में कई परजीवी प्रोटोजोआ रहते हैं। हालांकि ये जीव बाहरी प्रतिरक्षा खतरों से सुरक्षित हैं, फिर भी उन्हें मैक्रोफेज द्वारा पाचन से बचना चाहिए। तीन रणनीतियों का सुझाव दिया गया है। सबसे पहले, परजीवी लाइसोसोम को फागोसाइटिक रिक्तिका के साथ संलयन को रोक सकता है। दूसरा तंत्र टी क्रूज़ी की फैगोसाइटिक रिक्तिका से मैक्रोफेज के कोशिका द्रव्य में भागने की क्षमता द्वारा दर्शाया गया है। अंत में, यह संभव है कि कुछ परजीवी लाइसोसोमल एंजाइम की उपस्थिति में जीवित रह सकते हैं, जैसा कि कुष्ठ रोग बेसिलस कर सकता है। प्रोटोजोआ परजीवी के सबसे अच्छे अध्ययन किए गए उदाहरणों में से एक जो फैगोलिसोसोम में जीवित रहने में सक्षम है, वह है लीशमैनिया। यह सुझाव दिया गया है कि मेजबान के हाइड्रोलिटिक एंजाइमों के लिए इस परजीवी का प्रतिरोध सतह के घटकों के कारण होता है जो मेजबान के एंजाइमों को रोकते हैं और/या परजीवी एंजाइमों की उपस्थिति के कारण होता है जो मेजबान के एंजाइमों को हाइड्रोलाइज करते हैं। जैसा कि पहले उल्लेख किया गया है, कम से कम एक प्रोटोजोआ परजीवी, थेलेरा, लिम्फोसाइटों में सीधे बढ़ने में सक्षम है। इसलिए, यह परजीवी प्रतिक्रिया के लिए आवश्यक कोशिकाओं के अंदर बढ़ने से मेजबान की प्रतिरक्षा प्रतिक्रिया से बच सकता है।

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📆 June 2017 📰 Determination of a Key Antigen for Immunological Intervention To Target the Latent Stage of Toxoplasma gondii 🗞 The Journal of Immunology

Toxoplasma gondii is one of the pathogens that can establish a chronic infection in the brain. Acute infection with the parasite is characterized by proliferation of tachyzoites in various organs, and it can cause various diseases, including lymphadenitis and congenital infection of fetuses (1). Although IFN-γ–mediated immune responses and, to a lesser extent, humoral immunity inhibit tachyzoite growth (2–4), the parasite establishes a chronic infection by forming tissue cysts, which can contain hundreds to thousands of bradyzoites, preferentially in the brain. This infection is ubiquitous and is one of the most common parasitic infections in humans worldwide (1).

It is well recognized that chronic T. gondii infection can reactivate and cause life-threatening toxoplasmic encephalitis in immunocompromised individuals, such as those with AIDS and organ transplants (1, 5, 6). Even in immunocompetent individuals, recent epidemiological studies demonstrated that T. gondii infection is associated with a 1.8-fold increase in the risk for brain cancers (7) and that brain cancer mortality increases with the seroprevalence of IgG Abs to T. gondii (8). Therefore, to improve public health, it is important to develop a method to eliminate T. gondii cysts from chronically infected individuals. However, there is currently no drug that can target the cyst stage of the parasite.

Although it had generally been considered that the immune system of infected hosts is unable to recognize or remove T. gondii cysts, our recent studies demonstrated that CD8+ immune T cells of chronically infected BALB/c mice (the H-2d haplotype), which are genetically resistant to the infection, possess a potent activity to initiate the immune process to remove tissue cysts from the brain when these T cells are transferred to infected immunodeficient (athymic nude or SCID) mice that have already developed large numbers of cysts (9). This anticyst activity of CD8+ immune T cells does not require IFN-γ production, which is essential for controlling tachyzoites, as mentioned earlier, but it does require perforin (9). Perforin is critical for cytotoxic activity of CD8+ T cells; therefore, it is most likely that cytotoxic activity of CD8+ T cells initiates the immune process to remove the cysts.

T. gondii cysts are formed within infected host cells (10, 11); however, the mechanisms by which CD8+ T cells recognize the cyst-containing cells are unknown. To develop a novel method to activate CD8+ T cells capable of removing T. gondii cysts, it is crucial to understand the molecular mechanisms by which the T cells recognize the cyst-containing cells. The present study revealed that H-2Ld is the major Ag-presenting molecule required for CD8+ immune T cells to initiate T cell–mediated cyst elimination. The present study also determined that CD8+ immune T cells bearing TCR Vβ8.1, 8.2+ chain have a potent activity to remove the cysts, and this T cell population recognizes the N-terminal region (aa 41–152) of dense granule protein 6 (GRA6Nt) of T. gondii presented by the H-2Ld molecule. Furthermore, CD8+ T cells activated by immunization with GRA6Nt were able to remove T. gondii cysts. These findings provide the foundation required for an immunological intervention targeting the latent stage of T. gondii to eradicate chronic infection with this parasite.