Multiplication of Certain Neurotropic Viruses in the Rabbit Eye following Intraocular Inoculation

Lymphocytic choriomeningitis virus and Semliki Forest virus readily multiply in the rabbit eye following inoculation into the vitreous. Less than 10 mouse LD(50) of LCM virus was sufficient to induce multiplication in the eye, whereas, approximately 1000 LD(50) of SFV was required to initiate infection. Both viruses multiplied in the rabbit eye as an inapparent infection. Little or no virus could be recovered from the optic nerves or brains of the rabbits, although virus was present in high titer in the eyes. The animals showed no signs of illness other than a transitory fever. Large amounts of SFV induced a severe iritis followed by corneal opacity. This reaction appeared to be due to "toxic" properties of the virus. No ocular reactions have been observed with LCM virus other than a mild transitory hyperemia. The yield of virus from the eye following inoculation of large amounts of SFV was less than when more dilute inocula were used. Maximum multiplication of both viruses occurred about 48 hours after inoculation into the vitreous. SFV remained in high titer for about 4 days and thereafter could be recovered in variable amounts up to about 5 weeks after inoculation. LCM virus could be recovered in gradually decreasing amounts up to about 3 weeks after inoculation. Serum-neutralizing antibodies appeared in high titer (neutralization index up to 3000) following inoculation of SFV into the rabbit eye. However, only traces of antibody could be detected in extracts of the eyes. SFV was obtained irregularly and in low titer from the aqueous humor following inoculation into either the vitreous or anterior chamber. No significant difference in the virus content of the vitreous, an extract of the retinal cells, and an extract of the whole eye could be detected 48 hours after inoculation of SFV into the vitreous. The Lansing strain of poliomyelitis virus failed to cause any detectable reaction in the rabbit eye and no evidence of multiplication of the virus was obtained in these experiments.