Year : 1980 | Volume
: 28 | Issue : 3 | Page : 127--129
Experimental iridocyclitis with herpes simplex virus type- I
VD Purohit, LP Agarwal, VM Mahajan, Ramesh Kumar
Department of Microbiology, A.I.I.M.S. and Dr. Rajendra Prasad Centre for Ophthalmic Sciences, New Delhi, India
V M Mahajan
Dr. Rajendra Prasad Centre for Ophthalmic Sciences, A.I.I.M.S New Delhi-29
|How to cite this article:|
Purohit V D, Agarwal L P, Mahajan V M, Kumar R. Experimental iridocyclitis with herpes simplex virus type- I.Indian J Ophthalmol 1980;28:127-129
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Purohit V D, Agarwal L P, Mahajan V M, Kumar R. Experimental iridocyclitis with herpes simplex virus type- I. Indian J Ophthalmol [serial online] 1980 [cited 2020 Nov 25 ];28:127-129
Available from: https://www.ijo.in/text.asp?1980/28/3/127/28241
Clinical and experimental herpetic keratitis has been well studied from its numerous angles,. Herpetic iridocyclitis is also emerging as an independent and secondary clinical entity. This experimental study has been undertaken with a view to understand if some of the routine diagnostic appliances could be of some avail in clinching the diagnosis of herpetic uveitis.
MATERIALS AND METHODS
Ten healthy albino rabbits, each weighing 1.5 to 2.5 kg and of either sex were chosen for the study. Virus isolated from a case of keratitis and serotyped as Herpes simplex virus (HSV) Type 1, was injected into their anterior chamber. Inoculum for each rabbit was 0.05 ml containing 10, TCID 50/ml. Control e) e was similarly inoculated with Eagle's minimal essential medium in the same dosage. Both, the test as well as the control eyes were examined every other day till the 35th day. The lesions were graded following the system of Smolin and Okumoto.
Corneal scrapings and aqueous from test and control eyes were examined, at 48 hrs, 72 hrs and on the 10th post-inoculation days for cytological changes and viral re-isolation respectively. A loopful of aqueous was tested for bacterial culture also. Corneal scrapings were stained with Giemsa stain. For isolation of virus, Vero cells were used. Two passages were given. Infected cover-slips were stained with haematoxylin and eosin stain.
Blood was tested for HSV antibodies on 0, 8th and 22nd post-inoculation days. Microtitre complement fixation test was used following the procedure of Lennette and Schmidt. Antigen was prepared from one of the local isolates of HSV-I following the method of Palmer et a1[ 6] . At the end of 35 days of follow up period, infected eyes were enucleated and eye balls studied for histopathological changes after staining with haematoxylin and eosin stains.
By the 4th day, 6 out of 10 eyes showed mild to moderate oedema and congestion which regressed by the 18th day. No change was seen in the remaining four.
By the 12th day, all the test eyes showed aqueous flare. Only 6 eyes developed low degree of hypopyon which persisted till the end. Two out of these had haemorrhagic hypopyon. Keratic precipitates, which started appearing from 6th day, disappeared by the 35th day. Iris was muddy and lost its pattern in 5 eyes by the 10th day and remained so till the end.
Pupil remained constricted in all the eyes throughout. Synechiae developed on the 8th day in 6 eyes but were subsequently seen in all till the end.
Of the control eyes, two showed mild iridocyclitis changes after 8th day which regressed gradually by the 20th day. Laboratory investigations are summarized in [Table 1]. None of the aqueous specimens yielded a bacterial culture. First aqueous tap from all eyes was negative for the virus. In second aqueous tap, only one eye showed the presence of virus which was detected in the first passage. The remaining were negative. This isolate developed intra-nuclear inclusions in Vero cells.
Corneal scrapings never showed any evidence of intra-nuclear inclusions. However, 1 out of 10 in the first specimen and 2 out of 10 in the 2nd specimen, showed the presence of mononuclear and giant cells. Sera showed 2-4 fold rise in their antibody titres against HSV [Table 1].
Out of the 6 eye balls subjected to histopathological examination, 5 showed iridocyclitic changes. Anterior chamber was full of inflammatory exudates. Two eyes showed severe haemorrhages and keratic precipitates. These were having endophthalmitis. Corneal stroma was oedematosus and infiltrated with inflammatory cells.
Independent uveal involvement in ocular herpes is a known clinical entity,,. However, the interesting feature of this experimental study has been the development of iridocyclitis after inoculating HSV in the anterior chamber of rabbits. The results of re-isolation of virus from the aqueous were rather disappointing. This could have been due to two reasons. Firstly, perhaps the aqueous does not contain adequate number of live cells required for viral replication and thus the released virus does not remain viable. This view has also been advocated by Martenet who has been able to isolate the virus from one eye out of nine with experimentally produced anterior uveitis in rabbits. Earlier, Kimura also failed to culture the virus from aqueous of thirty eyes of rabbits with fully developed anterior uveitis. Second possibility could be that as soon as the virus is inoculated into the anterior chamber, it gets adsorbed to the cells of different tissues like iris and ciliary muses and starts replication after penetration. The presence of virus in these tissues has been demonstrated by several workers. Maloney and Kaufman cultured the virus from ciliary body and iris of HSV infected eyes. Subsequently after being released, the virus reinfects other structures and perhaps no or minimal amount is left behind in the aqueous humour. Poor positivity by cytology study is understandable because the disease did not even clinically manifest on the corneal surface. However, presence of giant cells and mononuclear cells preceding the development of self limiting corneal ulcers on the periphery are suggestive that these ulcers might be due to HSV-I. It can be concluded that in laboratory diagnosis, isolation of the virus and corneal scrapings are of little value in cases of iridocyclitis. Two fellow eyes (control eyes) also showed mild iridocyclitic changes which started eight days after inoculation. The lesions regressed by the twentieth day and the eyes became clear. This type of involvement in the control eyes, has been observed previously also. Attempts to demonstrate virus in the fellow eyes, by any test were not made.
The paired sera of these animals showed a 2 to 4 fold rise in complement fixing (CF) antibody titres, irrespective of low isolation rate and negative cytology. This increase in CF antibody confirms the primary ocular infection due to HSV-I. Martenet had also suggested serology as the only valuable aid. Histopathological study of the enucleated eyes by the end of follow up period, all revealed iridocyclitic changes. However, three eyes showed active iridocyclitic changes. The anterior chamber of these eyes was full of inflammatory cells and keratic precipitates. Two out of them showed haemorrhages in anterior chamber where they developed haemorrhagic hypopyon. Schlaegel also observed haemorrhagic hypopyon occasionally in viral uveitis, especially in clinical herpetic uveitis. This experiment confirms the clinical findings.
Herpetic iridocyclitis similar to that seen in man was produced, after inoculation of Herpes simplex virus Type I into the anterior chamber of rabbits. Development of lesions was studied. Serum antibody levels and also the virus re-isolation were determined at different intervals.
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